,transcrib]'s ,note3 ,punctuation has be5 /&>dis$1 & possible typographical errors h be5 *ang$4 ,ar*aic1 v>iable & inconsi/5t spell+ & hyph5ation h be5 pres]v$4 ,bold text is surr\nd$ by equal signs & italic text is surr\nd$ by und]scores4 ,footnotes appe> at ! end ( _! respective *apt]s4 ,,survey+ ,,& ,,levell+ ,,in/rum5ts ,,survey+ ,,& ,,levell+ ,,in/rum5ts ,!oretically & ,practically ,describ$4 ,,= ,,con/ruction1 ,,qualities1 ,,selection1 ,,pres]vation1 ,,adju/m5ts1 ,,& ,,uses2 ,,) ,,o!r ,,app>atus ,,& ,,appliances ,,us$ ,,by ,,civil ,,eng9e]s ,,& ,,surveyors ,,9 ,,! ,,field4 ,,by ,,william ,,=d ,,/anley ,,optician1 ,,manufactur] ,,( ,,survey+ ,,& ,,draw+ ,,in/rum5ts1 ,,au?or ,,( ,a ,,treatise ,,on ,,draw+ ,,in/rum5ts1 ,,prop]ties ,,& ,,motions ,,( ,,fluids1 ,,nebul> ,,!ory1 ,,etc4 ,,f\r? ,,edition ,,revis$ ,,by ,h4 ,t4 ,,tallack4 ,,london3 ,e4 ,f4 ,n4 ,,spon1 ,,ltd41 #eg1 ,,haym>ket1 ,s4,w4 ,,new ,,york3 #abc1 ,,lib]ty ,,/reet ,,& ,,( ,w4 ,f4 ,,/anley ,,co41 ,,limit$ #bhf1 ,,high ,,holborn1 ,,london1 ,w4,c4 #aiad ,,preface ,,to ,,fir/ ,,edition4 ,notes 7 tak5 = _m ye>s be=e ! production ( ?is "w ( qu]ies t came be=e ! au?or = reply relative to functional p>ts ( survey+ in/rum5ts4 ,^! bore mo/ frequ5tly ref]5ce to optical & magnetic subjects1 & to ! qualities & action ( _s level tubes1 also occasionally to graduation & ! qualities ( clamp & tang5t motions4 ,x 0 !re=e ?\ght t x w\ld be useful to give notes ^u ^! subjects 9 detail z f> z possible 9 ! e>ly *apt]s4 ,z ! "w proce$$ x 0 f\nd t ?is plan sav$ mu* space 9 avoid+ ! necessity = sep>ate descriptions :5 p>ts ( complex in/rum5ts 7 aft]w>ds describ$4 ,to %[ ! /ate ( ! art & r5d] ! "w useful1 x 0 necess>y t ! /ructure ( survey+ in/rum5ts %\ld be giv5 ) suffici5t detail to be work$ out by ! skilful manufactur]4 ,beyond ?is x 0 ?\ght to be mo/ important t ! pr(essional man1 :o mu/ h limit$ exp]i5ce ( ! qualities ( workman%ip1 %\ld be suppli$ ) z _m simple te/s z possible = assur+ ! qualities ( ! in/rum5ts he might pur*ase or use1 ) details also ( _! adju/m5ts4 ,?is matt] is !re=e c>ri$ into detail = "o in/rum5t at lea/ ( ea* class1 z v little g5]al in=mation is to be f\nd on ! subject 9 our lit]ature4 ,9 fact1 l>ge gr\ps ( in/rum5ts 9 ext5sive use1 su* z ^? us$ = m9+ survey+1 & subt5se measur+ in/rum5ts1 h rema9$ h]et(ore ne>ly undescrib$ 9 our language4 ,! te*nical pr9ciples foll[$ 9 work+ out details 9 ^! pages are giv5 by illu/rations ( su* p>ts ( important in/rum5ts z pres5t any difficulty ( obs]vation f an ext]ior view ( ! engrav+ ( ! entire in/rum5t4 ,! plans ( con/ruction 9 g5]al use are select$ = illu/ration4 ,c]ta9 con/ructions t are liable to failure are po9t$ out4 ,_m rec5t improvem5ts 9 in/rum5ts are recognis$ & "s are sugge/$1 b no attempt has be5 made to record ! little diff]5ces ( con/ruction1 (t5 m]itori\s1 :i* give only a c]ta9 am\nt ( /yle to ! "w ( ea* c\ntry & ( ea* individual4 ,^u ?is po9t x mu/ occur t ! "w done 9 any work%op mu/ v>y f o!r "w accord+ to ! skill & judgm5t ( ! ma/]4 ,x is int5d$1 !re=e1 t di/9ctly typical in/rum5ts only %\ld be describ$1 9 a mann] t details may be work$ out !refrom4 ,to make ?is matt] z cle> z possible1 ) few exceptions ^! pages 7 writt5 ) ! in/rum5ts describ$ ^u my table1 & ! illu/rations1 :5 n tak5 directly f ! in/rum5ts1 7 tak5 f work%op draw+s to a r$uc$ scale4 ,9 practice x is f\nd t in/rum5ts p]=m+ simil> functions may be v mu* v>i$ 9 con/ruction1 be>+ ref]5ce frequ5tly to ! conditions "u :i* !y are to be us$4 ,! same may be said ( ! functional p>ts ( in/rum5ts4 ,we may also obs]ve t ,engli% in/rum5ts diff] 9 detail f =eign ones1 & ^u ?is po9t !re is no d\bt mu* may be le>n$ by comp>ison ( "s details ( ,engli% ) =eign "w1 al?\gh our own is admitt$ to rank high4 ,comp>isons are !re=e freely made 9 ! foll[+ pages1 & sugge/ions (f]$ aft] /udy abroad ( =eign "w1 & c>eful inspection ( ne>ly ! :ole lit]ature ^u ! subject1 9 :i* x is v obs]vable t "s mod]n cont95tal books1 treat+ ^u p>ts ( ! subject1 are mu* 9 advance ( our own4 ,! survey+ in/rum5ts describ$ 9 ^! pages are ne>ly limit$ to ^? us$ 9 ! field4 ,in/rum5ts = plan draw+ & calculation ( areas1 :i* ! surveyor uses 9 ! (fice1 h be5 describ$ 9 ! au?or's "w on ,draw+ ,in/rum5ts 7n[ 9 ,sev5? ,edition71 to :i* ?is is int5d$ to be ! complem5t ( ! subject4 ,to r5d] ! "w z complete z possible1 x 0 ?\ght necess>y to give briefly ! mann] ( us+ _m in/rum5ts 9 practical survey+4 ,?is "p ( ! subject1 f ! au?or's v limit$ exp]i5ce 9 ! field1 is l>gely tak5 f inspection ( ! be/ works on survey+4 ,! au?or1 h[ev]1 is v pleas$ to ackn[l$ge ! k9dness ( _m pr(essional fri5ds = assi/ance on ?is & _m o!r po9ts1 & = hi/orical notes4 ,= ! description ( ! #cf-;in* !odolite1 giv5 9 ,*apt] ,,vii4 7n[ ,x471 ! au?or is indebt$ to ! late ,col4 ,a4 ,/range1 ,f4,r4,s41 :o gave e detail ( 8 design & discuss$ _m po9ts4 ,! au?or is also indebt$ to ,mr4 ,?omas ,cu%+1 ,f4,r4,a4,s41 ,inspector ( ,sci5tific ,in/rum5ts = ,india1 :o has giv5 in=mation & 8 op9ions ^u _m subjects f 8 l>ge practical exp]i5ce4 ,also to ,pr(4 ,george ,full]1 ,c4,e41 :o has k9dly read pro(s1 exam9$ =mul1 & made "s te*nical po9ts cle>]4 ,also to ,mr4 ,w4 ,n4 ,bakewell1 ,m4,in/4,c4,e42 ,major-,g5]al ,a4 ,de ,lisle1 ,r4,e42 ,"r ,hon4 ,"l ,rayleigh1 ,f4,r4,s41 = assi/ance on sev]al te*nical po9ts4 ,9 ?is ,fir/ ,edition1 entirely f manuscript1 !re w no d\bt be errors & omissions2 !re=e ! au?or w feel oblig$ by ! receipt ( any notes t he may make use ( = future corrections1 %\ld ano!r ,edition be dem&$4 ,w4 ,f4 ,s4 ,,great ,,turn/ile1 #ahij4 ,,preface ,,to ,,?ird ,,edition4 ,! note at ! end ( ! ,fir/ ,edition ( ?is "w ref]r$ to on ! prec$+ page has br\ght ! au?or _m lett]s f pr(essional m51 :o h k9dly tak5 int]e/ 9 ! "w by (f]+ sugge/ions :i* are n[ incorporat$ z f> z practical 9 ?is ,edition1 & = :i* ?anks are t5d]$4 ,"o important improvem5t ( late ye>s 9 ! con/ruction ( survey+ in/rum5ts is due to ! great] p]fection ( mod]n ma*9]y1 & ! adoption ( special ma*9es to %ape out _m p>ts ( ! "w f ! solid :i* 7 =m]ly screw$ toge!r 9 _m pieces1 :i* made ! in/rum5ts heavi] & also liable to become loose 9 p>ts by j>s1 s z to cause ! necessity ( frequ5t readju/m5ts4 ,ano!r important improvem5t 9 mod]n survey+ in/rum5ts is 9 _! lightness1 due to ! discov]y ( p]man5t alum9ium alloys1 by :i* _m p>ts ( in/rum5ts t are %ap$ out 9 ! solid may be r$uc$ to "o-?ird ! weight ( ! gun-metal ca/+s =m]ly us$ entirely = ^! p>ts4 ,9 ! pres5t ,edition1 :i* repres5ts =ty-sev5 ye>s ( exp]i5ce ( ! au?or's life devot$ to ! details ( ! subject1 x is hop$ t "s p]man5t improvem5ts 9 survey+ in/rum5ts may be %[n1 & t _m new designs n[ fir/ describ$1 f\nd$ ^u ?is exp]i5ce1 may m]it trial4 ,! au?or is pleas$ to ackn[l$ge ! zeal\s aid 8 work+ manag] & at pres5t co-director1 ,mr4 ,h4 ,t4 ,tallack1 has giv5 9 p]fect+ ?is "w to br+ x to its pres5t /ate4 ,w4 ,f4 ,s4 ,,great ,,turn/ile1 #aija4 ,,preface ,,to ,,f\r? ,,edition4 ,s9ce ! publication ( ! ,?ird ,edition ( ?is "w1 ! au?or has be5 tak5 f u1 & x has fall5 to my lot to revise x & br+ x up to ! pres5t "t4 ,?is "w ,i h approa*$ ) ! greate/ diffid5ce1 hav+ to foll[ "o :o _h su* pr(\nd k ( ! subject1 & ,i h e>ne/ly endeav\r$1 z closely z possible1 to act z ,i ?9k he w\ld h done _h he be5 alive1 & hav+ enjoy$ ov] tw5ty ye>s ( ! happie/ & close/ bus9ess relations ) him--actively co-op]at+ 9 br++ _m ( ! in/rum5ts to _! pres5t /ate1 ,i v5ture to hope t ,i h to "s ext5t c>ri$ out :at 8 wi%es w\ld h be54 ,i h c>efully read ov] & correct$ ! :ole "w1 & ! additions to x are only 9 ! nature ( br++ x up to date4 ,h4 ,t4 ,,tallack4 #bhf1 ,,high ,,holborn1 ,june1 #aiad4 ,,cont5ts4 ,,*apt] ,i4 ,,page ,,introduction3--,hi/orical ,sket*--,classification ( ! ,subject-- ,purposes & ,qualities ( ,in/rum5ts--,workman%ip--,metals-- ,alum9ium--,fram+--,tools--,axes ( ,in/rum5ts--,sold]+-- ,f9i%+--,bronz+--,lacqu]+--,graduat+--,e ngrav+--,/yle-- ,glass-,"w--,woodwork--,lubrication--,pr es]vation ( ,in/rum5ts-- ,pack+ #a ,,*apt] ,,ii4 ,,! ,,telescope ,,z ,a ,,"p ,,( ,a ,,survey+ ,,in/rum5t3--,g5]al ,description--,qualities--,optical ,pr9ciples--,refraction ( ,glass--,limit ( ,refraction--,reflection--,prisms--,l5se s1 ,convex & ,concave--,ab]ration--,=mation ( ,images--,disp]sion-- ,a*romatism--,curvature ( ,l5ses--,telescopes--,eye-pieces--,p[]s- - ,dynamet]--,con/ruction ( ! ,telescope--,diaphragm--,webs--,l9es-- ,po9ts--,p>allax--,exam9ation & ,adju/m5t #bd ,,*apt] ,,iii4 ,,! ,,magnetic ,,compass ,,z ,a ,,"p ,,( ,a ,,survey+ ,,in/rum5t ,,or ,,sep>ately3--,broad & ,edge-b> ,ne$les--,manufacture ( ! ,ne$le--,magnetisation--,susp5sion--,dip & ,adju/m5t--,lift+-- ,incl9ation--,decl9ation--,v>iation--,co rrection--,compass-,boxes-- ,description ( ,compasses--,r+ ,compasses--,tr\gh ,compasses-- ,prismatic ,compasses--,/&--,survey+ ) ,compass--,pocket ,compasses #ei ,,*apt] ,,iv4 ,,levels3--,me?ods ( ,asc]ta9+--,level ,tubes--,manufacture-- ,curvature--,s5sitiv5ess--,te/+--,read+- -,circul> ,levels-- ,surveyors' ,levels--,y-,levels--,p>allel ,plates--,adju/m5ts ( ,y-,levels--,sugge/$ ,improvem5ts--,dumpy ,levels--,tripod ,/&s-- ,adju/m5t ( ,dumpy--,collimator--,improvem5ts 9 ,dumpy ,levels-- ,tribra* ,head--,diaphragms--,cu%+'s ,levels--,cooke's ,levels--,*eap ,=ms ( ,level--,h& ,levels--,reflect+ ,levels--,wat] ,levels #he ,,*apt] ,v4 ,,levell+ ,,/aves3--,con/ruction--,v>i\s ,read+s ,discuss$-- ,sop)'s--,field's--,/range's--,/anley's ,new ,metrical--,simple ,con/ruction--,m9+ ,/aff--,pap]+ ,levell+ ,/aves-- ,pres]vation--,pack+ ,pads--,/aff ,plate--,/aff ,level--,practice ( ,levell+--,index ( ,bubble--,lamp--,curvature ,corrections--,/ation ,pegs--,ref9em5t ( ,levell+--,levell+ ,books #adh ,,*apt] ,,vi4 ,,division ,,( ,,! ,,circle ,,& ,,me?ods ,,employ$ ,,9 ,,tak+ ,,angles3-- ,divid+ ,eng9e--,surfaces = ,graduation--,v]ni]--,v>i\s ,sections--,read+ ,microscopes--,%ades--,micromet]s--,clam p & ,tang5t ,motions--( ,limbs--( ,axes--,use & ,we>--,diff]5ce ( ,hypot5use & ,base #age ,,*apt] ,,vii4 ,,!odolites3--,con/ructive ,details ( #e-;in* & #f-;in* ,transits-- ,special ,additional ,p>ts--,old ,=m ) ,f\r ,screws--,improv$ ,=m--,additional ,p>ts--,plummets--,/rid+ ,level--,lamp-- ,adju/m5ts ov] a ,po9t--,sol> ,atta*m5t--,photographic ,atta*m5t #bad ,,*apt] ,,viii4 ,,specialties ,,9 ,,mod]n ,,=ms ,,( ,,transit3--,!odolites = ,g5]al ,survey+--,railway ,"w--,explor+ #bdf ,,*apt] ,,ix4 ,,pla9 ,,!odolites ,,9 ,,:i* ,,! ,,transit ,,pr9ciple ,,is ,,n ,,employ$3--,! ,pla9 ,!odolite--,improv$ ,con/ruction--,ev]e/'s ,simple--,adju/m5ts & ,exam9ation ( ,!odolites #bfg ,,*apt] ,x4 ,,l>ge ,,!odolites ,,us$ ,,only ,,= ,,geodetic ,,surveys3--,/anley's #aj- & #ab-;in*--#ad-;in* ,altazimu?--,col4 ,/range's #cf-;in* ,!odolite #bic ,,*apt] ,,xi4 ,,m9+ ,,survey ,,in/rum5ts3--,circumf]5tors--,pla9 ,m9]'s ,dial-- ,sights--,tripod ,/&--,adju/m5ts--,h5d]son's ,dial--,lean's ,dial--,adju/m5ts--,h$ley's ,dials--,additional ,telescope--,improv$ ,h$ley--,tribra* & ,ball ,adju/m5t--,reflectors--,cont95tal ,=ms--,?odolite ,s\t]ra9--,tripod ,tables--,/anley's ,m9+ ,!odolite--,pa/orelli's & ,h(fmann's ,adju/able ,tripod ,heads-- ,m9+ ,transit ,!odolites--,/anley's ,prismatic ,m9+ ,compass-- ,hang+ ,dial--,hang+ ,cl9omet]--,semi-circumf]5tor--,m9+ ,lamps #cjg ,,*apt] ,,xii4 ,,in/rum5ts ,,to ,,measure ,,subt5se ,,or ,,tang5tial ,,angles ,,to ,,asc]ta9 ,,di/ances3--,hi/orical ,notes ( ! ,me?od--,pr9ciples ,involv$-- ,/adia ,measurem5ts1 ,direct & by ! ,ord9>y ,telescope-- ,corrections = ,refraction ( ! ,object ,glass--,/anley's ,subt5se ,diaphragm--,anallatic ,telescope ( ,porro--,ta*eomet]s--,/adia-- ,omnimet]--,field book--,bakewell's ,subt5se ,arrangem5t #cee ,,*apt] ,,xiii4 ,,in/rum5ts ,,con/ruct$ ,,especially ,,= ,,facility ,,( ,,tak+ ,,incl9ations3--,incl9omet] ,!odolite--,gradiomet]--,cl9omet]s3 ,abney's--,tr\ghton's--,de ,lisle's--,/anley's--,b>k]'s--,burni]'s- - ,watk9's--,cl9omet] ,sights--,rule ,cl9omet]--,road ,trac] #chi ,,*apt] ,,xiv4 ,,in/rum5ts ,,( ,,reflection3--,octant or ,quadrant--,reflect+ ,circle--,sextant--,pr9ciple--,p>allax-- ,con/ruction--,exam9ation-- ,adju/m5t--,artificial ,horizon--,s\nd+ ,sextant--,box-,sextant-- ,supplem5t>y ,arc--,improvem5ts ^u ?is--,optical ,squ>e--,optical ,cross--,apomecomet] #dbb ,,*apt] ,,xv4 ,,graphic ,,survey+ ,,in/rum5ts ,,& ,,appliances ,,connect$ ,,!re)3--,plane ,tables--,alidades--,telescopic ,arrangem5ts-- ,subt5se ,measurem5ts--,v>i\s ,devices = ,hold+ ! ,pap]-- ,cont9u\s ,pap]s--,adju/m5t ( ,tripod ,heads--,me?od ( ,us+--,edgewor?'s ,/adiomet]--,sket*+ ,protractor--,sket*+ ,case--,cam]a ,lucida1 etc4 #dgb ,,*apt] ,,xvi4 ,,in/rum5ts ,,= ,,measur+ ,,l& ,,& ,,civil ,,works ,,directly3--,*a9s-- ,v>i\s ,tell]s--,/&>d ,*a9s--,arr[s--,drop ,arr[s--,vice = ,adju/+ ,*a9--,ca9k's ,rule = ,incl9es--,/eel ,b&s--,wire ,l& ,measures--,l95 ,tapes--,(fset ,rods--,p9e ,/&>d ,rods--,rods ) ,iron ,core--,beam ,compass ,rods--,co9cid5ce ,measurem5ts-- ,comp5sat$ ,rods--,base ,l9e ,app>atus--,coa/ ,survey ,l9es-- ,p]ambulator--,p$omet]--,passomet]--,s\n d+ ,*a9s--,s\nd+ ,l9es--,telemet]s--,h& ,rods--,rules #dij ,,*apt] ,,xvii4 ,,/ations ,,( ,,obs]vation3--,pickets--,false ,picket--,p]man5t ,/ations--,ref]r+ ,object--,heliotrope--,helio/at--,heliog raph ,signall+--,morse ,alphabet--,night ,lights--,oil ,lant]ns--,magnesium ,light #ecc ,,*apt] ,,xviii4 ,,measurem5t ,,( ,,altitudes ,,by ,,diff]5ces ,,( ,,atmosph]ic ,,pressure3-- ,hi/orical ,note--,m]curial ,b>omet]--,con/ruction--,op]ation-- ,an]oid ,b>omet]--,con/ruction--,v>i\s ,improvem5ts--,hypsomet] #edh ,,*apt] ,,xix4 ,,miscellane\s ,,surveyors' ,,& ,,eng9e]s' ,,in/rum5ts1 ,,appliances1 ,,& ,,accessories3--,cross ,/aff--,me*anics' ,levels--,bon+ ,rods-- ,footn]'s ,railway ,gauge--,gir? ,/rap = ,timb] ,measurem5t--,gir? ,tapes--,timb] ,m>k]--,sla%+ ,knife--,bill-,hook--,reconnoitr+ ,glass--,telescope--,sun ,spectacles--,:i/les--,pione] ,tools--,sket* ,block ,book--,cam]a--,geological ,tools--,wealemefna--,opisomet]-- ,b\*]'s ,calculator--,slide ,rules--,full]'s ,calculator--,eng9e]s' ,pocket-,books--,*ronomet]--,outfits #egc ,,index #fja ,,survey+ ,,in/rum5ts4 ,,*apt] ,i4 ,,hi/orical ,,sket*--,,classification ,,( ,,! ,,subject--,,purposes ,,& ,,qualities ,,( ,,in/rum5ts--,,workman%ip--,,metals--,,a lum9ium--,,fram+-- ,,tools--,,axes ,,( ,,in/rum5ts--,,sold]+--,,f9i%+--,,bronz+ -- ,,lacqu]+--,,graduat+--,,engrav+--,,/yle --,,glass-,,"w--,,woodwork-- ,,lubrication--,,pres]vation ,,( ,,in/rum5ts--,,pack+4 #a4--;,hi/orical ,sket*4--,al?\gh ! aim ( ?is "w is to %[ ! /ate ( ! art x is int5d$ to repres5t at ! pres5t p]iod1 a l>ge am\nt ( lit]ature1 anci5t & mod]n1 has be5 consult$ = its production1 pr9cipally ) ! object t ! au?or%ip1 z f> z possible1 %\ld be giv5 ( ! in/rum5ts describ$ :i* h come into g5]al use4 ,_m ( ^! in/rum5ts h be5 br\ght to _! pres5t /ate ( p]fection by small consecutive improvem5ts ^u old] =ms4 ,!re=e1 x is hop$1 a brief hi/orical sket* ( ! lit]ature ( ! subject may be ?\ght to =m a fit introduction4 #b4--,l& survey+ 0 possibly fir/ practis$ 9 ,egypt1 :]e l&m>ks 7 liable to be wa%$ away or displac$ by ! ov]fl[ ( ! ,nile4 ,t x 0 also us$ o!rwise is %[n 9 t !re is extant 9 ,tur9 a papyrus giv+ ! plan ( a gold m9e ( ab\t #adjj ,b4,c4 ,! e>lie/ survey+ in/rum5t ( :i* we h record is ! diopt] ( ,h]o ( ,alex&ria1 ab\t #acj ,b4,c4 ,?is in/rum5t appe>s to h be5 a wood5 cross1 ) sights to take "r angles4 ,9 ! a/rolabe ( ,hipp>*us1 we h a divid$ quadrant ( a circle sight$ f ! c5tre4 ,9 ,ty*o ,brah's ,a/ronomica ,in/aurata ,me*anica1 #aeih1 we h descriptions & engrav+s ( ! a/rolabe ( ,hipp>*us1 ,ptolemy1 ,alhaz51 & ( 8 own in/rum5ts4 ,^! all embrace ! pr9ciple ( ! quadrant1 b ! sight+ ( ! /> or object ) ! in/rum5t by movable p>ts is effect$ 9 v>i\s ways4 ,^! in/rum5ts 7 made at fir/ only = a/ronomical obs]vations2 b !y appe> to h be5 appli$1 at a v e>ly date1 ) slight modifications1 to topographical survey+4 #c4--;,9 ,?omas ,digges' ,pantometrie1 #aega1 we h sev]al in/rum5ts describ$ = survey+ purposes3--,! geometrical quadrant is an arc ( #ij1 ) sights to ! #ij radius1 & a plummet f ! radiant angle to read degrees ( elevation4 ,! geometrical squ>e1 sight$ ^u "o edge1 ) an alidade c5tr$ f ! corn] f :i* ! #ij radiate to take horizontal angles4 ,9 ano!r in/rum5t ! two in/rum5ts describ$ above are comb9$4 ,! !odolitus--! orig9 ( ! !odolite1 a ^w probably d]iv$ f !odica1 tak5 9 ! s5se ( p]fection1 z be+ ! mo/ p]fect in/rum5t4 ,x consi/s ( a complete circle divid$ & figur$ to #cfj1 m\nt$ ^u a /&1 ) a sight$ alidade mov+ ^u its c5tre & read+ across ! circle into opposite divisions4 ,an artificial horizon is also describ$ = asc]ta9+ altitudes by reflection4 #d4--;,9 #afbd1 ,edmund ,gunt]1 to :om sci5ce is indebt$ = ! inv5tion ( ! slide rule1 sector1 & *a9 ( #ajj l9ks1 publi%$ a "w giv+ descriptions ( ! cross-/aff1 8 improv$ =m ( quadrant1 ) improvem5ts on "s o!r in/rum5ts4 ,9 #afhf we h ! fir/ treatise on m9e survey+1 ! ,geometria ,subt]ranea ( ,nicolaus ,voigtel1 publi%$ 9 ,leipzig1 9 :i* we h ! hang+ compass1 /ill mu* 9 use on ! ,cont95t1 describ$4 ,beyond ?is1 few improvem5ts are record$ ^u survey+ in/rum5ts 9 ! sev5te5? c5tury4 #e4--,ne> ! comm5cem5t ( ! eighte5? c5tury we h a some:at important "w1 publi%$ 9 ,p>is1 writt5 by ,nicolaus ,bion1 ,con/ructions des ,in/rum5ts de ,ma!matique1 #agah4 ,?is treatise 0 translat$ into ,engli% by ,edm4 ,/one1 :o made _m additions to x 9 #agbc4 ,x =m$ an important "w 9 its day1 & is excell5tly illu/rat$4 ,9 ?is we f9d an acc\nt ( ! circumf]5t]s1 plane tables1 magnetic compasses1 & o!r in/rum5ts !n 9 use4 ,! next important "w treat+ ^u ! subject is ,g>d9]'s ,practical ,surveyor1 #agcg4 ,9 ?is we h ! !odolite mu* improv$ & br\ght to ne>ly its pres5t =m by ,jona?an ,sisson1 b x 0 n1 h[ev]1 p]fect$ until ! introduction ( ! a*romatic telescope by ,john ,dollond1 ab\t #agfj4 ,g>d9] gives also a c>eful consid]ation ( ! be/ in/rum5ts employ$ g5]ally 9 ! practice ( survey+4 ,no?+ f ?is "t appe>s except transcriptions & incid5tal descriptions ( in/rum5ts 9 works on survey+1 until ! publication ( ,geo4 ,adams's important ,geometrical & ,graphical ,essays1 ,conta9+ a ,description ( ,ma!matical ,in/rum5ts1 9 #agia4 ,9 ?is "w we h an able discussion ( ! be/ survey+ in/rum5ts !n 9 use4 ,x 0 mu* ext5d$ 9 lat] editions by ! descriptions ( ! great improvem5ts made 9 ! con/ruction ( in/rum5ts by ,jesse ,ramsd51 z also by ! inv5tion ( ! box-sextant by ,wm4 ,jones4 ,! la/ edition c>ries ! subject well up to date at ! beg9n+ ( ! la/ c5tury 7#ahjc74 #f4--;,9 ! la/ c5tury no orig9al "w appe>$ on ! subject till ,f4 ,w4 ,simms's treatise on ,ma!matical ,in/rum5ts1 #ahcd4 ,?is small "w is limit$ to descriptions ( popul> in/rum5ts = l& survey+ & levell+4 ,x 0 probably call$ hurri$ly into exi/5ce to supply a want at ! comm5cem5t ( ! railway mania4 ,ano!r small popul> "w1 by ! late ,j4 ,f4 ,hea!r1 #ahdi1 appe>$ 9 ,weale's ,rudim5t>y ,s]ies4 ,?is 0 almo/ entirely compil$1 old & ev5 !n obsolete engrav+s be+ us$4 ,no "w 9 ! ,engli% language1 f an e>ly date 9 ! la/ c5tury1 is f\nd to treat ! subject compreh5sively1 or to br+ x ne>ly up to date ) ! advanc$ "w ( our be/ opticians ( ! p]iod at :i* x 0 publi%$4 #g4--;,9 ,g]many we h rec5t works ( an altoge!r high] ord] 9 ,die ,in/rum5te und ,w]kzeuge d] hoh]5 und ni$]5 ,messkun/1 s[ie d] geometri*5 ,zei*n5kun/2 ihre ,!orie1 ,con/ruction1 ,gebrau* und ,prufung1 by ,c4 ,f4 ,s*neitl]1 #ahdh2 & a "w ^u ! l>g] in/rum5ts1 ,die geometris*5 ,in/rum5te1 by ,dr4 ,g4 ,c4 ,hunu1 #ahfd4 ,^! works are orig9al1 & ent] ably into con/ructive details4 ,! au?ors1 h[ev]1 d & m5tion1 & 7 possibly unacqua9t$ )1 _m excell5t in/rum5ts 9 ! h&s ( ! ,briti% surveyor4 ,z reg>ds reflect+ in/rum5ts1 :i* d]ive _! fir/ pr9ciples f ,hadley's sextant1 !re is no "w 9 :i* ^! are treat$ s ably z t ( ! ,italian1 ,capta9 ,g4 ,b4 ,magnaghi1 9 ,gli ,/rum5ti a ,reflessione p] ,misur>e ,angoli1 #ahge4 ,! consid]ation ( ^! in/rum5ts is1 h[ev]1 9 ?is "w m 9 ref]5ce to a/ronomical & nautical obs]vations ?an to survey+4 #h4--,! important class ( subt5se in/rum5ts1 ! use ( :i* 0 fir/ propos$ by our c\ntryman1 ,james ,watt1 9 #agga1 & br\ght out by ,wm4 ,gre5 9 #aggh1 s9ce re9v5t$ 9 ,italy by ,j4 ,porro1 #ahbc1 ( :i* we h a description 9 8 "w1 ,la ,ta*omtre1 ou l',art de lev] les ,plans et de faire les ,nivellem5ts1 #aheh1 is n[ 9 ext5sive use on ! ,cont95t1 & to "s ext5t 9 ,am]ica4 ,_! use is becom+ m g5]al 9 ?is c\ntry b !y are n ne>ly s well kn[n z !y %\ld be4 ,"o ( ! fir/ 0 ,edgecombe's little-us$ /adiomet]1 ( :i* we h descriptions1 )\t any recognition ( ! optical correction always requir$ to r5d] ?is in/rum5t practical2 & "s descriptions ( ,eckhold's omnimet]1 giv5 g5]ally ) an illu/ration ( an e>ly ab&on$ =m ( ! in/rum5t4 ,m rec5tly we h ! subject ( subt5se in/rum5ts ably discuss$ 9 a pap] by ,b4 ,h4 ,br\gh1 ,c4,e41 on ,ta*eometry1 z x is t]m$1 read be=e ! ,in/4 ,c4,e4s1 #ahhg4 #i4--;,classification4--,! survey+ in/rum5ts necess>y to be employ$ on any p>ticul> survey w dep5d1 9 a great measure1 ^u ! nature ( ! "w to be p]=m$4 ,?us1 if x is = a simple plan ( an e/ate1 ! surveyor requires to asc]ta9 ! positions ( build+s & important objects1 ! int]nal divisions ( ! l&1 & ! surr\nd+ b\nd>ies ( ! e/ate1 plac+ all p>ts 9 _! true horizontal positions & be>+s 9 relation to ! po9ts ( ! compass4 ,if x is = a topographical survey ( great ext5t1 he requires ^! matt]s 9 less detail1 b1 9 addition to ! above1 means ( f9d+ ! true latitudes & longitudes1 & ! relative altitudes ( ! p>ts ( 8 "w4 ,if = a railway1 a canal1 or wat]-works1 he requires to asc]ta91 besides ! g5]al horizontal plan1 especially ! altitudes ( all p>ts ( 8 "w v exactly4 ,if x is = coa/ survey1 he requires1 besides ! be>+s1 ! exact relative trigonometrical positions ( all p>ts ( ! coa/-l9e1 z also ! relative s\nd+s on ! sea front4 ,if = a m9+ survey1 he requires to asc]ta91 besides ! horizontal plan1 sections %[+ ! position & dep?s ( /rata1 faults1 ve9s1 etc42 &1 z ! "w is pr9cipally und]gr\nd1 x is necess>y t he %\ld be able to take 8 obs]vations by artificial light4 ,x becomes1 !re=e1 cle> t special in/rum5ts c be adapt$1 m or less p]fectly1 to ^! v>i\s k9ds ( "w )\t t am\nt ( complication & ( weight :i* w\ld be requir$ 9 any s+le in/rum5t con/ruct$ to p]=m _m ( ! above-nam$ functions4 #aj4--,tak+ ! subject 9 a g5]al way1 ! in/rum5tal aid ( ! greate/ importance 9 ! "w a surveyor has to p]=m is su* z w provide measurem5ts ( di/ances & ( angles by :i* he may be enabl$ to make a horizontal plan or map ( ! gr\nd he surveys to a measurable scale4 ,! me?od employ$ to secure ?is object is by tak+ l9e> measurem5ts 9 c]ta9 l9es to fix$ positions1 or /ations1 z !y are t]m$1 & by tak+ angles 9 relation !reto f su* /ations to prom95t po9ts ( view1 :i* may be ei!r natural or artificial objects4 ,to obta9 ?is end1 he requires means ( measur+ su* l9es1 & "s in/rum5t t w take angles ( position 9 ! horizontal plane1 or1 z x is t]m$1 9 azimu?4 #aa4--,! in/rum5ts us$ 9 practice = measur+ ! complete circle 9 angles ( azimu? are ! v>i\s k9ds ( !odolites1 includ+ transits1 omnimet]s1 ta*eomet]s1 circumf]5t]s1 also m9+-dials ( v>i\s k9ds1 prismatic compasses1 & plane-tables4 ,in/rum5ts limit$ to measur+ angles ^u ! plane1 )9 a segm5t ( a circle1 are sextants1 box-sextants1 & semi-circumf]5t]s4 ,in/rum5ts adapt$ to take c]ta9 fix$ angles only are ! optical squ>e 7#ij71 ! cross-/aff 7#ij & #de71 ! apomecomet] 7#de only74 ,! !odolite be+ a univ]sal in/rum5t1 is us$ = tak+ angles 9 altitude z well z 9 plane4 ,! sextant is also adapt$ to ?is4 ,circumf]5t]s & m9+ dials are g5]ally con/ruct$ to measure altitudes less exactly ?an ! !odolite4 ,9 ext5sive surveys ( c\ntries a con/ant *eck is requir$ by tak+ ! latitude & longitude1 = :i* a good transit in/rum5t is requir$ to take obs]vations ( cele/ial bodies1 & a reliable *ronomet]4 #ab4--,practically = tak+ altitudes = railway1 canal1 road1 & dra9age survey1 a telescopic level is us$1 ei!r ) or )\t a magnetic compass4 ,= topographical "w & measurem5ts ( great altitudes 9 ext5sive surveys1 ! !odolite1 an]oid or m]curial b>omet]1 or boil+-po9t !rmomet] is us$4 ,9 important surveys ( m\nta9\s c\ntries1 all ( ^! in/rum5ts are us$1 ! "o z a *eck ^u ! o!r4 ,= tak+ m]ely angles ( incl9ation ( surface1 angles ( embankm5t or cutt+1 & dip ( /rata1 a cl9omet] ( "s k9d is us$4 ,"s g5]al details ( con/ruction w be consid]$ 9 ?is *apt] be=e proce$+ ) ! details ( ! in/rum5ts m5tion$ above1 & "s p>ticul>s also :i* x w\ld be difficult to introduce h]eaft]4 #ac4--,qualities ( ,"w4--,! qualities t in/rum5ts %\ld possess w be sep>ately discuss$1 ) ! description ( ea* special in/rum5t4 ,x may be /at$ g5]ally t mu* ( ! quality ( survey+ in/rum5ts dep5ds ^u ! p]fection ( ! tools us$ 9 _! manufacture1 b v mu* also dep5ds ^u ! "* ( ! man :o produces !m--n only ^u 8 intellect1 b :e!r 8 *ief object is ! p]fection ( 8 "w1 or ! am\nt ( pr(it he c obta9 f x4 ,x is g5]ally kn[n 9 all bran*es1 z a rule1 t ! *eap] k9ds ( "w1 f ! less c>e requir$ 9 details1 secure ! greate/ pr(its4 ,9 ! au?or's & "s o!r optical works1 a completely fitt$ eng9e]'s %op is employ$ to keep tools 9 p]fect ord]1 make special tools1 & produce ! heavi] class ( "w1 = :i* ! eng9e] is bett] adapt$ ?an ! ma!matical fram]4 ,x is also advantage\s at all times to h at lea/ "o skill$ eng9e]1 :o is /yl$ ! eng9e]1 9 a work%op :]e z _m z fifty m5 are employ$4 #ad4--,metals4--,! alloys g5]ally us$ 9 ! con/ruction ( survey+ in/rum5ts are brass1 gun-metal1 bell-metal1 & occasionally electrum or ,g]man silv]1 silv]1 alum9ium1 gold1 & plat9um4 ,^! are requir$ to possess c]ta9 qualities1 &1 :]e ! magnetic ne$le is us$1 to be p]fectly pure or free f iron4 ,! c]ta9ty ( copp] alloys be+ q free f iron is "o ( ! great tr\bles ) :i* ! manufactur] ( magnetic in/rum5ts has to cont5d :5 obta9+ 8 ca/+s f ! ord9>y comm]cial f\nd]4 ,?is has l$ ! au?or1 & "s o!rs 9 8 l9e ( bus9ess1 to ca/ _! own metals z ! only means ( gett+ !m pure4 ,:]e ! metal is _h f ! comm]cial f\nd]1 e "p ( ! ca/+ %\ld be c>efully br\ght )9 ! influ5ce ( a delicately-susp5d$ magnetic ne$le4 ,if ! slighte/ attraction be f\nd 9 any "p ( ! ca/+ x %\ld be reject$4 #ae4--;,alum9ium1 f its mu* l[] price ( production ?an =m]ly1 & f its extreme lightness & fre$om f t5d5cy to oxidation1 except :5 expos$ to sea air1 z ! pres5ce ( common salt appe>s to completely decompose ! surface1 is n[ recognis$ z a metal :i* may be us$ = ! manufacture ( p>ts ( survey+ in/rum5ts4 ,?is metal1 9 its pure /ate1 is too s(t & malleable to be us$ advantage\sly = _m p>ts ( ^! in/rum5ts4 ,x1 h[ev]1 appe>s to alloy ) _m metals1 "s ( :i* increase its h>dness & /iffness )\t mak+ its specific weight m ?an "o-?ird t ( gun-metal1 & )\t great] liability to oxidation4 ,! foll[+ alloys are n[ (f]$ 9 comm]ce3--,alum9ium-nickel1 al-*romium1 al-tung/51 al-titanium4 ,^! possess _m di/9ct qualities1 & may be f\nd1 "u judici\s h&l+1 useful = _m p>ts ( ^! in/rum5ts4 ,!re is1 h[ev]1 f ! f95ess ( gra9 ( alum9ium1 ev5 9 its alloys1 a t5d5cy to fret 9 surfaces expos$ to friction4 ,?is c be avoid$ 9 _m cases by l9+ su* p>ts ) a suitable metal )\t mat]ially *ang+ ! g5]al lightness ( ! in/rum5t4 ,! au?or has devot$ mu* "t to =m+ & te/+ alum9ium alloys1 p>ticul>ly ) nickel1 b !re is no d\bt !re is /ill mu* to be le>n$ ( ! alloys ( ?is beautiful metal1 z x is /ill1 comp>atively1 s new to manufactur]s4 ,! au?or has f\nd _m difficulties to be ov]come 9 obta9+ f9e solid ca/+s1 &1 z f> z 8 exp]i5ce goes1 !re are only v imp]fect sold]s (f]$ = x 9 comm]ce4 ,x !re=e rema9s advisable to "w up all p>ts 9 ! solid 9 ?is metal z f> z possible1 & :]e !re is risk ( exposure to salt air to conf9e ! alum9ium alloys to su* p>ts ( ! in/rum5t z may n be s]i\sly injur$ by surface oxidation4 ,on ! :ole ?is metal is only recomm5d$ :]e lightness is ( m importance ?an durability4 #af4--,! g5]al object to be obta9$ 9 ! di/ribution ( metals to ! v>i\s p>ts ( an in/rum5t is to get good we>+ surface ) solidity1 & an ev5 balance ( ! mov+ p>ts ) mod]ate lightness4 ,9 practice1 su* p>ts z c be ?or\ghly hamm]$1 drawn1 or roll$ 9 a cold /ate w =m /iff1 ela/ic1 & durable p>ts 9 brass4 ,= ! composition ( ?is metal ! au?or uses copp] #fi1 z9c #cj1 t9 #ja4 ,! t9 is us$ 9 place ( ! lead ( ! ord9>y f\nd]1 & produces !reby a /iff] alloy4 ,= su* p>ts z require /iffness1 :]e suffici5t hamm]+ is impossible1 or ! metal is 9 consid]able mass1 gun-metal %\ld be us$4 ,! au?or has f\nd ! be/ practical mixture = ?is--pure copp] #hh1 t9 #ab4 ,= c5tres requir+ great rigidity1 z ^? ( ! !odolite1 level1 or sextant1 bell-metal is us$ by all ! be/ mak]s4 ,?is %\ld be ( su* composition t x _c be p]man5tly b5t )\t imm$iate fracture4 ,x %\ld possess ab\t ! h>dness & /iffness ( untemp]$ /eel4 ,! be/ alloy ! au?or has f\nd = ! bell-metal = ^! in/rum5ts is copp] #hc1 t9 #ag4 ,if v small ca/+s are made ) ?is alloy !y are some:at brittle1 probably f ! rapid cool+ ( ! surface 9 ! m\ld1 !re=e1 = small ca/+s1 a saf] alloy is copp] #he1 t9 #ae4 #ag4--;,9 mak+ all ! above alloys1 = ! be/ results ! metals are assum$ to be comm]cially pure4 ,! introduction ( a little unc]ta9 scrap1 :i* ! ord9>y f\nd] is s fond ( us+ to make 8 metal run d[n1 w (t5 f\l a pot ( metal4 ,9 all cases ( copp] alloys ! copp] %\ld be entirely melt$ be=e ! addition ( ! z9c or t91 aft] :i* x %\ld be ?or\ghly /irr$ ) a *>r$ /ick or e>!nw>e rod1 & !n be ca/ 9 small +ots1 to be re-melt$ & ca/ a second or1 ev5 bett]1 a ?ird "t be=e melt+ = ! f9al ca/+s4 #ah4--,workman%ip4--,x w\ld be q impossible1 )9 ! limits ( ?is "w1 to give su* p>ticul>s ( ! workman%ip 9 survey+ in/rum5ts z to enable a p]son to manufacture !m )\t practical k ( ! manipulation ( ! v>i\s bran*es ( ! art1 b x is ?\ght t a g5]al sket* ( ! v>i\s op]ations entail$1 :i* v>y some:at 9 diff]5t work%ops1 may be useful4 ,"s ( ^! p>ticul>s may be also useful to ! surveyor1 n only z g5]al k ( ! in/rum5ts he uses1 b 9 "s cases ( accid5ts & em]g5cies1 & = ! sake ( keep+ 8 in/rum5ts 9 ord] :5 he is f> away f ! manufactur+ optician4 #ai4--;,fram+ ,"w4--,! ord9>y turn+ & fil+ ( metals1 & "s k ( ! workman%ip ( ! bus9ess1 are assum$ to be und]/ood by ^? :o may use ?is book = special con/ructive details4 ,! tools 9 a ma!matical or philosophical in/rum5t-mak]'s work%op1 :]e high-class "w is done1 ne>ly resemble 9 e way ^? ( a good eng9e]'s %op1 except t on an av]age ! tools are mu* light]1 & run at a high] spe$4 ,:]e ! works are ext5sive1 /eam-p[]1 a gas eng9e1 or electric-motors are us$4 ,9 small %ops ! foot la! is ! only important tool4 ,!re is a great advantage 9 us+ p[] = good "w1 z ! oscillation ( ! tool1 :i* is always caus$ by ! action ( ! foot1 produces :at is t]m$ a *att] ^u ! "w4 ,= turn+ brass & silv]1 a high spe$ is desirable ) a la! ( suffici5t rigidity to give no s5sible vibration4 ,a surface cut spe$ ( ab\t #bej feet p] m9ute %\ld be aim$ at4 ,= turn+ gun-metal1 ,g]man silv]1 & mild wr\ght-iron1 ab\t #ajj feet p] m9ute is requir$4 ,= turn+ bell-metal & ca/-/eel1 a v sl[ spe$ is requir$--ab\t #af feet p] m9ute4 ,! la! %\ld !re=e possess means ( ensur+ ^! diff]5ces by back ge>1 ov]head motions or o!rwise4 #bj4--,tools4--,! la! ( ! mo/ suitable con/ruction = survey+ in/rum5ts has ! upp] surfaces ( ! b$1 "o side ( section1 & ! o!r flat--n bo? flat z 9 _m eng9e]s' la!s4 ,?is ensures ! c]ta9ty t re/s & o!r tools c be firmly clamp$ d[n )\t possibility ( lat]al %ake4 ,! slide-re/ %\ld h a broad base & be provid$ ) direct p]p5dicul> & rotatory motions1 ) means ( clamp+ ! motive p>ts n 9 imm$iate use1 z smoo? cuts c only be obta9$ on copp] alloys by p]fect rigidity ( all p>ts ( ! tools4 ,! la! %\ld also possess a b$-screw & ov]head motions suitable = apply+ fly+ cutt]s & mill+-tools 9 e desir$ direction ^u ! piece ( "w :5 x is once *uck$ 9 ! la!4 ,a univ]sal %ap+ ma*9e & a mill+ ma*9e g5]ally replace ! plan+ ma*9e ( ! eng9e]4 ,^! tools are suffici5t = produc+ ! flat surfaces = all ord9>y "w4 ,ev5 :5 p[] is g5]ally us$1 small h& plan+ & %ap+ ma*9es1 work$ ) a lev]1 are v useful = work+ up s+le pieces & small p>ts4 ,a circul> saw & a good gr9d/one are also indisp5sable4 ,) good rigid tools1 well appli$1 v little "w is left = ! r\gh or ba/>d file2 on _m in/rum5ts none :atev]--only a little f9e scrap+1 sup]f9e fil+ & /on+ be+ requir$4 #ba4--,! greate/ te*nical skill requir$ 9 ! manufacture ( survey+ in/rum5ts is 9 ! pr9cipal axes ( ^! in/rum5ts1 p>ticul>ly 9 !odolites1 ta*eomet]s1 sextants1 & "s k9ds ( m9+ dials1 :]e9 a class ( "w is dem&$ :i* mu/ be p]=m$ by a skilful1 exp]i5c$1 & c>eful workman4 ,! axis ( ^! in/rum5ts1 z already m5tion$1 %\ld be =m$ ( a ca/+ ( good bell-metal4 ,?is axis mu/ be turn$ ^u its own c5tres1 :i* %\ld be drill$ up suffici5tly to keep a /eady be>+1 s t ! tru? ( ! "w is q indep5d5t ( any fault !re may be 9 ! la!4 ,! turn+ mu/ be p]=m$ ) a po9t-tool1 ! upp] angle ( :i* %\ld be ab\t #fj4 ,?is %\ld be kept con/antly %>p1 & be all[$ to take only ! f9e/ possible cut at a sl[ spe$4 ,! slide-re/ %\ld be set to ! exact angle ( ! tap] ( ! axis4 ,! socket1 if x is n v /\t1 %\ld be plac$ 9 a massive metal box & emb$d$ 9 pla/] ( ,p>is1 :i* mu/ be all[$ to set p]fectly h>d be=e use4 ,! socket is turn$ out1 if possible1 or o!rwise x is r\gh$ out ) a h>d /eel flut$ cutt]1 & f9ally cut up by ano!r flut$ cutt] :i* has be5 c>efully gr\nd to ! correct cone int5d$ = ! f9i%$ axis4 ,! axis is *amb]$ back 9 its c5tral "p1 s t x may fit ! socket = ab\t f half to ?ree qu>t]s ( an in*1 only at its extreme ends4 ,aft] turn+ & bor+ z correctly z possible1 ! axis & socket are gr\nd toge!r ) s(t oil-/one du/ to true =m4 ,aft] ?is1 ! surface is turn$1 or scrap$ entirely (f1 ) a %>p tool1 & ! axis is aga9 fitt$ by rubb+ contact only4 ,x is mo/ important to be sure t no grit rema9s emb$d$ 9 ! metal f ! gr9d+1 z ?is w be sure to "w out & abrade ! axis aft]w>ds4 #bb4--,! same c>e z is necess>y to be be/[$ ^u ! c5tres ( in/rum5ts1 is requir$ = tang5t motion screws :5 ^! act directly )\t c\nt] spr+s4 ,^! %\ld be made1 if possible1 ( h>d drawn wire4 ,!y %\ld be turn$ on _! own c5tres1 ! cut ( ! tool be+ extremely light to avoid flexure1 all screws ( ov] #a_/h-;in* diamet] %\ld be cut direct 9 a light screw-cutt+ la!1 al?\gh x is advantage\s to run a pair ( dies lightly ov] !m aft]w>ds to make ! ?read smoo?1 & ensure a p]fect fit 9 ! nut4 #bc4--,sold]+4--,besides ! tubes ( in/rum5ts1 all p>ts :i* are difficult or impossible to be =m$ advantage\sly 9 a s+le ca/+1 are h>d sold]$ or braz$ toge!r :]e ?is w r5d] ! "p ( ! in/rum5t m rigid ?an by screw atta*m5t4 ,! p9s ( all screws %\ld be made ( drawn metal1 to :i* ! "p to =m ! mill$ head may be a ca/+4 ,h>d sold]+ 9 ?is c\ntry is n[ g5]ally p]=m$ ) "o ( ,flet*]'s gas bl[-pipes1 ! p>ts ( ! in/rum5t1 if l>ge1 be+ emb$d$ 9 a pan ( *>coal4 ,! au?or uses a pair ( gas bl[-pipes1 tak+ ! bla/ ( a c5trifugal bl[] driv5 by an electric motor4 ,^! bl[-pipes are plac$ opposite to ea* o!r1 s t ! pieces be+ sold]$ toge!r are entirely surr\nd$ by ! flames project$ f bo? sides4 ,! flames ( ! gas bl[-pipe may1 ) ?is app>atus1 be r$uc$ to m]e po9ts = small pieces4 ,! sold] employ$ = ord9>y "w is f9e spelt] ) a flux ( gr\nd borax4 ,! mo/ conv5i5t me?od ( us+ ?is is to put ab\t a qu>t] ( a p\nd ( spelt] & an ounce ( gr\nd borax 9 a sauc]1 & add suffici5t wat] to cov] x4 ,! borax & spelt] may !n be tak5 up toge!r ) a small spoon & plac$ directly ^u ! clean "p ( ! metal :i* is to be sold]$4 ,) deep or difficult jo9ts x is well to soak ! :ole ( ! pieces an h\r or s 9 a saturat$ solution ( borax be=e comm5c+ ! sold]+4 ,= sold]+ v small pieces1 or = sold]+ /eel to brass1 silv] sold] is bett] ?an spelt]2 x appe>s to bite ! /eel m firmly & x runs at a l[] heat4 #bd4--,s(t ,sold]+1 or :at is t]m$ 9 ! trade sweat+1 %\ld be resort$ to z seldom z possible4 ,x is necess>y 9 mak+ atta*m5ts to drawn tubes1 z ! heat ( h>d sold]+ w\ld de/roy ! rigidity ( ! tube1 due to ! draw+ processes4 ,9 ?is case1 :]e s(t sold] is employ$1 ! tube %\ld be1 if possible1 surr\nd$ by a b& ( solid metal1 :i* =ms a "p ( ! atta*m5t1 or ! atta*$ "p %\ld be well secur$ ) screws1 tapp$ dry1 be=e ! sold]+ is comm5c$4 ,s(t sold]+ on brass is g5]ally v deceptive2 ! sold] may =m a glaze r\nd ! jo9t ) no atta*m5t )94 ,_m surveyors w recognise ?is :o may h _h "o ( ! slop-made sold]$-up levels fall to pieces 9 _! "w by a simple j> accid5tally giv5 to ! in/rum5t4 #be4--;,f9i%+ ma!matical "w3 ! surface z x leaves ! sup]f9e file is br\ght up by cutt+ x d[n to a mat ) ,wat] ( ,ayr /one1 & f9ally cle>+ ) s(t grey slate-/one4 #bf4--,poli%+4--,:]e brightness is desirable1 p>ticul>ly = /eel "w1 wa%-em]y & ,fr5* poli%+ pap] are us$4 ,heads ( screws & small turn$ p>ts are bett] f9i%$ (f by a clean cut or ) ! burni%] on ! la!4 #bg4--,optical ,black4--,! int]ior p>ts ( telescopes are pa9t$ ov] ) a dull black pa9t1 ! object ( :i* is to cut (f ! reflection ( extrane\s light ent]+ ! object-glass obliquely4 ,optical black is made by f9ely gr9d+ drop-black 9 turps or spirits ^u a /one ) a mull]1 ?is is aft]w>ds /ra9$ ?r\gh f9e musl92 if x is gr\nd 9 turps a little good gold-size is add$2 if 9 _s1 a little _s v>ni%4 ,! black %\ld be te/$4 ,x %\ld appe> q dull1 & yet be suffici5tly firm to be> ! f+] rubb+ ^u x )\t soil+4 ,= eye-pieces1 ! dull black g5]ally employ$ is due to oxidation obta9$ by burn+ (f an acid solution ( cupr\s-nitrate 9 a gas flame4 #bh4--;,bronz+4--,= ! protection ( f9i%$ metal "w 9 survey+ in/rum5ts ! surface is g5]ally bronz$1 z x is t]m$1 leav+ bright only su* p>ts z are requir$ to be easily se51 su* z mill$-heads1 heads ( screws1 etc4 ,! d>k gray ( ! bronze is also mu* m pleasant to ! eye ?an a bright surface1 p>ticul>ly :5 out 9 ! sunlight1 s t bright in/rum5ts h gone ne>ly out ( use4 ,! bronz+ is effect$ by ! application ( a liquid t w corrode ! metal &1 at ! same "t1 leave a d>k pulv]5t deposit ^u x4 ,!re are a great numb] ( bronzes to be _h1 b t :i* ! au?or has f\nd to be ! mo/ p]man5t & safe/ f aft] corrosion is plat9ic-*loride1 dissolv$ 9 suffici5t wat]4 ,?is bronze is well kn[n1 b is n us$ s frequ5tly z x %\ld be f its great exp5se4 ,! bronzes :i* are to be p>ticul>ly avoid$ are ^? conta9+ m]curic-di*loride4 ,^! are v *eap1 & !y give a f9e d>k surface2 b !y are c]ta9 to rot ! brass & produce a pitt$ or spott$ appe>ance aft] ! in/rum5t has be5 mu* expos$4 ,! bronze1 :atev] k9d is us$1 is put on ) a bru% ^u ! surface ( ! metal1 :i* mu/ be q clean to receive x4 ,aft] ! col\r is well br\ght up by pass+ ! bru% ov] ! "w sev]al times1 ! "w is !n ?or\ghly gone ov] ) a h>d bru% & f9e black lead until e trace ( free corrosive liquid is remov$1 z f> z possible1 f ! surface1 & ! "w is left q dry 9 all p>ts4 ,"s mak]s put a ?9 coat ( asphaltum1 dissolv$ 9 turp5t9e1 ov] ?is1 :i* produces a light black surface4 ,"s1 to save tr\ble & exp5se1 simply pa9t ! in/rum5t ) black v>ni% )\t bronz+4 ,?is looks v sm>t at fir/1 b ! black is v liable to *ip (f 9 use & make ! in/rum5t unsightly4 #bi4--,lacqu]+4--,all p>ts ( in/rum5ts int5d$ to be left bright1 z well z all prop]ly bronz$ p>ts1 are sep>ately cov]$ ) a ?9 coat+ ( lacqu]1 ! application ( :i* is te*nically t]m$ v>ni%+4 ,! metal is rais$ to an equal temp]ature ( ab\t #bjj ,fahr41 & ! v>ni% is appli$ ) a f9e1 flat camel-hair bru%4 ,! process requires consid]able skill1 s t only a few workm5 d x to p]fection4 ,special v>ni%es are made = ! philosophical & ma!matical in/rum5t trades1 all ( :i* h a base ( f9e %ellac1 dissolv$ 9 absolute alcohol4 #cj4--;,engrav+ ( figures1 words1 etc41 :]e !re is mu* repetition1 is be/ done by ! engrav+ ma*9e--g5]al "w by ! ord9>y skill$ engrav]4 ,! me?od employ$ = ! graduation ( in/rum5ts w be consid]$ fur!r on 9 ! discussion ( in/rum5ts read+ ) a v]ni] scale4 #ca4--,/yle4--,?is mu/1 ( c\rse1 dep5d ^u ! ta/e ( ! manufactur]4 ,9 mod]n ma*9]y1 & 9 sci5tific in/rum5ts1 !re is a /rong t5d5cy to avoid all useless m\ld+s or ornam5ts1 & to f9i% all p>ts ( ! "w uni=mly ) clean smoo? cuts4 ,9 survey+ in/rum5ts :i* h to be h&l$1 x is desirable to avoid angles z mu* z possible1 bo? by =m & by r\nd+ (f all corn]s neatly1 s z to produce a g5]al feel+ ( smoo?ness ov] ! :ole in/rum5t2 useless metal1 z1 = in/ance1 9 mill$ heads ( screws1 %\ld be holl[$ away to avoid weight1 & ?is object %\ld be obs]v$ 9 ! g5]al di/ribution ( metal1 nev] neglect+ at ! same "t to insure ! firmness ( ! in/rum5t4 ,p>ts %ap$ out ( ! solid may be made mu* light] ?an :5 screw$ toge!r 9 sep>ate pieces & are ( great] rigidity1 & admit ( bett] /yle4 ,! lead+ mak]s all h a /yle ( _! own1 "s m graceful ?an o!rs2 mo/ ( ! small] mak]s make bad copies ( ^! designs4 #cb4--;,glass-,"w4--,! mo/ important te*nical "w1 except p]haps ! graduation 9 survey+ in/rum5ts1 is f\nd 9 ! optical p>ts1 ( :i* only a brief description c be giv54 ,! glass us$ = ! l5ses1 p>ticul>ly = ! a*romatics1 is t manufactur$ by ,messrs4 ,*ance ,bros41 ( ,birm+ham1 or by ,m4 ,mantois1 ( ,p>is1 bo? ( :i* firms use ! process discov]$ by ,gu9>d1 ( ,solo?urn1 9 ,switz]l&1 :i* 0 aft]w>ds mu* improv$ by ,geo4 ,bontemps4 ,?is glass is ne>ly :ite & transp>5t1 ( uni=m d5sity1 & free f ve9s & /ri4 ,x is also p]fectly anneal$1 :i* is important4 ,! foll[+ k9ds ( glass are usually employ$ = ! object-glasses ( survey+ in/rum5ts3-- ---------------------------------------- ---------------- ,index ( ,spectrum ,l9es4 ,d5sity4 -------------------------------- ,c ,d ,f ,g ---------------------------------------- ------------- ,h>d ,cr[n #bdhe #aeadf #aeagb #aebcb #aebhj ,d5se ,fl9t #cffj #afage #afbbd #afcdh #afdec ---------------------------------------- ------------- ,^! p>ticul>s are giv5 by ! glass-mak]s :o supply ! glass4 ,= *eapness ! optical cr[n-glass is (t5 replac$ by common plate-glass4 ,a specially cle> & h>d glass is made by ,%ott1 ( ,j5a1 b e>ly specim5s ( ?is glass did n appe> to /& climatic influ5ces4 ,?is defect is n[ rem$i$1 & ! glass is v pure 9 body1 b n free f air-bubbles4 #cc4--,two pairs ( tools are us$ = glass-gr9d+ = e curve4 ,^! possess two sph]ical surfaces1 "o ( ea* pair resembl+ a %all[ bas91 & ! o!r1 ( ! same diamet]1 fitt+ into ?is4 ,aft] turn+ ! tools !y are gr\nd toge!r1 & are aft]w>ds kept 9 ord] by con/ant regr9d+ toge!r4 ,^! tools may be ( ca/-iron or brass4 ,! work+ surface ( ! tool is1 ( c\rse1 ( ! rev]se curvature to t ( ! glass to be gr\nd 9 x4 ,:5 ! glass is gr\nd by h&1 ea* tool possesses a screw$ socket by :i* x c be screw$ to a /ump or po/1 fix$ 9 ! gr\nd1 or to a %ort knob-h&le to be us$ z ! upp] tool by h&4 ,= work+ a glass1 or sev]al glasses1 x or !y are cem5t$ ^u a h& tool or hold]1 :i* is ( less curvature ?an ! work+ tool4 ,! work+ is p]=m$ by rubb+ 9 a /raight alt]nately ) a circul> direction1 ) a c]ta9 /roke difficult to describe1 at ! same "t walk+ r\nd ! po/ to rev]se all positions4 ,! gr9d+ is cont9u$ ov] ! sph]ical tool until ! surface ( ! glass is br\ght up to its curvature1 be+ suppli$ at fir/ ) co>se em]y1 #fj-;hole1 :i* is kept 9 a v moi/ /ate1 & aft]w>ds ) f9] em]y1 #ajj-;hole1 & !n by eight or t5 /ill f9] grades1 c>efully wa%+ (f betwe5 ! processes1 & res]v+ ! mud mo/ c>efully = wa%-em]y1 :i* is us$ 9 complet+ ! gr9d+4 ,:]e ma*9]y is employ$1 h& motions are imitat$ z ne>ly z possible by ! motion ( ! tools1 p>ticul>ly = ! =m+ processes4 #cd4--,! wa%-em]y is =m$ ( p>ticles :i* are held susp5d$ = a m9ute or s :5 ! mud is /irr$ 9 a l>ge vessel ( wat]4 ,?is wat] is drawn (f = f9al settlem5t to =m ! wa%4 ,! f9al gr9d+ ) ! wa% is cont9u$ until ! em]y appe>s jet black on ! surface ( ! glass1 :i* has !n a semi-poli%$1 almo/ metallic1 lu/re4 #ce4--,poli%+4--,?is is p]=m$ 9 v>i\s ways1 g5]ally moi/ clo? is plac$ ov] ! tool4 ,! bett] way is to cov] ! poli%+ tool ) pat*es ( h>d pit*1 :i* are made to take ! =m ( ! h& tool by hav+ ! fell[ tool to t us$ 9 work+ press$ ^u ! surface :ile ! pit* is /ill w>m1 us+ a %eet ( moi/ tissue-pap] to prev5t adhesion4 ,! poli%+ is effect$ 9 ! same mann] z ! gr9d+1 b ) p]oxide ( t9 7putty p[d]71 or r\ge4 #cf4--,! great diff]5ce 9 ! value ( a*romatic l5ses dep5ds ^u ! tru? ( ! curvature due to ! accuracy ( ! tools & ! cont9uity ( ! gr9d+ processes until a p]fect surface is produc$ be=e poli%+1 s t a giv5 l5s may h treble ! lab\r be/[$ ^u x to "o ( inf]ior quality 9 ! gr9d+ only4 ,beyond ?is its ultimate p]fection w dep5d mu* ^u ! poli%4 #cg4--;,x may be well "h to note h[ ?is may be obs]v$4 ,a good te/ is to ?r[ ! %ad[ ( a ?9 object1 z t ( a piece ( wire ^u ! surface obliquely4 ,?is %\ld %[ cle> edges :5 ! l5s is *ang$ to all positions = reflection4 ,! te/ ( poli% is really only ! te/ ( brightness ( ! surface ( ! glass1 :i* may be di/+ui%$ 9 _m ways t w readily sugge/ !mselves4 ,! importance ( ! p]fect gr9d+ is t to :i* att5tion is desir$ to be drawn4 #ch4--;,c5tr+--,figur+ & ,te/+4--,aft] ! above describ$ processes1 ! glass is c5tr$ by gr9d+ (f ! edges until its axis is exactly c5tral ) ! p]iph]y1 s t x c be m\nt$ 9 its cell4 ,x is !n te/$ = figure4 ,! te*nical difficulties ( figur+ are too great to be discuss$ briefly 9 ?is treatise2 mu* ( ?is "w is p]=m$ by ! skill$ workman 9 ! mann] he works 8 tool & applies 8 gr9d+ & poli%+ mat]ial1 e /roke giv+ a slightly diff]5t figure4 ,"s me?od1 h[ev]1 may be giv5 ( te/+1 :i* w be useful 9 e/imat+ ! quality ( a l5s1 irrespective ( its manufacture4 ,to te/ ! objective x may be m\nt$ 9 its telescope & focuss$ ^u a />1 or m practically 9 work%ops1 ^u ! reflection ( ! sun z ?is is se5 9 ! m]cury ( a small bulb ( a !rmomet] plac$ conv5i5tly on a black backgr\nd at z great a di/ance z x is cle>ly visible 9 ! telescope--a common di/ance is #bj feet4 ,! telescope is made to trav]se ! sight$ object s z to cross ! field ( view4 ,if ! focus "u ?is te/ rema9s con/ant1 s t ! image ( ! sun 9 ! m]cury bulb appe>s %>p & )\t col\r1 ! objective is fairly correct$4 ,fur!r in=mation on ?is subject may be ga9$ f a v important pap] read by ,sir ,h[>d ,grubb1 ! em95t optician1 be=e ! ,royal ,in/itution4#a #ci4--,! ,woodwork ( ! ,/&s ( in/rum5ts made 9 ?is c\ntry is g5]ally ( /raight-gra9$ ,honduras mahogany4 ,= occasional "w ! mahogany is bett] if season$ = ?ree or f\r ye>s 9 bo>ds :i* are cut to ?icknesses increas+ by qu>t] in*es1 s t ab\t ! ?ickness ( ! f9i%$ "w 9 "o dim5sion may be us$4 ,:]e a numb] ( /&s ( con/ant dim5sions1 z = ord9>y !odolites & levels1 is requir$1 x is bett] to cut ! mahogany a little ov] f9i%+ size directly f ! fre% log1 & !n all[ x to season ?ree or f\r ye>s4 ,9 ?is mann] any natural w>p ( ! wood takes place be=e x is work$ up1 :i* causes x to /& well aft]w>ds4 #dj4--,lubrication ( ,in/rum5ts4--,= ! lubrication ( all screws1 good wat* oil %\ld be us$4 ,:]e ?is _c be obta9$1 salad oil fill$ up 9 its bottle ) fre%-cut %av+s ( lead w produce a p]fect oil free f acidity4 ,= work+ c5tres & coll>s1 a grease is bett]--t extract$ f pork fat1 by leav+ x 9 ! sun%9e1 answ]s v well1 b :at ! au?or has f\nd be/ = ! purpose is pure vasel9e4 ,?is keeps its greas9ess1 & appe>s to be p]fectly non-corrosive4 ,= ! coll>s ( tang5t screws1 a mixture ( tall[1 wax1 & soap is employ$4 ,?is mixture does n fret out to cause a bite ^u ! surfaces4 ,z ! in/rum5t-mak] leaves ! work+ c5tres ( in/rum5ts !y w g5]ally p]fectly ma9ta9 _! lubrication = f\r or five ye>s1 & x is n well to di/urb !m2 s t ?is note may be consid]$ only = ! re/oration ( old in/rum5ts to ord]1 or = clean+ !m up g5]ally1 :i* is nev]!less be/ done by skilful h&s4 #da4--,pres]vation ( ,in/rum5ts4--,in/rum5ts t h by any accid5t become spla%$1 or dirty by exposure to ra9 & du/ or o!rwise1 may be wa%$ ) damp wa%-lea!r4 ,if a piece ( s(t1 dry lea!r be aft]w>ds moi/5$ ) a little l9se$-oil1 & ?is rubb$ ov] ! in/rum5t :5 x is q dry1 x w re/ore ! orig9al brightness1 & t5d to pres]ve x4 ,= wip+ object-glasses "s pref] a piece ( clean old l951 o!rs an old silk h&k]*ief2 ei!r w answ] if kept q clean4 ,if ! glasses are only du/y1 ! application ( a s(t camel hair bru% is all t is necess>y1 & ?is is q safe f c>ry+ grit4 ,if glasses are /a9$ by slight corrosion1 ?is c be p>tially remov$ by clean _s4 ,9 replac+ glasses1 x is important to obs]ve t ! not* m>ks1 if any1 on ! edges ( ! glass agree1 & t ! d\ble-convex l5s is plac$ outw>ds 9 ! telescope4 #db4--,pack+ ( ,in/rum5ts4--,?is is really a v important matt] seldom e/imat$ at its prop] value4 ,an in/rum5t %\ld lie or /& 9 its case 9 su* a mann] t its mo/ solid p>ts only take ! be>+ surfaces1 & ?us p]fectly secure x4 ,:5 ?is is effect$ !re %\ld be no possibility ( an exceptional j> on any delicate "p f ! jolt+ ( ! conveyance ( ! in/rum5t4 ,great c>e %\ld be tak5 to note h[ ! p>ts ( ! in/rum5t 7 orig9ally arrang$ by ! pack]1 & ?is arrangem5t %\ld always be foll[$ 9 replac+ ! in/rum5t 9 its case to its position1 into :i* x %\ld fall ) p]fect ease4 ,in/rum5ts are frequ5tly /ra9$ by be+ plac$ wrongly 9 _! cases4 ,ev5 ) all ^! precautions1 ! wood ( ! case may %r9k or w>p to a c]ta9 ext5t1 p>ticul>ly 9 tropical climates1 s t ! in/rum5t may be expos$ to ext]nal pressure f clos+ ! case or o!rwise1 s z to injure x or to spoil its adju/m5t4 ,9 su* cases x is bett] to exam9e ! pack+ occasionally1 &1 if ! case does n easily & p]fectly close1 !re is a risk t ! in/rum5t is be+ /ra9$4 ,if ?is is ! case1 assum+ ! in/rum5t to be 9 its correct position1 ! be>+ surfaces %\ld be l[]$ ) ! p5knife or o!r tool1 s t x is j free1 b n to %ake4 ,! au?or 0 ! fir/ to place a piece ( cork "u ea* be>+ surface4 ,?is gives a c]ta9 am\nt ( ela/icity1 ) suffici5t rigidity = support1 to pres]ve ! in/rum5ts f injuri\s j>1 & x may aft]w>ds be cut away m easily ) ! p5knife ?an wood4 #dc4--,) complicat$ in/rum5ts !re are always a numb] ( loose pieces :i* are us$ occasionally ^u or ) ! in/rum5t4 ,^!1 = compactness ( pack+1 are (t5 plac$ "o above ! o!r1 & are liable to get a/ray4 ,x is v desirable t complete p>ts %\ld be arrang$1 z f> z possible1 to g into _! cases 9 any /ate ( adju/m5t1--?is is1 h[ev]1 n always possible4 ,z a rule1 be=e putt+ an in/rum5t or any portions ( x by1 all movable p>ts1 su* z ! telescope1 eyepieces1 etc41 %\ld be clos$ 9 _! close/ =m4 ,p>allel plates %\ld be left squ>e to ! in/rum5t1 ) ! screws loose4 ,g5]ally ! pack] leaves little lib]ty4 ,in/rum5ts are (t5 pack$ s t !y w g into _! cases only j 9 "o /ate ( adju/m5t1 & 9 "o position ( ! movable p>ts4 ,9 ?is case1 great c>e mu/ be tak5 at fir/ 9 exam9+ ! position 9 :i* ! in/rum5t & its p>ts arrive f ! mak]4 ,! late ,m4 ,gav>d1 ( ,p>is1 :o 0 celebrat$ = 8 delicate p5tagraphic in/rum5ts1 & to :om ! writ] owes _m useful h9ts1 put initial lett]s on ! p>ts ( 8 in/rum5ts1 & plac$ pr9t$ labels on ! p>ts ( ! cases :]e ^! %\ld g4 ,mr4 ,h5nessey1 ,fir/ ,assi/ant 9 ! great ,trigonometrical ,survey ( ,india1 gives "s excell5t notes ^u ! subject ( pack+ 9 8 ,topographical ,in/ructions = ! use ( ! ,survey ,dep>tm5t4 ,he recomm5ds ^u op5+ a case t a sket* %\ld be made ( ! cont5ts z !y lie1 & all possible p>ticul>s %\ld be record$2 b 8 mo/ useful h9t is1 always to replace an in/rum5t g5tly1 & 9 no case to use =ce if ! in/rum5t w n fall into its place4 ,unless ! pack+s h be5 damag$ 9 "s way1 ! in/rum5t w g easily into its case1 & if x does n1 x %[s t "s "p is n 9 its prop] position1 & ?is mu/ be c>efully look$ into to avoid injury4 #dd4--,lea!r ,ov] ,cases4--,= an in/rum5t = use 9 ! field x is bett] to h a solid lea!r case ov] ! ord9>y mahogany "o4 ,?is acts z a k9d ( buff]1 & takes (f ! j> ( an accid5tal bl[ ^u ! case1 :i* might o!rwise injure ! in/rum5t4 ,x also protects ! mahogany case f ! w>p+ effect ( direct sun%9e & ra91 & closes ! meet+-jo9t to keep out ! du/4 ,solid lea!r cases are also g5]al = all light in/rum5ts1 r5d]+ a /iff case ( wood or pa/ebo>d unnecess>y4 ,^! admit mo/ p]fectly ( /raps be+ plac$ conv5i5tly to adapt !m to ! p]son = c>ry+4 ,wat]pro( ,cov]s4--,9 v ra9y climates a wat]pro( cov] = a delicate in/rum5t is desirable4 ,?is c be ?r[n ov] ! in/rum5t in/antly 9 case ( a sudd5 /orm1 & ! in/rum5t left ready = cont9u+ ! "w :5 x cle>s up4 ,,footnote3 #a ,proc4 ,royal ,in/itution1 vol4 xi4 p4 #dac4 ,,*apt] ,,ii4 ,,! ,,telescope ,,z ,a ,,"p ,,( ,a ,,survey+ ,,in/rum5t--,,g5]al ,,description--,,qualities--,,optical ,,pr9ciples--,,refraction ,,( ,,glass--,,limit ,,( ,,refraction--,,reflection--,,prisms--,, l5ses1 ,,convex ,,& ,,concave--,,ab]ration--,,=mation ,,( ,,images--,,disp]sion-- ,,a*romatism--,,curvature ,,( ,,l5ses--,,telescopes--,,eye-,,pieces--, ,p[]s-- ,,dynamet]--,,con/ruction ,,( ,,! ,,telescope1 ,,diaphragm--,,webs--,,l9es-- ,,po9ts--,,p>allax--,,exam9ation ,,& ,,adju/m5t4 #de4--;,g5]al ,description ( ! ,telescope4--,?is in/rum5t =ms "p ( ! !odolite1 level1 "s k9ds ( m9]'s dials1 sextants1 plane tables1 & o!r survey+ in/rum5ts4 ,= ?is purpose x is made ( simil> con/ruction to t ( ! refract+ telescope us$ = a/ronomical purposes4 ,! great object desirable 9 ! telescope1 :5 us$ z a "p ( a survey+ in/rum5t1 is t x %all assi/ vision 9 obta9+ ! true direction1 or po9t+ to ! position ( an object 9 su* a mann] t x c be employ$ to asc]ta9 ! angul> position ( two or m objects 9 relation to ! position ( ! c5tre ( ! in/rum5t ^u :i* x is fix$2 also to obta9 relative altitude to ?is c5tre 9 relation to a di/ant /ation by ! read+ ( a divid$ measure or /aff plac$ !reon4 #df4--,! qualities desirable 9 a survey+ telescope are1 t suffici5t rays ( light may be collect$ f ! object obs]v$ = x to be cle>ly se5 z a :ole1 & 9 "s cases t suffici5t magnify+ p[] %\ld be available1 9 ord] t details or divisions pa9t$ ^u a /aff may be %>ply def9$4 ,! am\nt ( light receiv$ by ! eye :i* is effective 9 produc+ di/9ct vision is 9 proportion to ! ext5t ( active surface ( ! object-glass conv]g+ ! light rays4 ,! magnify+ p[] is regulat$ by ! sum ( ! convexities ( ! l5ses ( ! eye-piece ^u pr9ciples to be expla9$4 ,! survey+ telescope is requir$ to possess only a v limit$ field ( view1 b v great focal range1 s t objects may be se5 at any di/ance4 ,by ! necess>y optical arrangem5t ( ! telescope1 :i* w be fur!r describ$1 ! object obs]v$ is g5]ally inv]t$4 ,?is inv]sion ( ! image z x appe>s1 at fir/ pres5ts a little difficulty to ! le>n]1 b 9 practice ?is soon becomes s famili> z n to be ev5 recognis$ m5tally4 #dg4--,optical ,pr9ciples involv$ 9 ! ,telescope4--,to comm5ce ) ! optical con/ruction ( ! telescope1 t ?is may be ?or\ghly und]/ood1 x is necess>y to give brief details ( "s fir/ pr9ciples ^u :i* x is con/ruct$1 assum+ t optics h n be5 made a special subject ( /udy4 #dh4--,refraction ( ,glass4--,! prop]ties ( a l5s dep5d entirely ^u ! fact t a ray ( light pass+ f air obliquely into ! surface ( a d5se transp>5t m$ium 79 ?is case ( glass7 & equally f ! glass into air is b5t1 or1 z x is t]m$1 refract$1 to a c]ta9 angle at ! surface ( contact ( ! air & glass4 ,! ray ( light ent]+ ! glass is t]m$ ! incid5t ray1 t proce$+ f x ! em]g5t ray4 #di4--,!re is no kn[n m$ium1 glass or o!r1 :i* refracts a ray ( :ite light at "o uni=m angle4 ,! :ite ray is univ]sally sep>at$ ^u refraction1 or disp]s$1 z x is t]m$1 into rays ( all col\rs ( ! ra9b[4 ,9 consid]+ refraction1 !re=e1 9 its simple/ aspect we are compell$ to take ! refraction ( "o uni=m ray :i* is di/+ui%$ by "o col\r1 t =ms a "p ( ! :ite ray1 z = in/ance ! r$1 yell[1 gre51 or blue1 t is1 a mono*romatic ray1 z x is t]m$1 :i* gives a %>p refraction ( its own col\r$ light only 9 its ray4 ,inc&esc5t soda produces mono*romatic rays1 b 9 practice an int5se flame beh9d a bright-col\r$ glass w answ] ! same purpose1 z ! col\r$ glass may be arrang$ to absorb all1 or ne>ly all1 p>ts ( ! :ite ray1 except t ( its own col\r4 #ej4--;,e transp>5t m$ium has a special quality ( refraction4 ,!re=e1 diff]5t k9ds ( glass refract 9 diff]5t degrees )9 c]ta9 limit$ angles :i* w be h]eaft] consid]$4 ,! refraction is uni=mly 9 ! plane conta9+ ! incid5t ray1 & ! p]p5dicul> to ! surface sep>at+ ! two m$ia4 ,e m$ium refracts mono*romatic light equally accord+ to ! foll[+ law = any angle ( refraction3-- ,:atev] ! obliquity ( ! incid5t ray may be1 :5 x passes f a r>] to a d5s] m$ium ! ratio :i* ! s9e ( ! angle ( incid5ce be>s to ! s9e ( ! angle ( refraction is con/ant = any two transp>5t m$ia4 #ea4--,! natural law by :i* ! p[] ( refraction ( any m$ium may be %[n1 & consequ5tly ! magnify+ p[] ( a l5s 9 ! ratio ( its curvative ?r\gh ?is refraction may be exemplifi$1 is illu/rat$ by ! diagram on ! foll[+ page 7,fig4 #a74 ,,pp1 a l9e p]p5dicul> to ! surface ( ! plane ( ! m$ium 7glass7 ) air above x1 a ray ( light w\ld pass directly ,p to ,p ?r\gh ! glass surface ,,ss )\t refraction1 & s = all p]p5dicul> incid5ces or em]g5ces4 ,by ?is p]p5dicul> l9e ,,pp1 t]m$ ! normal1 all refractions are measur$4 ,! incid5t ray ,i to ,c is refract$ to ,r4 ,!n if we call ! angle ,,icp ,i1 & ! angle ,,rcp ,r1 x is f\nd by exp]im5t t ! p]p5dicul> f ,i on ,,pp 7or s9 ,i7 be>s a c]ta9 proportion to ! p]p5dicul> f ,r on ,,pp 7or s9 ,r7 accord+ to ! d5sity ( ! glass4 ,?is proportion is g5]ally express$ by ! =mula--s9 ,i s9 ,r4 ,ano!r incid5t ray ,i to ,c w\ld be refract$ to ,r1 & us+ simil> notation to ! above we h s9 ,i s9 ,r1 & f ?is x foll[s t 7s9 ,i7_/7s9 ,r7 7s9 ,i7_/7s9 ,r7 1 :i* is call$ ! index ( refraction4 ,?us1 if 9 a c]ta9 glass ! s9e ( ,i measure #c equal p>ts on any scale ( l5g?1 & ! s9e ,r #b p>ts on ! same scale1 ! index ( refraction ( ?is glass w\ld be #c divid$ by #b or #ae4 ,illu/ration3 ,fig4 #a4--;,diagram ( ,refraction & ,reflection4 ,if ! above process be rev]s$1 & ! ray ( light ,r be refract$ on pass+ f ! glass to ! air1 x w be project$ to ,i 9 ! em]g5t ray1 & foll[ ! same law z t giv5 above4 #eb4--,limit ( ,refraction--,reflection4--,! s9es to ! angles ,,icp & ,i,,cp be+ con/antly great] 9 proportion to ! obliquity 9 ! case ( glass we are consid]+ by #a_/c ?an ! s9e ( ! angles ,,rcp & ,r,,cp ( ! rays ( incid5ce ?r[n upw>d ^u ! surface ,,ss1 x w be se5 t at a c]ta9 angle or t 9 :i* ! s9e is #b_/c ! radius1 namely1 #da #dh #cg1 ! equation giv5 above makes s9 ,i #a its maximum value2 !re=e1 at any angle ( incid5ce great] ?an ?is1 ! s9e ( refraction to cont9ue 9 proportion w\ld exce$ ! radius--an impossibility4 ,! refraction1 if possible1 w\ld c>ry ! ray into ! sub/ance ( ! glass4 ,?is is !re=e call$ ! critical angle or angle ( total reflection4 ,at ?is po9t we may consid] :at mu/ happ54 ,by our rule1 refraction mu/ cease at ! angle refraction becomes impossible by increase ( s9e1 & z light _c be ext+ui%$ 9 a transp>5t m$ium x mu/ be reflect$4 ,?us ! ray r _c be refract$ 9 ! proportion accord+ to ! rule giv5 = s9e ,i to s9e ,r1 z ?is w\ld exce$ ! greate/ s9e1 t is ,,sc ! radius1 ?is ray w !re=e be reflect$ at ! surface f ! po9t ,c1 & pass 9 ! direction r4 ,?is prop]ty ( refraction1 cont9u+1 z x 71 into reflection1 is made use ( 9 _m in/rum5ts4 #ec4--;,x may be wor?y ( repeat+1 z x is a mi/ake occasionally made by p]sons design+ in/rum5ts = special purposes 7z telemet]s71 t ! refractions are n equal = v>y+ angles ( incid5ce1 b only1 z be=e /at$1 9 ! ratio ( ! s9es4 ,?us !re is no refraction ,p to ,p a c]ta9 refraction ,i to ,r1 & a great] refraction ,i to ,r1 ! refraction con/antly increas+ ) ! angle ( incid5ce4 #ed4--,! ,reflection ( ,light foll[s a v simple law1 viz43--,! angle ( reflection ( a ray ( light f a reflect+ surface is equal & opposite to ! angle ( incid5ce ^u x4 ,?us1 9 ,fig4 #b1 let a ray ( light ,,ia fall ^u ! reflect+ surface ,,ss at #cj ( incl9ation to ?is surface1 !n ?is ray w be reflect$ f ,a to ,r at ! angle ,,ras1 :i* is also #cj4 ,if an object be at ,o1 & ! eye at ,i1 !n ! object w appe> z ?\gh x 7 at ,o1 z ! eye only recognises ! object 9 ! direction f :i* x actually receives ! light4 ,! app>5t angle ,s,,ao is equal to ,,ias1 s t ! po9t ( a mirror f :i* an object reflect$ is receiv$ is 9 direct l9e betwe5 ! eye & ! app>5t object4 ,?is obs]vation w be f\nd useful 9 plac+ mirrors4 ,illu/ration3 ,fig4 #b4--;,diagram reflections f a plane4 ,illu/ration3 ,fig4 #c4--,reflection f a prism4 #ee4--,prismatic ,reflection4 ,! same law z giv5 above applies to int]nal reflection f glass4 ,let ,fig4 #c repres5t ! section ( a prism ff1 two pla9 surfaces ( glass at "r angles to ea* o!r1 & ! ?ird side mak+ an angle ( #de ) ea* ( ! o!r two4 ,! ray i w !re=e pass p]p5dicul>ly ?r\gh ! plane f )\t refraction to meet ! plane #de & ! angle ( reflection1 be+ equal to ! angle ( incid5ce1 w leave ?is plane at #de1 & rea* r4 ,! angle ( glass "h giv5 ( #de be+ great] ?an #da #di1 its extreme angle ( refraction1 ! int]nal reflection w be !re=e p]fect4 #ef4--,prismatic ,reflection1 z ?is is t]m$1 is l>gely us$ 9 optics 9 pref]5ce1 :]e practicable1 to op5 reflect+ surfaces1 f ! c]ta9ty ( keep+ ! reflect+ surface clean2 z dirt ext]ior to ! reflect+ surface ( ! prism does n affect ! int]nal reflection 9 any degree4 #eg4--,! reflection is %[n = cle>ness f ! plane 7,fig4 #b7 z x actually occurs1 or z x is measurable1 indep5d5t ( !ory4 ,9 optics x is f\nd mu* m conv5i5t to take ! reflection 9 relation to an imag9>y l9e drawn p]p5dicul> to ! plane4 ,9 ,fig4 #d ,,na is t]m$ ! normal4 ,tak+ ! angles z be=e z #cj to ! plane1 ! optical expression ( ?is w\ld be #fj to ! normal1 & ! reflection ( ! incid5t ray ,,ia to ,r w\ld be 9 ! angle ,,i> #fj #fj #abj1 ! am\nt ! incid5t ray is deflect$ f its =m] c\rse4 ,?is pr9ciple is important to be und]/ood 9 ! con/ruction ( ! sextant & o!r reflect+ in/rum5ts4 ,9 reflection ! ray is f\nd to foll[ ! %orte/ pa?1--t is1 ! pa? ,i to ,r by reflection is %ort] 9 ! l9es ,,i>1 plac$ at equal angles to ! normal1 ?an x w\ld be by any o!r possible pa?4 ,z1 = in/ance1 x is %ort] ?an ,ia,r1 %[n by dott$ l9es4 ,illu/ration3 ,fig4 #d4--,measurem5t ( angle ( reflection 9 optics4 ,illu/ration3 ,fig4 #e4--;,diagram illu/rat+ ! pr9ciple ( ! l5s4 #eh4--,passage ( a ,ray ( ,light ?r\gh a ,prism or a ,l5s--,convex ,refraction4 ,if we compreh5d ! law ( refraction exemplifi$ above1 art4 #ea1 ! pa? ( a mono*romatic ray ?r\gh a prism or a l5s is easily det]m9$1 tak+ into consid]ation ! refraction index ( ! glass4 ,9 ,fig4 #e let aa be ! base ( an equilat]al prism1 :i* base may also repres5t ! axis ( a l5s l9e> or p>allel ) ! direction f ! c5tre ( ! eye to ,o4 ,n[1 if a ray ( light pass f a small lum9\s object at ,o 9 ! pa? a to ! prism1 we may assume all o!r p>ts ( ! prism cov]$1 & ! refraction ( ! glass be su* t ! ray w pass ?r\gh x f ?is position 9 a horizontal direction1 or t p>allel to ! assum$ axis aa1 !n ! same ray w pass ?r\gh ! prism to equal di/ance f ! c5tre ( ! prism1--t is1 to ! position ( ! eye %[n by ! ray cont9u+ 9 ! pa? a1 ! angles to or f ! prism be+ equal2 s t if we cov] up all p>ts ( ?is prism except a l9e p>allel ) its base jo9+ ! ends ( ! l9es aa1 :]e x is %[n pass+ ?r\gh ! prism1 any ray ( light f ,o1 "u ! conditions giv51 w appe> z a spot ( light on ! plane p>allel to ! base ( ! prism2 or if we place our eye at ! position %[n1 we %all see ! image ( ! light ,o4 ,if we take a prism ( ! same k9d ( glass1 b ( less angle1 ^: base is bb1 ! refraction w\ld !n be less 7t is 9 ! ratio ( ! s9es71 t is if ! ray pass ?r\gh ! prism at less di/ance f ! base1 s t ! ray ,ob w\ld pass ?r\gh horizontally z be=e1 & em]ge f ! prism 9 ! pa? b1 also ) equally less refraction1 s t ! ray w\ld rea* ! eye at ! same po9t z ! m refract$ ray4 ,9 l mann]1 if ! prism 7 ( /ill less angle ) base cc & pass ?r\gh ! prism at a l[] position1 ! refraction w\ld be proportionally less1 & !re=e rea* ! eye at ! same po9t4 #ei4--;,if we take ! half l5s %[n 9 section 9 ! figure1 ?is may be consid]$ to t\* ! surface ( ! prisms describ$ tang5tially 9 ! l9es aa1 bb1 & cc1 :]e ! angles ( contact ( ,o1 a1 b1 or c ^u ! prism w\ld be equal to ^? ^u ! l5s = an inf9itely small ext5t ( surface4 ,!re=e1 if we make ! l5s ( su* =m t a ray ( light may pass f any s+le po9t ^u ! l9e ( its axis1 & be refract$ by e po9t ( ! surface ( ! l5s to a s+le po9t or focus on ! opposite side ( ! axis1 su* =m w\ld be a p]fect l5s4 ,= simplicity ( demon/ration ! refractions giv5 above are made p>allel ) ! axis ( ! l5s4 ,?is p>allelism c\ld only occur ) ! object & ! eye at equal di/ance f ! c5tre ( ! l5s1 & ) ?is di/ance also proportional to ! am\nt ( refraction ( ! glass us$ 9 ! con/ruction4 ,if ! rays 7 all p>allel to ea* o!r ^u incid5ce !y w\ld /ill be b5t 9 ! same ratio 7to ! s9es ( ! angles ( contact & dep>ture71 & ?is w\ld br+ ! focus ne>] to ! glass2 b x is evid5t ! same pr9ciples w\ld hold4 #fj4--;,z reg>ds ! action ( ! eye 9 ?is matt]1 x c only recognise ! direction f :i* x receives ! light1 & n ! processes ! rays may h und]gone be=e rea*+ x4 ,!re=e ! ray proce$+ f ,o 9 ! pa? b1 pass+ ?r\gh ! l5s or prism & em]g+ 9 ! pa? b1 is recognis$ by ! eye z ! ray b only4 ,s t ! po9t ( light ,o appe>s visually z proce$+ f ! direction bs1 & ?is conv]g5ce or expansion ( ! po9t ,o1 ) its co9cid5ce f ! opposite side ( ! l5s1 produces ! effect ( magnification ( ! object repres5t$ by ,o4 #fa4--;,concave ,refraction4--,9 ,fig4 #f a convex l5s is %[n 9 :i* ! p>allel rays ,l are drawn to a focus at ,f ^u ! pr9ciples j demon/rat$4 ,if ! l5s 7 made concave1 z %[n 9 section ,fig4 #g1 by ! same pr9ciples ( refraction1 x is evid5t t ! rays w\ld div]ge1 z ! refraction b5ds ! ray uni=mly t[>ds ! ?icke/ section ( ! glass4 ,if two l5ses are br\ght toge!r1 "o ) convex face1 & "o ( ! same radius ( curvature1 b ) concave face1 ! rays 9 pass+ ?r\gh w\ld n be refract$4 ,9 ?is case ! l5s w\ld be said to be correct$4 ,a convex l5s has a focus :]e ! rays conv]ge4 ,a concave l5s is said to h a negative focus equal to ! focus ( ! convex l5s1 t w correct x1 or make x equal1 z reg>ds refraction1 to plane p>allel glass4 ,illu/ration3 ,fig4 #f4--;,diagram convex l5s4 ,illu/ration3 ,fig4 #g4--;,diagram concave l5s4 #fb4--,sph]ical ,ab]ration4--,if ! surfaces ( convex l5ses are truly sph]ical1 x is f\nd1 by an analysis too complex to be describ$ 9 ?is "w1 t ! rays :i* pass ?r\gh at diff]5t di/ances f ! axis conv]ge to slightly diff]5t po9ts ( di/ance4 ,?is subject 0 at "o "t s]i\sly discuss$ = ! prop] =mation ( objectives = telescopes2 b at pres5t x is entirely neglect$ by ! optician1 z x is f\nd practically to be z difficult to make a l5s truly sph]ical z "o ( ! conv]g5t or div]g5t =m requir$ "u ! special conditions pres5t4 ,! sph]ical =m1 z x is approximately produc$ f ! gr9d+ ) sph]ical tools1 be+ always ne>ly correct1 ! correct =ms ( object-glasses are made by figur+1 :i* has be5 already ref]r$ to1 art4 #ch4 ,9 eye-pieces ! sph]ical ab]ration w\ld cause "s confusion 7 ! glasses n adju/$ 9 su* a mann] z l>gely to prev5t ?is4 #fc4--,! ,=mation ( ,images by ,refraction f a ,convex ,l5s4--,if we take any d\ble convex l5s1 z t %[n 9 section ,fig4 #f1 we f9d1 if x is held t[>ds ! sun at a c]ta9 di/ance f a solid surface1 we =m a burn+-glass1--t is1 we produce an image ( ! sun :]e 8 rays ( light & heat are refract$ by ! :ole ( ! surfaces ( ! glass4 ,! di/ance f ! c5tre ( ! l5s to ! po9t ( greate/ light is call$ ! sol> focus ( ! l5s1--t is1 ! po9t at :i* x conc5trates or conv]ges p>allel rays1 & =ms ! image ( ! sun4 ,) p>allel rays f ! sun1 ! di/ance ( focus is less ?an if ^! rays 7 div]g5t 9 any degree4 ,consequ5tly ! sol> focus is less ?an t subt5d$ by any object on ! e>?4 ,illu/ration3 ,fig4 #h4--;,diagram ( ! conv]g5ce ( rays ( light4 #fd4--;,9 ! diagram1 ,fig4 #h1 a c&le-flame at acb =ms its focus at acb1 :]e all rays conv]ge to =m an image 9 ! foll[+ mann]3--,e po9t ( ! c&le ?r[s its light ^u e po9t ( ! surface ( ! l5s1 &1 !re=e1 ?r[s ! image ( ea* po9t to its focal position beh9d ! l5s1 accord+ to ! direction ( its refractions2 s t1 if we take all ! sep>ate po9ts ( light ?r[n f ! c&le1 we !n h a p]fect image ( x =m$ by an inf9ite numb] ( sep>ate focal po9ts1 & z ! rays by _! direction necess>ily cross ov] ! axis ! image is 9 an inv]t$ position4 #fe4--,! :ole ( ^! l9es w\ld =m a confusion if %[n 9 a diagram4 ,we may1 !re=e1 take = illu/ration ! ext]ior ( a cone ( rays proce$+ f ?ree po9ts only4 ,?us ! cle> l9es aa & aa f ! po9t ( ! flame w\ld refract to ! l[] "p ( ! image a4 ,! dott$ l9es bb w\ld proce$ to ! upp] "p ( ! image1 z %[n by ! cont9uation ( ! dott$ l9es to b1 :]eas ! c5tral da% l9es cc w\ld =m _! images 9 ! c5tre foll[+ ! da% l9es to c1 & ?us1 f ! numb] ( lum9\s po9ts1 ! :ole image ( ! c&le w\ld be produc$ at ! foci bca 9 an inv]t$ position4 #ff4--;,disp]sion ( ,light4--,! conditions /at$ above = refraction ( mono*romatic light w\ld n answ] = p]fect vision1 :i* is only possible 9 cle> :ite light4 ,x !re=e becomes necess>y 9 practice to correct ! quality ( disp]sion :i* light suff]s 9 refraction ?r\gh any d5se m$ium4 ,! evid5ce ( disp]sion by glass may be %[n by a prism1 z 9 ! foll[+ diagram3-- ,illu/ration3 ,fig4 #i4--;,diagram %[+ *romatism ( light by ! prism4 #fg4--;,9 ,fig4 #i let ,p repres5t ! section ( a prism ( glass1 cov]$ except at ! n>r[ op5+ a4 ,let a /rong light1 z %[n1 be cov]$1 except f a n>r[ slit1 !n ! ray f ! light1 refract$ f a t[>ds a 9 ! prism1 w be disp]s$ or split up at a into ! col\rs ( ! ra9b[1 %ad+ f blue1 gre51 & yell[1 to r$1 )9 ! prism4 ,^u em]g5t refraction at a ?is disp]sion w increase s t an image ( ! slot ne> ! light1 if ?r[n on a plane proce$+ f ! base ( ! prism to ! "r1 w be repres5t$ at ,,bgr by a prismatic or *romatic spectrum1 z x is t]m$1 %ad+ (f f blue to gre51 yell[1 r$4 #fh4--;,a*romatism ( ! ,prism 9 ! same ,quality ( ,glass4--,tak+ ! prism1 ,fig4 #aj1 ,c z be=e1 & apply+ a second exactly simil> prism ,c rev]s$ ^u ! face ( ! fir/--!n at e "p ( ! process ( disp]sion f a po9t ( :ite light "u diffraction into ! fir/ prism1 w by equal diffraction1 9 pass+ ?r\gh ! second prism1 be br\ght to a po9t1 :]e x w issue a :ite ray at ! po9t a1 z x ent]$ at ! po9t a2 or1 practically1 ! em]g5t ray w be a*romatis$4 ,?is pr9ciple mu/ be foll[$ 9 ! manufacture ( a*romatic l5ses1 al?\gh "u v>i\s indices ( refraction & disp]sion f diff]5ces 9 qualities ( glasses4 ,x is made use ( 9 ! a*romatism ( eye-pieces1 & 9 comb9ations1 & assures ! a*romatism ( p>allel glasses us$ = sextants "u diff]5t angles ( incid5ce4 ,illu/ration3 ,fig4 #aj4--;,diagram p]fect a*romatism4 #fi4--,! ,a*romatic ,l5s4--,! a*romatism ( a pair ( l5ses by :i* a l>ge am\nt ( refraction ( pure :ite light is obta9$1 dep5ds ^u diff]5ces 9 ! qualities ( glasses :i* are due to _! d5sity & *emical composition1 s t 9 "o glass a less am\nt ( disp]sion is produc$ at an angle :i* gives an equal am\nt ( refraction ?an 9 ano!r4 ,! comb9ations ( glasses 9 use are cr[n & fl9t1 z already describ$1 art4 #cb1 ! cr[n be+ a light glass ( soda & silica1 ! fl9t be+ a heavi] glass conta9+ silica1 pota%1 & lead4 ,9 a c]ta9 k9d ( fl9t glass us$ = optical purposes1 = a prism giv+ only slightly great] refraction ?an "o ( cr[n glass1 ! disp]sion is ab\t d\ble4 ,!re=e1 we may comb9e a pair ( glasses s z to obta9 a desir$ am\nt ( refraction f ! comb9ation if we make ! cr[n glass refract some?+ ov] d\ble ! am\nt we require = ! p]fect$ l5s or prism1 & dim9i% ?is quantity by ! rev]se refraction ( ! fl9t glass1 !reby correct+ ! disp]sion1 z may be %[n by ! diagram on ?is page4 #gj4--;,9 fig4 #aa let ,c be a prism ( cr[n glass giv+ ov] d\ble ! am\nt ( refraction to a prism ( fl9t glass ,f1 b only ( total disp]sion equal to ! ?ick] cr[n glass4 ,! comp\nd :ite ray ( light a w !n be disp]s$ ^u refraction at ! meet+ faces ( ! two prisms1 a c]ta9 quantity repres5t$ by ! cone ( rays %[n1 & aga9 conv]ge at a1 an equal quantity on em]g5ce f ! ext]ior surface ( ! fl9t prism1 s z to issue aga9 a :ite ray1 ( :i* ?is sy/em ( prisms has refract$1 b n disp]s$1 ! light4 ,illu/ration3 ,fig4 #aa4--,%[+ pr9ciples ( a*romatism4 #ga4--,t ! same pr9ciples giv5 above = ! prism w hold 9 ! a*romatic comp\nd l5s1 is already demon/rat$ by ! comp>ison ( l5ses & prisms %[n 9 ,fig4 #e2 b = ! sake ( cle>ness x may be aga9 %[n diagrammatically 9 ,fig4 #ab = an actual objective1 :]e9 ! p>allel rays ab1 proce$+ f a di/ant object or />1 are %[n refract$ to ab1 & com+ to a focus at ,f1 al?\gh disp]s$ at ! meet+ surfaces ( ! two glasses1 z %[n diagrammatically1 by ! int]nal cone ( rays4 ,illu/ration3 ,fig4 #ab4--,%[+ a*romatic objective4 #gb4--,practically1 ! matt] is n q s simple z x w\ld appe> to be !oretically1 by ! above-describ$ conditions1 z we actually f9d ! spectrum ( a prism ( fl9t glass ( equal disp]sion to "o ( cr[n glass does n give exactly simil> ext5t ( sep>ate col\rs )9 its spectrum1 ! m$ium ray ( ! spectrum 9 ! fl9t glass be+ ne>] ! blue ?an 9 ! cr[n4 ,?us1 ?is comp\nd l5s does n p]fectly correct by inv]sion z x does 9 ! p]fect case discuss$1 & %[n 9 ,fig4 #aj4 ,= ?is reason bett] def9ition is f\nd by slight displacem5t & slight diff]5ce ( total ext5t ( disp]sion ( "o ( ! spectra 9 co9cid5ce on ! meet+ planes betwe5 ! l5ses1 leav+ 9 all cases a c]ta9 am\nt ( residual col\r1 blue or r$1 uncorrect$1 by mak+ ! glass "u- or ov]-correct$1 z x is t]m$1 :i* does n1 h[ev]1 s]i\sly impair di/9ct vision4 ,x is q possible t1 by "s future improvem5ts 9 ! *emical con/itution ( ! glass1 ?is defect may be rem$i$4 ,engli% glass-work]s pref] to ov]-correct1 ,g]man & ,fr5* glasses are m (t5 "u-correct$4 #gc4--,! measurem5ts ( refraction & disp]sion be+ bo? 9 "o direction1 may be tak5 toge!r )9 c]ta9 angul> limits 9 "o t]m 9 ! con/ruction ( a l5s z ! ratio ( disp]sive p[]s1 ! indices be+ c]ta9 d>k l9es :i* are obs]v$ uni=mly 9 ! spectrum ( ! sun project$ f a n>r[ slit4 ,^! l9es or b&s 9 ! sun's spectrum are kn[n to be due to metallic vap\rs :i* are pres5t 9 8 atmosph]e1 & c !re=e be reproduc$ by ! deflagration ( l metals on a small scale4 ,to c]ta9 ( ^! l9es lett]s ( ! alphabet h be5 appli$4 ,( ^! lett]s1 a pair ( l9es due to sodium vap\r m>k$ ,d1 & ?ree l9es due to hydrog51 m>k$ ,c1 ,f & ,g1 are commonly tak5 = ref]5ce ( disp]sion4 ,a*romatism is g5]ally consid]$ duly correct$ :5 ! l9es ,c & ,g are unit$4 ,! middle ( ! spectrum betwe5 ^! l9es is ab\t ,e2 & *romatic disp]sion ( optical fl9t & cr[n may be tak5 to be fairly correct$ if ! spectra are co9cid5t 9 col\r at ?is l9e4 #gd4--;,curvatures 9 ! ,a*romatic ,l5s4--,a l>ge am\nt ( ma!matical p[] has be5 exp5d$ ^u ?is matt]1 b ! p]plexity ( ! subject is due to small diff]5ces ( ! mat]ial2 & ! impossibility ( work+ absolutely true sph]ical curves has r5d]$ ?is "w ( little practical value to ! optician1 :o /ill resorts to ! =mul ( ,dollond & ,tully4 ,^? :o c>e to foll[ ! subject beyond ! scope ( ?is "w w f9d num]\s pap]s 9 ! ,phil4 ,trans41 & 9 ! works ( ,h]s*el1 ,b>l[1 ,codd+ton1 ,rob9son1 & ,/okes1 :]e9 :at is kn[n !oretically ( ! subject is fully inve/igat$ & discuss$4 #ge4--;,= all small a*romatics1 su* z are employ$ 9 survey+ in/rum5ts ) ,*ance's h>d cr[n & d5se fl9t1 ! foll[+ approximate =mula is commonly employ$1 express$ 9 t]ms ( ! radius ( ! curv$ surface into f1 ! total focus ( ! f9i%$ objective1 = fir/ work+ be=e trial3-- #a/4--,outside surface1 f_/#b convex1 cr[n4 #bnd4--,inside f_/#c #crd4--,outside f_/#c concave1 fl9t4 #d?4--,inside #d;f convex1 #gf4--;,by diff]5t mak]s ! surfaces are *ang$ z f> z rev]s+ ! curvature ( ! front glass1 & inde$ v good glasses are made ) ! #a/1 #bnd & #crd 7f_/#be74 ,9 all cases true conv]g5ce ( ! :ite ray is only obta9$ by correction ( ! out] & inn] surfaces1 or by figur+1 z x is te*nically t]m$1 9 :i* ! curvature is n only made great] or less1 b its "* is alt]$ g5]ally 9 ! direction f circul> to elliptical section4 ,! qualities ( ! object-glass _c be ov]-e/imat$ by ! practical surveyor4 ,a heavy in/rum5t ) inf]ior object-glass may be c>ri$ ab\t = ye>s1 :]eas a light] in/rum5t ) good object-glass w\ld p]=m bett] "w4 ,excell5t in=mation ^u ?is subject 0 giv5 9 a lecture be=e ! ,royal ,in/itution by ! em95t optician1 ,sir ,h[>d ,grubb1 ( ,dubl94 #gg4--,optical ,arrangem5ts ( ! ,telescope4--,! e>lie/ =m ( telescope is t ( ,kepl]1 ,fig4 #ac4 ,9 ?is ! rays f ! object-glass cross 9 front ( ! eyeglass2 consequ5tly1 ! image is inv]t$4 ,?is =m is at pres5t little us$ except 9 comb9ation ) a sep>ate eye-piece4 ,illu/ration3 ,fig4 #ac4--,kepl]'s telescope4 ,illu/ration3 ,fig4 #ad4--;,galileo's telescope4 #gh4--;,galileo's ,telescope1 ,fig4 #ad4--;,9 ?is ! eye-piece is a concave glass4 ,?is glass is plac$ inside ! focal di/ance1 s t ! rays f ! object-glass are b5t to less conv]g5ce1 t !y may ent] ! pupil ( ! eye 9 a direction possible to rea* ! ret9a4 ,! image 9 ?is telescope is ma9ta9$ erect4 ,?is pr9ciple is us$ entirely = field & op]a glasses1 also = sextants & "s o!r in/rum5ts :]e x is desirable to keep ! image erect1 & small p[] is requir$1 suffici5t only to obta9 m di/9ct vision4 ,! l9es aa 9 ,figs4 #ac1 #ad are t]m$ ! axis ( ! telescope4 #gi4--,optical ,arrangem5t ( ! ,huyg5ian ,telescope4--,9 survey+ in/rum5ts1 :]e angles & directions are n tak5 by co9cid5ce ( direct & reflect$ images1 x is necess>y t ! direction ( ! axis ( ! telescope %\ld be cle>ly indicat$4 ,9 ?is case ! focus ( a di/ant object--t is1 its exact image--is project$ ^u a plane t]m$ ! diaphragm1 ,fig4 #ae1 ,,ss ^u :i* a visible object or index is plac$1 ! position ( :i* is pick$ up by a second>y telescopic arrangem5t1 or eye-piece z x is te*nically t]m$4 ,illu/ration3 ,fig4 #ae4--;,diagram ( arrangem5t ( l5ses4 #hj4--,! arrangem5t ( l5ses 9 a survey+ telescope is %[n 9 ! illu/ration above1 :]e ,,og is ! object-glass or objective1 ,e ! eye-glass1 ,f ! field-glass4 ,! two l5ses ,e & ,f1 9 _! m\nt+s1 =m ! eye-piece ,,ep4 ,! dott$ l9e a is ! axis ( ! telescope1 ,,ss is ! focal plane ( ! object-glass1 :]e a metal disc is plac$ ) an op5+ 9 its c5tre--?is is t]m$ ! diaphragm or te*nically1 ! index-/op4 ,across ! op5+ 9 ! disc1 spid]'s webs or o!r f9e visible objects are plac$1 to be describ$ fur!r on4 #ha4--;,bo? ! object-glass & ! eye-piece are fitt$ 9 slid+ tubes1 :i* w be describ$ pres5tly1 9 su* a mann] t !y may be made to approa* or rec$e f ! focal plane ,,ss4 ,! ne>e/ di/ance ( ! object-glass to ?is plane is ! sol> focus1 or ! di/ance at :i* a %>p image ( ! sun or a /> plac$ 9 ! axial l9e w\ld be =m$4 ,! greate/ di/ance ( ! object-glass f ! focal-plane 9 mo/ in/rum5ts is su* t a cle> image w be giv5 on ?is plane ,,ss ( an object plac$ at ab\t tw5ty feet f x4 #hb4--,! ,ramsd5 ,eye-piece1 ! optical arrangem5t ( :i* is %[n 9 ,fig4 #af1 is also kn[n z a positive eye-piece4 ,x consi/s ( two plano-convex l5ses1 ! convex surfaces ( :i* are turn$ t[>ds ea* o!r4 ,!y are sep>at$ by a di/ance equal to two-?irds ! focal l5g? ( ei!r glass1 & plac$ s t ! diaphragm is "o-f\r? ?is focal l5g? f ! field-glass4 #hc4--,?is eye-piece is consid]$ n to be q s a*romatic z ano!r =m kn[n z ! ,huyg5ian eye-piece1 b its sph]ical ab]ration is less ?an any o!r1 & x gives :at is necess>y 9 all measur+ in/rum5ts--a flat field ( view1 requir+ no *ange ( position to see ! c5tre & bord] ( ! field ) equal di/9ctness4 ,illu/ration3 ,fig4 #af4--,ramsd5 eye-piece4 #hd4--,! ,field ( ,view %\ld be z bright z possible4 ,to ensure ?is1 ! field ( ! object-glass :i* is tak5 by ! eye-piece at ! position ( ! front ( ! eye %\ld n be l>g] ?an ! pupil4 ,if ! :ole field ( light ent] ! eye z x %\ld d1 ! brightness w !n v>y directly z ! squ>e ( ! diamet] ( ! object-glass1 & inv]sely z ! squ>e ( ! magnify+ p[]4 ,! directions ( ! rays are %[n by dott$ l9es z aa & aa = ! ,ramsd5 eye-piece 9 ,fig4 #af4 ,?is eye-piece is sometimes call$ an inv]t+ eye-piece4 ,x is n really s3 ! object-glass inv]ts its image & ! eye-piece picks up ! image 9 its inv]t$ position4 ,two or ?ree eye-pieces ( ?is k9d1 ( diff]5t magnify+ p[]s1 are sometimes suppli$ ) "o survey+ in/rum5t4 ,! same =m ( eye-piece1 be+ also a simple microscope1 is us$ to read ! divisions on ! divid$ circles ( !odolites1 sextants1 & o!r in/rum5ts1 & = su* purposes x is (t5 desirable to asc]ta9 its focal l5g?4 #he4--,! ,focal ,l5g? ( ! positive or ,ramsd5 eye-piece is f\nd by divid+ ! product ( ! focal l5g?s ( ! two l5ses by _! sum1 dim9i%$ by ! di/ance betwe5 !m4 ,?us1 if ! focal l5g? ( ea* ( ! l5ses be #ae in*es1 ! di/ance betwe5 !m #a in*3-- 7#ae #ae7_/7c - #a7 #aabe in*es4 #hf4--,! ,magnify+ ,p[] ( ! ,telescope4--,! focal l5g? ( ! objective divid$ by t ( ! eye-piece gives ! p[] ( ! telescope4 ,?us1 a #ad-;in* telescope ) ! above eye-piece w\ld h a p[]1 #ad_/aabe #abddd1 or #ab ne>ly1 a v g5]al l[] p[] eye-piece ) telescopes ( ?is focus4 ,illu/ration3 ,fig4 #ag4--;,dynamet]4 #hg4--;,dynamet]4--,! magnify+ p[] ( a telescope may be asc]ta9$1 )\t any k ( ! focus ( ! glasses us$ 9 its con/ruction1 by ! use ( a dynamet]4 ,?is in/rum5t1 ,fig4 #ag1 consi/s ( a comp\nd microscope 9 :i* a f9ely divid$ transp>5t scale is plac$ 9 ! mutual focus ( its object-glass & ( ! eye-piece at a4 ,! divisions ( ! scale may be #ja1 #jb1 or #jja in*es ap>t1 adju/$ s t a disc #a in* diamet] at ! ext]ior focus ( ! eye-piece may read a giv5 quantity ^u ! scale4 ,to use ?is app>atus1 ! flang$ face is plac$ 9 front ( ! eye-piece ( ! telescope1 previ\sly set at sol> focus4 ,! telescope ?r[s a circul> image ( its object-glass ?r\gh ! eye-piece1 :]e x is pick$ up by ! object-glass ( ! dynamet] & br\ght to focus on ! scale a1 :]e x appe>s z a circul> disc ( light4 ,if ?is image be measur$ by ! scale1 & ! diamet] ( ! object-glass be divid$ by ?is measure1 ! quoti5t w be ! magnify+ p[] ( ! telescope4 ,!re are sev]al o!r =ms ( dynamet]4 #hh4--,! ,erect+ ,eye-piece1 sometimes suppli$ ) !odolites & occasionally ) o!r in/rum5ts1 is ! ord9>y "o ( ! common telescope1 ,fig4 #ah4 ,! glasses are s arrang$ t ! image br\ght to ! focus ( ! telescope inv]t$ is aga9 erect$1 s t objects appe> 9 _! natural position4 ,! complete eye-piece is ( ! same optical arrangem5t z t ( a comp\nd microscope4 ,! arrangem5t ( l5ses is %[n 9 ! engrav+ on next page4 ,illu/ration3 ,fig4 #ah4--,optical arrangem5t ( erect+ eye-piece4 #hi4--;,a object l5s1 ,b amplify+ l5s1 ,c field l5s1 ,d eye l5s4 ,/ops are plac$ at d & d to cut out extreme rays4 ,! image is =m$ by ! objective at ,o1 & ! light passes 9 ! direction %[n by f9e l9es1 be+ ?r[n f side to side ( ! l5ses4 ,! ray is a*romatis$ proportionally to its disp]sion by ! sep>ate l5ses1 ^u pr9ciples discuss$ art4 #fh & %[n ,fig4 #aj1 z indep5d5tly ( ! small am\nt ( opacity ( ! l5ses1 extreme rays are cut (f1 s t c5tral portions only are us$4 ,?is eye-piece suff]s loss ( light at ea* ( ! f\r l5ses2 !re=e1 a telescope ) x1 = equally di/9ct vision to t obta9$ by us+ ! ,ramsd5 eye-piece previ\sly describ$1 w\ld require a l>g] objective4 ,?is eye-piece is r>ely us$ n[1 except+ ) ,am]ican in/rum5ts 9 :i* !y are almo/ univ]sal1 z ! v slight advantage ( see+ ! image erect is f> outweigh$ by ! loss ( light x entails4 ,! ,am]ican manufactur]s place !m inside ! telescope in/ead ( outside1 ?us ! telescopes look mu* ! same z our ord9>y ones1 b ! focal l5g? ( ! object-glass is %ort5$ by ! l5g? ( ! eye-piece1 & z ?is takes up f ?ree to f\r in*es1 a telescope :i* w\ld appe> to be say #aj in*es sol> focus is1 9 reality1 only six or sev5 in*es & consequ5tly only ab\t two-?irds ! p[]4 ,illu/ration3 ,fig4 #ai4--;,diagonal eye-piece1 full size2 ,s ,g sun-glass4 ,x is a/oni%+ t ! ,am]icans1 :o are usually s quick 9 adopt+ ! mo/ practical appliances1 are s sl[ 9 see+ ! advantage ga9$ by ! use ( ! n[ almo/ univ]sal inv]t+ eye-piece4 #ij4--,! ,diagonal ,eye-piece1 ,fig4 #ai1 is us$ ^u transit in/rum5ts1 !odolites1 & occasionally ^u m9+-dials4 ,x p]mits ! telescope to be us$ by ! obs]v] look+ at "r angles to its axis4 ,?us1 by ! natural direction ( ! eye1 />s or ! sun may be obs]v$ to ne> ! z5i?1 or ! direction ( a l9e cut by two lights at ! bottom ( a %aft may be obs]v$ f above by ! telescope ( a !odolite hav+ a holl[ c5tre on its ord9>y /&1 to *eck ! magnetic be>+ ( ! ne$le bel[ gr\nd1 if ?is is assum$ to be subject to local di/urbance4 ,! socket ( ?is eye-piece screws ^u ! telescope & has a free inn] tube = rotation1 s t ! #ij to ! axis ( ! telescope may be plac$ at any angle to ! axis ( its cyl9drical circumf]5ce2 z1 = in/ance1 in/ead ( be+ us$ v]tically or = z5i? />s1 x may be us$ horizontally1 :]e precipit\s gr\nd w\ld n p]mit direct axial vision ?r\gh ! telescope4 ,! reflect+ arrangem5t ( ?is eye-piece may be adapt$ ei!r to ! ,ramsd5 or ! erect+ =m4 ,9 ei!r case ! reflector is plac$ 9 ! c5tral portion ( ! eye-piece4 ,9 survey+ in/rum5ts ! reflector is g5]ally a piece ( poli%$ speculum metal = portable in/rum5ts1 b a prism ( glass = l>g] fix$ in/rum5ts4 ,! g5]al arrangem5t is %[n 9 ! section ( a diagonal ,ramsd5 eye-piece on page #db1 full size4 ,a object l5s1 ,d eye l5s1 adju/able = di/ance f ! reflector ,r1 ,s out] cas+ :i* p]mits adju/m5t = focus+1 ,,sg sun glass1 ! diaphragm be+ 9 front ( ,a4 #ia4--,:5 a rectangul> prism is us$ = ! reflector1 x is work$ ) "o plane #de1 z previ\sly discuss$1 art4 #ee1 ,fig4 #c4 ,9 place ( "o or bo? ! #ij faces ^! surfaces are sometimes work$ convex s z to =m a magnifi]1 disp5s+ ) "o ( ! convex l5ses ( ! eye-piece4 ,a long diagonal eye-piece is necess>y1 :]e />s t[>ds ! z5i? are to be obs]v$1 to prev5t int]f]5ce ( ! limb ( a !odolite ) ! face ( ! obs]v]4 #ib4--,reflect+ ,eye-piece is us$ to obs]ve small />s1 z = in/ance ! circumpol> />s 9 ! s\!rn hemisph]e1 by illum9at+ ! front ( ! webs or l9es4 ,a /rong light ?r[n d[n ! telescope f a reflector to illum9ate ! webs w\ld t5d to dim ! effect ( blackness ( ! sky & r5d] ^! />s indi/9ct4 ,9 ! eye-piece1 ,fig4 #bj1 a piece ( pla9 p>allel glass is plac$ at an angle ( #de to ! axis4 ,?is p]mits ! webs to be cle>ly obs]v$ ?r\gh ! glass at ! same "t t x ?r[s light f a lamp plac$ at a di/ance f ! glaz$ ap]ture ,l by reflection ( ! surface ( ,r suffici5t = front illum9ation4 ,! am\nt ( light requir$ is regulat$ by ! di/ance ( ! lamp f ,l4 ,?is eye-piece is made to fit into ! diagonal eye-piece cas+1 z ,s ,fig4 #ai1 ,e ,fig4 #bj be+ ! position ( ! eye1 ,f field-l5s4 ,illu/ration3 ,fig4 #bj4--,reflector 9 eye-piece to illum9ate ! front ( diaphragm4 #ic4--,sun-glass4--,sextants & !odolites are suppli$ ) a v d>k glass or a comb9ation ( d>k glasses fix$ 9 a rim to =m an eye-piece front1 :i* screws or fits on 9 front ( any eye-piece1 to take obs]vations ( ! sun = longitude or be>+1 ,fig4 #ai1 ,,sg4 ,x ne$s no description1 b is necess>y to be m5tion$ to complete ! optical arrangem5ts ( a telescope1 z x is sometimes us$ = survey+ purposes4 #id4--,! ,body ( a ,telescope t =ms "p ( a survey+ in/rum5t is con/ruct$ ( a pair ( triblet drawn tubes1 ,fig4 #ba1 ,,tt ,t4 ,^! tubes %\ld be truly cyl9drical & /raight1 s z to fit smoo?ly toge!r1 ! "o )9 ! o!r1 & slide 9 & out q freely b )\t any play4 ,! inn] tube %\ld be z long z practicable1 s z to rema9 /eady :5 rack$ out to ! full ext5t requir$ to focus ne> objects4 ,! object-end ,r is g5]ally enl>g$ s z to take ! cell 9 :i* ! objective ,o is plac$1 )\t cutt+ (f any "p ( ! light1 or entail+ ! weight ( l>g] tubes ?an is necess>y to make use ( ! full field ( ! objective4 ,! objective is g5]ally held 9 its cell by an int]nally fitt+ screw$ r+ ) mill$ edge1 s t ! glasses may be tak5 out & sep>at$ to be clean$1 & be easily replac$4 ,two not*es or grooves are commonly made 9 ! edges ( ! glasses1 ea* ( :i* is deep en\gh to take a small brass p9 :i* is sold]$ to ! inside ( ! cell4 ,! second not* indicates relative position1 s z to secure ! glasses be+ replac$ prop]ly4 ,9 all cases ! d\ble convex cr[n glass is plac$ outw>ds f ! telescope4 ,a glass ( l>ge size %\ld h a loose r+ )9 ! cell to act z a spr+ to save di/ortion ( ! objective f expansion or contraction ( ! metal2 b ?is is n necess>y 9 small survey+ in/rum5ts4 ,9 "s common telescopes ! object-glass is burni%$ into its cell1 9 :i* case ! glasses ( ! objective _c be sep>at$ = clean+4 ,illu/ration3 ,fig4 #ba4--;,body ( survey+ telescope4 ,illu/ration3 ,fig4 #bb4--,section ,fig4 #ba1 ,a to ,b4 #ie4--,/ops4--,)9 ! inn] tube two or m ?9 metal r+s1 t]m$ te*nically /ops ,,ss & ,s,s1 are plac$ to cut (f any extrane\s light t may ent] ! telescope obliquely1 & :i*1 if n /opp$ (f1 w\ld produce a fogg9ess ov] ! :ole field ( view4 ,x is important t ^! /ops %\ld n cut out any "p ( ! full ap]ture ( ! object-glass if x be a good "o4 ,9 ! manufacture ( ! telescope ?is is easily se5 by look+ 9 at ! eye-piece ( ! unglaz$ telescope to see if ! /ops cle> ! objective cell4 ,9 ! f9i%$ glaz$ telescope ano!r me?od w be discuss$ fur!r on4 #if4--,! inn] or ! out] tube ( ! body ( ! telescope slides t[>ds or f ! objective = focuss+ by means ( a rack ,r & p9ion ,p4 ,! rack is sold]$ to ! inn] tube1 & ! p9ion fitt$ 9 a cock-piece1 z %[n ,fig4 #bb ,c1 on ! out] tube4 ,! p9ion is mov$ by a l>ge mill$ head ,m4 ,?is fitt+ %\ld be made ) c>e4 ,! p9ion %\ld be v free1 s t x does n lift ! body at any too?1 & at ! same "t !re %\ld be no %ake on ! ge>+4 ,x ne$s consid]able practice to rack a telescope prop]ly4 #ig4--,! outw>d "p ( ! object end ( ! telescope is g5]ally turn$ to fit ! int]ior ( a sep>ate %ort tube1 %[n at ,r1 :i* is plac$ ov] x4 ,! out] end is clos$ by a r+ to ! size ( ! ap]ture ( ! objective4 ,?is is t]m$ a ray-%ade or sometimes a dew-cap4 ,! ray-%ade is ext5d$ :5 ! telescope is direct$ to su* an angle t ! sun's rays w\ld fall ^u any "p ( ! objective1 & !reby cause int]nal reflections4 ,a swivel %utt]1 ,fig4 #ba1 ,r1 is plac$ ^u ! outw>d end ( ! ray-%ade1 :i*1 :5 clos$1 z %[n 9 ! cut1 =ms a cap to ! telescope4 ,! eye-piece ,,ep be=e describ$1 art4 #hb1 ,fig4 #af1 is plac$ 9 a tube con/ruct$ ^u ! end ( ! telescope1 9 :i* x slides freely1 to focus ^u ! diaphragm to be pres5tly describ$4 ,! telescope is m\nt$ sometimes solidly ^u a transv]se axis1 or x is m\nt$ 9 turn$ be>+s1 or x has two coll>s plac$ r\nd x :i* are turn$ q equal & true1 & are m\nt$ on ,y's to be h]eaft] describ$4 #ih4--,me*anical ,adju/m5t ( ! ,eye-piece4--,9 "s l>ge in/rum5ts ! eye-pieces are rack$ = adju/m5t 9 ! same mann] z ! object-glass already describ$4 ,a bett] plan is to h an inn] tube to ! socket tube cut ) a screw into ?is1 & provid$ ) a mill$ edge1 s t ! eye-piece may be screw$ g5tly to focus ^u ! webs ( ! diaphragm4 ,illu/ration3 ,fig4 #bc4--;,elevation ( diaphragm4 ,illu/ration3 ,fig4 #bd4--,section ( diaphragm4 #ii4--,! ,diaphragm ( ! ,telescope is s con/ruct$ z to p]mit ! displacem5t ( spid]s' webs or o!r f9e objects 9 any direction at "r angles to ! axis ( ! telescope1 or 9 ! v]tical only 9 ! dumpy level1 to be describ$1 ! object 9 all cases be+ to adju/ ! cross+ ( ! webs1 l9es1 or po9ts to ! axis ( ! telescope4 ,x w be conv5i5t "h to discuss a g5]al =m ( diaphragm applicable to !odolites1 m9+-dials1 & plane-tables only1 :i* gives movem5t 9 two directions at "r angles to ea* o!r4 #ajj4--,! diaphragm1 ,fig4 #bc1 is =m$ ( a /\t disc ( brass hav+ a c5tre hole ( ab\t #cj in* diamet]4 ,^u ! side :i* is plac$ next ! eye-piece ! hole is br\ght to a ?9 edge by an int]nal bevel or c\nt]s9k1 :i* leaves ! hole mu* l>g] at its (f surface1 ,fig4 #bd ,p4 ,! disc is held 9 its place & adju/$ by f\r cap/an-head$ screws1 t]m$ collimat+ screws1 two ( :i* are %[n 9 section z ,,cc1 ! screws be+ tapp$ into ! rim ( ! diaphragm frame ,p4 ,! screws are plac$ ?r\gh a /\t coll>4 ,! !odolite diaphragm has g5]ally ?ree spid]s' webs or l9es cross$ 9 ! mann] %[n 9 ! c5tre ( ,fig4 #bc4 ,! eye-piece is screw$ into ! ?ick plate1 ,fig4 #bd1 ,,tt1 & adju/s to ! focus ( ! webs4 ,illu/ration3 ,fig4 #be4--,webs w\nd (f = use4 #aja4--,webs4--,x is a some:at delicate process to web a diaphragm1 b x is necess>y t e surveyor abroad1 out ( ! rea* ( an optician1 %\ld und]/& ! me?od if 8 in/rum5t 7 orig9ally webb$4 ,! webs are tak5 f a small or "y g>d5 spid]4 ,! be/ are tak5 :5 ! spid] has fir/ comm5c$ sp9n+4 ,to w9d (f ! web a =k is b5t up out ( a piece ( ?9 brass wire4 ,a long hairp9 w answ] = ?is purpose v well1 or ev5 a =k =m$ ( a ?9 bran*+ twig ( a %rub2 b if ?is la/ be us$ x %\ld be ?or\ghly dry1 or ! webs w be brok5 or be baggy by its w>p+ 9 dry+4 #ajb4--,! web 9 connection ) ! spid] is fir/ atta*$ to "o prong ( ! =k by loop+ or by any /icky matt]1 if ! web be n suffici5tly /icky naturally4 ,! spid] is !n susp5d$ f ! =k & j]k$ d[n a foot or s1 & ! web is w\nd (f z %[n 9 ,fig4 #be4 ,! la/ l5g? ( web be+ atta*$ by gum4 ,a doz5 or s ( ! =ks may be tak5 f ! same spid] be=e %e is exhau/$4 ,! webs are !n gumm$ or v>ni%$ to ! sides ( ! =k1 & are ready = use at any future "t4 ,!y are be/ pres]v$ if plac$ 9 an air-tight box1 :i* may h slots 9 an int]nal fitt+ to hold !m4 ,! small am\nt ( spr+ giv5 by ! =k keeps ! webs always taut4 ,:]e a liv+ spid] _c be f\nd1 ! op5 ties ( an old web may be tak52 b 9 ?is case1 aft] ! web is w\nd on ! =k1 x %\ld be c>efully wa%$ by imm]s+ x 9 clean wat]1 &1 if necess>y1 bru%+ x g5tly "u wat] ) a light camel-hair bru%1 exam9+ x occasionally ) a magnifi] to see t x is suffici5tly clean & free f knots = its purpose4 #ajc4--,to ,fix ! ,webs1 l9es are drawn on ! diaphragm1 into :i* ! webs are to fall4 ,x is !n v>ni%$ ov] ! divid$ side ) ,canada balsam1 laudanum1 or o!r quick-dry+1 /icky v>ni%--at a p9*1 seal+-wax dissolv$ 9 /rong :isky w answ]4 ,! out]1 or ! unus$ web ^u ! =k1 is l[]$ c>efully ov] "o ( ! mo/ ne>ly v]tical l9es1 & lightly press$ d[n to assure its p]fect adhesion to ! v>ni%4 ,x is !n ei!r brok5 (f or cut loose4 ,! second ne>ly v]tical l9e is !n webb$ 9 ! same mann]1 & ! horizontal l9e f9ally1 be+ sure t ?is la/ cuts ! int]section ( ! o!rs4 ,! diaphragm %\ld !n be put 9 a w>m place to be all[$ to ?or\ghly set )\t di/urbance be=e x is fitt$ 9 ! telescope4 #ajd4--,plat9um ,wires are sometimes us$ 9 place ( webs4 ,^! wires are made by draw+ a piece ( f9e plat9um wire1 :i* has be5 previ\sly sold]$ into a silv] tube1 to ! greate/ f95ess possible ) ! draw-plate1 & aft]w>ds dissolv+ ! silv] (f ! plat9um by nitric acid4 ,! plat9um wire is ?us produc$ ( less ?an #jja in* diamet]4 ,= a "t ^! wires 7 v popul>1 & x 0 ?\ght t !y w\ld sup]s$e ! use ( webs1 b !y d n appe> entirely to answ] expectation4 ,! plat9um drawn 9 ?is mann] appe>s to lose "s "p ( its ela/icity4 ,x is n easily atta*$1 t is1 x is liable to %ift f its fix+1 possibly f its contraction & expansion ) *ange ( temp]ature1 n be+ ( ! same metal z ! diaphragm4 ,x also oxidises a little or becomes 9 "s way corrod$ 9 use out ( doors4 ,x appe>s to answ] bett] = a/ronomical telescopes1 b ! f9e/ plat9um wire obta9able is n s f9e z a spid]'s web4 #aje4--,l9es ,rul$ ^u ,glass4--,a glass diaphragm is frequ5tly us$ 9 a survey+ in/rum5t to replace ! webs4 ,l9es are rul$ ^u ! glass 9 simil> positions to ! webs already describ$4 ,!y appe> q %>p 9 ! eye-piece1 & are m p]man5t ?an webs4 ,glass is also conv5i5t = p]mitt+ space l9es to be rul$ = subt5se measurem5ts1 a subject to be consid]$ fur!r on4 ,! objections t h be5 f\nd to glass are t x ob/ructs a little light1 & is subject to dew+4 ,! dew+ is p>ticul>ly annoy+ :5 temp]ature is l[]+ quickly1 z a diaphragm may become b$ew$ _m times 9 a few h\rs4 ,9 all cases :]e a glass diaphragm is us$ x %\ld be plac$ 9 a gr\nd metal fitt+1 s t x may be tak5 out 9 a m9ute to clean & be replac$ ) p]fect c]ta9ty ( its adju/m5t4 ,x is a v conv5i5t practice :]e webs are us$ to h a sp>e glass diaphragm to replace !m %\ld !y become brok54 ,?is may be con/ruct$ by means ( a gr\nd metal fitt+ to be put 9 a webb$ in/rum5t 9 p]fect adju/m5t 9 cases :]e x might be impossible to f9d a new web4 #ajf4--,po9ts4--,! au?or = a l>ge numb] ( in/rum5ts employs v f9e po9ts 9 place ( webs1 :i* he highly recomm5ds4 ,^! are fix$ = support ^u ! m>g9 ( ! diaphragm1 & project$ !refrom into ! field ( view4 ,! po9ts are =m$ ( a special alloy1 #ge plat9um1 #be iridium1 :i* has ! h>dness ( /eel1 & is p]fectly non-corrosive 9 air or moi/ure4 ,!y are made suffici5tly /iff to be du/$ ) a camel-hair bru%1 suppli$ 9 ! in/rum5t case1 )\t ! slighte/ fe> ( di/urbance ( position 9 ! in/rum5t4 ,!y =m a p]fectly p]man5t index ( suffici5t /ability to la/ 9 p]fect adju/m5t z long z ! in/rum5t la/s 9 we>4 ,"o objection is t a po9t gives less field ( obs]vation = levell+ ?an a l9e1 b ?is does n hold if !re is tang5t adju/m5t to ! in/rum5t to br+ ! po9t up to its read+ position4 ,! value ( ! read+ f ^! po9ts w be discuss$ fur!r on4 #ajg4--,position ( ! ,diaphragm 9 ! ,telescope4--,if ! objective be accurately c5tr$1 & its m\nt+ true1 ! int]sections ( ! webs1 l9es1 or po9ts %\ld come exactly 9 ! axis ( ! telescope2 b x w\ld nev] d to accept ?is )\t critical exam9ation4 ,!re=e ! webs may be plac$ approximately 9 ! c5tre1 & adju/$ true to ! axis ( ! objective & ! telescope by :at is te*nically t]m$ collimation4 ,! fir/ po9t1 h[ev]1 to be /udi$ 9 ?is adju/m5t is to get ! eye-piece & ! objective accurately 9 focus ) ! webs4 ,! same description ( focuss+ :i* answ]s = collimation w answ] also = ord9>y use ( ! telescope4 #ajh4--;,adju/m5t ( ! ,eye-piece to ! ,webs is effect$ by pu%+ 9 or draw+ out ! eye-piece 9 its tube ) a slight screw+ motion until ! webs1 l9es1 or po9ts appe> q di/9ctly4 ,to prev5t confusion f ! sight+ ( objects1 x is bett] to take (f ! ray-%ade1 to po9t ! telescope to ! di/ance 9 opposition to ! direction ( ! sun1 & to keep ! telescope rack fully ext5d$1 s t x is q out ( focus4 ,:5 ! light is n v bright a %eet ( notepap] or an envelope may be plac$ obliquely 9 front ( ! object-glass to obta9 a s(t reflection f ! sky4 ,?is me?od is always employ$ by "s obs]v]s4 #aji4--;,adju/m5t to ,focus ( ! ,objective4--,p>allax4--,! eye-piece rema9+ 9 focus1 ! telescope is rack$ out until ! object desir$ to be br\ght into view1 ei!r = ! collimation or = ord9>y read+1 is sight$4 ,aft] ?is ! mill$ head is mov$ z sl[ly z possible until :at is ?\ght to be ! exact focus is obta9$4 ,! c]ta9ty ( exact focus is n easily obta9$ by direct obs]vation1 b x may be obta9$ by :at is t]m$ obs]vation = p>allax1 :i* mu/ be tak5 9 all cases :5 adju/m5t is requir$ = collimation4 ,?us1 hav+ obta9$ ! ne>e/ possible adju/m5t by sight+ a small object or a division ^u ! /aff1 br+ ! object to read exactly 9 a l9e above ! horizontal web 9 ! c5tre ( ! /op or ! corn] aga9/ a v]tical web4 ,if n[ ! eye be mov$ up & d[n z f> z ! range ( ! eye-piece w p]mit vision ( ! c5tre ( ! webs1 & ! object sight$ appe>s fix$ at ! same position to ! webs1 ! focus is p]fect4 ,if1 9 mov+ ! eye1 ! object sight$ appe>s to foll[ its motion ab\t ! int]section ( webs1 ! focus ( ! telescope lies beyond ! webs2 ! objective mu/ !re=e be mov$ slightly ne>] ! webs by turn+ ! mill$ head v g5tly4 ,if1 on ! o!r h&1 ! object sight$ moves 9 ! opposite direction to ! eye ab\t ! int]section ( ! webs1 ! focus ( ! telescope is t[>ds ! eye-piece1 & ! telescope requires slightly rack+ outw>ds by mov+ ! mill$ head 9 ! rev]se direction4 ,aft] a few trials ! object & webs appe> /ation>y1 h[ev] obliquely obs]v$4 #aaj4--;,collimation is ! adju/m5t ( ! cross+ ( ! webs ( ! diaphragm to ! axis ( ! telescope & its object-glass4 ,?is is effect$ by adju/m5t ( ! opposite collimat+ screws1 ,fig4 #bd1 ,,cc1 9 two directions at "r angles to ea* o!r4 ,:]e ! telescope is plac$ 9 ,y's or coll>s1 ?is adju/m5t is made by plac+ ! webs or l9es 9 focus ( ! eye-piece & ! object-glass ( ! telescope 9 focus ^u a small di/ant object4 ,!n if ! telescope is rotat$ 9 all directions1 & ! small di/ant object cuts ! cross+ ( ! webs 9 all positions1 x is said to be truly collimat$4 ,x is necess>y to discuss ! /ructure ( v>i\s in/rum5ts to %[ ! me?ods ( collimat+ 9 special cases2 !re=e ?is subject w be aga9 br\ght =w>d4 #aaa4--,! ,qualities ( a ,telescope ( a survey+ in/rum5t are be/ asc]ta9$ by its p]=mance4 ,! g5]al me?od is to place a /aff at ! full range1 #aj to #ae *a9s1 & to see if ! #ja foot 9 f9e bright wea!r is read cle>ly & %>ply4 ,?is outdoor obs]vation is n always possible1 p>ticul>ly 9 l>ge t[ns1 b x may v well be supplant$ by read+ at a %ort di/ance4 ,! au?or made = ! late ,colonel ,/range1 ,f4,r4,s41 ^: k ( sci5tific in/rum5ts 0 ( ! highe/ ord]1 a te/-c>d = ! ,lambe? ,obs]vatory1 to be plac$ at #be feet f ! in/rum5t4 ,?is c>d _h on "o "p f9e l9es rul$ #ja in* ap>t4 ,a #ad-;in* telescope 0 consid]$ suffici5tly good if ^! l9es c\ld be cle>ly sep>at$ at ?is di/ance by ! telescope :5 x 0 9 correct focus4 ,! dial ( a wat*1 or an ivory scale1 answ]s v well z a te/ object1 z %>pness ( outl9e is ! po9t to be asc]ta9$4 #aab4--;,a m ref9$ te*nical me?od ?an t describ$ above1 :i* also te/s ! g5]al accuracy ( ! optical arrangem5t ( ! telescope1 is to fix a small disc ( :ite writ+-pap]1 say #a_/h in* diamet]1 cut out ) ! po9t ( a pair ( compasses ) %>p outl9e1 on a black surface ( a bo>d1 pap]1 or clo?4 ,if ?is be plac$ z be=e1 #cj feet or m di/ant 9 a good light1 & be correctly focuss$ 9 ! telescope1 a %>p image ( x %\ld be obta9$4 ,?is focal position ( ! telescope may be tempor>ily m>k$ ^u ! inn] tube ) a f9e s(t black-lead p5cil4 ,if n[ ! object-glass be rack$ outw>ds or inw>ds f ?is l9e1 say = ab\t a twelf? ( an in*1 & ! image appe>s to be surr\nd$ ) a uni=m haze1 ! objective may be consid]$ to be correctly =m$1 or to be free f sph]ical ab]ration1 z x is t]m$1 & ! comb9ation to be correctly c5tr$4 ,if ! haze appe>s m on "o side ?an ! o!r ! c5tr+ is defective4 ,if ! object rema9s fairly %>p :5 out ( exact focus ! curves ( ! l5s are defective1 z ! %ort] ! range ( focus ! m p]fect is ! correction f sph]ical ab]ration4 #aac4--;,if ! curves are n suffici5tly correct to br+ ! image f all p>ts ( ! objective to a focus1 su* incorrect p>ts are useless1 & a good glass ( small] size w\ld be bett]4 ,! fault is g5]ally f\nd 9 ! m>g9al portion ( ! objective1 :i* requires ! greate/ skill ( ! glass-work]4 ,!re=e1 a v good te/ to f9d :e!r ! :ole ( ! ap]ture ( ! objective is 9 effective use is to cut out a piece ( c>d ( ! size ( ?is ap]ture & to cut a second piece out ( ! c5tre ( ?is1 ( half ! diamet]1 s z to =m a disc & a r+4 ,if ! objective be n[ cov]$ by ! r+ & accurately focuss$ ^u a te/ object1 & ?is be !n remov$ & replac$ by ! disc fix$ ov] ! c5tre ( ! objective1 & ! focus rema9s equally %>p1 ! curves may be said to be1 practically1 correctly work$4 #aad4--;,z ! c5tral "p ( an objective is m easily br\ght to correct curvature ?an ! m>g9al p>ts x is n uncommon 9 inf]ior in/rum5ts to make ! ap]ture ( ! c5tral /op ( ! telescope cut (f ! m>g9 ( ! objective4 ,?is r5d]s x only equal to a small] glass4 #aae4--,:e!r ! full ap]ture ( a telescope is us$ may be discov]$ by employ+ a second eye-piece--outside ! regul> eye-piece t is plac$ 9 ! telescope--to pick up ! image ( ! object glass =m$ ?r\gh ! eye-piece :i* is plac$ aga9/ ! telescope 9 ! mann] ( us+ a dynamet]1 art4 #hg4 ,) ! ord9>y surveyor's level1 two eye-pieces are commonly sold2 "o ( ^! may be plac$ 9 ! telescope & ! o!r us$ to pick up ! image ( ! object-glass4 ,) a !odolite "o eye-piece may be plac$ 9 ! telescope1 & "o ( ! read]s us$ to magnify ! divisions ( ! limb may be us$ to pick up ! image4 ,! be/ mann] ( proce$+ is to fix ) wat] or ?9 gum two or ?ree small pieces ( pap]1 say #a_/bj1 #a_/aj1 & #a_/g in* squ>e1 close aga9/ ! edge ( ! cell ^u ! face ( ! objective4 ,!n focus ! telescope on an object at "s di/ance1 say a *a9 or two4 ,n[ use ! second eye-piece 9 front ( ! "o 9 ! telescope1 & an image ( ! object-glass w be se52 & if ! ap]ture is fully op5 all ! pieces ( pap] 9 _! places w be cle>ly di/+ui%able4 ,if "o or o!r piece is invisible1 ! m>g9 ( ! glass is cut (f to ?is ext5t4 ,if ! objects 9 front ( ! telescope t5d to confuse1 a piece ( :ite pap] may be plac$ obliquely to reflect ! light ( ! sky into ! telescope1 :i* w at ! same "t fully illum9ate ! objective4 ,! discussion ( ! pr9ciple ( ! anallatic telescope1 us$ only ) ! ta*eomet]1 is def]r$ to ano!r *apt]1 :]e9 subt5se in/rum5ts are describ$4 ,,*apt] ,,iii4 ,,! ,,magnetic ,,compass ,,z ,a ,,"p ,,( ,a ,,survey+ ,,in/rum5t ,,or ,,sep>ately--,,broad ,,& ,,edge-,,b> ,,ne$les--,,manufacture ,,( ,,! ,,ne$le--,,magnetisation--,,susp5sion--, ,dip ,,& ,,adju/m5t-- ,,lift+--,,incl9ation--,,decl9ation--,,v >iation--,,correction-- ,,compass-,,boxes--,,description ,,( ,,compasses--,,r+ ,,compasses--,,tr\gh ,,compasses--,,prismatic ,,compasses--,,/&--,,survey+ ,,) ,,compass--,,pocket ,,compasses4 #aaf4--,! ,magnetic ,ne$le1 :i* =ms "p ( a great _m survey+ in/rum5ts1 is made ( ! =m adapt$ to ! special purposes ( ! in/rum5t 9 :i* x is plac$4 ,!re are two prevail+ =ms commonly 9 use--"o 9 :i* ! ne$le is made po9t$ at "o or bo? ends to read directly ^u a divid$ circle fix$ ^u ! in/rum5t1 & ! o!r =m 9 :i* x is made to c>ry & to direct a divid$ circle by its magnetic =ce4 ,illu/ration3 ,fig4 #bf4--;,broad ne$le4 ,illu/ration3 ,fig4 #bg4--;,edge-b> ne$le4 ,! magnetism :i* gives directive =ce to ! ne$le has be5 f\nd by exp]im5t to reside 9 e sep>ate "p ( ! magnet1 t is1 x is assum$ to be a molecul> =ce4 ,!re=e1 x w\ld n appe> to be v important1 )9 c]ta9 limits1 ( :at =m ! magnetic ne$le is made1 & ?is is f\nd by exp]im5t to be to a l>ge ext5t true4 ,! only important conditions appe> to be t ! ne$le %all be ( su* =m t ! induc+ magnet1 to be describ$1 arts4 #abj-abc1 :i* is us$ = magnetis+ may be br\ght into contact ^u e "p ( its surface1 & t ! molecul> cont9uity ( ! p>ts %\ld mutually support ! g5]al directive influ5ce ( ! magnetism longitud9ally 9 p>allel l9es4 #aag4--,magnetic ne$les are g5]ally made 9 ! =m ( flat b>s1 :i* are balanc$ ^u a /&+ po9t fall+ into a cup :i* =ms ! c5tre4 ,:5 ! greate/ section ( ! b> is plac$ horizontally x is t]m$ a broad ne$le1 z %[n ,fig4 #bf4 ,?is may be made ( ! loz5ge =m %[n1 or be p>allel ?r\gh\t4 ,:5 ! greate/ section is plac$ v]tically x is t]m$ an edge-b> ne$le1 z %[n ,fig4 #bg4 ,! nor? po9t+ end ( ! broad ne$le is commonly temp]$ d>k blue1 or has a deep cut across x1 if ! ne$le is left op54 ,?is is n necess>y if x c>ries a r+4 ,! edge-b> is g5]ally us$ :]e x is requir$ to read into a fix$ circle ( division1 9 :i* case its ends are br\ght to f9e knife-edges4 #aah4--;,f ! difficulty ( read+ a %>p po9t 9 bright metal aga9/ ! black l9e ( a divid$ circle1 ! au?or occasionally makes "o po9t ( ! ne$le ) a f9e cut1 sawn v]tically = a %ort di/ance f its end1 s z to =m a k9d ( split :i* is aft]w>ds clos$1 s t x pres5ts ! appe>ance ( a f9e black l9e ( ! same "* z ! divisions into :i* x reads4 ,) ?is1 z %[n ,fig4 #bh1 ! read+ is f\nd to be mu* m easy4 ,! po9t is also m readily adju/$ by gr9d+1 z ! end ( ! ne$le be+ broad1 less c>e is necess>y to avoid r$uc+ x s mu* t x may leave ! int]ior ( ! circle %ort :]e x reads into ! divisions4 ,?is =m ( ne$le is n adapt$ to m9+ in/rum5ts1 :i* h (t5 to be read 9 an oblique direction4 ,illu/ration3 ,fig4 #bh4--;,au?or's plan ( ne$le read+4 #aai4--;,9 ! ,manufacture ( ! ,ne$le x %\ld be made ( ! f9e/ cutl]'s ca/ /eel1 or1 bett] /ill1 ( /eel conta9+ #c p] c5t4 ( tung/54 ,if n left 9 a p>allel /rip z x is drawn or roll$1 x %\ld be br\ght z ne>ly to its =m z possible by =g+ at a l[ heat4 ,! /eel %\ld n be ov]-heat$ = h>d5+4 ,x %\ld be h>d5$ 9 cold wat] or oil1 & be temp]$ aft]w>ds d[n to a v pale /raw-col\r--9 fact1 ! temp] col\r %\ld only j appe>4 ,long ne$les may h ! temp] suffici5tly l[]$ at ! c5tre to set !m approximately /raight dur+ ! temp]+2 b ! temp] %\ld n be l[]$ ev5 9 ! c5tre bel[ a pale blue1 spr+ temp]4 ,aft] temp]+1 ! sett+ & work+ up to balance is be/ done by gr9d+1 & = ! f9al adju/m5t1 by /on+ ) ,wat]-(-,ayr /one4 #abj4--,magnetisation ( ! ,ne$le may be p]=m$ 9 _m ways by means ( a p]man5t magnet or an electro-magnet1 or electrically by means ( a sol5oid4 ,:5 ! magnetism is induc$ f ano!r magnet x is only important t ! prop]ly h>d5$ ne$le %\ld be regul>ly & equally magnetis$ ov] its surface by pressure ^u x ( ! prop] poles ( ! induc+ magnet--t is1 t ! nor? pole ( ! magnet %\ld induce magnetism 9 ! s\!rn half ( ! ne$le only2 & ! s\? pole 9 ! nor!rn half only4 #aba4--,me?od ( ,magnetisation by ,s+le-t\*4--,?is me?od is m g5]ally appli$ to t\*+ up ne$les ?an magnetis+ !m at fir/4 ,! nor!rn pole ( a /rong p]man5t magnet is /rok$ d[n ! s\!rn end ( ! ne$le f its c5tre to its end ?ree times on "o side ( ! ne$le4 ,! ne$le is !n turn$ r\nd1 & ! nor!rn end is /rok$ d[n 9 l mann] ) ! s\!rn pole4 ,! ne$le is !n turn$ ov]1 & ! process is repeat$ on ! o!r side4 ,?is may be done a second "t & ! edges ( ! ne$le be /rok$ d[n also4 #abb4--,me?od ) bo? ,poles4--,9 ?is process ! ne$le is held d[n firmly ) pegs on a bo>d1 & a /rong horse-%oe magnet ) r close poles is laid on ! b>e ne$le )\t its cap1 9 a mann] t bo? t]m9als press ^u x4 ,x is !n drawn backw>ds & =w>ds f end to end ( ! ne$le sev]al times1 lift+ ! magnet f9ally f ab\t ! c5tre4 ,! process is !n repeat$ on ! opposite side ( ! ne$le & its edges4 ,illu/ration3 ,fig4 #bi4--;,divid$-t\* magnetisation4 #abc4--,me?od ( ,divid$-t\* is a some:at quick] process1 :i* does n entail remov+ ! cap1 ! g5]al plan ( :i* is %[n 9 ! engrav+ bel[4 ,! poles ( ! magnets1 or "o ( !m1 is m>k$4 ,two good /raight b> magnets are us$4 ,! ne$le is fix$ d[n on a bo>d & ! poles ( ! two magnets are laid ^u x at an angle ( ab\t #cj1 apply+ "o nor? or m>k$ pole1 & "o s\? or unm>k$ pole4 ,! magnets are !n drawn ap>t 9 a horizontal direction along ! ne$le1 ) con/ant pressure ^u x1 s z to rea* ! opposite ends ( ! ne$le simultane\sly1 & !n aga9 press$ back to ! c5tre4 ,aft] ?is op]ation is p]=m$ ?ree or f\r times on "o side ( ! ne$le1 x is turn$ ov] & ! process is repeat$ on ! o!r side1 be+ c>eful z be=e to use ! same ends ( ! magnets ^u ! same ends ( ! ne$le4 ,! op]ation may be repeat$ sev]al times to be sure ( saturation ( ! ne$le4 ,x is bett] to lift ! magnets (f at ! t]m9ation ( ! op]ation at ! c5tre ( ! ne$le4 #abd4--;,x is f\nd t ! ne$le is magnetis$ a little m quickly if x is laid ^u a /rong magnetis$ b> dur+ magnetis+1 or ^u ! ends ( two b>s1 z %[n 9 ! engrav+1 ,fig4 #bi1 or on ! two ends ( a wide horse-%oe magnet4 #abe4--,ne$les are n[ m g5]ally magnetis$ electrically by plac+ !m 9 a sol5oid or coil ( /\t insulat$ copp] wire ?r\gh :i* a /rong direct curr5t is pass+ f a dynamo or p[]ful batt]y4 ,?is me?od is employ$ 9 ! be/ %ops4 ,! t\* sy/em above describ$ is conv5i5t = ! pr(ession = remagnetis+ a ne$le :5 weak1 z a horse-%oe magnet at small co/ may be kept = ! purpose4 ,x is g5]ally us$ 9 small %ops1 z be+ at all times ready to h&1 less exp5sive1 & suffici5t to ensure saturation if x is skilfully done4 #abf4--,) e c>e 9 ! manufacture ( ! ne$le !re rema9s a little diff]5ce 9 ! qualities ( ne$les :i* are app>5tly o!rwise id5tical4 ,little local diff]5ces 9 ! quality ( ! /eel1 slight ov]-cry/allisation f ov]-heat+ 9 h>d5+ or unequal temp]+1 or unequal magnetis+1 are liable to =m weak p>ts1 or ev5 :at are t]m$ consequ5t po9ts4 ,^! are po9ts 9 :i* ! magnet possesses a rev]sal ( its g5]al longitud9al pol>ity4 ,?is c be made q evid5t by exp]im5t1 z x is possible to make a ne$le n only ) poles at ea* end1 b ) int]m$iate poles :i* are easily detect$ by sift+ iron fil+s ov] x4 ,! fil+s are f\nd to adh]e /rongly at o!r local po9ts ?an ^? ne> ! ends1 :]e a good magnet is alone /rongly attractive4 #abg4--,m\nt+ ( ! ,ne$le4--,! ne$le = a survey+ in/rum5t has a female c5tre ^u :i* x is susp5d$4 ,! c5tre1 t]m$ te*nically cap1 is g5]ally =m$ ( a h>d preci\s /one1 agate1 *rysolite1 ruby or sapphire1 ! latt] be+ be/1 simply f ! high poli% x atta9s 9 gr9d+ out ) diamond du/4 ,rubies & sapphires are l m9]als1 except 9 ! col\r1 :i* v>ies v mu*2 ! (f-col\r /ones1 :i* are ( small value = jewell]y1 are us$ = sci5tific purposes4 ,! cap is m\nt$ 9 a brass or alum9ium cell made z light z possible = suffici5t /ability4 ,! ne$le is support$ ^u a h>d5$ /eel po9t1 ^u :i* x is p]fectly balanc$4 ,! base ( ! po9t is temp]$ d[n to a l[ degree 9 ord] to admit a c]ta9 am\nt ( b5d+ to c\nt]act ! slight w>p+ :i* g5]ally occurs 9 ! h>d5+4 #abh4--;,correction ( ,errors4--,! ne$le1 aft] x is m\nt$1 al?\gh 9 balance may n h ! /eel plac$ symmetrically ab\t its axis ?r\gh slight curvature1 unequal ?ickness ab\t ! cap1 or o!rwise1 s t ! magnetic direction is n p]fectly l9e> betwe5 ! po9ts & ! c5tre4 ,if ! po9ts & c5tre are n magnetically l9e>1 ! correction = decl9ation1 :i* w be pres5tly consid]$1 _c be made accurately4 ,on ?is acc\nt x is bett] = ! manufactur] to m\nt ! ne$le on a slate b$ ) two slid+ heads t may be br\ght up to ! po9ts ( ! ne$le4 ,! heads h ^u _! upp] surfaces l9es drawn p]fectly l9e> ) ! c5tre po9t ( susp5sion ( ! ne$le1 & a few lat]al divisions to ^! l9es = det]m9+ errors4 ,on ?is b$ ! ne$le is plac$ ^u ! c5tre po9t to be exam9$ h[ ne>ly its read+ po9ts are true ) ! axis4 ,! error be+ record$1 ! ne$le is demagnetis$1 & remagnetis$ end = end1 & aga9 exam9$4 ,corrections are !n made by gr9d+ or /on+ f obs]vations ( bisections ( ! po9ts cut 9 ! sep>ate read+s1 until ! ne$le is made symmetrical & inv>iable1 :i*ev] end is magnetis$ = ! nor? or s\?4 ,illu/ration3 ,fig4 #cj4--,section ( m\nt$ ne$le4 #abi4--,lift+ ! ,ne$le4--,! ne$le ( a survey+ in/rum5t %\ld nev] be support$ ^u its c5tre except = ! "t x is 9 use = obs]vation1 z a f9e /eel po9t aga9/ a h>d /one mu/1 by any j> 9 conveyance f place to place1 receive a c]ta9 am\nt ( abrasion t w make x dull]4 ,= ?is reason a lift = ! ne$le is always provid$ 9 sci5tific in/rum5ts4 ,9 ! engrav+1 ,fig4 #cj1 an edge-b> ne$le is %[n 9 section ) its lift4 ,! lift is made 9 ! =m ( a b5t lev]1 ^: fulcrum is ^u ! bottom ( ! box4 ,on ! left-h& side ( ! brok5 l9e at ,b ! ne$le is %[n lift$4 ,on ! "r-h& side ,a ! ne$le is %[n at its position = use1 float+ j slightly above ! divid$ circle ,d4 ,! pressure ( ! mill$-head screw ,c depresses ! b5t lev] or lift on ! bottom ( ! box & !reby raises ! po9t "u ! c5tre ( ! ne$le4 ,?is po9t has a holl[ cone =m$ ^u x :i* fits ov] ! /&+-po9t to keep ! lift 9 position4 ,! cone fits ext]nally into ! cap to lift ! ne$le v]tically4 ,! screw ,c %\ld always be clamp$ d[n :5 ! ne$le is out ( use4 ,9 place ( ! screw a w$ge %ap$ slid+ piece is sometimes fix$ inside ! compass-box1 :i* is mov$ by a /ud project+ ?r\gh ! out] case4 ,ano!r plan ( rais+ ! lift is by a cam1 or :at is te*nically t]m$ a kidney-piece1 appli$ to ! ext]ior "p ( ! lift4 ,ei!r ( ^! plans answ]1 b ! screw fir/ describ$1 be+ ! g5tl] motion1 j>s ! ne$le lea/4 ,a screw is occasionally us$ longitud9ally to ! ne$le connect$ ) a cam lift1 ! object 9 all cases be+ to lift ! cap entirely cle> ( ! /&+-po9t4 #acj4--,! ,incl9ation or ,dip ( ! ,ne$le is ! position a ne$le balanc$ level ^u a free c5tre be=e magnetisation takes 9 ! v]tical plane aft] magnetisation4 ,?is incl9ation or dip v>ies 9 diff]5t p>ts ( ! globe1 & at diff]5t times4 ,at ! pres5t "t at ,gre5wi* 7,jan41 #aiad7 ! angle is #ff #ej f ! horizontal4 ,x is uni=mly ne>ly nil at ! equator1 & increases until ov] "o ( ! magnetic poles1 :]e x becomes v]tical4 ,!re are two magnetic poles 9 ! nor!rn hemisph]e active 9 direct+ ! ne$le1 "o 9 ,sib]ia1 b ! mo/ active is ab\t ,melville ,isl&2 also two 9 ! s\!rn hemisph]e1 :i* are suppos$ to be ne>ly toge!r1 b ! exact positions ( :i* are n asc]ta9$4 ,z we require only ! horizontal compon5t 9 survey+ & n ! dip1 x is necess>y to balance ! ne$le 9 opposition to ! direction ( ! dip until x keeps 9 a horizontal position4 ,?is may be done by mak+ ! ne$le light] on ! dip side--t is1 ! nor!rn 9 ?is hemisph]e4 ,b ! plan adopt$ 9 all sci5tific in/rum5ts is to place a rid] ov] ! ne$le1 z %[n ,fig4 #cj "u ,b4 ,?is clips ! ne$le suffici5tly to hold x firmly to its place1 & yet is loose en\gh to be mov$ by ! f+]s to balance4 ,! rid] has to be %ift$ :5 ! in/rum5t is tak5 into a c\ntry :]e ! dip is diff]5t f its position at home4 ,:5 a ne$le is tak5 abroad )\t any rid]1 x may be balanc$ by means ( a little seal+-wax plac$ ^u its upt5d+ end4 #aca4--,to get at ! ne$le = suppression ( dip :5 x is plac$ 9 ! compass-box1 x is necess>y to raise ! spr+ r+1 :i* is plac$ ov] ! glass to keep x d[n1 by ins]t+ ! po9t ( a pocket-knife betwe5 ! r+ & ! glass1 mov+ ! knife entirely r\nd x & us+ a little twi/ ^u x if necess>y until ! r+ is free4 ,?is mu/ be done g5tly or ! glass w break4 ,! ne$le is !n adju/$ to read correctly to ! plane ( ! divid$ circle & is replac$ 9 its box4 ,! glass is !n replac$ & ! spr+ r+ is press$ d[n by pass+ ! f+] firmly r\nd x until x is tight ^u ! glass4 ,sometimes a little extra pressure by a h>d body is ne$$1 b ?is mu/ be done ) c>e or ! glass w be brok54 #acb4--,! ,decl9ation ( ! ,ne$le1 t is1 its v>iation 9 po9t+ 9 a true nor!rnly & s\!rnly direction1 is necess>y to be kn[n & consid]$ by ! surveyor :]e ! ne$le is us$1 bo? 9 relation to ! locality & to ! "t1 z ?is decl9ation n only v>ies 9 diff]5t c\ntries b also f ye> to ye>4 ,= in/ance1 ?is ye> 7,jan41 #aiad7 x po9ts #ae #ab ,we/ at ,gre5wi*4 ,! foll[+ *>t1 ,fig4 #ca1 gives ! decl9ation v>iation = #aiad4 ,! :ole sy/em ( decl9ation l9es is n[ mov+ we/w>d at ! rate ( ab\t sev5 m9utes p] annum1 b ! rate v>ies slightly & f ye> to ye>4 ,! decl9ation l9es1 indep5d5tly ( correction1 :i* w be pres5tly consid]$1 may n be exactly repres5t$ by ! symmetrically curv$ l9es %[n 9 ! figure4 ,!re are small local deflections f ! !oretical curves "h giv51 :i* are p]man5t & ne$ local consid]ation :5 us+ ! ne$le = obta9+ v correct be>+4 ,^! h be5 ably consid]$ by ,pr(essor ,rck] & ,dr4 ,?orp1 b ! subject is too complicat$ to be ent]$ ^u "h1 except = ?is note ( obs]vation4#b #acc4--;,= new c\ntries1 :]e ! ne$le (t5 becomes mo/ important f ! impossibility ( ty+ up l9es by direct obs]vation ?r\gh =e/s & o!r ob/ructions1 ref]5ce mu/ be _h to magnetic *>ts :i* give sy/ems ( l9es easily work$ ?r\gh by symmetry1 ev5 = unexplor$ c\ntries4 ,at pres5t ! decl9ation is we/ 9 ,europe & 9 ,africa2 ea/ 9 ,asia & ! great] "p ( ,nor? & ,s\? ,am]ica4 ,illu/ration3 ,fig4 #ca4--,magnetic & ,gre5wi* "t *>t = ,great ,brita91 #aiad4 #acd4--,! ,magnetic ,v>iation ( ,decl9ation 9 ,"t1 becomes important 9 ref]5ce to old plans 9 :i* ! magnetic nor? ( ! p]iod has be5 plott$ = ! true nor? v mu* to ! pecuni>y advantage ( ! legal pr(ession :5 engag$ ^u actions ) reg>d to disput$ b\nd>ies4 ,! foll[+ table gives an idea ( ! v>iation 9 decl9ation = ,gre5wi* approximately = a few dates3-- ,ye> #aehj1 ,dec4 #aa #cf ,e4 ,ye> #ahfj1 ,dec4 #bj #dj ,w4 #affc1 #j #ahgj1 #bj #ai ,w4 #agjj1 #h #bj ,w4 #ahhj1 #ah #eh ,w4 #ahah1 #be #da ,w4 #ahij1 #ag #i ,w4 #ahej1 #ai #ca ,w4 #aijj1 #af #cj ,w4 ,x w be se5 by ! above table t ! ne$le po9t$ due nor? 9 #affc1 t x atta9$ its greate/ we/]n decl9ation 9 #ahah1 & t x is n[ los+ its we/]ly decl9ation at ! rate ( ab\t #g annually4 #ace4--;,annual ,v>iation4--,! decl9ation is subject also to a small annual v>iation :i* is greate/ ab\t spr+ "t1 dim9i%es t[>ds ! summ] sol/ice1 & increases aga9 dur+ ! foll[+ n9e mon?s4 ,x v>ies at diff]5t p]iods1 & seldom exce$s #af ( arc4 #acf4--;,decl9ation ,correction to true nor? may be made = ! compass by obs]vation 9 ?is hemisph]e ( ! pole />1 :i* is practically due nor? 9 ,janu>y at #f p4m41 ,febru>y at #d a4m41 ,m>* at #b a4m41 ,april at midnight1 ,may at #aj p4m41 ,augu/ at #d a4m41 ,septemb] at #b a4m41 ,octob] at midnight1 ,novemb] at #aj p4m41 ,decemb] at #h p4m4 ,mo/ survey+ in/rum5ts1 except ! transit !odolite1 are n made conv5i5t = ?is obs]vation4 ,m g5]ally obs]vations ( ! position ( ! sun may be made :]e a sun-glass is provid$ to ! telescope ( ! !odolite1 ,fig4 #ai1 ,,sg1 page #de1 ) ! aid ( a *ronomet] or a good wat*4 ,= ?is obs]vation we may rememb] t ! sun is true s\? at twelve o'clock on ! #af? ,april1 #ae? ,june1 #a/ ,septemb]1 & #be? ,decemb]4 ,! foll[+ table may be useful = "s int]m$iate times to %[ h[ mu* ! *ronomet] 7mean "t7 is fa/] or sl[] ?an ! sun's s\?+ approximately at noon3-- ,jan4 #a subtract #d m94 ,july #ae subtract #f m94 #af #aj #cj #f #ca #ad ,aug4 #ad #d ,feb4 #ae #ad ,sept4 #ac add #d ,m>4 #b #ab #bh #i #ag #h ,oct4 #ac #ad ,april #a #d #bh #af ,may #a add #c ,nov4 #ab #af #af #d #bg #ab #ca #c ,dec4 #ab #f ,june #cj subtract #c #ca subtract #c #acg4--;,z v>iation 9 "t ( s\?+ is f f\rte5 m9utes fa/ to sixte5 sl[1 or a diff]5ce ( ?irty m9utes1 correction becomes important1 z ! sun passes ov] #g 9 ?is p]iod4 ,9 ^! obs]vations ! diaphragm l9es1 webs1 or po9ts mu/ bisect ! sun's disc4 ,?is is done m exactly by tak+ ! mean positions ( ! sun's ea/]n & we/]n limbs or its semi-diamet]1 :i* is giv5 = e day ( ! ye> 9 ! ,nautical ,almanac4 #ach4--,! ,compass-box4--,! ne$le1 z x is g5]ally m\nt$ = ! !odolite1 m9+-dial1 & _m o!r in/rum5ts1 reads into a divid$ circle ( #cfj4 ,! circle is rais$ up f ! bottom ( ! compass-box to ! height ( ! top ( ! ne$le1 z %[n 9 section ,fig4 #cj1 ,d1 & is g5]ally silv]-plat$4 ,! bottom ( ! compass-box is sometimes divid$ ) a compass-rose giv+ ! po9ts ,n4 ,e4 ,s4 ,w4 ,! ,e4 & ,w4 9 "s cases are rev]s$ f _! natural directive positions f ! c5tre ( ! box1 s z to read ! lett] indicat+ ! po9t ne>e/ to ! division in/ead ( t opposite to x4 ,9 mod]n survey+ in/rum5ts1 h[ev]1 no reg>d is paid to ! po9ts ( ! compass1 nor? be+ #j1 ea/ #ij1 s\? #ahj1 we/ #bgj4 #aci4--;,9 ! manufacture ( ! compass-box v great c>e %\ld be tak5 t ! metal is q free f iron1 & t no iron comes ne> x4 ,on ?is po9t ! mak] _c be too gu>d$4 ,! au?or has 9 sev]al in/ances f\nd ! compass-box ( p]fectly free metal2 b a s+le f\l screw made ( comm]cial brass wire1 be+ us$ to fix ! r+ or ! rose plate1 has by its influ5ce entirely de/roy$ ! value ( ! compass4 #adj4--;,9 ! con/ruction ( ! compass-box ! au?or has f\nd ! mo/ c]ta9 me?od ( gett+ ! divisions correct ) ! c5tre is to make ! division directly f ! /&+-po9t ( ! compass1 & n to try to get ?is po9t correct to ! divisions aft]w>ds4 ,! /&+-po9t may be fix$ directly to ! box by screw+1 or be atta*$ to a brass plate be=e fix+4 ,x is adju/$ to ! compass-box by b5d+ until ! ne$le turns freely1 b at ! same "t ne>ly t\*es ! circle4 ,! ne$le is !n remov$ & ! circle is divid$ ) ! po9t z its c5tre4 ,:]e ! divisions read to ! po9t ( ! ne$le1 or to a l9e ^u x )\t a magnifi]1 ! divisions ( ! circle may be made directly ^u ! la! by a lev] to ! slide-re/ if ! la! has a well-divid$ head/ock4 ,:5 ! divisions are magnifi$ & require great accuracy1 or :]e a float+ r+ is us$ ^u ! ne$le1 ! circle %\ld be divid$ ^u ! divid+ eng9e1 :i* w be describ$ fur!r on1 ! c5tre us$ be+ /ill ! po9t or pivot on ! bottom ( ! case1 f :i* ! divisions are to be made radially4 #ada4--,pres]vation ( ! ,magnetism 9 ,ne$les4--,x is mo/ important t ! magnetism ( ! ne$le1 p>ticul>ly 9 m9+-dials :]e s mu* dep5ds ^u x1 %\ld be pres]v$ to ne> saturation 9 ord] to secure c]ta9 direction 9 opposition to ! friction ( ! c5tre1 necess>ily always pres5t4 ,?is is (t5 mu* neglect$ f c>elessness1 or want ( k ( ! pr9ciples ( magnetic action4 ,9 ! fir/ place we "k t a b> ( s(t iron1 possess+ no evid5t magnetism1 if x be plac$ 9 ! magnetic m]idian ) prop] dip1 w aft] a "t manife/ /rong magnetic prop]ties4 ,?us1 su* a b> 9 ,london plac$ due nor? & s\?1 ) a dip ( #fg to ! nor?1 becomes a weak magnet4 ,f ?is we may also inf]1 & ?is exp]im5t %[s1 t a ne$le plac$ 9 ?is position w n lose its magnetism4 ,b :at is mo/ important to obs]ve is t if ! ne$le is plac$ 9 a contr>y direction1 z1 = in/ance1 ) its nor!rn end t[>ds ! s\?1 x is 9 con/ant opposition to ! influ5ces ( t]re/rial magnetism1 & w c]ta9ly become weak]4 ,!re=e1 al?\gh x is necess>y to lift ! ne$le :5 c>ry+ ! in/rum5t1 :i* mu/ necess>ily place its poles 9 all directions1 x is n at all necess>y t ! ne$le %\ld be lift$ :5 ! in/rum5t is put by out ( use4 ,inde$1 magnetism is mat]ially pres]v$ by releas+ ! lift to let ! ne$le take its true be>+4 ,?is does n at all injure ! /&+-po9t1 z !re is no movem5t ^u x to cause we>4 ,( c\rse if ! ne$le is at fir/ magnetis$ beyond its p]man5t condition x w lose ?is surplus magnetism1 b ! residual magnetism 9 ?is position w rema9 ne>ly con/ant4 #adb4--;,a valuable precaution = a ne$le 9 con/ant we> is occasionally1 say twice a ye>1 or mu* (t5] if x is us$ 9 a du/y m9e1 to take x out ( its box & wipe out ! cap ) ! po9t ( a small sable bru%4 ,! /&+-po9t may at ! same "t be %>p5$ if necess>y by g5tly rubb+ x all r\nd ) a slip ( oil$ ,arkansas /one at its =m] po9t+ angle4 ,! %>pness ( a ne$le is easily asc]ta9$ by slid+ ! ?umb-nail ov] ! po9t at an angle ( ab\t #cj to x4 ,if ! po9t /icks & holds ! nail1 x is %>p2 if x glides ^u x1 x is dull4 ,! au?or has (t5 _h compasses ( v>i\s k9ds s5t to him = remagnetisation ^: only fault has be5 dulness ( c5tre4 #adc4--,r+ ,compasses4--,9 mod]n !odolites1 levels & prismatic compasses1 ! magnetic ne$le c>ries a light divid$ circle1 :i* is n[ g5]ally made ( alum9ium on acc\nt ( ! extreme lightness ( ?is metal4 ,a broad ne$le is us$ ( ab\t in* 9 wid? & #a_/ah in* 9 ?ickness4 ,!re is consid]able difficulty 9 m\nt+ ! circle to get x truly conc5tric & correct = be>+1 !re=e r+ compasses are (t5 f\nd to be inaccurate4 ,! au?or has foll[$ two me?ods ( con/ruction1 ei!r ( :i* answ]s fairly well3--,! "o is to leave a b> across ! compass :5 cutt+ out ! compass r+ f a plate ( alum9ium4 ,9 ?is case1 :5 ! out] edge ( ! r+ is *uck$ 9 ! la! to be turn$1 a c5tre hole is also made 9 ! cross-b> :i* exactly fits ov] ! cap ( ! ne$le1 s t ! adju/m5t = c5tre is practically secur$1 & att5tion is only necess>y to get ! adju/m5t correct = be>+--t is1 ! #j at true magnetic nor? to ! axis ( ! ne$le4 ,ano!r me?od1 :i* 0 sugge/$ to ! au?or by ! late ,mr4 ,?os4 ,cu%+ ( ! ,india ,(fice1 answ]s p]fectly1 & only entails a little extra tr\ble 9 sett+ = divid+4 ,?is is to p]man5tly m\nt ! r+ on ! ne$le )\t any means ( aft]-adju/m5t1 & to divide ! circle f a po9t plac$ 9 ! axis ( ! divid+ eng9e1 ^u :i* ! ruby c5tre is plac$1 be+ ( c\rse p>ticul> t ! z]o l9e #j cuts ! magnetic axis true nor? 9 ! graduation4 #add4--,m>9]s' ,compasses1 & an inexp5sive class ( prismatic compasses1 are made ) a pap] disc 9 place ( ! r+ above describ$ answ]+ ! same purposes4 ,! pap] disc is g5]ally made 9 two ?icknesses ) a ?9 %eet ( talc plac$ betwe5 !m4 ,m>9]s' compasses h frequ5tly ! divisions pa9t$ directly ^u talc = transp>5cy by light+ f b5ea?1 also = g5]al lightness comb9$ ) /iffness4 #ade4--,! read+ ( m>9]s' compasses1 & ! compasses on levels :]e ! ne$le c>ries a divid$ r+1 is tak5 f a l9e drawn v]tically up ! inside ( ! box or a po9t]4 ,?is lead l9e 9 ! m>9]s' compass gives ! direction ( ! head ( ! vessel2 a po9t] 9 ! level compass gives a direction 9 l9e ) ! axis ( ! telescope4 ,9 high-class !odolites1 a microscope is us$ by ! au?or read+ to a spid]'s web 9 ! diaphragm4 #adf4--,tr\gh ,compass1 sometimes t]m$ a long compass4 ,:]e an in/rum5t possesses a d\ble v]tical axis & a divid$ circle1 z ! !odolite1 ! division ( ! circle may take ! place ( ! divid$ r+ ( ! compass & save ! repetition ( ! graduation1 at ! same "t ! ne$le may (t5 be made long]1 z ! bulk ( ! compass-box is proportionately less4 ,9 fact 9 all cases :]e ! magnetic nor? only is requir$ ! tr\gh compass is to be pref]r$4 ,! ord9>y con/ruction ( ?is compass is 9 ! =m ( a n>r[ box1 ,fig4 #cb1 ,a repres5t+ a plan1 & ,b a p>allel section tak5 ?r\gh x horizontally4 ,ab\t #aj are graduat$ on ea* side ( ! m]idian l9e1 aa be+ adju/+ screws to br+ ! scale true ) ! ne$le4 ,illu/ration3 ,fig4 #cb4--,tr\gh compass = atta*m5t to an in/rum5t4 #adg4--,magnification ( ,read+4--,) ! tr\gh compass x is v common to h "s =m ( microscope = read+ ! ne$le m exactly4 ,?is may be done by a ,ramsd5 eye-piece be+ plac$ directly ov] ! ne$le1 z is common 9 "s ,g]man in/rum5ts4 ,a mu* m conv5i5t plan = c]ta9 in/rum5ts is to read ! ne$le longitud9ally4 ,?is is g5]ally done by means ( a transp>5t scale be+ plac$ across ! end ( ! ne$le :i* is divid$ ^u glass or horn4 ,?is may read to ei!r ! ne> or di/ant po9t ( ! ne$le4 ,a v good =m ( ne$le read+ is f\nd 9 "s ,fr5* in/rum5ts4 ,?is is %[n ,fig4 #cc1 :]e ! compass is %[n entirely enclos$ 9 a tube ,c :i* protects x f du/4 ,! ne$le ,n has a v]tical po9t fix$ ^u its end at ,p :i* reads pretty closely to a scale ( #aj divid$ ^u glass at ,g by ! eye-piece ,e4 ,x has a lift] ,l press$ up by a mill$-head screw ,m4 ,fig4 #cd %[s ! graduat$ glass4 ,?is compass is atta*$ b5ea? ! limb ( a !odolite1 or 9 any o!r conv5i5t position ^u an in/rum5t4 ,! au?or has plac$ a compass con/ruct$ ^u ?is pr9ciple 9 a telescope1 9 su* a mann] t ! ne$le may be read ) ! eye-piece1 s z to cut a l9e ) a di/ant object co9cid5t ) ! l9e cut by ! pr9cipal telescope ( ! in/rum5t at #j ( its graduation4 ,?is plan w be m fully expla9$ ) ta*eomet]s1 ,*apt] ,,xii4 ,illu/ration3 ,fig4 #cc4--,ne$le ) read]4 ,illu/ration3 ,fig4 #cd4--,scale at ,g4 #adh4--,! ,prismatic ,compass1 %[n ,fig4 #ce1 0 inv5t$ by ,*>les ,augu/ ,s*malcald] 9 #ahab4 ,x is ! mo/ conv5i5t portable in/rum5t = read+ magnetic be>+s4 ,angles may be tak5 ) great rapidity )9 ab\t #ae ( arc by hold+ ! in/rum5t 9 ! h&1 or p]haps )9 #e if ! in/rum5t is ( #d to #f in*es diamet] & plac$ on a /&4 ,x is a mo/ valuable in/rum5t = fill+ 9 close details1 su* z may occur among build+s1 trees1 etc41 aft] ! pr9cipal po9ts h be5 laid d[n f obs]vations tak5 ) ! !odolite4 ,! pr9ciples ( ! reflection ( a prism 7 discuss$1 art4 #ee1 ,fig4 #c1 p4 #bi4 ,illu/ration3 ,fig4 #ce4--,ord9>y prismatic compass4 ,illu/ration3 ,fig4 #cf4--,section ( ! same1 b ) mirror4 #adi4--,prismatic ,compasses are made f #b to #f in*es 9 diamet]4 ,! compass ne$le is sometimes made to c>ry a c>d dial = ! #b-;in* size2 = l>g] sizes ! r+ is n[ made uni=mly ( alum9ium4 ,! read+ ( ! compass r+ is effect$ by means ( a glass prism1 ,fig4 #cf1 ,p1 :i* is cut to #de ^u "o face & #ij = ! two o!rs1 "o #ij face be+ work$ convex1 s z to give magnify+ p[] simultane\sly ) reflection ( ! r+ at "r angles1 s t ! read+ ( ! compass appe>s to /& erect be=e ! us] ( ! in/rum5t1 & to be consid]ably magnifi$4 ,z ! read+ is made on ! side ( ! r+ ne>e/ ! obs]v]1 ! figures on ! r+ are engrav$ "r to left4 ,! prism is plac$ 9 a box1 ) a v]tical sight slit ,,ss ov] x1 :i* cuts a l9e ) ! c5tre ( ! top ( ! prism4 ,! box ) its prism moves upw>ds or d[nw>ds 9 a slid+ fitt+ ,,sl by means ( a ?umb nail /ud1 :i* adju/s ! prism until x is 9 exact focus ) ! divisions on ! r+4 ,! back ( ! prism-box has a h+e ,h1 s t ?is box may be clos$ d[n to ! level ( ! compass-box to r5d] x portable :5 out ( use4 ,on ! opposite side ( ! compass-box to t ^u :i* ! prism is plac$ a long v]tical w9d[ ,,sv is atta*$1 hav+ a c5tral hair plac$ s z to cut a direct l9e f ! slit ,,ss 9 ! prism-box across ! axis ( ! ne$le4 ,?is w9d[-piece is jo9t$ to turn d[n ^u ! face ( ! compass-box & simultane\sly to lift ! compass ne$le (f its c5tre by a "p ( x press+ ! out] end ( ! lift+ lev] ,l4 ,to prev5t too great a cont9uity ( ! oscillation ( ! compass ne$le & ! r+1 ?r\gh un/ead9ess ( ! h& 9 hold+ x1 a p9 is plac$ at ,s1 ?r\gh ! compass-box "u ! w9d[1 :i* c>ries a light spr+ ,b t j t\*es ! r+ lightly :5 ! p9 is press$ 91 & !reby br+s ! compass r+ to re/1 or fixes x = read+ ) "s degree ( c]ta9ty4 ,an op5 r+ "u ! prism-box is sometimes us$ = plac+ a piece ( ribbon ?r\gh x1 to atta* x to "s "p ( ! p]son to save dropp+ ! compass accid5tally :5 x is us$ 9 ! h&4 ,:5 ! in/rum5t is out ( use a metal cov] is provid$ to protect ! glass4 ,! in/rum5t is uni=mly c>ri$ 9 a lea!r case ) /rap to pass ov] ! %\ld]4 ,z ^! in/rum5ts are (t5 c>ri$ by milit>y surveyors1 !y are bett] made ( a /iff alum9ium alloy1 :i* makes ! in/rum5t less ?an half its ord9>y weight4 #aej4--;,additional ,p>ts commonly provid$ ) ! prismatic compass are a mirror & sun%ades1 %[n only 9 section ,fig4 #cf4 ,! mirror ,m is c>ri$ 9 a frame atta*$ ) a slid+ piece to ! w9d[1 ^u :i* x c be plac$ ei!r upw>ds or d[nw>ds4 ,x is jo9t$ ) a h+e s z to be set at any angle4 ,by reflection f ! mirror1 be>+s 9 azimu? are tak5 mu* above or bel[ ! horizontal plane4 ,sun-glasses are also provid$ 9 front ( ! prism1 :i* are us$ = tak+ ! sun's place ei!r ) or )\t ! mirror1 a s+le sun-glass be+ also us$ v com=tably = work+ t[>ds ! sun at all times4 ,! sun-glasses1 :i* are simply small1 d>k-col\r$ glass circles 9 frames1 are n %[n 9 ! engrav+4 #aea4--,to ,prep>e to take ,obs]vations ) ! ,prismatic ,compass4 ,aft] ! w9d[ & prism are op5$ out1 ! prism is adju/$ to read ! divid$ r+ %>ply :5 ! compass is ab\t level1 by rais+ or l[]+ ! prism ,p by pressure ( ! ?umb & =ef+] ( ! "r h& ^u ! /ud plac$ ^u ! prism slide fitt+1 %[n bel[ ,,sl1 until ! divisions appe> cle>4 #aeb4--;,9 ,us+ ! ,prismatic ,compass1 ! compass-box is held ) ! ?umb ( ! "r h& "u ! prism at ,,sl & ! =ef+] ^u ! /ud ,s4 ,! object :i* x is desir$ to obs]ve is sight$ ?r\gh ! slit ,,ss1 cutt+ ! left-h& side ( ! hair 9 ! w9d[ ,,sv1 :ile ! division :i* comes opposite ! read+ po9t at its edge by ! reflection f ! prism is not$4 ,! r+ :5 free oscillates = a "t1 b is easily br\ght to re/ = read+ by g5tly press+ ! p9 ,s ^u :i* ! =ef+] is plac$4 #aec4--,:]e objects are obs]v$ = tak+ _! be>+s above ! horizontal plane1 ! l5g? ( ! w9d[ w be suffici5t to take 9 a v]tical angle ( #bj to #cj2 b = su* altitudes x is necess>y to take v great c>e t ! compass is held level1 to get magnetic angles ev5 approximately true4 ,bel[ ! horizon1 angles c be obta9$ ) some:at great] c]ta9ty by means ( reflections f ! mirror4 ,altoge!r1 except = tak+ ne>ly horizontal angles1 or = v close "w 9 fill+ 9 aft] ! !odolite1 x is mu* bett] to h ! prismatic compass m\nt$ ^u a tripod /&4 ,) a /&1 :]e ! angle 9 azimu? is mu* above or bel[ ! horizontal plane1 x is bett] to h a small glass level1 describ$ fur!r on1 art4 #aha1 to place across ! compass :5 sett+ x up4 ,if ! compass r+ is v c>efully balanc$ across #ij to #bgj two bright wire po9ts may be plac$ inside ! compass-box1 level ) ! compass r+1 :i* w answ] = ! cross levell+4 #aed4--,/&s4--,! au?or has made a v simple & inexp5sive tripod /& = ! prismatic compass1 ! head ( :i* consi/s ( a ball & socket only1 clamp$ by a l>ge mill$-head screw4 ,an axis ?r\gh ! ball p]mits horizontal adju/m5t1 %[n 9 section1 ,fig4 #cg4 ,illu/ration3 ,fig4 #cg4--;,improv$ prismatic compass /&4 ,illu/ration3 ,fig4 #ch4--;,hut*9son's prismatic compass4 #aee4--;,hut*9son's ,prismatic ,compass1 ,fig4 #ch1 is n[ v g5]ally us$ by milit>y m54 ,9 ?is compass ! metal cov] is fix$ on ! top ( ! compass-box1 & a glaz$ op5+ is plac$ 9 ! cov]1 occupy+ ab\t "o-eigh? ( its area1 ne> ! prism4 ,?is op5+ gives suffici5t light to ! compass c>d to p]mit x to be easily read1 & ! loose cov] is disp5s$ )2 besides :i*1 ! cov] be+ fix$1 ?is1 z well z ! :ole in/rum5t1 may be made mu* light]1 :ile reta9+ equal rigidity = we>4 ,?is compass is n fitt$ ) %ade & mirror arrangem5ts z be=e describ$4 ,size1 #b in*es diamet]1 in* 9 ?ickness2 weight1 only #h oz4 9 brass2 #c oz4 9 alum9ium4 #aef4--;,capta9 ,burni]'s ,milit>y ,compass4--,?is portable compass is m g5]ally us$ on ! ,cont95t ?an o!r =ms4 ,x is g5]ally comb9$ ) a cl9omet]1 !re=e ! illu/ration is def]r$1 seq4 ) cl9omet]s4 ,! compass r+ is set up v]tical to ! plane ( ! ne$le1 & is read by an index po9t by means ( a cyl9drical l5s4 ,x has a pair ( sights =m$ ( a slit ne> ! eye-piece1 & a hair 9 ! w9d[ z 9 ! prismatic4 ,:5 ?is in/rum5t is held horizontally1 at ab\t a foot di/ance f ! eye1 ! sight l9e & ! index l9e read di/9ctly into ! graduations ( ! r+4 ,a lift] is provid$ to raise ! compass (f its c5tre1 z ) ! prismatic compass1 & a spr+ clut* to prev5t cont9uity ( oscillation4 ,x is adapt$ to be set up on a pla9 rod /&1 ! socket fitt+ to :i* is held 9 ! h& :5 x is us$ z a h& in/rum5t4 ,illu/ration3 ,fig4 #ci4--,sket*+ protractor = use ) prismatic compass4 #aeg4--,survey+ ) ! ,compass only4--,9 mod]n practice v little survey+ is p]=m$ ) ! compass1 except = sket* or explor+ maps & fill+ 9 details1 :]e9 ! prismatic compass is useful4 ,! magnetic ne$le 0 =m]ly mu* us$ = surface "w1 & dep5d$ ^u almo/ entirely = und]gr\nd "w2 b ?is has be5 f\nd practically 9 _m cases unsafe1 f ! unc]ta9ty ( magnetic v>iations1 local & o!r1 9 ! di/rict survey$4 ,m9+ compasses1 or dials1 z !y are t]m$1 are n[ 9 mod]n practice made ) means ( tak+ angles ) ! compass1 & indep5d5tly ( x4 ,?is subject w !re=e be def]r$ to a future *apt] on m9+ in/rum5ts4 #aeh4--;,9 ,plott+ ,milit>y ,sket* ,surveys f angles tak5 ) ! prismatic compass1 ! pap] employ$ is rul$ lightly all ov] ) p>allel l9es an in* or less ap>t4 ,! angles tak5 ) ! prismatic compass f #j to #cfj 7nor!rn z]o7 are set (f ) an ivory milit>y protractor1 :i* has l9es to correspond ) latitud9al l9es drawn ov] its face at #ij to its base1 s t ! protractor may be plac$ transv]se to any l9e drawn on ! pap] ) its c5tre 9 any position4 ,p>ticul>s ( ?is me?od are giv5 9 e detail 9 ,major ,jackson's ,c\rse ( ,milit>y ,survey+1 & 9 my "w on ,draw+ ,in/rum5ts4 ,! milit>y protractor is %[n ,fig4 #ci4 #aei4--;,= mak+ a sket* plan ) ! prismatic compass1 a v conv5i5t way is to use ! tee-squ>e1 ! upp] edge ( ! blade ( :i* repres5ts magnetic ea/ to we/1 ! upp] end ( ! bo>d magnetic nor? & ! l[] end s\?1 accord+ to ! read+ ( ! compass4 ,! be>+s tak5 f any />t+-po9t are set (f on ! plot by a semicircul> protractor ) its base re/+ along ! tee-squ>e4 ,! nor!rn angles are rais$ ) ! squ>e at ! left-h& side ( ! bo>d & ! s\!rn ) x at ! "r4 ,! di/ances f ! /ation = all be>+s are measur$ & set (f by scale4 #afj4--;,x is indiff]5t h[ _m /ations are tak5 by ! prismatic compass4 ,! measurem5ts 9 any direction may cont9ue all r\nd an e/ate1 & w be f\nd fairly correct if c>efully made1 z ! small p]sonal errors 9 read+ ! prismatic1 :i* may be plus or m9us1 t5d to correct ea* o!r on ! :ole1 & to tie up ! l9es4 #afa4--,! roll+ p>allel rule may replace ! tee-squ>e1 if x is ?\ght desirable to place ! plan 9 a direction o!r ?an t erect to magnetic nor? ) ! pap]1 or t x is inconv5i5t to use ! tee-squ>e4 ,9 ?is case a few p>allel l9es may be at fir/ drawn correctly across ! pap]1 at ab\t equal di/ances1 ) a %>p p5cil ,e4 to ,w4 = ref]5ces to reset ! p>allel rule at any position desir$4 ,illu/ration3 ,figs4 #dj1 #da1 #db1 #dc4--,pocket magnetic compasses4 #afb4--,pocket ,magnetic ,compasses4--,! subject ( compasses w sc>cely be complete )\t m5tion ( ! small pocket compasses :i* are s useful & univ]sal4 ,sev]al well-kn[n =ms are %[n 9 ! next illu/ration4 ,! squ>e =m %[n fir/1 ,fig4 #dj1 w be f\nd ! mo/ useful = v r\gh sket*+4 ,! edges may be sight$ = ! direction ( roads1 etc41 or ! box may be plac$ aga9/ a wall = tak+ ! magnetic direction ( a build+4 ,9 l mann] also ! compass-box may be laid on a draw+ & l9es drawn along by ! edges ( ! box to ! magnetic directions tak54 ,?is 9 mo/ cases is suffici5tly accurate = ar*itectural "w1 9 :i* ! exact direction is n g5]ally ?\ght to be important4 ,fig4 #da is a ,fr5* =m ( compass ) /ep read+ level ) ! upp] surface ( ! ne$le4 ,fig4 #db is an old ,engli% =m ) enamell$ dial1 ) lift] "u ! b[ ( ! h&le4 ,fig4 #dc is ! same make 9 a hunt] case4 ,9 ?is ! lift] rises ^u ! case be+ clos$4 ,illu/ration3 ,fig4 #dd4--,tr\gh =m ,egyptian compass4 #afc4--,! au?or has made a small pocket magnetic compass1 :i* is repres5t$ 9 ! illu/ration above4 ,! ne$le is plac$ 9 a long box4 ,x reads at its po9t into a s+le l9e :5 ! ne$le is exactly p>allel ) ! sides ( ! box4 ,! lid turns up endwise4 ,! ne$le is lift$ by clos+ ! box4 ,illu/ration3 ,fig4 #de4--,! au?or's "u slide = sett+ (f v>iation4 #afd4--;,9 a =m ( compass simil> to ! above1 ! au?or has add$ a ?9 slide to ! "u side ( ! box1 by means ( :i* ! magnetic v>iation may be adju/$1 z %[n ,fig4 #de4 ,?is slide moves out j ! am\nt ( magnetic v>iation1 ! /ud ,s be+ made conc5tric = ?is adju/m5t4 ,if ! slide box be made ( ivory a few useful scales may be divid$ ^u x4 ,! compass slips into a light lea!r case1 & is ! mo/ portable = its l5g? ( ne$le ( any compass made4 ,! edges ( ! box are us$ z direct+ l9es1 z above describ$ = ! squ>e =m4 ,! illu/rations %[ a compass made = ,great ,brita91 b a simil> in/rum5t is also made univ]sal4 ,9 ?is case ! box is a little wid]1 ) ! c5tre ( ! slide 9 ! middle1 s t ! magnetic v>iation c be set (f we/ or ea/4 ,a rid] also on ! ne$le enables x to be balanc$ 9 s\!rn latitudes4 ,illu/ration3 ,fig4 #df4--;,b>k]'s lum9\s compass4 #afe4--;,b>k]'s ,lum9\s ,compass1 ) float+ dial ( "m-(-pe>l1 "o-half ( ?is be+ engrav$ ) black figures & ! o!r half pa9t$ black ) ! figures left :ite1 p]mits magnetic direction to be obs]v$ 9 ! dusk & by moonlight4 ,^! compasses1 ,fig4 #df1 are mu* us$ by travell]s4 ,mr4 ,francis ,b>k] has also design$ a compass 9 :i* ! ne$le c>ries a b> coat$ ) lum9\s pa9t4 ,,footnote3 #b ,see ,phil4 ,trans4 #ahif1 vol4 #ahh1 ,map4 #i4 ,,*apt] ,,iv4 ,,levels--,,me?ods ,,( ,,asc]ta9+--,,level ,,tubes--,,manufacture--,,curvature-- ,,s5sitiv5ess-,,te/+--,,read+--,,circul> ,,levels--,,surveyors' ,,levels-- ,y-,,level--,,p>allel ,,plates--,,adju/m5ts ,,( ,y-,,levels--,,sugge/$ ,,improvem5ts--,,dumpy ,,level--,,tripod ,,/&s--,,adju/m5t ,,( ,,dumpy-- ,,collimator--,,improvem5ts ,,9 ,,dumpy ,,level--,,tribra* ,,head--,,diaphragms-- ,,cu%+',s ,,level--,,cooke',s ,,level--,,*eap ,,=ms ,,( ,,level--,,h& ,,levels-- ,,telescopic ,,level--,,reflect+ ,,levels--,,wat] ,,levels4 #aff4--;,a ,level ,plane is und]/ood te*nically to be a plane truly tang5tial to ! !oretical sph]oidal surface ( ! e>?1 z repres5t$ by any spot ^u ! mean surface ( ! ocean or ( /ill wat] free f local attraction4 ,! importance ( hav+ ! means ( con/ruct+ effici5t in/rum5ts t c be conv5i5tly employ$ to obta9 ! correct relative altitudes ( po9ts or /ations ^u ! e>?'s surface1 9 relation to su* a plane or datum1 c sc>cely be ov]rat$4 ,su* in/rum5ts are n only us$ = topographical surveys ( c\ntries1 b also 9 design+ & c>ry+ out public works adapt$ to ! local conditions ( natural incl9ation ( ! l& surface1 = railways1 dra9age1 irrigation1 canals1 wat]-works1 & o!r con/ructions4 #afg4--,! =ce con/antly at our comm& to enable u to asc]ta9 relative altitudes & to =m m5tally or graphically local level l9es on ! e>?1 is t ( gravity2 & x is only a "q 9 any case h[ ! action ( ?is =ce %all be employ$4 ,!re are f\r pr9ciples :i* we may accept z data = employ+ gravity1 ea* dep5d+ ^u a natural ph5om5on3--7#a7 ,! op5 upp] surface ( a liquid unaffect$ by curr5ts ( air1 or ! influ5ce ( solid objects 9 close proximity caus+ capill>y action1 or local attraction ( solid masses1 repres5ts a level plane4 7#b7 ,! l9e ( a plummet unaffect$ by curr5ts or lat]al attractions =ms a v]tical l9e to :i* ! level plane is ev]y:]e at "r angles4 7#c7 ,! atmosph]ic pressure1 f ! approximat$ equality ( its d5sity due to its weight 9 proportion to its height ov] limit$ areas1 gives pressure accord+ to its gravity--!re=e altitude or diff]5ce ( level relatively to less] pressure comp>$ ) a l[] datum4 ,?is pressure is measurable ) a b>omet] or o!r =m ( pressure gauge4 7#d7 ,! resi/ance to ebullition 9 a liquid is inv]sely proportional to ! weight or pressure ( ! arial fluid re/+ ^u its surface4 ,?is is measurable by ! temp]ature at :i* liquids boil "u v>y+ atmosph]ic pressures4 ,v>i\s in/rum5tal ref9em5ts h be5 discov]$ to r5d] ^! natural ph5om5a available 9 practical use = asc]ta9+ diff]5ce ( height4 ,! fir/ & mo/ exact me?od employ$ = ?is purpose1 by means ( ! liquid plane1 w be consid]$ 9 ?is *apt]4 ,! o!r me?ods w be def]r$ to lat] pages4 #afh4--;,9 tak+ ! level ( a liquid surface conta9$ 9 a vessel1 we h1 z j /at$1 to keep ?is surface free f ! di/urb+ influ5ce ( air curr5ts1 & to surr\nd ! surface ) equal conditions ( capill>y attraction1 or to make ^! conditions equal 9 ! direction 9 :i* we desire to asc]ta9 our level4 ,?is is f\nd practically to be be/ p]=m$ by means ( a seal$ glass tube1 9 :i* ! liquid w by gravitation naturally occupy ! l[] place1 & any air or light] fluid conta9$ !re9 ! space above ?is4 ,illu/ration3 ,fig4 #dg4--,level tube 7bubble74 #afi4--,level ,tubes1 or ,bubble ,tubes1 z !y are te*nically t]m$1 are us$ z a "p ( ne>ly all important survey+ in/rum5ts4 ,"o ( ^! is repres5t$ ,fig4 #dg4 ,! glass = ! con/ruction ( ^! tubes is drawn at ! glass-h\ses 9 l5g?s ( ab\t #f feet1 & may be ord]$ ( any desir$ size & sub/ance4 ,! tubes are drawn ( z ne>ly /raight & equal bore z possible4 ,!y are1 nev]!less1 f\nd to be1 :5 exam9$ aft] anneal+1 curv$ m or less 9 v>i\s directions at diff]5t p>ts ( _! l5g?s4 ,!y are f\nd also g5]ally to be slightly tap]+ f end to end & ( slightly unequal sub/ance4 ,9 ! manufacture ( level tubes p>ts ( ! tube are select$ ) approximately regul> longitud9al curvature1 & ^! p>ts are cut (f into ! requir$ l5g?s by a triangul> file dipp$ 9 spirits ( turp5t9e1 to be ready = ! future op]ations ( gr9d+1 seal+1 & divid+4 ,aft] ! tube is cut (f & c>efully exam9$ to get its mo/ concave int]nal surface upw>ds1 ?is is !n m>k$ by a te/ m>k1 ) ! flat ( a file1 ne> "o end = future "w & ref]5ce4 ,! gr9d+ ( ! inside ( ! glass tube to true curvature is p]=m$ by pass+ x ov] a brass m&rel or core1 :i* is employ$ to gr9d ! glass by means ( f9e em]y4 ,! core is turn$ slightly b>rel-=m to ! longitud9al curvature int5d$ = ! upp] surface ( ! f9i%$ tube4 ,x is made ( full ?ree-qu>t]s ! diamet] ( ! int]ior ( ! tube1 & a little long] ?an ! entire tube4 ,?is core is atta*$ by its ends to two /iff b flexible wires ( brass1 ab\t #h ,b4,w4,g4 = a tube ( #g in* diamet]1 & ^! wires are held firmly by _! ends 9 two vices1 s t ! core is slung1 z x 71 to p]mit a c]ta9 am\nt ( flexibility "u ! pressure ( ! h& us$ 9 gr9d+4 ,"s good mak]s d n use a m&rel core1 b only a /rip ( brass on ! m&rel1 ext5d+ ab\t #fj ( ! circumf]5ce4 ,9 ?is case ! /rip has to be correct$ = curvature dur+ ! gr9d+1 :i* plan is sometimes pref]r$ = c]ta9ty4 ,! gr9d+ ( a tube _c be comm5c$ ) co>se em]y1 su* z is us$ 9 ! gr9d+ ( l5ses1 z ! cut ( a co>se em]y w quickly split ! tube4 ,aft] ! glaze is remov$ !re is n s mu* risk1 s t a little "t may be sav$ by pass+ a curr5t ( hydr(luoric acid gas ?r\gh ! tube2 b m c>eful te/+ is requir$ aft]w>ds1 z ! cut ( ! gr9d+ tool is n s evid5t at sight :5 ! glaz$ surface is remov$4 #agj4--,! op]ation ( gr9d+ is v mu* ! same z t describ$ = l5ses1 p4 #ag4 ,! surface is requir$ to be trav]s$ 9 e direction longitud9ally & transv]sely1 :i* is effect$ z f> z possible by a twi/ ( ! h& alt]nately to ! "r & left4 ,! tube %\ld also be frequ5tly tak5 (f & turn$ end = end4 ,slight v>iations ( curvature are readily made by diff]5ces ( pressure ( ! h& on p>ts ( ! tube2 & a little coax+ is all[$ to get ! c5tre ( ! tube quick :]e ! tube is to be us$ = levell+ only1 & n = measur+ small angles1 s t 9 ?is case ! f9i%$ tube is slightly p>abolical4 ,! f9i%+ t\* is produc$ ) wa%-em]y4 ,! inside %\ld be left smoo? b n poli%$1 z ! slight r\ghness ( a f9e gr\nd surface assi/s ! capill>y action by caus+ bett] adhesion ( ! _s1 & gives a quick] run to ! bubble4 ,:]e ! tubes are requir$ ( a giv5 radius !y are te/$ frequ5tly1 dur+ ! gr9d+1 ^u ! bubble tri]1 by plac+ two corks 9 ! ends ( ! tube1 :i* is ne>ly fill$ fir/ ) wat] = r\gh trial1 & !n ) _s = f9al correction4 #aga4--,! ,bubble ,tri] is a b> or b$ #ab to #bj in*es long1 ) two ext5d$ feet end+ 9 po9ts at "o end1 & a micromet] screw at ! o!r1 ! po9t ( :i* is a re/+ foot1 !reby =m+ a tripod4 ,?is /&s on a ca/-iron or slate surface plate4 ,! micromet] screw has a f9e ?read1 & a l>ge head ) divisions ^u x to read seconds ( arc4 ,! tube is support$ on ! b> by two ,y's1 :i* are adju/able = di/ance ap>t1 accord+ to ! l5g? ( ! tubes to be tri$4 #agb4--,! ,s5sitiv5ess ( a ,level ,tube1 ! upp] curvature & gr\nd surface be+ equal1 dep5ds v mu* ^u ! capill>y action due to its int]nal diamet]1 ! l>g] tube1 f ! fre$om ( re/ra9t by capill>ity1 be+ ! m active4 ,z reg>ds ! ultimate settl+ to gravitation equilibrium1 p]haps !re is no diff]5ce1 b small tubes are sluggi% & take "t to "w4 ,! foll[+ are ab\t ! usual dim5sions ( ! int]ior ( s5sitive tubes--#h in*es #a in* diamet]1 #g in*es #i1 #f in*es #h1 #e in*es #g1 #d in*es #f1 #c in*es #e1 #b in*es #de1 #b in*es #d1 #a in*es #ce1 #a in* #c4 ,! l>g] ! volume ! great] ! expansion ( liquid ) heat2 ! long] ! tube ! less torsion x is liable to suff] f seal+1 s t if possible1 z expansion is a s]i\s defect1 x w\ld be bett] to h %ort tubes1 if ^! c\ld be seal$ )\t di/urbance ( curvature4 ,mu* %ort] tubes are us$ 9 ,am]ica ?an 9 ,great ,brita94 #agc4--,! ,curvature ( a ,level ,tube is work$ to radius accord+ to ! delicacy ( ! "w to be p]=m$ ) x aft]w>ds4 ,! radii ( curvature ( diff]5t level tubes us$ = sci5tific purposes v>y f ab\t #cj feet to #ajjj feet or m4 ,! radius ( any curve may be conv5i5tly measur$ by ! relation ( its v]s$ s9e to its *ord ( arc1 ! *ord be+ ! l5g? ( ! tube4 ,if ?is is fir/ calculat$ out1 a piece ( %ellac may be atta*$ by melt+ x d[n ^u ! c5tre ( ! edge ( a p>allel glass /raight-edge1 to repres5t by its ?ickness ! v]s$ s9e4 ,! spot ( %ellac may be br\ght to ! exact height requir$ f ! /raight-edge by fil+ & /on+1 at ! same "t tak+ its protub]ance by a callip] gauge provid$ ) v]ni] or micromet] to read #jja in*4 ,! v]s$ s9e ( a giv5 radius is =m$ = a giv5 *ord-- v]s$ s9e rad - 7rad#b - 7 *o7#b74 #agd4--,! g5]al in/ruction1 h[ev]1 giv5 to ! mak] is ! di/ance ( run ( ! bubble t is requir$ to give seconds or m9utes ( arc2 & p]haps ?is is aft] all ! be/ te/ = accuracy ( ! tube :i*1 l all o!r articles 9 glass submitt$ to ! process ( gr9d+1 is subject to a c]ta9 am\nt ( local error4 ,by ?is me?od ! local error is discov]$ by te/+ ) ! bubble tri]4 ,:5 ! run is giv51 ! radius ( ! curve ( ! tube may be f\nd if desir$ by ! use ( a common multipli]1 z foll[s1 v approximately-- ,arc equal to radius express$ 9 m9utes1 #cdcggdfgg4 seconds1 #bjfbfdhjfbe4 ,! run ( a good s5sitive tube is frequ5tly made #a_/cj in* to ! second1 "h 7omitt+ decimals7-- arc sec 7#bjfbfdh7 #a_/cj in* #egc feet radius ne>ly4 ,= sci5tific purposes a millimetre run p] second is commonly us$1 !n-- arc sec 7#bjfbfdh7 #jja metre #bjfbfd metres radius or #fhj feet ne>ly4 ,= an ord9>y #ab-;in* dumpy level ! tube is divid$ into m9utes at ab\t #a_/aj in* ap>t1 radius #bh to #cj feet2 = a s5sitive #ad-;in* ,y-level ( good con/ruction ! same divisions may repres5t five seconds1 radius ( bubble tube ab\t #agj feet4 #age4--,! ,divisions ^u ,ord9>y ,level ,tubes are made aft] ! tube is f9i%$1 b ) ! highly s5sitive ones ! divisions are made fir/4 ,! run is tak5 f t5 to ?irty divisions on ea* side ( ! c5tre ( ! tube1 :]e x is lightly m>k$ ) a m>k+ diamond4 ,^! spaces are !n equally subdivid$ & et*$ 9 ) hydr(luoric acid or m>k$ ) a h>d /eel edge dipp$ 9 turps4 ,if fur!r ref9em5t be requir$1 ! errors ( run 9 relation to ! divisions are tabulat$ f ! te/+ ( ! tube ) ! bubble tri]4 ,a less c>eful me?od is employ$ by "s mak]s ( leav+ ! level tube undivid$ & fix+ an indep5d5t metal or ivory scale ov] x4 #agf4--,level tubes are g5]ally fill$ ) pure alcohol = ord9>y purposes2 = trade purposes ) me?ylic alcohol1 :i* is mu* *eap]4 ,= v delicate tubes sulphuric e!r or *lor(orm is us$4 ,! s5sitiv5ess ( ! bubble dep5ds v greatly ^u ! mobility ( ! liquid ) :i* x is fill$1 & to ! quality ( adhesion ( ! liquid to ! glass4 ,! relative mobility ( ! above-m5tion$ liquids is f\nd by delicate te/s ) ! bubble tri] = small di/ances "u ! microscope at a temp]ature ( #fj ,fahr4 ,tak+ wat] z #ajj3--we f9d comm]cial me?ylic alcohol #bb1 absolute alcohol #ac1 sulphuric e!r #e1 *lor(orm #c1--t is1 = equal small runs tak5 9 #ae seconds ( "t4 ,all bubbles appe> to be m or less affect$ by temp]ature1 p>ticul>ly :]e ! _s is n ne>ly absolute4 ,9 ! high] temp]atures ! bubbles are m active4 ,! objection to *lor(orm1 :]e x is likely to be subject to great *anges ( temp]ature1 & :]e !re is no provision made = regulat+ ! size ( ! bubble--! means ( do+ :i* w be pres5tly discuss$--is t its expansion f heat is s great t x is v liable to bur/ its tube4 ,x c !re=e only be us$ ) ord9>y seal$ tubes :]e ^! are small & /rong4 ,sulphuric e!r has ! same fault1 b 9 a less] degree4 #agg4--,! seal+ ( gr\nd tubes requires ! skill ( a v exp]i5c$ glass-bl[]1 & is a te*nical matt] on :i* no writt5 in/ructions w\ld be ( value "u any conditions4 ,a little /ra9 is unavoidably put ^u ! tube 9 seal+ ) ! bl[-pipe1 s t ! curvature to :i* x is work$ is m or less di/urb$4 ,= ?is reason level tubes :i* are requir$ to be ( ! highe/ degree ( accuracy are sometimes left z !y are gr\nd1 & clos$ at ! ends by small discs ( glass groov$ to ! end surfaces4 ,^! are fix$ on ) glue1 & :5 ! glue is set are b\nd ov] ) silk & f9ally v>ni%$2 b ?is plan is mu* too delicate = in/rum5ts = use 9 ! field4 ,illu/ration3 ,fig4 #dh4--;,colonel ,/range's level tube4 #agh4--;,colonel ,/range's ,level ,tube4--,^! tubes1 ,fig4 #dh1 are bl[n ) an outw>d bead at ea* end ( ! tube1 two outw>dly screw$ coll>s1 ,f1 be+ fir/ plac$ ov] ! tube be=e ! bl[+4 ,! tube is !n gr\nd to curvature4 ,a plug1 ,s1 is =m$ = ea* end ( ! tube f a plano-convex l5s1 gr\nd to a bevel on ! plano side1 & also gr\nd into ! end ( ! tube z a /opp]4 ,a cap1 ,c1 is screw$ ov] ! end ^u ! coll>4 ,! spr+9ess ( ! cap keeps ! /opp] always tight4 ,z !re is no bl[-pipe us$ aft] ! gr9d+1 ! tube rema9s con/ant z x is gr\nd1 or x c be adju/$ by gr9d+ to any desir$ s5sitiv5ess4 ,?is cap1 = security1 is bett] cov]$ ) silk ti$ ov] x1 & aft]w>ds well v>ni%$4 ,9 ?is class ( tube !re is always a little risk ( evaporation4 ,! sy/em is n adapt$ to in/rum5ts to be us$ 9 ! op5 air4 #agi4--;,*amb]$ ,level ,tubes4--,z ! run ( a bubble v>ies slightly ) its size1 = exact purposes & extreme climates x is v desirable to be able to adju/ ! size ( ! bubble to ! surr\nd+ temp]ature1 s t x %all be kept at ab\t equal dim5sions = all measurem5ts made ) x4 ,?is becomes p>ticul>ly important :]e *lor(orm is us$1 f ! expansion be+ v great4 ,a g5]al way ( do+ ?is is to h a /opp] gr\nd into "o end ( ! tube1 :i* is itself a small bottle1 on ! "u side ( :i* a hole is gr\nd1 s t by turn+ ! tube ov] & rais+ x m or less1 any am\nt ( ! highly r>efi$ air x conta9s may be tak5 to =m ! bubble t may be desir$4 ,! /opp] is fix$ ) ?9 glue4 ,! g5]al con/ruction is %[n bel[1 ,fig4 #di4 ,( c\rse :]e su* a tube is us$ !re mu/ be means ( tipp+ & turn+ ! in/rum5t 9 :i* x is fix$ ov]1 or ! bubble itself mu/ h sep>ate fix+s4 ,! portability ( a surveyor's level admits readily ( ! necess>y tipp+2 ) !odolite levels at "r angles to ea* o!r ^u ! v]ni] plate x w\ld be impossible4 ,illu/ration3 ,fig4 #di4--;,bubble ) supplem5tal air-*amb]4 ,illu/ration3 ,fig4 #ej4--;,colonel ,scott's pat5t protect$ bubble4 #ahj4--;,extra ,/rong ,level ,tubes4--,colonel ,scott's v +5i\s device ( enclos+ a level tube )9 ano!r tube ( ?or\ghly anneal$ glass w be f\nd valuable 9 all cases :]e ! tube is mu* expos$1 or :]e x is difficult aft]w>ds to procure a new tube 9 ! case ( accid5t4 ,^! tubes are at pres5t only made by ! au?or = ,scott's telescopic gun-sights1 :i* are ne>ly l small !odolites4 ,! level tube1 ,fig4 #ej1 is made z /\t z possible to be s\ndly seal$ aft] fill+4 ,x is !n enclos$ 9 an anneal$ tube1 ,,cc1 ( ab\t #jh to #ab in* 9 ?ickness1 ! int]space betwe5 ! two tubes be+ fill$ ) ,canada balsam4 ,x is !n plugg$ ) ela/ic m>9e glue1 ,,kk & cem5t$ ov] ,,pp4 ,! anneal$ tube is ( great /r5g?1 s t ! complete nak$ tube ?us =m$ w be> dropp+ on ! gr\nd1 & also :5 atta*$ to a l>ge gun w be> ! viol5t vibration ( fir+ )\t injury4 ,illu/ration3 ,fig4 #ea4--;,artificial horizon level4 #aha4--,! ,level ,tube may =m a ,complete ,in/rum5t 9 itself4--,9 ?is case ! l[] surface is gr\nd to a flat plane to re/ on any plane surface4 ,?is level is g5]ally conta9$ 9 a small pocket case1 & is mo/ conv5i5t = adju/+ in/rum5ts to level4 ,x is commonly us$ ) ! black glass artificial horizon1 to be describ$4 #ahb4--,m\nt+ ,tubes4--,level tubes :5 appli$ to in/rum5ts are g5]ally m\nt$ 9 brass cov]+ tubes4 ,small level tubes "u #b in*es are conv5i5tly m\nt$ 9 su* tubes ) a fix+ ( slak$ pla/] ( ,p>is ins]t$ at ea* end ( ! brass tube4 ,l>g] level tubes %\ld be b\nd r\nd ) ?9 pap] pa/$ r\nd ! ends1 :i* is all[$ to get q dry1 to be aft]w>ds fitt$ to ! brass tube ) a file4 ,fitt$ 9 ?is mann] ! tubes admit ( adju/m5t to ! diff]5ce ( expansion ( ! metal & glass by *ange ( temp]ature )\t di/ortion4 ,!re is no objection1 h[ev]1 to ?or\ghly fix+ "o end ( ! tube ) pla/] if ! o!r be left free1 & ?is is p]haps advisable = portable in/rum5ts4 ,x is conv5i5t 9 m\nt+ level tubes to place :ite glaz$ pap] "u ! bubble to reflect ! light t passes ?r\gh x to ensure bett] obs]vation4 #ahc4--;,9 ,fix+ ,undivid$ ,level ,tubes1 or replac+ !m 9 in/rum5ts1 x is important to obs]ve t ! side ) ! te/ m>k1 :i* is a small gr\nd facet1 %\ld be plac$ on ! top4 #ahd4--;,9 ! ,use ( ,level ,tubes g5]ally1 x is n well to h !m ( great] s5sitiv5ess ?an ! g5]al con/ruction ( ! in/rum5t ^u :i* !y are plac$ p]mits4 ,?us ! c5tre ( a surveyor's level t may be "u con/ant /ra9 f ! unavoidable inequality ( ! pressure ( p>allel plate screws1 w appe> nev] to rev]se prop]ly if x has a v s5sitive bubble1 ! cause ( ! irregul>ity be+ entirely due to ! di/ortion f ! /ra9 on ! v]tical axis ( ! in/rum5t4 ,! same irregul>ity occurs 9 a less] degree ) ! ,y's ( a !odolite1 :]e ^! & ! coll>s become corrod$ by exposure4 ,! optician (t5 gets an undue am\nt ( cr$it = p]fect+ su* in/rum5ts :5 he has m]ely replac$ ! s5sitive bubble by a dull "o--t is by do+ :at is really 9 ?is case ! be/ = ! in/rum5t4 #ahe4--,:5 an in/rum5t t dep5ds entirely ^u ! level = its possible work+ is to be us$ abroad1 an extra tube %\ld be tak51 z ! level tube is v g5]ally m expos$ & is m delicate ?an any o!r "p ( ! in/rum5t4 ,! tube may n only be accid5tally fractur$ ) a slight b[1 b ev5 ! heat ( ! sun's rays w sometimes bur/ x4 #ahf4--,read+ ! ,bubble4--,! exact position ( ! capill>y concave surface ( ! _s 9 ! tube is liable to deceive ! obs]v] by ! diff]5ce ( refraction & reflection x gives1 :e!r ! light is t[>ds ! "r or left h&4 ,to avoid ?is cause ( error x is bett]1 9 sunlight1 to hold a piece ( :ite pap] at a %ort di/ance ov] ! end ( ! bubble dur+ ! obs]vation tak5 ( its t]m9al read+ into ! divid$ scale on ! tube4 ,x is also important to note t ! obs]v] %\ld /& at "r angles to ! tube to see ! position exactly :]e ! upp] capill>y l9e ( ! _s cuts1 z ! tube itself refracts ! light unequally4 ,x is n at all difficult to read ! bubble if ! obs]v] /& ov] x2 b g5]ally1 z x is m\nt$ ^u an in/rum5t1 x is at ! height ( ! eye4 ,9 ?is position ! holl[ surface r\nd ! bubble1 caus$ by ! adhesion ( ! liquid to ! sides ( ! glass tube1 reflects ! light 9 a mann] t ! holl[ may be tak5 = ! end ( ! bubble1 & a false read+ made4 ,x is bett] if possible to take ! conv5i5t side read+ fir/1 & aft]w>ds get a glance at ! upp] surface read+ = c]ta9ty4 ,9 "s cases ?is may be mu* assi/$ by ! employm5t ( a small mirror ( ab\t ! size ( a spectacle eye1 :i* is c>ri$ op5 9 ! pocket1 or1 z ! au?or has made x1 x may close 9 a horn case ) a pocket l5s1 z 9 ! ,fig4 #eb %[n bel[4 ,c %ea?1 ,m mirror1 ,l l5s4 ,illu/ration3 ,fig4 #eb4--,pocket l5s & mirror4 #ahg4--;,circul> ,levels h be5 made t5tatively = a long p]iod4 ,!y consi/ ( a work$ concave l5s fitt$ into a brass cell ) indi>ubb] seat+1 ! glass be+ secur$ by burni%+ ov] a bezel4 ,?is con/ruction answ]s v well :5 new1 b ! _s ! level conta9s is c]ta9 to evaporate sl[ly "u e possible c>e4 ,mr4 ,j4 ,j4 ,hicks has pat5t$ a h]metically seal$ circul> level1 9 :i* he has succe$$ 9 work+ ! upp] surface ( ! glass to curvature4 ,^! levels1 ( c\rse1 are n subject to evaporation1 & are v useful & portable = approximate levell+--z = plane tables1 cam]as1 etc4 ,illu/ration3 ,fig4 #ec4--;,hicks' pat5t circul> level4 #ahh4--,surveyors' ,levels1 ( :i* !re are _m =ms1 consi/ ess5tially ( a telescope ) a diaphragm at ! mutual foci ( ! objective & ! eye-piece1 ! axis ( ! telescope be+ plac$ 9 a direction truly p>allel ) ! cr[n ( a s5sitive level tube4 ,! telescope ) its level is m\nt$ ^u metal frame-"w1 c>ri$ up f a v]tical axis ^u :i* ! telescope re/s4 ,! v]tical axis is adju/able 9 relation to ! axis ( ! telescope1 s t !y may be br\ght p]fectly p]p5dicul>1 ! "o to ! o!r4 ,! :ole in/rum5t is also adju/able to a position ( v]ticality ( its c5tral axis1 & ! horizontality ( ! telescope 9 relation to ! surface ( ! e>? 9 :at is t]m$ ! sett+-up ( ! in/rum5t2 s t :5 x is set up 9 ?is position levels may be tak5 f x 9 any horizontal direction f "o po9t ( obs]vation1 by rotation ( ! telescope ab\t ! v]tical axis4 ,hav+ ^! ess5tial objects 9 view 9 ! con/ruction ( ! level1 ! =m ( ! in/rum5t may be v>i$ z to details accord+ to ! me*anical skill & ta/e ( ! mak] & ! special dem&s ( ! civil eng9e]4 #ahi4--;,9 ! design ( a surveyor's level v important consid]ations are3--,t ! metal %\ld be s di/ribut$ t e "p is z light z possible1 consi/5tly ) suffici5t solidity to take a mod]ate am\nt ( accid5tal r\gh usage1 & ensure fre$om f vibration2 t ! :ole /ructure %\ld be 9 equilibrium ab\t its v]tical axis :5 ! telescope is ext5d$ at mean range1 t is1 at ab\t ! focus ( ?ree *a9s--?is is a quality (t5 neglect$2 t !re %\ld be suffici5t light 9 ! telescope1 & t x %\ld possess a firm & durable /&4 ,e =m ( level %\ld embrace ^! qualities4 #aij4--,! ,olde/ ,=m ( ,surveyor's ,level is t t]m$ ! ,y-level1 s nam$ f ! telescope be+ support$ 9 ,y-=m$ be>+s4 ,?is in/rum5t 0 orig9ally inv5t$ by ,jona?an ,sisson1 a lead+ in/rum5t mak] ( ! #ah? c5tury4 ,x 0 mu* improv$ & br\ght ne>ly to its pres5t /ate ( p]fection by ,ramsd51 to :om practical opticians owe s mu* = _m advancem5ts ( _! sci5ce1 & to 8 lib]al publication !re(4 ,?is in/rum5t is n[ v little us$ 9 ,great ,brita92 b x /ill ma9ta9s its orig9al position1 to a c]ta9 ext5t1 on ! ,cont95t & 9 ,am]ica4 ,9 ! eyes ( ! optician x is /ill ! mo/ p]fect level1 possess+ all ! in/rum5tal ref9em5ts ( adju/m5t he c desire4 ,! reasons = its p>tial ab&onm5t by ! pr(ession w be discuss$ fur!r on4 #aia4--,! ,y-,level 9 a mod]n =m is repres5t$ 9 ! engrav+ bel[1 ,fig4 #ed4 ,! ,y's are %[n at ,,yy edgewise4 ,!y are support$ by /&>ds ,,sr ^u ! limb ,l4 ,! telescope is surr\nd$ by two coll>s :i* are sold]$ ^u x at positions exactly correspond+ ) ! ,y's4 ,! coll>s are turn$ p]fectly cyl9drical & p>allel on ! surface ) ! axis ( ! telescope1 & gr\nd 9 a gauge-plate to exact size s t ! telescope may be turn$ end = end 9 ! ,y's )\t alt]+ ! l9e> direction ( its axis 9 rev]s+ x4 ,! telescope is held f %ift+ longitud9ally 9 its ,y's by a pair ( flanges plac$ on ! inside ( ! coll> pieces4 ,illu/ration3 ,fig4 #ed4--,surveyor's ,y-level4 #aib4--,! ,y's are erect$ ^u ! limb1 to :i* !y are ea* fix$ firmly by a clamp+ nut ,r at "o end1 & a mill$ head clamp at ,m4 ,! telescope is held d[n by /rap pieces1 ea* ( :i* has a jo9t at "o end & a loose p9 at ! o!r1 ,,pp4 ,! p9 is secur$ f dropp+ :5 out ( use by a piece ( cord atta*$ to a "p ( ! in/rum5t & to a loop ?r\gh its head4 ,at ! top ( ! inn] side ( ! /rap-piece "u ,,yy a piece ( cork is ins]t$ 9 a cave4 ,! cork by its ela/icity keeps an equal b light pressure ^u ! coll> ( ! telescope4 ,x w be se5 t by ! above plan ( hold+ ! telescope1 x is s f> free t x may be revolv$ on its axis1 by :i* p]fect adju/m5t ( ! diaphragm to ! axis ( ! in/rum5t may be made 9 any direction4 ,illu/ration3 ,fig4 #ee4--,section ( p>allel plate & v]tical axis--arrangem5t ( ,y & o!r levels4 #aic4--,p>allel ,plates z a mode ( adju/m5t ( ! v]tical axis w be fir/ describ$1 z !y pres5t ! olde/ =m ( sett+ up adju/m5t4 ,! v]tical axis ( ! ,y-level 0 =m]ly c>ri$ tap]+ d[nw>ds1 & ! upp] p>allel plate 0 plac$ at ab\t ! c5tre ( ! socket4 ,"u ?is con/ruction ! socket 0 m liable to /ra9 f ! use ( ! p>allel plate screws4 ,x is m g5]al n[ to con/ruct ! axis z repres5t$ 9 ! illu/ration above1 ,fig4 #ee1 = ,y & o!r levels ) p>allel plates4 ,?is con/ruction also r5d]s ! in/rum5t m portable1 z ! p>allel plates & axis may be deta*$ & lie clos] 9 ! case2 ! plan is nev]!less op5 to _m risks1 :i* w be ref]r$ to 9 discuss+ a ?ree-screw arrangem5t4 ,! g5]al con/ruction is %[n 9 ! figure1 ( :i* ! left-h& side is a half-section4 ,a is a screw by :i* ! p>allel plates are atta*$ to ! limb ( ! in/rum5t2 ,m a l>ge mill$ head1 by means ( :i* ! screw c be br\ght up firmly to its coll>2 ,,ss ! socket :i* is gr\nd to fit ! cone ,c2 ,c =ms a "p ( ! upp] p>allel plate ,,up2 ,b a ball p9 :i* screws firmly into ,c2 ,,lp l[] p>allel plate1 "p ( :i* =ms ! ball socket1 s t ! :ole in/rum5t rocks ab\t ! ball ,b z a c5tre1 by ! action ( ! p>allel plate screws ,,ps2 ,b female screw = fix+ ?is "p1 :i* is call$ altoge!r ! p>allel plates1 to ! tripod head4 ,a clamp+ screw is sometimes plac$ ^u ! axis = sl[ motion4 ,! p>allel plate screws are tapp$1 t is1 h female ?reads cut into ! upp] plate ,,up1 & _! po9ts press ! l[] p>allel plate ,,lp at c]ta9 po9ts1 !re be+ a /op-piece plac$ r\nd ! po9t ( "o screw to prev5t rotation4 ,! pressure ^u ! screws c be increas$ z desir$ by means ( ! mill$ heads1 & ! in/rum5t made rigid 9 proportion2 b x is v undesirable t ! pressure %\ld be great] ?an t j necess>y to support ! in/rum5t firmly1 z x is easy by ! p[] ( ! screws to di/urb ! figure ( ! axis & !reby d]ange x4 ,! diaphragm ( ! telescope ( ! ,y-level is g5]ally webb$ ) pla9 cross webs4 ,! diaphragm & webs 7 describ$ arts4 #ii to #ajf4 #aid4--,! ,sett+-up ( ! ,y-,level is necess>y to be und]/ood be=e ! in/rum5t c be adju/$4 ,! same description :i* answ]s = ! sett+ up = adju/m5t w also answ] = ! sett+-up ( ! in/rum5t 9 ! field = actual "w4 ,9 ?is description x w be conv5i5t1 !re=e1 to consid] ! in/rum5t z be+ 9 ?is case 9 adju/m5t z x leaves ! h& ( ! mak]4 ,! aft] adju/m5ts w be pres5tly tak5 z f ! orig9al /ate ( ! in/rum5t1 z ! mak] has to d !m 9 ! fir/ in/ance4 ,practically1 ! civil eng9e] has only to make slight diff]5tial adju/m5ts at any "t1 z an in/rum5t1 by ! solidity ( its con/ruction1 w reta9 ! g5]al adju/m5t ne>ly1 ^u :i* fur!r adju/m5ts take m ! nature ( f9al corrections1 :i* become necess>y only f accid5tal causes4 #aie4--,sett+-up ( ! ,y or o!r ,level ) ,p>allel ,plates4--,! tripod /& is op5$ out s t ! legs /&1 if on level gr\nd1 incl9$ t[>ds ! c5tre ( ! in/rum5t at an angle ( ab\t #gj to ! horizon4 ,! toes ( ! legs are ea* sep>ately press$ into ! gr\nd suffici5tly to make ! in/rum5t /& q firmly4 ,! in/rum5t is !n tak5 f its case & screw$ d[n tightly ^u ! tripod head4 #aif4--,! ,eye-piece is ,adju/$1 art4 #ajh1 by slid+ x g5tly 9 & out until ! webs c be se5 mo/ di/9ctly4 ,on a bright day a :ite pocket-h&k]*ief may ) advantage be ?r[n s+ly ov] ! object-glass to prev5t any confusion f objects 9 ! field ( view dur+ ! focuss+ ( ! eye-piece4 ,= ! sett+-up adju/m5t ( ! telescope1 x is br\ght 9 position to lie directly ov] "o pair ( p>allel plate screws1 ,fig4 #ee1 ,,ps1 ,,sp4 ,illu/ration3 ,fig4 #ef4--;,diagram plan ( p>allel plate screw mill$ heads4 #aig4--,! mill$ heads only ( ^! screws are repres5t$ 9 plan 9 ! diagram ,fig4 #ef1 aa be+ ! opposite pair ov] :i* ! telescope w be assum$ to be at fir/ plac$4 ,! level tube is n[ br\ght to adju/m5t by br++ ! bubble to ! c5tre ( its run by means ( ! p>allel plate screws aa1 by tak+ ! mill$ heads ( ^! screws1 "o betwe5 ! ball ( ! ?umb & =ef+] ( ea* h&1 & roll+ !m simultane\sly ! "o 9 "o direction & ! o!r 9 ! rev]se4 ,?is action tips ! axis ( ! telescope 9 "o direction or ! o!r4 ,?us by ! screws be+ roll$ inw>ds1 z %[n by ! direction ( ! arr[s 9 ! diagram1 ! left-h& side ( ! in/rum5t w\ld be rais$4 ,if turn$ ! rev]se way1 ! "r h& end w\ld be rais$4 ,! opposite end1 f t to :i* ! bubble runs1 always requires to be rais$4 ,:]e ! gr\nd is r s(t1 adju/m5t :5 ne>ly correct may be made p>tially by press+ d[n "o or o!r ( ! legs2 9 ?is case ! telescope %\ld be plac$ p>allel ) ! toe ( ! leg :i* is press$ d[n & ! axis ( ! in/rum5t4 #aih4--,:5 ! level tube is adju/$ ov] ! screws aa x is !n plac$ ov] bb & adju/$ 9 a simil> mann]1 return+ aga9 to ! position aa = f9al adju/m5t4 ,:5 ! level is 9 p]fect adju/m5t ! bubble %\ld /& 9 ! c5tre ( its run 9 mak+ a complete circuit ( ! horizon by rotation ( ! in/rum5t ^u its v]tical axis4 #aii4--;,9 & dur+ ! sett+-up adju/m5t x is mo/ important t ! screws %\ld n be made tight en\gh to cause1 by _! pressure ^u ! p>allel plates1 di/ortion ( ! v]tical axis4 ,%\ld ?is occur1 ! in/rum5t w n level 9 all positions by ! same sett+4 ,! action ( ! screws also1 f ! great ela/icity ( ! metal1 %\ld di/ribute ! pressure ab\t equally betwe5 ! opposite pairs aa & bb4 ,! difficulty ( accompli%+ ?is ) c]ta9ty makes ano!r =m ( adju/m5t1 ) ?ree screws only1 pref]able = sett+-up1 :i* w be consid]$ fur!r on4 ,:]e ! in/rum5t is set up = use1 if ! adju/m5t ( ! bubble be fairly correct to ! c5tre ( its run1 ! read+ ( ! /aff may be sight$ & ! telescope br\ght to true focus ^u x by mov+ its mill$ head until ! divisions ( ! /aff are z %>p z possible1 & !n mov+ ! eye upw>ds & d[nw>ds to be sure !re is no error ( p>allax1 art4 #aji4 ,aft] ?is ! f9al adju/+ ( ! bubble %\ld be made1 not+ p>ticul>ly t !re are ! same numb] ( divisions 9 its run on ea* side f ! c5tre if x is a divid$ bubble4 #bjj4--;,adju/m5t ( ! ,axis ( ! ,telescope 9 true p>allel direction ) ! p]iph]y ( its support+ coll>s 9 its ,y's4 ,?is is p]=m$ entirely ) ! f\r cap/an-head$ screws :i* adju/ ! diaphragm1 "o ( :i* is %[n1 ,fig4 #ed1 ,c4 ,hav+ ! adju/m5t ( ! eye-piece 9 focus = ! webs 9 ! mann] describ$1 arts4 #ajh1 #aji1 ! object-glass focuss$ ^u a di/ant di/9ct small object or m>k1 & )\t p>allax1 ! in/rum5t :i* c>ries ! telescope is !n exactly adju/$ to make ! int]section ( ! webs cut ! m>k4 ,! telescope is n[ turn$ half r\nd on its axis1 s t ! l[] "p becomes ! upp]1 & obs]vation is aga9 made ( ! di/ant small object or m>k4 ,if ! same int]section ( ! webs falls on ! same po9t ( ! object1 ! collimation adju/m5t is p]fect4 ,if x does n d s1 ! upp] cap/an-head$ screw at ,c1 or ! "u opposite "o1 is loos5$ by means ( ! small p9 provid$ ) ! in/rum5t1 & ! opposite screw tight5$ until ! webs are br\ght ov] a po9t situat$ half-way betwe5 ! po9ts cut by ! fir/ & second obs]vation4 ,! telescope is aga9 direct$ to ! po9t fir/ obs]v$1 & ! adju/m5t *eck$ to see if x has be5 done correctly1 t is1 if ! level rev]ses1 cutt+ ! same po9t1 or :e!r x requires fur!r adju/m5t by ! same process z be=e4 ,! o!r web ( ! diaphragm1 at "r angles to ! fir/1 is adju/$ 9 a simil> mann]1 b ) ! o!r pair ( cap/an-head$ screws4 #bja4--;,x is sometimes inconv5i5t to adju/ out ( doors3 ?is may be p]=m$ v well indoors4 ,by daylight a small cross may be made ) ink on a %eet ( :ite writ+-pap] = ! sight+ object1 :i* %\ld be plac$ at z great a di/ance z conv5i5t1 say #bj or #cj feet4 ,by night a p9-hole may be made ?r\gh a piece ( pap] & a c&le or a lamp be plac$ beh9d x4 #bjb4--;,adju/m5t ( ,v]tical ,axis4--,= ?is ! eye-piece is fir/ br\ght to focus on ! webs4 ,! telescope is !n plac$ directly ov] "o pair ( p>allel plate screws opposite ea* o!r1 & ! in/rum5t is levell$4 ,! ,y's are !n op5$ out2 & ! telescope is direct$ s t ! int]section ( ! webs cuts or cov]s any di/9ct small m>k ^u a di/ant object1 or pref]ably ^u ! c5tre read+ ( a foot l9e ^u a levell+ /aff4 ,!re is no objection to adju/+ slightly to ?is by ! p>allel plate screws1 z ?is adju/m5t is indep5d5t ( ! level ( ! in/rum5t4 ,! telescope is !n tak5 out ( its ,y's & is turn$ end = end & replac$4 ,! telescope is n[ turn$ half a revolution on its v]tical axis1 & ! webs are aga9 br\ght to read on ! /aff1 if "o is us$4 ,if !y n[ fall ^u ! same spot or foot l9e1 ! v]tical axis is p]fectly p]p5dicul> to ! axis ( ! telescope 9 ?is direction4 ,if ! webs d n fall ^u ! fir/ read+ or po9t1 ! am\nt ( diff]5ce ( read+ is record$ & ?is space is bisect$2 s t n[1 if ! telescope be adju/$ by ! mill$ head ,m1 at its be>+s ^u ! limb ^u :i* x is support$1 = ! webs to cut ! bisection1 ! axis w be p]fectly p]p5dicul> 9 ! direction ( its be>+ socket4 ,! same process mu/ n[ be repeat$ ) ! telescope plac$ at "r angles to its fir/ position1 t is by br++ x ov] ! o!r pair ( p>allel plate screws :i* 7 n us$ at fir/4 ,!re is at all times a c]ta9 am\nt ( di/urbance ( ! in/rum5t due to h&l+ x2 x is !re=e necess>y to repeat ! :ole ( ! above process until ! in/rum5t rev]ses 9 any direction1 b ?is f9al adju/m5t is bett] def]r$ until ! adju/m5t ( ! level tube1 to be next describ$1 has be5 made4 #bjc4--;,adju/m5t ( ! ,level ,tube4--,! telescope is plac$ z be=e ov] an opposite pair ( p>allel plate screws1 & ^! are adju/$ until ! bubble is 9 ! c5tre ( its run4 ,! telescope is !n turn$ half a revolution1 s t x is plac$ ov] ! same pair ( screws 9 ! rev]se direction1 & ! displacem5t f ! bubble f ! c5tre is n[ not$4 ,! cap/an-head$ bubble screws at ! end ( ! level ,b are !n adju/$ to "o-f\r? ( ! diff]5ce obs]v$1 & ! p>allel plate screws are adju/$ = ! o!r f\r?1 s t by ^! two adju/m5ts ! diff]5ce ( ! run 9 ! two positions is bisect$4 ,! same process is repeat$ ov] ! second opposite pair ( p>allel plate screws4 ,if ?is be v c>efully done ) a correctly divid$ bubble1 ! ,y's ( ! telescope may be op5$ out & ! telescope be rev]s$ end = end 9 its ,y's1 & ! bubble rema9 true4 ,b x is q z well to g ov] all ! adju/m5ts a second "t1 z be=e recomm5d$4 #bjd4--;,if ! level is to be adju/$ by night1 ?is c be done v correctly by a f9e cross drawn on pap] plac$ on a wall1 ) a c&le or gas burn] %9+ brightly on x at tw5ty feet or s di/ance f ! in/rum5t4 ,= ?is adju/m5t by night ! in/rum5t mu/ be well con/ruct$1 z ! tubes require draw+ out to _! full ext5t = focuss+ ne> objects4 ,if ! tubes are n q /raight1 ! object-glass suff]s consid]able displacem5t 9 ! draw+ out1 or te*nically droops1 :i* is a v common fault 9 badly-made in/rum5ts4 #bje4--,:]e webs are us$ = ! read+1 !y are liable to become baggy or dirty1 art4 #aja1 & v frequ5tly to break2 no?+ c1 !re=e1 be m useful ?an to be able to re-web a /op 9 ! ev5+1 ) comm& ( ! easy & c]ta9 means ( readju/m5t describ$1 :5 f> f ! optician's aid4 #bjf4--;,z ! ,y-level is s p]fect 9 its arrangem5t = adju/m5ts1 & s ne>ly meets ! optician's ideal1 x w be well to inquire :at are ! objections made to its use by ! majority ( ,briti% surveyors4 ,! fir/ & mo/ important is t x possesses s _m loose p>ts1 to :i* ! practical man hone/ly objects4 ,! au?or 01 _m ye>s ago1 :5 ,y-levels 7 m popul>1 try+ to p]suade a cauti\s practical surveyor :o appe>$ to be v anxi\s = ! c]ta9ty ( 8 "w1 & :o 0 go+ abroad1 to take a ,y-level in/ead ( a dumpy "o he 0 select+1 :5 he _h 8 argum5ts /opp$ by ! foll[+ "q3--,suppose y 7 survey+ 9 a tropical c\ntry1 ?\s&s ( miles & an ocean voyage f civilisation1 :]e y\r native port] object$ to c>ry mu* weight1 & y\r in/rum5t case _h to be left at a back /ation--:5 y\r umbrella 0 all ! burd5 y felt y c\ld support4 ,9 ?is case1 suppose y\r port]1 :om y _h lo/ sight ( = a %ort "t1 arriv$ ) y\r level1 m9us ! telescope--lo/ by becom+ loose1 p]haps f hav+ be5 play$ ) :ile he 0 re/+--h[ w\ld y praise ! ,y-level8 ,?is g5tleman assur$ me t he did n1 & t ?is 0 a true acc\nt ( 8 exp]i5ce ) ! la/ ,y-level he possess$4 ,o!r objections1 besides loose p>ts1 are t ,y's & coll>s d n rema9 z p]fect z :5 !y leave ! optician--t !y are liable to we> by friction ( con/ant movem5t 9 be+ c>ri$ ab\t ^u ! po9ts 9 contact betwe5 !m1 & !reby =m facets2 t ! coll>s become corrod$ by exposure1 & t !y h op5 spaces t collect s& f fly+ du/ :i* fixes itself into ! coll>s & ,y's1 s t ?is arrangem5t loses ! p]fection ! optician claims = x4 ,fur!r1 t ! cross bubble1 :i* is uni=mly plac$ on ! dumpy level1 effects a great sav+ ( "t ov] sw++ ! telescope backw>ds & =w>ds ) e movem5t ( ! adju/+ screws4 ,ano!r feature is t 9 ! dumpy level1 to be describ$1 ! v]tical & horizontal webs ( ! diaphragm _c be di/urb$ f _! position by rotation ( ! telescope aft] ! level is once set up2 & ?is v]ticality indicates conv5i5tly at once :e!r ! /aff is held v]tically1 :i* is o!rwise a great difficulty ) ! ord9>y =m ( ,y-level read+4 #bjg4--;,improv$ ,y-,level4--,! above-describ$ defects ! au?or has tri$ to rem$y by a modification ( ! ,y arrangem5t1 by =m+ ! ,y's ) mu* broad] be>+s1 & in/ead ( ! old loose p9s screw fa/5+s are fitt$1 :i* firmly lock ! telescope 9 position ) ! webs v]tical4 ,?is1 s f>1 obviates ! dang] f loose p>ts1 z by ?is arrangem5t ! telescope also becomes practically firmly fix$4 ,9 adju/m5t ! coll>s are op5$ out1 & 9 clos+ press a /ud into ! telescope by :i* x takes a giv5 position4 ,?is enables a cross bubble1 %[n on ,fig4 #eg1 to be also plac$ on ! telescope = approximate adju/m5t1 :i* saves ! frequ5t di/urbance ( ! telescope by mak+ cross adju/m5ts4 ,! diaphragm ( ?is ,y-level is exactly ! same z t ( ! dumpy1 to be describ$ art4 #baj4 ,f ! limb d[nw>ds ! au?or uses ! same con/ruction z he n[ employs on 8 improv$ dumpy level4 ,?is w be describ$ ) t in/rum5t fur!r on1 art #bca1 seq4 ,also ! sett+-up adju/m5t ) x1 :i* is diff]5t f t already describ$ :]e p>allel plates are employ$4 ,illu/ration3 ,fig4 #eg4--;,improv$ ,y-level4 #bjh4--,p]haps1 ^u ! :ole1 ! conditions :i* =m]ly r5d]$ ! ,y-level und\bt$ly ! be/ practical level h s mu* *ang$ t ! m solid con/ruction ( ! dumpy may entirely sup]s$e x1 z x seems likely to d 9 mod]n practice1 & ! optician w lose 8 ideal4 ,"s reasons = ?is may be /at$1 b :e!r suffici5t is a "q4 ,! manufacture ( object-glasses ( good figure & prop] c5tr+ 0 =m]ly und]/ood by a few sci5tific opticians1 :o 7 pr9cipally engag$ ^u a/ronomical telescopes1 s t1 ) ! exception ( ^? made by ,tr\ghton & ,simms1 no v good & accurately c5tr$ l5ses 7 us$ 9 survey+ in/rum5ts4 ,) bad c5tr+ alone1 9 ord9>y telescopes1 ! webs 9 collimat+ 7 drift$ aside1 & ne$$ ! ,y sy/em ( adju/m5t to make ! telescope workable = levell+4 ,9 ! mod]n good object-glass1 ( :i* !re are n[ sev]al mak]s1 ! c5tr+ is s ne>ly p]fect t ! webs 9 adju/m5t fall 9 ! c5tre ( ! diaphragm :5 x is plac$ true to ! cyl9drical axis ( ! telescope4 ,if ! webs are plac$ z sugge/$ )\t fur!r adju/m5t1 no v s]i\s int]f]5ce is caus$ by want ( collimation ( ! axis4 ,) ?is fact 9 view1 ! in/rum5t mak] ne$s leave little space = adju/m5t ( ! webs = c5tre displacem5t to become a s\rce ( error to p]sons n us$ to adju/m5ts4 #bji4--;,fur!r1 ) a well-c5tr$ object-glass1 z x leaves ! h&s ( ! sci5tific optician1 & a solidly con/ruct$ adju/m5t to collimation be+ provid$ = 9 ! mak+ ( a level1 true work+ may be done ev5 if !re is a small error 9 ! collimation4 ,! late ,william ,gravatt1 ,c4,e41 0 ( op9ion t firm con/ruction1 compact =m1 & pl5ty ( light 9 ! telescope 7 m important ?an easy facilities ( adju/m5t4 ,!re is no d\bt he f\nd ! less op5 adju/m5ts ! bett] 9 ! h&s ( ! imp]fectly tra9$ assi/ants :o 7 press$ into s]vice dur+ ! railway mania ( #ahdh4 ,at any rate1 at ?is p]iod we h 8 inv5tion ( ! ,gravatt1 or1 z x 0 aft]w>ds t]m$1 ! ,dumpy level1 :i* has rema9$ ) u ) slight modifications 9 its me*anical p>ts & ) increas+ popul>ity until ! pres5t "t4 ,! late ,mr4 ,tr\ghton1 recognis+ ! same facts1 also made a level 9 :i* !re 0 no adju/m5t to ! supports ( ! telescope aft] x left ! h&s ( ! mak]4 ,9 8 level he also left no adju/m5t to ! bubble tube1 :i* no d\bt w\ld prev5t tamp]+1 b :i* c\ld sc>cely be call$ an improvem5t2 z ?is tube is liable at all times to be brok51 !re=e to ne$ replac+ ) ano!r tube1 :i* _c be made q simil>1 & !re=e ne$s easy means ( adju/m5t = a surveyor to replace x :5 abroad4 ,?is level has gone out ( use1 b x is m5tion$ "h1 z ! old engrav+ ( x rema9s 9 "s ( our mod]n text-books4 ,illu/ration3 ,fig4 #ei4--;,dumpy level4 #baj4--,! ,dumpy ,level4--,"o ( ! mo/ important /ructural improvem5ts made by ! late ,william ,gravatt 9 8 dumpy level1 0 ! addition ( a cross bubble1 %[n end-view 9 ,fig4 #ei at ,,cb4 ,?is improvem5t ov] ! old =m ( ,y-level p]mitt$ ! sett+-up ( ! in/rum5t to be complet$ approximately1 )\t turn+ ! level a qu>t] revolution backw>ds & =w>ds sev]al times dur+ ! op]ation1 z 0 necess>y 9 ! sett+-up ( ! ,y-level4 ,! compact =m1 lightness1 & l>ge field ( view 9 ! telescope o!rwise comm5d$ x to civil eng9e]s1 :5 ,gravatt _h po9t$ out ! possibility ( suffici5t practical adju/m5t )\t resort+ to ! cumbr\s proportions ( ! ,y-level z x 0 !n made4 ,mod]n exp]i5ce has %[n t ! dumpy =m ( telescope c\ld v well be appli$ to ! ,y con/ruction1 & ?is has be5 done1 z %[n 9 ! prec$+ pages2 b at ! "t ! dumpy 0 inv5t$ by ,gravatt1 ! ,y-levels 7 v commonly made #bj in*es or m 9 l5g? ( telescope1 & 7 altoge!r v flimsy affairs4 ,gravatt's #ab-;in* level 0 f\nd to be q equal 9 p[] & ( less ?an half ! bulk & weight4 ,a #ab-;in* dumpy %\ld read ! #ja foot on a ,sop) /aff1 :i* is describ$ 9 ! next *apt]1 at #e *a9s ) a webb$ or glass diaphragm1 ,fig4 #fa2 ) a m op5 read+ ?an ,sop)'s /aff a great] di/ance ?an ?is4 ,a #ad-;in* dumpy %\ld read ! #ja foot at #aj *a9s4 #baa4--,! ,dumpy ,level ( mod]n =m is repres5t$ 9 ! engrav+1 ,fig4 #ei4 ,x consi/s ( a telescope1 fully describ$ art4 #id1 :i* c>ries a ray %ade ,,rs at ! object-glass end1 to "w 9 ! field to ea/w>d or we/w>d fac+ a l[ sun4 ,! eye-piece ,,ep is adju/able to ! webs 9 ! telescope by pressure 9 or out4 ,two /raps or b&s are accurately fitt$ & sold]$ r\nd ! tube ( ! telescope2 "o ( ^! c>ries a h+e jo9t1 & ! o!r a pair ( lock+ nuts to support ! level tube ,,gg1 & at ! same "t p]mit its adju/m5t4 ,! level cas+ tube has two ?ree-qu>t] b&s1 :i* slide ^u x1 po9t$ at "o end ,,gg3 ^! adju/ to ! l5g? ( ! bubble = *anges by temp]ature4 ,! l[] "p ( ea* /rap-piece is left a solid block ( metal1 to give v firm support to ! telescope z x re/s ^u ! limb ,l b5ea?4 ,! limb may be ei!r a ca/+ ) a socket screw only 9 its c5tre1 or a compass box may be =m$ 9 ! c5tre & ! socket screw be plac$ "u ?is1 z x is %[n 9 ! figure at ,s4 ,! atta*m5t ( ! telescope support to ! limb is made by ?ree screws1 two ( :i* draw ! limb d[n1 & "o 9 ! c5tre presses x upw>ds1 z %[n 9 ! section ,fig4 #fj--;,,cc telescope1 ,,tt draw+ screws1 ,p press+ screw4 ,illu/ration3 ,fig4 #fj4--;,atta*m5t ( telescope block to limbs4 #bab4--;,x w be se5 t by ?is means firm adju/m5t may be made ei!r by rais+ or l[]+ "o end ( ! telescope1 z also by a lat]al rock+ motion %\ld ! web or bubble n be q to position4 ,?is plan is c]ta9ly mod]ately solid1 & little fault c be f\nd ) x1 except t a little torsion may be put on ! telescope by unequal screw+1 & t x appe>s slov5ly 9 leav+ an op5 gap betwe5 ! limb & block2 !re=e ! au?or pref]s 9 8 own =m ( level1 :i* w be pres5tly describ$1 t ! block be solidly fitt$ d[n ^u ! limb1 z is %[n 9 ! section ,fig4 #fj1 & ! telescope be plac$ p]man5tly exactly p>allel ) x4 ,if ! v]tical axis be once fix$ truly p]p5dicul> to ! axis ( ! telescope z solidly z possible !re is v little risk ( a bell-metal c5tre ( in* or s diamet] be+ b5t2 !re=e all p>ts may be closely fitt$ betwe5 ! axis & ! telescope4 ,"s mak]s1 in/ead ( screw+ d[n at bo? ends ( ! limb1 make "o end a rock+ c5tre & adju/ only by screw at ! o!r end4 ,?is plan lacks a little ( ! /ability look$ = 9 ! dumpy sy/em4 ,! g5]al con/ruction ( ! v]tical axis is ! same z t ( ! ,y-level already describ$4 ,! p>allel plates1 tripod head1 & tripod are also ! same1 art4 #aic1 ,fig4 #ee4 #bac4--;,z ! telescope ( ! dumpy level does n possess any simple means ( det]m9+ ! accuracy ( ! fitt+ ( its slid+ tube1 x is a v important po9t 9 ^! levels t ?is fitt+ %\ld be good1 s t ! object-glass does n droop :5 ext5d$4 ,= ?is reason ! inn] slid+ tube ( ! telescope %\ld be z long z possible1 & its adju/m5t by ! rack suffici5t to br+ an object 9 focus at #ae to #bj feet di/ance4 ,?is po9t is sometimes neglect$4 ,! au?or 0 once amus$ by a "y surveyor br++ him an inv5tion1 :i* 0 to fix two po9ts by ! side ( ! telescope to enable him to read at %ort di/ances4 ,x 0 se5 on exam9ation ( 8 own level t 8 telescope1 a badly-fitt$ "o1 w\ld n read at half a *a91 h5ce ! +5uity ( 8 inv5tion4 ,9 "s *eaply made levels ! solid r+ fitt+ to ! telescope1 above describ$1 :i* connects ! limb firmly ) ! bubble tube1 is replac$ by blocks sold]$ on ! telescope ) s(t sold]3 ! me?od is v uns\nd f risk ( imp]fect sold]+4 ,! blocks are v liable to become loos5$ by a j>4 #bad4--,! diaphragm ( ! dumpy level is g5]ally webb$ ) two v]tical webs & "o horizontal4 ,9 use ! image ( ! /aff is br\ght betwe5 ! v]tical webs1 :i* indicate :e!r x is held upright4 ,! upp] m>g9 ( ! portion ( ! horizontal web betwe5 ! two v]tical ones is ! index ( level to :i* all read+s are made1 ei!r = adju/m5t or = read+ ! levell+ /aff 9 ! field4 ,! some:at loose & slov5ly f\r-screw adju/m5t = a level diaphragm us$ 9 r\gh "w ) cap/an-head screws1 %[n ,fig4 #bc1 p4 #ej1 :i* is necess>y = ! adju/m5t ( ! telescope 9 ,y's1 has be5 ab&on$ = _m ye>s 9 ! bett]-con/ruct$ dumpy levels by all good mak]s1 & ! m solid con/ruction1 %[n bel[1 ,fig4 #fa1 us$ 9 ! place !re(4 ,9 ?is plan !re is no lat]al adju/m5t3 ! diaphragm is c>ri$ z a frame 9 a dovetail slide1 & is adju/able by v]tical screws only4 ,! figure %[s ! face ( diaphragm3--,,bb slide pieces1 ,a slide mov$ by cap/an-head screws4 ,illu/ration3 ,fig4 #fa4--;,diaphragm ( dumpy level ) webb$ /op4 ,illu/ration3 ,fig4 #fb4--,same1 ) /adia webs4 #bae4--,subt5se or ,/adia ,webs4--,x is v advisable 9 all levels to h two extra webs1 or l9es cut on glass1 plac$ "o on ea* side ( ! c5tral horizontal web or l9e1 fix$ at su* a di/ance ap>t t ! image ( #aj feet ( ! /aff :5 plac$ at #aj *a9s di/ance may exactly cut ! inn] space betwe5 ! l9es4 ,^! webs or l9es may be us$ z a means ( measur+ di/ances (t5 m exactly ?an c be p]=m$ ) ! *a9 if ! surface ( ! l& is irregul>2 or1 9 any case1 !y =m a good *eck ^u *a9 measurem5t4 ,if ! webs or l9es are sep>at$ s z to subt5d an arc ^: *ord is #aj feet at #aj *a9s1 x is easily se5 t #a foot ( ! /aff w repres5t ?is *ord at #a *a91 & t ea* #ja ( ! foot on ! /aff w repres5t #a l9k 9 di/ance4 ,a diaphragm webb$ or l9$ 9 ! mann] describ$ is %[n 9 ,fig4 #fb4 ,!re is "s difficulty 9 plac+ webs 9 exact position1 & all[ance %\ld be made = ! optical conditions by ! addition ( a plus factor4 ,?is important subject w be fully discuss$ h]eaft] 9 ,*apt] ,,xii4 ,illu/ration3 ,fig4 #fc4--,tripod4 ,illu/ration3 ,fig4 #fd4--,section ( "o turn-up leg ( ! same4 ,illu/ration3 ,fig4 #fe4--,section ( tripod4 #baf4--,tripods1 or ,/&s4--,?is matt] 0 def]r$ :5 describ+ ! ,y-level4 ,! same =m ( tripod is us$ = bo? ,y-level & dumpy4 ,9 ?is c\ntry ! tripod is g5]ally made ( /raight-gra9$1 well-season$ ,honduras mahogany1 :i* /&s bett] ?an any o!r wood4 ,:5 ! tripod is fold$ up = c>ry+ or = putt+ by x =ms a cyl9drical pole :i* is belli$ out at ab\t "o-?ird its l5g? f ! top1 & dim9i%es d[nw>ds & upw>ds f ?is po9t4 ,= a #ad-;in* ,y-level or dumpy ! dim5sions ( ! tripod are ab\t #c in*es at its greate/ diamet] :5 clos$1 tap]+ (f to #b in*es at bo? ! top & ! bottom ends4 ,= a #ab-;in* level ! section is some:at less4 ,ea* leg ( ! tripod takes an equal section ( ! cyl9d]1 ! inn] angle meet+ 9 ! axis be+ at an angle ( #abj1 z %[n 9 section ,fig4 #fe4 ,%ovel-pieces are %[n 9 ,fig4 #ei ,,aa 7p4 #aaj71 atta*$ to ! top ( ea* leg by f\r screws pass+ f ! brass to ! wood4 ,!re %\ld be also two screws f a brass plate inside ! leg to ! %ovel-piece1 mak+ connection brass to brass3 ?is is important1 z fix+s f ! brass to ! wood only become loose & %aky by %r9kage4 ,! %ovel-piece is =m$ into a /rong t5on at its upp] end1 ?r\gh :i* a bolt passes connect+ ! book-pieces toge!r4 ,! book-pieces are plates cut to an angle ( #abj1 s z to fall true on ! t5ons ( ! %ovel-pieces4 ,:]e h&-"w is us$ = mak+ ! tripod head1 ! book-pieces are atta*$ by ?ree screws2 :]e ma*9]y is us$1 ! head is made 9 ! %ap+ ma*9e out ( a solid ca/+1 :i* is mu* bett]4 ,! tripod head c>ries a screw ab\t #a in*es diamet] ) co>se ?read1 :i* fits into a socket on ! l[] p>allel plate ( ! level1 :e!r ,y or dumpy4 ,!re %\ld always be a pla9 piece1 te*nically a lead1 above ! screw4 ,?is holds ! in/rum5t /eady be=e x is screw$ d[n1 & also leads ! screw directly to its correspond+ ?read1 ?us sav+ risk ( cross+ ! ?read4 ,a common defect 9 tripod heads is ! ?9ness ( ! t5on1 s t ! leg1 if twi/$1 is felt to be rickety4 ,?is t5on is bett] made wide1 z %[n 9 ! /aff head 9 ,fig4 #gj;,a1 seq4 #bag4--,!re is a little diff]5ce ( op9ion z to ! =m ( ! woodwork ( ! tripod = #ad-;in* levels1 "s pref]r+ an op5 fram$ /& 9 place ( ! solid =m %[n 9 section ,fig4 #fe4 ,^! op5 fram$ /&s are n s compact to c>ry1 &1 z ! au?or ?9ks1 unnecess>y = levels ( #ab in*es & "u :]e ! tripod head is solidly made4 ,!y are well adapt$ = l>g] levels & = !odolites1 !re=e ! description ( a fram$ tripod w be def]r$ to ! discussion ( ^! in/rum5ts fur!r on4 ,a few eng9e]s pref] yell[ p9e = ! tripods in/ead ( mahogany3 ?is is mu* light] = its relative /iffness1 b x is r s(t = ! fix+ to ! %ovel-pieces1 & !re=e sc>cely s reliable z mahogany = durability4 ,:]e lightness is important ! au?or employs c$>1 :i* is z light z p9e b h>d]4 #bah4--,! l[] po9ts ( ! legs1 te*nically toes1 are po9t$ to an angle ( ab\t #fj1 & are %od on ! insides ) /eel plates to bite ! surface ^u :i* ! tripod /&s :5 ! legs are ext5d$ = use4 ,two brass r+s slip ov] & b9d ! legs toge!r :5 ! tripod is out ( use4 #bai4--,_m ye>s ago ! au?or introduc$ ! plan ( hav+ "o ( ! legs to turn up at ab\t #a foot di/ance f ! toe4 ,?is is %[n ,fig4 #fc at ,a1 & 9 detail section ,fig4 #fd4 ,! jo9t is made p]fectly firm by a w+$ screw at ,s1 :i* screws f a boss ca/ on ! h+e ,j to a solid metal %oe ,p4 ,:5 ! leg is turn$ up1 ! screw fixes x 9 ! female screw ,s4 ,?is plan is v conv5i5t = use 9 m\nta9\s di/ricts1 z x enables ! level to be set up fairly well )\t an uncom=table angle to any ( ! legs1 or risk ( ! in/rum5t toppl+ ov]4 ,?is plan is n[ ne>ly sup]s$$ by a ball jo9t z a "p ( ! sett+-up adju/m5t4 ,! tripod head %[n "u ! level ( ,fig4 #ei is by no means ! be/1 b x is ! easie/ made !re=e1 x is ! g5]al trade =m 9 use1 bo? = ! level & !odolite4 ,"s v sup]ior =ms w be discuss$ fur!r on 9 description ( ! in/rum5ts to :i* !y are atta*$4 #bbj4--,! adju/m5ts ( ! ,dumpy ,level4--,z ?is in/rum5t does n possess ! means ( revolv+ ! telescope ^u its axis z ) ! ,y-level1 ! adju/m5ts are some:at m complicat$1 & are p]=m$ 9 an entirely diff]5t mann] :5 !y are to be made by ! civil eng9e]4 ,! diff]5ces are n s great 9 ! h&s ( ! optician1 z he g5]ally possesses a movable pair ( ,y's ^u :i* he c adju/ ! telescope conv5i5tly = collimation )9 8 own works1 by support+ ! telescope tube 9 ,y's at a position ext]ior to ! b&s :i* surr\nd x4 ,! tools = ?is adju/m5t ! au?or has occasionally suppli$ ^u dem& ) ! dumpy level4 ,b :at is necess>y "h w be to give ! mode ( adju/m5t :i* ! civil eng9e] c accompli% at any "t )\t supplem5t>y app>atus4 ,! bubble is h&i] to "w ) :5 adju/$ to rev]se 9 ! c5tre ( its run1 b x does n really matt]1 z equally accurate "w c be done ) x 9 any o!r position4 ,%\ld ! bubble n rev]se 9 ! c5tre ( its run1 adju/ ! in/rum5t by ! levell+ screws until x rev]ses 9 "s position4 ,say y />t ) bubble 9 ! c5tre1 & on rev]s+1 x runs t[>ds ! eye end ( ! telescope six divisions1 !n alt] ! levell+ screws until x is only half ?is1 or ?ree divisions t[>ds ! eye end1 !n1 if prop]ly levell$1 ! telescope w make an entire revolution ) ! bubble 9 t position1 :i* w prove t ! axis is v]tical4 ,! bubble c n[ be adju/$ by ! oppos+ nuts at ! "o end by means ( ! tommy p9 7provid$ 9 ! case7 until x is 9 ! c5tre ( its run1 & x w !n rev]se 9 t position in/ead ( ?ree divisions t[>ds ! eye end4 #bba4--;,adju/m5t to ,collimation4--,^u a fairly level piece ( gr\nd ! /aff plate1 fully describ$ fur!r on1 is trodd5 well d[n on ! gr\nd1 & ! level is set up at say #c *a9s f ?is1 9 :i* position ! /aff is read z a back sight4 ,n[ 9 ! opposite direction 9 ! same l9e1 at #c *a9s di/ance f ! level1 a second /aff plate1 or 9 defect ( ?is if ! surface be n firm1 a /ake or a b\ld]1 is driv5 firmly d[n 9 ! e>?1 & ! /aff is plac$ ^u ?is erect & face to ! in/rum5t z a =esight4 ,! in/rum5t is turn$ half r\nd & ! second /ation is read4 ,^! read+s ( ! /aves tak5 w be truly level ) ea* o!r1 if ! axis ( ! in/rum5t has be5 set up q v]tically1 s t ! bubble has kept its c5tre 9 all positions4 ,?is is true al?\gh ! axis may h be5 out ( collimation4 ,?is arrangem5t is %[n 9 ,fig4 #ff1 ,l ! fir/ position ( ! level tak+ sights at equal di/ance f ,s & ,s4 ,let ! level be n[ remov$ to ,l3 if correct x %\ld cut ! /aves ,,ss at equal di/ances above or bel[ ! fir/ read+s at aa1 :i* are at equal di/ances f bb read+s f ,l1 !re=e level & p>allel ) ! fir/ read+4 ,illu/ration3 ,fig4 #ff4--;,adju/m5t ( dumpy level4 #bbb4--;,9 ! dumpy level1 z x leaves ! h&s ( any respectable mak]1 ! subsequ5t adju/m5ts requir$ c nev] be great1 unless ! level has suff]$ a s]i\s fall s z to b5d ! limb4 ,! rewebb+ ! /op1 if c>efully done1 w\ld require only a slight readju/m5t2 b x may be conv5i5t to give an exact me?od = extreme cases1 :i* may be giv5 9 detail = cle>ness1 & at ! same "t we may also consid] ! influ5ce ( ! curvature ( ! e>?4 #bbc4--,orig9al ,adju/m5t ( ! ,dumpy ,level to ,collimation ) consid]ation ( ! ,curvature ( ! ,e>?4--,suppose ! read+s ( ! two levell+ /aves at #aj *a9s ap>t1 tak5 ) ! level plac$ at int]m$iate di/ance z be=e1 read #gej & #dej1 & t we n[ place ! level l9e>ly at #a *a9 outside ! fir/ read+ & x reads ! ne> /aff #fej & ! di/ant /aff #eej1 by ! incl9ation ( ! gr\nd1 ?is w\ld be a & a - read+2 b we require bo? read+s ( "o sign1 & z ! di/ant /aff read+ is mu* too high1 x is cle> we require - read+s = correction4 ,! correction w be ( ! diff]5ce ( read+ 9 proportion to ! di/ances1 call+ ! l[] read+ m9us-- #gej - #fej -#a1 #dej #eej #a1 diff]5ce #b4 ,t is -#b1 z our read+s are - & z ! -#b is 9 #aj *a9s1 at #a *a9 ! di/ance ( - ! ne> /aff -#b1 & #aa *a9s ! di/ant /aff -#bb4 ,! correction w !re=e be = ! ne> /aff #a *a9 di/ant #fej - #b #fcj1 & = ! di/ant /aff at #aa *a9s #eej - #bb #ccj -#ab bel[ ea* ( ! fir/ read+s4 ,if ! telescope be n[ collimat$ to ! ne> /aff read+ #fcj1 by adju/+ ! screws imm$iately "u x = di/ance betwe5 ! limb & ! telescope1 & ! bubble be readju/$ to ! telescope )\t mov+ ! in/rum5t or t\*+ ! p>allel plate screws1 ! adju/m5t w be p]fect1 less ! small error due to ! e>?'s curvature 9 #a *a94 ,if ! telescope be adju/$ to ! di/ant /aff #ccj1 curvature ( ! e>? w be correct$ by ! level = #aa *a9s1 :i* is #jjajf foot or #ja ne>ly1 ! smalle/ read+ we h on ! /aff4 #bbd4--;,x 0 claim$ by ! late ,william ,gravatt = 8 me?od ( adju/m5t1#c :i* 0 equival5t to t giv5 above1 b m complicat$ & ) ?ree /aves1 t ! fix$ correction = curvature at #aj *a9s w\ld be uni=m 9 ! work+ ( ! level pro rat = all di/ances4 ,!re is "s diff]5ce ( op9ion on ?is subject3 at any rate1 a #aj *a9 correction w\ld only be applicable to v approximately level gr\nd :]e av]age #aj-;*a9 /ations c\ld be tak54 #bbe4--,:]e space is n at comm& & curvature correction is n desir$1 adju/m5ts ( ! level may be made ) c>e at #a *a9 di/ance on ea* side ( ! sett+-up ( ! level ) "o /aff only1 :i* c be mov$ f "o /ake to ! o!r1 & ) ! f9al sett+-up ( ! in/rum5t at #a *a9 di/ance f ^! /akes z be=e1 art4 #bba4 ,= ?is ! /aff only requires mov+ twice1 if ! collimation adju/m5t is to ! la/ read+ only calculat$ out z above4 ,?is close sy/em has a c]ta9 am\nt ( m]it1 t by read+ f "o /aff only = bo? /ations x is m accurate1 z any inequality betwe5 ! divisions ( two sep>ate /aves is avoid$4 ,illu/ration3 ,fig4 #fg4--;,collimator = adju/m5ts to horizontality ( ! telescope4 #bbf4--;,collimator4--,optical manufactur]s 9 popul\s di/ricts1 & "s obs]vatories1 z t ( ! ,india ,/ore ,dep>tm5t at ,lambe?1 adju/ by means ( ! collimator by ! exact me?od due to ! late em95t ,g]man ma!matician1 ,c>l ,f4 ,gauss1 :i* is h5ce t]m$ ! me?od ( ,gauss4 ,! collimator consi/s ( any good telescope p]man5tly adju/$ to sol> focus1 ) a webb$ diaphragm plac$ 9 ! focus1 :]e x may be illum9at$ by a lamp or by ! reflection ( daylight1 & provid$ ) means ( br++ ! telescope to a level position4 ,z ! collimator is g5]ally con/ruct$1 x consi/s ( an #ah-;in* telescope1 ,fig4 #fg1 ( ! same description z t us$ = a ,y-level1 describ$ art4 #id1 9 :i* ! telescope is surr\nd$ by accurately turn$ coll>s =m$ to re/ 9 ,y's4 ,! ,y's are support$ ^u a heavy ca/-iron /&1 ( some:at triangul> =m1 ( ne>ly ! l5g? ( ! telescope1 ab\t #f in*es wide at "o end & #b in*es at ! o!r4 ,! /& has two feet ext5d$ to ! full wid? at ! wid] end1 & "o foot at ! n>r[] end "u ! telescope4 ,ea* foot has an adju/+ screw4 ,! complete collimator is support$1 at ab\t ! height ( ! telescope ( ! level on its /&1 on a v solid pi] ( /one or brickwork 9 cem5t capp$ ) a /\t slate slab4 ,! telescope is br\ght to p]fect collimation z ) ! ,y-level1 already describ$ art4 #bjj1 & ! level is fix$ true ) ! axis ( ! telescope1 :5 ! collimation is p]fect4 #bbg4--;,a lamp or gas flame is plac$ at a %ort di/ance f ! eye-piece end ( ! telescope1 s z to illum9ate ! webs t !y may be di/9ctly se5 :5 look+ into ! objective end ( ! telescope4 ,9 bright daylight1 if !re is a skylight ov]1 a reflector w answ] ! same purpose4 ,at ! ,lambe? ,obs]vatory a f9e ne$le-po9t hole is us$ in/ead ( webs4 #bbh4--,! in/rum5t to be adju/$ may be plac$ at any conv5i5t di/ance f ! collimator4 ,= adju/m5t ( a level1 :]e ! collimator is already 9 adju/m5t1 ! level is rais$ ^u its /& until ! axis ( ! telescope s5sibly co9cides ) ! axis ( ! collimator2 !n if ! telescope ( ! level to be adju/$ be focuss$ into ! objective end ( ! collimator1 ! illum9at$ webs w be cle>ly se52 & if ^! webs be br\ght by adju/m5t ( ! level exactly to co9cide ) its own webs1 ! collimation l9es ( ! two in/rum5ts are exactly p>allel4 ,9 ?is adju/m5t x is only necess>y to be sure t ! v]tical axis ( ! level is truly v]tical1 s t ! bubble rev]ses )\t displacem5t1 9 :i* case ! :ole in/rum5t mu/ !n be 9 p]fect adju/m5t4 #bbi4--;,x w\ld be v difficult to use ?is me?od ( adju/m5t if x 7 necess>y t ! axes ( ! level & collimator %\ld exactly co9cide4 ,x is only necess>y t !y %\ld ne>ly co9cide1 on acc\nt ( ! imp]fection ( object-glasses1 :i* r>ely "w s well ne> ! edge z t[>ds ! c5tre2 o!rwise any directly p>allel position 9 front ( ! object-glass w\ld answ]1 z ! next diagram w %[4 ,let ,o1 ,fig4 #fh be ! object-glass ( ! collimator1 ^: sol> focus is at ,f4 ,!n ! rays ,,pp1 & all o!r p>allel rays fall+ on ! object-glass1 w be br\ght to a focus at ,f2 & reciprocally all rays dep>t+ f ,f 9 pass+ ?r\gh ?is object-glass w leave 9 p>allel l9es ,,pp4 ,let ,o be ! object-glass ( a telescope to be collimat$1 ,f its sol> focus4 ,!n all rays f ,p to ,p dep>t+ f ,f t fall )9 ! p>allel space ,p,p w be br\ght to focus at ,f4 ,:5 ! image at ,f is illum9at$ by a lamp ,l1 ! webs or o!r index w be cle>ly se5 by ! eye-piece at ,f :5 ! two telescopes are exactly p>allel ) ea* o!r4 ,9 ?is position ! webs ( ! level are adju/$ to make ?is co9cid5ce4 ,x is easily se5 t by ?is me?od we elim9ate all errors ( atmosph]ic refraction1 & are q indep5d5t ( ! /ate ( ! atmosph]e = obta9+ di/9ct vision = adju/m5t4 ,illu/ration3 ,fig4 #fh4--;,diagram ( collimation by two telescopes4 #bcj4--,:5 two levels are at comm&1 "o a ,y-level1 or ev5 a dumpy 9 p]fect adju/m5t1 ! "o may be us$ z a collimator to ! o!r by sett+ !m up at a di/ance )9 _! focal range on a firm basem5t floor4 ,a c&le or a lamp w give suffici5t light to illum9ate ! webs ( ! in/rum5t1 :i* is us$ z a collimator1 be+ c]ta91 ( c\rse1 t ?is in/rum5t is fir/ plac$ 9 level adju/m5t & set at sol> focus1 & t ! in/rum5t us$ z a collimator has a good object-glass4 ,illu/ration3 ,fig4 #fi4 ,illu/ration3 ,fig4 #gj4--,/anley's model #ad-;in* dumpy level4 ,illu/ration3 ,fig4 #gj;,a4--,tripod4 #bca4--;,improv$ ,dumpy ,level4--,! writ] has made "s improvem5ts 9 ! dumpy level1 :i* h s f> met ) v g5]al approbation f ! pr(ession1 ,fig4 #gj4 ,^! improvem5ts are direct$ to ensure mu* great] s5sitiv5ess 9 ! long] bubble1 !re=e great] accuracy 9 ! "w p]=m$ by x2 m solidity ( con/ruction )\t increase ( weight2 & p]man5ce ( read+ index1 ) "s additional matt]s4 ,9 ^! improvem5ts ! m\nt+ ( ! long] level tube1 in/ead ( be+ plac$ 9 a /iff jo9t at "o end1 or betwe5 rigid clamp+ nuts at bo? ends1 has a b>rel-fitt+ at "o end :i* is gr\nd into a p>allel hole4 ,?is plan admits ( circul> self-adju/m5t to ! bubble tube1 :i* ! clamp+ ( ! nuts c nev] twi/ or /ra9 dur+ v]tical displacem5t2 & ! jo9t c be made p]fectly s\nd ) c]ta9ty1 :i* saves ! risk ( accid5t to ! bubble f expansion by heat & "s o!r conditions4 ,a m rec5t =m ( cross level1 ,fig4 #fi1 %[n 9 p]spective ne> ! ray-%ade 9 ! engrav+ ,fig4 #gj has be5 design$ by ! au?or1 9 :i* ! level cas+ is bor$ entirely out ( ! solid4 ,x is support$ ^u ! side ( "o telescope /rap by ?ree /\t p9s1 ! c5tre "o fitt+ its hole1 & ! two out] ones are loosely held by cross screws to p]mit a small am\nt ( adju/m5t1 :i* is all t is necess>y4 ,by ?is con/ruction ! level fix+s are made 9 five pieces only1 includ+ screws1 in/ead ( ?irte5 z usual1 at ! same "t mak+ ! level m portable & solid = h>d we>4 ,! telescope /raps are fitt$ at _! /umps solidly d[n ^u ! limb1 z %[n ,fig4 #fj1 p4 #aab4 ,adju/+ screws are plac$ "u ?is z 9 ! dumpy level describ$1 b ! pressure screw is n employ$ except 9 case ( accid5t f> away f an optician1 :5 x is f\nd to be !re ready = use4 ,! limb is fram$ out into two edge b>s3 ?is gives great] v]tical sectional /r5g? & resi/ance to torsion )\t increase ( weight 9 ! in/rum5t4 ,:]e a compass is us$1 ?is is includ$ 9 ! frame ( ! limb1 z %[n 9 ! engrav+4 ,! compass is read ) a prism1 ?is be+ mu* m conv5i5t & exact ?an look+ d[n ^u ! divid$ circle1 ! in/rum5t be+ necess>ily plac$ = use at ne>ly ! height ( ! eye4 ,! compass r+ is made ( alum9ium4 #bcb4--,! fur!r improvem5t1 :i* ! au?or consid]s ( ! greate/ mom5t1 is t ! v]tical axis is fix$ directly & firmly ^u ! limb1 & n ?r\gh a loose screw fitt+ = sep>ation at ?is po9t z 9 ! ord9>y dumpy4 ,?is is %[n to be important 9 t1 ) ! dumpy1 :]e a loose screw is employ$1 any little diff]5ce ( screw+ d[n ^u ! axis :5 ! in/rum5t is set up causes s mu* d]angem5t ( a s5sitive bubble 9 relation to ! v]tical axis1 t ! optician is b\nd to use a r dull bubble ) ! ord9>y dumpy4 ,fur!r1 a p>ticle ( grit or ! slighte/ bruise on ! coll> 9 replac+ ! in/rum5t 9 its case ?r[s x out ( adju/m5t at ?is important po9t4 ,! objection to ! au?or's plan is t x makes ! case = ! in/rum5t some:at l>g]2 b ! advantage ( c]ta9ty ( p]man5t adju/m5t appe>s to him v f> to c\nt]balance ?is objection :]e accuracy is aim$ at4 #bcc4--,tribra*4--,! sett+-up adju/m5t ( ! in/rum5t is ^u tribra* limbs ) ?ree screws only4 ,^! screws c nev] /ra9 ! v]tical axis1 :i* 9 ?is in/rum5t is some:at deep] & m firmly made ?an t ( ! dumpy4 ,9 ! old =m ( tribra* ! po9ts ( ! screws 7 held d[n by a spr+ plate plac$ above !m4 ,?is plate1 9 c>ry+ ! in/rum5t ^u its /& ov] ! %\ld]1 :i* is ! mo/ com=table way if ! /ations are n f> ap>t1 0 v liable to /ra9 suffici5tly = ! screws to get loose4 ,! au?or pat5t$ a mu* m solid me?od1 by :i* ! old spr+ plate is entirely disp5s$ )4 ,9 ?is plan ea* screw has a ball at ! l[] end1 :i* is ins]t$ 9 a tubul> fitt+ =m$ 9 a solid tribra*1 made ( exact dim5sions to take x4 ,! tube is op5 on ! upp] side1 z %[n 9 longitud9al section ,h1 ,fig4 #ga4 ,_m ye>s' exp]i5ce & ! fact t numb]s ( mak]s h copi$ ?is =m s9ce ! expiration ( ! pat5t1 %[s ?is plan to be p]fectly successful4 ,! g5]al con/ruction ( ! l[] "p ( ?is level may be se5 f inspection3 ,l limb1 fitt$ ) compass2 ,c axis1 9 "o ca/+ ) ! limb2 ,s sprang1 c>ry+ ! socket & support+ ! in/rum5t4 ,,ph %[s ! ball head arrangem5ts to ! screws4 ,a c5tral screw 9 ?is "p deta*es ! tripod4 ,"o po9t is %[n at ,p1 ( :i* !re are ?ree1 to support ! level ^u a wall or rock 9 cases :]e ! tripod _c be us$--a mo/ important advantage 9 t[n levell+4 ,! tripod head is made mu* m firmly ?an t ( ! ord9>y con/ruction1 by ext5d+ two w+ fitt+s f ! top ( ! %ovel-plates z wide ap>t z possible1 in/ead ( ! n>r[ t5on fitt+ be=e describ$4 ,! %ovel-plates are screw$ to ! /aff by means ( a /\t nut-plate inside ! tripod ,f4 ,^? :o h exp]i5c$ h[ mu* defective levell+ is due to a %aky tripod head w appreciate ?is precaution4 ,! g5]al arrangem5t is also %[n 9 ,fig4 #gj;,a4 ,illu/ration3 ,fig4 #ga4--;,details ( ,/anley's dumpy level3 half elevation to left1 half section to "r4 #bcd4--;,z ! tribra* sy/em ( adju/m5t is ( some:at rec5t adoption to ord9>y survey+ in/rum5ts 9 ?is c\ntry1 x /rikes ! /rang] to x z be+ m difficult 9 use4 ,x is really ! mo/ simple & exp$iti\s sy/em z is cle>ly expla9$ by ! =ego+ diagrams1 ,figs4 #gb1 #gc ( ! plan ( a level1 omitt+ its l[] p>ts4 ,illu/ration3 ,figs4 #gb & #gc4--,tribra* adju/m5t4 #bce4--,! bubble ( ! level is plac$ p>allel ) two ( ! screws ( ! tribra*1 t is z ,b & ,c1 ,fig4 #gb1 & is adju/$ to ! c5tre ( its run4 ,x is !n plac$ at "r angles to ! fir/ position1 s t ! screw ,a comes directly "u ! bubble1 to be adju/$ by ?is screw only until x aga9 comes 9 ! c5tre ( its run4 ,fig4 #gc %[s ?is second position ) ! screw ,a und]nea?4 ,! level %\ld aft] ?is read all r\nd true1 b x is well to try x r\nd p>allel ) ! diff]5t pairs ( screws 9 all positions to give small adju/m5t if requir$4 ,:]e !re is a cross bubble ! level may rema9 = adju/m5t 9 its fir/ position1 b x is well to try x all r\nd1 z ! long bubble is made uni=mly ! m s5sitive4 ,illu/ration3 ,fig4 #gd4--,ray %ade4 #bcf4--,! ,ray ,%ade to ! telescope us$ 9 ! above-describ$ level has two n>r[ slits opposite ea* o!r at #ahj4 ,a z]o l9e is c>ri$ f "o slit to a l9e on ! ray %ade fitt+ :5 ! slits are q horizontal4 ,sights ?r\gh ! slits at z]o enable an approximate cross-level to be tak54 ,! edge ( ! tube ( ! ray %ade is divid$ #cj on ea* side ( ! z]o l9e to #b1 s z to take approximate lat]al incl9es ( ! surface ( ! l& 9 levell+4 ,?is useful plan ( cross-sight+ 0 orig9ally propos$ by ,gravatt4 ,illu/ration3 ,fig4 #ge4--,/anley's plat9o-iridium po9t level /op4 #bcg4--,! mo/ important v>iation f ! telescope ( ! dumpy level describ$ is 9 ! diaphragm1 :]e webs or l9es ( any k9d are entirely done away )1 & are replac$ by a special =m ( index4 ,?is is repres5t$ 9 ,fig4 #ge4 ,! movable "p c>ry+ ! op5+ ( ! diaphragm is plac$ 9 a slid+ fitt+1 z previ\sly describ$1 art4 #bad1 = ! dumpy level4 ,! index :i* replaces ! web is a f9ely-po9t$ ne$le =m$ ( plat9o-iridium 7plat9um #ge1 iridium #be74 ,?is alloy has ab\t ! h>dness ( spr+-temp]$ /eel1 & is1 z f> z kn[n1 p]fectly non-corrosive 9 air or moi/ure4 ,a pair ( v]tical po9ts indicate ! position = hold+ ! /aff4 ,x w be f\nd by exp]im5t t ! po9t read+ is mu* m exact ?an ) ! web1 z irradiation due to edge read+ ( ! web is entirely avoid$1 & also ! cov]+ ( ! object z x w\ld be int]sect$ by ! web due to ! angle its ?ickness subt5ds ^u ! /aff1 :i* is v palpable at #aj *a9s di/ance4 ,! iridium po9t is suffici5tly /rong to be kept p]fectly clean by t\*+ x occasionally ) ! po9t ( a camel-hair bru% if x appe> du/y4 ,) c>e ?is po9t w la/ 9 adju/m5t = z long a p]iod z ! level itself rema9s 9 use4 ,^u fir/ impression ! po9t may n appe> s f9e z a web1 b practically x is m exact1 z ! previ\s exagg]at$ images w %[--,fig4 #gf is ! image ( a division ( ! /aff p>tially cov]$ by a web ,,ww2 ,fig4 #gg t ( a magnifi$ image ( ! po9t ,p br\ght t[>ds a division = read+4 ,x w be readily obs]v$ t ! fractional "p ( ! #a_/ajj foot block1 :i* ! po9t ,p cuts1 is mu* m easily e/imat$ ?an t 9 :i* ! web ,,ww cov]s a "p ( a simil> block4 ,illu/ration3 ,fig4 #gf4 ,fig4 #gg4 ,diff]5ce ( read+ ) a web & a po9t1 %[n mu* magnifi$4 #bch4--;,9 e>ly levels ( improv$ con/ruction1 z %[n ,fig4 #gj1 a difficulty 0 exp]i5c$ 9 practice 9 br++ ! index po9t exactly up to ! edge ( ! l9e z x is %[n 9 ,fig4 #gg at ,p4 ,?is difficulty has be5 obviat$ 9 rec5t highe/ class in/rum5ts by mak+ a tang5t screw adju/m5t to ! axis z %[n "u ! level 9 ,fig4 #gh4 ,!re 0 a great objection to ! old =m ( tang5t adju/m5t by clamp+ on ! axis1 z ?is 0 f\nd to di/urb ! c5tre4 ,9 ! plan %[n 9 ! illu/ration ! clamp is left free by jo9t+ to ! axis until x grips "o ( ! arms ( ! tribra* ^u a v]tical surface2 9 ?is way x _c di/urb ! axis4 ,! level1 ,fig4 #gh1 is %[n m\nt$ on a fram$ /&1 :i* is pref]r$ by ! ,indian ,gov]nm5t1 & is g5]ally necess>y = rigidity = l>ge in/rum5ts ( ov] f\rte5 in*es4 ,?is w be describ$ fur!r on ) !odolites1 art4 #ddg1 on fram$ /&s4 ,illu/ration3 ,fig4 #gh4--,/anley's improv$ dumpy4 #bci4--,/adia ,po9ts4--,! au?or commonly makes ! po9ts1 ,fig4 #ge1 ,,vv /adia po9ts1 by mak+ ! di/ance ( ! extreme ends ( ^! subt5d an angle1 equal to #aj feet ( ! levell+ /aff at t5 *a9s di/ance1 or #a foot ( ! levell+ /aff at #ajj feet di/ance 7 a con/ant to be discuss$ ,*apt] ,,xii471 by :i* measurem5ts ( ! di/ance ( ! /aff c by tak5 or *eck$ by obs]vation ?r\gh ! telescope only4 ,illu/ration3 ,fig4 #gi4--,/anley's quick sett+-up level4 #bdj4--,quick sett+-up ,tribra*4--,"o objection has to be made to ! tribra* ov] ! f\r-screw sy/em ( adju/m5t1 t ! f\r-screw admits ( great] incl9ation to ! tripod1 :i* is important 9 hilly c\ntries4 ,to rem$y ?is defect ! au?or design$ a ball arrangem5t to ! axis1 :i* p]mits ! level to be set #ae to ! incl9ation ( ! tripod indep5d5tly ( ! screw adju/m5t1 s t ! level1 :5 ! tripod is set at its be/ angle1 may be br\ght imm$iately to ne>ly its f9al position4 ,! arrangem5t is %[n 9 ! engrav+ ,fig4 #gi4 ,! axis c>ries a cup =m$ 9 ! metal ca/+1 :i* c be clamp$ d[n ^u a ball-%ap$ recess =m$ ^u ! tribra* by means ( a w+$ nut plac$ "u x1 ! w+s ( :i* project betwe5 ! tribra* screws4 ,a v slight pressure is suffici5t to firmly clamp ! ball4 ,?is =m ( level is n[ v popul> ) civil eng9e]s4 ,) a po9t diaphragm & a tang5t screw to ! axis1 n %[n 9 ! engrav+1 x is1 9 ! au?or's op9ion1 ! be/ practical level he has be5 able to design4 ,illu/ration3 ,fig4 #hj4--,/anley's ,eng9e]'s level4 ,s9ce ! la/ edition 0 writt5 ! revis] ( ?is "w introduc$1 9 conjunction ) ,mr4 ,/anley1 8 new solid bodi$ eng9e]'s level1 :i* has practically revolutioniz$ ! =m ( dumpy level & has prov$ su* a success t m ( ?is =m are n[ made ?an all o!r =ms put toge!r4 ,9 ?is level1 ,fig4 #hj1 ! c5tre1 body ( telescope1 object end & bubble fitt+ are all comb9$ 9 "o piece ( gun-metal1 s t al?\gh ( va/ly great] /r5g? & rigidity x does n weigh z mu* z ! old =m ( tubul> body ) its coll> & /age4 ,?is does away ) _m sep>ate pieces :i* are usually sold]$ & screw$ toge!r4 ,x ?us =ms ! /ronge/ & mo/ compact level yet made1 & ) ord9>y c>e x w la/ 9 p]fect adju/m5t a lifetime4 ,! p9ion = focuss+ is fitt$ to ! side ( ! ca/ body1 in/ead ( to a tube1 ?us greatly increas+ its firmness4 ,its =m is equally adapt$ to ! f\r-screw levell+ if desir$1 z %[n on next page1 ,fig4 #ha1 9 :i* x w be se5 ! f\r-screw levell+ is ( mu* improv$ =m1 giv+ great] /r5g? & f> m we>+ & be>+ surface to ! levell+ screws4 ,illu/ration3 ,fig4 #ha4--,/anley's ,eng9e]'s level4 ,! revis] has also pat5t$ a new =m ( sph]ical jo9t1 :i* has met ) equal fav\r4 ,?is improvem5t consi/s ( a section ( a ball 7screw$ to fit ! /& head7 fitt$ )9 ! l[] plate & a simple means ( clamp+ x 9 any position1 :i*1 :5 releas$ all[s ( suffici5t rock+ movem5t 9 any direction to comp5sate = any unev5 sett+ up ( ! /&4 ,x does n add to ! height ( ! in/rum5t1 may be in/antly set ne>ly level1 & less ?an half a turn ( ! levell+ screws w br+ ! in/rum5t into true position4 ,x is %[n fitt$ to ! new eng9e]'s level at ,fig4 #hb bel[1 b is equally applicable to any o!r =m ( in/rum5t4 ,illu/ration3 ,fig4 #hb4--,/anley's ,eng9e]'s level fitt$ ) quick sett+ sph]ical l[] plate4 ,z n9ety p] c5t4 ( ! ord]s n[ = levels are = ! =m %[n at ,fig4 #hb1 ! revis] v5tures to ?9k t ?is mu/ be fav\r$ by ! pr(ession z ! be/ practical in/rum5t yet made4 ,a fur!r improvem5t has be5 made by mak+ ! diaphragms int]*angeable1 s t any =m ( diaphragm t is pref]r$ may be in/antly fitt$ )\t di/urb+ ! adju/m5t1 & :5 l9es on glass are us$ x may be remov$ = clean+1 & replac$ )\t int]f]+ ) ! adju/m5t4 ,! diaphragms illu/rat$ bel[1 ,fig4 #hc1 are usual =ms1 & x is recomm5d$ t :5 webs are pref]r$ a glass "o %\ld be c>ri$ z a sp>e 9 case ( accid5ts4 ,illu/ration3 ,fig4 #hc4 ,e ,/adia po9ts = clamp & tang5t levels4 ,f ,/adia po9ts = ord9>y levels4 ,g ,/adia glass diaphragm4 ,h ,webs4 ,j ,/adia webs4 #bda4--,! fur!r discussion ( ! subject ( high-class levels becomes some:at difficult4 ,leav+ out ( consid]ation ! levels sold by ! trad+ optician1 :o deals 9 ! comm]cial article b sometimes sup]adds a little fad1 e g5u9e manufactur] has 8 pet plans ( c>ry+ out details1 "s ( :i* may be v m]itori\s1 b :i* c\ld sc>cely be describ$ )\t a full] discussion ?an our space p]mits4 ,!re is also1 no d\bt1 a great numb] ( mi/akes t h be5 made 9 ! con/ruction ( surveyor's levels4 ,! direction 9 :i* ! sci5tific optician g5]ally fixes 8 att5tion is to give ! advantages ( ! ,y-level 9 ! dumpy =m1 assum+ ! civil eng9e] holds a c]ta9 am\nt ( prejudice aga9/ ! use ( ! ,y1 = :i*1 9 its old =m at lea/1 ! writ] mu/ admit t he 0 fully ju/ifi$4 ,:e!r ! pr(essional man1 nev]!less1 w ev] dep>t f ! solid con/ruction ( ! dumpy rema9s an op5 "q4 ,illu/ration3 ,fig4 #hd4--;,cu%+'s #ab-;in* improv$ level4 #bdb4--;,cu%+'s ,level4--,! level illu/rat$ above1 ,fig4 #hd1 by ! late ,mr4 ,?os4 ,cu%+1 ,f4,r4,a4,s41 ,inspector ( ,sci5tific ,in/rum5ts = ,india1 w\ld "u any circum/ances claim att5tion1 f ?is g5tleman's well-kn[n high te*nical sci5tific atta9m5ts4 ,x has also ! m]it ( be+ 9 practical use 9 ,india at ! pres5t "t4#d ,! pr9cipal improvem5t 9 ?is in/rum5t ov] ! dumpy =m1 :i* x o!rwise repres5ts1 is 9 ! con/ruction ( ! telescope1 :i* is said to possess all ! necess>y adju/m5ts ( ! ,y-level4 ,! telescope is firmly fix$ 9 coll>s sold]$ to ! tube1 z 9 ! dumpy4 ,! tube at ea* end is =m$ into a /\t socket coll>4 ,^! socket coll>s are exactly alike1 & are gr\nd to fit ei!r ! objective or ! eye-piece end ( ! telescope1 s t ^! p>ts may be rev]s$1 ! "o = ! o!r4 ,?is rev]s+ is ne>ly equival5t to turn+ ! telescope end = end 9 ! ,y-level4 ,! end also rotates 9 its fitt+1 :i* is ne>ly equival5t to rotat+ ! telescope half a revolution 9 ! ,y-level4 ,! rev]sible ends ( ! telescope are held 9 _! gr\nd fitt+s by /uds & slides 7bayonet not*es74 ,x is easily se5 t by ?is plan adju/m5ts may be made ( collimation & ( fix+ ! l9e ( collimation p]p5dicul> to ! v]tical axis1 z ) ! ,y-level1 if ! object-glass be orig9ally correctly c5tr$4 ,! /op is ( ! slide =m describ$ = ! dumpy1 ,fig4 #fa1 & a glass diaphragm is us$4 ,"o important arrangem5t is also made 9 ?is "p ( ! in/rum5t--:i* is necess>y1 z glasses become frequ5tly b$ew$ 9 ! telescope--viz41 t ! eye-piece end may be remov$ f its gr\nd fitt+ & ! glass clean$ & replac$ )\t di/urb+ ! adju/m5t 9 any injuri\s degree4 ,! g5]al con/ruction ( ! in/rum5t c be se5 f ! illu/ration4 ,! supports ( ! telescope h a rock+ axis at "o end1 & are adju/$ by cap/an-head$ nuts at ! o!r4 ,! adju/able support = sett+ up ! in/rum5t is ^u ,ev]e/'s tribra* sy/em = !odolites1 to be describ$ fur!r on1 9 ,*apt] ,,ix4 ,! tripod head has also wid] be>+ ?an is g5]al1 :i* is atta9$ by ext5d+ ! book-plates into ! =m ( a socket fitt+4 ,! illu/ration giv5 is ( a #ab-;in* level2 9 ! #ad-;in* an op5 fram$ /& is us$ 9 place ( ! solid tripod1 z 9 ,fig4 #gh1 :i* w be describ$ fur!r on1 = !odolites4 ,! level is a decid$ly good "o2 b ! au?or has exp]i5c$ ) x "s slight defects :5 comp>$ ) 8 own ,y =m4 ,! gr\nd coll>s are a little incl9$ to bite1 p>ticul>ly if ! in/rum5t has be5 laid by = "s "t1 s t 9 rev]s+ = adju/m5t !re is great risk ( di/urb+ ! in/rum5t4 ,! glass index1 al?\gh p]man5t1 has ! same defect z ! web--( cov]+ ! image ( ! /aff read+4 ,x also ob/ructs a little light1 & is subject to dew1 :i* ! po9t sy/em avoids4 ,! weight ( ! in/rum5t is increas$ by ! coll> fitt+s4 #bdc4--;,cooke's ,level4--,an in/rum5t some:at equival5t to ! above has be5 pat5t$ by ,messrs4 ,t4 ,cooke ,sons4 ,9 ?is1 in/ead ( ! objective & eye-piece ends ( ! telescope only be+ rev]sible 9 ! coll> fitt+s1 z 9 ,mr4 ,cu%+'s level1 ! entire telescope rev]ses end = end 9 an extra out] tube1 :i* is fitt$ betwe5 ! coll>s4 ,?is tube also p]mits ! rotation ( ! :ole optical p>ts ab\t ! axis ( ! telescope = adju/m5t = collimation1 al?\gh 9 a mann] m frictional1 & !re=e m likely to di/urb ! in/rum5t ?an 9 ! simple ,y adju/m5t4 ,9 ?is in/rum5t1 aga91 x is easily se5 t x is ! p]fection ( ! ,y-level1 )\t its outw>d appe>ance1 t is aim$ at1 & to ga9 ?is ! weight is increas$ by extra fitt+s & d\ble tubes1 :i* are liable to become fix$ by a slight d5t ^u ! out] tube4 ,tak5 altoge!r x is n q s conv5i5t or s simple z ! be/ con/ruct$ ,y-level2 b if x gives ! adju/m5ts ! optician holds to be mo/ important1 9 a disguis$ =m x may be acceptable to ! civil eng9e]4 ,we may 9 ?is mann]1 p]haps1 f ! optician's po9t ( view1 c\nt x a c]ta9 ga9 9 ! same direction z ,mr4 ,cu%+'s level j describ$2 b if we may accept ! late ,mr4 ,wm4 ,gravatt's ideas1 already m5tion$1 ! complication is unnecess>y4 #bdd4--;,a few o!r /ructural v>iations ( details may be m5tion$1 z ^! are con/antly cropp+ up z new inv5tions4 ,! bubble tube is sometimes plac$ ^u ! /age in/ead ( be+ ^u ! telescope4 ,?is is ?\ght to protect x4 ,x is n1 h[ev]1 s easy to read x 9 ?is position4 ,! compass is sometimes made a loose "p--:5 x is n requir$ on ! "w its weight is sav$4 ,v>i\s =ms ( lock+ screws are made to ! supports ( ! telescope2 ^! are only necess>y to correct imp]fect "w4 ,! axis coll> is sometimes ext5d$ to a limb be>+4 ,?is is common 9 ,fr5* in/rum5ts2 x makes ! movem5t /iff]1 & is q unnecess>y unless ! axis is made too %ort4 ,a well-kn[n ,g]man firm rec5tly br\ght out a level ) int]nal focuss+1 by means ( an auxili>y l5s m\nt$ 9 a tube inside ! telescope1 mov$ by a rack & p9ion1 b any int]nal l5s is a s\rce ( tr\ble1 z x _c be got at to be clean$1 & 9 hot1 damp climates x becomes b$ew$4 ,! device is v old1 hav+ be5 pat5t$ 9 ,am]ica _m ye>s ago & disc>d$4 #bde4--,supplem5t>y ,p>ts to ,levels4--,z a rule1 supplem5t>y p>ts fix$ to ! in/rum5t1 beyond ! magnetic compass sometimes requir$1 are v objectionable if ! object ( ! level is to be levell+1 z ^! additional p>ts inevitably increase ! weight :i* has con/antly to be borne 9 c>ry+ ! in/rum5t4 ,supplem5t>y p>ts h be5 c>ri$1 9 v>i\s s*emes1 to ! ext5t ( comb9+ ! entire level ) ! !odolite1 at ! same "t ne>ly comb9+ ! unit$ weights ( ! two in/rum5ts4 ,z a rule1 pr(essional m5 r>ely c>e = complex comb9ations2 & ev5 aft] a limit$ popul>ity is grant$ to extra p>ts n absolutely requir$1 ^! are g5]ally f9ally ab&on$4 ,m5tion ( two su* p>ts1 !re=e1 only w be made1 z ^! owe _! introduction to ! late ,william ,gravatt1 & are f\nd appli$ to _m levels 9 use1 or at lea/ conta9$ 9 ! case ) ! in/rum5t4 #bdf4--;,bubble ,reflector4--,?is 0 =m]ly plac$ ^u all dumpy levels4 ,x consi/s ( a small mirror ab\t #b in*es by #e_/h in* fix$ 9 a frame t is jo9t$ at its l[] end to a %ort piece ( tube p>tly cut away s z to =m only a little ov] a semi-cyl9d]4 ,?is tubul> "p j clips firmly ^u ! brass cas+ tube ( ! _s level4 ,! reflector1 :5 plac$ v]tically on ! level tube1 c be adju/$ by its jo9t1 s t ! run ( ! bubble may be obs]v$ by reflection 9 look+ above ! eye-piece to see t x is 9 adju/m5t at ! "t ( tak+ an obs]vation4 ,its use 0 ?\ght to be a precaution 9 levell+1 p>ticul>ly on m>%y gr\nd4 ,! obs]vation ( ! bubble is less exact ?an by a side read+1 & _c be reli$ on4 ,illu/ration3 ,fig4 #he4--;,compact *eap =m ( dumpy level4 #bdg4--,sight ,vanes4--,two sight vanes are plac$ above ! telescope1 ei!r z loose fitt+s or to h+e d[n ^u ! level tube4 ,"o vane has a v]tical n>r[ slit & cross hair2 ! o!r has a w9d[ ) a v]tical horse-hair plac$ 9 its c5tre4 ,?is arrangem5t gives sight ( di/ant l&m>ks 9 l9e ) ! direction ( ! telescope1 upw>ds or d[nw>ds1 beyond its field ( view4 ,a slid]1 fix$ ^u ! w9d[ sight1 reads at its upp] edge into divisions cut on ! vane1 by means ( :i* an approximate rate ( =w>d incl9ation ( ! l& may be tak54 ,?is sight+ arrangem5t adds ab\t half a p\nd weight to ! in/rum5t4 ,x 0 useful ) object-glasses ( small field ( view1 b is useless ) good mod]n glasses ( wide angle4 #bdh4--,l[]-class ,levels4--,a level is (t5 requir$ by an ar*itect or a contractor = works ( limit$ area1 :]e x is q unnecess>y to g to ! exp5se ( a civil eng9e]'s level ( ref9$ manufacture4 ,9 su* cases ! level may only be us$ occasionally & "u fav\rable circum/ances1 s t extreme solidity is n dem&$1 nei!r is di/ant view 9 ! telescope requir$4 ,! level g5]ally made = su* "w is a simple dumpy1 )\t cross bubble1 compass1 or any extra fitt+s1 & ) "o eye-piece only4 #bdi4--,! in/rum5t ,fig4 #he illu/rates ! au?or's newe/ design = a simple level4 ,x has a light =m ( tripod4 ,! legs clamp directly betwe5 angle plates--^! are n q s portable or s neat z cyl9drical legs1 b !y are easily made1 v firm1 & w be> consid]able we> & keep 9 ord]4 ,a /ill *eap] =m is made ) small] telescope & turn$ legs = ! tripod4 ,illu/ration3 ,fig4 #hf4--;,contractor's or build]'s level4 #bej4--,! illu/ration ,fig4 #hf repres5ts ! *eape/ =m ( level ) a tripod /& t has be5 con/ruct$1 :i* conta9s ! important factor ( a telescope4 ,! telescope has a slid+ fitt+1 :i* is mov$ by a knob outside1 ?is be+ made m quickly ?an a rack & p9ion fitt+4 ,! level tube is solidly support$ 9 coll>s4 ,! adju/m5t is 9 "o direction only1 s t ! bubble mu/ be set & exam9$ at ! "t ( read+ ! /aff4 ,! in/rum5t is support$ on a sprang1 jo9t$ at "o end & held by a mill$-head$ screw at ! o!r4 ,any %ak9ess ( ! ?read ( screw !re may be is tak5 up by a /iff ,g]man silv] spr+ betwe5 ! sprang & ! limb4 ,x is sometimes made ) a ball & socket jo9t = fir/ adju/m5t1 b ?is r5d]s x ne>ly z co/ly z a sup]ior level4 ,! tripod head is ( simple con/ruction4 ,! legs are oak or a%1 & are clamp$ on ! head by bolts4 ,?is simple tripod is fairly firm 9 use4 ,! level is good en\gh = ord9>y build+ works1 lay+ %ort dra9s1 etc41 )9 limit$ areas4 ,x is mu* m accurate ?an any =m ( op5 sight$ level )\t telescope4 ,sir ,george ,lea* has rec5tly made a modification ( ?is old =m ( level by plac+ a p5dulum to rock ! axis to cross level position1 :i* is a ref9em5t1 al?\gh r a co/ly "o4 ,illu/ration3 ,fig4 #hg4--,sight$ reflect+ pocket level4 #bea4--,sight$ ,pocket ,level4--,?is consi/s ( a tube1 :i* is g5]ally drawn ( squ>e section4 ,a p9-hole sight is made 9 ! clos$ end ( ! tube1 ,fig4 #hg1 at ,e4 ,! field end ( ! tube is left op54 ,! sight is tak5 by look+ ?r\gh ! c5tre ( ! p9-hole across ! edge ( ! reflector ,r4 ,a level ) a small bubble is plac$ or ins]t$ 9 ! top ( ! tube at ,b4 ,! metal cas+ ( ?is is cut away on ! upp] & "u sides to r5d] ! bubble visible f ! int]ior ( ! tube by means ( ! reflector ,r1 :i* occupies "o half v]tical section ( ! int]ior ( ! tube4 ,?is is plac$ at #de to ! axis4 ,! reflector is fix$ ^u an inn] tube s t x may be )drawn to be clean$4 ,:5 ! level is set horizontally1 a di/ant object 9 ! direct sight l9e is se5 ?r\gh half ! tube1 & simultane\sly ! reflection ( ! bubble 9 ! o!r half appe>s4 ,a l9e engrav$ ^u ,r indicates :5 ! bubble is c5tral1 & :5 ^! co9cide ! di/ant object & ! eye are level4 ,! in/rum5t is ab\t #d in*es long1 & weighs ab\t #h oz4 9 its case4 ,illu/ration3 ,fig4 #hh4--,pocket telescopic level4 #beb4--,pocket ,telescopic ,level4--,9 ! above-describ$ pocket level1 :]e x is made %ort1 ! av]age middle-ag$ man w n h suffici5t accommodation ( vision to be able to see ! bubble & ! scre5 %>ply def9$ simultane\sly ) ! di/ant object to :i* ! level is to be tak54 ,9 ,capta9 ,b>rie's#e level ^! objections are avoid$ by mak+ ! reflector & bubble =m "p ( a telescope1 ,fig4 #hh4 ,an a*romatic glass ( %ort focus is us$1 & ! eye-piece is ( long focus s z to br+ ! bubble to focus 9 ! c5tre ( ! mirror1 :i* is made ( curv$ =m to decrease ! app>5t size ( ! bubble4 ,! image ( ! bubble does n give by bisection a v def9ite index4 ,! au?or has f\nd t ?is level may be mu* improv$ by plac+ a po9t 9 ! telescope at ! mutual foci ( ! object-glass1 eye-piece & ! bubble4 ,! appe>ance ( ! mirror & po9t is %[n at ,b4 ,! po9t is %[n by a dot at ,p4 ,! curv$ mirror ,r4 ,! dott$ l9e %[s ! pa? ( reflection f ! bubble4 ,?is level w "w ) v fair accuracy z a h& in/rum5t4 ,size1 ab\t #d in*es by in*4 ,weight 9 case1 ab\t #h oz4 ,illu/ration3 ,fig4 #hi4--,reflect+ level4 ,illu/ration3 ,fig4 #ij4--,! same con/ruction 9 protect+ case4 #bec4--,reflect+ ,level4--,?is simple level1 ,fig4 #hi1 ! inv5tion ( ,colonel ,burel1 is "o ( ! mo/ portable4 ,:5 x is us$ ) a fair am\nt ( c>e x w give good approximate results4 ,x consi/s ( a piece ( p>allel glass1 :i* has half ! surface silv]$ to =m a reflector4 ,x is susp5d$ 9 su* a mann] t ! glass hangs v]tically by gravitation4 ,! position ( ! mirror to ! pla9 glass may be t %[n 9 ! engrav+1 or horizontally if pref]r$4 ,! mirror1 ,fig4 #hi1 is ins]t$ 9 a solid metal frame susp5d$ f a gimbal1 :i* p]mits x to hang p]fectly free to ! action ( gravitation4 ,! c5tres ( susp5sion are made ) slightly-r\nd$ knife-edges4 ,a r+ at ! upp] "p ( ! in/rum5t is plac$ ov] ! ?umb or f+] to support ! in/rum5t :5 9 use4 ,a /\t p9 passes ?r\gh a prolongation ( ! l[] "p ( ! frame1 screw$ or o!rwise1 :i* p]mits adju/m5t by fil+ to br+ ! mirror :5 x is susp5d$ exactly into a v]tical plane4 ,! in/rum5t1 fitt$ into a neat case1 weighs f #e oz4 to #i oz4 #bed4--;,9 us+ ! ,reflect+ ,level1 x is held ^u ! ?umb at ab\t arm's l5g?1 & adju/$ by rais+ or l[]+ ! arm until ! reflection ( ! pupil ( ! eye se5 9 ! mirror is exactly bisect$ by ! l9e cut by ! mirror aga9/ ! cle> glass4 ,! di/ant object se5 9 front1 t cuts ?is sight l9e & ! image ( ! pupil ( ! eye1 w !n be 9 true level position ) ! eye ( ! obs]v]1 provid$ ! air is /ill1 s t ! mirror is n deflect$ f v]ticality4 ,f ! natural un/ead9ess ( ! h& !re is "s little difficulty ( gett+ ?is level q free f oscillation4 ,?is may be obviat$1 or ne>ly s1 by clut*+ a picket or /aff ) ! h& & susp5d+ ! level f ! ?umb project$ out = ! purpose1 or by re/+ ! h& aga9/ a tree or o!r firm support4 ,capt4 ,a4 ,h4 ,ea/1 ,r4,a41 has sugge/$ to ! au?or a v capital device :i* he employs = h& in/rum5ts4 ,?is is to place ! h&le ( a /ick 7or umbrella7 9 ! wai/coat pocket1 to clut* ! body ( ! /ick ) ! h& :i* holds ! in/rum5t1 & to /eady x ) ! o!r h&4 ,9 ?is mann] ! two arms & ! /ick =m a tripod ( surpris+ /ead9ess4 #bee4--,reflect+ ,level 9 ,case4--,9 w9dy wea!r mu* great] exactness may be secur$ by plac+ ! p5dul\s level1 j describ$1 9 a tubul> case1 ,fig4 #ij4 ,! case is made ( d\ble tubes1 s t ! ap]ture cut on "o side may by a half turn ( ! out] tube close & protect ! in/rum5t :5 out ( use4 ,! transp>5t side ( ! inn] case is sometimes clos$ by ?9 glass tube ( its own int]nal diamet]4 ,x is mu* bett] if made ) two v]tical sides glaz$ ) p>allel glass4 ,:5 ?is =m ( in/rum5t is us$1 x may be1 if requir$1 made to fit on ! top ( a light /aff4 ,! eye is !n br\ght ) mu* great] c]ta9ty to ! po9t ( bisection on ! edge ( ! mirror1 & mu* great] accuracy is ?us atta9$ 9 levell+ ) x4 #bef4--,wat] ,levels4--,! antique =m ( level1 compos$ ( two vials fix$ on ! ends ( a tube & p>tly fill$ ) wat]1 by :i* a level is sight$ 9 look+ ov] ! surface ( ! wat]1 is /ill us$ to a limit$ ext5t 9 rural di/ricts on ! ,cont95t2 b ! _s level 9 "s simple =m is fa/ sup]s$+ x4 ,! same pr9ciple ( level1 b ) long tube1 has be5 f\nd conv5i5t = ! surveyor 9 measur+ ?r\gh close build+s1 ,fig4 #ia4 ,illu/ration3 ,fig4 #ia4--,tubul> wat] level ) op5 vials4 ,illu/ration3 ,fig4 #ib4--;,br[ne's /&>d wat] level4 #beg4--;,br[ne's ,wat] ,level#f is f\nd to be a conv5i5t in/rum5t = levell+ 9 close t[ns4 ,x consi/s ( a pair ( glass tubes ( ab\t #b feet 9 l5g?1 plac$ 9 a cas+ tube = protection4 ,! cas+ tube is divid$ into in*es & p>ts1 or ! scale is a deta*$ piece ( pa9t$ wood1 or any rod or rule4 ,a cock at ! bottom admits ! wat] to fl[ to level 9 ! pair ( tubes1 "o ( :i* is %[n1 ,fig4 #ib4 ,!re is a h&le at ! top :i* unscrews to fill ! level1 & a small air cock4 ,x is easily se5 t ! wat] f9ds its level1 & ! diff]5ce ( read+ ( ! two /&>ds is ! diff]5ce ( level ( ! surfaces ^u :i* !y are plac$4 ,by clos+ ! cocks ! level is made portable4 ,9 ?is position x does n matt] h[ high ! c5tre ( ! pipe is plac$--= in/ance1 9 cross+ ov] a wall--z ! wat] w /ill f9d its level :5 ! cocks are releas$ by syphon+ ! wat] f ! "o side or ! o!r4 ,x is a v conv5i5t & exact level = lay+ dra9 pipes 9 op5 wea!r1 & = mak+ f\ndations = heavy ma*9]y1 etc41 b ( c\rse x w n /& fro/4 ,platelay]s' levels & me*anics' levels g5]ally are def]r$ to consid] ) useful h& tools & app>atus employ$ by surveyors 9 ! f9al *apt]4 ,,footnotes3 #c ,see ,simms' ,ma!matical ,in/rum5ts1 p4 #c4 #d ,see pamphlet on ,a ,new ,=m ( ,levell+ ,in/rum5t1 by ,?os4 ,cu%+1 ,f4,r4,a4,s41 #ahgi4 #e ,pat5t ,no4 #fi1 ,wm4 ,b>rie1 #ahef4 #f ,pat5t ,no4 #fgdb1 ,john ,br[ne1 ,june1 #ahcd4 ,,*apt] ,v4 ,,levell+ ,,/aves--,,con/ruction--,,v>i\s ,,read+s ,,discuss$-- ,,sop)',s--,,field',s--,,/range',s--,,/a nley',s ,,new--,,metrical--,,simple ,,con/ruction ,,m9+ ,,/aff--,,pap]$ ,,levell+ ,,/aff-- ,,pres]vation--,,pack+ ,,pads--,,/aff ,,plate--,,/aff ,,level--,,practice ,,( ,,levell+--,,index ,,( ,,bubble--,,lamp--,,curvature ,,corrections--,,/ation ,,pegs--,,ref9em5t ,,( ,,levell+--,,levell+ ,,books--,,ink ,,bottle1 ,,etc4 #beh4--,levell+ ,/aves4--,s9ce great improvem5ts h be5 made 9 ! telescopes us$ z "p ( all mod]n surveyors' levels1 p>ticul>ly by increas+ _! light-receiv+ capacity1 all sy/ems ( vanes :i* 7 =m]ly made to be se5 di/9ctly at a di/ance h disappe>$ f use by ,briti% surveyors2 x is n[ f\nd t ! pla9 read+ ( a divid$ /aff c be tak5 by means ( ! telescope at a suffici5t di/ance f ! obs]v] = all practical purposes4 ,9 ?is c\ntry "o con/ruction ( /aff is n[ g5]ally adopt$2 & ! only v>iations t are made 9 ?is are f\nd occasionally 9 ! read+s4 ,! con/ruction ( ! level /aff 9 common use is t inv5t$ by ! late ,?omas ,sop)1#g call$ ! telescopic /aff1 ! face view ( :i* is %[n ,fig4 #if4 ,= ord9>y op5 field "w ?is is made #ad1 #af1 or #ah feet 9 its ext5d$ l5g?2 b g5]ally1 except = levell+ on m\nta9\s l&1 ! #ad feet is us$4 ,?is /aff :5 clos$ is ab\t ! same l5g? z ! tripod1 #e feet #d in*es1 & may be conv5i5tly /[$ away "u ! seat ( a railway c>riage4 ,sop)'s /aff1 z x 0 =m]ly made1 consi/$ ( two squ>e p>allel tubes & "o inn] solid p>allel slide4 ,made 9 ?is mann] x 0 liable to be r %aky :5 ext5d$1 besides :i* x frequ5tly got jamm$ 9 ! telescopic boxes if put away damp f ra93 ?is t5d$ at fir/ to limit its use4 ,x is n[ usual to make ! boxes slightly conical1 t is1 dim9i%$ t[>ds ! upp] "p1 s t !y are rigid :5 op5$ out b are v free :5 clos$1 :i* q rem$ies ! defects j m5tion$4 ,illu/ration3 ,figs4 #ic1 #id4--,section ( ,sop)'s /aff4 #bei4--,! ord9>y con/ruction ( ,sop)'s /aff & ! be/ mode ( manufacture is %[n1 ) ! jo9ts groov$ toge!r1 9 section ,fig4 #ic4 ,! out] tube or case ,a1 :i* 9 ! #ad-;feet /aff is #e feet 9 l5g?1 is made ( mahogany #e_/af in* ?ick1 ! front be+ in*4 ,! out] dim5sions ( ! section are #c-a_/h in*es by #b in*es4 ,! second tube ,b is #e feet #a in* long1 ( out] dim5sions #b-c_/h in*es by #a in*es4 ,! inn] slide ,c is solid1 #e feet #b in*es long1 #a in*es by in*4 ,all ! slides are sunk on ! face ab\t #a_/af in* to prev5t ! divisions be+ rubb$ by exposure 9 slid+ toge!r4 ,! slides h ea* a brass %oe & cap4 ,!y are held :5 ext5d$ by a spr+ cat*1 ! detail ( :i* is %[n 9 ,fig4 #id1 section y to z ( ,fig4 #ic--,s spr+ ( ,t =m screw$ firmly to ! edges ( ! box4 ,! cat* is made at ,a ov] ! edge ( ! brass cap ,a4 ,! spr+ %\ld be ( v h>d roll$ brass4 ,x is well to h "o or two brass b&s r\nd ! body ( ! out] cas+ to secure ?is z f> z possible f be+ split by accid5t4 #bfj4--,! mo/ important consid]ation 9 ! manufacture is t ! telescopic "w %\ld fit well1 & t ! boxes %\ld be glu$ up q squ>e & out ( w9d+4 ,! boxes %\ld1 aft] ! glue is q set1 be screw$ ) brass screws at di/ances ( ab\t #f in*es ap>t1 to secure ! jo9ts :i* may aft]w>ds 9 use be expos$ to long-cont9u$ ra94 ,! fitt+s %\ld be c>efully made1 s t :5 ! /aff is ext5d$ !re %\ld be no %ak9ess suffici5t to cause s]i\s vibration :5 x is us$ 9 w9dy wea!r4 ,! int]ior ( ! slides :5 f9i%$ %\ld be ?or\ghly oil$ ) raw l9se$ oil1 & ! out] surfaces be well soak$ 9 %ellac dissolv$ 9 _s1 & !n ,fr5* poli%$ ov] ?is4 ,! brass "w %\ld be well lacqu]$4 ,illu/ration3 ,fig4 #ie4--,section ( semi-cyl9drical /aff4 #bfa4--,semi-circul> ,/aff4--,?is is ano!r k9d ( telescopic /aff1 ) ,sop) slid+ arrangem5t1 :i* possesses a c]ta9 m]it1 b is m exp5sive to make4 ,x is semi-cyl9drical1 ! cyl9drical "p be+ made )\t any jo9t4 ,?is is %[n 9 ! section ,fig4 #ie4 ,! g5]al dim5sions ( ! face ( ! /aff are ! same z ^? giv5 = ! ,sop) /aff4 ,?is /aff is a little /iff]1 b !re is m risk ( its n /&+ true4 ,z 9 ! union ( f\r pieces ( wood 9 ! squ>e =m1 previ\sly describ$1 ! t5d5cy ( "o piece to w>p 9 a c]ta9 direction is resi/$ by ! o!r pieces2 b 9 ?is cyl9drical =m !re is no su* resi/ance1 s t x is f\nd t ^! /aves :5 expos$ to wet are mu* m liable to become w>p$ & fix$ 9 _! slides4 ,!re is also m difficulty 9 gett+ ! conical =m fairly accurate 9 ! work+4 ,"o p>ticul> m]it1 :5 a pair ( /aves ( ?is k9d is us$1 is t ! two g toge!r & =m a cyl9d]1 :i* is a v compact =m1 b p]haps a little m difficult to c>ry1 ow+ to ! t5d5cy ( a cyl9d] to roll (f ! %\ld]4 ,illu/ration3 ,fig4 #if4--,sop) patt]n /aff4 ,illu/ration3 ,fig4 #ig4--;,field's patt]n4 ,illu/ration3 ,fig4 #ih4--,/anley's old patt]n4 #bfb4--,:at 0 orig9ally consid]$ z ! defect ( ! ,sop) /aff1 besides its %ak9ess1 z x 0 fir/ made1 0 ! dim9i%$ wid? ( read+ ( ! upp] l5g?1 ?is be+ only #a in*es wide4 ,?is caus$ = a long p]iod o!r =ms ( /aves1 :i* ma9ta9$ ! same wid? ( read+ surface q to ! top1 to be pref]r$ by _m4 ,?is fault has be5 p>tly rem$i$ by ! au?or 9 mak+ ! feet read+s ( ! upp] /aff by dots1 in/ead ( ! n>r[ figures1 :i* 7 v difficult to read4 ,9 o!r respects ! light & portable =m ( ! ,sop) /aff has ensur$ its g5]al use4 ,illu/ration3 ,fig4 #ii4--,sop)'s /aff4 ,illu/ration3 ,fig4 #ajj4--,rog]s ,field's /aff4 ,illu/ration3 ,fig4 #aja4--;,col4 ,/range's /aff4 #bfc4--,! orig9al =m ( read+ design$ by ,sop) is /ill mu* m 9 use ?an any o!r4 ,x is simil> 9 patt]n to ,fig4 #if1 %[n 9 detail = #a foot ,fig4 #ii4 ,! dots at ! end ( ! l9es %[n 9 ! figure 7 introduc$ by ! au?or to r5d] ?is /aff m di/9ct ?an :5 l9es only are us$1 z 9 ! ord9>y patt]n4 #bfd4--,sop)'s patt]n is sometimes pr9t$ on pap] = pa/+ on ! /aff1 & 9 ?is mann] ! /aff comes out mu* *eap] ?an by draw+ ! read+s 9 solid pa9t4 ,pa9t1 h[ev]1 is /rongly recomm5d$1 n only because x we>s mu* bett] & keeps clean]1 b t ! pa9t+ & v>ni%+ add v mu* to ! durability ( ! /aff1 expos$ z x mu/ necess>ily be to ra9y wea!r2 fur!r1 ! pap]1 h[ev] well x is fix$ at fir/1 is liable to creep away f ! edges ( ! /aff1 & leave a space into :i* ra9 ent]s v freely by capill>y attraction2 b x does n aga9 freely evaporate1 s t x rots ! /aff & makes ! pap] read+ aft] a "t m\ldy4 ,x is1 nev]!less1 conv5i5t to take a set ( fir/ l5g? pap]s if a surveyor is go+ abroad1 z f accid5ts--graz+ by c>ry+ ! /aff ) ! tripod ( ! level1 etc4--! fir/ l5g? ( surface is v liable to become too mu* injur$ & effac$ = fair read+4 ,a description ( fix+ ! pap] w be giv5 fur!r on4 #bfe4--;,= ,read+ ! ,sop) ,/aff1 ! foot read+s are tak5 f ! tops ( ! r$ figures4 ,! #a foot figures are 9 black1 & are all odd numb]s1 #a1 #c1 #e1 #g1 #i4 ,^! read also f ! top4 ,! height ( ! figure is exactly #a foot1 s t ! bottom ( ea* figure reads ! l[] ev5 numb]--?us ! bottom ( #c reads #b1 ( #e reads #d1 ( #g reads #f1 & ( #i reads #h4 ,! #f & #i foot figures if made alike1 f effect ( telescopic inv]sion1 may cause error4 ,! au?or has = _m ye>s made ! head ( ! #i a solid black block to avoid ?is4 #bff4--,v>i\s ,read+s4--,a v l>ge numb] ( surveyors design _! own /aff read+s4 ,?is 0 =m]ly v mu* ! fa%ion1 consequ5tly a great numb] ( patt]ns come be=e ! manufactur]4 ,! au?or = ab\t twelve ye>s kept a copy ( :at he consid]$ ! mo/ m]itori\s ( ^! patt]ns1 bo? = future ref]5ce & to judge ( _! comp>ative m]its4 ,?is 0 discont9u$1 z x 0 f\nd t ! numb] ( designs became a little p]plex+1 & !y 7 r dang]\s to %[ to a cu/om]1 :o (t5 select$ f its appe>ance a patt]n :i* prov$ aft]w>ds unsatisfactory 9 use4 #bfg4--,rog]s ,field's & ,colonel ,/range's ,read+s4--,! au?or made "s exp]im5ts to obta9 a cle> /aff1 readable beyond ! ord9>y range ( /aves ) a #ad-;in* level2 b mu* m complete exp]im5ts 7 made ) ! au?or's set ( patt]ns by ,mr4 ,rog]s ,field1 ,c4,e41 ^: +5uity is well kn[n4 ,?is g5tleman f9ally design$ a /aff :i* 9 ! au?or's op9ion is /ill "o ( ! be/1 b x has n g5]ally pleas$ ! pr(ession3 ?is is illu/rat$1 ,figs4 #ig1 #ajj4 ,! au?or has tri$ x at all di/ances3 at #bj *a9s he has f\nd a read+ ( #ja foot c\ld be tak5 approximately ) a good #ad-;in* level ) 8 po9t index-/op level1 ,fig4 #ge4 ,! late ,colonel ,/range made a s]ies ( exp]im5ts ) ! au?or's patt]ns plac$ at #aj & #bj *a9s di/ance4 ,he also _h = ^! exp]im5ts "o ( ,mr4 ,rog]s ,field's /aves4 ,he arriv$ at ! conclusion1 = di/ant read+ p>ticul>ly1 t ! black m>k+s on all ! tw5ty /aff patt]ns he _h 7 excessively heavy1 s t ! lighte/ & mo/ op5 read+s 7 ! cle>e/4 ,?is l$ him to design a /aff1 a "p ( :i* is %[n 9 ,fig4 #aja1 :i* has be5 s9ce g5]ally us$ on ! great ,india survey4 ,?is /aff some:at resembles ! ,engli% ordnance patt]n4 ,! fault f\nd ) ^! patt]ns is t !y d n read ! #ja foot1 :i* is necess>y = close read+ 9 hilly di/ricts1 o!rwise !y may be read v cle>ly at a di/ance ( #bj *a9s1 :]e ! ,sop) becomes a blur4 ,we may take x t ! surveyor1 if he be a fairly good draughtsman1 w\ld subdivide ! #je block to ! #ja foot2 b x is argu$ t 8 assi/ant1 :o might be a fair levell]1 might n4 ,ano!r objection is t ! read+ is on "o side & is n cut ?r\gh by ! horizontal web1 s t a :ite m>g9 c be se5 9 ! telescope on bo? sides ( ! v]tical webs1 betwe5 :i* x is mo/ pleasant & exact t ! read+ %\ld be tak54 ,?is objection does n1 h[ev]1 hold = ! po9t read+1 ,fig4 #ge4 ,colonel ,/range's patt]n has n be5 v g5]ally accept$ by civil eng9e]s4 ,! au?or tri$ to meet ! matt] by mak+ ! block #je foot1 b s subdivid$ z to indicate #ja foot4 ,?is has frequ5tly be5 pref]r$ to 8 dott$ ,sop)4 ,illu/ration3 ,fig4 #ajb4--;,details ( ,/anley /aff2 ,a bottom l5g?1 ,b middle1 ,c top ) dot figures4 #bfh4--,! au?or design$ ano!r /aff especially = 8 po9t index4 ,?is is %[n above1 ,fig4 #ajb4 ,x has _h a v fair popul>ity1 be+ good bo? = di/ant & ne> sight+4 ,9 ?is /aff = ! close figures #aa1 #ab1 #ac1 on a #ad-;feet /aff1 :i* are ) great difficulty di/+ui%able at a di/ance1 ! au?or employs dots only z be=e m5tion$--"o dot = ! #aa1 two = ! #ab1 & ?ree = ! #ac1 z %[n ,c = ! #ab & #ac 9 ! "r-h& figure4 ,x mu/ be rememb]$ t a good cle> /aff is a great desid]atum1 z x means less size1 weight1 & co/ 9 ! level necess>y to be us$ ) x = equal exactness4 ,a cle> /aff ) a #ad-;in* level is q equal to a complex mi/y "o ) a #af-;in* level1 ) ! advantage ( sav+ exp5se 9 ! pur*ase1 & ab\t #b lbs4 9 ! weight ( ! level to be c>ri$ 9 "w4 #bfi4--,our space w n p]mit ! discussion ( ! v>i\s /aff read+s t h be5 design$1 _m ( :i* are1 9 ! au?or's op9ion1 sup]ior to ! ,sop)2 b "s v>iations are necess>y occasionally = p]sonal reasons4 ,"s surveyors1 f imp]fect col\r vision p]haps1 /rongly object to ! r$ foot figure z be+ indi/9ct at a di/ance1 h5ce 9 _m patt]ns a cle> black figure is employ$4 ,"s get confus$ ) ! numb] ( equal l9es ( #ja foot 9 ! ,sop)1 :at is sometimes t]m$ ,sop)'s ladd]4 ,9 ?is case ^! l9es may be made unequal 9 diff]5t ways3 sev]al patt]ns h ?is peculi>ity4 ,"s p]sons _c get ov] ! inv]t$ figure z se5 9 ! telescope4 ,9 ?is case x w\ld be mu* bett]1 p]haps1 to read ) an erect+ eye-piece to ! level2 b practically ! manufactur] has to inv]t ! figures4 ,o!r less important v>iations are common4 #bgj4--,metrical ,/aves4--,^! are 9 ?is c\ntry g5]ally made #ad feet1 to keep ! l5g? ! same z ! tripod4 ,! mo/ approv$ patt]ns are %[n ,figs4 #ajc & #ajc;,a4 ,9 us+ ! metre patt]n at %ort di/ances (t5 a complete metre _c be tak5 9 ! field ( view1 s t !re is a little difficulty 9 be+ c]ta9 to :at metre int]space ! subdivisions belong4 ,to avoid ?is ! au?or places a dot or dots aft] ! decimetre figures t foll[ ! metre--"o dot = #a metre1 two dots = #b metres1 ?ree dots = #c metres4 ,?us #ad metre reads #d2 #bd metre reads 3#d4 ,! dots ne$ only be v small1 z !y are n requir$ except = v close read+s1 t is1 )9 ab\t #cj metres3 at #dj metres di/ance "o complete metre comes into ! ord9>y telescopic field4 ,illu/ration3 ,fig4 #ajc4--,metres & ,half ,c5timetres4 ,fig4 #ajc;,a4--,c5timetres4 ,/anley's metre levell+ /aves4 #bga4--;,feet & ,in*es ,/aff4--,= build+ works1 dra9age1 & "s o!r cases1 ! /aff is divid$ into feet & in*es1 & subdivid$ aga9 into eigh?s or t5?s ( in*es4 ,?is is mo/ conv5i5t :5 ! "w has to be c>ri$ out ) #e or #aj feet rods & ! #b-;feet rule4 ,! int]m$iate in*es betwe5 ! feet are bett] m>k$ #c1 #f1 #i only ?an fully figur$4 ,= r\gh usage ! au?or has made a solid #aj-;feet p9e /aff1 well pa9t$4 ,?is has a /rong h+e 9 ! c5tre1 & is kept /iff :5 op5 by a /rong op5 hook4 ,x closes face to face 9 two p>ts1 :i* keeps ! face clean4 ,?is is important = dock & dra9age works1 :]e ! /aff hold]'s h&s 9 _m cases necess>ily get dirty by climb+2 o!rwise x be>s mu* m r\gh usage ?an ! telescopic /aff1 & is mu* *eap] to make4 ,fig4 #ajd4 ,illu/ration3 ,fig4 #ajd4--,/anley's r\gh levell+ /aff4 #bgb4--,m9+ ,/aves4--,= levell+ 9 m9es1 l>ge sew]s1 & o!r cases 7 !re is no height = ! ord9>y /aff1 ! ,sop) /aff is made 9 its clos$ =m commonly #b feet #c in*es & #c feet #c in*es only 9 l5g?1 to op5 out respectively #e feet & #h feet1 or 9 "s few in/ances ev5 %ort] ?an ^! dim5sions4 ,! m9e /aff is 9 e way1 except its l5g?1 simil> to ! ord9>y ,sop)1 art4 #bei4 ,illu/ration3 ,fig4 #aje4--,/anley's pat5t$ m9e /aff4 #bgc4--,/anley's ,portable ,/aff4--,! writ] has made a portable /aff 9 l5g?s ( #ah in*es1 some:at l a ,fr5* fold+ rule4 ,x may be =m$ ( ?ree1 f\r1 five1 or six l5g?s1 op5+ out respectively #d feet #f in*es1 #f feet1 #g feet #f in*es1 & #i feet4 ,! sep>ate pieces are flat bo>ds1 slightly sunk on ! face to prev5t ! divisions be+ scrat*$ 9 op5+ & clos+1 b left solid at ! jo9t ends4 ,! bo>ds are atta*$ toge!r ) a k9d ( rivet at ea* jo9t4 ,a /rong spr+ at ! end ( ea* piece ) a cat* & not* keeps ! l5g? op5$ or clos$ ) suffici5t rigidity4#h ,! entire l5g? ( ! /aff :5 clos$ 9 #bj in*es4 ,! same k9d ( /aff =ms a v useful build]'s or dra9age /aff1 divid$ 9 ?is case 9 feet & in*es2 & x is conv5i5tly portable = c>ry+ abroad4 ,fig4 #aje--;,e %[s back view1 ,f front view1 ,g cross section1 ,a longitud9al section4 ,! hold+ spr+s are %[n at ,,bb,b4 #bgd4--;,a portable m9e /aff design$ by ,mr4 ,g4 ,j4 ,jee1#i is said to be a useful /aff = colli]y "w4 ,x is con/ruct$ 9 ?ree l5g?s1 slid+ "o into ! o!r4 ,! bottom l5g? ( ?ree feet is graduat$ 9 ! ord9>y way4 ,! top ( ?is l5g? has a b& atta*$ to x1 pa9t$ to cont9ue ! l[] division ( ! /aff upw>ds4 ,! o!r end ( ! b& passes ov] a roll] atta*$ to ! top division ( ! /aff4 ,! roll] conta9s a spr+ :i* keeps a con/ant t5sion on ! b&4 ,by ext5d+ ! l5g?s ( ! /aff & clamp+ !m1 ! /aff may be l5g!n$ out any di/ance to #i feet4 ,! weight ( ! /aff is #e lbs4 #bge--,pap]+ or ,repap]+ a ,sop) ,/aff4--,! /aff1 if new1 is pa9t$ ) ?ree coats ( r flat1 ?9 :ite-lead pa9t on ! face1 & left to season till ! pa9t is q h>d4 ,x is !n wa%$ ?or\ghly ) a sponge dipp$ 9 /\t1 until ?is adh]es )\t bead+1 & is aga9 left to dry4 ,= repap]+ an old /aff1 ?is is soak$ ) hot wat] 9 :i* !re is "s wa%+ soda1 & rubb$ until ! old pap] is br\ght (f4 ,aft] ! /aff is 9 ei!r ( ! /ates describ$ above1 x has to be made w>m & coat$ ) "o or two coats ( size4 ,! size may be made ( a piece ( glue left 9 wat] = a night1 & !n melt$ 9 a jam-pot plac$ 9 a saucepan ( wat] ov] a sl[ fire4 ,:5 ! /aff is siz$ & dry1 if ord9>y pap]s be us$1 x has to be divid$ c>efully into foot l5g?s1 :i* are m>k$ ) a set squ>e 9 p5cil across ! face ( ! /aff4 ,! foot l5g?s may be set (f accurately f an eng9e-divid$ *a9 scale1 or by beam compasses4 ,! pap]s1 :i* are pr9t$ %ort1 are !n pa/$ ov]1 pref]ably ) pa/e made ( />* ) boil+ wat]1 b n aft]w>ds boil$4 ,z ! l5g?s ( pap] are pa/$ !y are laid aside1 pa/$ side ^u pa/$ side1 to ?or\ghly absorb ! pa/e = a few m9utes1 ! "t v>y+ accord+ to ! increas$ l5g? requir$ above t ( ! orig9al pr9t$ pap]4 ,:ile /ill wet1 ! upp] pap] ( ! two is lift$ up & cut ) scissors1 at ! same "t fitt+ to ! b\nd>y l9es4 ,?is wet cutt+ ensures ! pa/e be+ equally di/ribut$ q up to ! edges4 ,! foot l5g? ( pa/$ pap] is !n laid by sett+ ! upp] edge exact to ! upp] foot l9e1 & gradually br++ ! pap] d[n f ?is by dabb+ ) a clean clo? or /raight hat-bru%4 ,if ! pap] does n rea* ! foot m>k :5 laid1 x is aga9 lift$1 & a little m pressure us$ 9 lay+ x ! second "t1 :i* w l5g!n x out z requir$4 ,o!r l5g?s are laid 9 ! same mann]4 ,! skill$ workman requires no lap to ! jo9s ( ! pap]s1 b br+s !m up edge to edge2 ) ! amateur a lap ( #a_/h in* is advisable4 ,to avoid ! tr\ble ( m>k+ (f & /ret*+ ea* foot1 ! au?or has introduc$ jo9tless levell+ /aff pap]s1 s t ! entire l5g? ( ea* section may be put on 9 "o piece4 ,^! are ( special pap]1 & x is only necess>y to pa/e ! face ( ! /aff well & smoo?ly1 & lay ! pap] unpa/$ d[n 9 position ^u x4 ,aft] ! pap]s are ?or\ghly dry !y require two coats ( ?9 is+lass size1 & !n a coat or two ( v>ni%4 ,pap] v>ni% c be b\ght2 b 9 defect a v>ni% may be made ( ,canada balsam dissolv$ 9 oil ( turp5t9e4 ,?is %\ld be laid on ) a flat bri/le bru% 7v>ni% bru%71 & set 9 a w>m room to dry = a day or two4 #bgf4--,pres]vation ( ! ,levell+ ,/aff 9 ,use4--,:]e two /aves are us$ !y may be plac$ face to face = c>ry+1 & be /rapp$ toge!r1 & w take little h>m ) mod]ate c>e4 ,:]e "o only is us$ x is g5]ally /rapp$ to ! tripod4 ,a /rip ( wood is sometimes us$ to protect ! face ( ! /aff4 ,illu/ration3 ,fig4 #ajf4--,pad = hold+ a /aff & tripod4 #bgg4--;,= c>ry+ ! /aff ) ! tripod1 a conv5i5t plan is to h two pads =m$ ( /\t ox-hide butt1 ea* pi]c$ ) two slots ne> _! ends at ! exact di/ance ap>t ( ! wid? ( ! /aff1 ,fig4 #ajf4 ,! /rap ( calf lea!r is pass$ f "o slot r\nd ! /aff into ! o!r slot1 & !n pass$ r\nd ! tripod & pull$ up tightly & buckl$4 ,! pad ( c\rse protects ! front ( ! /aff f graz+ by ! friction ( ! tripod aga9/ x4 ,!re is a c]ta9 am\nt ( risk1 "u any circum/ances1 ( ! cyl9drical tripod press+ aga9/ ! front ( ! /aff & splitt+ x4 ,to avoid ?is ! au?or has lately made ! pads ) a mahogany bridge piece1 s t ! pressure is di/ribut$1 com+ ^u ! edges ( ! front :]e ! /aff is /ronge/ to resi/ x4 ,?is is %[n1 ,fig4 #ajg4 #bgh4--;,= ! entire protection ( ! /aff a lea!r-b\nd sailclo? case is v g5]ally us$4 ,?is may be divid$ into two comp>tm5ts = ! /aff & ! tripod1 ) pads betwe54 ,! :ole case has a neat appe>ance1 & =ms a protection f slight bruises & dirt1 ei!r 9 travell+ or :5 set up 9 an (fice corn] = future use4 ,illu/ration3 ,fig4 #ajg4--;,improv$ pad = /aff & tripod4 #bgi--,repair+ ,figures & ,divisions4--,surveyors go+ abroad w f9d x v conv5i5t to h a few tubes ( arti/'s oil col\rs--:ite1 black1 & v]milion1 ) "o or two sable bru%es to t\* up any divisions or figures ^u ! /aves t h become accid5tally injur$ or worn (f by friction4 ,a tube ( m$ium is also useful1 :i* w cause ! col\r to dry quickly & leave x bright4 ,! tubes ( col\r w keep any numb] ( ye>s if ! caps are c>efully replac$4 ,! bru%es aft] use %\ld be well wa%$ ) soap & hot wat]1 rubb+ ! soap 9 q ?ickly till !y are q clean1 & !n well r9s$ be=e putt+ !m by4 ,illu/ration3 ,fig4 #ajh4--;,iron triangle to support a /aff4 #bhj4--;,iron ,triangle4--,= use ( ! /aff 9 ! field1 p>ticul>ly 9 op5 grass or moi/ l&s1 a triangul> plate ( iron1 z repres5t$ ,fig4 #ajh1 is v useful4 ,?is is trodd5 d[n firmly by ! /aff hold] be=e he places ! /aff ^u x4 ,9 use x gives a c]ta9 base to turn ! /aff ^u f =e to back sight4 ,x is v inexp5sive4 #bha4--,/aff ,level4--,?is is a small circul> level1 %[n at ,fig4 #aji1 ! upp] surface ( :i* is =m$ ( a glass work$ slightly concave & fix$ into a %ort cyl9drical box4 ,! glass is h]metically seal$ aft] be+ ne>ly fill$ ) _s4 ,! circul> level is m\nt$ on a plate ) a dovetail fitt+ :i* fits 9 a slot 9 ! hold+ plate atta*$ to ! back ( ! /aff4 ,9 use ! /aff hold] has to obs]ve :5 ! bubble "u ! concave glass is 9 its c5tre4 ,a v little practice is requir$ to hold ! /aff v]tically by means ( ?is little contrivance1 :i* only weighs1 ab\t #b oz4 ,illu/ration3 ,fig4 #aji4--,/aff level1 scale4 ,illu/ration3 ,fig4 #aaj4--,/aff-hold]1 #a_/aj scale4 #bhb4--,/aff-hold]4--,?is implem5t1 %[n ,fig4 #aaj1 /rid+ a /aff1 is v g5]ally us$ 9 ,g]many & o!r p>ts ( ! ,cont95t4 ,! /aff is sunk into "o side ( a h>dwood block4 ,! block is turn$ at "o end to =m a h&le4 ,a second simil> h&le is cut ) a /rong screw & screw$ into ! end ( ! block4 ,?is screw h&le by turn+ br+s up a foll[+ piece1 %[n inside next ! /aff1 :i* is cov]$ ) lea!r4 ,:5 x is screw$ up1 ! /aff may be held firmly by ! h&les only1 )\t ! risk ( ! f+]s com+ 9 front4 ,) ?is accessory x is also held m easily & truly v]tical4 ,x is a com=t 9 use 9 cold wea!r4 #bhc4--,practice ( ,levell+ ) ! ,/aff4--,?is subject c be foll[$ "h only s f> z to exemplify ! uses ( ! in/rum5ts & ( accessories connect$ ) su* in/rum5ts4 ,= practical levell+ we h ! /&>d orig9al works ( ,simms1 ,a9sley1 & o!rs1 ) _m mod]n works4#aj #bhd4--;,= ,hold+ ! ,/aff1 ,mr4 ,holl[ay1 9 ! "w ref]r$ to 9 ! la/ note1 gives in/ructions 9 su* concise =m t !y may be quot$ ) advantage4 ,he says3--,i g5]ally ent] into confid5tial *at ) my /aff hold]1 9 :i* ,i expla9 to him ! va/ importance ( 8 duties1 i4e41 ,i endeav\r to make him a man ( importance 9 8 way1 & ,i nev] fail to get ^? duties prop]ly p]=m$4 ,my in/ructions to him are sev5 9 numb]3-- #a4 ,draw out ! slides ( ! /aff1 & be sure ! jo9ts are prop]ly lock$4 ,draw out "o l5g? only unless signall$ to d o!rwise4 #b4 ,:5 ! /aff is once on a po9t nev] move x unless signall$ to d s4 #c4 ,exam9e ! /aff regul>ly be=e sett+ x d[n to see t no dirt is /ick+ to ! bottom ( x4 #d4 ,always /& erect beh9d ! /aff1 s t ! figures face ! level4 #e4 ,d n let any "p ( ! h& come be=e ! face ( ! /aff4 #f4 ,9 no case put a d[nw>d pressure on ! /aff4 #g4 ,if ! grass be long1 mossy1 or spongy1 tread x d[n1 s t ! /aff %all h a firm foot+--select a firm spot if ! selection is left to y\rself4#aa #bhe4--,! mann] ( sett+ up a level has be5 already describ$ 9 ! previ\s *apt]4 ,! levell] g5]ally foll[s a def9ite track :i* he has previ\sly arrang$ & m>k$ out on a map4 ,! di/ances ap>t = plac+ ! /aves or /aff are measur$ by ! *a91 or by ! subt5se sy/em to be fully describ$ h]eaft]4 ,:]e ! levell+ is v important1 z = canal "w1 topographical survey1 etc41 wood5 pegs are driv5 d[n at ! measur$ /ations :]e ! /aff is to be plac$ f :i* ! levels are to be tak54 ,a g5]al rule foll[$1 z f> z practicable1 = />t+ is to select an easily recognis$1 p]man5t1 solid /ation = fir/ plac+ ( ! /aff--a mile-/one1 l>ge b\ld]1 or o!r solid object answ]s3 a datum l9e is g5]ally assum$ to be at a c]ta9 dep? bel[ ?is1 to :i* all levels are ref]r$4 ,f ?is /ation1 if ! gr\nd be fairly level1 #e *a9s is ! ord9>y advanc$ position :]e ! level is set up & ! fir/ /aff read+ tak54 ,! level is set up at ! measur$ di/ance f ! /aff1 :i* is indicat$ by a m>k left by ! *a9man4 ,illu/ration3 ,fig4 #aaa4--,level height tape4 #bhf4--,occasionally 9 t[n surveys ! height ( ! level has to be tak54 ,= ?is a small /eel spr+ pocket tape is us$ to take ! height ( ! axis ( ! telescope1 ,fig4 #aaa4 ,! tape may be adju/$ by tak+ a piece (f ! fir/ end1 & all[+ = ! wid? ( ! tape case1 s t by plac+ ! r+ ( ! tape ^u ! hook "u ! in/rum5t & br++ ! case j to ! gr\nd1 ! height ( ! axis ( ! telescope above ! gr\nd may be read (f at ! po9t :]e ! tape leaves its case4 #bhg4--,! ,read+ ( ! ,/aff4--,! fir/ position1 :i* is aft]w>ds t]m$ ! back read+1 is tak5 at a di/ance beh9d ! fir/ =w>d position ( ! level4 ,?is is record$ exactly z x appe>s 9 ! telescope1 ! height ( ! telescope be+ also not$ 9 ! levell+ book1 to be describ$4 ,?us 9 ,fig4 #aab1 ,s ! fir/ /aff2 ,l ! fir/ /ation = tak+ levels4 ,! =e read+ ,l to ,s reads to a high] "p ( ! /aff ,s2 ,l next level /ation back sight4 ,l,s reads high on ! /aff ,s2 =e sight ,l,s reads l[2 back sight ,l,s aga9 l[1 foll[+ ! cont\r2 =e sight ,l,s l[2 ?us giv+ data 9 ! levell+ book f :i* ! cont\r c be plott$ f ! datum l9e1 :i* is tak5 l[ to make all read+s plus4 ,illu/ration3 ,fig4 #aab4--,practice ( levell+4 #bhh4--,! /aff read+1 z already describ$1 is divid$ into feet1 ) two places ( decimals4 ,! safe/ me?od ( tak+ ?is read+ is to take ! second decimal place fir/ & !n record x1 !n ! fir/ decimal1 & f9ally ! foot4 ,9 ?is mann] no ef=t ( memory is requir$1 & ! /aff be+ sight$ ?ree times assures ! c]ta9ty ( ! read+4 ,! telescope %\ld n be t\*$ dur+ ! op]ation1 s t ! read+ 9 ?is mann] is only a cauti\s transf]4 #bhi4--;,if two /aves are us$ on fairly level gr\nd1 ! second /aff is n[ advanc$ #e *a9s f ! level to a measur$ /ation1 ! /aff hold] "h sight+ ! l9e ?r\gh ! level to ! back /aff1 & firmly tread+ d[n ! /aff plate if ! l& is s(t or grass1 or o!rwise requires x1 or an iron triangle is us$4 ,:5 "t is giv5 to hold ! /aff v]tically by means ( ! /aff level1 ! read+ is tak5 9 ?is position by ! levell] z be=e1 & ?is is record$ 9 ! levell+ book4 ,! level is n[ mov$ =w>d #aj *a9s1 t is1 #e *a9s ahead ( ! =w>d /aff4 ,! /aff is c>efully turn$ half r\nd )\t pressure ^u its /&+ place or plate to face ! level z n[ plac$1 9 :i* position x is !n read (f by ! level z ! back sight1 ! back /aff n[ be+ mov$ #e *a9s =w>d ( ! level1 & s on alt]nately /aff & level until ! di/ance requir$ to be levell$ is complet$1 if !re is no ob/ruction :i* causes ano!r me?od ( proc$ure to be adopt$4 ,a simil> plan is pursu$ ) a s+le /aff2 b c>e has to be tak5 9 secur+ ! "r l9e ( m>*1 :i* w be by plac+ ! /aff 9 a sight l9e ?r\gh ! level ) a fix$ l&m>k in/ead ( ! back /aff m5tion$4 #bij4--,! equal back & =e sights z f> z practicable are insi/$ ^u by all levell]s1 z by ?is means any inaccuracy 9 ! level1 if ! run ( ! bubble is kept con/antly true1 is !reby comp5sat$2 b x is n always conv5i5t1 & :5 x is n ! accuracy ( ! "w mu/ dep5d l>gely ^u ! qualities ( ! level4 ,x is n necess>y or conv5i5t at all times to take ! back & =e sight 9 a l9e--ob/ructions ( woods1 riv]s1 etc41 may occur4 ,9 ^! cases v (t5 :at is q equival5t may be done by tak+ equal angul> back & =e sights f ! apex ( an equilat]al triangle ?us3--,say an ob/ruction occurs = ! *a9 by a pond or wood1 b t bo? po9ts to :i* ! levels are to be tak5 are visible at "s lat]al position4 ,levels may be tak5 f ?is place1 & if ! int]m$iate po9t ( di/ance is equal f bo? /ations !re w be no in/rum5tal error4 ,?us1 suppose ! direct level l9e ea/ 7#ij71 & t ! two /ations c be se5 & ! /aves read at #aej & #baj2 "h1 evid5tly1 ?is is equival5t to a direct back & =e sight1 ! "r angle to ! level c\rse be+ #ahj--! "o /ation is #aej #ahj - #cj1 & ! o!r #baj #ahj #cj4 ,if ^! equal angles c be ev5 approximat$ ) a fairly good level ! error w be small4 ,9 ?is mann] int]m$iate & ext5d$ po9ts may (t5 be conv5i5tly tak5 by previ\s arrangem5t ) a good /aff hold]4 ,x is 9 ?is angul> levell+ t ! greate/ use ( ! compass is f\nd to give ! angles1 to make entries ( ! "w 9 ! levell+ book4 #bia4--;,9 levell+ hilly gr\nd great loss ( "t w\ld sometimes be incurr$ f tak+ equal back & =e sights2 ! be/ plan 9 ?is case is to make z mu* use z possible ( ! l5g? ( ! /aff 9 use4 ,x is 9 hilly di/ricts only t a /aff long] ?an #ad feet is advantage\s4 ,) any /aff 9 desc5d+ a hill only #e feet ( ! /aff c be us$ = ! back sight1 t is1 a "p ( x equal to ! height ( ! level1 & sometimes #d feet or less if !re is grass1 brambles1 or o!r ob/ruction4 ,:]eas = ! =esight all ! /aff upw>ds ( ! height ( ! level1 t is1 ab\t #i feet 9 a #ad-;feet /aff1 c be us$ ) c]ta9ty4 ,! di/ance ( sett+ up ( ! levels & /aves mu/ 9 ?is case entirely dep5d ^u ! l5g? ( ! /aff & o!r conditions pres5t4 #bib4--;,= ne> read+ ( ! /aff on %>p incl9es1 read+ to two places ( decimals is n ne> en\gh1 z errors may accumulate rapidly4 ,x is 9 su* cases t a fully divid$ /aff is be/4 ,! divisions ^u a ne> /aff appe> 9 ! telescope mu* magnifi$2 & ?ree places ( decimals may easily be tak5 by anyone us$ to read+ a *a9 scale1 p>ticul>ly if a po9t diaphragm be us$4 ,?r\gh valleys ! level may be (t5 *eck$ at "s po9t f hill to hill by a back sight3 ! cont\r mu/ nev]!less be foll[$ = ! section4 ,x is 9 ^! %ort] unequal ranges & 9 di/ant sights t accuracy 9 ! level is dem&$2 & x becomes int]e/+ to "k h[ ne>ly ?is may be dep5d$ ^u = su* read+s4 #bic4--;,z already m5tion$1 a s5sitive #ad-;in* level ( ,y con/ruction1 or a dumpy 9 p]fect adju/m5t support$ on ! tribra* sy/em1 w "w ) a level tube divid$ to read #e seconds 9 divisions #a_/bj in* ap>t4 ,!re w be a little p]sonal error 9 read+ ! bubble f diff]5ce ( reflection1 accord+ to ! direction ( ! light f ! two ends ( ! bubble1 z be=e discuss$2 b ! bubble may be assum$ to be read )9 less ?an half a division1 t is1 )9 #b seconds--say #b seconds4 ,a di/9ct /aff may be read ) a good glass )9 #a foot at "o mile4 ,a second ( arc subt5ds #jbeeih ( a foot approximately #c in* at a mile di/ance4 ,!re=e a back read+ at ?is di/ance c be tak5 )9 an in* or s ( all[ance = in/rum5tal errors4 ,a read+ tak5 9 ?is way at a mile di/ance w\ld require a plus all[ance = curvature ( ! e>? ( #h in*es1 m9us say #a in* = refraction #g in*es4 ,f ^! data we c get a fair *eck level = hilly gr\nd1 possibly m accurate ?an by cont\r levell+ = a di/ant /ation1 ev5 if we all[ d\ble ! probable error1 say #a foot = error ( read+ ! /aff at a mile di/ance4 ,illu/ration3 ,fig4 #aac4--;,cald] /ove us$ z a lamp4 #bid4--,lamp4--,at heights betwe5 hills 9 wide valleys *eck levels may be tak5 f five to t5 miles v well ) a good #ad-;in* level 9 /ill cle> wea!r 9 d>k nights by ! use ( an oil lamp4 ,co9cid5t po9ts above datum be+ select$1 ! lamp is set ^u ! gr\nd1 or at a measur$ height at a calculat$ po9t1 or rais$ or l[]$ to lant]n signals1 all[ance be+ made = curvature & refraction4 ,! wide b& ( light is read v easily by %ift+ ! obs]v]'s position & rais+ or l[]+ 8 tripod4 ,! ,cald] lamp /ove answ]s v well z a lamp4 ,x has a wick ab\t #c in*es wide1 & by means ( a mask$ *imney may be made to pres5t a cle> :ite l9e ( light ( #a in* 9 dep?1 ,fig4 #aac4 ,! helio/at is sometimes us$ = *eck levell+ 9 sunlight4 ,?is w be describ$ fur!r on ) ! !odolite4 #bie4--;,curvature ,corrections ( ! e>? & ( ,refraction to be made use ( occasionally = *eck levell+4 ,! rule = f9d+ curvature is ,t ! diff]5ce betwe5 true & app>5t level is equal to ! squ>e ( ! di/ance betwe5 two places or /ations 9 miles--divid$ by ! e>?'s mean diamet]1 #giaf miles2 consequ5tly1 by ?is rule ! correction is always proportional to ! squ>es ( ! di/ances4 ,by proportion+ ! excesses ( height to ! squ>es ( ! di/ances1 we may obta9 a curvature table = corrections4 ,?is is1 h[ev]1 always 9 excess ( ! true curvature by ! refraction caus$ by ! increase ( d5sity ( ! air t[>ds ! e>?'s surface1 :i* b5ds ! visual ray4 ,! curvature ( ! e>? may be correct$ = refraction "o-fif? to "o-six?1#ab :i* v>ies accord+ to ! atmosph]ic pressure4 #bif4--,! foll[+ table1 :i* takes curvature m9us refraction1 w be f\nd useful to h at h&3 x may be writt5 out & pa/$ inside ! lid ( ! level case3-- ,table ( ,diff]5ces ( ,app>5t & ,true ,level = ,di/ances 9 ,*a9s4 ,di/ances 9 ,curvature m9us ,di/ances 9 ,curvature m9us ,*a9s4 ,refraction 9 ,*a9s4 ,refraction 9 ,dec4 ,ft4 ,dec4 ,ft4 #a #jjjjhi #ad #jage #b #jjjceh #ag #jbeh #c #jjjhjd #bj #jceg #d #jjadce #bb #je #e #jjbbcc #bd #jf #f #jjcbaf #bf #jg #g #jjdcg #bh #jh #h #jjeg #cj #ji #i #jjgb #dj #ad #aj #jhi #fj #ca #aa #jaa #hj #ef ,:]e great precision 9 levell+ is requir$1 z = important trigonometrical surveys1 _m precautions are requir$ to be tak5 :i* w\ld be q sup]flu\s1 = in/ance1 9 railway "w4 ,?us mu* great] exactness & fre$om f p]sonal error is secur$ by hav+ two levell]s to g ov] ! same gr\nd simultane\sly4 ,errors by two p]sons 9 ! same "p ( ! track are v unlikely to occur1 & by comp>+ books e "p may be *eck$4 #big4--,pegs4--,:]e ! "w is to be entirely pegg$ = *a9 measurem5ts1 ! pegs may be made ( natural /icks sawn (f & po9t$ up ) a bill hook4 ,if !y are sawn f timb] !y are g5]ally made ab\t #i in*es long & sawn to a po9t1 ! head be+ full #b in*es by #b in*es4 ,:]e great precision is requir$ a ca/-brass or iron nail is driv5 into ! head aft] ! peg itself is driv5 d[n4 ,?is is us$ to turn ! /aff ^u1 ,fig4 #aad4 ,a ! peg %[n ) a nail 9 its head1 #a_/h size4 ,b nail ab\t full size4 ,illu/ration3 ,fig4 #aad4--;,a1 /aff pegs ( sawn timb]1 #a_/h scale2 ,b1 nail1 full size4 #bih4--;,x is consid]$ a precaution ) an ord9>y level to m>k "o leg ( ! tripod & always place ?is 9 ! same position to ! /aff4 ,?us1 if ! m>k$ leg is plac$ to ! =w>d /aff at fir/1 x is put at ! next /ation backw>d to ! back /aff4 ,?is corrects any g5]al error f defective "w 9 ! in/rum5t & want ( adju/m5t2 & if ! /aves are plac$ at equal /ations any in/rum5tal defect :atev]1 to act cumulatively ^u a di/ant /ation1 is !n prev5t$1 z ?is pr9ciple produces an alt]nate plus & m9us error4 #bii4--;,diff]5ces ( true level h be5 f\nd betwe5 work+ s\?w>d t[>ds ! sun f work+ nor?w>d f x1 :i* are caus$ by ! expansion ( ! in/rum5t & bubble tube ^u ! side heat$ by 8 rays4 ,^! matt]s ( high] ref9em5t may be foll[$ 9 "s ( our be/ works on levell+4 ,mo/ excell5t in/ructions 9 ?is matt] w be f\nd 9 ! app5dix ( ,a ,manual ( ,survey+ = ,india1#ac 9 a pap] by ,colonel ,j4 ,t4 ,walk]1 ,r4,e41 ,f4,r4,s41 etc41 ( ! great ,trigonometrical ,survey ( ,india1 :]e9 levels h be5 c>ri$ across f ocean to ocean = ov] #aejj miles ( l& surface4 #cjj4--,levell+ ,books :i* record ! levels z !y are tak5 are consid]ably v>i$ 9 =m1 mu* influ5c$1 no d\bt1 by ! me?od pursu$ by ! civil eng9e] = ! execution ( 8 "w4 ,! illu/ration1 ,fig4 #aae1 %[s ! mo/ g5]al =ms1 b !re are _m o!rs4 #cja4--;,entries are v g5]ally made 9 levell+ books 9 black lead4 ,fab]'s arti/s' p5cils1 :i* require no cutt+1 are v g5]ally us$1 ,no4 #b be+ black & mod]ately h>d4 ,x is v conv5i5t to c>ry a small file = %>p5+ ! lead frequ5tly4 ,9 ! au?or's surveyor's knife1 describ$ fur!r on1 a file =ms "o ( ! blades4 #cjb4--,:]e x is desirable to make ! orig9al levell+ book read+s p]man5t = ref]5ce or o!rwise1 !y are v commonly writt5 9 ink1 ,morrell's regi/ration ink be+ v g5]ally us$1 or ! au?or's draw+ ink answ]s2 ?is be+ p]man5t is n liable to corrode ! p51 nor p]mit ! writ+ to be effac$ 9 any degree by moi/ure4 ,illu/ration3 ,fig4 #aae4--,specim5s ( levell+ books1 #a_/c scale4 ,ord9>y ,level ,book ) columns = ,no41 ,back ,sight1 ,int]m$iate1 ,rise1 ,fall1 ,r$uc$ ,level1 ,di/ance1 ,rem>ks4 ,collimation ,level ,book1 ) columns = ,back ,sight1 ,int]m$iate1 ,=e ,sight1 ,height ( ,collimation1 ,r$uc$ ,level1 ,di/ance1 ,rem>ks4 ,railway ,eng9e]s' ,level ,book1 rul$ = ,back1 ,int]m$iate1 ,=e ,sight1 ,rise1 ,fall1 ,di/ance1 ,r$uc$ ,level1 ,=mation ,levels1 ,cutt+1 ,embankm5t1 ,rem>ks4 ,ta*eomet] ,survey ,book1 rul$ z above illu/ration4 ,trav]se ,survey ,book1 rul$ z above illu/ration4 #cjc4--,! ,ink ,bottle mo/ly us$ is t kn[n z ! excise bottle4 ,?is is ( a smoo?1 oval =m1 cov]$ ) black lea!r1 ) a tab & buttonhole to hang ^u a button ( ! coat1 ,fig4 #aaf4 ,"o ( ! num]\s f\nta9 p5s is n[ g5]ally us$ in/ead ( ! bottle describ$4 ,illu/ration3 ,fig4 #aaf4--;,excise ink bottle4 ,,footnotes3 #g ,brit4 ,assoc4 ,report1 #ahch1 p4 #aed4 #h ,pat5t ,no4 #abeij1 #ahhi4 #i ,colli]y ,gu>dian1 vol4 xxxviii4 p4 #egf1 #ahgi4 #aj ,a ,treatise ( ! ,pr9ciples & ,practice ( ,levell+1 by ,f4 ,w4 ,simms1 #ahdb2 ,a ,treatise on ,l& ,survey+1 by ,john ,a9sley1 revis$ by ,william ,galbrai?1 #ahdi4 ,q mod]n works--,aid to ,survey ,practice1 ,l4 ,d',a4 ,jackson1 ,crosby ,lockwood1 #aiaj2 ,on ,levell+ & its ,g5]al ,application1 by ,?omas ,holl[ay1 ,spon1 #ahhg2 revis$ #aiad4 #aa ,levell+1 p4 #di4 #ab ,des*anel's ,natural ,philosophy1 by ,pr(4 ,ev]ett1 p4 #ajah1 #ahgf4 #ac ,a ,manual ( ,survey+ = ,india1 by ,colonel ,h4 ,l4 ,?uilli]1 ,c4,s4,i41 ,f4,r4,s41 etc41 & ,lieut5ant-,colonel ,r4 ,smi?4 ,?ack]1 ,calcutta1 #ahge4 7,n[ out ( pr9t74 ,,*apt] ,,vi4 ,,division ,,( ,,! ,,circle ,,& ,,me?ods ,,employ$ ,,9 ,,tak+ ,,angles--,,divid+ ,,eng9e--,,surfaces ,,= ,,graduation--,,v]ni]--,,v>i\s ,,sections--,,read+ ,,microscopes--,,%ades--,,micromet]s--,, clamp ,,& ,,tang5t ,,motions--,,( ,,limbs--,,( ,,axes--,,use ,,& ,,we>--,,diff]5ce ,,( ,,hypot5use ,,& ,,base4 #cjd4--;,division ( ! ,circle4--,sexagesimal ,division4--,all true survey+ in/rum5ts dep5d1 z _! special function1 ^u tak+ ! direction1 or angul> position1 ( surr\nd+ objects or def9ite p>ts ( ! surface ( ! e>? f positions :i* are at fir/ accurately measur$ or asc]ta9$4 ,! in/rum5ts requir$ = su* "w mu/ possess an accurately divid$ circle or arc1 ) means ( subdivid+ ! visible divisions ( ?is to great] clos5ess ?an any possible me?od ( draw+ l9es simply w\ld p]mit4 ,! l9es ^u ! circle 9 g5]al practice 9 ,great ,brita9 are divid$ into degrees1 :i* are subdivid$ to #cj1 #bj1 #aj1 or #e m9utes1 accord+ to ! size ( ! in/rum5t1 & arrang$ = fur!r subdivisions by means ( a v]ni] into m9utes or #cj1 #bj1 or #aj seconds ( arc4 ,^u l>ge circles1 say ( #aj & #ab in*es diamet]1 & ) mod]n #e1 #f1 & #h in* diamet]s1 angul> displacem5ts 9 ! direction ( ! telescope are ultimately read (f ) a microscope by means ( a screw ) divid$ head1 t]m$ a micromet]1 plac$ tang5tially to ! divid$ circle2 or by a s]ies ( l9es plac$ at equal di/ances ap>t 9 front ( an eye-piece or )9 a microscope2 b 9 ! ord9>y portable in/rum5ts1 or ^? t a surveyor c p]sonally c>ry ab\t ! c\ntry1 ! ultimate subdivisions ( ! circle are /ill g5]ally made by a v]ni] scale only1 :i* w pres5tly be describ$1 al?\gh ! small] mod]n micromet] read+ in/rum5ts are sl[ly b surely com+ into fav\r = all high class "w4 #cje4--;,c5tesimal ,division4--,t5 to fifte5 ye>s ago on ! ,cont95t g5]ally1 & 9 ,am]ica occasionally1 ! division ( ! circle into #djj-;grades & -grades1 & ! subdivision ( ^! decimally to c5tigrades1 appe>$ to be com+ m & m into use1 p>ticul>ly ) ! m ext5d$ use ( ! ta*eomet]4 ,"u ?is sy/em x w be se5 t ! "r angle subt5ds #ajj grades4 ,?is division1 ) its c5tesimal p>ts1 0 f\nd to bl5d conv5i5tly ) log>i?metical calculation & to p]mit ! free use ( ! slide rule ) great sav+ ( "t ov] ord9>y calculation1 b x is n[ v little us$4 ,! decimal division ( ! ord9>y degree ( #ij to ! quadrant greatly facilitates ! calculation comp>$ ) :at is necess>y ) ! sexagesimal division into m9utes & seconds1 & ! read+ ( ! v]ni]s is mu* simpl] & less liable to errors2 moreov]1 ! m5tal conv]sion ( ! sexagesimal division into decimals ( ! same degrees is mu* simpl] ?an ! conv]sion into ! c5tesimal degrees ( #ajj to ! quadrant4 #cjf4--;,divid+ ,eng9e4--,?is important tool is us$ = cutt+ ! graduations on all survey+ in/rum5ts4 ,if possible a position %\ld be secur$ = x on a gr\nd floor at a mile or m di/ance f any railway1 & at a good di/ance f roads ^u :i* !re is heavy traffic1 z small vibrations are suffici5t to cause unpleasant work+ & "s error 9 ! division ( l>ge in/rum5ts4 ,= v accurate "w "s mak]s divide at night = ! sake ( /illness4 ,! pr9ciples ( con/ruction ( ?is ma*9e1 z at pres5t 9 g5]al use1 7 inv5t$ by ,jesse ,ramsd51 ( :i* an acc\nt 0 pr9t$ by ! ,bo>d ( ,longitude 9 #aggg4 ,ref9em5ts ( detail h be5 add$ to ! inv5tion1 & ! /eady action ( /eam or electric p[] has be5 appli$ 9 place ( ! foot1 b o!rwise ! ma*9e rema9s practically ! same4 ,!re=e a brief description ( ?is ma*9e z orig9ally inv5t$ w be suffici5t = ! purposes ( ?is "w1 :i* is n int5d$ to fully describe ! tools us$ 9 ! manufacture ( in/rum5ts4 #cjg4--,ramsd5's ,eng9e consi/s ( a circul> brass surface plate1 made g5]ally ( #cf in*es diamet]4 ,?is plate is support$ f bel[ ^u a holl[ v]tical axis1 :i* moves 9 an adju/able coll> plac$ at its upp] end & 9 a conical po9t or pivot at its base4 ,! pivot re/s 9 a cup ( oil & supports ! weight ( ! plate & axis1 s t ?is "p rotates ) little friction4 ,! out] edge ( ! surface plate is cut ) #bafj tee? or ?reads1 into :i* an endless or tang5t screw works1 s t ! plate c be revolv$ any desir$ quantity by means ( ! screw4 ,six turns ( ! tang5t screw moves ! plate #a4 ,! head ( ! tang5t screw is divid$ z a micromet] into #fj p>ts2 !re=e ! movem5t ( "o ( ! divisions ( ?is head revolves ! plate #aj ( an arc4 ,a rat*et :eel ( #fj tee? is atta*$ to ! tang5t screw1 & s arrang$ t by reciprocat+ motion appli$ to a rack :i* works into x ! circle c be advanc$ any multiple ( #aj4 ,motion is giv5 to ! tang5t screw by a catgut ov] a pulley work$ by ! foot4 ,! "w is c5tr$ & clamp$ d[n ^u ! surface plate4 ,:ile ! divisions are be+ cut ?is surface plate rema9s = ! "t q /ation>y4 #cjh4--,! divid+ knife is atta*$ to a sw++ frame hav+ a reciprocat+ motion4 ,! =w>d ext5t ( its sw+ is regulat$ by a det5t :eel ) tee? ( v>i$ heights1 :i*1 z !y are br\ght by ! me*anism consecutively =w>d1 /op ! knife at a def9ite position2 s t ! cuts ^u ! circle--te*nically ! limb--are regulat$ = l5g?s to repres5t #aj degrees1 #e degrees1 degrees & p>ts4 ,9 ! use ( ?is divid+ ma*9e ! divid] :o work$ x _h alt]nately to press 8 foot ^u a treadle & !n pull a cord atta*$ to ! divid+ knife frame4 ,^! motions are n[ p]=m$ by self-act+ me*anism4 ,= full p>ticul>s & details ( ! divid+ eng9e see ,tr\ghton's ,memoir1 ,phil4 ,trans41 #ahji3 ,memoirs ( ! ,royal ,a/ronomical ,soc41 vol4 v4 p4 #cbe2 vol4 viii4 p4 #ada2 vol4 ix4 pp4 #ag & #ce4 ,= v>i\s plans t h be5 tri$ see ,holtzapffel's ,turn+ & ,me*anical ,manipulation1 pp4 #fea-iee4 #cji4--,! ,mat]ial ^u :i* ! limb or circle ( an in/rum5t is divid$ is almo/ uni=mly ( silv]1 except = m9+ survey in/rum5ts1 :i* ne$ a v /rong cut4 ,silv] be+ d5se & ( extremely f9e cry/allisation1 or gra91 z x is te*nically t]m$1 be>s a uni=m smoo? cut ) %>p outl9e4 ,occasionally circles or arcs are divid$ on plat9um1 c]ta9ly ! be/ metal1 z x keeps con/antly clean2 b x is exp5sive4 ,! v]ni]s are !n made ei!r ( ?is metal or ( gold4 ,! silv] ( ! circle1 :5 ?is metal is employ$1 is roll$ d[n f a surfac$ ca/ plate ( ab\t #be in* 9 ?ickness to ab\t #jde in*1 by means ( :i* x becomes uni=mly d5se & f9e gra9$4 ,9 all cases possible1 t is1 ^u all flat int]nal surfaces1 ! silv] is plac$ 9 an und]cut groove & plani%$ d[n to fill ! groove )\t any o!r fix+ be+ necess>y4 ,?is plan ( ins]tion is employ$ = all v]tical circles--! horizontal circle ( ,ev]e/'s !odolite1 limbs ( sextants1 box sextants1 etc4 ,9 ,fig4 #aag ! silv] is %[n at ,a1 9 ! section to :i* x is drawn by a plate aft] x is cut 9 slips4 ,x is %[n plac$ 9 its groove ,b ready = plani%+ d[n4 ,by ?is me?od c]ta9ty ( d5se surface is obta9$ = ! future division4 #caj4--,^u bevell$ edges & out] surfaces ! roll$ silv] is plani%$ to =m1 & !n sold]$ to ! metal ( ! "p ( ! in/rum5t to be divid$4 ,! surface1 aft] be+ made z d5se z possible by plani%+ or o!rwise is turn$ to =m & /on$ to surface ready = ! divid+ knife4 ,illu/ration3 ,fig4 #aag4--;,ins]tion ( silv] 9 circle4 #caa4--;,graduat+4--,! object aim$ at by ! skilful divid] is to obta9 z deep a %>p-edg$ cut z possible1 :i* %all be at ! same "t z f9e z x c be read cle>ly by ! microscope ) :i* x is to be us$4 ,?is matt] is mo/ important to ! possessor ( ! in/rum5t aft]w>ds = use1 z 9 ! atmosph]e ! silv] soon =ms an oxide & a sulphuret ^u its surface :i* has to be clean$ (f2 & at e clean+ a portion ( ! silv] is necess>ily remov$1 s t 9 old or badly divid$ in/rum5ts ! divisions become dull or lo/ f ?is reason4 ,illu/ration3 ,fig4 #aah4--,piece ( *>coal4 #cab4--;,aft] ! in/rum5t is divid$ x is engrav$ ) figures & /on$ (f ) f9e blue-/one1 & f9ally f9i%$ ) will[ or pe>wood *>coal1 :i* has j suffici5t cut 9 x to leave a h>d edge to ! division l9es4 #cac4--;,x may be useful to ! surveyor1 f> f aid ( ! optician1 to "k t divisions on silv] :i* are mu* oxidis$ may be br\ght up to %>p l9es by ! use ( a piece ( f9e-gra9$ *>coal1 %>p5$ by a clean file to a *isel po9t4 ,?is %\ld be frequ5tly dipp$ 9 wat]1 & rubb$ lightly ) ! flat ( its end surface1 ,fig4 #aah1 keep+ ! motion ( ! h& 9 ! direction ( ! circumf]5ce ( ! circle4 ,! piece ( *>coal be=e be+ us$ %\ld be fir/ tri$ ^u a piece ( pla91 smoo? metal--an old co9 :i* is worn smoo? w d--to see t x is n scrat*y4 ,no k9d ( poli%+ p[d] %\ld 9 any case be us$ = clean+ limbs or v]ni]s1 z ?is is sure to rub d[n ! edges ( ! cuts & !reby ru9 ! divisions ( ! in/rum5t4 #cad4--;,x mu/ be und]/ood t ! above directions are n int5d$ = ! ord9>y clean+ ( ! circle = an in/rum5t 9 g5]al use1 z su* w\ld be injuri\s to x4 ,9 ! ord9>y daily use ( ! circle1 if x is n 9 any case t\*$ by ! h&1 & is kept c>efully bru%$ ) a l>ge1 s(t camel-hair bru% :5 tak5 f ! case1 & ! same :5 return$ to x1 x w keep a long "t 9 an excell5t /ate4 ,if ! circle is slightly t>ni%$1 ?is t>ni% may be remov$ by a piece ( q clean wa% lea!r2 b ! bru% is always ! safe/ if suffici5t4 ,if ! v]ni] gets grubby aga9/ ! circle1 a piece ( clean ?9 writ+-pap] may be pass$ betwe5 ^! p>ts1 :i* w cle> out any dirt or grit !re may be betwe5 suffici5tly4 #cae4--,! ,v]ni] ,read+ ,index4--,?is is "o ( ! mo/ important inv5tions ev] appli$ to in/rum5ts ( precision = measur+ ^u ! circumf]5ce ( ! circle4 ,x 0 inv5t$ or br\ght into practical use by ,pi]re ,v]ni]1 a native ( ,ornans1 ne> ,besanon1 9 ,burgundy4 ,! fir/ publication ( ! inv5tion appe>s 9 a pamphlet publi%$ 9 ,brussels 9 #afca1 ,con/ruction1 ,usage1 et ,proprietes du ,quadrant ,n\veau de ,ma!matique4 ,?is inv5tion 0 possibly =e%ad[$1 z x is m5tion$ by ,cri/oph] ,clavius 9 8 ,op]a ,ma!matica1 #afab1 vol4 ii4 p4 #e1 & vol4 iii4 p4 #aj2 b he did n propose to atta* x p]man5tly to read into an arc1 t is1 to place x 9 its practical =m4 #caf4--,! value ( ! v]ni] z a means ( read+ small quantities dep5ds ^u ! fact t ! eye _c sep>ate l9es1 drawn at equal di/ance ap>t1 ( above a c]ta9 degree ( clos5ess1 !re be+ a po9t = all vision :]e su* l9es appe> to mix ) ! gr\nd ^u :i* !y are drawn & =m a t9t2 !re=e1 an index read+ into su* close l9es w\ld be1 unless "u extreme magnification1 mo/ indef9ite2 :]eas ! eye c see a s+le sep>ate l9e cle>ly & detect any break 9 x4 ,! v]ni] = read+ subdivisions dep5ds ^u ! functions ( ! eye hav+ p[] to detect any break 9 an o!rwise /raight l9e1 s t a l9e t appe>s )\t a break may be tak5 z ! index ( read+ f among o!rs t appe> brok5 or sep>at$4 ,x is f\nd 9 practice t a l9e z f9e z x c be cle>ly se5 w appe> brok5 9 its cont9uity ) ano!r equally f9e l9e1 if at ! meet+ ! rectil9e> displacem5t is z mu* z #be to #b "p ( ! wid? ( ! l9e4 ,x !re=e foll[s t we may read clos] by displacem5t ( p>ts ( a s+le l9e ?an by any possible s]ies ( l9es t c be drawn 9 spaces ap>t ^u a surface2 s t if we c arrange l9es 9 su* a mann] t !y op5 out or sep>ate into di/9ct l9es to admit ( ?is pr9ciple1 we obta9 ! full value ( ! unbrok5 s+le l9e read+1 & ?is is ! pr9cipal aim ( ! v]ni]4 #cag4--,on ! same pr9ciple t we c f9d ! /raight or mo/ direct l9e ( a s]ies ( l9es to take z our index1 we c also e/imate ! am\nt ( ! displacem5t ( our select$ l9e1 if ?is does n read p]fectly /raight f ! v]ni] division to ! circle division4 ,?is small diff]5ce is detect$ 9 practice by _m exp]i5c$ surveyors1 s t a v]ni] read+ nom9ally to m9utes only is record$ n #ae1 #cj or #de1 t is to #ae4 ,!re is no d\bt t ?is w be approximate1 b x may be mu* ne>] ?an ! ev5 m9utes1 say to ! #cj on a #e-;in*1 or ! #ae on a #f-;in* %>ply divid$ circle4 ,illu/ration3 ,fig4 #aai4--,orig9 ( v]ni] scale4 #cah4--,! ,v]ni] ,scale1 z employ$ by ,v]ni]1 0 divid$ to read m9utes ^u a circle or limb divid$ to half degrees1 by tak+ ?irty-"o divisions ( ! scale & divid+ ^! 9 ?irty equal p>ts = a sep>ate scale to read aga9/ x4 ,?is plan is n[ t]m$ an inv]se read+1 ! read+ be+ ! rev]se to ! direction ( t ( ! arc4 ,9 mod]n practice ! v]ni] to read m9utes is divid$ to ! l5g? ( #bi half degrees1 & ?is l5g? is subdivid$ into ?irty equal p>ts3 consequ5tly1 :]e ! v]ni] & scale are plac$ edge to edge or read+ to read+1 e division ( ! v]ni] advances consecutively on ! scale "o-?irtie? ( ! half degree1 t is #a ( arc on ! scale divid$ to half degrees4 ,9 ! above diagram1 ,fig4 #aai repres5ts ! scale & v]ni] at ! position f :i* ! description is tak51 :]e9 ! v]ni] is %[n to cov] #bi half degrees or #ad #cj1 & ?is l5g? is divid$ into ?irty p>ts4 ,! consecutive advance ( ! v]ni] on ! scale is %[n #a = ea* half degree4 ,9 ?is position ( ! v]ni]1 or at a simil> position 9 relation to any o!r half degree ( ! circle ! arr[ plac$ at ! z]o ( ! v]ni] reads direct into ! degree or half degree1 s t ?is read+ mu/ be n or n #cj at any equival5t position 9 relation to any l9e on ! limb4 ,illu/ration3 ,fig4 #abj4--,v]ni] scale1 read+ #bc #ab4 #cai4--;,9 ,fig4 #abj ! arr[ ^u ! v]ni] scale is %[n read+ at a position beyond #bc1 :i* we !n "k mu/ be #bc n4 ,n[1 if we look along ! v]ni]1 ! l9es ( ?is & ! scale appe> co9cid5t at ! twelf? division ( ! v]ni]2 consequ5tly1 ! n is #ab1 & ! read+ is altoge!r #bc #ab4 #cbj4--,le>n+ ! read+ ( ! v]ni] is v simil> to t ( ! clock1 :]e9 a *ild at fir/ gets confus$ by ! diff]5ce ( value ( ! m9ute h& & ! h\r h&4 ,9 ! case ( ! v]ni] we h only to get cle>ly 9 our m9ds t ! degree read+ & ! v]ni] read+ are q di/9ct processes1 9 :i* ! v]ni] reads m9utes only1 & ?is by co9cid5ce ( l9es only1 & t x has no?+ to d ) degrees1 :i* are indicat$ by ! arr[ only4 ,! arr[ may be assum$ to be plac$ on ! v]ni] scale to save an unnecess>y l9e ( division2 b ?is practically might j z well be plac$ q outside ( x1 z x has no?+ :atev] to d ) ! v]ni] read+4 ,illu/ration3 ,fig4 #aba4--,v]ni] scale1 read+1 #bc #dg4 #cba4--;,x is important to make ?is matt] ( read+ ! v]ni] cle>2 !re=e 9 ,fig4 #aba ! index arr[ & v]ni] are %[n read+ pa/ a half degree4 ,at ?is position ! arr[ reads #bccj on ! limb ! v]ni]1 or #bc #cj n ( ! v]ni] read+4 ,we f9d ! co9cid5t l9e ( ! v]ni] ) ! limb is at #ag1 !re=e ! read+ is #bc #cj #ag or #bc #dg4 #cbb4--,! pr9ciple ( ! v]ni]1 ^u :i* x takes its read+ f ! co9cid5ce ( l9es1 z j /at$1 po9ts out t ! figur+ ( values ( po9ts ( co9cid5ce may be v>i$ at discretion1 & ! z]o index may be 9 any conv5i5t position4 ,! above describ$ is ! common read+ to ! !odolite & _m o!r in/rum5ts4 ,9 m9+ dials & "s o!r in/rum5ts ! z]o is plac$ 9 ! c5tre4 ,we may1 = example1 take a c5tral read+ ) a v]ni] read+ to #c1 :]e9 ! circle be+ divid$ into degrees2 ! v]ni] is !n1 necess>ily1 9 ! direct me?od1 divid$ into tw5ty divisions 7#bj #c #fj7 :i* correspond ) n9ete5 degree m>ks ( ! circle4 ,) a c5tral read+ ! v]ni] 9 ?is case is figur$ #cj1 #de1 #j1 #ae1 #cj4 ,?is is r a simple read+1 z ! z]o to :i* an arr[ is atta*$ gives ! true be>+1 & x is readily se5 to :i* degree x ref]s4 ,illu/ration3 ,fig4 #abb4--,v]ni] read+ c5trally to #c4 ,illu/ration3 ,fig4 #abc4 ,9 ,fig4 #abb ! #de ( ! v]ni] is co9cid5t ) a l9e ( ! limb1 ?is mu/1 !re=e be #de2 & z ! index arr[ is pa/ #dd1 x is #dd #de4 ,if ! v]ni] _h read ! division next pa/ ! #de1 ! division be+ to #c1 ?is read+ w\ld h be5 #dd #de #c #dd #dh4 ,! same pr9ciples may be appli$ to any subdivision4 ,circles are commonly divid$ by ! v]ni] 9 v>i\s ways to give read+s f #e to #e4 ,!odolites read+ to #cj seconds are usually divid$ degrees & ?irds ( degrees on ! circle & m9utes & halves on ! v]ni]1 z illu/rat$ 7,fig4 #abc71 ! read+ 9 ?is case be+ #aec degrees #dj m9utes on ! circle & #h m9utes #cj seconds on ! v]ni]1 giv+ a total read+ ( #aec #dh #cj4 ,a #bj second read+ usually has divisions ( #bj m9utes on ! circles & ^! are subdivid$ into m9utes & ?irds by means ( ! v]ni]4 ,illu/ration3 ,fig4 #abd4 ,fig4 #abd is an illu/ration ( ?is1 %[+ a read+ ( #bh degrees #dj m9utes on ! circle & #ab m9utes #bj seconds on ! v]ni]1 giv+ a total ( #bh #eb #bj4 ,a #aj second read+ is design$ 9 ! same mann] z ! above1 b ea* division ( ! circle is #aj m9utes in/ead ( #bj m9utes1 ) m9utes & six?s on ! v]ni]4 ,fig4 #abe is an illu/ration ( ?is1 %[+ a read+ ( #g #af #cj4 ,illu/ration3 ,fig4 #abe4 #cbc4--;,= ,c5tesimal ,division ! v]ni] to read m9utes is g5]ally divid$ #ej into #di = ! half grades1 = small circles #d in*es to #e in*es4 ,= l>g] circles1 #f in*es to #h in*es1 v]ni]s are cut #be to #bd4 ,! circle is !n divid$ to #be4 ,:]e !re is space = five divisions to ! grade1 #bj1 ! ?ird decimal place1 may be e/imat$ or read exactly to #jje by a v]ni] #dj to #ci1 or m closely if desir$ by a micromet]1 to be describ$ pres5tly4 ,illu/ration3 ,figs4 #abf1 #abg4--,sections ( scales & v]ni] = circul> read+s4 ,illu/ration3 ,figs4 #abh1 #abi4--,sections ( scales & v]ni] = circul> read+s4 #cbd4--,surfaces ( ,limb & ,v]ni]4--,to get a p]fect read+ ( a v]ni] ! scale & v]ni] %\ld be br\ght into contact ^u a plane4 ,?is1 = _m reasons1 is impossible 9 a great numb] ( cases ^u an in/rum5t1 f ! conditions ( its con/ruction1 conv5i5ce ( vision1 & 9 "s cases = want ( means ( ensur+ durability ( ! edges :i* "w toge!r4 ,!re=e v]ni]s & scales are m commonly con/ruct$ ^u ! me?ods %[n 9 section ,figs4 #abf1 #abg1 :]e ,,vv are v]ni]s1 ,,ll limbs4 ,! plan %[n 9 section ,fig4 #abh gives a nice read+ on a new in/rum5t2 b ! "p ( ! edge n cov]$ by ! v]ni] is op5 to accid5t1 or if ne>ly cov]$ by a "p ( ! in/rum5t1 op5 to ! introduction ( gritty du/1 :i* we>s ! meet+ l9e op51 & !reby causes loss ( edge to edge read+4 ,fig4 #abi %[s a section we f9d on "s ,fr5* in/rum5ts4 ,?is plan 0 introduc$ by ! late ,colonel ,a4 ,/range = ! section ( ! limb read+ ( !odolites = ,india1 b x 0 f\nd 9 practice awkw>d to use ^u ?is in/rum5t1 z x requir$ unpleasant /oop+ to read x4 ,x is1 nev]!less1 "o ( ! be/ p]man5t v]ni] read+s1 z ! division rema9s con/ant "u ! am\nt ( we> occasion$ by ! slid+ ( ! v]ni] ^u its circle4 #cbe4--,) ! read+ planes %[n 9 section ,fig4 #abf we require great c>e to br+ ! eye1 :e!r op5 or ?r\gh ! microscope1 directly radial ) ! c5tre ( ! circle at ! l9e into :i* ! v]ni] cuts4 ,if we read ! l9e 9 ! slighte/ degree "o-sid$ x is q possible to make a diff]5ce ( a m9ute on a #e-;in* or #f-;in* circle4 ,?is is ! section ( ! g5]al read+ plane ( !odolites1 :]e1 f ! necess>y height ( ! telescope1 ! limb has to be plac$ mu* l[] ?an ! eye4 ,) ?is section ! circle comes fairly squ>e to a com=table position = read+4 ,x w be notic$ t !re is a slight lap %[n to ! v]ni] ov] ! limb at a1 ,fig4 #abf1 :i* is always f\nd 9 new in/rum5ts ( ?is section4 ,x gives an all[ance = we> betwe5 ! v]ni] & ! limb caus$ by ! frett+ ( ! metals toge!r1 z also by ! intrusion ( grit1 :i* is always pres5t 9 in/rum5ts us$ 9 ! op5 air4 ,! lap %\ld n be great1 & x %\ld be ne>ly equal along ! edge ( ! v]ni]1 al?\gh x is a difficult matt] = ! mak] to get x p]fectly s4 ,fig4 #abg is a section ( ! read+ planes common to sextants & p>ts ( _m in/rum5ts4 ,?is plan requires ! same c>e to obta9 a truly p]p5dicul> read+ to ! division z t describ$ above = ,fig4 #abf4 #cbf4--;,9 ! v be/ ( "w !re is at all times a c]ta9 am\nt ( error1 bo? betwe5 ! divisions !mselves1 & 9 ! place ( ! axis 9 relation to ! c5tre ( ! divid$ circle1 & ( ! position ( ! v]ni] 9 relation to bo? ^!4 ,x !re=e becomes necess>y1 :]e exactness is requir$1 to place at lea/ two v]ni]s to read opposite sides ( ! circle4 ,^! bisect e read+ ?r\gh ! axis ( ! in/rum5t1 & detect v small errors 9 ! "w1 z well z p]sonal errors ( ! obs]v]1 ( :i* ! mean read+ ( ! m9utes or seconds only may be tak5 & us$ = correction to mean position4 ,:]e v great precision is aim$ at1 ?ree or ev5 five v]ni]s are sometimes plac$ r\nd ! circle1 & ! mean read+ is tak5 ( ! small diff]5ces 9 m9utes or seconds1 aft] calculation = correction1 to f9d ! direct position ( ! axis ( ! telescope requir$ = ! record ( ! obs]vation4 #cbg4--,read+ ,microscope4--,! microscope usual = read+ ! v]ni] is ei!r a simple plano-convex l5s ( %ort focus or a ,ramsd5 eye-piece ( ! k9d describ$ = obs]v+ l9es on ! diaphragm ( a telescope1 art4 #hb4 ,frequ5tly ! microscope1 te*nically call$ ! read]1 is made ( a comp\nd =m1 sometimes ) a diagonal prism or mirror4 ,x is uni=mly m\nt$ 9 su* a mann] t x may move conc5trically to ! divid$ circle into :i* x reads4 ,9 ,engli% in/rum5ts x is plac$ normal to ! surface ( ! v]ni]1 s t foll[+ its curvature x may read opposite any l9e ^u x4 ,9 ,fr5* in/rum5ts ! read] is frequ5tly plac$ obliquely1 s z to look along ! l9e ( ! limb into t ( ! v]ni]1 :i* is said to be advantage\s 9 c]ta9 lights4 #cbh4--;,9 !odolites = read+ ! horizontal circle1 ! read] is sometimes m\nt$ to slide 9 an und]cut groove ne> ! circumf]5ce ( ! limb to foll[ its curvature4 ,?is motion is n pleasant2 x is bett] 9 ?is & all cases ( v]ni] read+1 if possible1 to m\nt ! read] on frame-"w proce$+ directly f & mov+ ^u ! axis4 ,:]e x is practicable1 x is mu* bett] to h two read]s :]e !re are two v]ni]s1 & 9 all cases to h "o to ea* v]ni]1 ?an to %ift "o read] ab\t aft] ! in/rum5t is plac$ 9 position1 :i* is liable to di/urb x4 ,) opposite read]s m\nt$ on a pair ( arms =m$ ( "o piece ( metal1 :]e ^! bisect ! circle work+ ?r\gh its axis1 by ! sett+ ( "o read] truly normal to ! co9cid5t division ( ! v]ni] ! opposite read] w be set also2 s t ?is does n only save "t1 b ! in/rum5t ne$ n be t\*$ = read+ ! second v]ni]4 ,! same pr9ciple %\ld be appli$ to any great] numb] ?an two v]ni]s z ne>ly z x may be practical4 #cbi4--;,in/rum5ts t h to be pack$ 9 cases = conveyance %\ld always h read]s removable f ! in/rum5t1 ) prop] fitt+s 9 ! case provid$ = !m1 or !y %\ld be h+$ to turn up to a secure position1 ! latt] be+ a m exp5sive b a mu* bett] way4 ,x is bett] also1 if possible1 to remove ! light frame ) ! read] if ?is does n turn up1 s t x _c be injur$ 9 replac+ ! in/rum5t 9 its case4 ,illu/ration3 ,fig4 #acj4--,read] fix$ normal to surface4 ,illu/ration3 ,fig4 #aca4--;,jo9t$ read] to set to any angle4 #ccj4--;,fig4 #acj %[s a good rigid =m ( read] = an oblique plane ( division3--,v v]ni]1 ,l limb4 ,?is read] is plac$ on an arm radial f ! c5tre ( ! in/rum5t1 m g5]ally 9 pair ) an opposite read]4 ,! connection ) ! arm is commonly made = portability ) a dovetail slide fitt+ to ! read]1 sprung by a saw-cut d[n x to ensure con/ant contact aft] we>1 z %[n 9 section ,fig4 #acb2 ,n arm ( read]1 ,o fitt+ to arm4 ,! bett] =m is %[n 9 ,fig4 #aca4 ,9 ?is ! arm is jo9t$1 s t ! read] out ( use is turn$ up into ! c5tral "p ( ! in/rum5t4 ,?is plan admits ( adju/m5t ( ! read] = reflection ( light f ! division1 or = read+ d[n ! l9es if pref]r$4 ,! magnify+ p[] ( ei!r ( ^! microscopes is g5]ally two to ?ree diamet]s4 ,! adju/m5t ( ! glasses %\ld be su* z w produce a flat field 7,ramsd5's pr9ciple1 p4 #da71 s t sev]al divisions ( ! v]ni] & limb may be read %>ply :5 x is 9 focus1 al?\gh ! c5tral division only is tak5 = ! read+4 ,illu/ration3 ,fig4 #acb4--,section ( movable arm fitt+ to read]4 #cca4--,surface ,reflection to ,read]4--,9 read+ ) ! microscope ! silv] surface1 f its brightness 9 c]ta9 lights1 gives unpleasant reflections :i* r5d] ! read+ difficult4 ,9 practice ! h& or a piece ( :ite pap] is us$ to %ade ! op5 v]ni] 9 su* cases4 ,9 l>ge in/rum5ts a piece ( gr\nd glass is fix$ 9 a frame ov] ! v]ni]1 :i* ?r[s a s(t light1 produc+ ! effect ( a dead surface ^u ! silv]1 or ! light is reflect$ f a c>dbo>d or ivory surface4 ,fig4 #acc %[s a common =m ( microscope = read+ a v]tical circle1 by :i* ! light is reflect$ f a :ite surface surr\nd+ ! field-glass end ( ! read]4 ,illu/ration3 ,fig4 #acc4--,reflect+ surface read]4 #ccb4--,%ades = ,v]ni]4--,x is v g5]al on ! ,cont95t to place ! divid$ read+ ( ! circle & its v]ni] on a plane p]p5dicul> to ! axis1 ,fig4 #abh1 & to place ! read] at a fix$ angle = d[n-!-l9e read+1 ! object-glass ( ! read] be+ con/ruct$ to focus p>allel rays4 ,9 ?is way ! division ( ! circle is foll[$ into its v]ni] or vice v]sa4 ,9 ?is case ! silv] may be %ad$ by gr\nd glass1 :i* gives a s(t1 pleasant read+ 9 mo/ lights4 ,! g5]al arrangem5t is %[n1 ,fig4 #acd2 ,l limb1 ,v v]ni]1 ,s %ade ( gr\nd glass1 ,m read]4 ,objection is made to glass %ades by civil eng9e]s z be+ too delicate & liable to fracture1 ) risk ( ! p>ticles ( glass gett+ into ! work+ p>ts ( ! in/rum5t4 ,to obviate ?is ! au?or has made ! %ade ( a piece ( ?9 horn or transp>5t ivory1 :i* appe>s to answ] v well & to save ?is risk4 ,illu/ration3 ,fig4 #acd4--,oblique read+ microscope ) %ade1 ,fr5* plan4 #ccc4--;,= ord9>y in/rum5ts ) no provision = %ad+1 a piece ( transp>5t horn ab\t #b in*es by #a in*es may be c>ri$ 9 ! wai/coat pocket1 & w be f\nd a great com=t if held ov] ! v]ni] :5 ! l9es appe> gl>y1 or ! horn may be plac$ 9 a pocket frame ) ! case conta9+ reflector = bubble read+1 ,fig4 #eb4 ,9 l>ge !odolites1 us$ = geodetic surveys1 ! object-glass ( ! micromet] microscope is sometimes surr\nd$ by a ?9 belt ( turn$ ivory4 ,?is ?r[s a v s(t light ^u ! divisions4 #ccd4--,micromet] ,microscope1 = ,read+ ,subdivisions4--,:]e m exact read+ is requir$ ?an is possible ) ! v]ni]1 z 9 ! case ( ! read+ ( circles #aj in*es or m to seconds1 a micrometrical microscope is employ$1 :i* gives means ( measur+ ! di/ance f l9e to l9e ( ! division ^u ! limb by ! displacem5t ( a web1 po9t1 or l9e mov$ by a f9e screw ) a divid$ head4 ,! great dem& ( late ye>s = r$uc+ ! size & increas+ ! accuracy ( !odolites has induc$ ! highe/ class mak]s to introduce micromet] read+ in/rum5ts ( six1 five1 & ev5 f\r-in* circles1 & _! accuracy is f> great] ?an is possible ) any in/rum5t ( ! same size t reads by v]ni]s4 ,( c\rse ! workman%ip 9 ^! in/rum5ts has to be ( a high] ord]1 & ! revis] e/imates ! accuracy ( ! micromet] ?r\gh magnification & ! necess>y ref9$ workman%ip to be at lea/ f\r times z great z ! v]ni] read+1 ) ! advantage t ! micromet] is mu* m c]ta9 & easi] to read4 #cce4--,! con/ruction ( ! read+ micromet] z orig9ally design$ by ,tr\ghton has n be5 mat]ially modifi$ 9 ^? 9 g5]al use4 ,c]ta9 ref9em5ts h be5 introduc$ = a/ronomical "w3 ^! are sometimes exp5sive & (t5 cumb]some1 s t !y ne$ n be consid]$ 9 relation to survey+ in/rum5ts4 #ccf4--;,9 all cases :]e micromet]s are us$1 ! /ructure ( ! framework ( ! in/rum5t :i* c>ries !m %\ld be made extremely rigid1 z v m9ute deflections or vibrations r5d] ! read+ to seconds ( arc impossible4 ,! numb] ( micromet]s appli$ to a circle is g5]ally #b1 #c1 or #e4 #ccg4--;,if a circle is to be read by micromet]s1 ! v]ni] is g5]ally disp5s$ )4 ,! circle is usually divid$ to read 9 #e4 ,! fir/ approximate read+ us$ to be tak5 by a s+le index l9e ) ! aid ( ! ord9>y read]1 ,fig4 #acj4 ,f ! index l9e ! degrees or m9utes 7 tak5 to ! la/ #e l9e indicat$4 ,s9ce ! introduction ( high-class engrav+ ma*9]y ! figur+ is made at ea* degree & is cle>ly read 9 ! microscope1 s t ! index read] is unnecess>y4 ,?is engrav+ is q a nice piece ( "w1 z to figure f #j to #cfj means ne>ly a ?\s& figures1 & on a #e-;in* circle ^! h to be less ?an #a_/ajj? ( an in* high4 ,only ! highe/ class mak]s are able to d ?is "w4 ,:5 a microscope is adju/$ to "o l9e x %\ld be obs]v$ t all ! o!r microscopes ^u ! same circle %\ld also read exactly to a l9e t %\ld be true f microscope to microscope to ! arc !y subt5d betwe5 ea* o!r4 ,illu/ration3 ,fig4 #ace4--,side elevation ( ,tr\ghton's micromet]4 ,illu/ration3 ,fig4 #acf4--,section ( micromet]4 ,illu/ration3 ,fig4 #acg4--,micromet] slide4 #cch4--,! ,micromet]1 z x is n[ te*nically t]m$ to include ! :ole piece ( app>atus1 is a comp\nd microscope consi/+ ( ?ree l5ses1 ) measur+ app>atus at ! mutual foci ( ! field-glass & ( ! two l5ses :i* =m ! eye-piece4 ,! field-glass1 :i* is plac$ ne>e/ ! divid$ arc1 is g5]ally an a*romatic microscopic l5s ( an in* or m 9 focus4 ,! eye-piece is ( ! ,ramsd5 =m1 ,fig4 #af4 ,by ! con/ruction ( ! comp\nd microscopic arrangem5t ! eye ( ! obs]v] may be plac$ at any conv5i5t di/ance f ! limb1 & any desir$ magnification may be obta9$ to assure micrometric nicety ( measurem5t4 ,! engrav+s repres5t ! micromet]1 ,fig4 #ace 9 side elevation1 ,fig4 #acf longitud9al section1 & ,fig4 #acg ! micrometrical slide1 :i* is %[n p>tly 9 section = demon/ration 9 all ! figures2 a ! micromet]1 q microscope body tube4 ,?is has a male screw outside at b1 ^u :i* !re are two coll>s dd ) cap/an heads4 ,^! coll>s hold ! microscope ^u ! read+ frame b at any requir$ di/ance f ! limb to secure prop] focal adju/m5t4 g objective tube4 ,?is screws into ! body tube & p]mits adju/m5t ( ! objective to ! division ( ! limb & ! micromet] index web by ! mill$ head s4 ,?is tube has a lock+ nut i to secure x f aft] movem5t :5 x is once prop]ly adju/$4 h an a*romatic object glass ( half an in* or ov] 9 focus4 e ! cas+ t receives ! eye-piece :i* screws into ! out] plate ( ! micromet]4 f ! eye-piece1 g5]ally made ab\t "o in* long4 ,?is slides by friction 9 its cell to produce di/9ct vision ( ! spid] l9es 9 ! micromet]4 #cci4--,! micromet] frame1 ,fig4 #acg1 a has a fix$ scale or comb1 ) five or m po9ts or tee? =m$ ^u x1 & a movable slid+ frame1 ^u :i* a spid] web or webs are ins]t$ & cem5t$ 9 f9ely engrav$ l9es to =m an index1 br\ght z ne>ly z possible to ! mutual focal plane ( ! object-glass & ! eye-piece4 ,! index web frame has a f9e screw ( ab\t a hundr$ ?reads to ! in* tapp$ into x4 ,! micromet] screw1 divid$ drum1 & mill$ head are n[ g5]ally con/ruct$ z %[n 9 ,fig4 #acg4 ,two spr+s press ^u ! index frame & ! out] frame1 & ?us keep ! drum up to its coll>4 ,! drum r is divid$ ^u its edge into sixty equal p>ts1 to read seconds ( arc g5]ally to a s+le l9e index4 ,! screw is mov$ by ! mill$ head beyond ! drum1 s t ! divid$ surface ( ! drum ne$ n be t\*$4 #cdj4--,! portion ( ! arc measur$ be+ g5]ally #e1 ! di/ance ( x1 z x appe>s at ! magnifi$ image ( ! arc at ! position ( ! index ( ! micromet]1 is made to correspond ) five turns ( ! micromet] screw1 ! head ( :i* divides ea* turn into #fj4 ,by ?is means ! #e is divid$ into #cjj1 t is1 to s+le seconds1 & by approximation ( ! int]spaces on ! micromet] head1 z f> z ! read+ is conc]n$1 to fractions ( a second4 ,! fix$ scale1 or comb1 z x is t]m$1 is commonly plac$ 9 ! focus ( ! eye-piece ) five webs ^u x1 fix$ to agree ) five turns ( ! screw or a rack ) po9ts at ! bottom4 ,^! webs or rack divide ! #e ( arc 9 m9utes1 & indicate ! numb] ( revolutions ( ! screw1 z %[n by ! displacem5t ( its index l9e4 ,a pair ( l9es or webs are commonly plac$ 9 mod]n in/rum5ts at #a "p1 to ensure c]ta9ty ( read+ by ! mean ( two obs]vations4 #cda4--,! magnitude ( #e ( arc dep5ds necess>ily ^u ! radius ( ! divid$ circle2 !re=e ! microscope ( ! micromet] has to be made to suit ! division x is requir$ to subdivide--t is1 us+ ! same micromet]1 ! small] ! circle ! high] ! magnify+ p[] is requir$ to be to take regi/] by ! same screw4 ,)9 a wide range ! micromet] is p]fectly adju/able1 to ensure exactness ^u ?is po9t1 by v>y+ ! di/ance ( ! object-glass f ! limb1 = :i* purpose ! microscope is made adju/able by ! pair ( screws dd :i* clamp x to its /&>d z already m5tion$4 ,! pr9ciple ( ?is adju/m5t is easily se51 = if we place ! object l5s at a di/ance equal to its sol> focus f ! limb1 ! image w em]ge 9 p>allel l9es2 b z we cause x to rec$e f ! limb1 ! image may be br\ght to any position )9 ! tube great] ?an ! sol> focus ( ! objective ( ! microscope4 ,! image is !re=e br\ght to a position :]e x may be pick$ up conv5i5tly by ! eye-piece4 ,9 ?is mann] we h only to make ! adju/m5t ( ! object-glass f ! limb su* z ! space ( any pair ( divisions ( ! limb may be magnifi$ up equal to ! displacem5t ( five turns ( ! screw = seconds measurem5t4 #cdb4--,! two po9ts :]e ! divisions & _! images are situat$ are t]m$ ! conjugate foci ( ! l5s1 & ! magnify+ p[] is proportional to ^! di/ances2 ?us1 if we call ! di/ance ( ! object1 t is ! limb1 f ! object l5s f1 & ! di/ance ( ! focal plane ( its image )9 ! tube ,f1 ! image w exce$ t ( ! object 9 ! ratio ( ,ff1 or ,f_/f w repres5t ! magnifi$ image4 ,by ?is me?od x w be se5 t ! expression ,f_/f w h an increas$ value1 if we ei!r increase ,f or dim9i% f1 :i* we h to consid] 9 ! con/ruction ( ! microscope to br+ x to ! conditions "u :i* x w adju/ to br+ ! micromet] screw exactly to its requir$ read+4 ,illu/ration3 ,fig4 #ach4--;,grubb's plan ( secur+ micromet] screw4 #cdc4--;,x is v g5]al 9 in/rum5ts at ! pres5t "t to tap ! micromet] screw directly into ! micromet] frame1 & to make ! drum & mill$ head a "p ( ! screw4 ,9 ?is case a v s(t motion may be giv5 to ! screw by divid+ its nut longitud9ally & br++ ! p>ts toge!r ) a c]ta9 am\nt ( spr+4 ,sir ,h[>d ,grubb1 ( ,dubl91 has plac$ a spr+ ball fitt+1 z %[n ,fig4 #ach at ,,ee1 ov] ! screw ^u 8 a/ronomical in/rum5ts1 :i* gives a v s(t motion to ! screw4 ,^! ref9em5ts are v important1 z x is n desirable t any undue pressure %\ld be put ^u a delicate in/rum5t :i* "u all conditions mu/ be made rigid en\gh to resi/ x1 & ! great] ! pressure requir$ to br+ ! in/rum5t to be>+ ! /rong] x mu/ be made4 ,illu/ration3 ,fig4 #aci4--,/anley's micromet] slide4 #cdd4--,/anley's ,micromet]4--,! au?or has made an arrangem5t 9 :i* ! screw has a long1 d\ble tubul> slid+ /em1 ,fig4 #aci4 ,! inn] /em :i* c>ries ! mill$ head has a groove cut d[n x1 into :i* a /ud f ! inside ( its cov]+ tube slides4 ,?is arrangem5t p]mits ! mill$ head to be press$ inw>ds or outw>ds 9 turn+ x )\t any pressure com+ ^u ! micromet] great] ?an ! friction ^u ! slid+ tube1 & t ( a weak spr+ :i* keeps ! /em ne>ly ext5d$ 9 its tube4 ,a simple ,hook's jo9t ,h is =m$ at ! head ( ! screw1 s t no "p ( ! weight ( ! h& comes ^u ! screw4 ,a tubul> gu>d-piece ,t prev5ts ! mill$ head hang+ d[n too f> :5 out ( use4 ,:5 ! screw is us$ x is lift$ to ab\t ! c5tre ( ! gu>d tube4 ,) ?is arrangem5t1 z no practical weight or pressure comes ^u ! micromet] f h&l+ x1 ! support+ frame-"w may be made mu* light] ?an is necess>y ) any o!r =m ( micromet]4 #cde4--,! au?or pref]s to =m ! micromet] scale & ! index ( f9e l9es engrav$ ^u p>allel work$ glass = survey+ in/rum5ts4 ,?is avoids ! risk ( break+ webs1 &1 :at is mu* m important1 he f9ds t ) engrav$ l9es on glass he is able to br+ ! scale & index exactly & p]man5tly into ! plane ( mutual foci ( ! object-glass & eye-piece by plac+ ! l9es ^u ! same faces ( glass1 ?us avoid+ ! great difficulty ( focuss+ to guess-"w ( an int]m$iate position betwe5 two sets ( webs at diff]5t di/ances4 ,! /rip ( glass ,a is fix$ by a clamp & two screws to ! side ( ! micromet] box4 ,! slip ,b is gr\nd & poli%$ to fit ,a4 ,b is c>ri$ by ! micromet] frame ,f1 :i* holds x 9 a clamp by two screws4 ,a spr+1 n %[n1 presses ,b aga9/ ,a1 s t any displacem5t ( ! micromet] l9es may be made by ! mill$ head4 ,! l9es ^u ,a are adju/$ to ! position ( ! circle !y are int5d$ to read at exactly #e or o!r quantity4 ,= ! small] in/rum5ts :i* w be mu* m frequ5tly us$ by ! surveyor a simpl] =m ( read+ is us$1 & z ! revis] is conv9c$ t 9 future ?is =m ( read+ w gradually replace ! v]ni] = all high-class "w1 a full description ( ?is v simple read+ is "h giv54 ,! revis] is confid5t1 aft] _m ye>s ( practice = ! mo/ accurate =m ( index1 t a po9t c]ta9ly /&s fir/1 a pair ( webs or l9es on glass1 betwe5 :i* ! division is se51 second2 & a s+le web or l9e on glass plac$ ov] ! division1 ?ird4 ,! comb m5tion$ 9 art4 #cci is done away )1 & "o revolution ( ! micromet] screw made to c>ry ! index ov] "o division ( ! limb4 ,= cle>ness ! engrav+s %[ only a #aj read+2 = a #e read+ ! divisions on ! limb are to #e in/ead ( #aj1 & ! micromet] head is divid$ & figur$ accord+ly4 ,illu/ration3 ,fig4 #adj4--,/anley's micromet] read+4 ,fig4 #adj %[s at ,c a portion ( ! !odolite circle z se5 ?r\gh ! micromet] microscope4 ,p is ! movable po9t]1 ,m ! micromet] head1 & ,i ! index or read+ l9e4 ,to use ! micromet] ! fir/ /eps are to c>efully focus ! po9t] ,p by means ( ! eye-piece until x appe>s cle> & p]fectly %>p1 & set ! reflector at ! bottom ( ! microscope s t x reflects suffici5t light to illum9ate ! divisions on ! circle4 ,!n1 by turn+ ! micromet] head ,m1 set ! po9t] ,p to ! c5tre ( its travel1 s t x cov]s ! ,v cut 9 ! bottom ( ! slide1 & leave ! #j ( ! micromet] head exactly opposite ! index l9e ,i4 ,n[ proce$ 9 ! same mann] ) ! o!r microscope4 ,aft] sett+ ! microscopes z describ$ above1 lightly clamp ! l[] clamp screw ( ! in/rum5t & release ! upp] "o4 ,n[ revolve ! upp] "p ( ! !odolite until #cfj degrees on ! circle appe>s exactly "u ! po9t] ( "o ( ! microscopes4 ,! o!r w !n be po9t+ to #ahj degrees1 & ! in/rum5t is set ready = measur+ ! fir/ angle4 ,illu/ration3 ,fig4 #ada4 ,we w presume n[ t a be>+ has be5 tak5 by ! telescope & x is requir$ to read ! angle1 & t on inspection ( ! micromet] x is se5 to be 9 ! position illu/rat$ at ,fig4 #ada1 viz41 betwe5 #bbg & #bbh degrees4 ,n[ z ! degree is subdivid$ into #f p>ts1 ea* ( ^! subdivisions mu/ repres5t #aj m9utes ( arc1 !re=e ! po9t] is situate betwe5 #bbg #cj & #bbg #dj4 ,x is n[ necess>y to measure exactly ! di/ance ( ! po9t] f ! division #bbg #cj1 :i* is done 9 ! foll[+ mann]1 by means ( ! micromet] head ,m4 ,illu/ration3 ,fig4 #adb4 ,?is micromet] head is s con/ruct$ t "o complete revolution ( x causes ! po9t] to exactly travel ov] ! space ( "o division on ! circle4 ,! head itself is divid$ into #aj prim>y p>ts1 :i* indicate s+le m9utes1 & ^! are subdivid$ into #f p>ts ( #aj seconds ea*1 !re=e 9 ord] to measure ! exact position ( ! po9t] 9 ,fig4 #ada x is only necess>y to turn ! head ,m until ! po9t] is exactly ov] ! previ\s division ( ! circle 7z %[n 9 ,fig4 #adb7 & read ! di/ance on ! micromet] head ,m4 ,9 ?is case ! head has be5 turn$ ?r\gh six ma9 divisions ( #a m9ute #f m9utes & two subdivisions ( #aj seconds #bj seconds1 giv+ a total read+ ( #f #bj1 ?is1 add$ to ! circle read+ ( #bbg #cj1 gives #bbg #cf #bj1 :i* is ! correct read+ ( ! angle4 ,x w be se5 t ?is me?od is v mu* simpl] & a great deal m accurate ?an any =m ( v]ni] read+1 & also t its great] accuracy p]mits ! use ( small] in/rum5ts4 ,?us a #e-;in* micromet] read+ !odolite is m accurate ?an a #f-;in* "o ) v]ni]s4 ,six-in* micromet] !odolites are usually divid$ to read to #e seconds ( arc4 ,! me?od ( read+ is ! same z describ$ above1 b 9 ?is case ! circle is divid$ to spaces ( #e m9utes ea* & ! micromet] head to #e ma9 divisions ( #a m9ute1 ea* ( ^! hav+ #ab subdivisions ( #e seconds1 :i* x is possible to aga9 subdivide by e/imation & s measure angles to #b seconds4 ,ano!r feature 9 fav\r ( micromet] read+ in/rum5ts is ! ease ) :i* !y c be adju/$4 ,) v]ni]s1 %\ld !y get out ( adju/m5t ?r\gh damage1 ! in/rum5t mu/ be return$ to a mak]2 ) micromet]s1 if ?r\gh r\gh usage or accid5t1 x is f\nd t aft] br++ ! po9t]s to ! c5tre ( _! ,v's & sett+ ! micromet] heads to #j !y are n exactly opposite "o ano!r 7#ahj degrees ap>t71 !n _! sett+ has become di/urb$ & mu/ be readju/$ 9 ! foll[+ mann]3--,fir/ br+ ! ,v ( "o micromet] to ! #cfj on ! circle1 !n see if ! ,v ( ! opposite micromet] is exactly at #ahj1 if n ?is c be easily set to x by means ( ! small adju/+ screw :i* w be f\nd at ! left end ( ! micromet] box1 t is1 ! opposite end to ! divid$ head4 ,hav+ exam9$ ! ,v's & adju/$ !m if necess>y1 ! next /ep is to set ! po9t]s ,p exactly to #cfj & #ahj respectively1 9 :i* position ! divid$ heads %\ld bo? read #j2 if !y d n d s reset !m z foll[s3 ,take a screw-driv] & slack5 ! small screw :i* is 9 ! c5tre ( ! divid$ head2 ?is w free ! divid$ rim s t x c be turn$ )\t %ift+ ! position ( ! po9t]4 ,turn ! divid$ rims until !y read exactly #j at ! index l9e & retight5 ! screws4 ,?is completes ! adju/m5t4 ,illu/ration3 ,fig4 #adc1 #add4--,sections ( clamp & tang5t 9 two directions4 #cdf4--;,clamp & ,tang5t ,adju/m5t4--,! v]ni] read+ to ! circle1 :5 ?is 0 adju/$ by ! h&1 0 sc>cely practicable at ne>ly its full value until ! discov]y ( ! clamp & tang5t screw motion 0 made4 ,?is useful inv5tion is due to ,helvetius1 ! celebrat$ a/ronom] ( ,danzig 7ab\t #afej74 ,by ?is me*anical arrangem5t ! circle or arc is left q free to move ab\t its axis until ! clamp is screw$ d[n1 :i* !n fixes x firmly4 ,! fix+ arrangem5t ( ! clamp is atta*$ to a solid "p ( ! in/rum5t1 b is s con/ruct$ t :5 x is clamp$ x may yet be mov$ )\t unclamp+1 9 relation to ! fix$ "p ( ! in/rum5t1 by ! tang5t screw :i*1 z its "n indicates1 is plac$ 9 a direction tang5tial to ! circle or arc4 ,?is arrangem5t may take _m =ms 9 detail1 two ( :i*1 ! mo/ g5]al & especially adapt$ to survey+ in/rum5ts1 w be describ$4 ,illu/ration3 ,fig4 #ade4--;,elevation & "p section ( clamp & tang5t4 #cdg4--,! above illu/rations1 ,figs4 #adc1 #add1 repres5t a clamp & tang5t motion 9 two sections at "r angles to ea* o!r4 ,?is =m is common to v]tical circles & arcs g5]ally1 ( a !odolite1 arc ( sextant1 circles ^u "s m9+-dials1 protractors1 & _m o!r in/rum5ts4 ,fig4 #ade is p>tly a front elevation ( ! same1 b ) "p ( ! clamp screw ,a cut (f4 ,! /em ( ! tang5t screw is %[n 9 section at ,e4 ,9 all ! figures ,l is ! limb ( ! circle or arc4 ,?is has a groove at its "u side at ,g1 into :i* a fillet ( ! clamp+ piece ,c is ins]t$ to make ! clamp slide freely ab\t ! p]iph]y ( ! circle :5 ! clamp+ screw ,a is loose4 ,a spr+ is sometimes ins]t$ to op5 ! clamp betwe5 ! slid+ piece ,k & ! clamp ,c4 ,,ff1 ,figs4 #adc1 #add is ! tang5t nut to ,e4 ,?is nut is sawn d[n & has a cross screw to keep suffici5t tightness to prev5t loss ( "t1 & yet to all[ ! tang5t screw to "w pleasantly at ! same "t t x holds ! circle & v]ni] q dead to ! position to :i* x is adju/$ by ! screw4 ,! tang5t nut ,f has to move to ! direction horizontal to ! plane ( ! tang5t screw2 !re=e x has an axis v]tical to ! plane ( ! clamp4 ,?is is %[n at ,k4 ,! axis is held d[n firmly by a nut & a wa%] fitt$ ) a squ>e hole1 to prev5t ! nut unscrew+4 ,! tang5t screw has a coll> fitt+ or %ank at ! tang5t boss ,b1 :i* is turn$ d[n f ! full-siz$ metal ( ! screw4 ,! fell[ coll> on ! out] side ( ! boss is =m$ by ! %ank ( ! mill$ head ( ! tang5t screw ,d4 ,! hole ?r\gh ! mill$ head is made squ>e1 s t x c be adju/$ up to ! boss )\t risk ( aft] unscrew+ by friction by ! screw ,e4 ,?is is tight5$ up by means ( a screw-driv] appli$ at ,e4 ,! boss ,b has a v]tical axis ,n1 simil> to ! tang5t nut1 & is atta*$ to a solid "p ( ! in/rum5t by ! wa%] & nut %[n at #j4 #cdh4--,! above con/ruction is solid & good1 & w be> consid]able we>2 b !re is a little delicacy ( t\* requir$ to adju/ ! coll>s to ! boss & to give pleasant tightness to ! screw2 a bett] plan is to disp5se ) ! split 9 ! tang5t nut & ! inn] coll> turn$ on ! tang5t screw1 & place a spiral spr+ ov] ! tang5t screw :i* foll[s ! adju/m5t1 or 9 "s cases a long b[ spr+ may be conv5i5tly us$ 9 place ( ! spiral4 ,^! plans answ] v well3 "o ( !m w be pres5tly describ$ = axis clamp+4 ,9 place ( ! groove at ,g ! clamp is sometimes con/ruct$ to move on an arm direct f ! axis ( ! circle4 ,?is is on ! av]age a pleasant] motion1 b 9 complex in/rum5ts x w\ld (t5 int]f]e ) ! motion ( o!r necess>y p>ts4 #cdi4--;,axis ,clamp & ,tang5t4--,?is is g5]ally us$ to br+ ! horizontal axis ( an in/rum5t to be>+1 & is made indep5d5t ( ! circle & v]ni]4 ,! ord9>y =m1 :i* is v effective :5 prop]ly con/ruct$1 is %[n ,fig4 #adf4 ,?is =m is us$ = clamp+ ! v]tical axis ( a !odolite1 m9+-dial1 ,y-level1 & "s o!r in/rum5ts4 ,! clamp ,c surr\nds ! axis z a coll>1 f :i* two lugs 9 ! same ca/+ are project$ at a4 ,^! are br\ght tight ^u ! out] axis socket ,b by means ( ! screw ,w1 :i* has a w+-nut head to give good pur*ase4 ,9 ! con/ruction ( ?is =m ( clamp ! coll> %\ld be fitt$ & gr\nd to its be>+s ) ! lug 9 ! solid1 & ! cut at a be sawn ?r\gh aft]w>ds4 ,illu/ration3 ,fig4 #adf4--;,clamp & tang5t to a v]tical axis4 #cej4--,! tang5t screw adju/m5t is %[n at ,t1 mov$ by ! mill$ head ,m1 ! boss ,e be+ fix$ to ! in/rum5t4 ,?is "p ( ! arrangem5t is j ! same z t describ$ above = a v]ni] tang5t4 ,objection has sometimes be5 made to ?is =m ( clamp1 t x t5ds to become weak aft] a "t f ! con/ant clamp+ & releas+1 :i* causes loss ( ela/icity 9 ! metal4 ,:5 ?is occurs x is no d\bt due to ! metal ( ! clamp n be+ good gun-metal2 or1 if brass1 n ?or\ghly press$ or hamm]$ be=e ! piece is made up4 ,a plan1 9 n uncommon use 9 ,g]many1 ( avoid+ ?is suppos$ s\rce ( weakness is to br+ up a tumbl+ piece direct on ! axis by a screw4 ,?is is %[n 9 ,fig #adg1 screw ,w2 tumbl+ piece ,a4 ,?is produces a direct clamp ^u ! axis socket ,b4 ,! clamp r+ ,,cc is made loose on its socket4 #cea4--;,9 practice x is f\nd impossible to clamp ! axis ( a !odolite )\t di/urb+ ! c5tre m or less4 ,9 "s exp]im5ts ! au?or made he f\nd ! direct or tumbl+ piece clamp ,fig4 #adg1 al?\gh x holds firmly1 di/urbs ! c5tre mu* m ?an ! clasp+ clamp ,fig4 #adf4 ,!re=e :5 ! =m] is us$ ! clamp %\ld be ^u a /rong flange4 ,?is increases weight1 & x c sc>cely be s well = a portable in/rum5t4 ,9 all cases1 9 ! con/ruction ( ! in/rum5t1 clamps %\ld be fitt$ & screw$ d[n be=e ! c5tre is gr\nd & f9i%$4 ,?is ensures ! c5tre be+ made correct 9 its clamp$ position1 9 :i* x w aft]w>ds be us$4 ,illu/ration3 ,fig4 #adg4--;,clamp & tang5t to v]tical axis1 ,g]man plan--,hunu4 ,! arrangem5t ,fig4 #adg %[s also a spr+ ,s fall+ ^u a /ud at ,e1 fix$ ^u a "p ( ! in/rum5t ^u :i* x acts z a fulcrum4 ,! spr+ %\ld be ( h>d roll$ ,g]man silv]4 ,9 ?is case ! tang5t screw ne$s no split or o!r adju/m5t to make x tight1 z all loss ( "t is tak5 up by ! spr+4#ad ,! plan is f\nd practically to answ] fairly2 b unless ?is is v c>efully made !re is a want ( solidity 9 ! movem5t :i* a well-fitt$1 direct-act+ tang5t screw possesses4 #ceb4--,! ,fr5* g5]ally 9 all _! sup]ior in/rum5ts clamp ^u a flange c>ri$ out f ! l[] rim ( ! socket1 ) ! screw plac$ longitud9ally to ! axis4 ,:5 ?is plan is v c>efully c>ri$ out1 s t ! clamp+ has nei!r t5d5cy to raise or l[] ! socket-piece1 x is no d\bt v good4 ,9 l>ge in/rum5ts1 :]e weight is no object & ! flange may be made l>ge1 x is c]ta9ly ! be/ plan4 ,9 su* cases ! clamp may be releas$ z a free fitt+ to prev5t ! possibility ( /ra94 ,fig4 #adh %[s ! ,fr5* plan atta*$ to a tribra*3 ,s socket1 ,f flange1 ,c clamp+ screw1 ,t tang5t screw4 ,! tang5t 9 ?is arrangem5t acts aga9/ a spiral spr+ conta9$ 9 a tube ,a1 :i* gives a v /eady motion to ! in/rum5t4 ,illu/ration3 ,fig4 #adh4--;,fr5* axis clamp & tang5t4 #cec4--,"s p>ticul>s ( ! c>e requir$ 9 ! manufacture ( ! tang5t screw 7 giv51 art4 #bb4 ,! te/ = ! equality ( ?is screw1 :i* is important :5 x moves a v]ni]1 is to loos5 its clamp & to see :e!r x works equally1 firmly1 & smoo?ly at all p>ts :5 x is turn$ d[n f end to end4 ,! te/ = its /raightness is to screw d[n ! clamp1 !n to notice any little m>k on ! mill$ head ( ! tang5t screw1 or make a slight m>k ^u x1 & to place ?is m>k upp]mo/1 & !n to take a read+ ) ! v]ni]1 !n to turn ! mill$ head a qu>t] turn & take ano!r read+1 & aga9 ano!r qu>t]1 & s on consecutively4 ,by comp>+ ! rates ( read+ ( ! v]ni] at ! qu>t] turns1 if we f9d ^! equal ! screw is /raight4 ,a little all[ance is necess>y = imp]fect "w4 ,if ! "w is v bad at "s qu>t] turns !re w be an advance at ! opposite qu>t] ( ne>ly d\ble ! prop] mean quantity4 #ced4--;,= ,te/+ & ,adju/+ ! ,fitt+ ( ! ,tang5t ,screw4--,! clamp %\ld be tight5$ d[n & ! ball ,b1 ,fig4 #add1 held tightly betwe5 ! ?umb & =ef+]2 !n1 by us+ a g5tle reciprocat+ motion 9 ! direction ( ! tang5t j suffici5t to move ! circle1 if !re is any loos5ess 9 ! screw or ! ball fitt+ ,b x w be felt z a j>1 or te*nically1 a slight loss ( "t4 ,if ?is be 9 ! ball ,b x c be tak5 up by ! screw ,e at its end4 ,if x be 9 ! screw x c be tak5 up by ! cross clamp screw4 ,if x be 9 nei!r ( ^!1 x may be 9 "o or bo? ( ! axes ,n & ,k4 ,9 ?is la/ case x w ne$ refitt+4 ,x appe>s a some:at simpl] te/ ) a !odolite to lightly press ! telescope on "o side ( ! eye-piece & take a read+ ( ! v]ni]1 & !n to press ! o!r side & aga9 take a read+4 ,?is1 possibly1 indicates loss ( "t 9 ! clamp & tang5t if !re is f\nd any diff]5ce 9 ^! read+s2 b ?is w\ld n be ) any c]ta9ty1 z ! fault might be 9 "s o!r "p ( ! in/rum5t4 ,x1 nev]!less1 is a simple plan to te/ ! :ole in/rum5t1 includ+ ! clamp & tang5t1 al?\gh ?is does n localise any defect !re may be 9 any special "p ( x4 #cee4--,use & ,we> ( ! ,clamp4--,! common fault ( a novice :5 he comm5ces to use an in/rum5t is t he applies too mu* viol5ce to all clamp+ p>ts4 ,?us we f9d ! l[] p>allel plate ( an in/rum5t soon becomes deeply ind5t$1 & ! clamp ( ! tang5t screw (t5 /ra9$1 or its screw worn loose by extreme clamp+4 ,! be/ rule to avoid ?is ) a clamp is to make a p]sonal te/ ( h[ little =ce is requir$ to produce suffici5t hold = ! action ( ! tang5t screw1 & :5 ?is is f\nd out to try to clamp only slightly 9 excess ( ?is4 ,a novice sc>cely recognises ! p[] ( a screw4 ,x is1 p]haps1 a fault ( "s mak]s ( giv+ mu* too l>ge heads to clamp screws :i* to a c]ta9 ext5t p]mits ?is ov]/ra9+ f clamp+4 ,9 discuss+ ?is matt] ) a sci5tific civil eng9e] ^u an in/rum5t :i* _h be5 v mu* /ra9$1 to :i* small clamp+ screw heads 7 sugge/$1 ?is g5tleman repli$ t he look$ to ! optician to supply in/rum5ts1 n bra9s1 & made ! us] responsible2 b1 really1 a "y surveyor is g5]ally s int5t on ! object ( 8 "w t he _c consid] ! me*anical details ( 8 in/rum5t1 to :i* 8 att5tion possibly has nev] be5 prop]ly direct$2 s t !re is a policy 9 cutt+ (f possibility ( injury to ! in/rum5t :]e ?is c be conv5i5tly done4 #cef4--,use & ,we> ( ! ,tang5t ,screw4--,see+ t ! axis ( an in/rum5t is q free to ! ext5t ( ! loss ( "t on ! tang5t screw :i* holds x1 & t ?is fre$om1 by any slight t\* ( ! telescope1 may cause a diff]5ce ( read+--9 "s cases ( sev]al m9utes ( arc--x becomes important to obs]ve t ! tang5t screw is 9 good ord]4 ,?is matt] consid]$ at its full value1 we may wond]1 p]haps1 :at k9d ( "w may h be5 done ) ! tang5t screw loose & worn d[n 9 its c5tral "p1 z we f9d x 9 _m old in/rum5ts s5t = repair4 ,a great am\nt ( ! common defects we f9d 9 worn tang5t screws might h be5 prev5t$ by us+ c]ta9 precautions2 & ev5 ! mu*-worn tang5t screws w\ld sometimes g on fairly by a diff]5t me?od ( use f t to :i* !y h evid5tly be5 submitt$4 ,! we> ( a tang5t screw is due pr9cipally to ! fact t ?is screw is necess>ily oil$ to make x "w freely1 & t ! oil$ "p be+ expos$ to du/1 ?is du/ atta*es itself & works into ! ?read ) ! oil s z to cut bo? ! screw & ! nut4 ,precaution is necess>y t ?is %\ld be obviat$ z f> z possible4 ,"o precaution may be tak51 t :5 ! screw is oil$1 say once 9 ?ree mon?s1 ! p>ts outside ! nut %\ld be clean$ (f q dry ) a few /r&s ( ?read4 ,! oil left 9 ! nut1 if ! screw has be5 turn$ ?r\gh x1 w be q suffici5t to lubricate ! screw4 ,ano!r bett] precaution is to use only "o "p ( ! screw = a p]iod1 say "o mon?4 ,! screw may be divid$ m5tally into ?ree p>ts--ne> "p1 middle "p1 & end "p4 ,if "o "p only be us$ = a p]iod1 & ! v]ni] be set 9 us+ ! in/rum5t s t n m ?an ab\t #a ( motion is requir$ ( ! screw1 no grit c be c>ri$ f> into ! c5tre ( ! nut2 & if ! precaution ( clean+ ! screw ) ?read be tak5 e "t ! in/rum5t is return$ to its case aft] a day's "w1 ! screw be+ left at ab\t ! same place on ! screw & nut1 x w keep true ) little we>4 ,:5 ano!r "p ( ! screw is tak5 into use1 ?is "p %\ld be fir/ clean$ ) ?read & !n oil$ ) wat* oil1 aft] :i* ! =m] position ( ! nut %\ld be clean$ q dry ) ?read4 ,treat$ 9 ?is mann] a tang5t screw w la/1 9 con/ant we>1 = t5 ye>s or s1 keep+ 9 fairly good ord]4 ,:]e a spr+ is us$ to take up loss ( "t !re is less risk1 & ! only precaution necess>y is to be sure ! spr+ cont9ues to act prop]ly4 ,!re is g5]ally1 h[ev]1 a little m we> ) a spr+ ?an ) a free ?read4 #ceg4--;,if ! in/rum5t be n t\*$ aft] ! tang5t is set1 & !re is no w9d to cause vibration1 ! in/rum5t w read correctly al?\gh ! tang5t may be out ( ord]4 ,b aft] ! adju/m5t by ! tang5t screw1 :i* may cause a di/urbance1 x is always necess>y to set ! microscope to ! v]ni]4 ,?is is "o important reason :y ! microscope %\ld move z s(tly z possible1 & t x is advisable to c5tre x ^u ! axis4 ,:]e any d\bt ( ! quality ( ! tang5t exi/s1 ! telescope %\ld be reobs]v$ = v]ification ( its position aft] read+1 :i* is also und\bt$ly ! safe/ 9 all cases4 #ceh4--,"s contrivances h be5 appli$ to tang5t screws to prev5t we> f du/1 & also to take up ! nut aft] we>4 ,a v good plan1 common 9 ,am]ican in/rum5ts1 is to ins]t ! end "p ( ! screw beyond ! nut 9 a clos$ tube4 ,?is entirely prev5ts du/ f re/+ on ?is "p2 & if ! precaution be tak5 to clean ! expos$ "p ( ! screw aft] use x is v effective = pres]vation4 ,?is plan ! au?or has comb9$ ) a spr+ arrangem5t1 :i* appe>s to r5d] x v safe f loss ( "t & mu* we>4 ,?is arrangem5t is1 h[ev]1 a little exp5sive to make1 !re=e c only be appli$ to high-class in/rum5ts4 ,fig4 #adi1 ,c nut1 ?r\gh :i* tang5t screw passes2 ,b tang5t boss1 ,a mill$-head1 ,h cov]+ tube to ! po9t ( ! screw1 ,,gg ,,ee pair ( telescopic tubes :i* cov] ! screw4 ,a ,g]man silv] or plat9um spr+ works inside ^! tubes1 keep+ a con/ant sep>at+ pressure betwe5 ,c & ,b to take up any loss ( "t 9 ! screw4 ,illu/ration3 ,fig4 #adi4--,protect$ tang5t screw ) helical spr+4 #cei--;,free ,tang5t ,screw4--,!re is always a risk ( a tang5t screw ( any fix$ k9d produc+ a c]ta9 am\nt ( /ra9 ^u ! in/rum5t1 !re=e1 :]e practicable1 x %\ld be made free4 ,! illu/ration1 ,fig4 #aej1 %[s ! =m ( free tang5t ! au?or n[ applies to _m in/rum5ts4 ,! c5tre /ud is clamp$ to ! l[] "p ( ! in/rum5t by ! screw %[n 9 dott$ l9es4 ,to ! left h& a pi/on conta9+ a spiral spr+ c>ries a press+-rod aga9/ :i* ! screw to ! "r h& works4 ,illu/ration3 ,fig4 #aej4--;,free tang5t adju/m5t4 #cfj4--,loss ( ,"t by ,we> ( ! nut is v>i\sly tak5 up :5 no spr+ is us$4 ,"o plan 0 %[n ( splitt+ x up4 ,a plan common 9 ,g]many is to make ! nut 9 two pieces1 :i* are br\ght up by two screws4 ,?is is a v effective plan4 ,! au?or has f\nd a tumbl+ piece arrangem5t also effective4 ,fig4 #aea1 ,s section ( tang5t screw1 ,t tumbl+ piece mov$ by ! adju/+ screw1 %[n above1 = we> ( ! tang5t screw4 ,?is adju/+ screw ,a %\ld be tapp$ tight )\t oil1 & put toge!r dry to prev5t its rec$+ by pressure4 ,illu/ration3 ,fig4 #aea4--,tumbl+ piece adju/m5t = we> ( tang5t screw4 #cfa4--;,hypot5use & ,base4--,o!r trigonometrical values besides ! division ( ! circle into equal p>ts are occasionally plac$ on in/rum5ts = special purposes4 ,! mo/ common ( ^! is ! scale ( diff]5ce ( hypot5use & base1 :i* is g5]ally plac$ ^u ! back ( ! v]tical arc ( a !odolite & ^u "s dials & cl9omet]s4 ,! division = ?is purpose is g5]ally done by h&4 ,! scale gives a p]c5tage diff]5ce = c]ta9 angles4 ,?us :5 us$ ) *a9 measurem5t1 x gives ! numb] ( l9ks ( ! *a9 to be d$uct$ p] *a9 ( #ajj l9ks = ! incl9ation ( l& t ! !odolite or o!r in/rum5t indicates 9 foll[+ ! surface cont\r4 #cfb4--;,a ,horizontal ,scale ( ,tang5ts 0 plac$ ^u ! survey+ !odolites by ,ramsd54 ,?is 0 divid$ ^u a scale c>ri$ by ! v]ni] plate1 :i* read to ! z]o l9e 7#j7 ( ! limb4 ,x is f\nd 9 practice m accurate to take ! tang5t to any curve f a scale ( tang5ts1 z1 = in/ance1 t 9 ,moleswor?'s pocket-book1 & set ?is (f ^u ! limb by means ( ! v]ni]4 #cfc4--;,gradi5t ,scale4--,civil eng9e]s engag$ on railway "w occasionally h a scale ( gradi5ts ^u ! back ( ! v]tical arc #a to #ajj1 #aej1 #bjj1 etc4 ,^! are bett] read f ! circle ) v]ni] f a table ( gradi5t arcs4 ,,footnotes3 #ad ,! illu/ration is tak5 f ,die geometris*5 ,in/rum5te1 ,dr4 ,g4 ,*r4 ,k4 ,hunu4 ,hanov]1 #ahfd4 ,,*apt] ,,vii4 ,,!odolites--,,con/ructive ,,details ,,( #e-;,,in* ,,& #f-;,,in* ,,transits-- ,,special ,,additional ,,p>ts--,,plummets ,,) ,,screw ,,adju/m5ts ,,( ,,improv$ ,,=m--,,/rid+ ,,level--,,lamp--,,adju/m5t ,,( ,,axis ,,ov] ,a ,,po9t--,,sol> ,,atta*m5t--,,photographic ,,atta*m5t4 #cfd4--,! ,!odolite is ! mo/ p]fect in/rum5t = measur+ bo? horizontal & v]tical angles by ! aid ( a telescope & graduat$ circles4 ,= ! purpose ( survey+1 ! !odolite is mo/ly employ$ to take a sy/em ( triangles ^u ! horizontal plane ( ! surface ( ! l&1 & ( objects at any position 9 :i* !y may be plac$4 ,:5 altitude angles are tak5 sep>ately ^! are g5]ally appli$ to give corrections to *a9 or o!r actual measurem5ts ^u ! surface by calculation ( ! diff]5ce ( hypot5use & base4 #cfe4--,! !odolite 9 all its ess5tial features1 z diff]5tiat$ f sight$ compasses = tak+ angles1 m5tion$ by ,digges1#ae 0 ! inv5tion ( ,jona?an ,sisson1 a celebrat$ ma!matical in/rum5t mak] ( ! beg9n+ ( ! #ah? c5tury4#af ,great improvem5ts 7 aft]w>ds made 9 ?is in/rum5t by ,ramsd51 :o br\ght x up ne>ly to its mod]n effici5cy by ! introduction ( ! transit pr9ciple4#ag ,lat] improvem5ts 9 portable in/rum5ts consi/ 9 ! application ( ! transit pr9ciple to ! telescope1 :i* 0 =m]ly appli$ to a/ronomical & ! l>g] geodetic in/rum5ts only4 ,o!r improvem5ts h be5 made m rec5tly 9 con/ructive details4 #cff4--,!odolites 7 commonly made ( two di/9ct types1 :i* 7 orig9ally di/+ui%$ z pla9 !odolites & transit !odolites4 ,9 ! pla9 !odolite ! telescope moves ?r\gh an arc ( ab\t #de upw>ds or d[nw>ds f ! horizontal plane1 b v few ( ^! are n[ made comp>$ ) ! numb] ( transit !odolites 9 :i* ! telescope may take a complete revolution ^u its horizontal axis1 s t a back & =e sight may be tak5 by a half revolution4 ,?is diff]5ce ( con/ruction entails a diff]5ce 9 ! mann] ( m\nt+ ! telescope to correct its adju/m5ts4 ,9 ! transit ! accuracy ( c5tr+ & read+ is easily discov]$ by tak+ a back & =e sight at a di/ance z equival5t to an arc ( #ahj1 :i* may be read on any "p ( ! limb by transitt+ ! telescope1 :]e9 ! correspond5ce ( ?is arc to ! read+ ( ! limb to "r & left h&s w detect error4 ,) ! pla9 !odolite ! equival5t me?od ( exam9ation is effect$ by plac+ ! telescope 9 ,y's1 z previ\sly discuss$ = ! ,y-level1 & turn+ x end = end on its be>+s1 a process liable to di/urb ! direction ( ! telescope unless special c>e be tak54 ,9 ! foll[+ description ( ! details ( con/ruction ( a !odolite x w be conv5i5t to take ! transit =m ( in/rum5t1 z ?is is m compreh5sive1 ! orig9al patt]n be+ select$1 z ?is may be con/ruct$ ) ! limit$ am\nt ( tools g5]ally f\nd 9 a survey+ in/rum5t work%op4 ,illu/ration3 ,fig4 #aeb4--e-;in* transit !odolite 7old =m74 #cfg4--,! size ( a !odolite is fix$ te*nically by ! diamet] ( ! l9e ( division ^u ! horizontal circle4 ,a #e-;in* or #f-;in* !odolite is ! l>ge/ size t may be c>ri$ com=tably 9 a s+le case2 & no great advantage is ga9$ by hav+ an in/rum5t beyond ?is size if ! "w is t ( ! ord9>y surveyor on t[n & c\nty surveys4 ,! v]ni]s ( #d- & #e-;in* in/rum5ts read %>ply to s+le m9utes ( arc1 :i* is z ne>ly z c be plott$ ) any degree ( c]ta9ty ) an ord9>y protractor read+ by v]ni] also to m9utes only2 #f-;in* in/rum5ts read to #cj b g5]ally to #bj seconds4 ,occasionally #d-;in* !odolites are select$ = lightness at a sacrifice ( capability & ( di/9ct & exact read+4 ,! foll[+ table gives ! av]age weight ( ! transit !odolite illu/rat$ on ! la/ page3-- ,in/rum5t4 ,case4 ,ov]case4 ,tripod4 #d-;in* ,transit4 #aa lbs4 #h lbs4 #d lbs4 #h lbs4 #e-;in* #ac #i #e #i #f-;in* #ai #aj #f #aa #h-;in* #cf #bj #aj #ah ,if ) lamp extra ab\t lb4 ,if ) /rid+ level extra ab\t lb4 ,x w be se5 t ! #e-;in* in/rum5t ( ?is class ) cases & tripod1 say altoge!r #cf lbs41 is really ( q z mu* weight z a fairly /rong man c c>ry ?r\gh a h>d day's "w4 ,! #e-;in* in/rum5t is !re=e becom+ m & m popul> ) practical civil eng9e]s1 & its p]=mance1 if ( good mod]n "w1 is q equal to ! #f-;in* ( less ?an half a c5tury ago4 #cfh4--;,by giv+ a description 9 detail ( a transit !odolite1 ! g5]al pr9ciples ( a great numb] ( o!r in/rum5ts1 p>ticul>ly ^? ( l>g] dim5sions1 w be includ$1 except = c]ta9 details t ! specialities ( ! p>ticul> in/rum5ts dem&4 ,! mo/ conv5i5t plan to foll[ 9 ?is description w be to take ! /ructure ( a #f-;in* transit !odolite ( common con/ruction1 z x is built up f its base1 piece by piece1 accord+ to ! rule ( ord9>y /ructure2 :]e m mod]n !odolites v>y mo/ly f ?is is 9 hav+ _m p>ts %ap$ out ( ! solid1 :i* are screw$ toge!r 9 ! =m illu/rat$4 #cfi4--,! ,tripod ,/& ( a !odolite ( #f in*es & "u is g5]ally made id5tical ) t ( a level1 a common =m be+ t describ$ = a dumpy1 art4 #baf4 ,! arrangem5t ( "o turn-up leg1 z %[n ,fig4 #fc1 is v advantage\s = ! !odolite if x is to be us$ on m\nta9\s or ev5 v hilly gr\nd4 ,= in/rum5ts exce$+ #f in*es a fram$ /&1 :i* w be describ$ fur!r on1 is bett]4 ,"s mak]s use a fram$ /& = a #f-;in* in/rum5t4 ,! rigidity ( ! /& ought to be q equal to t ( ! "w 9 ! !odolite1 or a little 9 excess1 & :5 ?is is atta9$ x is suffici5t4 ,:]e ! /&s ( !odolites s (t5 fail is f ! defective con/ruction ( ! tripod head1 n at all f defici5cy ( timb] 9 ! tripod itself2 & ov]load+ ?is1 9 add+ weight )\t att5tion to sci5tific con/ruction1 is worse ?an useless4 #cgj4--;,9 ! foll[+ description ( ! transit !odolite ! p>allel plate sett+-up arrangem5t is tak51 z ?is is at ! pres5t "t 7#aiad7 /ill 9 use 9 ?is c\ntry & 9 ,am]ica4 ,!re is nev]!less great probability t x w n long cont9ue to be s1 z ye> by ye> ! tribra* sy/em1 describ$ art4 #bcc1 = levels is com+ m =w>d1 bo? = levels & !odolites4 ,?is tribra* sy/em ! au?or holds to be mu* m sci5tific1 & :5 ?or\ghly und]/ood1 m simple & exp$iti\s to "w )4 ,x is also to be recomm5d$1 z !re is no possible risk ( /ra9 ^u ! g5]al "w ( ! in/rum5t1 nor risk ( error f di/ortion ( ! v]tical axis f /ra9 9 sett+ x up to adju/m5t4 ,a con/ructive draw+ ( a common transit !odolite ) p>allel plates is %[n ,fig4 #aec1 ( :i* ! foll[+ is a detail$ description4 ,illu/ration3 ,fig4 #aec4--f-;in* transit !odolite--back view1 ) sections4 #cga4--,! ,l[] ,p>allel ,plate ,n4--,?is has a l>ge boss-piece tak5 up f its c5tral "p1 :i* =ms a dome ( a holl[ globul> section1 te*nically t]m$ ! socket1 %[n at ,x4 ,9 ! int]ior ( ! l[] "p ,n a co>se female screw is cut1 ( ab\t f\rte5 ?reads to ! in*1 :i* is us$ to atta* ! in/rum5t to its tripod4 #cgb4--,! ,upp] ,p>allel ,plate is con/ruct$ z a flange f a solid boss ,l4 ,?is piece is g5]ally made 9 gun-metal ( a =m z solid z possible1 to resi/ ! /ra9+ action ( ! p>allel plate screws4 ,! boss is prolong$ d[nw>ds by a /em-piece1 ^u ! l[e/ "p ( :i* a ball coll> ( globul> section is firmly screw$4 ,! screw is turn$ by means ( two opposite holes1 into :i* a p[]ful =k$ screw-driv] is ins]t$1 until x is jamb$ up too tightly aga9/ its %\ld] to ev] become loose by ! ord9>y use ( ! in/rum5t4 ,! ball coll> fits into ! socket c>ri$ up f ! l[] p>allel plate4 ,! :ole ( ?is globul> arrangem5t is t]m$ ! ball & socket4 ,! boss ,l ( ! upp] p>allel plate1 ) its /em1 has a holl[ conical hole ?r\gh its axis1 into :i* ! body-piece1 to be describ$1 fits accurately4 ,^u its out] upp] "p an inset coll> is =m$ :i* acts z a guide to ! clamp ,k4 ,at ! out] edge ( ! p>allel plate ,m f\r v]tical1 conical holes are made1 :i* take socket-pieces1 :i* are tapp$ z nuts to ! p>allel plate screws ,m4 ,^! socket-pieces are jamb$ into _! holes tight home to _! %\ld]s4 ,! socket-pieces are made sep>ate1 bo? to give a great] l5g? ( female screws ?an ! ?ickness ( ! plates1 & t !y may be easily re/or$ at any "t if worn loose 9 ! ?reads by ! action ( ! plate screws4 #cgc4--,! ,p>allel ,plate ,screws4--,"o 9 elevation is %[n at ,m1 ) its po9t dott$1 & "o 9 section at ,m4 ,! f\r p>allel plate screws are 9 opposite pairs1 plac$ exactly at "r angles to ea* o!r 9 a l9e pass+ ?r\gh ! v]tical axis ( ! in/rum5t4 ,^! are made ( gun-metal ab\t #c_/h in* 9 diamet]1 ) a deep ?read ( ab\t ?irty-two to ! in*4 ,!y require cutt+ on a nice /eady screw-cutt+ la!4 ,! l[] po9ts ( ! screws are slightly dom$1 suffici5tly only = ! am\nt ( rock+ !y h to take1 s z to impress ! l[] p>allel plate z little z possible4 ,! mill$ heads ,m are plac$ betwe5 ! p>allel plates1 n above1 z previ\sly describ$ = levels4 ,!re be+ a con/ant /ra9 ^u ^! screws 9 use & by intrusion ( grit f fly+ du/ !y soon become worn4 ,aft] we> ! ?reads may be recut deep]1 & new socket-pieces fitt$ to ! upp] p>allel plate4 ,to prev5t we> ! upp] p>ts ( ^! screws are sometimes encas$ 9 tubes--a plan v g5]ally adopt$ 9 ,am]ica4 ,at ! foot ( "o ( ! p>allel plate screws a /ay-piece is fix$ to ! l[] p>allel plate1 :i* =ms a k9d ( r+ r\nd ! screw4 ,?is prev5ts ! p>allel plates f %ift+ ^u ! axis at ! ball & socket4 ,! p>allel plate screws %\ld be )\t any %ake or :at is te*nically t]m$ loss ( "t4 ,!y %\ld move firmly b s(tly4 ,!y %\ld support ! in/rum5t aga9/ ! ball & socket ^u :i* ! :ole rocks to position by _! aid1 b n be screw$ d[n too tightly1 z ?is has a t5d5cy to di/urb ! axis ( ! in/rum5t h[ev] solidly x may be made4 ,mak]s (t5 h in/rum5ts 9 _! h&s = repairs 9 :i* ! p>allel plate screws h be5 deeply ind5t$ into ! l[] p>allel plate1 ) ! c5tre ( ! in/rum5t p]man5tly /ra9$ m or less4 #cgd4--,! ,body-piece4--,! only outw>d "p se5 9 elevation ( ?is is %[n at ,t3 x is %[n 9 section ,t4 ,?is piece c>ries ! limb ( ! in/rum5t ,,ss by a c5tr$ coll> to :i* x is atta*$ by screws4 ,ab\t ! c5tre ( ! body-piece an inset coll> is =m$ to take ! clamp ,,kk :i* bites ^u x4 ,! l[] out] "p ( ! body-piece =ms a conical fitt+ 9 ! boss ( ! upp] p>allel plate ,l4 ,! int]ior is a holl[ conical axis4 ,! body-piece is g5]ally made ( h>d gun-metal4 ,! greate/ possible c>e is requir$ 9 its manufacture1 art4 #ba4 ,! int]ior & ext]ior %\ld be p]fectly conc5tric at e "p4 ,mu* ( ! value ( ! in/rum5t dep5ds ^u ! p]fection ( ! "w 9 ?is piece4 #cge4--;,axis ,coll> ,clamp ,k has be5 already describ$1 art4 #cdi1 & is illu/rat$ 9 ,fig4 #adf1 :i* is tak5 f a !odolite1 s t only specialities 9 relation to ! in/rum5t ,fig4 #aec ne$ be not$4 ,?is clamp surr\nds ! body-piece & clamps x by means ( ! screw ,k %[n on ! left h&4 ,! clamp is connect$ ) ! upp] p>allel plate ?r\gh ! tang5t screw1 ! head ( :i* is %[n at ,p1 s t :5 ! screw ,k is tight5$ ! p>ts ,l & ,t are fix$ toge!r1 except t a sl[ motion c be giv5 to ^! p>ts by ! tang5t screw ,p4 ,by ?is clamp & tang5t arrangem5t ! :ole ( ! upp] "p ( ! in/rum5t is r5d]$ free to revolve1 to br+ ! in/rum5t to be>+ :5 ! clamp is loos5$1 ! f9al adju/m5t be+ secur$ aft] clamp+ by ! tang5t screw4 ,x is ?is "p ( ! in/rum5t :i* is us$ aft] sett+ x up to br+ ! magnetic ne$le true to magnetic nor?1 or o!rwise to direct ! telescope to any e/abli%$ di/ant m>k1 object1 or /> t may be fix$ = ! z]o or o!r index po9t ( ! horizontal circle1 to :i* all read+s f its position are ref]r$4 #cgf4--,! ,c5tral ,v]tical ,axis is %[n only 9 half section at ,z4 ,?is is made uni=mly ( bell-metal1 9 ! =m ( a truncat$ cone1 ext5d+ f ! horizontal circle plate ,s to ! int]ior ( ! socket ,n4 ,its fitt+ surfaces are at ! two ends ( ! cone1 ext5d+ ab\t half an in*1 ! c5tral "p be+ *amb]$ back4 ,at ! upp] "p a p9-piece c5tres ! v]ni] plate1 to :i* x is atta*$ by a wide coll> ) ?ree or f\r screws4 ,a squ>e %\ld] re/s ) weight only j suffici5t to support ! in/rum5t ^u ! body-piece4 ,?is "p has to be s adju/$ t ! axis p]fectly fits & yet moves freely4 ,a squ>e-hole coll> & screw are fix$ on ! l[] end ( ! axis1 j to t\* ! socket ( ! body-piece1 s z to secure ! axis 9 its position :5 ! in/rum5t is lift$4 ,an eye or a hook is fix$ into ! screw at ! l[] end to take ! cord ( ! plummet us$ = fix+ ! in/rum5t ov] a def9ite po9t on ! gr\nd4 ,?is is n %[n 9 ! engrav+4 #cgg4--,! axis ( an ord9>y !odolite is made ! weake/ "p4 ,x is g5]ally consid]$ 9 ! trade "r = x to be s1 z 9 case ( accid5t no o!r "p ( ! v]tical axis sy/em is likely to be d]ang$2 & ?is is ! easie/ "p to replace1 be+1 z x 71 indep5d5t ( o!r fitt+s4 ,:e!r ?is %\ld be tak5 cum grano salis is a "q2 at any rate ) ! axis weak x is n policy to load ! upp] "p ( ! in/rum5t ) metal--:i* 9 places at lea/1 is g5]ally made t5 times z /rong z ! axis--:5 ! in/rum5t has to be c>ri$ ab\t by a p]son ov] 8 %\ld]4 ,"s sugge/ions w be made on ?is po9t h]eaft]4 #cgh4--,! ,horizontal or ,l[] ,plate or ,limb4--,sometimes ! :ole ( ! piece ,,ss is t]m$ ! limb1 b m g5]ally ?is ^w is appli$ to ! divid$ "p only4 ,?is plate is ( brass1 & is atta*$ to ! body-piece by screws4 ,! out] rim1 :i* is some:at triangul> section1 is und]cut ^u ! inn] side ( its l[] surface to support ! clamp-piece1 ! out] edge be+ turn$ to a fillet to take ! clamp :i* is rebat$ to fit x4 ,! upp] surface ( ! rim1 or ! limb prop]1 is turn$ to ! fru/um ( a cone ( ab\t #de4 ,?is "p is cov]$ ) silv]1 :i* is beat5 out to ! conical =m & sold]$ d[n ^u x1 & aft]w>ds turn$ to true =m4 ,! divid+ has be5 discuss$ 9 ! la/ *apt]4 ,! #f-;in* in/rum5t is g5]ally divid$ to #bj1 b sometimes to #cj1 & ! v]ni] reads to #bj or #cj4 ,! figur+ is f #j to #cfj1 "r to left1 tak5 fac+ ! in/rum5t4 #cgi4--,! ,v]ni] ,plate is %[n 9 section "u ,p4 ,! v]ni] f :i* x is nam$ is %[n at ,,vv1 ,fig4 #aee4 ,! v]ni] plate is c>ri$ f ! c5tral axis & =ms ! f\ndation = all ! sup]/ructure4 ,! upp] & l[] plates are left v free :]e !y are br\ght toge!r1 ! v]ni]s be+ g5]ally sprung d[n j to g5tly t\* ! limb4 ,! v]ni] surface is let d[n "s di/ance into its plate = protection4 ,! read+ ( ! v]ni] has be5 discuss$ 9 ! la/ *apt]4 #chj4--;,x may be p>ticul>ly not$1 z already /at$1 t ! c5tral axis & ! body-piece are atta*$ to ! v]ni] & horizontal plates by screws4 ,?is plan might /rike "o z be+ uns\nd3 x is n really s1 ! reason = ?is con/ruction be+ t ^! axes are1 or %\ld be1 ( bell-metal1 & t ?is metal be+ v h>d & brittle x w\ld n be s easily work$1 or s s]viceable z brass = ! limb & v]ni] plate1 nei!r w\ld !re be means ( correct+ errors :i* g5]ally occur bo? 9 ! workman%ip & 9 ! divid+ ( ?is delicate "p4 ,! adju/m5t = fix+ ! limb & v]ni] plate1 te*nically call$ c5tr+1 9 p>ticul> requires consid]able te*nical skill4 ,x is g5]ally p]=m$ by ! divid]1 :o is a specially intellig5t artisan4 ,9 ! au?or's improv$ !odolite1 to be describ$ fur!r on1 ! axis is 9 "o ca/+ ) ! /&>d2 b 9 ?is case ! con/ruction is diff]5t1 ! axis be+ made l>g] & ! :ole body be+ 9 a special gun-metal :i* approa*es bell-metal 9 h>dness4 #cha4--,! v]ni] plate c>ries ! ball nut ( ! tang5t screw1 %[n at ,fig4 #aec;,j4 ,! g5]al arrangem5t may be se5 by ! section1 b is m fully describ$ art4 #cdg4 ,"o ?+ is important 9 ?is screw1 viz41 t x %\ld range )\t /ra9 q p>allel ) ! plates1 s z n to give ! slighte/ t5d5cy to elevate or depress ! edge ^u :i* x is plac$ dur+ motion 9 any "p ( its ?read4 ,! clamp is sometimes plac$ betwe5 ! plates4 #chb4--,! ,compass-box4--,! g5]al con/ruction ( ?is is %[n1 ,fig4 #aee1 ,w4 ,9 ! transit !odolite x is fix$ firmly by screws to ! v]ni] plate & is made to =m a /eady+ piece to ! ,a-frames ,c ,c :i* support ! upp] "p ( ! in/rum5t4 ,= ?is purpose ! compass-box is made z a solid ca/+ 9 brass1 :i* is mu* /iff5$ by ! rais$ /ep :i* =ms ! divid$ circle4 ,f\r solid lugs 9 ! same ca/+ project f ! rim ( ! compass1 & =m /iff5+ pieces betwe5 ! l[] p>ts ( ! ,a-frames2 ^! are secur$ to ! lugs by f\r screws1 "o ( :i* is %[n1 ,fig4 #aec1 at a4 ,! lug screws hold ! :ole sup]/ructure toge!r q indep5d5tly ( ! v]ni] plate1 to :i* x is aft]w>ds firmly fix$4 ,! compass ne$le is lift$ by means ( a mill$ head1 j inside "o ( ! /&>ds1 n %[n4 ,= a g5]al description ( ! compass-box see art4 #ach4 ,! v]ni] plate c>ries two or m v]ni]s4 ,! v]ni]s are read by a pair ( microscopes1 ,fig4 #aee ,,mm plac$ "o on ea* end ( a radial arm ,n hav+ its axis ( motion ^u a l>ge coll> ( ! v]tical axis4 ,by ?is plan1 :5 "o microscope is set to read by ! co9cid5ce ( l9es ^u "o ( ! v]ni]s1 ! o!r microscope on ! o!r arm or arms w be set also 9 l position ov] ! o!r v]ni] or v]ni]s4 ,illu/ration3 ,fig4 #aed4--,v]tical circle ) clipp+ arm ( transit !odolite4 ,! v]ni]s are adju/$ ready = read+ :5 ! telescope is accurately direct$ ^u any object ( :i* x is desir$ to asc]ta9 ! angul> position 9 relation to magnetic nor?1 or a def9ite object4 ,! v]ni] plate also c>ries a _s level at ,o1 ,fig4 #aec1 :i* is adju/able by a pair ( cap/an-head$ screws4 ,illu/ration3 ,fig4 #aee4--;,cross section ( ! upp] "p ( a transit !odolite4 #chc4--,! ,/&>ds or ,a-,frames1 %[n ,c ,c ,fig4 #aee1 are solid ca/+s 9 brass ( ab\t #g in*es 9 height4 ,!y are set up ^u ! v]ni] plate1 to :i* !y are atta*$ by f\r /\t screws1 z also by cross screws to ! compass z /at$4 ,?is r5d]s ! sup]/ructure ( ! transit z firm z may be 9 a built-up con/ruction4 ,^u ! front ( "o ( ! /&>ds a _s level1 ,figs4 #aec1 #aee1 ,i1 is plac$ adju/able by two cap/an screws4 ,?is level1 & "o %[n ,fig4 #aec at #j on ! v]ni] plate are us$ entirely 9 sett+ up ! in/rum5t2 & be+ plac$ at "r angles to ea* o!r1 are a means ( mak+ ! v]ni] plate q level4 ,^u ! inside ( ea* ( ! /&>ds1 at ab\t #b in*es f ! v]ni] plate1 a clip-piece1 ,figs4 #aed1 #aee1 ,p is secur$ by two screws4 ,?is takes ! clipp+ screws1 ,fig4 #aed ,,hh to be describ$4 ,at ! top ( ! /&>ds two ,v's are =m$1 ^u :i* ! transit axis re/s4 ,"o ( ^! is cut out ( ! solid ca/+4 ,! o!r z %[n 9 half section ,fig4 #aee c is =m$ z a p>allel slid+ piece ) ! ,v at ! top plac$ 9 a v]tical slot =m$ 9 ! /&>d4 ,?is slid+ piece has a screw$ /em cont9u$ f its l[] surface t passes ?r\gh a v]tical hole at ! top ( ! ,a-frame1 :i* is =m$ "h z a cross-piece4 ,^u ! screw two cap/an nuts are plac$1 "o on ea* side ( ! cross-piece1 ,fig4 #aee xx2 ^! p]mit ! adju/m5t ( ?is 9 height s z to get ! transit axis p]fectly horizontal :5 ! v]tical axis is p]fectly p]p5dicul> to ! horizon4 ,! slid+ piece is cov]$ by plates back & front to r5d] x firm 9 its position4 ,! transit axis 9 practice is adju/$ ) a /rid+ level :i* w be describ$ pres5tly4 ,) ! au?or's !odolites f #f in*es d[nw>ds ! old-fa%ion$ adju/m5t to "o upright = levell+ ! horizontal axis has be5 disp5s$ ) = _m ye>s1 & is only fitt$ if specially ord]$1 z x has be5 f\nd to be a frequ5t s\rce ( error4 ,long exp]i5ce has prov$ beyond d\bt t ! few] adju/m5ts !re are1 & ! m p>ts t c be fa%ion$ f ! solid metal correctly1 ! long] w ! in/rum5t keep 9 adju/m5t4 ,%\ld !re ev] be any we> on ei!r ( ! ,v's a few /rokes ) a piece ( v f9e em]y pap] ^u ! opposite "o w put x "r 9 half ! "t t x c\ld be correct$ ) ! old-fa%ion$ adju/able ,v1 & no am\nt ( vibration c alt] x z ) ! adju/+ screws4 ,an axis cov] cap bb is plac$ on ! top ( ea* /&>d4 ,! cap is screw$ d[n at "o end ) a cut screw & coll>4 ,! screw is us$ = adju/m5t to g5tle pressure on ! axis4 ,! second screw is a mill$ head ,,ee4 ,"u ?is screw ! cap is slott$ out to "o side1 & turns on ! cut screw z an axis to op5 ! cap )\t remov+ its mill$-head screw1 s t ! telescope c be lift$ out to turn its face to ! opposite side ( ! in/rum5t4 ,9 ! "u side ( ! c5tre ( ! cap a cell is bor$ out1 into :i* a small cork is fitt$1 :i* produces1 :5 ! cap is clamp$ d[n1 a s(t ela/ic pressure on ! axis4 #chd4--,! ,transit ,axis :i* supports ! telescope re/s at its ends ^u two trunnions1 ,figs4 #aed1 #aee ,,aa1 te*nically call$ pivots1 9 ! ,v's ( ! /&>ds already describ$4 ,! pivots are turn$ z true z possible1 & aft]w>ds gr\nd to exactly equal size 9 a coll>1 s t !y may be rev]s$ end = end 9 _! be>+s )\t *ang+ ! l9e> direction ( ! transit axis1 except by ! little diff]5ce ( pressure t "o end ( ! axis imposes by ! weight ( ! v]tical circle & its atta*m5ts be+ ecc5tric4 ,9 l>g] in/rum5ts ?is diff]5ce ( weight is c\nt]balanc$1 z %[n 9 dott$ l9es at p1 ,fig4 #aee4 ,! c5tre ( ! transit axis is =m$ into a coll> e ( ab\t #a in*es 9 wid?1 :i* exactly fits ! out] tube ( ! telescope1 & to :i* x is fix$ ) s(t sold]4 ,! coll> is directly connect$ ) & supports a flange f4 ,^u ?is flange ! v]tical circle ,,ff is fix$ by ?ree or f\r screws4 #che4--;,9 front ( ! v]tical circle a flang$ coll>-piece c>ries ! v]tical v]ni] frame ,,vv1 ,fig4 #aed1 c5tr$ ^u x4 ,! v]ni] frame is atta*$ by ?ree screws to ! clipp+ arm to be describ$1 & 9 front ( ?is ! v]tical microscope arms are c5tr$4 ,^! c>ry two read]s ,u1 ,fig4 #aee1 exactly simil> to ^? :i* read ^u ! horizontal circle1 & !y are simil>ly c5tr$1 s t by sett+ "o1 ! o!r is set at exactly #ahj f x4 ,9 front ( ! c5tre ( ! microscope arms on ! transit axis1 an axis coll>-piece j is atta*$ by ?ree screws cut directly into ! axis4 ,?is coll> & "o at ! o!r end ( ! axis ,a1 turn$ out ( ! solid1 are nicely fitt$ to ! op5+ betwe5 ! /&>ds to prev5t lat]al displacem5t ( ! axis4 #chf4--,! ,clips4--,! clipp+ arm1 :i* is c5tr$ on ! transit axis & atta*$ to ! v]ni]s1 is %[n ,fig4 #aed ,,bb,b4 ,x is fitt$ to move freely on its axis at ,a1 s z to p]mit unre/ra9$ motion ( ! telescope4 ,a mill$-head clamp+ screw ) clamp1 ,fig4 #aee1 ,k1 & ! same p>tly cut away to %[ ! slot 9 :i* x works1 are %[n at ,k ,fig4 #aed4 ,?is is us$ to fix ! v]ni]s /ation>y on ! circle1 except = ! adju/m5t by ! tang5t screw ,g1 :i* has its coll> atta*$ to ! clipp+ arm1 & its ball nut atta*$ to ! clamp at ,d :5 us+ ! telescope = levell+4 ,?is clamp & tang5t sets ! v]ni] to z]o on ! circle4 ,x is also us$ 9 sett+ ! telescope be=e angles ( altitude or depression c be measur$4 ,! clipp+ screws ,,hh are us$ to br+ ! pr9cipal bubble ,b1 ,fig4 #aec1 on ! top ( ! telescope to ! c5tre ( its run aft] ! v]ni]s h be5 br\ght to z]o by means ( ! clamp & tang5t screws4 ,! clipp+ screws hold ! clips1 ,fig4 #aee1 ,p or ,p to ! "o /&>d or ! o!r4 ,! :ole ( ! v]tical adju/m5t is exactly equival5t to t already describ$ = ! horizontal motion1 except t x is plac$ 9 ! v]tical plane4 #chg4--,! ,v]tical ,circle1 ,figs4 #aed1 #aee1 ,f is c>ri$ by f\r arms f a c5tral boss atta*$ firmly by screws to ! transit axis4 ,x is groov$ at ! edge to take ! clamp-piece4 ,! silv] is inlaid 9 ?is circle 9 ! mann] %[n ,fig4 #aag4 ,! v]ni] is read ^u ! circle on ! plan %[n ,fig4 #abg4 ,! circle is divid$ g5]ally to half degrees or #bj1 & is figur$ #j to ! horizontal ) #ij upw>ds & d[nw>ds4 ,! z]o l9es are made directly co9cid5t ) ! optical axis ( ! telescope :5 x is level4 ,! v]ni] reads to half m9utes or #bj1 9 ei!r direction1 ! ris+ arc above ! level datum be+ consid]$ z plus1 ! fall+ arc z m9us4 #chh4--,on ! out] edge ( ! circle or at ! back a scale ( diff]5ce ( hypot5use & base reads to a l9e on a fiducial edge ^u a "p ( ! clip ,,bb1 ,fig4 #aed1 at ,n4 ,?is scale is calculat$ = decimal quantities1 & gives ! p]c5tage numb] ( l9ks1 feet1 or metres to be d$uct$ f ! *a9 measurem5ts ^u ! gr\nd l9e to give ! horizontal di/ance correspond+ to ! angle ( incl9ation at :i* ! telescope is set = obs]vation4 #chi4--,! ,telescope1 ,fig4 #aec1 ,,dd has be5 describ$ art4 #id4 ,its g5]al con/ruction is also %[n 9 p>tial sections 9 ! figure4 ,its body tube passes ?r\gh ! transit axis 9 :i* x is sold]$4 #cij4--,! ,pr9cipal ,level ,tube is g5]ally m\nt$ on ! telescope ^u two /iff screws :i* rise f plates atta*$ to ! telescope body by pairs ( screws4 ,ea* level screw has a pair ( cap/an nuts4 ,! level is m\nt$ 9 a brass tube ) /op-pieces at ! ends1 ea* ( :i* c>ries a t5on ) a hole 9 its c5tre ?r\gh :i* ! level screw passes to be clamp$ top & bottom by ! cap/an nuts4 ,^! nuts give adju/m5t to ! level1 s t ! c5tre ( its inn] upp] surface may be plac$ p>allel ) ! optical axis ( ! telescope4 ,illu/ration3 ,fig4 #aef4--,/anley's new model ( #d-screw transit !odolite4 #cia4--,until #ahih ! au?or 0 unwill+ to attempt to remodel ! old =m ( transit !odolite1 believ+ ! #d-screw adju/m5t w\ld soon become a me?od ( ! pa/1 b z a small dem& cont9u$ f ! ,colonies & ,unit$ ,/ates = ?is =m ( in/rum5t he felt b\nd to make x ( m solid con/ruction to br+ x some:at up to date4 ,! illu/ration %[n1 ,fig4 #aef1 is ( an in/rum5t1 foll[+ 9 con/ruction ! transit !odolite already describ$ 9 _m details1 ! m>k$ exception be+ t ! /&>ds are 9 "o ca/+ ) ! compass-box & axis1 ^! be+ entirely %ap$ out 9 ! solid metal4 ,! upp] p>allel plate is ( special design1 be+ f> /rong]1 yet light]1 & gives a mu* long] be>+ to ! levell+ screws4 ,! l[] p>allel plate is also %ap$ ) ?ree feet s t ! in/rum5t may be set up )\t its /& :5 requir$4 ,x has also mod]n spr+ tang5t adju/m5ts ) cov]$ screws4 ,! limb is cov]$1 & ! read]s are jo9t$ across ! axis to turn up )\t sep>ation4 ,x has a float+ alum9ium compass read by a microscope1 s t ! in/rum5t1 except 9 ! f\r-screw arrangem5t = sett+ up1 embraces _m mod]n improvem5ts =m]ly appli$ only to special high-class !odolites4 ,! improv$ con/ruction p]mits great] rigidity ) fifte5 p] c5t4 less weight4 ,illu/ration3 ,fig4 #aeg4--,! plummet4 ,illu/ration3 ,fig4 #aeh4--;,gurley's plummet4 ,illu/ration3 ,fig4 #aei4--,loop4 ,illu/ration3 ,fig4 #afj4--,r+ plummet1 ,%ortt's ,pat5t4 ,( lat] ye>s1 h[ev]1 ! dem& = f\r-screw levell+ in/rum5ts has be5 ma9ta9$1 especially f ,canada1 ow+ to ! influ5ce ( ! ,am]ican s*ool ( tea*+1 & 9 consequ5ce all ! au?or's improv$ !odolites are fitt$ ) ei!r ?ree- or f\r-screw levell+1 :i*ev] is desir$4 ,x is a /range fact1 h[ev]1 t ) all ! ,am]ican mak]s1 al?\gh !y li/ all _! ord9>y in/rum5ts ) f\r-screw levell+1 _! ref9$ ones1 :i* !y t]m precision in/rum5ts1 w be f\nd ) ?ree-screw levell+4 #cib4--;,deta*$ p>ts ( a ,!odolite4--,! ,plummet suppli$ ) ! !odolite is made to hang f a hook "u ! c5tre ( ! axis ( ! in/rum5t1 ! cord1 :i* is ( s(t silk1 be+ loop$ or knott$ to hold 9 ! hook4 ,! l[] end ( ! plummet is br\ght to a po9t :i*1 :5 9 use1 falls directly "u ! v]tical c5tre ( ! in/rum5t ^u ! surface ( ! gr\nd4 ,9 ,fig4 #aeg ! screw & plummet are %[n deta*$4 ,! cord ,c is atta*$ to ! plummet by pass+ x ?r\gh a hole 9 ! mill$-head screw ,s at ! top ( ! plummet1 & by mak+ a knot ,k 9 ! cord4 ,fig4 #afj %[s an +5i\s r+ plummet rec5tly inv5t$ & pat5t$ by ,mr4 ,w4 ,h4 ,%ortt1 ,a4,m4 ,i4,c4,e4 ,! *ief object 0 ! production ( a plumb bob ^: plumb+ po9t %\ld be situat$ at1 or v close to1 ! c5tre ( oscillation 9 ord] t ! position ( ! po9t might be unaffect$ by oscillation ( ! bob itself1 ap>t f any sw+ :i* x might h ab\t ! po9t ( susp5sion ( ! /r+4 ,a fur!r object 0 to %ape ! bob s t a p]son hold+ ! /r+1 or /&+ close to x :5 atta*$ to an in/rum5t & look+ d[n at ! bob1 %\ld be able to see readily ! exact position ( ! plumb+ po9t4 ,^! objects h be5 atta9$ by mak+ ! bob 9 ! =m ( a r+1 s t ! c5tre ( oscillation :i* lies 9 ! c5tre ( ! r+ c itself be us$ z ! plumb+ po9t1 s9ce x c be readily se5 & indicat$ by ! extremities ( po9t]s project+ t[>ds ! c5tre f ! inside ( ! r+4 ,a great advantage ( ?is bob is t :5 plumb+ on to a flat surface x does n fall ov] :5 l[]$1 b may be all[$ to actually lie on ! surface :ile ! position ( ! po9t is be+ m>k$4 ,also x c be/ be /eadi$ by l[]+ into contact ) ! gr\nd & rais+ aga94 ,! plumb+ po9t]s are l>gely protect$ f injury :5 ! bob is 9 use1 & :5 n 9 use ! susp5sion /r+ c be w\nd diametrically across ! bob1 9 recesses provid$ = ! purpose1 ?us completely protect+ ! po9ts4 #cic4--,! ,loop4--,x is some:at difficult 9 ! ord9>y way to adju/ ! plummet to ! /ation m>k on ! gr\nd or on a peg4 ,! cord is sometimes plac$ 9 an ivory runn] fix$ to ! top ( ! cord1 ,fig4 #aei4 ,?is gives friction on ! cord & p]mits ext5sion & contraction ( ! loop = adju/m5t4 ,:]e ! plummet has to be susp5d$ f ! in/rum5t z well z f a hook inside ! /&1 :i* is sometimes conv5i5t1 x is bett] to h ! runn] cut out on "o side4 ,?is p]mits easy *ange & x is j z firm4 #cid4--,messrs4 ,gurley ,bros4 ( ,troy1 ,n4,y41 h a good plan = %ort5+ ! plummet l9e4 ,?is is effect$ by mak+ a reel 9 ! plummet1 :i* is w\nd by a mill$ head at ! top ( x1 ,fig4 #aeh4 #cie4--,screw-driv]s1 ,tommy ,p9s1 etc4--,a screw-driv] & a tommy p91 ! la/ to turn ! cap/an heads1 are plac$ 9 ! case ) ! !odolite4 ,two screw-driv]s ) prop] h&les are bett]1 z !re are small & l>ge screws4 ,a camel-hair bru% to du/ ! in/rum5t1 a piece ( wa%-lea!r1 a little vasel9e1 & a small bottle ( good wat* oil are also v useful4 ,^! little ref9em5ts are g5]ally kept out to keep d[n ! price ( ! in/rum5t4 #cif4--;,additional ,p>ts1 & ,v>iations 9 ,!odolites4--,illum9at$ ,axis4--#d1 #e & #f-;in* transits sometimes1 & l>g] in/rum5ts always1 h ! transit axis bor$ on "o side ?r\gh to ! int]ior ( ! telescope1 z %[n on ,fig4 #aee4 ,?r\gh ! hole a small p5cil ( light is s5t by a lamp l ) a plano-convex l5s front1 to a l5s plac$ 9 ! end ( ! axis4 ,?is1 by a slight adju/m5t ( ! lamp on its /&1 focusses ! light ^u a small mirror plac$ )9 ! telescope1 :i* reflects its rays to ! diaphragm4 ,! lamp gives a fa9t light only suffici5t to di/+ui% ! webs = night & und]gr\nd obs]vations4 ,! mirror is ab\t #a_/aj in* 9 diamet]1 & is g5]ally m\nt$ ^u a mill$ head screw tapp$ into ! trunnion b& ( ! telescope m4 ,! po9t ( ! screw is ext5d$ z a ?9 /em into ! axis ( ! telescope1 :]e ! mirror is held by x4 ,?is arrangem5t p]mits ! mirror1 :i* is g5]ally made ( silv]1 b is mu* bett] ( plat9o-iridium1 to be remov$ = clean+4 ,! lamp is m\nt$ ^u a wood5 /& w c>ri$ ^u a slide n or ^u two brass p9s direct to ! ,a-frame4 ,! wood is employ$ 9 ?is case to cut (f conduction ( heat to ! ne> /&>d f ! lamp z mu* z possible to prev5t di/urbance ( ! axis f expansion by heat+4 ,! /& may be remov$ :5 ! lamp is n requir$ & plac$ 9 ! case4 ,9 l>ge !odolites a pair ( lamps are us$1 t ! transv]se axis may n be heat$ m on "o side ?an on ! o!r4 #cig4--,! ,lamp1 :i* is f\nd s conv5i5t = br++ a /> or di/ant light to read ) ! webs1 becomes difficult to use :5 ! object is v fa9t1 z ! light ?r[n into ! telescope by ! lamp takes (f ! effect ( blackness ( ! night sky or t ( total d>kness4 ,?is becomes important 9 tak+ obs]vations ( small />s1 z = in/ance1 ! circumpol> />s ( ! s\!rn hemisph]e4 ,9 "s !odolites1 made fir/ = ! ,sydney ,gov]nm5t1 ! au?or plac$ a v small lamp to ?r[ light ^u ! face ( ! webs only1 mak+ ^! appe> z light l9es on a black gr\nd4 ,! reflect+ eye-piece1 ,fig4 #bj1 w be f\nd to answ] v well1 & ?is is a simple1 inexp5sive contrivance4 ,any am\nt ( illum9ation desir$ may be ?r[n on ! front ( ! diaphragm1 accord+ to ! di/ance at :i* ! light is held f ! eye-piece3 g5]ally a v fa9t light only is requir$4 #cih4--,! au?or has illum9at$ ! webs front & back by means ( a v small 7"o-qu>t] c&le p[]7 inc&esc5t lamp1 :i* is *>g$ by a portable batt]y1 or a second>y batt]y :]e a dynamo is at h& = *>g+ x1 & = c\ntries :]e ^! _c be r5ew$ or :]e ! extremes ( temp]ature are too great = _! use1 he has devis$ a small h& dynamo = g5]at+ ! curr5t & a rheo/at = controll+ ! p[] ( ! lamp1 s t resi/ance may be employ$ to r$uce ! light to ! fa9te/ possible glimm]4 ,! electric lamp is f> sup]ior to ! old oil lamp & safe to use 9 gase\s m9es2 x is f> clean]1 does n give out a ti! ( ! heat1 & may be remov$ f its socket & us$ 9 ! h& = read+ ! v]ni]s 9 a bad light4 ,all ! au?or's mod]n in/rum5ts t are requir$ ) illum9at$ axis are n[ fitt$ ) electric lamps4 ,illu/ration3 ,fig4 #afa4--,tr\gh ne$le = transit !odolite4 #cii4--;,a ,tr\gh or ,long ,compass1 us$ 9 place ( ,circul> ,compass4--,a long compass1 ,fig4 #cb1 p4 #gd1 is (t5 appli$ to a !odolite1 ei!r ^u ! top ( ! telescope1 or m g5]ally & conv5i5tly = read+ "u ! limb4 ,9 ?is la/ case ! tr\gh ne$le is a sep>ate piece1 :i* is only atta*$ to ! limb ( ! !odolite by means ( loop slides or bayonet fitt+s "u ! limb1 :5 requir$ to take a be>+4 ,! engrav+ ,fig4 #afa %[s ! long compass ) bayonet fitt+s4 ,!re are f\r slots1 two ( :i* are %[n ,,ss1 :i* fit 9 "u ! heads ( r\nd-head$1 %\ld]$ screws4 ,! au?or has some:at modifi$ ?is patt]n rec5tly by mak+ x slide into grooves4 ,! tr\gh ne$le is g5]ally made #e or #f in*es long1 & reads into a %ort scale ( ab\t #aj at ea* end4 ,! divisions are be/ plac$ ^u slid+ fitt+s1 s t !y may be adju/$ by f\r screws f ! outside ( ! box--screws %[n ,,aa4 ,?is enables ! ne$le to be adju/$ to its own axis1 & also to ! #j read+ ( ! horizontal limb ( ! !odolite4 ,a slide lift to ! ne$le is %[n at ,l4 ,:5 ! same =m ( compass is us$ ^u l>ge in/rum5ts a read] is plac$ at ea* end ( ! ne$le4 ,illu/ration3 ,figs4 #afb1 #afc1 #afd4--,/rid+ level4 #djj4--,/rid+ ,level4--,= ! adju/m5t ( ! transv]se axis ( a !odolite a v s5sitive _s level is us$4 ,?is is m\nt$ ^u a b$1 :i* may be =m$ ( brass tub+1 f ! two ends ( :i* adju/able legs desc5d1 ! ends ( :i* are =k$1 ! holl[s ( ! =ks =m+ ,v be>+ surfaces4 ,! ,v's re/ ^u ! pivot ( ! axis4 ,by rev]s+ ! /rid+ level on ! pivots ! transv]se axis ( ! telescope1 or transit axis1 c be readily adju/$ truly p]p5dicul> to ! v]tical axis4 ,9 ! con/ruction ( ! /rid+ level1 %[n 9 detail 9 ,fig4 #afb1 ! two /rid+ /&>ds ,,ss are c>ri$ d[n f ! ends ( ! cas+ tube ,b ( ! _s level4 ,^! are adju/able3 "o1 ,fig4 #afd1 by rais+ or l[]+ ! end ( ! level tube by ! cap/an screws ,,cc1 & ! o!r1 ,fig4 #afc1 by a lat]al adju/m5t ( ! cap/an screws ,,pp t act ^u ! /ud ,s1 :i* is fix$ ^u an arm c5tr$ ^u ! axis ( ! tube4 ,?is connection is %[n by dott$ l9es4 ,by ^! two motions ! /&>ds are br\ght to p]fect p>allelism ) ea* o!r = _! be>+ surfaces & adju/m5t ( ! cr[n ( ! bubble tube4 ,illu/ration3 ,fig4 #afe4--,wallis' %ift+ c5tre = !odolites4 #dja4--;,adju/m5t ( ! ,axis = ,sett+ x up ov] a ,po9t4--,e surveyor exp]i5ces an am\nt ( difficulty 9 gett+ ! plummet to fall f ! axis ( ! in/rum5t exactly ov] a po9t ^u ! gr\nd1 or a m>k ^u a rock1 or /ill m s ^u a po9t 9 /reet pav+ 9 a t[n1 :i* is necess>y = exact "w4 ,x is easily set ne> ! po9t1 t is1 )9 half an in* or s1 by press+ or %ift+ ! legs2 b ! difficulty increases z ! exact po9t is approa*$1 s t ! sett+ has g5]ally to be left at a c]ta9 /ate ( approximation4 ,!re are a great numb] ( s*emes 9 use = mov+ ! axis by adju/m5t ( ! in/rum5t ! small quantity requir$1 )\t di/urb+ ! legs ( ! tripod :5 !y are firmly set d[n ne>ly correct to position4 ,"o ( ^! w\ld no d\bt be g5]ally appli$ to ! !odolite1 except = ! reason t e means yet devis$ adds to its weight1 & also to ! exp5se ( ! in/rum5t4 ,a mod]ately simple plan1 :i* is especially adapt$ to ! p>allel plate adju/m5t1 is to make ! l[] flange ( ! !odolite1 ^u :i* x /&s :5 set d[n (f its tripod1 some:at l>g] & ?9n]4 ,?is flange1 in/ead ( be+ screw$ directly d[n ^u ! tripod head1 is plac$ betwe5 two r+ plates1 :i* are clamp$ toge!r :5 ! !odolite is set 9 position4 ,! l>ge hole 9 ! c5tre ( ! r+ p]mits movem5t ( ! l[] plate ( ab\t #a in*4 ,fig4 #afe is an arrangem5t ( ?is k9d by ,mr4 ,j4 ,wallis4 ,?is is made entirely indep5d5t ( ! !odolite1 & may be us$ or n z requir$4 ,i is a screw t corresponds ) ! head ( ! tripod :i* takes ! !odolite2 ,t simil> female screw to take ! tripod head :5 ! %ift+ c5tre is us$2 ,,cc a box =m$ by screw+ two tray-pieces firmly toge!r2 ,s clamp+ flange2 ,,hh clamp screw$ into ! top ( box ,c4 ,?is has two h&les by :i* ! screw is mov$ to clamp :5 ! in/rum5t is 9 position4 ,! weight ( ?is additional "p is ab\t #c lbs4 ,! arrangem5t is p>ticul>ly adapt$ to p>allel plate adju/m5ts4 #djb4--;,9 an ,am]ican plan ( a transit by ,messrs4 ,hell] ,brightly1 ! flange is lift$ by ! p>allel plate screws1 :i* tight5 x at ! same "t4#ah ,messrs4 ,tr\ghton ,simms h a plan ( %ift+ ! axis by means ( a pair ( ecc5tric plates1 :i* c>ry ! in/rum5t 9 two directions ne>ly at "r angles to ea* o!r4 ,by ?is arrangem5t an am\nt ( lev]age is secur$ :i* produces an easi] motion ?an t ( %ift+ ! weight ( ! in/rum5t on ! plans m5tion$ above4 ,! au?or's s*emes w be describ$ z a "p ( 8 new !odolites a few pages on4 #djc4--,/adia ,webs or ,l9es us$ = tak+ subt5se angles by ! telescope = measur+ di/ances1 :i* are frequ5tly appli$ to !odolites1 w be fully describ$1 ,*apt] ,,xii41 9 treat+ ( subt5se in/rum5ts g5]ally4 #djd4--,sol> ,atta*m5t to a ,!odolite4--,?is appliance is an adaptation to ! !odolite ( ! sol> compass ( ,w4 ,a4 ,burt1 ( ,mi*igan1 :i* 0 made to replace ! magnetic compass 9 det]m9+ a true m]idian1 or nor? & s\? l9e1 by obs]vation ( ! sun only4 ,x 0 br\ght into g5]al use 9 ! surveys ( ! ,unit$ ,/ates public l&s4 ,! sol> compass consi/s ma9ly ( ?ree arcs ( circles by :i* ! latitude ( a place1 ! decl9ation ( ! sun1 & ! h\r ( ! day c be set (f4 ,9 ! sol> atta*m5t to ! !odolite ! latitude arc is f\nd unnecess>y1 z ?is is =m$ by ! v]tical arc ( ! !odolite2 !re=e ! h\r & decl9ation arcs ne$ only be describ$4 ,illu/ration3 ,fig4 #aff4--;,burt's sol> atta*m5t to a !odolite4 #dje4--,! ,h\r ,circle1 ,fig4 #aff1 ,h is fix$ ^u ! c5tre ( ! telescope ^u a socket axis ,s1 :i* is plac$ p]p5dicul>ly to ! optical axis & to ! transv]se axes or pivots ( ! !odolite4 ,?is circle is divid$ to read five m9utes ( "t1 & is figur$ ,i to ,,xii twice1 or ,i to ,,xxiv1 ! index be+ a f9e l9e c>ri$ d[n on a plate f ! l[] arm ( ! decl9ation arc1 :i* is fix$ to ! socket ,s4 ,! h\r circle1 :5 set to any read+1 may be clamp$ to ?is position by means ( ! mill$ head plac$ ov] ! socket ,m4 #djf4--,! ,decl9ation ,arc is ( #e in*es radius1 divid$ to read on ! same plane ) a v]ni] ,v to s+le m9utes ( arc4 ,! v]ni] arm is fix$ by a clamp at ,c1 :i* c>ries tang5t adju/m5t ,t4 ,at ! back ( ! v]ni] arm two spur-pieces are c>ri$ out directly f x1 ,l & ,i4 ,^! are blocks ( metal ab\t #a by #a by in*es1 :i* c>ry ea* a l5s ( a focus ,l to ,i1 & a silv] plate to be pres5tly describ$1 ^u :i* ! sun's image is receiv$ 9 "o direction or ! o!r4 ,illu/ration3 ,fig4 #afg4--;,image plate ( sol> atta*m5t4 #djg4--,! ,image ,plate1 ,fig4 #afg1 is m>k$ ) two sets ( l9es int]sect+ ea* o!r at "r angles4 ,! l9es bb are t]m$ h\r l9es1 ! l9es cc equatorial l9es2 ^! l9es hav+ ref]5ce respectively to ! h\r ( ! day & ! position ( ! sun 9 relation to ! equator4 ,! int]vals betwe5 ! l9es bb & cc are j suffici5t to include ! circul> image ( ! sun =m$ by ! sol> l5s on ! opposite end ( ! v]ni] arm4 ,! axes ( ! sol> l5ses & correspond+ image plates are plac$ p>allel ) ea* o!r1 & ) ! direction ( ! v]ni] arm4 ,bel[ ! l[] l9e c ?ree o!r l9es are cut at #e m9utes ap>t4 ,^! are useful = mak+ all[ance = refraction4 ,! foll[+ description = ! use ( ! in/rum5t is p>tly extract$ f ,messrs4 ,gurley's manual4 #djh4--,:5 ! in/rum5t is made p]fectly horizontal1 ! equatorial l9es & ! opposite l5ses be+ accurately adju/$ to ea* o!r by a previ\s op]ation1 ! sun's position 9 ! heav5s ) ref]5ce to ! horizon w be def9$ ) precision4 ,suppose ! obs]vation to be made at ! "t ( "o ( ! equ9oxes2 ! arm ,r set at z]o on ! decl9ation arc ,v2 & ! pol> axis is plac$ exactly p>allel to ! axis ( ! e>?4 ,!n ! motion ( ! arm ,r1 if revolv$ on ! pol> axis ar\nd ! h\r circle ,h1 w exactly correspond ) ! motion ( ! sun 9 ! heav5s on ! giv5 day & at ! place ( obs]vation2 s t if ! sun's image be br\ght betwe5 ! l9es cc on ! image plate 9 ! morn+ x w cont9ue 9 ! same position1 pass+ nei!r above nor bel[ ! l9es z ! arm is made to revolve 9 foll[+ ! motion ( ! sun ab\t ! e>?4 #dji4--;,9 ! morn+ z ! sun rises f ! horizon1 ! arm ,r w be 9 a position ne>ly at "r angles to t %[n 9 ! illu/ration1 ! l5s be+ turn$ t[>ds ! sun & ! silv] plate1 on :i* 8 image is ?r[n1 directly opposite4 ,z ! sun asc5ds1 ! arm mu/ be mov$ ar\nd1 until :5 he has rea*$ ! m]idian1 ! graduat$ side ( ! decl9ation arc w indicate ,,xii on ! h\r circle2 & ! arm ,r1 ! decl9ation arc ,v1 & ! latitude arc1 t is ! v]tical arc ( ! !odolite1 w be 9 ! same plane4 ,z ! sun decl9es f ! m]idian ! arm ,r mu/ be mov$ 9 ! same direction1 until at sunset its position w be ! exact rev]se ( t x occupi$ 9 ! morn+4 #daj4--;,all[ance = ,decl9ation4--,let u n[ suppose ! obs]vation made :5 ! sun has pass$ ! equ9octial po9t1 & :5 8 position is affect$ by decl9ation4 ,!n1 by ref]r+ to ! ,nautical ,almanac & sett+ (f on ! arc 8 decl9ation = ! giv5 day & h\r1 we are /ill able to det]m9e 8 position ) ! same c]ta9ty z if he rema9$ on ! equator4 ,:5 ! sun's decl9ation is s\?1 t is1 f ! #bbnd ( ,septemb] to ! #bj? ( ,m>* 9 ea* ye>1 ! arc ,r is turn$ t[>ds ! plates ( ! in/rum5t 9 ! opposite position to t %[n 9 ! engrav+1 us+ ! sol> l5s at ,i1 ) ! silv] plate opposite at ,l4 ,! rema9d] ( ! ye> ! arc is turn$ f ! plates1 & ! l5s at ,l & plates at ,i are employ$ 9 ! position %[n 9 ! figure4 #daa4--,:5 ! sol> compass is accurately adju/$ & its plates made p]fectly horizontal1 ! latitudes ( ! place & ! decl9ation ( ! sun = ! giv5 day & h\r be+ also set (f on _! respective arcs1 ! image ( ! sun _c be br\ght betwe5 ! equatorial l9es until ! pol> axis is plac$ 9 ! plane ( ! m]idian ( ! place1 or 9 a position p>allel to ! axis ( ! e>?4 ,! slighte/ deviation f ?is position w cause ! image to pass above or bel[ ! l9es & ?us discov] ! error4 #dab4--,we ?us1 f ! position ( ! sun 9 ! sol> sy/em1 obta9 a c]ta9 direction absolutely un*angeable f :i* to run our l9es & measure ! horizontal angles requir$4 ,! transit !odolite w1 )\t ! sol> compass1 p]=m ! same functions2 b by means ( ?is in/rum5t ! calculation = position is mu* m simple4 #dac4--,photographic ,app>atus 9 ,connection ) ! ,!odolite4--,! application ( photographic app>atus z an accessory to survey+ in/rum5ts has be5 tri$ t5tatively = _m ye>s4 ,a practical introduction to ! subject 0 fir/ giv5 by ,m4 ,lauss$at 9 a pap] publi%$ 9 ! ,comptes ,r5dus de l',academie des ,sci5ces1 #ahei4 ,! subject has s9ce be5 well /udi$ by _m writ]s1 & is writt5 up ext5sively by ,dr4 ,e4 ,deville1 ,,ll4,d41 ,surveyor-,g5]al ( ,canada1 9 a "w entitl$ ,photographic ,survey+1 publi%$ 9 ,ottawa1 to :i* we mu/ ref] ! read] = full discussion ( ! subject4 ,9 ,engl&1 ,mr4 ,j4 ,bridges ,lee has inv5t$ a v suitable cam]a 9 :i* a negative glass photograph ( #d #c in*es is tak51 ) an axis l9e f ! %ad[ ( a hair p]man5tly photograph$ co9cid5t ) ! axis to ! telescope z x appe>s to view4 ,at ! same "t degrees & subdivisions are tak5 on ! photograph to "r & left ( ! axial l9e4 ,! edge ( ! magnetic circle is also photograph$ ^u ! plate1 indicat+ cle>ly ! be>+ ( ! /ation tak5 by ! axis l9e4 ,! :ole ( ^! op]ations are p]=m$ at once 9 a p]fect mann]4 #dad4--,mr4 ,j4 ,bridges ,lee's photo-!odolite 0 made 9 excell5t workman%ip by ,messrs4 ,tr\ghton ,simms4 ,! inv5tor has publi%$ a pap] on ! subject1 to be _h ( ! ,society ( ,eng9e]s1 ,we/m9/]4 ,illu/ration3 ,fig4 #afh4--,light cam]a ^u ! telescope ( a !odolite4 ,at ! pres5t "t a cam]a is v commonly tak5 by a civil eng9e] = prospect+ 9 new c\ntries1--a conv5i5t =m ( ?is w be discuss$ at ne>ly ! end ( ?is "w--b x is n g5]ally held t photography w ev] (f] a means ( exp$iti\s survey+1 except possibly 9 v m\nta9\s c\ntries :]e ! necess>y /ations = obs]vation become difficult ( approa* & ( cle> def9ition4 ,! objections to ! m g5]al adoption ( photography are1 o!rwise1 t ! processes are 9 degree t$i\s1 & require special skill 9 manipulation1 & t ! app>atus is heavy & exp5sive ) s5sitive glass plates = use ) x4 #dae4--,!re are _m cases1 no d\bt1 :]e a photograph w\ld be valuable = ! exact def9ition ( a /ation4 ,to meet ?is case ! au?or has made a small light cam]a1 %[n ,fig4 #afh1 giv+ photographs #b #b in*es only1 ) axis l9e f %ad[ ( a po9t4 ,! cam]a to be plac$ :5 requir$ ^u ! telescope ( a !odolite = special cases4 ,he has lately us$ 8 pat5t slide = ?is cam]a t c>ries films :i* w be fur!r describ$ at ! end ( ?is "w4 ,! films are unbreakable1 & rema9 s5sitive _m ye>s if kept dry4 ,! weight ( ?is cam]a ) its d\ble slides & #ajj films is ab\t #a lb4 ,!re is ample room = x 9 ! ord9>y !odolite case4 ,,footnotes3 #ae ,digges's ,pantometria1 see p4 #b4 #af ,g>d9]'s ,practical ,survey+1 p4 #ei1 #agcg4 #ag ,adam's ,geometrical ,essays1 pp4 #bag-bbi1 #ahjc4 #ah ,civil ,eng9e]s' ,pocket-,book1 by ,j4 ,c4 ,trautw9e1 ,c4,e4 ,,*apt] ,,viii4 ,,specialities ,,9 ,,mod]n ,,& ,,improv$ ,,=ms ,,( ,,transit ,,!odolites ,,= ,,survey+--,,railway ,,"w--,,explor+4 #daf4--,! description giv5 9 ! la/ *apt] ( a #f-;in* transit !odolite gives all p>ticul>s ( ! orig9al ,old ,engli% =m1 :i* 9 a g5]al way comprises ! con/ructive pr9ciples ( all o!rs4 ,:5 we consid] mod]n in/rum5ts ! details are f\nd to v>y greatly1 b mo/ p>ticul>ly 9 ! direction ( unit+ 9 solid ca/+s _m p>ts t may be %ap$ out by ma*9]y 9 a mann] impossible by h&-"w1 :i* avoids ! in/ability ( ! "w be+ screw$ toge!r 9 _m pieces1 & makes x at ! same "t light]1 m rigid1 & less liable to j> out ( adju/m5t4 ,?is direction ( con/ruction is also foll[$ 9 ! be/ mod]n "w on ! ,cont95t & 9 ,am]ica4 ,x w\ld ext5d ?is "w beyond conv5i5t limits to (f] details ( ! wide v>iations employ$ 9 practice1 b z ! au?or has made ?is subject a life /udy1 & has embrac$1 modifi$1 & endeav\r$ to improve ?is class ( "w 9 all its details1 freely adopt+ any improvem5t he has obs]v$1 8 own in/rum5ts w repres5t l>gely 8 pres5t ideas ( ! be/ =ms1 ) ! economy ( hav+ engrav+s = illu/ration to h&4 ,transit !odolites ( portable =m w be consid]$ "h1 leav+ l>g] /ation>y in/rum5ts to ano!r *apt]4 ,illu/ration3 ,fig4 #afi4--,/anley's pat5t new model !odolite4 #dag4--,new ,model ,transit ,!odolite4--,9 ?is in/rum5t ! pr9ciples ( con/ruction are ! same z 9 ! ord9>y transit !odolite fully describ$ 9 ! la/ *apt]1 b ! di/ribution ( mat]ials & details are v diff]5t4 ,! g5]al arrangem5t ( a #e-;in* in/rum5t is %[n 9 ,fig4 #afi4 ,"o important diff]5ce1 z be=e m5tion$1 is t ! "w is n built up s mu* 9 sep>ate ca/+s & pieces z is usual1 b e possible ca/+ is %ap$ out ( ! solid to ! f9i%$ =m4 ,! v]tical axis is ( ne>ly ! same con/ruction z ! ord9>y transit1 except t ! c5tral axis is ab\t d\ble z /rong1 be+ ( once & a half ! ord9>y diamet]4 ,x is made 9 "o ca/+ ) ! upp] framework4 ,! v]ni] plate is =m$ ( ?9 h>d hamm]$ gun-metal1 :i* is screw$ ^u ! axis4 ,?is plate has n 9 ?is con/ruction to support ! sup]/ructure z 9 an ord9>y !odolite1 b has only to hold ! two axis bubbles1 :i* are !reby br\ght di/9ctly 9 view1 & ! clamp & tang5t motion1 :i* is also plac$ conv5i5tly = use ^u ?is upp] plate1 9 a position :]e !re is less risk ( accid5t ?an :5 x is plac$ ^u ! out] edge ( ! limb4 #dah4--,! ,read]s to ! horizontal limb are jo9t$ to turn up aga9/ ! /&>ds & adju/ = reflection1 z %[n ,fig4 #aca4 ,9 ?is mann] ! read]s d n ne$ deta*m5t to place ! in/rum5t 9 its case4 ,illu/ration3 ,fig4 #agj4--,section ( /&>ds ( new model !odolite4 #dai4--,! ,c5tral ,axis & ! /&>ds are made 9 "o ca/+ 9 h>d gun-metal4 ,! /&>ds are ( light cyl9drical & ribb$ section4 ,?is con/ruction1 al?\gh ( only ab\t "o-half ! weight ( ! ,a-frame arrangem5t ) its atta*m5ts1 describ$ 9 ! la/ *apt]1 0 f\nd ^u te/+ to h m ?an d\ble ! rigidity 9 resi/+ deflection1 ) p]fect c]ta9ty ( avoid+ ! accid5tal occurr5ce ( imp]fect fitt+ ( p>ts1 or ( screws j>r+ loose1 ,fig4 #agj4 ,! mak+ ( ! v]tical axis & ! /&>ds 9 "o piece 0 9 a c]ta9 s5se an exp]im5t4 ,x has be5 f\nd 9 practice ( _m ye>s n[ to give mu* great] resi/ance to all ord9>y /ra9s & j>s1 & ensure ! in/rum5t keep+ 9 ord] & adju/m5t :5 jolt$ by c>ry+ ov] ! %\ld]1 j z ! same pr9ciple acts 9 ! dumpy level2 b at ! same "t1 9 cases ( viol5t accid5t1 su* z ! fall ( ! in/rum5t f a height1 x r5d]s repairs some:at m exp5sive1 z ?is entire "p might h to be re9/at$ in/ead ( ! axis only1 ! axis ( ! !odolite be+ g5]ally made v weak t x may g fir/1 (t5 inde$ ) a slight j>4 ,_m details are ! same z ! transit !odolite be=e describ$1 adopt+ :at is ?\ght to be ! s\nde/ pr9ciple 9 all cases4 #dbj4--,! ,compass-box 9 ?is in/rum5t is atta*$ "u ! limb4 ,x is ( ! tr\gh =m %[n ,fig4 #cb1 page #gd4 ,! magnetic nor? is set to z]o4 ,! tribra* is ( ! =m describ$ = levels1 illu/rat$ ,figs4 #gb & #gc1 p4 #abh4 #dba4--,! weights ( transit !odolites ( ?is con/ruction are ab\t #f-;in* 9 gun metal #ad lbs41 alum9ium1 #h lbs4 #e-;in* #aa #f #d-;in* #g #d ,?is patt]n embodies all ! ess5tial features ( a ?or\ghly reliable & conv5i5t in/rum5t = all-r\nd g5]al survey+4 ,x has no unnecess>y elaborations & is a /rong1 light & compact in/rum5t suitable = cont9u\s h>d we>4 ,x has few] pieces ?an any o!r design & is pack$ 9 its case complete 9 "o piece ready to screw ^u its /& ^u be+ tak5 out ( its case4 ,illu/ration3 ,fig4 #aga4--,/anley's simple slid+ /age = tribra* !odolite4 #dbb4--,! au?or has devis$ a special arrangem5t = displacem5t ( axis = ?is !odolite1 :i* does n int]f]e ) its valuable quality ( /&+ ! tribra* on a wall or flat surface1 ,fig4 #aga4 ,9 ?is s*eme ! arms ( ! tribra* are slightly elevat$ by ! foot screws4 ,a flange is =m$ on ! top ( ! head ) a lead+ tube ?r\gh x to ! upp] surface ( ! l[] tribra* plate2 ^u ?is tube an upp] flange is screw$1 s t ! plate comes betwe5 ! two flanges1 :]e x may be fix$ by means ( rotation ( ! flange by a ?umb-piece4 ,! engrav+ %[s ! arrangem5t ) ! axis displac$ to its extreme po9t1 ab\t ( an in* f ! c5tre4 ,illu/ration3 ,fig4 #agb4--,/anley's #d-screw slid+ /age4 ,illu/ration3 ,fig4 #agc4--,/anley's solid r\nd =m tripod ) slid+ head4 ,illu/ration3 ,fig4 #agd4--,/anley's telescopic tripod ) slid+ head4 ,a some:at simil> arrangem5t is made = f\r-screw levell+ in/rum5ts %[n on page #bej at ,fig4 #agb1 b 9 ?is ! slid+ motion is fix$ to position by ! action ( ! levell+ screws4 ,x is sometimes pref]r$ to h ! slid+ adju/m5t ^u ! tripod head in/ead ( ^u ! in/rum5t1 & 9 "s cases = gett+ a great] range ( movem5t1 on bo?1 & = ?is purpose ! revis] has design$ ! two tripods %[n at ,figs4 #agc & #agd1 ! =m] be+ ( ! r\nd solid patt]n1 & ! latt] hav+ adju/able slid+ legs4 ,a some:at simil> arrangem5t is made = a slid+ head to a fram$ tripod z %[n bel[1 ,fig4 #age4 ,illu/ration3 ,fig4 #age4--,/anley's fram$ /& ) slid+ head4 #dbc4--;,improv$ ,transit ) ,adju/able ,axis4--,?is in/rum5t1 ,fig4 #agf1 9 g5]al1 resembles t la/ describ$1 except t x has a l>g] telescope & x is m\nt$ on a slid+ /age ) screw adju/m5ts1 :i* is p>ticul>ly describ$ bel[4 ,x is frequ5tly provid$ ) a ta*eometrical eye-piece = giv+ horizontal di/ances by subt5se tak5 on ! incl9e1 :i* w be describ$ 9 ,*apt] ,,xii4 ,illu/ration3 ,fig4 #agf4--,/anley's pat5t new model !odolite1 ) me*anical /age4 #dbd4--,! ,me*anical ,tribra* ,/age4--,?is important addition to ! !odolite above describ$ p]mits exact adju/m5t ov] a /ation4 ,! upp] plate ( ! tribra* ) ! movable /age is %[n 9 ,fig4 #agg4 ,a dovetail slide is fitt$ ^u ! base ( ! /age adju/able = we> by a slip-piece ) two screws at ! n>r[ "p4 ,! slide is adju/$ to position 9 ! direction ( its dovetail fitt+ by a l>ge mill$ screw s z to move ! :ole in/rum5t above x = c5tr+ 9 ?is direction4 ,an upp] slide act+ 9 ! same mann]1 ) dovetail fitt+ pieces at sides moves = an equal di/ance = c5tr+ transv]se to ! l[] slide by a mill$ head4 ,?is gives ! same k9d ( motion ( displacem5t t we h 9 ! slide re/ ( a la! or ! me*anical /age ( a microscope1 except t 9 ?is case we h a k9d ( ?ree-po9t be>+ surface4 ,! motion giv5 to ! screws p]mits ! p]fect adju/m5t ( ! !odolite ov] a po9t on ! gr\nd correspond+ ) ! susp5d$ plummet1 aft] ! in/rum5t is set up to ne>ly its true position by movem5t ( ! tripod legs4 ,! range ( motion is f to #a in*1 a quantity q suffici5t = f9al adju/m5t1 b :i* does n mat]ially affect ! equilibrium ( ! in/rum5t ^u its rigid tripod1 z x has 9 ?is case a broad solid base ev5 9 ! extreme positions ( ! slide4 ,illu/ration3 ,fig4 #agg4--,/anley's pat5t tribra* me*anical /age4 ,?is movem5t be+ above ! levell+ screws1 ! adju/m5t ( ! in/rum5t = level is n affect$ by its use1 z 9 ! case ( all slid+ arrangem5ts bel[ ! levell+ screws4 ,suitable means are provid$ = tak+ up any we> t might occur 9 ! slides4 #dbe4--,! above /age is support$ ^u ?ree foot screws1 ! female fitt+s be+ specially long to give pl5ty ( be>+ surface to prev5t we>2 !y are sawn d[n on "o side s t !y spr+ lightly ^u ! screws1 & are provid$ ) cross cap/an screws = tight5+ up :5 necess>y4 ,?is plan gives ! screw ab\t in* ( ?read1 & p]mits adju/m5t = com=table movem5t & = we> )\t any risk ( %ak9ess4 ,! screw 9 l>g] in/rum5ts ( ?is class has a cap to exclude du/4 ,! foot ( ! screw has a ball :i* re/s 9 a slott$ tube be=e describ$1 ,fig4 #ga1 p4 #abg4 #dbf4--,?is !odolite ) me*anical /age is g5]ally fitt$ ) illum9at$ axis = tunnel "w1 art4 #chc4 ,! lamp is n %[n 9 ! illu/ration4 ,! weights ( ?is make ( !odolite are ab\t #f-;in* 9 gun-metal #ah lbs41 alum9ium #aj lbs4 #e-;in* #ac #g #d-;in* #i #d #dbg4--h-;in* ,transit ,!odolite4--,= ord9>y survey+ ! small] in/rum5ts are suffici5t4 ,= op5+ a survey 9 new c\ntries ! #h-;in* in/rum5t1 ,fig4 #agh1 or a l>g] "o1 is g5]ally us$ = ! sup]ior triangulation1 p>ticul>ly = obs]vations at night ( di/ant lights :5 great] light-grasp+ p[] is dem&$ ( ! telescope4 ,! l>g] circle gives a m exact read+ ( ! limb1 :i* is g5]ally divid$ to read cle>ly to t5 seconds ( arc1 & by e/imation suffici5tly ne> to obta9 five seconds read+ v approximately ) ! v]ni]s4 ,:5 in/rum5ts exce$ #h-;in*es1 ! read+ is by means ( microscopes1 ! application ( :i* w be describ$ fur!r on4 ,illu/ration3 ,fig4 #agh4--h-;in* transit !odolite4 #dbh4--,! #h-;in* transit illu/rat$ is ( ! au?or's model4 ,x is 9 g5]al /ructure simil> to ! #f-;in* j describ$1 except 9 c]ta9 specialities4 ,! in/rum5t does n clamp ^u ! v]tical circle1 b a simil> circle is provid$ ^u ! opposite side ( ! axis4 ,?is answ]s two purposes1 x balances ! pressure ^u ! pivots & obviates di/urbance ( ! division by ! clamp4 ,! pr9cipal bubble is support$ ^u ! v]ni] frame1 z special exactness is n requir$ = ! in/rum5t to be us$ z a level4 ,! base support is ^u ! ,ev]e/ tribra* sy/em1 :i* w be describ$ 9 ! next *apt]4 ,a long compass is %[n1 b a telescopic compass is sometimes us$4 ,! in/rum5t is %[n ) an axis-lamp & diagonal eye-piece = /> obs]vation4 ,illu/ration3 ,fig4 #agi4--,/anley's quick-sett+ transit !odolite4 #dbi4--,! v]tical axis ( ?is in/rum5t is sometimes pi]c$ = a look-d[n telescope to sight its v]tical position on ! gr\nd to ! c5tre ( a peg4 ,?is w be describ$ ) geodetic in/rum5ts 9 ! next *apt]4 ,x is an exp5sive ref9em5t1 seldom necess>y1 z ! axis ) plummet may easily be br\ght )9 ! t5? ( an in*4 ,!odolites ( eight in*es & ov] are uni=mly pack$ 9 two cases4 ,! l[] "p is pack$ 9 a case by itself1 ! upp] p>ts connect$ ) ! v]tical circle & all ! accessories1 eye-piece1 plummet1 etc41 =m+ ! cont5ts ( ano!r case1 ea* "p be+ suffici5t = "o man to c>ry )\t ! tripod4 ,! weight ( ! entire in/rum5t is #bi lbs4 #dcj--,quick-sett+ ,!odolites4--,! dem& = in/rum5ts ) quick-sett+ arrangem5ts has greatly increas$ ( late ye>s4 ,!y save a great deal ( "t 9 sett+ up1 & also save we> ( ! levell+ screws1 z ! in/rum5t may be in/antly set ne>ly level by its means1 s t less ?an half a turn ( ! levell+ screws w br+ x to true level4 ,an ord9>y transit is %[n ,fig4 #agi1 fitt$ ) a simil> arrangem5t to t describ$ art4 #bdj1 p4 #acb4 ,illu/ration3 ,fig4 #ahj4--,railway !odolite4 #dca4--,railway ,!odolite4--,!re are objections made to ! transit !odolite by "s civil eng9e]s t x is a l>ge & heavy in/rum5t1 only to be accept$ = its p]fect conv5i5ce ov] light] =ms4 ,to meet ?is objection ! au?or has made a special transit !odolite1 ,fig4 #ahj1 :i* is suffici5t = railway "w & g5]al survey+ ^u mod]ately level c\ntry4 ,! transit pr9ciple is cons]v$ by balanc+ ! telescope on its axis to p]mit x to transit ov] ! eye-end only4 ,! v]tical arc is omitt$ z be+ unnecess>y = railway "w4 ,! in/rum5t is con/ruct$ especially l[ & ( great rigidity & solidity1 ) light weight4 ,! compass is ( ! tr\gh k9d4 ,! limb is cov]$ = protection4 ,x is extremely portable4 ,weight ( #d-;in*1 #g lbs42 #e-;in*1 #i lbs42 #f-;in*1 #ab lbs4 ,be+ con/ruct$ = r\gh1 h>d we> & local use x is n made 9 alum9ium4 #dcb4--;,= tunnell+ und]gr\nd railways ! m9+ !odolite describ$ fur!r on w be f\nd ! mo/ valuable = railway eng9e]s4 #dcc4--,m\nta9 ,transit ,!odolite4--,?is in/rum5t1 ,fig4 #aha1 is design$ = geographical exploration1 & mak+ sket* surveys4 ,x embraces ! transit pr9ciple = ! conv5i5ce ( tak+ z5i? />s4 ,x is made 9 #c-;in* & #d-;in* sizes4 ,x has two v]ni]s to ! horizontal limb read+ to m9utes1 & a s+le v]ni] to ! v]tical circle4 ,x has be5 made by ! au?or 9 alum9ium alloy only1 ! total weight be+ #b lbs4 = ! #c-;in* & #c lbs4 = ! #d-;in*4 ,! eye-piece reads direct or diagonally4 ,x has clamp & tang5t adju/m5t to bo? circles1 & a tr\gh compass4 ,! tripod slides up to half l5g?1 ea* leg be+ adju/able to fix to any l5g? )9 ! range ( ! slide to accommodate x to ! surface ( incl9$ rocks4 #dcd4--;,a ,m\nta9 ,!odolite is a t]m appli$ to any v small or light !odolite4 ,^! are g5]ally made to ord]1 v frequ5tly to a r$uc$ model ( a l>g] !odolite1 #c in*es be+ a common size4 ,! telescope is occasionally plac$ ^u ! side ( ! horizontal axis to transit4 ,!odolites ( ?is class g5]ally weigh mu* m ?an ! above-describ$ in/rum5t1 a common weight be+ #e to #g lbs4 ,illu/ration3 ,fig4 #aha4--,/anley's m\nta9 transit !odolite4 #dce4--;,improv$ ,sol> ,atta*m5t4--,! revis]'s improv$ sol> atta*m5t admits ( a full v]tical circle be+ employ$2 x also has a clamp & tang5t to ! h\r circle & decl9ation arc & quick act+ clamp & f9e adju/m5t to ! sol> arm4 ,an in/rum5t s fitt$ is %[n on p4 #bfj1 ,fig4 #ahb4 ,illu/ration3 ,fig4 #ahb4--,/anley's sol> atta*m5t4 #dcf4--,micromet] ,read+ ,!odolites4--,! favor ) :i* ! small] micromet] read+ !odolites h be5 receiv$ & ! ev] increas+ dem& = !m ow+ to _! mu* great] accuracy has induc$ ! revis] to introduce a :ole range ( ^! in/rum5ts4 ,9 _m cases :]e great] accuracy is requir$ = horizontal ?an = v]tical angles1 ! micromet]s are only fitt$ to ! horizontal circle & ! v]tical circle has v]ni]s z usual4 ,a useful in/rum5t = g5]al survey+ )\t any unnecess>y elaboration is %[n bel[ at ,fig4 #ahc4 ,illu/ration3 ,fig4 #ahc4--,/anley's micromet] transit !odolite4 ,! #f-;in* in/rum5t reads to #e seconds ( arc on ! horizontal & to #aj seconds ( arc on ! v]tical circle1 & ! #e-;in* in/rum5t to #aj seconds ( arc on ! horizontal & to #bj seconds ( arc on ! v]tical circle4 ,a full micromet] read+ in/rum5t is %[n at ,fig4 #ahd1 ! #f-;in* read+ to #e seconds ( arc on bo? circles & ! #e-;in* read+ to #aj seconds ( arc on bo? circles4 ,illu/ration3 ,fig4 #ahd4--,/anley's full micromet] transit !odolite4 ,a specially light =m ( micromet] read+ transit 7,fig4 #ahe7 has rec5tly be5 design$ by ! revis] :i* has met ) mu* fav\r4 ,x has a #d-;in* horizontal circle read+ by micromet]s to #bj seconds ( arc :i* may be approximately read by m5tal subdivision to #e seconds1 & a #d-;in* v]tical circle read+ by v]ni]s to s+le m9utes4 ,x is also made micromet] read+ to #bj seconds ( arc to bo? circles4 ,! compass is ( circul> =m read+ by microscope to -degrees1 :i* may easily be e/imat$ to a ?ird ( ?is4 ,illu/ration3 ,fig4 #ahe4--,/anley's light micromet] transit4 ,an example ( a m ref9$ micromet] transit is %[n at ,fig4 #ahf4 ,?is in/rum5t 0 design$ by ,dr4 ,e4 ,deville1 ,,ll4,d41 ,surveyor-,g5]al ( ,canada1 & is arrang$ = latitude det]m9ation by ,talcott's ,sy/em1 & g5]al geodetic "w4 ,illu/ration3 ,fig4 #ahf4--;,dr4 ,deville's transit4 ,x has a #f-;in* horizontal circle read+ by micromet]s to #e seconds ( arc1 & a #d-;in* v]tical circle read+ by v]ni] to #a m9ute1 ) z5i? _s level graduat$ to #b seconds ( arc1 deta*able & int]*angeable ) a small level = ord9>y use4 ,! telescope is #ad in*es sol> focus ) l>ge object glass s t obs]vations may be tak5 ( />s up to ! six? magnitude2 x has a revolv+ micromet] diaphragm & electric illum9ation to micromet]s1 to diaphragm bo? front & back1 & to z5i? _s level1 x has also a rheo/at = regulat+ ! am\nt ( light1 & a dynamo g5]ator = supply+ ! curr5t4 ,illu/ration3 ,fig4 #ahg4--,/anley's pat5t univ]sal transit !odolite4 ,! univ]sal transit design$ by ! revis] is %[n at ,fig4 #ahg4 ,?is is an #h-;in* in/rum5t1 read+ by micromet]s on bo? circles to #b seconds ( arc1 & is fitt$ ) all ! necess>y arrangem5ts = univ]sal "w4 ,a description ( ! l>g] geodetic in/rum5ts is giv5 9 a subsequ5t *apt]4 ,,*apt] ,,ix4 ,,pla9 ,,!odolites ,,9 ,,:i* ,,! ,,transit ,,pr9ciple ,,is ,,n ,,employ$--,,! ,,pla9 ,,!odolite--,,improv$ ,,con/ruction--,,ev]e/',s-- ,,simple--,,adju/m5ts ,,& ,,exam9ation ,,( ,,!odolites4 #dcg4--,! pla9 !odolite is ( ne>ly its orig9al =m z inv5t$ by ,sisson4 ,x /ill reta9s a limit$ popul>ity1 :i* is pr9cipally due to its portability1 be+ ( less bulk & weight ?an ! transit ( equal diamet] ( circle4 ,if we consid] ! railway !odolite describ$ 9 ! la/ *apt] z a simple =m ( transit1 ?is mu/ be consid]$ z an exception ) reg>d to ! bulk & weight1 n be+ great] ?an t ( ! pla9 !odolite4 #dch4--,! ,pla9 ,!odolite4--,= ! g5]al description we may foll[ t giv5 9 ,*apt] ,,vii4 = ! #f-;in* transit = all p>ts ( ! in/rum5t bel[ ! v]ni] plate1 & = ! compass-box above ?is plate4 ,! con/ruction ( ! in/rum5t v>ies f ! transit 9 hav+ a half v]tical circle only1 ) a s+le v]ni]1 & 9 ! diff]5ces 9 ! arrangem5t ( ! fitt+s connect$ ) ! telescope4 ,a s+le microscope is g5]ally us$ on ! horizontal circle1 & ?is passes 9 a groove f "o v]ni] to ano!r1 in/ead ( hav+ two microscopes on arms jo9t$ ^u ! v]tical axis1 z 9 ! bett] con/ruction ( transits be=e describ$4 ,! /&>ds or ,a-frames 9 ! ord9>y pla9 !odolite are atta*$ to ! v]ni] plate1 b n g5]ally to ! compass-box4 ,! pivots ( ! transv]se axis1 :i* are made exactly equal 9 size1 re/ on c\pl$ be>+s on ! tops ( ! /&>ds1 :i* are 9 con/ruction made toge!r1 & !re=e exactly alike4 ,! transv]se axis is n adju/able1 z 9 ! transit !odolite previ\sly describ$2 ! /&>ds h !re=e to be adju/$ to height 9 ! manufacture by fil+1 ) ! application ( a special /rid+ level1 until ! transv]se axis is br\ght p]man5tly p]p5dicul> to ! v]tical axis4 ,illu/ration3 ,fig4 #ahh4--e-;in* pla9 !odolite4 #dci4--,! v]tical arc is fitt$ ov] ! transv]se axis2 t is con/ruct$ ) a turn$ flange to :i* ! arc is firmly screw$4 ,! arc is divid$ to #cj & reads ) a v]ni] to m9utes4 ,! v]ni] is fix$ directly to ! v]ni] plate1 & reads g5]ally ) a microscope jo9t$ on ! transv]se axis1 b sometimes ) a loose magnifi] = economy4 ,divisions = diff]5ce ( hypot5use & base are occasionally divid$ on ! back ( ! arc4 ,! v]tical arc has a clamp & tang5t plac$ at ! back1 !re=e ?is _c be %[n 9 ! engrav+4 ,along ! b> above ! v]tical arc a /\t plate is atta*$ by screws4 ,f ?is a pair ( ,y's ) clips & eye-p9s1 z describ$ = ! ,y-level1 art4 #aib1 supports ! telescope4 ,! telescope is ( ! same con/ruction z t describ$ = ,y-levels1 ) turn$ coll>s4 ,! diaphragm is cross-webb$4 ,= economy a simple cap is g5]ally put to ! telescope in/ead ( ! bett] plan ( a ray %ade4 ,! pr9cipal level is fix$ to coll>s fitt$ r\nd ! telescope1 to :i* are atta*$ "o slot-piece = lat]al adju/m5t ( ! level1 & "o screw-piece = l9e> adju/m5t by means ( two cap/an nuts4 ,! level is plac$ "u ! telescope = compactness4 #ddj4--,! p>ts ( ! pla9 !odolite bel[ ! /&>ds are ! same z ^? already describ$ = ! transit !odolite1 except t ! v]ni] plate c>ries "o level only at "r angles to t ( ! telescope4 ,! telescope is !re=e set to z]o by ! v]tical arc1 & ! two levels are !n us$ z ! pair ^u ! v]ni] plate ( ! transit4 ,! means provid$ = ! adju/m5t are ! same z ^? ( ! ,y-level1 b ! ,y's are adju/$ firmly by ! mak] by fitt+ !m d[n ^u ! ,y-plate 9 ! manufacture4 #dda4--,! pla9 !odolite1 except :]e price is ! fir/ consid]ation1 appe>s to be go+ gradually out ( use1 be+ sup]s$$ by ! transit4 ,x has _h a long day s9ce its fir/ conception by ,sisson ab\t #agcj4 ,= #d-;in* & #e-;in* in/rum5ts ! mak]s /ill f9d a small dem&4 ,! #f-;in* is r>ely enquir$ =4 ,! pla9 !odolite _c compete ) ! transit = p]fect utility1 b x holds ! m]it ( less weight & ( great] portability4 ,! weights ( ! ?ree sizes 9 g5]al use are z foll[s3-- ,weights ( ,pla9 ,!odolites4 ,in/rum5t4 ,case4 ,out] ,case4 ,tripod4 #d-;in* #g lbs4 #g lbs4 #c lbs4 #h lbs4 #e-;in* #aa #h #d #i #f-;in* #ag #aj #e #aa ,v light #c-;in* & #d-;in* pla9 !odolites ( f #e lbs4 to #g lbs4 complete are made occasionally = travell]s4 ,illu/ration3 ,fig4 #ahi4--,/anley's new model pla9 !odolite4 #ddb4--,! au?or has rec5tly modifi$ ! pla9 !odolite1 ,fig4 #ahi1 = :i* !re /ill rema9s a small dem& 9 ! ,colonies1 by mak+ ! con/ruction mu* m solid by %ap+ ! "w out ( s+le ca/+s 9 gun-metal = p>ts =m]ly screw$ toge!r 9 _m pieces1 :i* =m]ly 0 necess>ily arrang$ to p]mit facility ( con/ruction by h&-"w4 ,!re are also 9 ! new in/rum5t "s improvem5ts made 9 detail4 ,! limb divid+ is cov]$ = protection4 ,! read]s are jo9$ ?r\gh ! v]tical axis & are h+$ to turn up4 ,! compass has an alum9ium r+ ) a microscope :i* p]mits x to be read at a conv5i5t height & mu* m accurately4 ,! tang5t screws are cov]$ to exclude du/1 & "s o!r improv$ details4 ,illu/ration3 ,fig4 #aij4--;,ev]e/'s !odolite4 #ddc4--;,ev]e/'s ,!odolite1 ,fig4 #aij1 design$ by ! late ,sir ,george ,ev]e/1 & us$ = details ( ! great trigonometrical survey ( ,india1 is built up v mu* ^u a well-kn[n common ,fr5* model4 ,9 s]vice 9 ,india x has prov$ an excell5t in/rum5t4 ,! horizontal circle or limb ( ?is in/rum5t consi/s ( a s+le plate1 ^u :i* ! silv] is inlaid flat ^u ! surface1 ^u ! plan %[n1 ,fig4 #abh4 ,9 place ( ! ord9>y v]ni] plate ?ree arms are ext5d$ f ! c5tral axis1 :i* c>ry ea* a v]ni] at its end1 read+ to a fiducial edge1 ,fig4 #abg1 p4 #ahf4 ,! v]ni]s trisect ! circle1 & are m>k$ ,a1 ,b1 & ,c4 ,a f\r? arm1 proce$+ f ! same relative position ( ! c5tre z ! arms ( ! v]ni]1 c>ries a clamp & tang5t :i* is simil>ly con/ruct$ to t ( ! ord9>y !odolite describ$4 ,! in/rum5t has also an "u clamp & tang5t = sett+ ! telescope to be>+1 or = repeat+1 z 9 ! ord9>y !odolite4 #ddd4--,! horizontal axis c>ries ! telescope 9 a cyl9drical fitt+ z 9 ! transit !odolite1 t]m9at+ 9 two pivots :i* are set to p]man5t position z 9 ! pla9 !odolite4 ,! pivots re/ 9 be>+s ^u %ort /&>ds c>ri$ out f ! c5tre ^u a flat horizontal b> to :i* a _s level is atta*$ = adju/m5t ( ! pivots to horizontality4 ,v]tical angles are read (f ^u two arcs :i* h a horizontal axis z _! c5tre atta*$ to ! telescope1 s z to move ) x 9 ! v]tical plane1 ) clamp & tang5t adju/m5t4 ,an index1 ^u ! same c5tre c>ries two v]ni]s & has a _s level atta*$ to x4 ,! v]ni]s are read by a pair ( microscopes4 ,^u ! upp] side ( ! telescope a tr\gh ne$le is plac$4 #dde4--,?is in/rum5t has be5 us$ 9 milit>y surveys by ! ,royal ,eng9e]s4 ,! objections t civil eng9e]s h made to ,ev]e/'s !odolite are t ! work+ p>ts are made v op51 s t ! wet & du/ intrude2 fur!r x lacks ! g5]al conv5i5ce ( ! transit pr9ciple1 :i* is necess>y = a/ronomical obs]vations4 ,! tripod is sometimes made ( ! ord9>y solid section1 art4 #baf2 b = ,india1 :]e c>ry+ lab\r is *eap1 a heavy fram$ /& is us$1 :i* is special1 z foll[s3-- ,illu/ration3 ,fig4 #aia4--;,ev]e/'s lock+ plate tribra*4 #ddf4--;,ev]e/'s ,tribra*4--,! upp] "p ( ! engrav+1 ,fig4 #aia1 %[s ?is tribra* t supports ! upp] "p ( ! in/rum5t directly ^u its v]tical axis4 ,! ?ree arms ( ! tribra* c>ry ea* a mill$-head$ adju/+ screw1 ! nut ( :i* is =m$ 9 ! arm4 ,! arm is sawn up to admit ( adju/m5t1 t ! mill$ head may turn s(tly b )\t any %ake4 ,! l[] po9ts ( ! mill$-head$ screws1 te*nically feet1 fall into ,v-grooves 9 ! head ( ! tripod4 ,! ,v's are n %[n 9 ! engrav+4 ,above ! upp] surface ( ! tripod head1 a ?91 ?ree-arm$ plate ( metal1 t]m$ ! lock+ plate1 is c5tr$ ^u ! holl[ axis ( ! head1 s t x w move lat]ally4 ,! lock+ plate has a hole & slot at ! end ( ea* ( its arms1 ! holes ( :i* admit ! toes ( ! feet ( ! tribra* into ! ,v-grooves =m$ 9 ! head ( ! tripod4 ,! lock+ plate :5 mov$ lat]ally locks all ! toes 9 at once1 s t ! in/rum5t is secur$ by ?is means to a c]ta9 degree f accid5t4 ,?is lock+ plate has commonly a mill$-head$ screw clamp :i* fixes x 9 its lock$ position4 ,! head ( ?is screw is "u ! tripod head1 & consequ5tly _c be %[n 9 ! engrav+4 ,x is a defect ( ?is lock+ plate t ! screws1 unless !y fall p]fectly 9 ! ,v-grooves h a t5d5cy to ride4 ,to avoid ?is ! au?or has = _m ye>s made ! ball feet fall ^u a pla9 surface1 be+ at ! same "t held 9 _! places by a slott$ plate :i* fits ov] ! neck ( ! balls4 ,?is plan1 :i* is n %[n 9 ! engrav+1 is n[ adopt$ by o!r mak]s4 ,! au?or uses also 8 pat5t tribra* sometimes on ?is in/rum5t4 ,illu/ration3 ,fig4 #aib4--,/anley's ,ev]e/ !odolite4 #ddg4--,! ,fram$ ,tripod ( ,sir ,geo4 ,ev]e/'s design is made ( /raight-gra9$ mahogany1 ea* leg be+ =m$ ( two side-pieces1 ) "o or two cross-pieces4 ,! engrav+1 ,fig4 #aia1 %[s ! head ( a tripod ( ?is con/ruction4 ,! side-pieces are splic$ toge!r at ! l[] ends1 :]e !y =m a r obtuse po9t1 :i* is %od ) a gun-metal %oe4 ,! upp] ends ( ! side-pieces c>ry /rap plates t receive a bolt :i* holds !m firmly by means ( w+$ nuts to ! tripod head4 ,! legs c be deta*$ aft] use & ! tripod head be plac$ 9 ! case ) ! in/rum5t 9 a pack+ provid$ = x4 ,"s modification ( ?is =m ( tripod is g5]ally us$ = all l>ge field in/rum5ts4 ,! au?or's improv$ ,ev]e/ !odolite is %[n at ,fig4 #aib4 ,illu/ration3 ,fig4 #aic4--,simple !odolite4 #ddh4--,simple ,!odolite4--,! pla9 !odolite be+ ( ! *eape/ con/ruction may be /ripp$ ( its sup]ior functions1 :i* are us$ = te/+ its adju/m5ts1 & be made into a simple angle measur] = lay+ out or plott+ small p>cels ( gr\nd1 small e/ates 9 build+ gr\nd1 local sewage1 gas & wat] works1 & _m o!r cases ( small surveys1 = :i* purpose x w be f\nd suffici5t1 ) a sav+ ( ab\t half ! co/ ( a p]fect !odolite4 ,! in/rum5t %[n above1 ,fig4 #aic1 0 design$ by ! au?or to meet ! above cases4 ,9 ?is in/rum5t !re is no v]tical arc4 ,! telescope has a socket axis c>ri$ ^u a s+le /&>d4 ,! axis _c be se5 9 ! figure f int]f]5ce ( ! telescope plac$ 9 front ( x4 ,! telescope is arrang$ to be fix$ 9 a level position by means ( ! loose p9 be+ press$ 9 a pair ( holes4 ,x may !n be us$ z a level by means ( ! _s level %[n on ! v]ni] plate4 ,! horizontal circle is divid$ to read ) a s+le v]ni] to #c ( arc by means ( a h& magnifi] :i* is plac$ 9 ! case ) ! in/rum5t4 ,!re are int]nal & ext]nal axes1 ea* provid$ ) clamp & tang5t motions to ! horizontal circle1 z ) ! pla9 !odolite4 ,x is support$ on a tribra*1 ! legs ( :i* are ^u ! plan1 art4 #bdi4 ,if x be made ) two v]ni]s & divid$ ^u silv] x becomes a useful light in/rum5t = fill+ 9 details ( sup]ior triangulation4 ,weight1 ab\t #d lbs4 #ddi4--;,exam9ation & ,adju/m5t ( ! ,!odolite4--,! description giv5 ( a transit !odolite1 arts4 #cfi to #chi1 w %[ t ?is in/rum5t is provid$ ) means ( adju/m5t 9 e requisite direction4 ,l>g] transit in/rum5ts possess ! same means ( adju/m5t1 b 9 "s p>ts ^! h great] ref9em5t4 ,pla9 !odolites h ! l me?ods1 except 9 ! case ( ! transv]se axis1 :i* is adju/$ once = all by ! mak]4 ,x w be necess>y1 !re=e1 to limit our space to a discussion ( ! exam9ation & adju/m5ts ( ! transit !odolite only1 ( :i* we h giv5 a full description1 arts4 #cfi to #chi1 not+ only :]e v>iations occur f p>tial diff]5ces betwe5 ?is & o!rs4 #dej4--;,a !odolite z x comes f a respectable mak] is usually c>efully adju/$ 9 all its p>ts4 ,if x has travell$ a long j\rney x is1 h[ev]1 well = an exp]i5c$ surveyor to put x ?r\gh its v>i\s adju/m5ts4 ,! corrections1 if any are requir$1 w be g5]ally v small1 & ^! 9 all probability w be ( ! same k9d z w occur 9 ! use ( ! in/rum5t & 9 ! accid5tal conditions to :i* x may be subject$ dur+ conveyance f place to place ^u a survey2 !re=e x is well to be famili> ) !m4 ,:5 a new in/rum5t is receiv$ f ! mak]1 x is necess>y to obs]ve att5tively ! mann] ( its pack+ z x lies 9 its case4 ,x is well at fir/ to lift ! p>ts a few times g5tly out ( ! case & replace !m1 s t ?is may be done at any future "t ) c]ta9ty & )\t any risk ( /ra9 ^u ! in/rum5t1 rememb]+ always t an in/rum5t 9 conveyance is mu* m liable to be ?r[n out ( adju/m5t by c>elessly replac+ x 9 its case ?an f its ord9>y use1 art4 #db4 #dea4--;,= exam9ation or adju/m5t ( ! !odolite ! tripod /& %\ld be at fir/ firmly fix$ ) legs ext5d$ to an angle ( ab\t #gj to ! gr\nd1 :i* %\ld be solid & h>d4 ,z ! telescope has to be br\ght to ! height ( ! obs]v]'s eye1 x is well to m5tion 8 /ature 9 ord]+ an in/rum5t4 ,! tripods t are made = tall m5 are (t5 awkw>d & un/eady if ! legs are ext5d$ to br+ ! telescope d[n to ! height ( a %ort p]son4 ,!y may always be cut d[n & ref9i%$ by ! mak]4 ,:5 ! tripod is set up ! toes %\ld be ea* sep>ately press$ d[n1 s t future slips are impossible4 ,?is be+ done ! in/rum5t is tak5 f its case & grasp$ firmly by ! body "p "u ! horizontal circle1 & plac$ on ! tripod at once1 !n screw$ firmly b n too tightly d[n ^u its be>+ surface4 ,) a #f-;in* transit !odolite ! upp] "p is sometimes deta*$ & pack$ sep>ately 9 its case4 ,:]e ?is is s1 aft] ! body "p is fix$ on ! tripod1 ! cleats on ! top ( ! /&>ds mu/ be op5$ out1 & ! upp] "p ( ! in/rum5t1 lift$ by its telescope1 be sl[ly l[]$ into its be>+s1 be+ p>ticul> at ! same "t t ! clips "u ! telescope embrace _! /ay-piece on ! /&>d4 ,! cleats mu/ !n be clos$ ov] ! pivots4 ,! in/rum5t be+ set up to position1 all levels may be adju/$ to ! c5tres ( _! runs1 & e "p clamp$ suffici5tly to make ! in/rum5t firm1 b 9 no case us+ viol5ce to produce a /ra9 9 any "p4 ,! clamps or o!r fitt+s are aft]w>ds sep>ately releas$ z !y are requir$ = exam9ation or adju/m5t ( ! p>ts to :i* !y relate4 #deb4--;,exam9ation = ,co9cid5ce ( ,ext]ior & ,int]ior ,v]tical ,axes4--,! !odolite be+ set up solidly1 & all clamps fix$ z above describ$1 unclamp ! l[] or ext]ior axis clamp & set ! v]ni] plate levels p>allel ) opposite pairs ( p>allel plate screws if ! in/rum5t adju/s on ! p>allel plate sy/em1 art4 #aic1 or "o level p>allel ) "o pair ( foot screws if x is made on ! tribra* sy/em1 art4 #bcd4 ,n[ adju/ bo? levels4 ,turn ! in/rum5t half r\nd 7#ahj7 & obs]ve if ! levels keep ! c5tres ( _! runs4 ,if !y d s !y are 9 adju/m5t to ! ext]ior axis4 ,if f\nd imp]fect1 ! adju/m5t by ! cap/an heads ( ! levels is set1 by means ( ! tommy or p9 :i* is provid$ 9 ! in/rum5t case1 = half ! error z x appe>s by ! bubble1 ! o!r half be+ giv5 by readju/m5t ( ! p>allel plate or tribra* screws4 ,9 ^! adju/m5ts x is necess>y to be p>ticul> always to obs]ve ! bubbles aft] ! h&s h left ! in/rum5t1 n dur+ ! adju/m5t1 :i* produces /ra9 ^u ! in/rum5t4 ,n[ clamp ! l[] clamp & note if ?is clamp+ has di/urb$ ! levels4 ,if ! levels are v s5sitive x w d s 9 a slight degree1 b ! di/urbance %\ld be v small if ! clamp is p]fect4 ,n[ unclamp ! v]ni] plate & note aga9 if ?is clamp di/urbs ! levels3 ?is %\ld also affect !m v little4 ,n[ obs]ve ! levels if !y /& exactly z !y did :5 ! ext]ior axis 0 unclamp$ at _! pres5t position1 & also at "r angles to ?is4 ,if !y rema9 z be=e ! axes are truly conc5tric4 ,if !y d n1 !re is no rem$y except at ! h&s ( ! mak]4 ,! v]tical axis to :i* ! above exam9ation applies is consid]$ ! mo/ important "p ( ! in/rum5t1 & ! "w %\ld be ?or\ghly well done2 nev]!less1 if ! levels are v s5sitive1 :i* !y seldom are1 su* m9ute faults may be detect$1 t a small all[ance may be made = imp]fection ( "w1 & ! in/rum5t /ill be consid]$ a s\nd "o4 ,9 ! use ( ! in/rum5t x is always well1 aft] ! circle is set ei!r by ! magnetic compass or by sight+ a di/ant po9t = direction1 to clamp ! l[] clamp & readju/ ! levels to ! v]ni] plate4 ,9 ?is way ! axis t w aft]w>ds be us$ = triangulation w be v]tical1 & small errors due to want ( co9cid5ce ( axes be elim9at$4 #dec4--;,exam9ation ( ! ,azimu?al ,level4--,?is level1 :i* is plac$ ov] ! telescope1 be+ made ( sup]ior s5sitiv5ess to ! v]ni] plate levels1 is mu* m accurate = adju/+ ! v]tical axis1 b mu* sl[] 9 op]ation = te/+4 ,! v]ni]s ( ! v]tical circle %\ld be accurately set to z]o1 9 :i* position ! run ( ! bubble %\ld exactly agree ) ^? on ! v]ni] plate :5 plac$ p>allel ) !m 9 any direction1 b ?is level may also be consid]$ by itself4 ,assum+ ! circle & v]ni]s correct1 or o!rwise1 x may be rev]s$ ov] ! axis by half turns 9 all positions ov] ! p>allel plate or tribra* screws1 & adju/$ by ! cap/an heads half ! error1 z be=e describ$1 = ! v]ni] plate levels4 #ded4--;,exam9ation ( ! ,divisions & ,c5tr+4--,! v]ni] plate be+ unclamp$1 ! v]ni]s1 if two1 %\ld be br\ght approximately to #j 7#cfj7 & #ahj1 & !n ! plate be lightly clamp$4 ,! microscopes or read]s are !n to be set truly radial ) ! z]o read+ ( ! v]ni]s1 & ! tang5t screw adju/$ to make "o ( ! read+s1 say ! #cfj1 exact4 ,! opposite read+1 #ahj1 is !n c>efully exam9$1 & ! error discov]$1 if any1 is due to ! imp]fection ( c5tr+1 assum+ ! divid+ p]fect4 ,at ?is po9t x is well to record ! am\nt ( diff]5ce4 ,! same exam9ation is !n repeat$ ) ! #ij & #bgj4 ,9 a prop]ly c5tr$ & accurately divid$ #e-;in* or #f-;in* !odolite ?is diff]5ce w n am\nt to m ?an #a error1 9 l>g] in/rum5ts proportionately less4 ,ow+ to ! difficulties at all times ( read+ ! circle correctly f diff]5ce ( direction ( light1 & :at is t]m$ p]sonal error1 x is well to entirely repeat ?is exam9ation1 turn+ ! in/rum5t half r\nd4 ,x is also well to repeat ! exam9ation at :at are t]m$ ! half po9ts1 #de1 #bce1 & #ace1 #cae4 ,?is w sometimes detect ! error ( c5tr+1 if !re be any1 9 its true direction4 ,! purpose ( ! two v]ni]s is to discov] ?is error4 ,9 practice ! two read+s are always tak51 & ! mean is consid]$ z ! true read+4 ,:]e !re are a great] numb] ( v]ni]s exactly ! same pr9ciple is foll[$1 b ! mean ( ?ree or m read+s is tak51 :i* ( c\rse assures great accuracy4 ,exam9ation ( ! telescope has be5 discuss$ arts4 #ajg to #aae4 #dee4--,te/+ an ,in/rum5t = its ,/ability4--,! /ability ( an in/rum5t w dep5d pr9cipally ^u ! quality ( ! workman%ip2 b ! same te/ w also indicate1 at any "t1 :e!r ! in/rum5t has be5 submitt$ to suffici5t we> to ne$ ! repair ( ! optician4 ,= ?is exam9ation ! eye-piece ( ! telescope requires to be focuss$ aga9/ a piece ( :ite pap] held obliquely 9 front ( ! object-glass s z to ?r[ a s(t :ite light into ! telescope4 ,aft] ! eye-piece is focuss$1 any di/ant po9t may be tak5 = a sight+ object ^u :i* to direct ! telescope4 ,?is po9t %\ld be focuss$ by ! telescope s t its image falls c5trally ^u ! int]section ( ! webs4 ,! eye %\ld !n be %ift$ up & d[n or sideways )9 ! range ( cle> vision ( ! webs 9 ! eye-piece to asc]ta9 t !re is no p>allax1 t is1 t ! adju/m5ts ( ! eye-piece & ! telescope are 9 true focus ^u ! webs4 ,?is prelim9>y arrangem5t be+ made1 :i* w s]ve 9 future exam9ation = o!r adju/m5ts1 all p>ts ( ! in/rum5t %\ld be exam9$ to see t ! clamps are firmly clamp$4 ,! object to be us$ z an index or sight+ po9t %\ld be br\ght by ! clamp & tang5t motions exactly ^u ! int]section ( ! webs z !y appe> 9 ! telescope1 :5 ! foll[+ exam9ations are to be made4 #def4--,tripod ,head ,exam9ation4--,! telescope be+ sight$ ^u an index po9t1 & all clamps screw$ d[n & ! tripod firmly fix$ on ! gr\nd1 take ! tripod head ( ! !odolite 9 bo? h&s & give x a twi/ ( ab\t a p\nd pull 9 "o direction2 !n exam9e ! telescope to see if ! index po9t is displac$ 9 ! telescope4 ,if x /ill /&s correct give a l twi/ 9 ! opposite direction & aga9 exam9e ! telescope4 ,if x /&s ^! opposite firm twi/s reta9+ its position ! /& is good & 9 good ord]4 ,if x does n1 assum+ good con/ruction ( /&1 ! rem$y may be f\nd 9 tight5+ up all its screws2 b if its con/ruction is bad x w n1 ev5 aft] ?is tight5+1 keep 9 ord]4 ,!re is no d\bt t m inaccurate triangulation is caus$ by defective tripods ?an f any o!r cause :atev]4 ,a p]fect in/rum5t is useless on a bad tripod4 #deg4--;,g5]al ,exam9ation ( ,fix$ ,p>ts4--,! /& be+ f\nd good by ! above process1 ! g5]al fitt+s ( ! in/rum5t may be exam9$1 aft] clamp+ all p>ts & direct+ ! telescope to a di/ant po9t1 by tak+ a quill p5 by its root or pipe & press+ its fea!r$ end ^u "o side ( ! eye-piece ( ! telescope suffici5tly to b5d ! quill1 & aft]w>ds exam9+ ! telescope to see t ! webs are n displac$ f ! index po9t4 ,?is may be done fir/ to ! "r h& & !n to ! left4 ,if ! webs /ill cut ! same object x is cle> t ! :ole ( ! c5tres1 fitt+s1 clamps1 & tang5t screws ( ! horizontal circle are correct4 ,if any displacem5t be discov]$1 ! am\nt ( diff]5ce betwe5 ! "r & left h&$ twi/s w be ! total error due to imp]fection ( "w or we> z ! case may be4 ,9 exactly ! same mann]1 b by press+ ! eye-piece upw>ds & d[nw>ds1 ! transit axis & its fitt+s may be exam9$4 ,if ! in/rum5t be n g5]ally s\nd en\gh to be> ! above te/s1 o!r critical adju/m5ts become necess>y4 ,= ! correction ( faults t may be includ$ 9 ! above op]ations1 ! p>ts ( ! in/rum5t mu/ be sep>ately exam9$4 #deh4--;,exam9ation ( ! ,transit ,axis4--,! be/ means ( adju/+ ?is axis 9 a !odolite is by a /rid+ level1 art4 #djj4 ,:5 ?is is n provid$ ) ! in/rum5t1 & x is (t5 omitt$ = economy1 ! axis is g5]ally bett] to be left z x is adju/$ 9 ?is p>ticul>1 by ! mak]4 ,to adju/ ! transit axis ! v]ni] plate bubbles are set exactly true by rev]s+ angles ( obs]vation4 ,! cleats are op5$ & ! /rid+ level is m\nt$ above ! in/rum5t re/+ ^u ! pivots4 ,! telescope is plac$ exactly ov] an opposite pair ( p>allel plate screws1 or p>allel ) two screws if ! base adju/m5t be on ! tribra* pr9ciple4 ,! /rid+ level is !n c>efully obs]v$ & rev]s$ on ! pivots4 ,if !re be any diff]5ce 9 ! run ( ! level bubble ! transit axis is adju/$ by rais+ or l[]+ ! movable ,v on :i* "o pivot re/s by turn+ ! cap/an nuts until x is q correct1 if ! in/rum5t has ?is old-fa%ion$ arrangem5t1 or if n1 by a few /rokes ( f9e em]y pap] ^u ! ,v :i* is high]4 ,?is adju/m5t is almo/ sup]flu\s1 z ! axis is g5]ally set "r at fir/1 & is n subject to *ange1 especially if solid )\t an adju/able ,v4 #dei4--;,= l>g] !odolites ( #ab in*es & ov]1 ! transit axis is mu* bett] adju/$ by means ( an artificial horizon1 :i* w be describ$ fur!r on4 ,by ! use ( ?is in/rum5t 9 ! nor!rn hemisph]e ! pole /> is fir/ obs]v$ directly by ! telescope1 & !n by its reflection f ! horizontal surface ( clean m]cury plac$ on ! gr\nd at #ab feet or s f ! in/rum5t4 ,if ! /> & its reflection cut ! webs equally 9 direct+ ! telescope by movem5t ( its transit axis only f ! "o to ! o!r1 ?is axis mu/ be truly horizontal4 ,if ! v]ni] plate be !n turn$ a qu>t] ( a revolution & ! ext]ior axis a qu>t] ( a revolution1 ! telescope transitt$ & obs]vation be repeat$1 ! v]ticality ( ! pr9cipal axis may be adju/$ ) p]fect c]ta9ty4 ,! pr9cipal axis %\ld be mov$ "o-eigh? ( a revolution all r\nd & ! bubble exam9$ at e position to assure p]fect adju/m5t4 ,) ! pla9 !odolite1 ,ev]e/'s & "s o!rs1 ! transv]se axis is fix$ to position by ! mak]1 !re=e _c be adju/$4 #dfj4--;,exam9ation & ,adju/m5t ( ,webs1 ,l9es on ,glass1 or ,po9ts4--,! ord9>y mann] ( webb+ ! diaphragm ( a !odolite 0 %[n ,fig4 #bc4 ,horizontal angles are tak5 by ! upp] int]section ( ! diagonal webs or l9es4 ,a s+le web is plac$ horizontally = tak+ v]tical angles3 x is necess>y t ?is %\ld be ne>ly true4 ,:5 ! !odolite has its axis v]tical1 z %[n by ! v]ni] plate bubbles be+ 9 ! c5tre ( _! runs1 if "o end ( ! horizontal web or l9e be set to cut a small di/ant object by sight 9 ! telescope1 ! same object %\ld keep on ! web :ile ! tang5t screw ( horizontal circle is mov$ a di/ance suffici5t to trav]se x1 ! h& be+ always tak5 f ! screw :ile ! obs]vation is made4 ,if x does n d s1 ! collimat+ screws %\ld be lightly tapp$ ) ! back ( a p5knife 9 ! direction to set x "r4 ,^! screws h a slot 9 ! body ( ! telescope1 "u ! loose cov]+ plate1 suffici5t to p]mit ( ?is small adju/m5t4 #dfa4--;,adju/m5t ( ! ,telescope to ,v]tical ,collimation4--,! eye-piece is fir/ focuss$ z be=e aga9/ a piece ( :ite pap] held obliquely 9 front ( ! object-glass until ! webs are %>ply se54 ,! axis ( ! telescope is !n exam9$ = v]tical collimation error4 ,! me?od ( do+ ?is has be5 already describ$ = a telescope plac$ 9 ,y's1 z x is 9 ! ,y-level1 & ! pla9 !odolite1 art4 #bjj4 ,! only diff]5ce ) ! transit !odolite is t in/ead ( turn+ ! in/rum5t 9 its ,y's1 ! telescope is transitt$1 z x is t]m$1 ov] on ! transv]se axis exactly half a revolution1 or #ahj z se5 by ! v]ni] read+2 & ! horizontal circle is mov$ also half a revolution1 s t ! telescope po9ts aga9 on ! same di/ant po9t :i* is us$ = an object4 ,if ! webs or l9es /ill cut ! same po9t or small object1 !y are 9 v]tical collimation1 or truly 9 ! optical axis ( ! telescope1 z reg>ds ! v]tical direction :i* ?is adju/m5t is int5d$ to secure1 presum+ ! circle has be5 correctly divid$ & c5tr$ & ! v]ni]s accurately set4 ,if ! webs or l9es d n cut ! same po9t1 half ! error is correct$ by ! top & bottom collimat+ screws ne> ! eye-piece4 ,?is process is repeat$ until x is exact1 be+ p>ticul> to obs]ve1 z be=e m5tion$1 t !re is no p>allax4 ,?is adju/m5t _c be made ) ! pla9 !odolite2 b ! z]o ( altitude may be exam9$ on bo? sides ( ! arc4 ,= ! transit !odolite1 adju/m5t by means ( a collimator1 art4 #bbi1 is mu* m conv5i5t & exact1 z lat]al & v]tical errors 9 ! position ( ! webs c be detect$ 9 "o op]ation4 ,:5 a ,y-level is at h&1 ?is may be us$ z a collimator if x is fir/ set to sol> focus4 #dfb4--;,exam9ation = ,p]p5dicul>ity ( ,transit ,axis & ,telescope4--,! :ole ( ! l[] "p ( ! in/rum5t reta9+ its position ) all clamps firm1 op5 ! cleats ^u ! top ( ! /&>ds s z to release ! transit axis4 ,n[ release "o ( ! clip screws & g5tly lift ! upp] "p ( ! in/rum5t out ( its be>+s4 ,turn ! telescope ! rev]se way upw>ds1 :i* w be 9 ?is case bubble d[nw>ds4 ,release ! clamp & turn ! clips to ! rev]se position ( ! telescope1 & rev]se ! position ( ! pivots 9 _! be>+s4 ,if ! telescope be n[ direct$ to ! same po9t z be=e1 & ! webs /ill fall ^u x1 ! telescope adju/m5t is at "r angles to ! transit axis4 #dfc4--;,exam9ation ( ! ,magnetic ,ne$le4--,if ! ne$le be plac$ 9 a circul> box1 z %[n 9 ! engrav+1 ,fig4 #cj1 x admits ( no adju/m5t4 ,if x is plac$ 9 a tr\gh1 ,fig4 #afa1 x admits ( adju/m5t g5]ally by lat]al screws to a portion ( its division4 ,if ! ne$le is us$ = a survey1 x is set to ! z]o ( ! horizontal circle by clamp+ ! v]ni] plate & br++ ! nor!rn v]ni] to z]o1 !n releas+ ! ext]ior axis & br++ ! ne$le by ! motion ( ! l[] tang5t screw to ! z]o ( its circle4 ,! corrections ( ! ne$le = giv+ true nor? h be5 discuss$1 art4 #acb4 ,x is difficult to read an ord9>y edge-b> ne$le correctly1 x is also difficult to m\nt x p]fectly true4 ,x may be read at bo? ends1 & if ! #j & #ahj po9ts cut ! l9e fairly x is consid]$ correct2 if n1 ! mean ( ! diff]5ce may be tak54 ,9 "s in/rum5ts a microscope is m\nt$ ov] ! ne$le po9t t ! ne$le may be adju/$ to a web2 b ,briti% surveyors seldom feel confid5t ( surveys by ! magnet1 & = triangulation g5]ally pref] to employ a c]ta9 numb] ( di/ant fix$ po9ts1 ! be>+s ( :i* are at fir/ z accurately asc]ta9$ z possible1 = ref]r+ objects1 r ?an to ref] frequ5tly to ! magnet4 ,:5 ! ne$le is out ( use x %\ld always rema9 lift$ (f its c5tre4 ,:5 ! in/rum5t is put by = a long p]iod x is bett] to place x 9 a v]tical position & free ! ne$le1 s t x re/s 9 ! magnetic m]idian1 9 ord] to pres]ve its magnetism z mu* z possible4 #dfd--,use ( ! ,!odolite4--,9 sett+ up a !odolite1 place ! tripod ne>ly ov] ! position 9 :i* x is to be us$4 ,?is is frequ5tly ! socket hole =m$ 9 ! e>? by ! removal ( a rang+ pole or picket1 to be describ$ ,*apt] ,,xvii4 ,!n1 aft] x is set up1 susp5d ! plummet f ! hook1 :i* w be f\nd inside ! head ( ! tripod4 ,if ! gr\nd be solid & level1 !n by %ift+ ! toes ( ! tripod slightly1 & firmly press+ !m d[n "o by "o1 ! c5tre ( ! plummet may be br\ght easily )9 ab\t #be ( an in* ( its true position4 ,! !odolite is !n plac$ on its tripod1 obs]v+ t ! telescope is 9 a position easy to be us$4 ,! c5tre ( ! picket-hole1 :5 ?is is us$ = a /ation1 is g5]ally tak5 by guess-"w1 :i* is consid]$ ne> en\gh4 ,x may be tak5 ) a little m ref9em5t by plac+1 9 ! same hole1 a %ort false picket ( n9e in*es or s 9 l5g?1 b ( ! same diamet] z ! ord9>y picket1 ! top ( :i* is cut (f smoo? & poli%$1 & has l9es sawn across its c5tre inlaid ) ebony1 describ$ 9 ,*apt] ,,xvii4 ,! false picket is c>ri$ ab\t ) ! !odolite4 ,) ,ev]e/'s & _m o!r =ms ( !odolites ! hook is fix$ "u ! axis ( ! in/rum5t4 ,9 ?is case x is usual to set ! !odolite be=e adju/+ x to ! /ation1 z !re is no sep>ate hook to ! tripod1 :i* also occurs ) all fram$ /&s4 #dfe4--,:]e !re is no hook to ! tripod an excell5t plan is to h a false c5tre1 :i* may be a piece ( turn$ wood ) a hole ?r\gh x1 to fix on ! top ( ! tripod head4 ,! plummet cord adju/s ?r\gh ! hole4 ,?is false c5tre is also conv5i5t :]e ! axis adju/s to position by a me*anical /age4 ,fig1 #aid %[s a false c5tre =m$ ( a piece ( ivory ) two slots to p]mit ! cord to loop ov] & yet hang c5trally4 #dff4--;,x may be obs]v$ t if ! tripod be set up out ( level1 :i* x mu/ necess>ily be 9 _m cases1 ! hook1 if atta*$ to ! /& & foll[+ its incl9ation1 w n hold ! cord at a truly v]tical position to ! axis4 ,surveyors commonly all[ a little = ?is incl9ation4 ,x is mu* m accurate to h ! cord susp5d$ directly f ! axis ( ! in/rum5t :5 x is con/ruct$ to admit ?is4 ,!n if a false c5tre be us$ ! plummet %\ld be susp5d$ a second "t f ! axis hook4 ,) ! k9d ( runn] %[n 9 ! figure ?is ne$ take little "t1 z x is in/antly deta*$ & replac$4 ,illu/ration3 ,fig4 #aid4--;,false c5tre = a tripod head4 #dfg4--;,aft] ! tripod is fix$ ) ! !odolite ^u x1 ! read]s are set to exact focus4 ,! horizontal circle is !n br\ght to z]o by ! v]ni] plate clamp & tang5t1 & ! compass br\ght to magnetic nor?1 if all angles are tak5 9 ref]5ce to ?is z a *eck1 by means ( ! l[] clamp & tang5t4 ,! v]ni] plate clamp is !n releas$4 ,! eye-piece is correctly focuss$ ^u ! webs1 l9es or po9ts aga9/ ! nor!rn sky1 or ^u a piece ( :ite pap] held obliquely if ?is is pref]r$4 ,! telescope is !n ready to be direct$ t[>ds a picket or o!r /ation m>k to be obs]v$1 & set correctly to focus ?is1 aft] :i* ! eye is mov$ to ! "r & left1 to ! ext5t ( cle> vision 9 ! eye-piece1 to see t ! object appe>s to rema9 fix$ ^u ! int]section ( ! upp] ,v ( ! webs1 or does n dance1 z x is sometimes t]m$4 ,! obs]vation1 if ( a picket1 %\ld be tak5 z ne> ! gr\nd z possible1 z x may n be set q upright4 ,if ! telescope is direct$ to objects :]e ! sun's rays w\ld ent] x1 ! ray %ade %\ld be pull$ out suffici5tly to q %ield ! object-glass4 ,! initial read+ to be record$ is always tak5 on ! face ( ! in/rum5t1 9 :i* position ! upp] tang5t screw is always on ! "r-h& side4 ,:5 ! obs]vation is cle> & satisfactory1 x is record$ 9 ! field-book4 ,if ! sight l9es tak5 are to be measur$ by ! *a91 ! am\nt ( incl9ation is tak5 by ! v]tical circle read+ to ! top ( ! picket if ?is is ! #f-;feet ord9>y l5g?1 or to a m>k$ b& if ?is is long]4 ,! incl9ation may be tak5 exactly to angle by v]ni]1 or r\ghly by scale ( diff]5ce ( hypot5use & base if ?is is engrav$ on ! v]tical circle1 or by bo? ( ^!--! "o z a *eck ^u ! o!r4 ,x is common to take ! upp] incl9ation z a plus 77 & ! l[] z a m9us 7-74 ,incl9ation obs]vation is record$ at ! same "t z ! horizontal position4 ,o!r obs]vations ( ! v>i\s positions or pickets are tak5 9 a simil> mann] at ! same "t4 ,:5 a /adia or ta*eometrical diaphragm is us$ ! angle is record$ & ! /adia reads ! di/ance4 ,x is ?\ght well :5 ! !odolite is 9 position to take z _m exact obs]vations z possible 9 all directions ( int5d$ /ations4 ,x is also conv5i5t to take a numb] ( obs]vations1 :i* f ! circum/ances pres5t may be inexact1 su* = in/ance z ! angles subt5d$ by trees1 gates1 r\gh build+s1 or ev5 sometimes ! corn]s ( fields1 z f su* obs]vations ^! objects may be plac$ ne>ly en\gh = ord9>y plott+ by ! angles !y subt5d f ?is & ano!r /ation ^u ! plan4 ,9 any case !y =m a *eck to positions if tak5 ) pickets aft]w>ds m def9itely4 ,^! may be m>k$ 9 ! field-book inx4 = inexact4 #dfh4--;,field ,book4--,?is book is g5]ally made #h in*es by #d in*es1 cov]$ ) r$ lea!r1 ) ela/ic clos+ b& & %ea? = p5cil1 z an ord9>y pocket-book4 ,x conta9s ab\t #ajj pages ( good /\t writ+-pap]4 ,two l9es are rul$ 9 r$ ink1 in* ap>t1 v]tically d[n ! c5tre ( ea* page4 ,! column betwe5 ! l9es is us$ = di/ances measur$ by ! direct *a9 l9e at :i* h$ges are cross$1 /ations1 (fsets1 or o!r measurem5ts are tak54 ,9 ! "r & left columns obs]vations are made ( objects desirable to be record$ or triangulat$4 #dfi4--;,= sup]ior triangulation1 def9ite & prom95t fix$ objects are tak5 at z great di/ances z possible1 s z to include ! details ( measur$ triangles )9 a sup]ior triangle4 ,a *ur* /eeple1 = in/ance1 is a fav\rite sight+ object4 ,?is _c1 h[ev]1 g5]ally be made1 a /ation = future triangulation unless a scaffold is built up ar\nd x4 ,g5]ally ! mo/ conv5i5t me?od on fairly level gr\nd1 if ! survey is l>ge1 is to h an ord9>y scaffold pole1 #bj feet or s 9 l5g?1 c>efully /raight5$ by a village c>p5t] ) a /ret*$ *alk l9e & !n pa9t$ :ite4 ,?is may be squ>$ at ! end & fix$ v]tically 9 a socket =m$ ( cross$ bo>ds to a dep? ( ab\t #c feet 9 ! gr\nd1 ) long cross+ tail pieces ramm$ firmly ) ! soil to keep x /eady4 ,:5 ?is is us$ = a triangulat+ /ation1 ! pole is tak5 out ( its socket & its exact position is c5tr$ = plac+ ! !odolite4 ,flags are sometimes us$ to indicate /ations3 _! defect is t ! w9d may bl[ !m f or to ! obs]v] & ?us r5d] !m invisible4 ,o!r me?ods w be f\nd 9 practical works on survey+4 ,?is subject w also be reconsid]$ 9 ,*apt] ,,xvii4 ,illu/ration3 ,fig4 #aie4--;,diagram bisection ( circle4 #dgj4--;,elim9ation ( ,in/rum5tal ,errors dur+ ,triangulation--,*ang+ ,face4--,x is g5]ally advis$ to *ange face ) ! !odolite aft] angles are tak5 9 ! ord9>y way1 t is1 to take fir/ ! initial angles read+ f ! face v]ni] ) ! tang5t screw on ! "r h&1 & !n to take ! same angles ) ! back v]ni]1 ! telescope be+ transitt$4 ,?is1 ( c\rse gives a read+ on a diff]5t "p ( ! circle & corrects ! error ( position ( ! v]ni]1 or c5tr+1 9 ! foll[+ mann]3--,9 ,fig4 #aie let a be z]o 7#cfj71 ! read+ ( ! face v]ni]4 ,let ! opposite read+ 7#ahj7 be at a4 ,suppose at #ahj on ! left-h& side ( ! in/rum5t ! #ahj reads at b1 !n obs]ve by ! telescope an object t cuts ?is read+1 or place a picket to d s4 ,*ange face2 !n ! same arc w come to c1 & ! telescope mu/ trav]se cb to come to ! fir/ direction4 ,! in/rum5tal error is half bc1 :i* bisect$ 9 a gives #ahj exactly4 ,! same pr9ciple ( repetition ) *ang$ face may be made an any "p ( ! circle1 & ! mean w be ! correct read+4 #dga4--,repeat+ ,angles4--,?is is p]=m$ by tak+ all p>ts ( ! circle = read+ a giv5 angle1 s t errors ( division & c5tr+ ( ! in/rum5t are elim9at$4 ,! process is z foll[s3--,take ! angul> positions ( two objects 9 azimu?1 comm5c+ ) ! z]o ( ! horizontal circle1 say ! two objects subt5d f ! c5tre ( ! in/rum5t #cf #aj2 !n turn+ ! telescope back f its advanc$ position at #cf #aj by releas+ ! l[] or axis clamp1 we may br+ ! fir/ read+ to ! orig9al z]o position4 ,n[ clamp ! l[] clamp & release ! v]ni] plate clamp & take aga9 a =w>d read+4 ,if ?is reads #cf #aj #cf #aj #gb #bj1 ! circle & c5tr+ appe> s f> correct2 b x w probably read #gb #ba1 & ! correct$ read+ w\ld be ! mean #cf #aj #cj4 ,if we cont9ue ?is sy/em r\nd 9 t5 pairs ( read+s ! :ole circle w be embrac$1 !n ! mean ( ! sum ( ! m9utes divid$ by ! numb] ( pairs ( obs]vations w give ! true read+ ( ! m9utes4 ,by tak+ ! read+s ( two opposite v]ni]s sep>ately1 ! circle w\ld be encompass$ by five read+s4 ,?is plan is foll[$ 9 all important triangulations :]e ! "w is submitt$ to calculation4 ,su* ref9em5t is sc>cely necess>y = direct plott+ ) ! protractor4 #dgb4--;,x may be obs]v$ t if ! horizontal circle is plac$ ) its z]o con/antly to magnetic nor?--n necess>ily = tak+ angles 9 ref]5ce to ?is--t ! same "p ( ! circle w always be us$ 9 ! same direction2 s t ! sum ( errors ( ! :ole circle mu/ necess>ily t5d to tie1 ev5 if ! division is to a c]ta9 degree imp]fect1 provid$ also t ! protractor us$ 9 plott+ is also kept 9 "o direction4 ,?is plan has o!rwise no inconv5i5ce1 z any arc or angle may be tak5 by ! diff]5ce ( ! circle read+ 9 any position 9 :i* x may happ5 to fall4 ,?is does n mean t x is advisable to survey above gr\nd by ! ne$le--x is q o!rwise4 ,x is be/ to h "s di/9ct1 %>ply def9$ object to :i* all angles are ref]r$1 & !re=e call$ a ref]r+ object1 z ! g5]al index4 ,! magnetic be>+ ne$ only be ! initial position ( ! horizontal circle ( ! in/rum5t4 #dgc4--,) l>g]1 :at are t]m$ geodetic in/rum5ts1 to be describ$ 9 ! next *apt]1 con/ructive errors are n p]missible2 b ^! in/rum5ts are obs]v$ "u altoge!r diff]5t conditions1 :i* are suitable to ! precision dem&$4 ,a l>ge !odolite is g5]ally fix$ ^u solid rock1 or masonry ) good f\ndation1 or ^u a v firm solid fram$ /&1 & is protect$ f w9d1 sun & ra94 ,:]e x is necess>y on level gr\nd to elevate ! in/rum5t = m ext5sive view1 a prop] /ructure is built1 9 :i* ! !odolite is isolat$ f ! out] walls or enclosure c>ry+ ! /age ^u :i* ! obs]v] works1 s t no vibration or deflection ( ?is1 caus$ by ! w9d or ! weight ( ! body1 affects ! in/rum5t4 ,"u su* conditions angles are read on v>i\s po9ts ( ! circle by micromet] microscopes s z to obta9 a suffici5t numb] ( means1 t p]sonal & in/rum5tal errors may be r$uc$ to a m9imum4 ,,*apt] ,x4 ,,l>ge ,,!odolites ,,us$ ,,only ,,= ,,geodetic ,,surveys--,,/anley',s #aj- ,,& #ab-;,,in*--#ad-;,,in* ,,altazimu?--,,colonel ,,/range',s #cf-;,,in* ,,!odolite4 #dgd4--,l>ge !odolites employ$ ^u geodetic surveys4 ,:]e ! complete survey ( a c\ntry has to be made1 a sy/em ( l>ge triangles is =m$ ov] ! c\ntry f conv5i5t positions :i* are naturally or artificially elevat$ s z to obta9 di/ant views ) ! telescope4 ,^! triangles are correctly measur$ by angles subt5d$ f a v c>efully measur$ base or bases set out ^u approximately level planes1 :i* are g5]ally ( a mile or m 9 l5g?4 ,:]e measurem5ts are d]iv$ f su* bases by con/ant int]section ( angul> positions ext5d$ !refrom to l>ge triangles or o!r polygons1 x becomes important t ! !odolite employ$ %\ld measure su* angles ) great accuracy4 ,9 ?is case ! v]ni] read+ does n possess suffici5t ref9em5t1 & ! divisions repres5t+ ! degrees h to be magnifi$ to appe> wid] ap>t1 s t !y c be m f9ely subdivid$ = ! read+ to be tak5 by means ( a micromet] microscope capable ( subdivid+ ! divisions made ^u ! in/rum5t ev5 to s+le seconds ( arc4 ,! !odolites us$ = ! sup]ior triangulation ( ,great ,brita9 7 ,ramsd5's #cf-;in* & #ah-;in*1 :i*1 al?\gh con/ruct$ 9 ! la/ c5tury1 rema9 excell5t in/rum5ts4 #dge4--,! con/ruction ( l>ge !odolites is v>i$ v consid]ably accord+ to ! conditions pres5t 9 ! c\ntry to be survey$4 ,?is subject if c>ri$ into detail w\ld ext5d mu* beyond ! int5d$ limits ( ?is "w4 ,?is *apt] w !re=e be limit$ to ! description ( a #aj- or #ab-;in* in/rum5t1 & to two hi/orical in/rum5ts :i* h be5 us$ successfully = geodetic "w4 ,illu/ration3 ,fig4 #aif4--,/anley's #aj-;in* transit !odolite4 #dgf4--aj- or #ab-;in* ,!odolite4--,^! in/rum5ts approa* ! limit 9 size ( portability = movable /ations 9 triangulation4 ,! illu/ration1 ,fig4 #aif1 is ( ! au?or's late/ #aj-;in* model1 ! patt]ns ( :i* 7 made = a !odolite ) v]ni] read+s to be us$ = ! con/ruction ( a spiral tunnel ?r\gh ! ,&es1 n[ complet$4 ,! object 9 its con/ruction 0 to obta9 great rigidity ) mod]ate weight4 ,to ?is end ! gun-metal ( :i* x is made is %ap$ out f ca/+s z compreh5sive 9 unity ( p>ts z possible4 ,x has a fram$ mahogany /& 7n %[n7 :i* is brac$ 9 e way & provid$ ) a v rigid head4 ,9 g5]al con/ruction ( ! in/rum5t illu/rat$ x has a me*anical slid+ /age & an extra p[]ful clamp & tang5t arrangem5t = ! l[] limb1 ! adju/+ screws be+ all cov]$ to exclude du/4 ,! circles are divid$ to #e m9utes1 & are read by micromet]s to s+le seconds ( arc4 ,two v]tical arcs are us$1 ! second "o c>ry+ ! clamp & tang5t arrangem5ts1 :i* also s]ves to balance ! trunnion4 ,! #aj-;in* in/rum5t c>ries a #af-;in* telescope ) #b-;in* object-glass1 & ! #ab-;in* in/rum5t an #ah-;in* telescope ) #b-a_/h-;in* object-glass4 ,! tang5t screws all act aga9/ spr+s to avoid loss ( "t4 ,illu/ration3 ,fig4 #aig4--ad-;in* altazimu? !odolite4 #dgg4--ad-;in* ,!odolite4--,= ?is description a mod]n in/rum5t is tak5 :i* ,colonel ,a4 ,r4 ,cl>k select$ = illu/ration 9 8 excell5t article on ,geodesy 9 ! n9? edition ( ! ,encyclopdia ,britannica1 to ! publi%]s ( :i* ! au?or is indebt$ = ! illu/ration1 ,fig4 #aig4 ,! in/rum5t is a comb9ation ( a transit !odolite ) special arrangem5ts z an altazimu? in/rum5t ) fix$ base1 "o side ( ! v]tical circle be+ divid$ to place ! z]o 9 a direction co9cid5t ) ! pol> axis4 ,! con/ruction z a simple fix$ transit !odolite = support ^u a p$e/al 9 /one :]e9 ! axis rema9s p]man5t = a pr9cipal geodetic /ation1 & !re=e requires only a s+le sett+ to br+ x to true nor? & s\? = z]o1 r5d]s *ange ( position ( horizontal limb unnecess>y = a p]man5t /ation4 ,= ?is ! in/rum5t is well adapt$1 & w be discuss$ "h4 ,! telescope is ( #ah in*es focus1 ) #b in*es cle> object-glass4 ,! axis pivots are ( h>d /eel3 "o is p]=at$ = illum9ation by a lamp4 ,! v]tical circle is plac$ almo/ directly ^u ! side ( ! telescope1 & ! tang5t arm on ! opposite side is ( ne>ly equal weight1 s t !re is no c\nt]balance necess>y4 ,!re are ?ree ,ramsd5 eye-pieces giv+ p[]s ( #ag1 #ce1 & #ed1 & "o diagonal eye-piece4 ,a level is atta*$ inside ! /&>d1 divid$ to read #aj ( arc3 ?is has cem5t$ ends1 art4 #agg1 & is enclos$ 9 an out] tube = protection4 ,two o!r exactly simil> levels are atta*$ to ! ext]ior axis ( ! in/rum5t4 ,! circle is divid$ to #e ( arc & reads by two micromet] microscopes to s+le seconds4 ,! v]tical axis ( ! in/rum5t is ( /eel4 ,x is plac$ ) ! apex ( ! cone upw>ds1 & t]m9ates on a triangul> spr+ ) ?ree adju/+ screws by :i* any portion ( ! weight ( ! upp] "p ( ! in/rum5t c be reliev$ f ! axis1 s t ! :ole in/rum5t moves q freely4 ,! horizontal circle reads ) ?ree micromet] microscopes on ! upp] circle to s+le seconds4 ,orig9ally ! light 0 ?r[n d[n on ! divisions by ?ree ivory cones plac$ ov] ! fronts ( ! microscopes1 z %[n 9 ! illu/ration2 b ^! h be5 *ang$ 9 ! pres5t in/rum5t = concave swivell$ reflectors1 :i* may be set to any angle conv5i5t to ?r[ suffici5t light ^u ! circle4 ,! microscopes are support$ f ! body ( ! in/rum5t ^u holl[ conical arms ^u ! same excell5t plan orig9ally us$ by ,ramsd54 ,! microscopes h adju/m5ts 9 ?ree directions1 s z to br+ !m exactly into place = trisection ( ! horizontal circle4 ,! clamp & tang5t motion is plac$ directly ^u ! divid$ circle1 & has adju/m5ts to secure fre$om f /ra92 b ?is is n p]fect--x is p]haps ! wor/ feature 9 ! in/rum5t1 "s modification ( ! plan %[n1 ,fig4 #aif1 be+ mu* bett] = l>ge in/rum5ts4 ,! :ole in/rum5t is m\nt$ on a tribra* frame1 :i* is adapt$ to /& ^u a portable table or ^u masonry4 ,! screws h lat]al adju/m5t to prev5t loss ( "t by we>4 #dgh4--;,x is a common cu/om ) ?is class ( in/rum5t to make ! axes ( h>d /eel4 ,?is plan is no d\bt v satisfactory z x leaves ! optician's h&s1 b ! au?or v mu* pref]s good h>d bell-metal4 ,:5 he saw ! above describ$ in/rum5t at ,s\?ampton1 !re 0 q suffici5t evid5ce ( ru/ on ! pivots to de/roy all p]fection ( c5tr+1 & ?is c\ld sc>cely h occurr$ ) bell-metal4 ,( c\rse ! brittl5ess ( bell-metal w\ld be objectionable :]e ! in/rum5t might be subject$ to sev]e j> 9 c>riage f place to place2 b ! au?or has obviat$ ?is by a plan he w\ld /rongly recomm5d = g5]al adoption--( hav+ ! axis ( good gun-metal1 & to silv]-sold] a r+ ( bell-metal !reon :]e ! fitt+ surfaces occur4 ,if ! gun-metal is pure x w be> ! av]age reliable /ra9 ( h>d5$ /eel1 :i* 9 h>d5+ & temp]+ is n ) c]ta9ty always free f flaws2 & ! av]age we> ( pure bell-metal is p]haps q z good z /eel4 #dgi4--cf-;in* ,!odolite1 ,fig4 #aih1 0 design$ by ! late ,colonel ,a4 ,/range & con/ruct$ by ,messrs4 ,tr\ghton ,simms = ! ,great ,trigonometrical ,survey ( ,india4 ,x is probably ! mo/ complete & p]fect !odolite ev] con/ruct$4 ,! lead+ *>act]i/ics ( ?is important in/rum5t only w be giv54 ,x has a horizontal circle #cf in*es diamet]1 & a v]tical circle #bd in*es diamet]4 ,! telescope has a focal l5g? ( #cf in*es3 ! ap]ture ( ! object-glass is #cbe in*es4 ,illu/ration3 ,fig4 #aih4--cf-;in* !odolite--,great ,indian ,survey4 ,f a photograph4 #dhj4--,! ,/& has ?ree massive mahogany legs ,,aa brac$ toge!r ) horizontal & oblique wr\ght-iron b>s ,b4 ,ea* leg is divid$ v]tically1 & conta9s a long1 gun-metal1 squ>e-?read$ screw ,c :i* is made to rotate by means ( a worm-:eel & endless screw work$ by a w9* h&le ,d1 & capable ( be+ firmly clamp$ aft] adju/m5t at po9ts ab\t #ae in*es ap>t ,e4 ,! upp] ends ( ^! screws are conical1 & fit into ?ree inv]t$ radial grooves =m$ 9 ! l[] side ( a ca/-iron circle or table1 :i* is ?us support$ by ! ?ree screws )\t be+ atta*$ to !m1 & is !re=e free to accommodate itself to expansional *anges )\t re/ra9t4 ,! upp] surface ( ! ca/-iron circle is turn$ flat & true to receive ! tribra* ( ! in/rum5t4 ,! ?ree screws ,f :i* pass ?r\gh ! side ( ?is circle are int5d$ to adju/ ! c5tre ( ! in/rum5t ov] ! /ation m>k4 ,a lev] ,g also passes ?r\gh ! side ( ! circle & actuates ?ree roll]s1 :i*1 :5 9 action1 support ! great] "p ( ! weight ( ! in/rum5t1 & s enables ! horizontal z]o to be set )\t difficulty4 ,z ! in/rum5t weighs ov] #djj lbs41 x w be se5 t "s su* arrangem5t is absolutely necess>y to enable x to be mov$ on ! ca/-iron circle4 ,:5 ! correct position has be5 obta9$1 ! lev] is ?r[n out ( action1 & ! in/rum5t rema9s immovably seat$ ^u its circul> frame4 #dha4--,! ,foot ,screws are tapp$ ?r\gh ! ends ( ! tribra* arms 9 ! usual way1 b h a range ( motion n exce$+ #a_/aj in*4 ,?is range may appe> small1 b is really mu* m ?an is requir$1 z ! upp] surface ( ! ca/-iron circle c be levell$ by ! long screws 9 ! mahogany legs be=e ! in/rum5t is plac$ on x1 s t n m ?an ab\t #a_/ajj in* ( motion is requir$4 ,! foot screws d n re/ directly on ! ca/-iron circle1 b on ! extremities ( an int]m$iate ?ree-arm$ plate1 securely bolt$ to ! c5tre ( ! in/rum5t1 ! di/ance betwe5 ! tribra* & ! plate be+ ab\t #a_/aj in*4 ,! object ( ?is arrangem5t is to obviate ! di/urbance ( level & azimu? :i* arises f clamp+ foot screws ( ! ord9>y con/ruction aft] adju/m5t1 z well z t due to loos5ess ( ! foot screws 9 ! tribra* arms4 ,! arms ( ! spr+ plate1 be+ ( consid]able wid?1 h great horizontal rigidity1 b be+ comp>atively ?9 are easily b5t v]tically4 ,! out] ends ( ! arms re/ on ! ca/-iron circle or /&2 ! foot screws pass ?r\gh ! tribra* arms1 b n ?r\gh ! spr+ arms4 ,x is evid5t !re=e t :5 ! foot screw is turn$ inw>ds ) ! screw+ motion1 ! solid end ( ! tribra* w be rais$ & ! slit betwe5 ! two arms wid5$2 b s9ce ! end ( ! screw does n re/ on ! /&1 b on an int]m$iate arm1 :i* is actually a portion ( ! tribra* itself1 x is cle> t if a lat]al pressure be appli$ to ! tribra* no motion w be caus$ !reby1 h[ev] loose ! screw may be1 s long z ! pressure is less ?an ! lat]al rigidity ( ! int]m$iate arm4 ,! lat]al pressure caus$ by turn+ ! in/rum5t 9 azimu? :5 tak+ obs]vations is greatly )9 ?is limit4 ,?is plan is p]fectly successful1 b x is only available :]e a mod]ate range ( v]tical movem5t is ne$$4 ,9 ! pres5t in/ance1 z ! ca/-iron r+ or /& on :i* ! in/rum5t is support$ is always fir/ made practically level1 ! v]tical range ( ! foot screws ne$ n be m ?an a small fraction ( an in*4 ,ano!r po9t ) reg>d to ! foot screws is _! delicacy & c]ta9ty ( action4 ,?is is atta9$ by apply+ to !m a clamp & tang5t screw arrangem5t ,h v simil> 9 pr9ciple to t sometimes appli$ to circles4 ,al?\gh ! foot screws !mselves are r co>se1 hav+ only ab\t eight ?reads to ! in*1 ! arrangem5t is su* t "o entire revolution ( ! sl[ motion tang5t screw alt]s ! level only ab\t "o second ( arc4 ,h5ce ! foot screws 9 ?is in/rum5t1 ?\gh co>se & /rong en\gh to be> great weight are probably = ! fir/ "t made 9 keep+1 9 po9t ( ref9em5t1 ) its mo/ delicate p>ts4 #dhb4--,! ,horizontal ,circles4--,! inn] or work+ circle is #cf in*es 9 diamet]4 ,x is v f9ely divid$ on silv] to #e m9utes1 & is read by five equidi/ant micromet] microscopes to t5?s ( a second ( arc4 ,x is fix$ at ! c5tre to ! tribra*1 b ev]y:]e else is p]fectly free4 ,! out] or gu>d circle consi/s ( a second horizontal circle ext]ior to & conc5tric ) ! inn] circle4 ,!re is a space ( ab\t #a_/aj in* all r\nd betwe5 ! two circles1 & ! upp] plane ( ! out] circle /&s ab\t ! same quantity above t ( ! inn] or pr9cipal circle4 ,! gu>d circle is support$ by radii ( its own1 q indep5d5t ( ^? ( ! inn] circle4 ,?is circle has sev]al functions4 ,x protects ! work+ circle f accid5tal injury2 x helps to di/ribute *anges ( temp]ature uni=mly ov] ! circumf]5ce ( ! work+ circle2 x receives ! clamp & tang5t screw1 leav+ ! work+ circle absolutely free f contact at all times2 & x be>s a /rongly-cut set ( divisions1 m visible to ! nak$ eye ?an ^? ( ! work+ circle1 :i* are exce$+ly f9e1 & !re=e w\ld be inconv5i5t = sett+ ! in/rum5t approximately 9 azimu?4 #dhc4--,! ,horizontal ,tang5t ,screws4--,x w be se5 at ,,ii t !re are two clamps & two tang5t screws to ! horizontal circle4 ,x is necess>y to h bo?1 on acc\nt ( ! l>ge size ( ! circle4 ,9 use1 ( c\rse1 !y are n bo? us$ at ! same "t4 ,9 ! pres5t position ( ! in/rum5t ! clamp & tang5t screw on ! left-h& side ( ! illu/ration w\ld be employ$2 b on rev]s+ ! telescope ?is clamp w\ld be releas$ & ! "o on ! opposite side made use (4 ,x is necess>y ) ?is1 z ) small] in/rum5ts1 to avoid loss ( motion 9 ! tang5t screws4 ,_m me?ods h be5 employ$ to obviate ?is loss ( motion1 b :ile !y are suitable to small in/rum5ts !y are n s effective ) l>ge ones1 su* z t "u consid]ation4 ,! plan adopt$ 9 ?is case is t kn[n z ! divid$ nut pr9ciple4 ,! block into :i* ! tang5t screw is tapp$ is divid$ transv]sely & ! two halves are =c$ asund]1 & !re=e act aga9/ ! contr>y sides ( ! screw ?reads by f\r int]nal spiral spr+s4 ,! t5sion ( ^! spr+s is necess>ily con/ant1 & !re=e n subject to ! di/urbance & sl[ recov]y ( ela/ic =ce unavoidable 9 an ext]nal spr+4 ,means are suppli$ = regulat+ ! t5sion ( ! f\r spr+s1 :i* mu/ be a little 9 excess ( ! =ce necess>y to move ! revolv+ mass1 )\t tak+ ! p>ts to pieces4 #dhd4--,! ,v]tical ,axis is a truncat$ cone ( /eel ) its base d[nw>ds4 ,x is ab\t #fe in*es high & #cc in*es & #b in*es 9 diamet] at ! base & summit respectively1 ! flange be+ ab\t #de in*es 9 diamet] & con/ruct$ on ! isolat$ pr9ciple4 ,! v]tical axis socket & ! five horizontal microscopic arms are ca/ 9 "o piece ( alum9ium bronze1 ! elliptical table c>ry+ ! telescope supports be+ bolt$ to ! c5tral boss 9 :i* ! socket ( ! v]tical axis is =m$4 ,! v]tical axis & ! elliptical table are bo? p]=at$ 9 ! c5tre s z to all[ ( a look-d[n telescope be+ employ$ 9 adju/+ ! in/rum5t accurately ov] ! /ation m>k4 #dhe4--,! ,telescope is furni%$ ) two sep>ate eye-ends1 c>ry+ respectively a v]tical & a horizontal p>allel wire micromet] ,j4 ,x is also suppli$ ) bo? bright & d>k field illum9ation1 ! latt] be+ employ$ :5 fa9t />s are obs]v$4 ,! v]tical circle ,k is divid$ on silv] simil> to ! horizontal circle1 & is read by two opposite micromet] microscopes :5 ! in/rum5t is us$ = t]re/rial "w3 b :5 requir$ = a/ronomical purposes f\r micromet]s c be us$1 & !y c be %ift$ to any "p ( ! circle on :i* !y are clamp$4 ,9 ! illu/ration ! f\r micromet]s are %[n 9 position4 ,! two rods or h&les se5 p>allel ) ! telescope at ,,ll are atta*$ to ! middle ( ! transit axis :]e ! telescope passes ?r\gh x1 & are int5d$ to raise or depress ! telescope )\t t\*+ x by h&4 ,^! rods are also us$ = c>ry+ adju/able c\nt]poises1 ! in/rum5t be+ s balanc$ 9 e "p t ! equipoise is z ne>ly p]fect z practicable ?r\gh any diametrical section ( ! v]tical axis4 #dhf4--,! ,_s ,levels1 bo? horizontal ,m & v]tical ,n1 are v delicate4 ,!y are con/ruct$ s t ! divisions on _! scales repres5t z ne>ly z possible "o second ( arc4 ,! scales are divid$ to tw5ty p] in*4 ,! glass bubble tubes are m\nt$ on ,v be>+s1 & are kept 9 position by light spr+s 9 su* a mann] t !y are free to adapt !mselves to *anges ( temp]ature ) p]fect fre$om4 ,!y are also enclos$ 9 ext]nal cyl9drical glass cov]s to protect !m f sudd5 *anges ( temp]ature4 ,! arrangem5ts = adju/+ ! levels are su* z to obviate /ra9s )\t risk ( %ake1 & to ensure delicacy ( action4 #dhg4--,! ,five ,micromet] ,microscopes ,o = read+ ! horizontal circle are c>ri$ by ! same numb] ( equidi/ant radial arms bran*+ f ! c5tral boss :i* c>ries ! :ole ( ! in/rum5t above ! horizontal circles4 ,^! micromet]s are made on ,rob9son's pr9ciple1 ,fig4 #aii1 t is1 ) a %ort b[ spr+ ,s hav+ a c5tral nut tapp$ ?r\gh x to keep ! t5sion betwe5 ! be>+ ( ! micromet] screw on ! end ( ! out] box & ! slide :i* c>ries ! webs con/ant ) :atev] "p ( ! screw may be 9 use4 ,! radial arms ea* c>ry a v]tical socket :i* is bor$ out cyl9drically to receive ! microscope4 ,^! sockets are slott$ v]tically1 & h ?ree clamp+ screws at ! side to hold ! microscopes firmly 9 position :5 !y are once adju/$4 ,! two webs 9 ^! micromet]s are plac$ p>allel to "o ano!r1 & at su* a di/ance ap>t t :5 9 prop] adju/m5t !y are a trifle wid] ap>t ?an ! wid? ( "o l9e on ! circle1 z %[n 9 ,fig4 #bjj4 ,! micromet] heads are divid$ into sixty p>ts1 & ! :ole is arrang$ s t 9 practice t5 revolutions ( ! micromet] screw trav]se ! webs ov] t5 m9utes ( arc or two divisions on ! circle4 ,ea* division !re=e on ! micromet] head repres5ts "o second ( arc2 & z ! divisions are cle>ly cut on silv] & ab\t "o-t5? ( an in* ap>t1 !re is no difficulty 9 read+ to ! t5? ( a second1 :i*1 on a circle ( #cf in*es 9 diamet]1 is equal to ! #jjjjjhgb ( an in*1 or ! ?ree-?\s&? "p ( "o division ( ! circle2 ?is1 z be=e /at$1 is equal to five m9utes ( arc1 or ! #jbfaf ( an in*4 ,! illum9ation ( ! microscopes1 or r ( ! divisions ( ! circle1 is a mo/ important matt]4 ,:5 su* exact measures are to be tak5 x is effect$ by means ( p]=at$ silv] reflectors atta*$ to ! micromet] arms & m\nt$ q indep5d5tly ( ! micromet]s !mselves4 ,! axis ( ea* reflector co9cides ) ! axis ( its microscope4 ,all ! reflectors h bo? v]tical & horizontal movem5ts1 & are !re=e readily adju/able to ! be/ position = secur+ effective illum9ation "u ! v>y+ conditions 9 :i* ! in/rum5t may be employ$4 ,illu/ration3 ,fig4 #aii4--,rob9son's micromet]4 ,illu/ration3 ,fig4 #bjj4--,webs ( micromet]4 #dhh4--,reliev+ ,app>atus4--,x w be readily und]/ood t ! mov+ p>ts ( s l>ge an in/rum5t mu/ necess>ily be v heavy4 ,9 ?is case ! telescope1 v]tical circle1 pill>s1 elliptical table1 horizontal micromet] arms1 & v]tical axis socket weigh ne>ly #cjj lbs4 ,x w\ld ( c\rse be impossible to take horizontal angles ) s mu* friction on ! flange ( ! v]tical axis z ?is weight w\ld produce1 h5ce ! necessity = "s =m ( reliev+ app>atus4 ,t employ$ 9 ?is case is a sy/em ( =ty spiral spr+s1 ea* ( a def9ite l5g?1 :i* :5 adju/$ support ab\t #fbe lbs4 ,! spiral spr+s are m\nt$ on a flat r+ 9 two circles ) project+ p9s to keep !m 9 position4 ,! upp] ends ( ! spr+s support a /eel r+ ) a circul> groove on its upp] surface1 betwe5 :i* & a correspond+ groove 9 ! out] "p ( ! v]tical axis socket ?ree equidi/ant1 ne>ly frictionless /eel roll]s run2 s t by ?is means ab\t #bej lbs4 weight is tak5 (f ! flange ( ! v]tical axis1 ! rema9+ weight be+ suffici5t to all[ ( ! in/rum5t mov+ ) ! necess>y fre$om1 & at ! same "t giv+ all ! /ability requisite = accurate levell+4 ,,*apt] ,,xi4 ,,m9+ ,,survey ,,in/rum5ts--,,circumf]5tors--,,pla9 ,,m9]',s ,,dial--,,sights--,,tripod ,,/&--,,adju/m5ts--,,h5d]son',s ,,dial--,,lean',s ,,dial--,,adju/m5ts--,,h$ley',s ,,dial--,,additional ,,telescope--,,improv$ ,,h$ley ,,tribra* ,,& ,,ball ,,adju/m5t--,,reflectors--,,cont95tal ,,=ms--,,!odolite ,,s\t]ra9--,,tripod ,,tables--,,/anley',s ,,m9+ ,,!odolite--,,pa/orelli',s ,,& ,,h(fmann',s ,,adju/able ,,tripod ,,heads-- ,,m9+ ,,transit ,,!odolites--,,/anley',s ,,prismatic ,,m9+ ,,compass-- ,,hang+ ,,dial--,,hang+ ,,cl9omet]--,,semi-,,circumf]5tor--,,m9+ ,,lamps4 #dhi4--,m9]'s ,circumf]5tor4--,9 ! orig9al =m ( !odolite1 z x 0 at fir/ design$ by ,digges1 op5 sights took ! place ( ! telescope4 ,! sights 9 ?is case 7 ext5d$ on arms4 ,! compass-box1 aft]w>ds add$1 0 plac$ ov] ! axis & made z free f ob/ruction z possible1 s t ! ne$le1 ^u :i* g5]al survey+ =m]ly dep5d$1 c\ld be read correctly by plac+ ! eye v]tically to ! plane ( ! horizontal circle ( division aga9/ :i* ! ne$le read4 ,aft] ! introduction ( ! telescope to ! !odolite ?is old =m ( in/rum5t took ! g5]al designation ( ! circumf]5tor2 & subsequ5tly1 be+ be/ adapt$ to und]gr\nd survey+1 x became1 ) "s slight alt]ations1 ! m9]'s dial4 #dij4--,^u ?is orig9al circumf]5tor improvem5ts h be5 made 9 ! v>i\s m9+ dials we possess1 9 all ( :i* ! l>ge op5 compass is /ill pres]v$4 ,?is prom95ce ( ! compass does n indicate t ! mod]n sci5tific m9+ eng9e] has any desire to dep5d ^u x = tak+ horizontal angles1 b t 9 close & tortu\s work+s x provides ! ne>e/ & (t5 ! only possible means ( tak+ angles hav+ reg>d to ! extreme difficulties ( obs]vation ( any k9d4 ,:]e work+s are op5 & fairly plane ! telescope & circle ) v]ni] read+ c be us$1 s t at ! pres5t "t ! bett] in/rum5ts possess ! means also ( tak+ obs]vations ( angul> direction by v]ni] read+4 ,sev]al o!r v important factors specialize m9+ f ord9>y survey+ in/rum5ts1 :i* may be /at$ z foll[s3--#a4 ,t !re %all be means ( %ort5+ ! tripod = "w 9 /rata ( small dep?4 #b4 ,t ! in/rum5t %all be l[ & compact 9 itself1 t ! head ( ! surveyor may be plac$ above x if possible1 ev5 9 %all[ work+s4 #c4 ,t great ext5t ( adju/m5t ( ! compass-box to horizontality %all be giv5 9 ! fitt+s ( ! in/rum5t1 on acc\nt ( ! difficulty ( ext5d+ ! legs at all times = tripod adju/m5t & f ! extreme incl9ation ( ! floor ( ! work+ 9 "s cases4 #d4 ,t x is desirable 9 m9+ survey in/rum5ts t ! telescope1 if !re is "o1 %all take sights at all angles ^u ! surface ( ! e>? 9 ! locality 9 :i* ! in/rum5t is us$1 z also ab\t a v]tical position1 s z to be able to sight l9es f ! top to ! bottom ( ! %aft1 or vice v]sa1 to set (f angles 9 ! same azimu? z ^? tak5 at ! surface by direction ( /ret*$ wires or o!rwise4 ,?is la/ contrivance w also give ! means ( sight+ a p]fectly v]tical po9t b5ea? ! c5tre ( ! in/rum5t plac$ at ! top ( ! %aft1 to make a concurr5t /ation bel[ dur+ v5tilation1 :5 ! plummet w\ld be di/urb$4 ,! devices by :i* ^! v>i\s requirem5ts h be5 met m or less p]fectly w g f> to expla9 ! specialities ( con/ruction f\nd 9 m9+ survey+ in/rum5ts1 :i* w n[ be describ$1 comm5c+ ) ! olde/ & mo/ simple specialis$ =m ^u :i* improvem5ts h be5 made 9 _m directions4 #dia4--,pla9 ,m9]'s ,dial4--,! orig9al simple =m ( specializ$ m9]'s dial is %[n 9 ,fig4 #bja4 ,x consi/s ( a compass1 divid$ to s+le degrees1 read by a f9ely po9t$ edge-b> ne$le m\nt$ on a jewell$ cap4 ,! ne$le has a slid+ rid] plac$ ^u x1 art4 #acj1 s t x may be c>efully balanc$ to horizontality 9 any locality 9 :i* x is us$4 ,! divid$ compass is rais$ on a /ep1 & ! upp] surface ( ! ne$le is made to be q level ) ! division :5 ! compass is horizontal4 ,9 erect+ ! in/rum5t ) ! ne$le correctly balanc$1 ! compass may !re=e be br\ght to horizontality by ! co9cid5ce ( ! upp] surface ( ! ne$le ) ! plane ( ! divisions1 )\t ! necessity ( hav+ _s levels4 ,illu/ration3 ,fig4 #bja4--,m9+ dial4 ,illu/ration3 ,fig4 #bjb4--;,cov] to ! same4 ,illu/ration3 ,fig4 #bjc4--,sight4 ,illu/ration3 ,fig4 #bjd4--,section ( ball & socket jo9t4 #dib4--,! compass-box is ext5d$ 9 "o m]idian1 nor? to s\?1 by /rong arms t c>ry a pair ( sights h+$ to turn d[n to ! surface ( ! cov] = portability4 ,! compass-box & arms toge!r are t]m$ ! limb4 ,! limb ( ! in/rum5t is m\nt$ ^u a ball & socket jo9t to be describ$4 ,! socket is slott$ d[n on "o side to p]mit ! limb to be turn$ to a v]tical position4 ,9 ?is position ! level %[n on ! front ( ! in/rum5t is us$ = levell+ by means ( ! sights3 ?is level is n1 h[ev]1 put on all pla9 dials4 #dic4--,! cov] ( ! compass-box1 ,fig4 #bjb1 is fix$ on ! box to a giv5 position by a /ud & slot4 ,x has an arc divid$ ^u its out] surface1 :i* is c5tr$ f a small hole plac$ ne> ! out] edge4 ,a l9e f ! c5tre ( ! hole to ! z]o ( ! arc is made p]p5dicul> to ! c5tral indices ( ! sights4 ,a piece ( silk or a horse-hair c>ry+ a small plummet is fix$ to hang f ! hole4 ,by ?is means :5 ! limb is turn$ d[n 9 ! slot ( ! socket & ! silk or hair /ret*$ by ! plummet to p]mit x to hang 9 front ( ! arc1 x w !n cut ! divisions1 & ?us =m a read+ index to ! arc1 giv+ !reby approximately ! v]tical angle at :i* ! sights are set to degrees4 #did4--,! in/rum5t is m\nt$ on a simple jo9t$ tripod to be describ$4 ,x w be se5 by ! above description t ?is in/rum5t is *eaply made1 & is n design$ = v exact "w4 ,x is n[ giv+ way = m exact in/rum5ts1 b x =ms ! gr\ndwork on :i* m9+ survey in/rum5ts are mo/ g5]ally con/ruct$4 ,! height ( ?is dial ) sights erect is #aa in*es2 weight1 #f lbs4 ,"s ( ! sep>ate p>ts above enum]at$1 :i* are common to _m o!r =ms ( m9+ in/rum5ts1 w n[ be m p>ticul>ly describ$4 #die4--,sights1 "o ( :i* is %[n sep>ately1 ,fig4 #bjc1 are common to m9+ in/rum5ts4 ,!y are con/ruct$ ess5tially 9 two p>ts1 te*nically t]m$ ! slit & ! w9d[4 ,! slit ,a is a n>r[ p>allel cut made ?r\gh ! metal ^u ! inn] surface ( ! sight1 :i* is turn$ t[>ds ! c5tre ( ! in/rum5t4 ,! ?ickness ( ! metal is holl[$ away on ! out] side :i* comes next ! eye1 s z to pres5t a ?9 edge only = ! sight+ slit1 z %[n 9 section at ,a4 ,9 "s in/rum5ts ! slit is =m$ ( two ?9 plates fix$ to ! sight by screws 9 slots1 :i* r5d] x adju/able bo? to wid? & position2 ?is is ! bett] way if ma*9]y be n us$ = cutt+ ! slit4 ,! w9d[ ,b is an oblong op5+1 across :i* a hair wire or a ?9 plate plac$ edgewise is fix$ 9 l9e ) ! slit4 ,! hair or wire is laid 9 a deeply engrav$ l9e1 s t x is 9 ! same plane z ! c5tre ( ! slit4 ,! ends ( ! hair are held firmly by draw+ !m ?r\gh small holes & fix+ !m !re9 by means ( dry1 conical1 p9ewood p9s press$ tightly 9 ! holes4 ,:5 a ?9 plate is us$ edgewise1 ?is is s(t-sold]$ into ! top & bottom ( ! w9d[4 ,9 ! pair ( sights ! w9d[ ( "o sight is plac$ at ! l[] position & ! slit 9 ! upp]4 ,9 ! fell[ sight ! positions ( ^! p>ts are rev]s$1 ! obs]vation be+ always tak5 f ! slit ?r\gh ! w9d[4 ,! duplication ( p>ts 9 ea* sight p]mits x to be us$ 9 ei!r direction4 #dif4--;,9 ! use ( ! ,sight ! po9t or object to be obs]v$ f ! slit %\ld appe> to be bisect$ by ! hair 9 ! w9d[ at ! same "t t x appe>s to ! eye to /& 9 ! c5tre ( ! slit4 ,= ?is reason x is n necess>y t ! slit %\ld be v n>r[4 ,x is g5]ally m com=table to take ! sight ) ! eye at ! di/ance ( #aj to #ab in*es 9 front ( ! slit to obta9 cle> vision ( x4 ,9 ?is case if x be made too n>r[ x %uts out ! field ( view4 #dig4--;,x is n q c]ta9 t ! old slit & w9d[ is ! be/ =m4 ,_m m9+ eng9e]s pref] a pair ( equal slits1 "o ( :i* replaces a w9d[4 ,9 ?is case1 in/ead ( ! wire cov]+ ! object sight$ 9 ! use ( ! in/rum5t1 ! object is made to appe> 9 ! c5tre ( ! =w>d sight slit4 ,9 ?is con/ruction ! sight ap]tures are made mu* n>r[] s t !y d n cov] too mu* ( ! field ( view4 ,excell5t "w is done ) ?is op5 =m ( sight1 & its con/ruction is mu* m solid ?an t ( hav+ loose hairs4 #dih4--,univ]sal ,sight1 t]m$ te*nically hole & cross sight1 consi/s ( a small hole ,c1 ,fig4 #bjc1 on ! inn] side ( "o sight t is holl[$ away on ! out] side :i* comes next ! eye1 s z to pres5t a ?9 edge ( ! hole only4 ,! fell[ sight ,c has a hair cross plac$ c5trally 9 a circul> w9d[4 ,?is is ( occasional use = sight+ angles approximately 9 altitude & horizon simultane\sly2 b ! cross occupies s mu* ( ! sight space t obs]vation ) x _c be dep5d$ ^u4 #dii4--;,ball & ,socket ,jo9t4--,?is is %[n 9 elevation ,fig4 #bja at ,f1 & 9 section ,fig4 #bjd ,f1 ,d4 ,x is "o ( ! olde/ =ms ( adju/m5t1 & is common to _m dials4 ,:5 ! clamp+ screw ,g is releas$ ! ball is free 9 its socket ,f to move ab\t its c5tre1 to ! ext5t ( ! op5+ at ! top ( ! socket1 9 any direction4 ,a plug ,e1 :i* really =ms ! l[] half ( ! socket1 is screw$ into ! "p ,f at ! l[] "p ( :at is te*nically call$ ! socket-piece4 ,! plug is turn$ upw>ds by its screws s z to tight5 ! ball by means ( a tang5t screw ,g :i* works 9 a rack ?read cut 9 a "p ( ! circumf]5ce ( ! plug1 ?us =m+ a screw & cross screw1 :i*1 z ! con/ruction indicates1 clamps ! ball ) great rigidity4 ,!re are sev]al o!r ball & socket arrangem5ts2 ^! w be discuss$ 9 describ+ ! special in/rum5ts to :i* !y are affix$4 ,! only objection to ?is =m is t x elevates ! dial v mu* m ?an o!rs4 #ejj4--,! ,tripod ,/& ( an ,ord9>y ,m9]'s ,dial4--,! upp] "p is %[n 9 ,fig4 #bje4 ,?is =m ( tripod is common to _m dials4 ,! legs are made ab\t #a in*es 9 diamet]4 ,! heads ( ! legs are fitt$ directly )\t brasswork betwe5 ! book-plates ,a1 to :i* !y are held by cross screws or bolts :i* =m ! jo9t on :i* ! legs move = ext5sion4 ,unless ! head be work$ out ( ! solid1 ! book-pieces are screw$ to a plate t c>ries a male plug c5tre to :i* ! dial is fix$ by a mill$-head$ screw %[n at ,fig4 #bja ,l4 ,! plug is groov$ at ! position ( ! po9t ( ! screw s z to p]mit rotation ( ! in/rum5t :5 ! screw is slightly releas$4 ,?is tripod head rema9s p]man5tly fix$ to ! legs4 ,ea* leg is jo9t$ to "p 9 its c5tre by unscrew+1 to pres5t :5 disjo9t$ a metal po9t to hold ! surface ( ! gr\nd1 to =m a %ort /&4 ,! usual height ( ! full tripod legs is #e feet2 ! upp] "p only #b feet #f in*es4 ,! usual =m ( jo9t is %[n 9 detail 9 section ,fig4 #bje4 ,c ! male screw1 :i* is fitt$ to ! woodwork by a socket & cross p9n$ to x4 ,?is piece has a po9t at its l[] end4 ,d ! socket-piece is screw$ ov] ! po9t to ext5d ! leg :5 ! tripod is requir$ ( full l5g?4 ,! woodwork ( ?is l[] piece has a conical metal po9t to bite ! gr\nd :5 x is set up 9 use4 ,occasionally = close "w %ort] legs are provid$1 or ! legs are jo9t$ 9 ?ree p>ts4 ,9 ! common dial %[n1 ! legs are left expos$ :5 out ( use2 ) sup]ior in/rum5ts !y are pack$ 9 a deal case t protects ! socket fitt+ to :i* ! in/rum5t is atta*$4 ,ano!r mu* bett] =m ( tripod w be discuss$ fur!r on ) ! in/rum5t to :i* x is atta*$4 ,illu/ration3 ,fig4 #bje4--;,jo9t$ tripod legs ( a m9]'s dial4 #eja4--;,exam9ation & ,adju/m5t ( ! ,pla9 ,m9]'s ,dial4--,! tripod %\ld be fir/ set up to full l5g? & ea* l5g? sep>ately twi/$ to "r & left to see t its socket fitt+s are good & free f %ak9ess4 ,! legs %\ld ea* be sep>ately press$ 9 & out at its c5tre to see t ! screws clamp ! p>ts firmly & are free f %ak9ess4 ,! in/rum5t %\ld !n be set up & its socket fitt+ be felt to see t x is free f %ake1 & also be turn$ r\nd to see t x moves freely4 ,! ball fitt+ %\ld be clamp$ & its rigidity be te/$ by fair pressure on ! two ends ( ! limb sep>ately4 ,! sights %\ld be exam9$ to see t !y are q l9e> ) hair & slit4 ,! compass-box %\ld be levell$ by ! co9cid5ce ( ! upp] surface ( ! ne$le ) ! plane ( ! division1 & be rev]s$ 9 e direction by turn+ ! compass-box1 ! read+ be+ obs]v$ ) ! ,n4 po9t ( ! ne$le at ,n4 ,e4 ,w4 ,s4 to see t x bisects ! graduation by angles #ahj ap>t4 ,! compass-box be+ level1 ! sights %\ld be rang$ ) an ext]nal object at a di/ance--a plumb-l9e is be/--a piece ( /r+ susp5d+ a /one answ]s--to see t !y are v]tical1 & t !y cut ! same l9e ) ! position ( ! sights *ang$ =e to back4 ,if ! sights are co9cid5t1 b d n range ) ! plumb-l9e1 ! ne$le is out ( balance1 & ?is may be correct$ by %ift+ ! rid]4 #ejb4--;,h5d]son's ,dial4--,?is is an improvem5t ^u an old =m ( circumf]5tor1#ai 9 :i* f\r sights are c5tr$ 9 opposite pairs s z to revolve ab\t ! v]tical axis1 s t "o pair ( sights may take any angle to ! o!r pair4 ,9 ,mr4 ,j4 ,h5d]son's dial ! improvem5t consi/s 9 mak+ ! compass l>g]1 ! ne$le be+ made to read by a v]ni] plac$ ^u "o end to #c ( arc4 ,mr4 ,h5d]son pref]s pla9 slit sights in/ead ( slit & w9d[ sights1 z be=e /at$1 :i* avoids ! accid5tal d]angem5t ( ! horse-hair4#bj ,! in/rum5t comb9es "s ( ! p>ts ( ,lean's dial1 to be next describ$4 ,illu/ration ( ?is in/rum5t is giv5 9 ,mr4 ,b4 ,h4 ,br\gh's ,m9e ,survey+4 #ejc4--,lean's ,dial4--,! inv5tor ( ?is in/rum5t 0 ,mr4 ,joel ,lean1 a ,corni% m9e manag]1 :o 0 well kn[n at ! end ( ! #ah? c5tury = 8 important improvem5ts 9 m9+ app>atus4 ,?is dial is /ill popul> 9 ,cornwall & o!r m9]al di/ricts4 ,9 g5]al con/ruction ! sights & limb on :i* !y are m\nt$ are ! same z 9 ! pla9 dial j describ$1 art4 #dia4 ,! legs are also ! same--o!r p>ts are additional or modifi$4 ,9 ! engrav+1 ,fig4 #bjf1 ! sights & v]tical arc ) its telescope are %[n m\nt$ toge!r on ! limb4 ,?is is done to %[ ! relative position ( ^! p>ts3 !y c\ld n 9 practice be us$ simultane\sly ^u ! in/rum5t4 ,!y are sep>ately atta*$ to ! limb by ! same pair ( mill$ head$ screws4 ,z a g5]al rule ! telescopic arrangem5t1 :i* w be describ$ fur!r on1 is us$ above gr\nd & ! sight arrangem5t bel[4 ,! details ( con/ruction are z foll[s3-- ,illu/ration3 ,fig4 #bjf4--,m9+ circumf]5tor or ,lean's dial4 #ejd4--,! ,tripod--( ! m9+ circumf]5tor1 9 common ) _m o!r =ms ( dial1 has ! legs fitt$ directly betwe5 book-pieces1 :i* are fix$ to ! l[] p>allel plate1 z %[n ,fig4 #bjf1 ?us disp5s+ ) ! sep>ate tripod head1 common to levels & !odolites4 ,o!rwise ! p>allel plates are simil> to ^? describ$ = levels & !odolites1 art4 #aic1 & are us$ 9 ! same mann]4 ,! upp] p>allel plate 9 ?is dial c>ries ! male axis1 :i* fits into a socket atta*$ bel[ ! c5tre ( ! limb 9 ! mann] j describ$ = pla9 dial4 ,! tripod /&1 ) its p>allel plates atta*$1 is g5]ally pack$ 9 a p9ewood case :5 out ( use4 ,! reason = atta*+ ! legs directly to ! l[] p>allel plate in/ead ( hav+ a tripod head is t x saves ! extra elevation ( ! in/rum5t by ! dep? ( "o screw fitt+4 ,at ! same "t x mu/ be obs]v$ t x exposes ! axis to ! air by sep>at+ ! in/rum5t at ?is "p :5 x is put by1 :i* r5d]s ! axis difficult to be kept lubricat$ & 9 smoo? work+ ord]4 ,on ! ,cont95t & 9 ,am]ica x is g5]al to deta* ! legs only1 on a plan %[n1 ,fig4 #he1 p4 #adj4 ,?is keeps ! axis atta*$1 & is probably ! bett] plan1 al?\gh x may be f\nd a little m tr\blesome to erect ! in/rum5t4 ,illu/ration3 ,fig4 #bjg4--,section ( compass-box & axis ( ,lean's dial4 #eje4--,revolv+ ,compass =ms a "p ( ,lean's dial & _m o!r dials4 ,x is %[n 9 section ,fig4 #bjg4 ,z ! axis is con/ruct$ 9 ?is in/rum5t1 ! socket-piece ,a is gr\nd to fit ! male axis ,s1 & at ! same "t x is %\ld]$ to fit ! surface ( ! p>allel plate ,t to prev5t excess ( friction on ! axis fitt+1 s t x may move easily to set ! ne$le to magnetic nor? ( ! compass-box if desir$4 ,! socket-piece is atta*$ to ! compass-box ?r\gh a coll>4 ,! compass has a /ep ,d :i* is divid$ to degrees on its inn] edge to read to ! po9t ( ! ne$le1 & simil>ly to degrees on its out] edge to read ) a v]ni] scale1 %[n ,d to #c4 ,! v]ni] is set (f on ea* side ( ! z]o l9e 9 t5 divisions1 :i* are figur$ #cj1 #de1 #j1 #ae1 #cj1 art #cbb1 p4 #ahd4 ,! upp] surface ( ! ne$le is made level ) ! upp] surface ( ! /ep4 ,! bottom plate ( ! compass-box is divid$ to #aj3 9 "s difficult positions 9 ! use ( ! in/rum5t ?is la/ is ! only read+ t c be sight$4 ,! compass-box1 :i* c>ries ! v]ni] ,b1 is fix$ c5trally on ! arm plate4 ,! arm plate is c5tr$ ^u a /ep fitt+ betwe5 ! compass & ! socket-piece1 s t x c>ries ! :ole sup]/ructure ( ! in/rum5t ar\nd ! compass1 its relative position be+ read by ! v]ni]4 ,! edge ( ! compass plate is =m$ into a too!d :eel1 z %[n 9 section 9 ! figure on ! "r-h& side1 into :i* a small :eel or p9ion ,r is fix$ 9 a box ^u ! arm plate t works by means ( a l>ge mill$-head screw ,p4 ,by means ( ?is mill$ head ! in/rum5t may be rotat$ ab\t ! compass1 s t ! l9e ( division on ! compass /ep read+ into ! v]ni] p]=ms ! functions ( ! horizontal limb ( a !odolite4 ,9 ?is mann] angles may be tak5 by means ( ! v]ni]1 q irrespective ( ! read+ ( ! ne$le4 ,:5 ! compass is set to ! z]o ( ! v]ni] at nor? 7#cfj7 x may be fix$ 9 ?is position by means ( a p9 fitt+ 9 opposite holes to ! arm plate & bottom plate ( ! compass1 n %[n2 & :5 ?us fix$ ! ne$le only is us$ z 9 ! pla9 dial4 ,betwe5 ! coll>-piece ,c & ! socket-piece ,a a w$ge-%ap$ lift raises ! ne$le (f its c5tre by press+ 9 a slide %[n at ,l4 #ejf4--,! ,v]tical ,arc is erect$ ^u ! limb z close z possible to ! compass-box1 s z to leave room = a level to be plac$ betwe5 ! seat+s ( ! arc & sights4 ,! axis ( ?is arc is a simple h+e jo9t1 br\ght d[n ne>ly to ! surface ( ! cov] :i* protects ! glass ( ! compass-box3 ?is is done to keep ! in/rum5t z l[ d[n z possible4 ,! telescope1 :i* is ( ! same k9d z t us$ = ! !odolite1 trav]ses ! arc tang5tially1 p]mitt+ x to be adju/$ = read+ ! arc by its v]ni] by means ( a clamp & tang5t motion at any position4 ,! arc is divid$ on "o side into degrees1 & reads by ! v]ni] to #c 9 ! same mann] z ! horizontal circle4 ,on ! opposite side x is divid$ ) a p]c5tage scale ( diff]5ce ( hypot5use & base :i* reads to an index l9e4 ,a _s level is plac$ "u ! telescope1 9 l9e ) its axis1 to :i* x is adju/able by means ( cap/an-head$ screws4 ,! telescope :5 fix$ is plac$ j suffici5tly above ! arc to p]mit x to be br\ght to a v]tical position at #ij1 or a degree or two ov] ?is1 ) ! full ap]ture ( ! object-glass beyond ! extreme edge ( ! horizontal circle4 ,by ?is con/ruction a be>+ may be tak5 ( any object ^u ! surface f ! top ( a %aft1 & a l9e may be sight$ to ! bottom ( ! %aft 9 exact azimu? ) ?is )\t *ang+ ! horizontal adju/m5t ( ! in/rum5t4 ,9 ! same mann]1 if ! v]tical axis be p]fectly adju/$ by ! level on ! v]ni] plate1 ! telescope at #ij n w indicate a p]fect v]tical to ! /ation ( ! in/rum5t above1 ! n be+ ! all[ance to be made = ! ecc5tricity ( ! telescope1 provid$ ! collimation is p]fect4 ,if ?is is n p]fect1 ! v]tical may /ill be tak5 accurately by means ( ?ree obs]vations tak5 f equal division ( ! entire horizontal circle1 say at #cfj1 #abj & #bdj4 #ejg4--;,x w be notic$ t ! v]ni] to ! compass circle comes directly "u ! v]tical arc1 !re=e x c only be read obliquely :5 ?is arc is m\nt$3 ) op5 sights ! v]ni] c be read directly4 ,?is is a defect 9 ?is in/rum5t1 z ! v]ni] is mo/ly requir$ = exact "w :5 ! telescope is us$4 #ejh4--,lean's dial possesses ! qualities #a & #d1 po9t$ out 9 art4 #dij z important to dials2 9 #d ! p[] ( sett+ ! telescope to ! v]tical ) great facility be+ ! mo/ important4 ,?is quality has kept ! dial a fav\rite ) _m m9+ eng9e]s 9 m9]al di/ricts = _m ye>s4 ,o!rwise = g5]al "w ! compass is mo/ inconv5i5tly ob/ruct$ by ! arc above x1 & ! in/rum5t1 al?\gh1 ( c\rse1 ( less height ?an ! !odolite1 "s ( ! functions ( :i* x p]=ms indiff]5tly1 is too high to be us$ 9 %all[ work+s4 ,! height ( a #e-;in* ,lean's dial to ! c5tral apex ( ! telescope is #i in*es2 to ! top ( ! sights plac$ 9 a level position1 #h in*es2 weight ( in/rum5t only1 #f lbs4 ,! #f-;in* in/rum5t is ab\t #a in* high]1 & weighs #a lb4 m4 #eji4--;,a numb] ( v>iations h be5 made 9 ,lean's dial2 b none t ! au?or is aw>e ( has prov$ successful4 ,9 an in/rum5t ( ?is class1 design$ by ,mr4 ,j4 ,:itelaw1#ba ! v]tical arc is br\ght d[n to ! compass-box by plac+ pivots on ea* side ( ! box aft] ! mann] ( ,h$ley's dial1 to be next describ$4 ,?is l[]s ! in/rum5t ab\t an in*1 & is an improvem5t2 b ?is is effect$ at ! exp5se ( plac+ a /rid+ b> across ! compass box1 :i* is a great imp$im5t to ! cle> sight+ ( ! compass4 ,messrs4 ,newton ,son h made ! telescope to deta* f ! arc ( ,lean's dial to be plac$ directly ^u ! limb4 ,9 ?is way !y claim = x t x comb9es a m9]'s dial & dumpy level4 ,! arrangem5t appe>s to ! au?or to make ! in/rum5t top heavy z a dial1 & to give too little p[] = a good level1 add$ to :i* x co/s ab\t ! same z ! two sep>ate in/rum5ts ( equal quality4 ,( c\rse any telescopic dial may be us$ z a level by clamp+ x at z]o4 ,practical surveyors g5]ally object to comp\nd in/rum5ts t entail _m loose pieces4 ,^! 7 a fa%ion 9 ! middle ( ! n9ete5? c5tury4 #eaj4--;,exam9ation ( ,lean's ,dial4--,z reg>ds ! /&1 sights & p>allel plates1 p>ticul>s h be5 giv5 ^u ! pla9 dial j describ$4 ,! revolv+ compass %\ld be turn$ r\nd by ! mill$ head ,p1 ,fig4 #bjg1 ( ! p9ion :eel ,r to see t ! compass-box revolves /eadily at all po9ts )\t di/urbance ( ! ne$le4 ,x may also be p>ticul>ly obs]v$ t ! ne$le does n oscillate at any "p ( ! circle1 to be sure t ! compass-box is q free f iron4 ,! v]ni] %\ld be exam9$ at f\r opposite positions ( ! ne$le to see t ! ne$le is truly c5tr$ & is 9 accord ) ! v]ni]4 ,! lift] %\ld be tri$ to see t x l[]s ! ne$le g5tly on ! c5tre1 & t x holds ! ne$le firm (f ! c5tre4 ,! telescope %\ld be set up & direct$ to an object1 & all p>ts ( ! in/rum5t clamp$ & ! ne$le obs]v$4 ,! telescope %\ld !n be deta*$ & ! sights set up1 to see t !y range fairly ) ! telescope4 ,if !y d n d s ! diff]5ce %\ld be not$ & treat$ z a con/ant 9 any case ( *ange f telescope to sights on ! same survey4 ,! diff]5ce ought to be v small1 o!rwise ! in/rum5t %\ld be return$ to ! mak]4 #eaa4--,! ,adju/m5t ( ,lean's ,dial is ! same z t ( ! pla9 !odolite1 s f> z ?is c be c>ri$ out2 b g5]ally ! adju/m5t is dep5d$ ^u z x leaves ! manufactur]4 ,= ! g5]al use ( ?is & o!r dials "s notes w be made fur!r on1 b z reg>ds v]tical position & ! tak+ ( azimu? angles1 = :i* ?is dial is specially adapt$1 notes may be made "h4 #eab4--,to set a l9e 9 ,azimu? ) "o tak5 above ,gr\nd4--,?is is necess>y :]e !re is local attraction to ! ne$le bel[1 or !re is a suspicion ( ?is1 s t ! ne$le _c be dep5d$ ^u ) c]ta9ty4 ,! in/rum5t is plac$ on /ag+ ov] ! pit & a v]tical is tak5 to its c5tre ei!r by ! means briefly discuss$ art4 #ejf by ! in/rum5t1 or by susp5d+ a plummet1 a ball1 or a bullet f ! c5tre ( ! in/rum5t by a ?read & burn+ ! ?read :5 ! ball is free f vibration4 ,! ball is all[$ to fall ^u a smoo? horizontal surface =m$ ( e>? or o!rwise1 9 :i* x makes a d5t :i* w be v]tical to ! axis ( ! in/rum5t if ! ball has n be5 deflect$ by v5tilation curr5ts4 ,two lights1 z di/ant z possible to be se5 to range 9 l9e ) ! d5t1 are plac$ at ! bottom ( ! pit4 ,! lights1 if ?\ght desirable1 may range nor? & s\? ) ! ne$le2 b 9 :atev] direction ?is may be set ! correct azimu? ( ?is may be tak5 by cutt+ !m by ! webs ( ! ne>ly v]tical telescope ( ! dial2 & ?is azimu? may be correctly set out on ! surface by a pole or o!r /ation m>k1 or its true direction by a pair ( ^!1 "o on ea* side ( ! pit's m\?1 ! second /ation m>k be+ set out aft] a %ift ( ! horizontal v]ni] exactly #ahj on ! circle4 ,a /raight-edg$ floor+ bo>d pa9t$ :ite may be made to cut ! l9e f light to light1 :i* is m def9ite = be>+ ?an ! lights !mselves4 #eac4--;,h$ley's ,dial1 ! inv5tion ( ,john ,h$ley1 ,h4,m4 ,inspector ( ,m9es1 9 #ahej1 has n[ become ! mo/ popul> =m ( m9]'s dial1 modifi$1 h[ev]1 f its orig9al =m 9 v>i\s ways4 ,! peculi> feature ( ?is =m ( dial is t ! sights move ^u a framework c5tr$ ^u a horizontal axis1 s t !y may by a rock+ motion take horizontal angles )9 a wide azimu? )\t ob/ruction to ! sight ( ! compass4 ,illu/ration3 ,fig4 #bjh4--;,h$ley's dial4 #ead4--;,= consid]ation ( ! g5]al features ( ,h$ley's dial1 ! tripod & ! ball & socket are ! same z t describ$ = ! pla9 dial2 b ! socket is n cut d[n on "o side to *ange ! position ( ! axis1 z ! compass-box 9 ?is in/rum5t is requir$ to be kept uni=mly level4 ,! g5]al appe>ance is %[n ,fig4 #bjh4 ,= di/ricts 9 :i* ! work+ /rata are fairly level1 p>allel plates are put to ?is in/rum5t 9 place ( ! ball & socket jo9t4 ,! compass-box revolves1 z t describ$ = ,lean's dial2 b x is m g5]al 9 ?is in/rum5t to h a clamp & tang5t motion1 z 9 a !odolite1 ?an ! rack & p9ion motion4 ,two levels = sett+ ! compass horizontal are sunk into ! plate ( ! compass-dial l[ en\gh to miss ! edge-b> ne$le4 ,! /ep ( ! compass is divid$ into degrees & ! plate ( ! dial to #aj4 ,! v]ni]1 :i* is plac$ on ! opposite side ( ! box to ! v]tical arc1 reads to #c1 z describ$ = ,lean's dial4 #eae4--,! ,rock+ ,c5tre =ms ! peculi> feature ( ,h$ley's dial4 ,f opposite po9ts ( ! "u side ( ! compass two pivots are project$4 ,^! are set p]p5dicul> to ! v]tical axis1 :i* is plac$ above ! ball & socket4 ,! pivots are plac$ c5tral ) ! v]ni] & 9 l9e ) ,e4 to ,w4 ( ! compass :5 ?is is set to z]o 7#cfj74 ,! pivots =m ! axes ( a /\t r+--rock+ r+--:i* surr\nds ! compass-box1 ) space suffici5t to cle> x :5 ! r+ is rock$ ab\t its axis4 ,! r+ has two ext5d$ arms :i* c>ry sights z %[n4 ,^! turn d[n ^u ! compass-box :5 out ( use4 ,"o ( ! pivots is prolong$ = ab\t in* beyond ! out] circumf]5ce ( ! r+4 ,! prolongation is made g5]ally ( triangul> section4 ,?is =ms a fitt+ to ! v]tical arc1 :i* is atta*$ by a mill$-head$ screw :5 requir$1 ! arc be+ an encumbrance :5 ?is dial is us$ = mak+ horizontal plans only4 #eaf4--,! ,v]tical ,arc1 ) its index arm1 =ms a sep>ate piece4 ,! arm is c5tr$ ^u ! arc ) a gr\nd fitt+1 :i* is reta9$ 9 its position by a coll> fix$ ) ?ree screws4 ,! arm-piece =ms ! axis1 ?r\gh ! c5tre ( :i* a triangul> hole is made to fit ! triangul> prolongation ( ! pivot1 s t ! index arm rema9s fix$1 & ! arc moves ) ! rock+ r+1 to :i* x is held by a pair ( d[els4 ,! arc is divid$ into degrees on ! out] edge ( its surface1 & a scale ( diff]5ce ( hypot5use & base ^u its inn] edge4 ,! graduations read to a s+le index l9e ^u a fiducial edge c>ri$ d[n f an op5+ 9 ! index arm4 ,h$ley's dial c be lock$ by a p91 :i* is atta*$ to ! "u side ( ! compass-box1 s z to "w by ! compass only4 ,! r+ c also be lock$ level ) ! compass by a sl+ lat*-piece s z to conv]t x into a pla9 dial4 #eag4--,! great m]it ( ,h$ley's dial is t ! rock+ c5tre p]mits a great] range ( op5 sight+ ?an any o!r2 & ! in/rum5t is v l[1 p]mitt+ its use 9 %all[ work+s4 ,fur!r1 t x is a v /rong in/rum5t to resi/ accid5ts1 & is v portable4 ,! height ( a #f-;in* ,h$ley's dial above ! tripod head1 9 a level position1 is #i in*es to ! top ( ! sights4 ,weight ( in/rum5t1 #g to #aj lbs4 ,illu/ration3 ,fig4 #bji4--;,h$ley's dial ) ball clamp4 #eah4--;,9 ! au?or's simple dial1 ,fig4 #bji1 :i* is ( a mod]n =m1 ! ball is clamp$ by a capp+-piece ov] x mov$ to clamp by two /\t p9s4 ,?is =m gives a little less height & /ill holds ! dial firmly4 ,! horizontal axis moves r /iffly1 s t no clamp to ! arc is requir$4 ,x is a v *eap =m ( dial1 b sub/antially made4 ,x answ]s = a small m9e survey4 #eai4--,!re h be5 _m v>iations made & propos$ = ,h$ley's dial4 ,mr4 ,cas>telli1 ( ,man*e/]1 places ! arc ov] ! c5tre ( ! compass-box4#bb ,?is plan is int5d$ to make ! rock+ c5tre firm2 b ! arc int]f]es a little bo? ) ! sights & ! view ( ! compass box4 ,messrs4 ,davis & ,son connect :eel-"w ) ! arc1 s z to magnify ! scale ( motion4 ,o!r less important v>iations 9 ,h$ley's dial are common4 #ebj4--;,exam9ation & ,adju/m5t ( ,h$ley's ,dial4--,! g5]al exam9ation ( ! /& & ( su* p>ts ( ! in/rum5t z correspond ) ,lean's dial is ! same z j giv54 ,! rock+ r+ %\ld be lift$ & press$ d[n at ea* end alt]nately to see t !re is no loss ( "t on ! axis4 ,! arc %\ld be exam9$ 9 l mann]4 ,! dial %\ld be set up 9 front ( a plumb$ l9e to see t its sights range prop]ly :5 ! in/rum5t is set level by its bubbles4 ,a po9t %\ld be obs]v$1 say ?r\gh ! hole & cross webs at ! top ( ! sight2 & ) ?is po9t kept 9 view ! rock+ r+ %\ld be mov$ upw>ds or d[nw>ds s t ! po9t trav]ses ! plumb-l9e to ! ext5t ( ! rock+ motion4 ,if x does n d s1 possibly ! transv]se level 9 ! plate ( ! compass-box may be adju/$ to make x d s2 b 9 ?is adju/m5t x mu/ be p>ticul>ly obs]v$ t ! balance ( ! ne$le rema9s s t x /ill reads ! graduation ) its upp] edge1 & t ! sights trav]se ! same plumb-l9e :5 turn$ ab\t1 z x is possible to set ! level "r ) "o pair ( sights & ?r[ o!r p>ts out4 ,!re are no simple means ( adju/m5t provid$1 s t if ! in/rum5t is n accurate x %\ld be return$ to ! mak] = correction4 #eba4--;,improvem5t 9 ,h$ley's ,dial1 by ,addition ( ,telescope4--,surface "w be+ g5]ally p]=m$ ) ! !odolite1 survey+ ) op5 sights foll[+ ?is _c be effect$ ) suffici5t accuracy2 !re=e !re becomes a necessity = ! use ( ! telescope1 :i* 0 fir/ plac$ on ?is in/rum5t by ! au?or at ! sugge/ion ( ,mr4 ,w4 ,preece1 ,c4,e4 ,9 m9es1 also1 al?\gh sights pres5t (t5 ! only possible means ( direct+ angul> positions 9 cramp$ & tortu\s work+s1 on ! o!r h&1 bett] "w c v (t5 be done & ! telescope be conv5i5tly us$4 ,"u ^! conditions1 ?is addition =ms an important improvem5t 9 ! in/rum5t1 to be at h& to apply :5 desir$4 ,! telescope ( ?is in/rum5t deta*es exactly z ) ,lean's dial1 b ! sights are made ) an angle piece1 s z to ext5d !m to a di/ance ( ab\t #ab in*es ap>t = sight+4 ,fig4 #baa is ( "o crank$ sight4 ,! in/rum5t illu/rat$ ,fig4 #baj has p>allel plates1 art4 #aic1 p4 #ii1 suitable = fairly level work+s4 ,a ball & socket jo9t is sometimes fitt$ to ?is in/rum5t 9 place ( ^!4 ,illu/ration3 ,fig4 #baj4--;,h$ley's dial ) telescope4 ,illu/ration3 ,fig4 #baa4--;,bracket sight4 #ebb4--,! ,telescope is plac$ on ,y's1 & is ( exactly ! same =m z t describ$ = a pla9 !odolite4 ,! ,y's 9 ?is in/rum5t (f] a great conv5i5ce = rev]s+ ! telescope = back sights 9 range :5 ! v]tical axis is fix$4 ,! level "u ! telescope is suffici5tly good to conv]t ?is in/rum5t into a level = dra9age1 etc41 :5 ! rock+ r+ is lock$ ) ! compass4 ,its exam9ation & adju/m5t are ! same z ^? la/ giv51 except = ! telescope1 :i* is ! same 9 all p>ticul>s z t ( a #e-;in* pla9 !odolite4 ,illu/ration3 ,fig4 #bab4--;,improv$ m9]'s dial4 #ebc4--;,improv$ ,m9]'s ,dial4--,! illu/ration giv51 ,fig4 #bab1 is ( ! =m ( dial introduc$ by ! au?or1 a "p ( ! arrangem5t only be+ ( 8 own design4 ,! telescope ) ,y supports is ! same z t j describ$1 & ! sights1 n %[n1 are crank$ 9 ! same mann] z %[n ,fig4 #baa4 ,! horizontal circle1 in/ead ( be+ 9 ! int]ior ( ! box1 is plac$ on ! ext]ior rim1 & reads ) two v]ni]s--n = correction1 b = conv5i5ce ( read+ 9 diff]5t positions4 ,! compass is divid$ ^u ! upp] surface ( ! /ep to degrees1 & 9 ! same mann] on ! int]ior cyl9drical surface ( ! /ep4 ,?is la/ (t5 p]mits ! compass to be read 9 a close work+ :5 ! upp] surface c\ld n ei!r be light$ or sight$4 ,?is plan 0 us$ on old circumf]5tors4#bc ,! plane ( ! compass is divid$ to #aj z usual4 ,! compass adju/s by clamp & tang5t motion4 ,! axis ( ! in/rum5t is support$ ^u a ball & socket arrangem5t design$ by ! au?or = r\ghly br++ ! compass to level1 & a p>allel plate adju/m5t = f9al sett+4 ,! ball is fix$ by clamp+ a pair ( plates toge!r by a ?umb-screw4 ,ea* plate is holl[$ 9 ! c5tre to hold ne>ly half ! ball4 ,:5 fix$1 ! in/rum5t is f\nd to be v rigid4 #ebd4--;,a plan ( clamp+ design$ by ! au?or to meet ! conditions ( ! tribra* sy/em ( adju/m5t ( equal rigidity to t above describ$1 is %[n 9 elevation1 ,fig4 #bac ,b4 ,9 ?is ! upp] half ( ! socket is screw$ d[n outside ! l[] half socket by means ( ?ree project+ h&le p9s4 ,?is is a some:at neat] arrangem5t ?an t %[n 9 ,fig4 #bab4 ,ei!r ( ! above-describ$ ball arrangem5ts elevate ! in/rum5t1 & are bett] omitt$ = close work+ if !re is a special adju/m5t 9 ! tripod atta*$ to ! in/rum5t1 z t to be describ$ pres5tly1 :i* w be f\nd suffici5t 9 mo/ cases4 ,! height ( ! in/rum5t f ! tripod is ab\t #f in*es2 weight1 #aa lbs4 = bo? p>allel plate & tribra* adju/m5ts4 #ebe4--;,adju/able ,tripod = ,dials4--,! au?or's improv$ =m ( tripod is adju/able to all heights betwe5 #cj in*es & #eg in*es1 ,figs4 #bac1 #bad4 ,ea* leg is =m$ ( two /iff b>s ( mahogany1 %[n 9 detail1 ,fig4 #bad ,g ( section1 ab\t #a in*es by #e_/h in*1 & a ?ird b> or leg ,g ( ab\t #a in*es squ>e1 :i* slides betwe5 ! o!r two4 ,! slid+ surfaces are groov$ & tongu$ toge!r 9 ,v grooves 9 ! solid4 ,two /rap-pieces ( brass ,,ss are fix$ ne> ! ends ( ! b>s4 ,"o ( ^! ,s is firmly sold]$ to a boss-piece t takes a ?umb-screw1 :i* has q suffici5t p[] to hold ! leg ,g firmly at any position ( ext5sion4 ,x is a rigid /&1 :i* may leave ! tripod head ne>ly v]tical ^u any incl9ation ( ! floor surface4 ,illu/ration3 ,fig4 #bac4--,! au?or's adju/able ball jo9t & socket tribra* /&4 ,illu/ration3 ,fig4 #bad4--;,adju/m5t to leg ( tripod4 #ebf4--;,h$ley's ,dials1 ) ,pa/orelli's & ,h(fmann's ,ball ,arrangem5ts4--,by ei!r ( ^! arrangem5ts ! ball & socket is br\ght d[n close into ! p>allel plate adju/m5t s t ! dial is ( less total height4 ,h(fmann's is n[ becom+ ! mo/ popul> sy/em1 z practice has %[n x to be ! mo/ p]fect = m9+ survey4 ,by ei!r ( ^! arrangem5ts ! ball & socket is clamp$ by ! same screws t br+ ! in/rum5t to f9al position4 ,9 ,pa/orelli's arrangem5t#bd ! socket is drawn d[n ^u ! ball by ! adju/+ screws4 ,9 ,h(fmann's#be ! ball is press$ up into ! socket1 :i* is ! exact me*anical equival5t4 ,:5 ! screws are lightly clamp$ ! ball c be mov$ ) mod]ate =ce1 or ev5 q loosely by c>eful adju/m5t2 & 9 ei!r case1 :5 ! ball is once set1 c>e mu/ be tak5 to keep pressure con/antly ^u x dur+ ! f9al adju/m5t by ! screws4 ,! g5]al arrangem5ts are %[n 9 two ,figs4 #bae1 #baf1 :i* are tak5 f ! draw+s ( ! respective pat5ts4 ,9 ,fig4 #bae1 va1 ! axis ( ! in/rum5t t]m9ates 9 a ball e :i* works 9 a cup f4 ,! axis has also a portion ( a ball ( great] radius b conc5tric ) ! l[] ball e4 ,! upp] p>allel plate d is cupp$ ov] ?is ball4 ,:5 ! p>allel plate is mod]ately free on b1 ! axis va may be set to any angle )9 ! range ( ! c5tral op5+ ( d2 & z ! friction ^u bd is great] ?an t ^u fe1 ! axis moves by ! adju/m5t ( ! p>allel plate screws aa4 ,9 ,fig4 #baf ! action is precisely ! same1 except t ! pressure is upw>ds in/ead ( d[nw>ds4 ,9 ,fig4 #bae !re are spr+s s "u ! p>allel plate screw heads to keep contact :5 ! screws are loos5$4 ,9 ,fig4 #baf ! spr+ is a plate "u ! screws s1 ! action be+ ! same 9 bo? cases4 ,illu/ration3 ,fig4 #bae4--,pa/orelli's ball & socket adju/m5t4 ,illu/ration3 ,fig4 #baf4--;,h(fmann's ball & socket adju/m5t4 #ebg4--,"s objections h be5 made to ?is class ( arrangem5t1 ov] ! simpl] "o ( clamp+ ! ball indep5d5tly & !n adju/+ by ! screws1 z be+ m complex4 ,on ! o!r h& ?is comp\nd arrangem5t has ! m]it 9 und]gr\nd in/rum5ts ( be+ l[] & m compact1 :i* is v important4 ,! au?or has some:at modifi$ ! arrangem5ts ( ,h(fmann's head1 z %[n 9 ! engrav+ on next page1 to r5d] x /ill m compact = m9+ in/rum5ts4 ,illu/ration3 ,fig4 #bag4--;,improv$ ,h$ley's dial1 m\nt$ on ,h(fmann's head4 #ebh4--;,9 ,fig4 #bag an improv$ ,h$ley's dial is m\nt$ ^u an improv$ =m ( ,h(fmann's head4 ,! :ole arrangem5t is v compact1 rigid1 & rapid 9 action4 ,! height ( ?is dial is #i in*es2 ! weight #h lbs4 = a #f-;in* in/rum5t1 9 alum9ium #e lbs4 ,illu/ration3 ,fig4 #bah4--;,improv$ ,h$ley1 ) cradle r+4 #ebi4--;,h$ley's ,dial ) ,crank$ ,rock+ ,c5tre4--,"o defect ( ! ,h$ley's dial1 :i* 9 c]ta9 cases makes ,lean's pref]r$1 is t ) ! rock+ r+ ! sights _c be br\ght v]tical = look+ up or d[n a %aft4 ,! au?or has devis$ a means ( gett+ ov] ?is difficulty by mak+ ! r+ ( cradle =m1 ?us ?r[+ ! be>+ surfaces to suffici5t height to cause ! r+1 :5 ! arc is rais$ to ab\t #ij1 to fall "u ! compass-box & its adju/m5ts1 ,fig4 #bah4 ,?is dial pres5ts possibly ! greate/ ref9em5ts ( ! ,h$ley pr9ciple at ! "t ( its pat5t1 ,no4 #iacd1 #ahih4 ,s9ce ?is date ! revis] has introduc$ a few fur!r ref9em5ts z illu/rat$ at ,fig4 #bai4 ,illu/ration3 ,fig4 #bai4--,/anley's improv$ dial4 ,?is in/rum5t has tribra* levell+ ) quick-sett+ sph]ical l[] plate1 a slid+ tribra* = c5tr+ ov] any desir$ spot1 & full clamp & tang5t motions to bo? horizontal c5tres4 ,! divid+ is ^u silv] on a #f-;in* cov]$ limb read+ by two v]ni]s to s+le m9utes1 fold+ sights int]*angeable ) telescope ,y's1 & ?is dial may be us$ ^u any /ag+ )\t its /&4 ,! some:at peculi> %ape ( ! crank$ rock+ r+ is necessitat$ by ! movem5t ( ! slid+ tribra*1 :i* x has to cle> 9 all positions = read+ v]tical sights4 #ecj4--;,accessories ,common to ,h$ley's ,dials are a v]tical reflector & a diaphragm illum9ator4 ,reflect+ ,cap4--,"o ( ! disadvantages ( ,h$ley's dials ov] ,lean's 0 po9t$ out to be ! impossibility ( v]tical sight :]e ! two la/ describ$ dials are n us$4 ,"s ye>s ago ! au?or devis$ a plan ( obta9+ ?is v]tical sight by reflection by means ( a reflect+ cap1 ,fig4 #bbj1 plac$ ov] ! end ( ! telescope4 ,! cap is =m$ ( a tube :i* fits ! out] surface ( ! object end ( ! telescope4 ,?is is prolong$ suffici5tly to lock x by a d[el 9 correct position aga9/ revolution :5 ! po9ts t are us$ = index 9 ! diaphragm ( ! telescope are v]tical4 ,! tube is cut 9 two & h+$ to turn up1 z %[n 9 two positions ,h & ,h4 ,:5 turn$ up x leaves ! tube op5 = direct vision4 ,a reflector ,r is plac$ 9 ! cap1 & !re is an op5+ bel[ x equal to ! full ap]ture ( ! telescope4 ,x is easy to see t by ?is means a pair ( lights or a l9e may be sight$ up or d[n a %aft1 & ! azimu? ( its direction be reflect$ to foll[ a l9e by slightly rock+ ! telescope ^u its pivots4 ,?is may be done1 h[ev]1 ) m ref9em5t if !re is a clamp & tang5t motion to ! v]tical arc1 :i* is plac$ only on fir/-class in/rum5ts4 ,illu/ration3 ,fig4 #bbj4--,reflect+ cap to m9]'s dial4 #eca4--;,illum9ation ( ! ,diaphragm = obs]v+ ! webs or a po9t1 may be conv5i5tly effect$ und]gr\nd by employ+ a conical r+ reflector 9 front ( ! object-glass4 ,! ap]ture ?r\gh ! cone leaves ! field ( ! object-glass ne>ly free1 z x is only necess>y t ! cone %\ld project 9 front ( ?is = a v small di/ance4 ,?is reflector is plac$ ov] ! object end ( ! telescope :5 x is requir$1 j ! same z ! ray %ade4 ,! v]tical reflector1 ,fig4 #bbj1 goes on ! same fitt+4 ,! reflector ,fig4 #bba ,r may be made ( silv] or plat9um4 ,a light plac$ any:]e opposite ?is1 & p]p5dicul> to ! axis ( ! telescope w ?r[ suffici5t light to %[ ! webs or po9t4 ,sometimes a simple1 pla9 mirror plac$ on an arm b5t ov] to ! c5tre ( ! front ( ! object glass1 9 :i* ! mirror /&s at #de to ! axis1 is us$2 b ?is plan is n s good z t %[n ,fig4 #bba1 z ! light has to be br\ght to face ! mirror q p]p5dicul> to ! axis ( ! telescope1 & ?is process is frequ5tly difficult to accompli% und]gr\nd4 ,illu/ration3 ,fig4 #bba4--;,conical reflector to illum9ate axis ( telescope4 #ecb4--;,cont95tal ,=ms ( ,m9]'s ,dials4--,on ! ,cont95t g5]ally sights h be5 ab&on$ = m9]'s dials4 ,! telescopes are usually ( %ort =m1 ) l>ge object-glass & wide field ( view4 ,! telescope is g5]ally plac$ ecc5trically1 :i* p]mits ! in/rum5t to be made ( v l[ =m4 ,!re is a c]ta9 am\nt ( disadvantage 9 ! ecc5tricity ( ! telescope1 z angles _c be tak5 direct f ! c5tre ( ! in/rum5t b ?is is comp5sat$ = 9 ! plott+ by mak+ ea* /ation a small circle equal to ! am\nt ( ! ecc5tricity ( ! in/rum5t to scale1 & sett+ (f angles tang5tially to ?is1 :i* may be done ) a little m tr\ble ?an t ( plott+ ! angle f a po9t4 #ecc4--;,fr5* ,m9]'s ,compasses4--,fig4 #bbb %[s ! simpl] =m ( ?is in/rum5t4 ,! ne$le is op5 & q free f ob/ruction4 ,! telescope is c5tr$ ab\t level ) ! compass-box4 ,! v]tical axis has clamp & tang5t adju/m5t4 ,! transv]se axis is set entirely by h& z ) ! pla9 dial4 ,! in/rum5t is set up level by its tribra* adju/m5t4 ,! height ) #e-;in* ne$le 9 a level position1 )\t tripod head1 is ab\t #e in*es2 weight ab\t #aa lbs4 )\t ! tripod table4 ,! extremely squat =m ( ! in/rum5t p]mits its use 9 v close work+s1 ) a %ort tripod1 if ! work+s are fairly level4 ,x is us$ also z a *eap =m ( surface survey+ in/rum5t1 consequ5tly x is n g5]ally v c>efully made4 ,z a good in/rum5t ( ! class x _c compete ) t to be next describ$4 ,illu/ration3 ,fig4 #bbb4--;,fr5* =m ( m9]'s dial4 #ecd4--;,x w be se5 by ,fig4 #bbb t ! in/rum5t has no direct connection ) its /& or tripod4 ,?is is g5]al ) all ,fr5* & ,g]man in/rum5ts1 ev5 ) !odolites & survey+ levels1 x be+ ! rule t ! top ( ! tripod %\ld =m a k9d ( table ^u :i* ! in/rum5t is set up4 ,! table is almo/ uni=mly made ( wood1 & is some:at bulky & clumsy 9 con/ruction1 !re=e n v well adapt$ to m9+ survey+1 p>ticul>ly 9 wet m9es4 ,nei!r is ! tribra* sy/em ( adju/m5t1 unless x is supplem5t$ by "s =m ( ball & socket arrangem5t1 or ) adju/able /&4 ,?is subject w be fur!r discuss$ 9 ! description ( sup]ior in/rum5ts pres5tly4 ,illu/ration3 ,fig4 #bbc4--;,fr5* m9]'s transit survey in/rum5t4 #ece4--,m9]'s ,transit ,in/rum5t4--,?is is ! ?odolite s\t]ra9 ( ! ,fr5*1 & is ( a con/ruction v g5]al ?r\gh\t ! ,cont95t--,fig4 #bbc4 ,! compass is plac$ cle>ly 9 view4 ,! v]tical axis has a clamp & tang5t motion to br+ ! compass to exact be>+ if desir$1 or to p]mit survey+ ) ! compass only4 ,! axis has also a clamp & tang5t screw to ! ext]ior divid$ circle1 :i* reads ) two v]ni]s4 ,! telescope is plac$ on ! side ( ! in/rum5t1 & has clamp & tang5t motions to read ! v]tical circle :i* ! v]ni] trav]ses 9 transit4 ,all ! divisions are made /rong to be read cle>ly by lamp-light1 ei!r to #a or #c by ! v]ni]1 z desir$4 ,a second level is g5]ally plac$ on "s "p ( ?is in/rum5t at "r angles to ! "o %[n4 ,! in/rum5t is balanc$ by a c\nt]poise weight to keep its v]tical axis 9 equilibrium4 ,! height ( an in/rum5t ) #e-;in* ne$le is ab\t #f in*es2 ! weight )\t ! tripod table is ab\t #ad lbs4 ,! tripod table is con/ruct$ 9 v>i\s ways by diff]5t mak]s4 #ecf4--,! value ( ! transit pr9ciple appli$ to m9+ in/rum5ts1 = tak+ back & =e sights = hang+ l9es 9 undulat+ /rata1 by simply turn+ ! telescope ov] on its axis1 _c be ov]rat$ = exact "w su* z ! telescope alone c p]=m4 ,fur!r1 ) ?is con/ruction ! incl9ation & diff]5ce ( hypot5use & base = correction ( ! *a9 measurem5ts may be tak54 ,b x is important 9 ! use ( ?is in/rum5t to obs]ve ! side ^u :i* ! telescope is situat$ at ! "t ( obs]vation1 "r or left4 ,= ?is a column %\ld be plac$ 9 ! field-book4 ,z a rule =e sights are tak5 ) ! telescope left2 back sights ) ! telescope "r1 rememb]+ t 9 plott+ all angles are tak5 ecc5trically f ! axis ( ! in/rum5t1 t is1 tang5tial to a small circle :i* repres5ts ! ecc5tricity ( ! telescope accord+ to ! scale us$ 9 plott+4 #ecg4--,! ,tripod ,table ( a sup]ior class ( ,cont95tal in/rum5ts1 :e!r ?is is us$ = surface or m9+ survey+1 is usually made ) "s =m ( adju/m5t to br+ ! upp] surface approximately level be=e sett+ up ! in/rum5t4 ,9 ?is case ! table is made a comb9ation ( wood & metal2 & ! only diff]5ce betwe5 m9e & surface tables is t 9 ! =m] case !re is a jo9t$ arrangem5t = %ort5+ ! legs1 b n 9 ! latt]4 ,! table surface = sup]ior "w is g5]ally adju/$ to approximate level ei!r by a ball & socket jo9t or by a pair ( knee jo9ts plac$ at "r angles to ea* o!r1 ) clamps to hold x firmly :5 adju/$4 ,radial ,v-grooves are commonly made = ! po9ts ( ! tribra*1 & a hole is sometimes made 9 ! c5tre ( ! table = susp5d+ a plummet f ! axis ( ! in/rum5t4 ,!re are _m =ms ( tripod table 9 use1 a modifi$ =m ( "o ( :i* 9 metal w be describ$ fur!r on 9 ! *apt] on plane tables4 ,!re are c]ta9 m]its 9 ?is table arrangem5t ov] connective /&s1 z ! table is conv5i5t to set up fairly level1 & ! in/rum5t ne$ n be expos$ until ! op]ation is complete4 ,on ! o!r h& !re is m risk ( upsett+ & injur+ ! in/rum5t by accid5t :5 loosely plac$ on ! table4 ,!re are1 h[ev]1 s*emes m or less complicat$ to prev5t ?is1 z by a screw fix$ 9 ! tripod head act+ aga9/ a spr+ :i* draws ! in/rum5t con/antly d[n :5 atta*$1 & o!r contrivances1 none ( :i* is p]haps equal 9 simplicity to ,ev]e/'s arrangem5t = ! tribra*1 ,fig4 #aia1 p4 #bgc1 on ?is p>ticul> po9t4 ,illu/ration3 ,fig4 #bbd4--,/anley's improv$ m9+ survey transit4 ,illu/ration3 ,fig4 #bbe4--,/& = ! same4 #ech4--;,improv$ ,m9+ ,survey ,transit4--,! au?or has modifi$ ! =m ( in/rum5t la/ illu/rat$1 reta9+ ! g5]al pr9ciples4 ,9 ,fig4 #bbd ! compass is made l>g] & reads 9 ! inside ( ! /ep z well z ^u ! surface1 :i* is ! only way 9 _m cases t x c be read 9 a close work+4 ,! read+ ( ! horizontal circle is plac$ ne>ly v]tical1 s t x may be se5 cle>ly :5 ! in/rum5t is ne> ! ro( ( ! m9e4 ,! v]tical circle is made small] ?an ! horizontal1 z ?is circle1 z a rule1 is ( less importance1 & x c g5]ally be read m exactly f its conv5i5t position4 ,! arrangem5t also p]mits great] fre$om = ! use ( ! tribra*4 ,! telescope is made ) a mu* l>g] object-glass ?an is usual1 to take a wide field ( view2 !re=e x =ms a good level4 ,illu/ration3 ,fig4 #bbf4--,/anley's m9]'s dial sight4 #eci4--,two pairs ( sights are plac$ ^u ! telescope1 ei!r = r\ghly sight+ an object or /ation1 or to be us$ 9 difficult positions4 ,^! are made on a new pr9ciple1 %[n ,fig4 #bbf4 ,! sights are plac$ 9 two w9d[s1 ea* ( :i* is =m$ ( a ne$le po9t ( plat9o-iridium4 ,9 sight+1 ! po9ts are br\ght ov] ea* o!r1 ! di/ant lamp or object appe>+ betwe5 !m4 ,a %>p po9t gives mu* cle>] def9ition ?an a hair1 z x subt5ds ( itself no angle to ! axis ( ! eye4 ab repres5t ! pair ( sights1 c z !y appe> sup]impos$4 ,?is in/rum5t is v conv5i5tly fitt$ ) subt5se po9ts 9 ! telescope1 by :i* di/ances may be tak5 ) ! au?or's /aff1 ,fig4 #aje1 p4 #aeh1 )\t actual measurem5t1 = ! p>ticul>s ( :i* see next *apt]4 ,! subt5se po9ts are arrang$ to measure ! /aff ei!r v]tically or horizontally4 ,z a rule x w be f\nd ) ?is in/rum5t bett] to take r\gh positions fir/ ) ! po9ts1 & aft]w>ds by ! telescope4 ,! in/rum5t _c be recomm5d$ univ]sally = und]gr\nd survey+1 b x is valuable "u c]ta9 conditions 9 close /rata4 ,its height is #f in*es & weight #ac lbs4 ,fig4 #bbe is an ord9>y tripod1 l t us$ ) a level4 ,?is is pref]r$ by _m m9+ eng9e]s z be+ firm] ?an any jo9t$ arrangem5t1 & is suffici5t = work+ 9 a seam ( fairly equal ?ickness4 ,! legs v>y f #i in*es to ! full height1 #e feet #d in*es4 ,an ord9>y set ( ?ree tripods w\ld be #a foot #f in*es1 #c feet #f in*es1 & #e feet #d in*es4 ,illu/ration3 ,fig4 #bbg4--,/anley's und]gr\nd !odolite4 #edj4--,m9+ ,!odolite4--,?is !odolite is ( ! mo/ conv5i5t =m = und]gr\nd railways1 ,fig4 #bbg4 ,! telescope transits on its axis to be br\ght to a v]tical position4 ,! v]tical axis is pi]c$ s t ab\t #aj ( angle may read bel[ ! v]tical mo/ conv5i5tly by means ( a diagonal eye-piece4 ,! c5tre is support$ ^u a slid+ fitt+ s t x may be displac$ ab\t #a in*es ab\t ! c5tre ( ! tripod & be clamp$ to its position4 ,! horizontal axis is pi]c$ to p]mit ! diaphragm to be illum9at$ by a lamp4 ,! tripod /& is fitt$ ) slid+ legs1 if x is to be us$ = m9e survey1 to adju/ = irregul>ity ( surface ( ! gr\nd & = l[ work+s4 ,! =m ( ! in/rum5t is v compact1 rigid1 & portable4 ,illu/ration3 ,fig4 #bbh4--,/anley's prismatic m9+ compass4 #eda--,prismatic ,m9+ ,survey ,compass4--,?is arrangem5t is design$ by ! au?or = v close work+s4 ,! entire dep? ( ! in/rum5t be+ only #d in*es1 any read+ may be tak5 f "o po9t ( view simultane\sly ) ! obs]vation4 ,! #e-;in* compass1 ,fig4 #bbh1 has a float+ r+ divid$ to half degrees1 & ! read+ ( ?is is reflect$ ?r\gh a prism s t x appe>s directly "u ! =e sight1 to be se5 at ! same "t4 ,! prism has a slight magnify+ p[]1 s t by e/imation a be>+ may be easily tak5 to degree or ne>]4 ,! pr9ciple ( ! compass is describ$ art4 #adh1 ! prism art4 #ee2 b 9 ?is case ! prism is rais$ & has a second l5s "u x1 s t x =ms a k9d ( prismatic ,ramsd5 eye-piece4 ,?is elevation ( ! prism p]mits sight+ "u a c]ta9 am\nt ( d[nw>d incl9ation1 regulat$ by ! height ( ! prism & ! l5g? ( ! back sight1 z well z ! upw>d incl9ation :i* is common to ! use ( prismatic compasses4 ,! mo/ important feature 9 ?is compass is ! mode ( light+1 :i* is effect$ by means ( a l>ge prism1 ,fig4 #bbi ,r1 plac$ "u ! compass-box 9 a squ>e tube1 & a small movable lamp to ?r[ light into x1 ,fig4 #bbh ,l4 ,! float+ r+1 ,fig4 #bbi ,c1 is made ( celluloid1 q transp>5t1 s t ! divisions ^u x are cle>ly read ?r\gh ! small w9d[ 9 ! cov] ( ! compass-box4 ,! =e sight ,w is jo9t$ 9 two folds jj1 s t x ext5ds ! di/ance ( sights to ab\t #aj in*es ap>t 9 use1 & yet folds away closely to ! compass = portability :5 out ( use4 ,on ! ne> sight a cut is made transv]sely to ! slit4 ,a second simil> cut on ! =e sight is made level ) ?is to take levels r\ghly4 ,ab\t #bj are set (f on ea* side ( ! cut on ! =e sight1 s t angles ( altitude may be approximately tak5--al?\gh ! in/rum5t is n well adapt$ to ?is4 ,two levels set at "r angles to ea* o!r1 to be us$ 9 sett+ up ! in/rum5t1 are fix$ "u ! compass-box4 ,weight ( in/rum5t1 #d lbs4 )\t ! tripod /&4 ,illu/ration3 ,fig4 #bbi4--,section ( prismatic m9+ compass4 #edb4--;,hang+ ,compass4--,a v g5]al me?od ( und]gr\nd survey+ 9 m9]al di/ricts ^u ! ,cont95t is by means ( ! hang+ compass2 ?is in/rum5t is !re=e g5]ally f\nd 9 catalogues ( survey+ in/rum5ts 9 ,france1 ,g]many1 & ,italy4 ,! orig9al hang+ compass 0 inv5t$ by ,bal?as> ,rssl] ab\t #affj4bf ,x appe>s to ! au?or to be a valuable in/rum5t = survey+ 9 tortu\s m9]al ve9s :]e sight+ is difficult4 ,! measur+ l9e ^u :i* x is us$ is ei!r a hemp5 or copp] cord or a *a94 ,! compass is hung ^u ! cord or *a91 :i* may be /ret*$ to any po9t out ( sight1 & ! compass w !n indicate ! be>+ ( ! l9e4 ,9 ,g]many two in/rum5ts are us$ simultane\sly--! hang+ compass = tak+ ! be>+1 & a cl9omet]1 compos$ ( a light brass semicircle graduat$ to degrees1 ) a small plummet = tak+ ! incl9ation4 ,illu/ration3 ,fig4 #bcj4--,/anley's hang+ dial4 #edc4--;,hang+ ,dial4--,fig4 #bcj repres5ts a modification ( ! hang+ compass design$ by ! au?or1 by :i* incl9ation may be tak5 simultane\sly ) be>+1 if ! dial c be susp5d$ ne> ! c5tre ( ! l9e or *a9 :]e ! cat5>y curve is p>allel ) its po9ts ( support4 #edd4--;,9 ! con/ruction ( ! in/rum5t a circle ( brass ab\t #f in*es diamet]1 in* wide1 & #a_/h in* ?ick1 has two arms ext5d$ to #ab in*es at ! upp] "p1 on ! end ( ea* ( :i* a hook is =m$ = hang+ ! in/rum5t ^u a cord or *a94 ,^u ! l[] "p ( ! circle a =k-piece1 ) a be>+ clipp+ ! circle1 is atta*$ by two screws4 ,! =k-piece is con/ruct$ to support two axes conc5tric to ! v]tical circle1 9 :i* ! compass-box is susp5d$ mu* above its c5tre ( gravity1 s t x falls by its own weight 9 use to a level position4 ,^u ! edge ( ! compass-box an index is br\ght up ne>ly to ! int]ior surface ( ! v]tical circle1 :i* reads into graduations ^u ?is circle into degrees & half degrees4 ,illu/ration3 ,fig4 #bca4--;,hang+ cl9omet]4 #ede4--;,a ,light ,hang+ ,cl9omet]1 ,fig4 #bca1 %[s ! k9d t is us$ 9 ,g]many1 ( #e in*es diamet]1 graduat$ to degrees1 made ( ?9 brass4 ,x is pack$ 9 ! case ) ! hang+ compass1 describ$ art4 #edb4 ,! ends ( ! semicircle are =m$ into hooks = hang+ on ! l9e4 ,! plummet has a horse-hair l9e1 :i* cuts ! degrees4 ,! cl9omet] may be us$ only :5 ! hang+ dial ,fig4 #bcj _c be susp5d$ ne> ! c5tre ( ! l9e1 9 :i* case ?is light semicircle w cause less deflection ( ! l9e1 & give ! incl9ation approximately4 ,= fur!r details ( ! use ( ! hang+ compass ! read] is ref]r$ to ,mr4 ,b4 ,h4 ,br\gh's admirable "w on ,m9e ,survey+4 ,illu/ration3 ,fig4 #bcb4--;,fr5* semi-circumf]5tor4 ,illu/ration3 ,fig4 #bcc4--,tripod head4 #edf4--,semi-circumf]5tor4--,?is simple in/rum5t c sc>cely be enum]at$ ) m9+ survey+ in/rum5ts1 z x is mu* m us$ = surface "w2 b be+ ( ! class ( circumf]5tors to :i* m9]s' in/rum5ts g5]ally belong1 ?is is ! mo/ conv5i5t place = its description4 ,x has v g5]al use on ! ,cont95t4 ,its con/ruction is v simple1 ,fig4 #bcb4 ,x is support$ on a ball & socket jo9t4 ,! socket is =m$ 9 two pieces1 :i* are clamp$ toge!r to hold ! ball by a w+$-head$ screw4 ,"o pair ( sights is m\nt$ ^u ! extreme ends ( lugs ^u ! limb4 ,! limb is divid$ to half degrees4 ,:5 ! ball is loosely clamp$ ! fix$ pair ( sights may be adju/$ to cut any desir$ object4 ,a second pair ( sights is jo9t$ ^u an axis to move c5trally betwe5 ! fir/ pair4 ,^! are made %ort] to pass )9 ! fir/ pair to any angle ar\nd ! arc1 except ! small angles ) :i* ! sights !mselves int]f]e :5 !y are sup]impos$4 ,! movable sights c>ry v]ni]s to read on ! limb to #b4 ,!re is a small compass atta*$ to ! limb4 ,z a *eap in/rum5t = tak+ angles approximately x is v useful1 p>ticul>ly = workm5 employ$ 9 c>ry+ out "w f draw+s plott$ f a survey by a bett] in/rum5t4 ,! weight ( ! in/rum5t ) #f-;in* circle is ab\t #b lbs42 height above tripod1 #g in*es4 #edg4--,! tripod ( ?is in/rum5t is made ( wood4 ,! head is %[n ,fig4 #bcc4 ,! legs are simply ext5sions ( ! upp] p>ts1 :i* are %[n atta*$ ) bolts4 ,! po9t ( ea* leg has a /eel %oe to prev5t x slipp+ 9 use4 ,! head is turn$ to a cone1 :i* fits into ! socket-piece ( ! in/rum5t & p]mits x to be rotat$ ) mod]ate friction4 ,! head is made ( triangul> section t ! legs may be clamp$ firmly to x4 ,:5 us$ = und]gr\nd "w a sep>ate set ( %ort legs is provid$1 :i* atta* to ! head by ! same bolts4 #edh4--,light+ ,und]gr\nd4--,! old und]gr\nd /ation1 =m$ ( a light$ c&le or lamp1 is n n[ consid]$ good 9 practice :]e surface l& is exactly def9$ by b\nd>ies held by legal clauses & rights4 ,! sy/em ( und]gr\nd survey+ n[ v g5]ally foll[$ is t fir/ recomm5d$ by ,mr4 ,?omas ,bak]1 ,c4,e41 & aft]w>ds fully develop$ by ,mr4 ,h4 ,mackwor?1#bg by :i* a /ation tak5 = angul> directions is =m$ by ! position ( ! c5tre ( a tripod4 ,= ?is sy/em ?ree tripods are provid$ = ea* in/rum5t1 ) head adju/m5t complete4 ,^! tripods are made 9 su* a mann] t ! in/rum5t c be plac$ on any "o ( !m 9 a level position4 ,two lamps are provid$1 ! flame ( ei!r ( :i* w take ! position ( ! v]tical axis ( ! in/rum5t :5 ! lamp is plac$ ^u ! tripod =m]ly occupi$ by x4 ,x is easily se5 t by ?is sy/em =e & back sights or angul> positions c be ext5d$ ) all ! accuracy t ! uni=mity ( ! flame ( ! lamp w p]mit4 #edi4--,m9+ ,survey ,lamp4--,! au?or con/ruct$ ?is lamp f an idea giv5 to him by ,mr4 ,geo4 ,kilg\r1 ,c4,e41 ,fig4 #bcd4 ,x is some:at diff]5t f ! ord9>y =m4 ,its accuracy does n dep5d ^u ! regul>ity ( ! flame4 ,a v]tical axis is =m$ "u ! lamp1 :i* is made to ! same fitt+ on :i* ! m9+ survey in/rum5t is plac$4 ,! lamp is plac$ entirely ecc5tric to ! v]tical axis 9 su* a mann] t a v]tical l9e =m$ by a wire ^u its face may /& c5tral & l9e> ) ! axis4 ,a cross l9e is also plac$ at ! same height above ! tripod head z ! c5tre ( ! axis ( ! telescope or cross sight4 ,by ?is means1 al?\gh ! lamp ?r[s its light broadly 9 "o direction only1 ! cross is a p]fectly def9$ object1 easily pick$ up & br\ght to exact be>+ 9 ! in/rum5t :5 plac$ ^u ano!r tripod4 ,9 conv]t+ ?is lamp f a =e to a back sight x has simply to be turn$ half r\nd on its axis1 :i* is done )\t any displacem5t ( ! relative position ( ! cross 9 v]tical or horizontal directions4 ,:]e ?is lamp is requir$ 9 m9es liable to fire-damp1 x is made on ! safety pr9ciple ( ! ,davy lamp4 ,illu/ration3 ,fig4 #bcd4--,m9+ survey lamp4 ,electricity has be5 appli$ to lamps = survey+4 ,?is plan has be5 f\nd successful :]e a second>y batt]y is us$ t c be *>g$ by a dynamo ^u or 9 ! m9e1 or ) "s ( ! mod]n dry batt]ies4 ,illu/ration3 ,fig4 #bce4--,/anley's complete m9+ outfit4 #eej4--,m9+ ,t>gets4--,! ?ree tripod sy/em has be5 mu* improv$ by ! introduction ( accurate t>gets made specially = ! in/rum5t us$1 & int]*angeable ) ! in/rum5t on ei!r /&4 ,! revis] has design$ sev]al =ms ( ^!4 ,!y are g5]ally us$ ) a m9+ !odolite = high-class m9e survey+1 & ! l[] "p is simil> to ! l[] "p ( ! !odolite !y are us$ )4 ,in/ead ( a horizontal circle1 !y simply support a plate c>ry+ cross levels1 & a pill> c>ri$ up to br+ ! t>get level ) ! optical c5tre ( ! telescope ( ! !odolite2 ?is "p is made to fit ! out] c5tre ( ! l[] "p into :i* x is held by a special clamp4 ,! !odolite is made ) a d\ble out] v]tical c5tre1 & ?is is held to ! l[] "p simil>ly clamp$1 s t ! !odolite & t>gets all lift out ( _! c5tres & int]*ange ) ea* o!r4 ,a complete m9+ set ( ?is description is %[n at ,fig4 #bce4 ,?is =ms a v complete m9+ outfit4 ,x consi/s ( a highe/-class ta*eomet] ) quick sett+ sph]ical l[] plate1 me*anical c5tr+ /age1 auxili>y top & side telescope1 illum9at$ axis1 /rid+ level1 also two t>gets ) quick sett+ sph]ical l[] plates1 me*anical /ages1 cross levels1 & swivell$ sight+ crosses4 ,all ?ree are made ) lift-out c5tres1 :i* are int]*angeable1 & all h base plates p]mitt+ _! use on any /ag+ or fix+ )\t _! /&s4 ,! t>gets are sometimes made to hold c&les in/ead ( ! swivell$ cross1 & sometimes ) pla9 /eel po9ts only4 ,! auxili>y telescope is ! special =m design$ by ,mr4 ,dunb> ,scott1 & x embraces all ! advantages & elim9ates all ! disadvantages ( all o!r types4 ,! p>ticul> feature is its int]*angeability ) top or side positions1 & ! means provid$ to ensure p]fect adju/m5t ) ! m9imum ( tr\ble1 ?us =m+ a m9+ transit :i* w p]=m ) exactness all ! complex functions 9 m9e survey+ & requir+ no correction = ecc5tricity4 ,! auxili>y telescope is provid$ ) a c5tre t may be screw$ to ! ?read$ ext5sion ( ei!r ! transv]se axis or ! v]tical pill>s ( ! ma9 telescope4 ,9 ei!r position x is clamp$ firmly & rang$ quickly into alignm5t ) ! ma9 telescope by two oppos+ screws4 ,! diaphragm ( ! auxili>y telescope has "o web only1 s plac$ t x is v]tical :5 on ! top & horizontal :5 at ! side4 ,illu/ration3 ,fig4 #bcf4--,/anley's ,dunb> ,scott auxili>y4 ,! obs]vation ( /eep horizontal angles is made only ) ! auxili>y on top1 & ( precipit\s v]tical angles ) ! auxili>y on ! side4 ,a c\nt]poise is provid$1 :i* exactly balances ! auxili>y1 s t !re is no /ra9 ^u ! in/rum5t4 ,= v]tical sight+ x is also mo/ useful & accurate1 z by transf]r+ ! l9es ( bo? positions ( auxili>y two l9es are transf]r$ d[n a %aft1 at "r angles to ea* o!r1 :i*1 if produc$1 w int]sect ea* o!r exactly "u ! c5tre ( ! in/rum5t1 & no all[ance or calculation :atev] has to be made to asc]ta9 ! c5tre4 ,! :ole atta*m5t adds v little to ! weight1 ! great] "p be+ ( alum9ium1 & x is pack$ sep>ately 9 ! case s z n to int]f]e 9 any way ) ! in/rum5t :5 n 9 use4 ,9 ,fig4 #bce ! auxili>y telescope is %[n at top2 ,fig4 #bcf %[s x atta*$ at ! side4 #eea4--,pocket ,in/rum5ts4--,a v light pocket in/rum5t has be5 design$ by ,mr4 ,d4 ,w4 ,brunton1 :i* w be f\nd useful2 he t]ms x a pocket m9e transit1 b ( c\rse x has no?+ to d ) a transit4 ,x is design$ = r\ghly tak+ horizontal & v]tical angles1 & answ]s ! purpose ( a prismatic compass1 cl9omet] & ,abney level1 & is v portable1 made 9 alum9ium1 & weigh+ only #h oz4 ,x is %[n at ,fig4 #bcg4 ,illu/ration3 ,fig4 #bcg4--,pocket m9e transit4 ,! cov] is provid$ on its inside ) a mirror1 & ?is acts z a back sight2 x is op5$ out to an angle :i* reflects ! =e sight1 & ! object sight$ & ! read+ ( ! ne$le is !n tak54 ,x is necess>y to hold ! in/rum5t firmly aga9/ ! body & see t x is level sideways by plac+ ! _s level across ! box & br++ ! bubble to ! c5tre ( its run1 :ile any turn+ movem5t %\ld be made by turn+ ! body f ! hips4 ,= v]tical sight+ ! =e sight is us$ z ! back sight1 & ! mirror 9 ! lid mov$ to reflect ! bubble1 ! back sight be+ =m$ by ! hole 9 ! mirror se5 at ! bottom ( ! c5tre l9e1 ! cl9omet] bubble is !n mov$ till ! air bell is se5 9 ! c5tre ( its run & ! v]ni] read+ tak54 #eeb4--;,dip ,compass4--,?is consi/s ( a magnetic ne$le susp5d$ betwe5 c5tres s z to move readily 9 a v]tical plane1 & is %[n at ,fig4 #bch4 ,:5 9 use ! r+ is held 9 ! h& & ! compass-box by its own weight takes a v]tical position2 x mu/ !n be held 9 ! plane ( ! m]idian4 ,9 ?is position ! ne$le :5 unaffect$ by ! attraction ( iron assumes a horizontal position4 ,:5 br\ght ov] any mass ( magnetic iron ore x dips1 & ?us detects ! pres5ce ( su* ore ) c]ta9ty4 ,illu/ration3 ,fig4 #bch4--;,dip compass4 ,if held 9 a horizontal position x s]ves z an ord9>y pocket compass & ?us indicates ! magnetic m]idian 9 ! plane ( :i* x %\ld be held :5 us$ to asc]ta9 dip4 ,,footnotes3 #ai ,plate xiv41 fig4 #e4 ,geometrical ,essays1 ,geo4 ,adams1 #ahjc4 #bj ,proc4 ,m94 ,in/41 ,cornwall1 #ahhc1 vol4 i4 p4 #cag4 #ba ,pat5t ,no4 #aeib1 ,april #ahgh4 #bb ,pat5t ,no4 #aheg1 ,j4 ,l ,cas>telli1 ,may1 #ahgd4 #bc ,illu/rat$ plate xv4 ,fig4 #a41 ,geometrical ,essays1 ,john ,adams1 #ahjc4 #bd ,pa/orelli's pat5t1 ,no4 #bgad1 #ahfc4 #be ,h(fmann's pat5t1 ,no4 #bjhd1 #ahgh4 #bf ,geometria ,subt]ranea1 ,voitel1 #afhf4 #bg ,subt]ranean ,survey+1 ,?os4 ,f5wick1 ,lockwood4 ,,*apt] ,,xii4 ,,in/rum5ts ,,to ,,measure ,,subt5se ,,or ,,tang5tial ,,angles ,,to ,,asc]ta9 ,,di/ances--,,hi/orical ,,notes ,,( ,,! ,,me?od--,,pr9ciples ,,involv$-- ,,/adium ,,measurem5t1 ,,direct ,,& ,,by ,,! ,,ord9>y ,,telescope--,,corrections ,,= ,,refraction ,,( ,,! ,,object-,,glass--,,/anley',s ,,subt5se ,,diaphragm-- ,,anallatic ,,telescope ,,( ,,porro--,,ta*eomet]s--,,/adium--,,field -,,book-- ,,omnimet] ,,& ,,its ,,field-,,book--,,bakewell's ,,subt5se ,,arrangem5t4 #eec4--;,direct ,subt5se ,measurem5t ( ,di/ances1 by an ,in/rum5t1 dep5ds ^u our p[]s ( measur+ ! image ( a di/ant /aff or /adium1 or ! divisions m>k$ !reon z !y appe> at ! focus ( ! telescope4 ,if ! /adium is plac$ at "r angles to ! direction ( "o ( two sight l9es :i* subt5d a giv5 angle1 ! numb] ( units divid$ ^u ! /adium cut by ^! l9es w be proportional to units ( l5g? ( base or cotang5t = a con/ant focus ( ! telescope2 s t if we c measure at a fix$ angle ! numb] ( equal units ( measurem5t ( a /adium correctly1 we c obta9 its exact di/ance2 & :e!r ?is me?od is m or less exact ?an *a9 measurem5t w dep5d entirely ^u ! p]fection ) :i* ei!r ( ^! op]ations may be practically p]=m$4 #eed4--,! ,orig9 ( ! ,inv5tion ( ,subt5se ,survey+ 0 ?\ght to be due to ,wm4 ,gre51 an optician ( ,great ,m\lton ,/reet1 ,london1 :o 0 aw>d$ a premium = its inv5tion by ! ,society ( ,arts 9 #aggh4 ,he publi%$ a pamphlet giv+ a description ( 8 me?od 9 #aggh4bh ,?is subject he press$ ^u ! notice ( pr(essional m5 at ! "t1 & 8 me?od has cont9u$ 9 use 9 ?is c\ntry ev] s9ce4 ,8 refract+ telescope1 :i* alone has rema9$ 9 use1 =m$ "p ( ! !odolite4 ,a micromet] 0 plac$ 9 ! focus ( ! eye-piece ( ! telescope1 :i* revolv$ a qu>t] turn 9 its axis to read angles v]tically or horizontally4 ,he con/ruct$ 8 micromet] ) l9es fix$ at a giv5 di/ance ap>t1 & by a second me?od ) ! l9es adju/able4 ,= ?is adju/m5t a f9e l9e 0 rul$ ^u "o side ( two pieces ( glass4 ,! rul$ sides 7 plac$ face to face1 s z to be at ! same focus4 ,"o ( ! l9es 0 adju/able by a micromet] screw4 ,8 /aff 0 #bj l9ks 9 l5g? by #d in*es 9 wid?1 divid$ decimally into #ajjj4 ,8 description ( ! mann] ( us+ 8 in/rum5t w give a g5]al idea ( work+ ! o!rs :i* h be5 d]iv$ f x--ta*eomet]s1 omnimet]s1 etc4--& ?is is wor?y ( note1 z ! inv5tion1 ?\gh g5]ally attribut$ to him1 0 n 83-- #eee4--,to f9d ! cont5ts ( a field ) ei!r ( ! in/rum5ts describ$1 let ! telescope be plac$ s t ! obs]v] may see all its angles f 8 /ation4 ,if ne> ! c5tre ( ! field ! bett]4 ,! p]son :o c>ries ! scale 7/aff7 is to g all r\nd ! field1 /opp+ at e angle1 & to place ! scale at "r angles to ! axis ( ! telescope 7pass+7 f corn] to corn] 7f "r to left if requir$7 ) ! help ( a signal by ! obs]v]4 ,aft] ! di/ances all r\nd ! field are tak5 7by measurem5t ( ! image ( ! micromet]7 & all ! angles includ$ betwixt !m1 ) ! !odolite1 plot x out 9 ! usual mann]1 e4g41 ) a nonius protractor4 ,describe a circle1 & on ?is circle set (f all ! angles f ! c5tre ?r\gh ea* po9t ^u ! circumf]5ce4 ,set (f ! l5g? ( e l9e by a scale ( equal p>ts4 ,^! po9ts w give ! limits ( ! field1 :i* may be laid out 9 trapeziums1 triangles1 etc41 & measur$ f ! same scale ( equal p>ts4 ,! surveyor w compreh5d h[ easily ! cont5ts ( ! field are f\nd by trigonometrical calculation1 s9ce by ?is me?od !re are two sides & "o includ$ angle giv54 ,! common me?od ( measur+ ) ! *a91 besides ! inaccuracies to :i* x is liable1 does only give ! l5g? ( ! surface ( ! gr\nd betwe5 two objects1 & !re=e n its prop] di/ance1 unless ! surface be /raight & no object to h9d] its be+ measur$ f "o end to ! o!r4 ,h[ (t5 ?is is practicable ,i leave to ! consid]ation ( ^? :o are mo/ accu/om$ to measure l9es1 & d\bt n t ^u ! :ole !y w f9d ! telescope me?od has besides ease1 accuracy1 & univ]sality1 necessity itself to recomm5d x4 ,he po9ts out ! utility ( ! sy/em = levell+1 z bo? di/ance & incl9ation may be tak5 at ! same "t4 ,he f9ds by exp]im5t t ! accuracy ( ! me?od exce$s t :i* he c\ld reasonably expect by calculations d$uc$ f !ory1 by sev]al circum/ances 9 its fav\r be+ insep>able f x4 ,! obs]v]'s /ation is ! c5tre ( circle ^: radius is ! di/ance requir$1 :i* is obta9$ by measur+ ! l5g?1 t is1 ! tang5t or subt5se1 ( ! small arcs ^: limits are def9$ by view+ _! image 9 ! focus ( a telescope betwe5 two po9ts !re plac$1 & mov+ !m up & d[n until !y appe> to t\* ! v extremities ( said limits exactly4 ,! mann] ( see+ is natural & by practice w become habitual1 & !re=e cont9ually approa* ne>] to p]fection4 ,?us may any surveyor 9 less ?an two h\rs take all ! dim5sions ( an irregul> polygon necess>y = obta9+ its area1 if x be z mu* z #hj or #ajj acres & limit$ by tw5ty or ?irty unequal sides4 ,gre5 po9ts out t if ! subt5se angle is tak5 horizontally1 atmosph]ic refraction error is elim9at$4 ,he proposes to use bo? reflect+ & refract+ telescopes4 ,) ! reflector he possibly obta9$ accurate results1 b ) ! refract+ telescope he does n appe> to h recognis$ a con/ant correction :i* is necess>y & important4 ,x has s9ce be5 f\nd t 9 #aggh ! ,dani% ,academy ( ,sci5ces aw>d$ a prize to ,g4 ,f4 ,br&] = a simil> device1 :i* he _h appli$ to 8 plane-table1 six ye>s be=e4 ,its real discov]] 0 ,james ,watt1 :o us$ x 9 #agga = measur+ di/ances 9 ! surveys = ! ,t>b]t & ,cr9an ,canals4 ,9 ,james ,patrick ,muirhead's ,life ( ,james ,watt1 he gives a /atem5t by ,watt himself t he con/ruct$ 8 in/rum5t 9 #aggj & %[$ x to ,smeaton 9 #aggb4 #eef4--,subt5se ,in/rum5ts1 z t orig9ally made by ,gre51 are ( "s =m ( !odolite1 ! telescopes ( :i* are con/ruct$ to measure ei!r ! angle subt5d$ by ! *ord ( a small arc or ! tang5t ( ! same4 ,= conv5i5ce ! tang5t is m g5]ally tak5 ^u a graduat$ /adium or /aff1 :i* is erect$ = measurem5t p]p5dicul>ly to ! horizon1 ! pr9ciple ( :i* is %[n 9 ! foll[+ s*eme3-- ,illu/ration3 ,fig4 #bci4--;,diagram ( tang5tial angle measurem5t4 ,let ,,ac1 ,fig4 #bci1 be a horizontal l9e2 ,,bc a /adium set up v]tically4 ,!n if ! angle ,,bac & ! height ,,bc are kn[n1 ! di/ance ( ,,ac c be easily calculat$4 ,= any int]m$iate di/ance betwe5 ,a & ,c a v]tical w be 9 l5g? proportional to ?is di/ance4 ,let de be at "o-?ird ! di/ance f ,a2 !n ! l9e de w be "o-?ird ! l5g? ( ,,bc4 ,if we divide ,,bc into ?ree p>ts & place ! /adium at fg two-?irds ! di/ance f ,a1 ! angle d,ae giv5 by an in/rum5t subt5d+ a fix$ angle w cut ! /aff at ! second division1 equal to two ?irds ! /aff1 :i* demon/rates ! pr9ciple ( all ta*eomet]s1 ,cleps1 etc4 ,if ! tang5t be made a con/ant equal to ! l5g? ( ! /adium ,,bc1 & ?is /adium be plac$ at ano!r position1 say de or fg2 !n ! angle subt5d$ by its entire l5g? w v>y 9 a mann] t c only be e/imat$ by trigonometrical calculation4 ,9 case ( read+ two di/ant m>ks on ! /adium only = ! subt5se1 ! s+le c5tral web ( ! telescope be+ direct$ fir/ to "o & !n to ! o!r ( ^! webs1 ! di/ance is calculat$ z foll[s3-- ,giv5 ! tang5t ,,bc & ! angle ,,bac1 requir$ ! di/ance ,,ac4 ,let ! angle ,,bac be repres5t$ by ,d2 !n-- ,,ca _/ 7,,cb7 cotan ,d1 or ,,ca ,,cb cotan ,d4 ,r$uc+ by log>i?ms1 we h-- log ,,ca log ,,cb ,l cotan ,d - #aj4 ,= example1 make ,,cb #ad feet1 & ! angle ,d #b #de #ej1 ?us3-- log ,,cb #aadfabh ,l cotan ,d - #aj #acafbfe ---------- log ,,ca #bdfbcic1 or ,,ca #bij feet4 ,! above gives ! pr9ciples foll[$ ) in/rum5ts ( ! !odolite class simply2 b arrangem5ts are made 9 omnimet]s & simil> in/rum5ts to read ! tang5t directly & det]m9e ! height ,,cb 9 equal p>ts1 s t obs]vation ( ! heights ,,bc gives rectangul> co-ord9ates & ?us saves r$uction f degrees ( arc4 ,9 practice ! /aff or /adium is made ( ! greate/ l5g? conv5i5t = portability4 ,) a telescopic /aff1 #ad or #af feet is commonly us$4 ,if a unit tang5t be n employ$1 ! foot is divid$ into #ajj p>ts1 ea* ( :i* p>ts1 ) ! ta*eomet]1 repres5ts #a foot ( ! base1 & ! :ole /aff #adjj or #afjj feet4 ,! ord9>y ,sop) /aff1 art4 #bfc1 answ]s ! purpose1 b art4 #bfh bett]4 #eeg4--,measur+ ,di/ances by ! ,ord9>y ,telescope by ,measurem5t ( its ,focal ,image4--,:5 we apply a refract+ telescope to measure a subt5se angle by webs fix$ 9 ! diaphragm1 vision is n direct z 9 ! s*eme ,fig4 #bci1 b subject to b5d+ caus$ by ! refractive quality ( ! l5s1 art4 #eh1 ! telescopic focus v>y+ ) ! di/ance f ! /aff4 ,?us ) a #ab-;in* telescope !re w be a diff]5ce ( ab\t #be in* 9 ! focus1 :e!r ! /aff is held at #ej or #ejj l9ks f ! telescope2 & ?is diff]5ce ( focus is equal to a diff]5ce ( base or cotang5t betwe5 ! po9ts ,a & ,c 9 ! la/ figure1 s t ^! di/ances d n rema9 proportional to ! fix$ unit ( ! tang5t or /adium4 ,x is important to g c>efully into ?is subject ( ! use ( subt5se webs 9 ! ord9>y telescope1 z ! necess>y correction does n appe> to h be5 recognis$ by ,engli% writ]s on in/rum5ts1 & no d\bt ?is is ! pr9cipal reason t subt5se measurem5t has n be5 m practis$ 9 ?is c\ntry4 #eeh4--;,at ! comm5cem5t ( ! la/ c5tury1 ,rie*5ba*1 a ,bav>ian eng9e]1 po9t$ out a me?od /ill 9 use on ! ,cont95t4 ,! au?or is indebt$ to ! k9dness ( ,"l ,rayleigh = ! foll[+ demon/ration ( ,rie*5ba*'s =mula3-- ,illu/ration3 ,fig4 #bdj4--,subt5se diagram4 ,let ,fig4 #bdj ,,ab s1 ab i1 ,,oa d1 ,ob r4 ,o is ! optical c5tre ( ! object-glass2 ab a pair ( webs at v>iable di/ance r f ,o accord+ to telescopic focus2 f focus = p>allel rays4 ,!n by simil> triangles s_/d i_/r or d rs_/i1 r is f\nd by optical laws to v>y 9 ! proportion ( #a_/r #a_/;d #a_/;f4 ,we may !re=e elim9ate ! v>iable r by sub/itut+ its value r fd_/7d - f71 by :i* we f9d d sf_/i f1 :i* gives ! true correction2 & ! di/ance f ! axis ( ! in/rum5t w be d sf_/i f c :]e c is ! con/ant di/ance ( ! object-glass f ! axis ( ! in/rum5t4 ,x is usual to place ! v]tical axis ( a !odolite c5tral betwe5 ! object-glass & ! diaphragm at sol> focus1 s t ! con/ant c becomes f_/#b4 ,x is se5 t sf_/i repres5ts ! direct subt5se1 :]eas ! refraction1 :i* is a con/ant1 gives f & ! position ( ! object-glass f_/#b4 ,rie*5ba*'s =mula be+ true = p>allel rays is evid5tly also true = any subt5se ) refraction = ! /aff at any di/ance4 ,we may !re=e adopt a plus con/ant ( #a;f1 :i* add$ to ! app>5t subt5se is f\nd to produce no error4 ,?us ) a telescope ( #a foot sol> focus1 & us+ ! decimal sy/em ( notation1 z be=e m5tion$1 if a /adium or di/9ct scale be plac$ at #cja feet di/ance f ! c5tre ( ! in/rum5t1 & ! webs or po9ts ( ! diaphragm be adju/$ to read #c feet #cjj divisions1 e subt5se may aft]w>ds be tak5 z numb] ( divisions read #a feet = di/ance 9 feet4 ,if ! subt5se is to be tak5 9 l9ks or metres ! divid+ ( ! /adium w be to ^! measures1 b ! con/ant rema9s ! same #a feet always4 #eei4--,:5 ! l9e ( sight is incl9$ f ! horizon & ! /adium is held erect--a conv5i5t me?od commonly foll[$ ^u ! ,cont95t--! read+ becomes 9 excess ( ! true read+1 9 ! ratio ( ! cos9e ( ! angle ( ! /adium1 repres5t$ by a l9e tang5t to ! sight-l9e subt5d$ to ! foot ( ! /adium1 z %[n 9 ! foll[+ diagram4 ,illu/ration3 ,fig4 #bda4--;,diagram ( v]tical /adium on an incl9e4 ,?us1 ,fig4 #bda1 let ! portion cut by ! l9es ,,ab1 ,s be ! read+ ( ! /adium2 !n ,s7cos a7 ,s4 ,! incl9$ di/ance is !n equal to 7f_/i7,s7cos a7 f c & ! horizontal projection ( t di/ance or a 77f_/i7,s7cos a7 f c7cos a2 or z f c is small & ! angle g5]ally small also1 f c may be tak5 equal to 7f c7 cos a4 ,!n a7f_/i7,s cos#b a f c4 ,illu/ration3 ,fig4 #bdb4--,/anley's pat5t subt5se diaphragm4 #efj4--,! ,subt5se-diaphragm ( ! au?or1 ,fig4 #bdb1 =ms ! eye-piece ( a !odolite4 ,x has movable indices :i* are sep>at$ accord+ to a scale =m$ by calculation ^u ! data ( ! above =mul4 ,by ?is1 di/ances may be tak5 9 ! horizontal plane = l& ( any incl9ation )\t aft] calculation4 ,?is result is obta9$ by obs]v+ ! angle ( incl9ation upw>ds or d[nw>ds on ! !odolite & sett+ ! micromet] to ?is angle be=e read+ ! subt5se di/ance4 ,! read+ is tak5 by po9ts :i* are arrang$ to measure ! subt5se #a to #ajj1 s t ! ord9>y ,sop) /aff may be us$4 ,! diaphragm at z]o appe>s z an ord9>y subt5se-diaphragm4 ,x may be obs]v$ t ?is diaphragm may be us$ z a good *eck1 z di/ances may be tak5 ov] any irregul>ities ( int]v5+ incl9e & give ! true base = ! entire di/ance4 #efa4--;,if ! mean cont\r di/ance is requir$ f /ation to /ation1 ?is may be tak5 directly by subt5se f ! /aff-read+ held at "r angles to ! axis ( ! telescope4 ,! means ( do+ ?is1 devis$ by ! au?or1 is to place a sight director ( a special =m ^u ! side ( ! /aff1 ,fig4 #bdc4 ,?is small piece ( app>atus is %[n atta*$ to ! /aff4 ,x consi/s ( a small telescope ?ree in*es long atta*$ at "r angles to ! /aff by means ( a dovetail slide fitt+ :5 9 use z %[n4 ,! /aff-hold] sights ! ta*eomet] ?r\gh ! %ort telescope1 :i* c only be se5 to appe> !re9 by mov+ ! /aff until x is approximately at "r angles to ! direction ( ! ta*eomet]4 ,illu/ration3 ,fig4 #bdc4--,sight director = /adium4 #efb4--,! ,anallatic ,telescope4--,9 ?is telescope ! focus is con/ant1 & consequ5tly ! tang5tial measurem5ts indicat$ by ! num]ical qualities subt5d$ by a con/ant angle are directly proportional to ! base1 s t !re is no con/ant to be add$4 ,! inv5tion ( ?is in/rum5t & its mod]n application to subt5se measurem5t 0 due to ,pr(essor ,j4 ,porro1 ( ,milan1 :o put x to practical te/ 9 #ahbc1bi 9 an in/rum5t t]m$ a ta*eomet]4 ,! telescope w be be/ und]/ood by ! foll[+ details3-- ,! object-glass ,o1 ,fig4 #bdd1 is made ( a focus t falls well 9 front ( ! axis ( ! in/rum5t ,,cc1 s t ! rays cross be=e fall+ ^u ! anallatic l5s ,a1 ! optical arrangem5t be+ su* t if ! rays fell direct )\t any refraction !y w\ld rea* ! axis & subt5d angles !refrom inv]sely proportional to ! di/ance ( ! /adium4 ,! object-glass & anallatic l5s are ( ! same focus1 s t ! rays aft] cross+ f equal refraction may em]ge p>allel 9 ! space ,a to ,m4 ,! /op at ,s & at ! axis ,,cc cuts (f ecc5tric rays t w\ld o!rwise give int]nal reflections f ! telescope tube4 ,! eye-piece1 repres5t$ by ,,mf1 may be made to pick up ! image ( ! /adium 9 front ( x ^u an ord9>y webb$ diaphragm or ^u rul$ glass4 ,! diaphragm webs are fix$1 or ! glass surface engrav$ ) ?ree or five horizontal l9es & "o v]tical4 ,! out] horizontal l9es are us$ g5]ally z ! subt5se l9es1 & ! c5tral l9e = levell+ & tak+ altitudes4 ,! v]tical l9e is us$ = triangulat+ on ! surface ( ! gr\nd4 ,illu/ration3 ,fig4 #bdd4--;,diagram ( anallatic telescope4 #efc4--,!re is an adju/m5t made by slid+ tubes to br+ ! object-glass & anallatic l5s )9 mutual focus to ensure ! p>allelism ( ! em]g5t rays & to adju/ magnification4 ,?is is commonly effect$ by means ( a rack & p9ion1 mov$ by a sep>ate key kept 9 ! in/rum5t case1 b :i* %\ld n be t\*$ aft] ! in/rum5t is once adju/$ by ! mak]1 except 9 ! case ( accid5t4 ,x is mu* bett] made )\t ?is rack adju/m5t & p]man5tly fix$ by ! mak]1 z if x has ! adju/m5t x is likely to be tamp]$ ) & ?us defeat its object4 ,! eye-piece adju/s to di/ance f ! object-glass 9 ! ord9>y mann] ( ! survey+ telescope--by rack & p9ion4 #efd4--,! eye-piece ( ! anallatic telescope is g5]ally made ( mu* high] p[] ?an ^? ord9>ily employ$ = levels & !odolites--#be to #cj diamet]s is usual4 ,:]e a diaphragm is us$ ! subt5se l9es are commonly plac$ on a slip ( glass 9 two or ?ree sets1 s t great] magnitude ( image may be tak5 = objects at di/ances ( f #b to #g *a9s ) ! #ad-;feet /aff1 or t ! /aff may be read at great] di/ances ?an #ad *a9s4 ,?is s]ies ( l9es is di/+ui%$ z #ej1 #ajj1 & #bjj1 ,figs4 #bde1 #bdf & #bdg2 s t ) ?is z great a di/ance z #bh *a9s ) a #ad-;feet /aff may be e/imat$1 b ?is is beyond ! safe p[] ( ! in/rum5t4 ,! int]m$iate l9e1 z %[n ,fig4 #bbj1 is valuable 9 all cases = levell+4 ,! advantage ( ! increas$ p[] ( ! eye-piece is m ?an neutraliz$ by ! loss ( light4 ,illu/ration3 ,figs4 #bde1 #bdf1 #bdg4--,subt5se l9es rul$ on glass4 ,illu/ration3 ,fig4 #bdh4--;,adju/able po9t diaphragm ) /adia po9ts4 #efe4--,:ile _m civil eng9e]s are satisfi$ ) a s+le p]c5tage pair ( subt5se l9es ! au?or mu* pref]s us+ ! po9t sy/em1 arts4 #bcg to #bci4 ,9 ?is case ! diaphragm1 z made by ! au?or1 possesses two sy/ems ( adju/m5t2 t %[n ,fig4 #bdh at a = ! s+le po9t = altitudes1 & ! pair ( po9ts sep>at$ by ! spr+ ss = subt5se angles4 ,^! po9ts adju/ by sep>ate screws top & bottom ) a mill$-head$ key f4 ,! two v]ticals are fix$ p]man5tly4 ,^! po9ts are all made ( plat9o-iridium1 :i* possesses ! h>dness & ela/icity ( spr+ /eel1 & is at ! same "t1 z f> z is kn[n1 p]fectly non-corrosive4 ,9 case ( any light du/ or moi/ure re/+ ^u ! po9ts1 x is p]fectly safe to bru% !m lightly ) a s(t camel-hair bru% to clean !m4 ,:]e ! #bjj factor is requir$1 a mean may be tak5 ( two obs]vations above & bel[ ! c5tral po9t4 ,:]e #ej is requir$1 ! v]tical po9ts may be adju/$ to ?is4 #eff4--;,9 adju/+ ! l9es1 webs1 or po9ts to a giv5 subt5se1 ! anallatic l5s may be mov$ to give m or less angul> displacem5t or magnification ( ! image4 ,great] accuracy is obta9able :5 ! /aff is held normal to ! l9e ( sight in/ead ( v]tical4 ,if ! /aff be held incorrectly 9 ! incl9$ position at great angles ( elevation or depression1 ! result+ error is v mu* small] ?an 9 ! case ( an equal v>iation ( ! /aff f ! true v]tical position4 ,:5 adju/m5t is made ^u a di/ant /adium at small angles ( elevation or depression1 ! subt5se ( ! small arc w v>y s little f a tang5t to "o ( its radii t ! "o or o!r may be tak5 )\t s5sible error4 ,! plan orig9ally propos$ by ,gre5 ( plac+ a sight tube ?r\gh ! /adium at "r angles to its face1 z a means ( keep+ x 9 ! *ord ( ! arc1 is z good z any o!r1 b is m cumb]some ?an t describ$ art4 #efa4 ,if ! v]tical /adium be pref]r$1 ?is may be set up by ! small level1 ,fig4 #aji1 p4 #afc4 #efg4--;,x is well to note t ) ! anallatic telescope ! /adium mu/ n be s ne> t ! rays f ! object-glass d n cross 9 front ( ! anallatic l5s or ! subt5se w appe> mu* increas$1 s t !re is a fix$ ne>ness at :i* ?is =m ( telescope c be us$1 say #ej feet4 ,= ?is reason eng9e]s g5]ally pref] an ord9>y telescope1 mak+ use ( ! addition ( a con/ant4 ,! au?or also pref]s ! pla9 telescope1 z be+ m correct accord+ to 8 exp]im5ts :]e ! con/ant is correctly all[$4 ,!re are _m advantages 9 ! use ( a pla9 op5 telescope in/ead ( ! anallatic telescope = ta*eomet]s1 among !m ! foll[+ may be m5tion$4 ,m light rea*es ! eye because !re are few] l5ses2 !re is no int]m$iate l5s requir+ adju/m5t & :i* becomes dirty & b$ew$ & is inaccessible = clean+1 & = ! same dim5sions ( ! telescope great] p[] c be obta9$4 ,a l>g] telescope & ( high] p[] is ( great advantage 9 subt5se measurem5t1 b ! full advantage is n obta9$ 9 ! anallatic telescope4 ,! idea :i* appe>s to be /ill common t an ord9>y op5 telescope w n give accurate results at all di/ances by means ( /adia read+s1 plus ! di/ance ( ! ant]ior pr9cipal focus ( ! object-glass f ! axis ( ! in/rum5t1 is entirely errone\s4 ,:5 a /aff is held at any di/ance 9 front ( ! object-glass ( an op5 telescope1 an inv]t$ image ( ! /aff is =m$ at ! conjugate focus :i* subt5ds an angle at ! correspond+ nodal po9t ( ! l5s1 equal to t subt5d$ by ! /aff at ! o!r nodal po9t4 ,if a diaphragm ) two /adia po9ts or webs be plac$ at ?is conjugate focus ! ratio i_/f ! ratio l_/,d2 :]e i is ! space betwe5 ! /adia po9ts1 l ! height on ! /aff :i* ^! po9ts appe> to int]cept :5 view$ ?r\gh ! eye-piece accurately focuss$ on !m1 ,d ! di/ance ( ! /aff f ! object-glass1 & f ! di/ance ( ! diaphragm f ! object-glass4 ,n[ 9 ?is equation i is a fix$ space1 l is ! obs]v$ height on ! /aff1 & bo? f & ,d are v>iables1 ( :i* x is desir$ to f9d ! value ( ,d4 ,f ! laws ( optics x is also kn[n t #a_/;f #a_/;,d #a_/;,f :]e ,f is ! pr9cipal focal l5g? ( ! l5s4 ,!re=e f ,,fd_/7,d - ,f7 = all values ( ,d4 ,sub/itut+ ?is value ( f 9 equation 7#a7 we get i 7,d - ,f7_/,,fd l_/,d2 & multiply+ bo? sides by ,d1 i 7,d - ,f7_/,f l4 ,d - ,f 7,f_/i7l & ,d 7,f_/i7l ,f :i* is true = all di/ances4 ,b ?is di/ance is measur$ f ! object-glass1 & ! di/ance ,s requir$ by ! surveyor is t f ! axis ( ! in/rum5t1 & x is !re=e necess>y to add t ( ! object-glass f ! axis d4 ,s ,d d 7,f_/i7l ,f d1 & ,f d is ! con/ant ( ! in/rum5t c4 ,s 7,f_/i7l c4 ,:5 ! range is great] ?an t at :i* ! divisions ( an ord9>y levell+ /aff c be cle>ly read ) ! /adia po9ts1 t>get /adia rods or t>gets fix$ to a levell+ /aff are us$4 ,x is usual to use pla9 t>gets fix$ ) _! c5tre l9es at exactly #aj or #bj feet ap>t or o!r conv5i5t di/ance1 & ! angle subt5d$ by ^! is measur$ by a micromet] diaphragm4 ,! revis]1 9 conjunction ) ,mr4 ,c4 ,w4 ,scott1 ,b4,a4,i41 ,a4,m4,i4,c4,e41 has design$ a micromet] diaphragm :i* has be5 prov$ to give v accurate results4 ,x is made to revolve1 s t ei!r horizontal or v]tical /adia rods may be measur$1 & x is fitt$ ) f9e fix$ plat9o-iridium po9ts1 :i* are mu* m satisfactory ?an webs or l9es engrav$ on glass4 ,^! are fix$ on "o side ( ! diaphragm1 two ea* #a_/bjj "p ( ! pr9cipal focal l5g? ( ! object-glass above & bel[ ! axial po9t4 ,on ! o!r side ( ! diaphragm is a movable po9t :i* c be trav]s$ ov] ! fix$ po9ts by a micromet] screw1 e complete turn ( :i* moves ! po9t ov] a di/ance equal to #a_/ajjj? ( ! pr9cipal focal di/ance & ! head ( ! micromet] be+ divid$ into #ajj p>ts1 x reads to ! "o hundr$-?\s&? "p ( ! same2 :ile a small />-:eel records ! numb] ( complete revolutions1 five ( :i* cov] ! space betwe5 any two ( ! fix$ po9ts4 ,9 us+ ?is micromet] ) say a #aj-;foot t>get1 let ! l[] t>get cross-b> be clamp$ to ! level /aff at #b feet1 & ! upp] t>get cross-b> at #ab feet4 ,direct ! axial po9t to ! c5tre betwe5 ! t>gets at #g feet & read ! angle1 !n br+ ! ne>e/ fix$ po9t to ! top or bottom m>k by means ( ! tang5t screw1 & br+ ! micromet] po9t to ! o!r m>k by ! micromet] screw4 ,! micromet] read+ is ! read+ on ! divid$ head plus ! hundr$?s indicat$ on ! />-:eel plus #ejj = ea* includ$ complete space betwe5 ! fix$ po9ts4 ,see :e!r ! micromet] reads up or d[n1 & set ! fix$ po9t to ! l[] or upp] m>k on t>get accord+ly4 ,to obta9 ! di/ance f ! axis ( in/rum5t1 divide #ajj1jjj1 multipli$ by ! l5g? ( ! t>get by ! micromet] read+1 & add ! con/ant ( ! in/rum5t ,s #ajj1jjjl_/x c :]e x is ! micromet] read+1 & l ! l5g? ( ! t>get4 ,! ta*eomet] :i* ! au?or has lately made has a pla9 op5 telescope1 b ?is is ( ! same size z t us$ ^u ! ,porro sy/em1 & consequ5tly x gives mu* m light & bett] def9ition4 #efh4--,ta*eomet]s consi/ ess5tially ( any =m ( !odolite t is provid$ ) means = read+ di/ances by its telescope4 ,/adia "w is simply ano!r "n = ta*eometry1 :i* is d]iv$ f ! ,greek ta*eos 7quickly71 & metreo 7,i measure71 & signifies ! art ( measur+ rapidly4 ,! graduation ( ! arcs & circles ( ^! in/rum5ts is sometimes made ^u ! c5tesimal sy/em1 ! circle read+ #djj grades1 :i* are subdivid$ to half grades to read ) ! v]ni] or micromet] to c5tigrade m9utes ( #ja grade4 ,! c5tesimal sy/em facilitates calculation1 & p]mits a free use ( a log>i?mic slide rule ( a special k9d4 ,9 ,france1 :]e work+ ) ?is sy/em at "o "t became m g5]al1 we h v complete c5tesimal trigonometrical tables adapt$ to ! ta*eomet] publi%$ 9 /]eotype1#cj b x has n ga9$ fav\r1 & v few in/rum5ts are n[ s divid$4 ,a compromise :i* has f\nd a c]ta9 am\nt ( fav\r is ! decimal division ( ! ord9>y degree ( #ij to ! quadrant2 ?is greatly facilitates ! calculation comp>$ ) :at is necess>y ) ! sexagesimal division into m9utes & seconds & ! read+ ( ! v]ni]s is mu* simpl] & less liable to errors4 ,moreov]1 ! m5tal conv]sion ( ! sexagesimal division into decimals ( ! same degree is mu* simpl] ?an ! conv]sion into ! c5tesimal degree ( #ajj to ! quadrant4 ,any in/rum5t divid$ sexagesimally c be conv]t$ by simply *ang+ ! v]ni] if ! divisions on ! limb are degrees or half degrees4 ,! !odolite1 ,fig4 #afi1 ! au?or made specially = a ta*eomet]4 ,any !odolite may be conv]t$ into a ta*eomet] by fitt+ x ) a subt5se diaphragm4 ,a mod]n ta*eomet] %\ld be a high-class !odolite 9 :i* e possible ref9em5t is includ$4 #efi4--,! ta*eomet]1 al?\gh manufactur$ = _m ye>s = export1 has be5 v little us$ 9 ?is c\ntry4 ,! in/rum5t to be describ$1 %[n ,fig4 #bdi1 is ! au?or's late/ patt]n4 ,x is made ) sexagesimal division or +rades1 to read by ! v]ni]s to #bj or to c5tigrade m9utes4 ,! telescope is ( mu* l>g] & ( high] p[] ?an t ( ! ord9>y !odolite4 ,= a #f-;in* in/rum5t ! telescope is ( #aa in*es focus1 ) an object-glass ( #a in*es ap]ture4 ,! eye-pieces are ( ! ,ramsd5 =m ( p[]s #ah & #be4 ,! po9ts 9 ! diaphragm are set to cut #ajj divisions ( ! /adium at #ajj units con/ant ( ! measurem5t int5d$ to be tak51 l9ks1 feet1 or metres4 ,?is precludes di/ant measures1 say ( ov] #ae *a9s1 :]e a #af-;feet /adium is us$1 b !y are made adju/able s t !y may be set1 if desir$1 = any o!r subt5se1 al?\gh ?is is n recomm5d$4 ,x is d\btful :e!r ! subt5se me?od c be consid]$ z reliable at a di/ance ( ov] #aejj l9ks2 or at any rate we mu/ assume t mu* great] accuracy c be obta9$ by divid+ di/ances great] ?an ?is into two by an int]m$iate /ation = obs]vation1 indep5d5tly ( ! additional conv5i5ce ( hav+ ! /aff-hold] )9 easy di/ance ( communication4 ,illu/ration3 ,fig4 #bdi4--,/anley's #f-;in* ta*eomet]4 #egj4--,:]e po9ts are n us$ 9 ! diaphragm or :]e l9es are pref]r$1 ^! may be divid$ ^u glass 9 f9e l9es z ,fig4 #bdf2 or spid] webs may be us$1 b ^! are m difficult to set exact = /adia4 #ega4--,/adium4--,any accurate levell+ /aff w answ] = ! /adium1 b ! ord9>y ,sop)1 ,fig4 #ii1 is slightly confus+4 ,a m op5 read+ is g5]ally recomm5d$--t %[n ,fig4 #ajb1 p4 #aee1 :i* ! au?or design$ = ! purpose1 answ]s p]fectly4 ,x is bett] to read ! /adium l[1 z !re is less vibration2 b x is n (t5 possible or at any "t advisable to read x f ! bottom--#a foot up is g5]ally mo/ conv5i5t4 ,read+s are tak5 & record$ ( ea* subt5se web1 or po9t1 sep>ately1 & ! diff]5ce ( read+ subtract$ = ! subt5se ( tang5t4 ,) a po9t diaphragm = tak+ ! subt5se angle a fair c]ta9ty ( accuracy ( measurem5t ( di/ance )9 #jjb may be assur$1 :i* is mu* ne>] ?an c be atta9$ by av]age *a9+1 tak+ six times ! lab\r4 #egb4--,! ,g5]al ,sy/em ( ,work+ ! ,ta*eomet]1 ) suffici5t detail = practice1 w\ld take too mu* ( our limit$ space to be giv5 "h4 ,we n[ h sev]al good works publi%$ 9 ,great ,brita91 9 addition to ! able pap] by ,mr4 ,br\gh be=e m5tion$1 su* z ,! ,ta*eomet]3 ,its ,!ory & ,practice1 by ,mr4 ,neil ,k5n$y2 ,survey+1 by ,:itelaw2 ,aid to ,survey ,practice1 by ,l4 ,d',a4 ,jackson1 c4 ,!re is a small "w publi%$ 9 ,new ,york giv+ "s details4#ca ,!re are complete works 9 ,fr5*1 ,italian1 ,g]man1 & ,spani%4 ,9 ,fr5*1 ,leves de ,plans a la ,/adia1 by ,m4 ,j4 ,mo9ot1 eng9e] to ! ,p>is1 ,lyons1 & ,m$it]ranean ,railway1 gives v complete in/ructions = all conditions ( c\ntry1 ^u surveys :i* he has p]sonally c>ri$ into practice ) ?is in/rum5t4 ,!re are sev]al ta*eomet]s made ^u ! ,cont95t1 ( m complicat$ =ms ?an ^? h]e9 describ$1 b !y d n produce bett] "w4 #egc4--;,field-books = ! ta*eomet] are rul$ 9 v>i\s ways 9 columns1 :i* v>y 9 numb] 9 diff]5t books f twelve to tw5ty4 ,! ,fr5* g5]ally h f\rte5 columns1 giv+ ! numb] ( ! /ation1 "t1 heights ( l9e ( collimation above po9t levell$1 numb]s ( po9ts select$1 horizontal & v]tical angles obs]v$1 read+ ( subt5se webs & _! diff]5ces1 height ( /aff by read+ c5tral web1 & columns = calculations & rem>ks2 mo/ ,engli% =ms are m simple4 ,illu/ration3 ,fig4 #bdi;a4 #egd4--;,a conv5i5t protractor 9 :i* ! equival5t ( surface read+ is tak5 f a scale ^u its l[] "p direct$ f ! c5tre ( ! protractor is "h %[n4 ,illu/ration3 ,fig4 #bej4--,p]spective view ( #e-;in* omnimet]4 #ege4--,! ,omnimet] is "o ( ! class ( in/rum5ts 9 :i* ! tang5t to a radius proce$+ direct f ! axis ( ! telescope is repres5t$ by ! /adium made ( con/ant l5g?1 ! subt5se angle v>y+ ) ! di/ance4 ,! omnimet] is ! inv5tion ( ,*as4 ,a4 ,c4 ,eckhold1 a ,g]man eng9e]1 describ$ 9 ! provisional ,briti% pat5t#cb z a p]son liv+ 9 ,alex&ria4 ,! in/rum5t z orig9ally devis$ consi/$ ( a k9d ( !odolite to :i* ! subt5se tang5tial sy/em 0 add$ z an entirely sep>ate "p4 ,! important "p ( ! provisional specification %[s t ! pr9ciple ( ! inv5tion consi/s 9 ! use ( two sights to ! in/rum5t1 "o a telescope to sight ! object1 & ! o!r a p[]ful comp\nd microscope to read divisions ^u a tang5tial scale4 ,! telescope & microscope are firmly unit$ toge!r 9 p>allel position ) _! axes exactly cross+ ! transv]se axis ( ! !odolite1 s z to move toge!r ?r\gh ! same angle by ! motion ( ! telescope 9 trav]s+ ! azimu?4 ,a delicate level is plac$ ^u ! telescope1 & :5 ! bubble is 9 ! c5tre ( its run ! scale is truly at "r angles to ! axis ( ! microscope4 ,! scale 9 ! e>ly in/rum5ts /ood v]tically at ! extreme edge ( ! in/rum5t 9 a position lat]al to ! object-glass ( ! telescope4 ,x 0 f9ely divid$ to millimetres1 & read ! int]vals ( ! divisions by means ( a micromet] screw ) a v]ni]4 ,illu/ration3 ,fig4 #bea4--;,details ( omnimet]1 %[+ section ( microscope & scale4 #egf4--,) ! in/rum5t z orig9ally con/ruct$1 x 0 f\nd t ! delicate scale1 protrud+ v]tically to ! extreme edge ( ! in/rum5t1 0 v liable to injury unless support$ by heavy metal "w1 :i* r5d]$ ! in/rum5t cumb]some4 ,a great improvem5t 0 made 9 ?is in/rum5t1 :i* br\ght x to its mod]n =m1 by plac+ ! tang5t scale 9 a horizontal position1 :]e x c\ld be firmly fix$ ^u ! v]ni] plate z %[n ,fig4 #bea ,s1 & read+ ! scale by means ( a reflect+ prism ,p 9 ! eye-piece ( ! microscope4 ,9 ?is improv$ in/rum5t1 z ! microscope & telescope are /ill unit$ on "o axis s t !y move at equal angles to ea* o!r1 x is cle>ly indiff]5t :e!r ! scale be plac$ v]tically or horizontally1 provid$ x is plac$ truly at "r angles to ! microscope :5 ! axis ( ! telescope is horizontal4 ,! scale1 :i* is #d in*es long1 is plac$ 9 a slid+ fitt+ to adju/ longitud9ally to its position by means ( a micromet] screw4 ,9 ! ,engli% in/rum5t ! scale is divid$ into #ajj p>ts = calculation4 ,! divisions are subdivid$ by %ort] l9es1 mak+ ! actual division #bjj4 ,! micromet] screw has #ej ?reads to ! in*1 & moves ov] "o ( ! divisions ( ! scale only4 ,! micromet] head is divid$ into #ajj1 numb]$ at ! t5s2 a v]ni] plac$ aga9/ ! head subdivides ea* ( ^! divisions into #e1 mak+ ! total micromet] #ejj = "o complete revolution4 ,! total division ( ! #d-;in* scale !re=e becomes3 #bjj 7divisions ( scale7 #ejj 7micromet]7 #ajj1jjj 9 #d in*es4 ,! scale is plac$ c5trally to ! in/rum5t1 s t :5 ! telescope is level ! microscope is v]tical1 & reads #ej1jjj :5 9 p]fect adju/m5t4 ,illu/ration3 ,fig4 #beb4--;,details ( prismatic eye-piece4 #egg4--,! g5]al appe>ance ( ! in/rum5t resembles ! transit !odolite1 already describ$ art4 #cfh1 9 e way except = ! addition ( ! microscope & scale1 %[n 9 p]spective 9 ,fig4 #bej4 ,! details ( con/ruction ( ! microscopic app>atus may be foll[$ 9 ,fig4 #bea4 ,t telescope ) s5sitive level ,b m\nt$ ^u x2 ,r body ( microscope connect$ solidly ^u ! same axis z ! telescope1 %[n 9 half section4 ,! eye-piece is plac$ at "r angles to ! microscope & telescope1 & reads ?r\gh ! reflection ( a prism ,p to ! face ( ! in/rum5t4 ,! details ( ! eye-piece are %[n 9 section ,fig4 #beb4 ,! tang5tial scale is %[n 9 section ,fig4 #bea ,s ) ! micromet] ) edge read+ v]ni] at ,m4 ,! compass ( ! in/rum5t ,c is ( ! tr\gh =m1 & plac$ on ! opposite side to ! level to be us$ aft] transitt+ ! telescope f ! position 9 :i* x is %[n 9 ! figure4 ,! axis ( ! connect$ telescope & microscope is exactly #f in*es above ! surface ( ! tang5tial scale ,s4 ,illu/ration3 ,fig4 #bec4--,omnimet] webs2 a telescope1 b microscope4 #egh4--,! telescope diaphragm is g5]ally webb$ ) "o horizontal & two v]tical webs1 ,fig4 #bec a1 ! altitude read+ be+ tak5 f ! top ( ! horizontal web1 & ! horizontal angul> position f ! c5tre ( ! int]val betwe5 ! v]tical webs4 ,! microscope diaphragm b has two horizontal webs1 & reads f ! c5tre ( ! int]val1 :i* is judg$ by ! eye4 ,obs]v$ 9 ?is mann]1 !re is no error due to cov]+ angle subt5d$ by ! webs !mselves4 ,! mo/ exact read+ is obta9$ ) a f9e po9t4 #egi4--,read+ ( ! ,tang5t ,scale4--,z ! micromet] divides half a pr9cipal division into #ejj1 ! complete figur$ divisions are !re=e divid$ into #ajjj4 ,?is is done = ! sake ( decimal notation4 ,9 read+ x is only necess>y to obs]ve t ! %ort] or half division is #ejj1 :i* mu/ be add$ to ! micromet] read+ :5 x is pa/ ?is division2 z = in/ance #fe read+ is #fe1ejj1 & say ! micromet] reads #bcd pa/ ?is1 ! read+ is !n cle>ly #fe1ejj #bcd #fe1gcd1 j z be=e describ$ = read+ half degrees ) ! v]ni]4 #ehj4--,value ( ! ,scale tak5 9 ,rectangul> ,coord9ates4--,! radius f ! transv]se axis ( ! telescope to ! tang5t surface ( ! scale is exactly #f in*es4 ,! scale is #d in*es divid$ into #ajj1jjj p>ts1 z x is read ) ! aid ( ! micromet] & v]ni]4 ,! radius !re=e 9 t]ms ( ! scale w\ld be at #f to #d1 t is #aej1jjj4 ,by ?is we see t ! divisions ( ! scale by ! angle subt5d$ give tang5ts1 ! value ( ea* division ( :i* is ! reciprocal ( ?is on #aej1jjj ( ! radius or base to any unit we may select4 ,if we make ! unit #a foot1 !n "o division repres5t$ by a unit ( *ange ( position ( ! v]ni] read+1 & consequ5tly ( equal angul> *ange 9 ! direction ( ! axis ( ! telescope1 w\ld give a tang5t ( #a foot ^u a /adium plac$ at #aej1jjj feet di/ance4 ,if ! /adium 7 made #aj feet1 z is usual1 ! same angul> magnitude w\ld be trav]s$ 9 t5 times ?is di/ance1 or ov] #bhj miles1 mak+ ! value ( ! units ( ! v]ni] #a1ejj1jjj4 ,?is w give a g5]al idea ( ! delicacy ( ! in/rum5t s f> z con/ructive pr9ciples are conc]n$1 & n its p]=mance4 #eha4--,! ,/adium is m>k$ (f 9 a numb] ( feet1 l9ks1 or metres1 accord+ to ! unit tak5 = measurem5t ( ! surface ( ! l&4 ,! ,engli% /adium is g5]ally =m$ ( a #ad-;feet levell+ /aff1 ) ! surface pa9t$ ) a gr\nd ( pla9 :ite4 ,at #aj feet ap>t two black b&s ab\t #b in*es wide are pa9t$ 91 leav+ 9 ! c5tre ( ea* b& a cle> :ite l9e ( ab\t "o-t5? ( an in* 9 wid?4 ,^! :ite l9es are c>efully set to #aj-;feet /&>d c5tre to c5tre4 ,b a bett] plan is to h two equilat]al triangles pa9t$1 ) _! apices meet+ to ! c5tre4 ,an int]m$iate #e-;feet l9e is drawn 9 black1 :i* is f\nd conv5i5t = ne> measurem5ts1 to avoid too great angul> displacem5t ( ! telescope4 ,:5 ! measurem5t is 9 *a9s1 #ae l9ks or #bj l9ks may be tak5 = ! di/ance ( ! l9es ap>t to give ! tang5t4 ,= metre measurem5t #c metres are commonly tak5 = ! /adium division4 ,^! are 9 ea* case subdivid$4 ,! l[e/ /adium read+ %\ld be #a foot at lea/ f ! gr\nd to avoid grass & o!r ob/ructions4 ,illu/ration3 ,fig4 #bed4--,rul+ ( omnimet] field-book4 #ehb4--;,field-book4--,! field-book z %[n above1 ,fig4 #bed1 0 recomm5d$ by ! inv5tor4 #ehc4--,mode ( ,op]at+ ) ! ,omnimet]4--,c>efully set ! in/rum5t up at its /ation 9 p]fect adju/m5t z a !odolite1 not+ ! dep>ture po9t ^u ! scale read+ ?r\gh ! microscope4 ,place ! /adium 9 a v]tical position at ! po9t to :i* measurem5ts are requir$4 ,direct ! telescope s t ! horizontal web cuts ! upp] l9e ( ! /adium1 & lightly clamp x4 ,n[ read ! microscope & record ! read+ z obs]v$ 9 ! field-book4 ,unclamp ! telescope & take ! read+ ( ! l[] po9t ( ! /aff & record ?is4 ,record ! be>+ ( ! in/rum5t on ! horizontal circle z ) a !odolite4 #ehd4--,to ,det]m9e ! ,horizontal ,di/ance 9 ,feet4--,divide ! con/ant radius ( #a1ejj1jjj giv5 be=e by ! diff]5ce ( ! two read+s ( ! /adium m>k1 :i* are #aj feet ap>t4 ,= example3-- ,fir/ read+ ( scale #fg1ejj1 micromet] #bce #fg1gce ,second #fd1jjj1 #dej #fd1dej ,diff]5ce #c1bhe2 !n #a1ejj1jjj_/cbhe #deff feet di/ance4 ,! process is some:at simplifi$ by log>i?ms1 z we h only ! log4 ( ! diff]5ce to subtract f ! con/ant1 ! #a1ejj1jjj mantissa ( :i* is #a1gfj1iac4 ,?us-- log4 #a1ejj1jjj #fagfjiac log4 #c1bhe1jjj #ceafeced --------- #bfeieeei #deff feet4 #ehe4--,to ,det]m9e ,horizontal ,di/ance 9 ,*a9s ! /adium %\ld be m>k$ z j describ$ = feet1 b at #bj l9ks di/ance f l9e to l9e4 ,!n ! radius #aej1jjj #bj gives #c1jjj1jjj4 ,tak+ = example1 read+s z be=e ) diff]5ce ( #cbhe we h-- #c1jjj1jjj_/cbhe #iacb1 or #i *a9s #acb l9ks di/ance4 ,to ,det]m9e ,horizontal ,di/ance 9 ,metres1 ! /adium is divid$ to #d metres4 ,!n radius #aej1jjj #d #fjj1jjj4 ,tak+1 = example1 diff]5ce ( read+ z be=e #cbhe !n #fjj1jjj_/cbhe #ahbfd metres4 #ehf4--,levell+--,tak+ ,altitudes4--,to take ! elevation ( ! /aff above ! level ( ! in/rum5t1 subtract ! read+ ( ! scale1 :5 ! axis ( ! telescope is level1 f ! l[] read+ ( ! /aff on ! scale1 & divide by ! di/ance diff]5ce1 z f\nd by ! me?od discuss$ be=e1 !n multiply ?is by #aj feet4 ,?us tak+ ! l[] read+ z be=e #fd1dej & ! con/ant = ! level position ( ! in/rum5t1 say #ej1jaj1 we !n h-- ,l[] read+ #fd1dej ,level #ej1jaj ------ ,diff]5ce #ad1ddj !n #ad1ddj_/cbhe #aj #dcif feet ne>ly4 ,! heights1 9 relation to ! position ( ! in/rum5t1 are positive or negative accord+ z ! scale read+s are great] or less ?an ! con/ant level read+ or dep>ture po9t4 #ehg4--,"w ( ! ,omnimet]4--,! p]fection ( ! pr9ciples ( ! omnimet] w\ld lead anyone to inf] t "w might be done ) x ( ! highe/ degree ( accuracy4 ,! te/imony ( ! greate/ au?orities %[ by comp>ison t x is unable to compete 9 ?is respect ) ! be/ made ta*eomet]s4 ,a l>ge numb] ( ^! in/rum5ts are employ$ 9 ,india4 ,colonel ,laughton reports ^u x--,x has be5 f\nd to give v accurate heights ( build+s1 etc41 also to be wond]fully accurate :5 us$ z a levell+ in/rum5t2 b x is n s accurate = measur+ di/ances ov] #fjj feet1 & ev5 at ?is di/ance ! error sometimes am\nts to z mu* z #a foot4 ,x is recomm5d$ z admirably adapt$ = city surveys & trav]s+1 also 9 hilly & jungly c\ntries1 & = railway & simil> purposes4#cc #ehh4--,:]e9 ! in/rum5t fails to give exact results is no d\bt 9 ! difficulty ( its manipulation4 ,= tak+ two read+s1 :i* are necess>y = e op]ation 9 di/ance1 ! in/rum5t has necess>ily to be set twice1 ! h& be+ plac$ ^u ! micromet] = ! second obs]vation :ile ! att5tion is ^u ! sight+ ( ! telescope2 & ev5 :5 ! read+s are tak5 by ! telescope1 ! microscope has to be sep>ately adju/$ to read ! micromet] scale4 ,9 ! repetition ( ^! processes x is almo/ impossible to avoid "s slight di/urbance ( c5tre by pressure4 ,9 di/ant read+s atmosph]ic *anges giv+ diff]5ce ( refraction occur quickly1 s t !re is m risk ( error f two sep>ate obs]vations ?an if ! obs]vations ( ! subt5se webs are tak5 simultane\sly1 z ) ! ta*eomet]4 ,fur!r1 any defect 9 workman%ip or we> tells s]i\sly aga9/ ! read+s ( ! in/rum5t4 ,its advantages are !oretically t a wide angle is subt5d$ by ! /adium ) ! omnimet] 9 %ort di/ances :i* mu/ be 9 e way an advantage4 ,fur!r1 s9ce ! e>ly g5]al use ( ! omnimet]1 ! ta*eomet] has be5 greatly improv$1 p>ticul>ly 9 provid+ x ) a l>g] & bett] object-glass s z to obta9 great] field ( view1 t fairly ne> /ations may be tak5 ) x t 7 =m]ly only possible ( read+ ) ! omnimet]4 ,! manufacture ( omnimet]s is n[ v limit$2 ! subject is only reta9$ 9 ?is edition because !re are /ill "s hundr$s ( ^! in/rum5ts 9 use4 #ehi4--;,improvem5t 9 ! ,omnimet]4--,"o improvem5t 9 ?is in/rum5t by ,mr4 ,w4 ,n4 ,bakewell1 ,m4,in/4,c4,e41 consi/s 9 turn+ ! body ( ! microscope to a "r angle at ! position ( ! transv]se axis ( ! omnimet]1 & plac+ a reflect+ prism at ! angle4 ,by ?is means ! eye-pieces ( ! telescope & ! microscope are br\ght side by side1 greatly facilitat+ ! jo9t read+s4 ,a second improvem5t is 9 mak+ ! scale #a1jjj1jjj in/ead ( #aej1jjj1 :i* mu* facilitates calculation1 b x is d\btful if ^! improvem5ts w /ay ! decl9+ popul>ity ( ! omnimet]4 ,illu/ration3 ,fig4 #bee4--;,bakewell's tang5tial arrangem5t to a !odolite4 #eij4--;,bakewell's ,tang5tial ,arrangem5t to a ,!odolite = ,measur+ ,di/ances4--,?is arrangem5t1 :i* gives ! di/ances by direct read+ )\t calculation1 0 devis$ by ,mr4 ,w4 ,n4 ,bakewell to ext5d ! p[] ( an ord9>y #f-;in* transit !odolite fitt$ ) subt5se webs4 ,! obs]vations are made on m>ks at #c feet & #ac feet on an ord9>y ,sop) /aff--a #aj-;feet base1 z is usual ) ! omnimet]4 ,any o!r base may be us$ if ! di/ances regi/]$ are proportionally alt]$1 or ! scale may be divid$ to suit4 ,x 0 fir/ appli$ by ! au?or to a !odolite t _h be5 9 good s]vice1 )\t ! necessity ( mak+ any /ructural alt]ations 9 ! in/rum5t4#cd ,! measur+ app>atus consi/s ( a tang5t screw imp++ ^u a radial plane1 ) micromet] & v]ni]4 ,! details w be readily compreh5d$ f ! engrav+1 ,fig4 #bee1 & ! foll[+ full description4 #eia4--,! transv]se axis ( a !odolite1 ^u ! opposite side ( ! telescope to t ^u :i* ! v]tical arc is fix$1 is turn$ d[n to a cyl9drical surface true ) ! pivots4 ,a coll> ,a1 :i* fits ! cyl9drical surface1 is slit up on "o side to enable x to be clamp$ firmly to any position ( ! axis by a clamp+ screw ,b4 ,! coll> is connect$ 9 ! same gun-metal ca/+ ) ! radial arm ,c t t]m9ates at ,t 9 a plane1 :i* is made truly radial ) ! transv]se axis ( ! telescope4 ,?is radial arm ,c has a long ,g]man-silv] spr+ ,s at ! opposite side to ! radial plane1 :i* keeps x up firmly 9 contact ) ! po9t ( ! micromet] screw4 ,a screw is cut on ! drum ( ! micromet] ,d2 on ! spiral ! scale ( di/ances is engrav$2 & read+s are tak5 f a l9e on ! index ,i :i* slides on ! b> ,e4 ,! scale be+ "o ( reciprocals ! divisions are at unequal di/ances1 s a v]ni] _c be us$2 consequ5tly at long ranges :]e ! divisions are close1 ! subdivisions mu/ be e/imat$4 ,:]e ?is is too r\gh a me?od1 resort mu/ be _h to calculation4 ,! out] end ( ! drum ,d is divid$ into #bjj1 & reads by v]ni] ,v c>ri$ by ! arm ,e 9 #e or ?\s&?s ( a revolution4 ,! micromet] screw has tw5ty-five ?reads to an in*1 & ! radius ( ! arm ,c is #d in*es4 ,"o complete revolution ( ! screw is "o-hundr$? ( ! radius1 & us+ a base ( #aj ! radius factor is #ajjj #ajj #aj or #a1jjj1jjj2 consequ5tly ,b>l['s or any o!r table ( reciprocals c be us$1 & ! di/ances obta9$1 by inspection ) comp>atively little lab\r4 ,?is additional "p has n range suffici5t = altitudes1 be+ available = ab\t #b degrees only4 ,! di/ance may be tak5 z a subt5se or small tang5tial angle at a radius :i*1 ) ! azimu?al angle tak5 by ! v]tical arc ( ! !odolite1 w give altitude by its s9e & horizontal di/ance by its cos9e 9 ! usual mann]4 ,! pr9ciple is t ( ! omnimet]1 & x possesses ! same objection = p]fect p]=mance1 t ! !odolite has to be h&l$ twice = ! two obs]vations necess>y4 #eib4--,! ,gradi5t] ,screw4--,?is is no d\bt a simplifi$ copy ( ,bakewell's tang5tial arrangem5t & is %[n at ,fig4 #bef4 ,illu/ration3 ,fig4 #bef4--;,gradi5t] screw4 ,x is a micromet] screw fitt$ to a tang5t arm1 :i* c be clamp$ to ! trunnion ( telescope :5 ! latt] is 9 any position4 ,! screw is cut ( a value t causes ! web ( ! telescope to move #ej_/ajj ( a foot at #ajj feet di/ance = ea* revolution1 & ! head ( ! screw is divid$ into #ej p>ts1 consequ5tly ea* division ^u ! head repres5ts a movem5t ( ! cross web ( ! telescope ( #a_/ajj ( a foot ^u a scale plac$ at #ajj feet di/ance4 ,! scale on ! arm ov] ! gradi5t] screw indicates ! numb] ( complete revolutions ( ! head1 !re=e1 if ! screw be revolv$ two :ole revolutions ! two divisions cov]$ on ?is scale indicate #ej_/ajj #b #a foot to ! #ajj feet4 ,to e/abli% any grade ) ?is screw4--,set ! gradi5t] head to z]o1 !n level ! telescope & clamp ! gradi5t] arm4 ,suppose grade requir$ be #age4 ,turn ! gradi5t] head ?r\gh ?ree :ole revolutions1 :i* w equal #aej1 !n g on turn+ ?r\gh #be ( ! divisions on ! head & ! total movem5t w be #age1 ! requir$ grade4 ,= ,measur+ ,di/ance4--,fir/ ) a /aff = mod]ate di/ances4 ,any space on ! /aff cov]$ by two complete revolutions ( head is #a_/ajj? "p ( di/ance1 ?us1 if ! diff]5ce betwe5 ! two read+s be #cdge feet ! /aff is di/ant #cdge feet4 ,second ,me?od4--,= long di/ances ) any rod ( kn[n l5g?1 su* z a #bj-;foot /adia rod4 ,s5d out a man ) ! rod :i* he holds v]tical at place to be measur$4 ,!n measure its l5g? ) ! gradi5t] screw2 say x takes #b revolutions & #de divisions ov]1 ?us #b revolutions #ajj & #de extra divisions #ade4 ,!n-- #bjjj feet_/#ade #ajj #acgic feet4 ,ano!r in/ance4--,suppose ! man at a di/ance has no /adia rod4 ,he simply holds up any /ick1 say a walk+ /ick4 ,measure ?is 9 telescope4 ,say x subt5ds #a revolution & #bh divisions4 ,?is #gh4 ,:5 y\r man comes 9 ) ! /ick1 measure its l5g?4 ,say x 0 #cbe feet4 ,!n-- #cbe feet_/#jgh #ajj #daff feet4 ,! above illu/rations are = read+s tak5 approximately level4 ,if !re be mu* elevation or depression ! angle mu/ be read & ! diff]5ce ( hypo & base calculat$ & ! /adia rod or /aff mu/ be incl9$ s t its face is at "r angles to ! l9e ( sight f telescope4 ,?is c be done by ! rod man incl9+ ! /aff or rod until ! %orte/ read+ is giv5 if a /aff be us$1 or ! longe/ measurem5t is record$ by ! gradi5t] screw head if a /adia rod be us$4 ,x is bett] 9 ?is case to h ! /aff fitt$ ) a director 7see art4 #efa71 s t ! p]son hold+ ! /aff may sight into ! telescope ( ! in/rum5t1 ?us ensur+ ! /aff be+ exactly at "r angles to ! l9e ( sight4 ,no con/ant %\ld be add$ ) ei!r ?is1 ,bakewell's1 or omnimet] measurem5ts1 z ! angles are tak5 f ! c5tre ( ! in/rum5t4 ,?is gradi5t] screw has ! same fault z m5tion$ = ! two =ego+1 viz41 t all read+s are tak5 by two movem5ts ( ! in/rum5t4 ,,footnotes3 #bh ,description & use ( an ,improv$ ,reflect+ & ,refract+ ,telescope & ,scales = ,survey+1 by ,william ,gre51 #aggh4 #bi ,la ,ta*omtre1 ou l',art de ,lev] les ,plans et de ,faire les ,nivellem5ts1 ,p>is1 #aheh4 #cj ,tables ,trigonomtriques ,c5tsimales1 by ,j4 ,l4 ,sanguet1 ,p>is4 #ca ,manual ( ! ,!ory & ,practice ( ,topographical ,survey+ by ,means ( ! ,transit & ,/adia1 by ,j4 ,b4 ,johnson4 ,new ,york4 #cb ,pat5t1 prov41 ,no4 #ahei1 ,june1 #ahfh2 pat5t ,no4 #cgei1 ,dec41 #ahfh4 #cc ,report on ,omnimet]1 by ,major ,g4 ,a4 ,laughton1 ,sup]9t5d5t1 ,bombay ,rev5ue ,survey4 #cd ,proc4 ,in/4 ,c4,e41 vol4 xcii4 "p ii4 p4 #bdh1 #ahhg-ahhh4 ,,*apt] ,,xiii4 ,,in/rum5ts ,,con/ruct$ ,,especially ,,= ,,(f]+ ,,facility ,,( ,,tak+ ,,incl9es--,,incl9omet]--,,!odolite--,,g radiomet]--,,cl9omet]s--,,abney',s1 ,,tr\ghton',s1 ,,de ,,lisle',s1 ,,/anley',s1 ,,b>k]',s1 ,,burni]',s1 ,,watk9s'-- ,,cl9omet] ,,sights--,,rule ,,cl9omet]s--,,road ,,trac]4 ,c]ta9 in/rum5ts are con/ruct$ specially ) ! object ( tak+ incl9es1 :]e ?is is ! pr$om9ant "w to be p]=m$ ) !m4 ,!y =m an important bran* ( survey+ in/rum5ts1 & = _! special k9d ( "w pres5t _m "t-sav+ capabilities4 #eic4--,li/]'s ,incl9omet] ,!odolite4#ce--,?is in/rum5t is ! inv5tion ( ,mr4 ,james ,li/]1 ,c4,e4 ,x 0 orig9ally design$ to set out ^u ! surface ( l& ! wid?s ( slopes or batt]s by pegs1 z requir$ 9 ! execution ( railway1 canal1 & o!r e>? works4 ,9 g5]al con/ruction x resembles a !odolite z be=e describ$1 arts4 #cgj to #cia1 ) ! addition ( an extra v]tical axis to ! telescope pi]c+ ! horizontal axis at "r angles1 ,fig4 #beg4 ,9 ?is con/ruction ! telescope ^u ! horizontal axis c be set by ! v]tical supplem5t>y axis to any incl9ation1 s t if ! v]tical axis be set to ! slope ( a railway cutt+1 any numb] ( po9ts or pegs may be set out cont9u\sly ) ! same sett+ by direct obs]vation ?r\gh ! telescope across any irregul>ity or incl9ation ( ! l& surface4 ,9 ?is op]ation an imm5se am\nt ( lab\r is sav$ ov] ! ord9>y sy/em ( pegg+ by calculation ) ! aid ( a !odolite1 :]e ea* peg requires a sep>ate sett+ ( ! in/rum5t4 ,:5 ! incl9omet] !odolite is us$ = survey+ purposes1 ! telescope is fix$ by a spr+ cat* :i* places x firmly true to ! read+ ( ! ord9>y v]tical arc4 ,illu/ration3 ,fig4 #beg4--,li/]'s incl9omet] !odolite4 ,! in/rum5t is also fitt$ ) a me*anical device = repeat+ ! tang5tial angles :5 op]at+ on curves1 :i* obviates ! necessity ( read+ !m on ! horizontal arc1 ?us facilitat+ ! "w4 ,?is w be ref]r$ to 9 ! foll[+ explanation ( ! manipulation ( ! in/rum5t z ! angle repeat]4 ,! ma9 diff]5ce betwe5 ! me?od ( tak+ cross sections by ! level & by ! incl9omet] !odolite is 9 sub/itut+ incl9$ bases = horizontal ones1 :i* w be cle>ly und]/ood by ref]5ce to ! foll[+ diagrams1 :i* illu/rate some:at extreme surface incl9ation4 ,illu/ration3 ,fig4 #beh4 ,illu/ration3 ,fig4 #bei4 ,fig4 #beh %[s ! levell+ me?od & ,fig4 #bei ! me?od by ! incl9omet] !odolite4 ,9 ! fir/ x w be se5 t ea* section requires to be tak5 s+ly ) repeat$ *anges 9 ! position ( ! in/rum5t at ea* section1 involv+ num]\s read+s on ! /aff1 book+1 & r$uction ( ! levels = *anges only4 ,also ! sectional measurem5ts require to be tak5 9 %ort horizontal l5g?s ) ! plumb+ ( ! end ( ! tape at ea* l5g?4 ,by ! incl9omet] me?od ?is unnecess>y lab\r is avoid$1 !re be+ no *anges 9 ! position ( ! in/rum5t1 z f "o sett+ a s]ies ( sections may be tak5 on ei!r side ( x4 ,!re is no r$uction ( levels1 & ! sectional measurem5ts are tak5 on ! surface to :i* ! base l9e is always approximately p>allel4 ,! sav+ ( lab\r is ev5 m m>k$ 9 ! sett+ out ( slope pegs ?an 9 ! tak+ ( cross sections1 = 9 addition to ! transf]5ce ( level f ! c5tre pegs to ! outcrop ( ! slope sev]al approximate calculations h to be made be=e ! exact position ( ! slope peg c be f\nd1 :ile by us+ ! incl9omet] !odolite x is only necess>y to put 9 normal slope pegs at int]vals ( a qu>t] ( a mile1 or at su* di/ances ap>t t a rang+ rod may be se5 f "o po9t to ! o!r1 & by sett+ up ! in/rum5t at ea* alt]nate peg1 or at half mile int]vals1 ! :ole ( ! int]m$iate pegs = a qu>t] ( a mile on ea* side ( x c be bon$ z simply z rang+ a /raight l9e1 ! telescope be+ incl9$ to1 & revolv+ 9 ! plane ( ! slope4 ,9 ?is mann] z mu* "w may be done 9 a few h\rs z w take a week ) ! levell+ me?od1 & ?is )\t ! slighte/ physical or m5tal /ra9 to ! op]ator4 #eid4--;,explanation ( ! ,me?od ( ,op]at+ ) ! ,incl9omet] ,!odolite4--,= sett+ out a c5tre l9e ( railway1 etc41 & putt+ 9 level pegs ! in/rum5t may be us$ z an ord9>y !odolite1 or ev5 z a level1 & ! "w p]=m$ 9 ! usual mann]4 ,x may also be us$ z a level :5 sett+ out ! normal slope pegs on slightly incl9$ gr\nd surfaces1 b :5 ! incl9ation is consid]able x may be us$ 9 a special mann] ) advantage z h]e9aft] expla9$4 #eie4--,to take ,cross ,sections :5 ! ,l9e is ,/raight4--,x is unnecess>y to expla9 ! use ( ! in/rum5t :5 ! gr\nd surface is comp>atively level1 s z to require no *ange 9 position & resett+ ( ! in/rum5t1 x be+ obvi\s t 9 ?is case x may be us$ simply z a level ) advantage2 b :5 ! surface is incl9$ 9 ! direction ( ! c5tre1 & also at a "r angle !reto 9 ! direction ( ! section l9es1 ! me?od ( proc$ure is z foll[s3-- ,assum+ t x is desir$ to take a s]ies ( #ae sections 7& ?is is )9 ! limit ( ! numb] t c be tak5 f "o sett+ ( ! in/rum5t71 set up ! incl9omet]1 pref]ably ov] ! c5tre peg ( ! s]ies1 9 su* a position t ! two front legs ( ! tripod /& across ! c5tre l9e1 & ! back leg 7:i* has a di/+ui%+ m>k7 re/s ^u ! c5tre l9e4 ,set ! l[] limb ( ! tribra* /& ^u :i* ! in/rum5t is support$ to a level condition 9 its lat]al direction by manipulat+ ! back leg1 & at ! same "t obs]v+ ! bubble on ! /&4 ,?is w enable ! in/rum5t to be subsequ5tly tilt$ to a c]ta9 ext5t 9 a p]fectly v]tical position4 ,clamp ! horizontal arc to z]o & direct ! telescope to ! c5tre l9e4 ,clamp ! l[] limb & br+ ! arc r\nd to an angle ( #ij4 ,! v]tical arc is n[ at "r angles to ! c5tre l9e & p>allel ) ! section l9es4 ,n[ release ! telescope f ! v]tical arc & turn x aga9 on ! c5tre l9e1 & by work+ ! back adju/+ ( ! in/rum5t 7or 9 case ( necessity manipulat+ ! back leg7 tilt ! in/rum5t until ! cross web ( ! telescope is elevat$ to a %ort di/ance above ! sev5? or mo/ di/ant peg ( ! sections1 or site ( ! fir/ section to be tak54 ,n[ tilt ! v]tical arc until ! cross web assumes a position p>allel to ! g5]al incl9ation ( ! gr\nd surface lat]ally4 ,clamp ! arc to ?is incl9ation & note ! angle !reon1 = ?is w be ! angle ( ! incl9$ base f :i* ! :ole ( ! sections w be tak5 & subsequ5tly plott$4 ,comm5c+ at ! sev5? peg at ?is side ( ! in/rum5t1 ! sections may n[ be tak5 consecutively to ! sev5? peg on ! o!r side by tak+ read+s on a level /aff held 9 an incl9$ position at a "r angle to ! cross web or base1 z %[n 9 ,fig4 #bei1 & oscillat$ t ! l[e/ read+ may be tak54 ,a read+ mu/ be tak5 on ! c5tre peg at ea* section to e/abli% ! height ( ! base above ! peg4 ,! base may be rais$ or l[]$ at any section1 or "p ( a section1 to meet any excessive elevation or depression ( ! gr\nd surface :i* might prev5t ! /aff be+ read1 b a sep>ate read+ on ! c5tre peg at ea* v>iation ( ! base mu/ be tak51 ?us3--,fig4 #bfj4 ,illu/ration3 ,fig4 #bfj4 ,! bases be+ p>allel ! angle ( incl9ation rema9s ! same4 ,! tilt+ ( ! in/rum5t produces a v>iation 9 ! angle ( ! v]tical arc1 b ?is is only to su* an inf9itesimal ext5t t unless ! tilt be excessive x may be disreg>d$4 ,! correction1 h[ev]1 may be simply made aft] ! in/rum5t has be5 adju/$ = any op]ation by asc]ta9+ or simply not+ approximately ! angle ( ! tilt1 & sett+ (f ?is angle on ! horizontal arc t[>ds ! tang5t l9e1 ?us v>y+ ! *ord or base l9e to ?is ext5t1 or x may be f\nd by ref]r+ to a table ( natural s9es1 etc41 & multiply+ ! cos9e ( ! angle ( ! tilt by ! tang5t ( ! v]tical arc angle1 ! result be+ ! tang5t ( ! correct$ angle1 ?us3--if ! angle ( ! tilt be #aj1 & ! v]tical arc angle #be--,ref]r+ to tables1 cos9e #aj #ihdha1 tang5t #be #dffca4 #dffca #ihdha #deibd tang5t #bd #dj1 ! correct$ angle mak+ a v>iation ( #bj4 #eif4--,to take ,cross ,sections :5 ! ,l9e is on a ,curve4--,?is op]ation is simil> to t expla9$ above = tak+ cross sections :5 ! l9e is /raight1 except t be+ on a curve a v>iation ( ! tang5tial angle mu/ be made at ea* peg or section4 ,z ?is is p]=m$ me*anically by a s+le movem5t ( ! angle repeat] & no read+ ( ! angle is requir$1 ! "w is j z readily p]=m$4 ,to m cle>ly elucidate ! me?od1 we w take a case 9 po9t & assume t ! numb] ( sections to be tak5 is #ae & t ! radius ( ! curve is #ej *a9s1 :i* ! accompany+ diagram illu/rates4 ,diagram 7,fig4 #bfa7 %[+ ! adju/m5t ( ! in/rum5t = tak+ sections on curves & ! v>iation ( ! tang5tial angles = ea* section4 ,illu/ration3 ,fig4 #bfa4 ,if ! c5tre pegs be tak5 z slope pegs1 ! diagram applies to illu/rate ! sett+ out ( half wid?s4 ,hav+ set up ! in/rum5t at ,a1 ,fig4 #bfa1 ov] ! c5tre peg ( ! s]ies 9 ! mann] be=e describ$1 asc]ta9 ! tang5tial angle = ! fir/ *a9 ( ! curve by divid+ ! con/ant1 #agai1 by ! radius ( ! curve 9 *a9s1 :i* gives ! angle 9 m9utes or #agai #ej #cd #bd1 & set ! angle repeat] to give a movem5t ( d\ble ?is angle or #a #h #dh1 ready = application at ea* *ange ( section4 ,set ! horizontal arc to ! tang5tial angle = ! sev5? peg f ! in/rum5t at :i* ! fir/ section has to be tak51 or #cd #bd #g #d #j #dh1 & direct ! telescope to ! peg4 ,z]o is n[ on ! *ord l9e ,,ad1 :i* is p>allel to ! tang5t at ! sev5? peg1 & at an angle ( #h #a #cf1 f ! tang5t l9e ,,ab1 :i* divid$ by #g gives ! v>iation ( ! tang5tial angle at ea* section1 or #a #h #dh1 to :i* ! angle repeat] has be5 set4 ,release ! horizontal arc & br+ x r\nd to an angle ( #ij f z]o1 & ! v]tical arc w be at a "r angle to ! l9e ,a ,d & p>allel ) ! section l9e at ! sev5? peg4 ,release ! telescope f ! arc & turn x at "r angles !reto 9 ! direction ( ! z]o l9e ,,ad4 ,n[1 by work+ ! back adju/+ screw ( ! tribra*1 tilt ! in/rum5t until ! cross web comes some:at above ! sev5? c5tre peg1 !n tilt ! v]tical arc until ! cross web is p>allel ) ! lat]al incl9ation ( ! gr\nd surface4 ,clamp ! arc & note ! angle !reon to det]m9e ! incl9ation ( ! base to plot ! sections f1 & ! in/rum5t is !n 9 adju/m5t = tak+ ! fir/ section at ! sev5? peg 9 ! mann] already describ$1 be+ c>eful t ! lat]al bubble on ! in/rum5t is 9 a p]fectly level condition4 ,to take ! second section at ! six? peg1 "o movem5t ( ! angle repeat] mu/ be made & ! lat]al bubble adju/$1 :i* op]ation mu/ be repeat$ = e succe$+ section4 ,! movem5t ( ! angle repeat] br+s ! v]tical arc p>allel to ! section l9e at ea* peg1 & ! adju/m5t ( ! bubble ma9ta9s ! angle ( ! incl9$ base uni=m ?r\gh\t4 ,:5 ! sections are all tak5 on ?is side ( ! in/rum5t1 ! telescope is turn$ to ! o!r side & ! op]ation cont9u$ until ! :ole fifte5 are complet$4 ,f ! above detail$ description x may be ?\ght t ! adju/m5t ( ! in/rum5t = ! op]ation is some:at complicat$1 b 9 practice x is n s4 ,aft] ! fir/ exp]i5ce & ! me?od is und]/ood1 x is only a matt] ( two or ?ree m9utes1 & once 9 position ! sections may be tak5 z rapidly z on level gr\nd1 & ! sav+ ( lab\r is practically ! same z 9 tak+ sections :5 ! l9e is /raight4 #eig4--,to set out ,half ,wid?s or ,slope ,pegs :5 ! ,l9e is /raight4--,9 comm5c+ ?is op]ation x is necess>y 9 ! fir/ in/ance to set out two or m half wid?s1 accord+ to ! l5g? ( ! cutt+ or embankm5t4 ,^! may be a qu>t] ( a mile ap>t1 or s f> z a rang+ rod may be cle>ly se5 f "o po9t to ! o!r4 ,! pegs put 9 at ^! po9ts act z normals f :i* to bone or range 9 all int]m$iate pegs by sight simply1 )\t fur!r rec\rse to levell+ measurem5t or calculation4 ,if ! gr\nd surface be comp>atively flat1 ^! normals may be put 9 9 ! usual way by us+ ! in/rum5t z a level1 b if ! surface is mu* incl9$ & ! slope deep1 a simpl] me?od may be adopt$1 :i* w be h]eaft] expla9$4 ,illu/ration3 ,fig4 #bfb4 ,assum+ t ! normals h be5 put 91 set up ! in/rum5t at any int]m$iate peg 9 su* a position t ! telescope :5 set to ! angle ( ! slope %all l9e ) ! top ( ! peg1 z p] sket*1 ,fig4 #bfb4 ,!n release ! telescope f ! v]tical arc & direct x to "o or o!r ( ! ne>e/ normals1 adju/+ ! cross web to cut ! top ( ! peg by turn+ ! in/rum5t on its axis4 ,clamp 9 ?is position & ! telescope w revolve 9 ! plane ( ! slope1 & any po9t on ! int]m$iate surface int]sect$ by ! cross web is ! outcrop ( ! slope & ! position ( ! peg4 ,:5 all ! pegs on ! "o side ( ! in/rum5t are put 91 turn ! telescope to ! o!r side to cut ! next normal & proce$ 9 ! same mann]4 ,:5 all ! pegs h be5 put 9 = ?is half mile di/ance1 ! in/rum5t may be mov$ to ! next half mile normal & ! op]ation repeat$1 until ! :ole cutt+ or embankm5t is complet$1 ! la/ normal po9t be+ 9 all cases ! =mation wid? at ! ends4 ,9 speak+ ( half-mile di/ances we are assum+ ! mo/ fav\rable conditions ( surface & application ( ! me?od1 b 9 practice :]e ! surface is undulat+ ! positions ( ! normals %\ld be at ! mo/ elevat$ po9ts f :i* a consid]able range ( sight may be obta9$4 ,9 fix+ ! po9ts = ! slope pegs1 a rod %\ld be held 9 an incl9$ position & be br\ght to l9e exactly ) ! cross web ( ! telescope1 ! pegs %\ld !n be driv5 level ) ! gr\nd surface :]e ! foot ( ! rod has re/$4 #eih4--,to set out ,slope ,pegs :5 ! ,l9e is on a ,curve4--,! op]ation is simil> to t describ$ above1 except z expla9$ = tak+ cross sections on a curve4 ,a v>iation ( ! tang5tial angle mu/ be made = ea* peg1 & if ! c5tre peg %[n on ! diagram accompany+ t explanation be tak5 z "o ( ! slope pegs1 x w also s]ve ! purpose ( illu/rat+ ! pres5t "o1 & a brief recapitulation ( ! manipulation ( ! in/rum5t to br+ x into adju/m5t = ! op]ation is all t w be requir$4 ,! normal slope pegs hav+ be5 set out & ! in/rum5t set up at an int]m$iate "o1 z be=e expla9$1 in/ead ( direct+ ! telescope 9 ! fir/ in/ance to int]sect "o ( ! next normals1 set ! angle repeat] to d\ble ! tang5tial angle = ! fir/ *a9 9 ! curve1 & ! horizontal arc to ! tang5tial angle = ! di/ance 9 *a9s t ! normal is f ! in/rum5t4 ,!n turn ! telescope to cut ! normal peg & clamp ! l[] limb4 ,n[ br+ ! horizontal arc r\nd to an angle ( #ij f z]o & clamp4 ,release ! telescope f ! v]tical arc & turn x at a "r angle !reto 9 ! direction ( ! z]o l9e ,,ad1 & by work+ ! back adju/+ screw tilt ! in/rum5t until ! cross web cuts ! normal peg aga94 ,adju/ ! lat]al bubble on ! in/rum5t to a level condition & x is 9 adju/m5t = ! op]ation4 ,to put 9 ! fir/ peg f ! normal1 make "o movem5t ( ! angle repeat] & adju/ ! bubble4 ,to put 9 ! second "o1 make ano!r movem5t ( ! repeat] & adju/ ! bubble1 & s on until ! :ole is complet$4 ,x w ?us be se5 t by a simple me*anical op]ation a va/ am\nt ( "w c be done 9 an incr$ibly %ort space ( "t z comp>$ ) ! levell+ me?od1 & t ) little or no ef=t on ! "p ( ! op]ator4 #eii4--;,alt]native me?od ( sett+ out ! ,normal ,pegs4--,let ! diagram1 ,fig4 #bfc1 repres5t ! section ( a cutt+ at ! po9t opposite :i* ! normal has to be set out1 :5 ! section dep? may be assum$ to be #af feet1 ! =mation wid? #cj feet1 & ! slope #a to #a1 or at an incl9ation ( #ef #ah4 ,! di/ance bc = a #a to #a slope is "o-?ird ! =mation wid?1 or #aj feet4 ,! data requir$ = ! op]ation is ! di/ance ad f ! c5tre peg to ! plane ( ! slope1 :i* is f\nd by multiply+ ac by ! natural s9e ( ! slope angle #ef #ah1 ?us3 #bf #hca #bafj feet4 ,! op]ation :5 ! l9e is /raight is to set up ! in/rum5t at a c5tre peg "s di/ance away f ! normal 9 ! mann] previ\sly describ$1 viz41 ) ! front legs set across ! c5tre l9e1 ! back leg on ! c5tre l9e1 & ! bubble on ! tribra* set level be=e adju/+ ! in/rum5t1 :i* manipulation produces a p]fectly v]tical tilt4 ,aft] adju/m5t1 set ! horizontal arc to z]o & direct ! telescope to ! c5tre l9e1 clamp ! l[] limb1 set ! v]tical arc to ! angle ( ! slope1 & br+ ! horizontal arc r\nd to an angle ( #ij1 or a "r angle to ! c5tre l9e4 ,lib]ate ! telescope & direct x aga9 to ! c5tre l9e1 & by work+ ! back adju/+ screw tilt ! in/rum5t until ! cross web int]sects ! top ( ! c5tre peg at ! normal4 ,! telescope w n[ revolve 9 ! l9e ag p>allel ) ! plane ( ! slope & at a di/ance ( #bafj feet f x4 ,!re=e any po9t on ! surface 9 ! l9e ( ! slope :]e #bafj c be read on ! /aff is ! outcrop ( ! slope & ! position ( ! peg4 ,9 ?is example1 :5 ! requir$ read+ is high] ?an ! ord9>y /aff1 l[] ! tilt & take an int]m$iate read+1 z at f 9 ! diagram1 ,fig4 #bfc1 :i* may read1 say1 #abjj1 :5 ! requir$ read+ on ! peg w be r$uc$ to #ifj4 ,illu/ration3 ,fig4 #bfc4 ,9 sett+ out normals on a curve by ?is me?od ! only diff]5ce 9 ! op]ation to t above describ$ is t in/ead ( 9 ! fir/ in/ance clamp+ ! in/rum5t ) z]o on ! c5tre l9e1 x mu/ be clamp$ ) z]o on ! *ord l9e1 i4e41 at d\ble ! tang5tial angle = ! di/ance ! in/rum5t is f ! peg1 z be=e expla9$ 9 detail = op]ations on curves4 ,by ?is me?od two normals may be set out at lea/ #bj *a9s ap>t f "o sett+ ( ! in/rum5t1 or sev]al slope pegs may be set out 9 l mann]1 :i* "u c]ta9 cont+5t difficulties ( gr\nd surface is an advantage ( consid]able importance4 ,9 ?is connection !re is also an alt]native me?od ( putt+ 9 ! slope pegs aft] ! normals h be5 set out1 :i*1 "u c]ta9 conditions1 may be employ$ ) advantage4 ,in/ead ( sett+ up ! in/rum5t at ! back ( ! normal ) ! telescope set to l9e ) ! plane ( ! slope1 & to range ! pegs 9 by means ( a rod or /aff held at ! incl9ation ( ! slope1 z be=e describ$1 x may be set up 9 any position 9 ! l9e ( slope :]e a read+ c be tak5 on ! peg1 z at a on ! sket* 7,fig4 #bfd71 & at ! po9t read1 z at b1 a disc %\ld be clamp$ to ! /aff1 z ?is c be mu* m cle>ly se5 ?an ! /aff graduations :5 sight+ long di/ances4 ,! /aff %\ld !n be transf]r$ to ! next normal & held on ! peg4 ,if ! telescope be n[ turn$ 9 ?is direction & ! cross web adju/$ to cut ! disc1 any po9t on ! int]m$iate surface :]e ! disc c be int]sect$ is ! outcrop ( ! slope & position ( ! slope peg4 ,illu/ration3 ,fig4 #bfd4 ,x is necess>y to obs]ve 9 ! sett+ out ( slope pegs t :5 !re is a *ange ( gradi5t ! op]ation mu/ cease1 b if ! po9t :]e ?is occurs be made ! position ( a normal ! op]ation may be proce$$ )1 if ! in/rum5t be set up at ?is po9t4 #fjj4--,to set out ,slope ,pegs on bo? sides ( ! ,l9e simultane\sly )\t mov+ ! ,in/rum5t f ! ,c5tre ,l9e4--,,conditions4 ,s+le ,l9e4 7ab7 ,=mation #ae feet4 7cd7 ,dep? ( cutt+ #ad feet4 ,slope #a to #a4 ,! po9t e1 ,fig4 #bfe1 is ! ext5sion ( ! slope l9es to cut ! c5tre l9e1 & its dep?s bel[ =mation = #a to #a slope is half ! =mation wid?1 or #g #f4 ,illu/ration3 ,fig4 #bfe4 ,,op]ation4--,! in/rum5t be+ set ov] a c5tre peg ) ! telescope at ! slope angle1 turn ! telescope to any o!r peg & adju/ ! cross web to l9e !re) 7on l9e c f74 ,take ! section dep? cd 7#ad feet71 to :i* add de 7#g #f7 #ba #f4 ,?is multipli$ by #gjg1 ! natural s9e ( ! slope angle 7#de7 w give ! di/ance f ! axis ( ! in/rum5t to ! slope l9e1 ?us3 #baej #gjg #aebj feet1 & ! po9t on ! surface at g :]e #aebj c be read on ! /aff is ! position ( ! slope peg4 ,?is is simil> to t describ$ 9 ! la/ p>agraph1 b if ! telescope be n[ *ang$ to ! angle ( ! slope on ! o!r side ( ! l9e *1 ! peg i is in/antly f\nd by ! same read+ 7#aebj74 #fja4--,! ,use ( ! ,incl9omet] 9 ,m9+4--,a lode hav+ be5 discov]$1 x is requir$ to m>k out on ! gr\nd ! g5]al l9e ( ! outcrop4 ,hi!rto ! me?od employ$ has be5 to f9d ! /rike & drift ( ! lode & to level & survey ! surr\nd+ c\ntry & plot on a cont\r plan4 ,l9es p>allel to ! /rike & spac$ accord+ to ! trigonometrically calculat$ bases are rul$ 94 ,! po9ts ( int]section ( ! cont\r l9e ) t ( ! p>allel l9e to ! /rike ( ! same height above datum w be a po9t ( outcrop4 ,! be>+s ( ^! po9ts are read1 & _! di/ances scal$ f ! plan1 ! !odolite is !n tak5 to ! field1 & ! po9ts f\nd are m>k$ out on ! gr\nd4 ,?is entails a consid]able am\nt ( lab\r & c>eful "w bo? 9 ! field & (fice1 & !n only po9ts at int]vals are obta9$ & n a cont9u\s l9e4 ,! incl9omet]1 hav+ an adju/able axis at "r angles to ! horizontal1 enables ! l9e ( sight to be made to revolve 9 any plane4 ,if at ! spot :]e ! lode has be5 discov]$ ! in/rum5t be set up 9 l9e ) ! /rike1 & ! movable axis adju/$ to ! angle ( dip1 x is evid5t ! l9e ( sight lies :olly 9 t plane1 & a cont9u\s l9e ( outcrop may be pegg$ out on a flat or undulat+ c\ntry1 :i* c be produc$ to any l5g? requir$ by tak+ ! in/rum5t to a fre% /ation4 ,?is feature ( ! in/rum5t is equally1 if n m1 important ?an its use = rapidly pegg+ out railway slopes4 #fjb4--,! ,gradiomet]4--,?is in/rum5t1 :ile p]=m+ all ! duties ( a fir/-class level1 is design$ also = tak+ v]tical incl9es at small fix$ angles = railways1 dra9age works1 /eep incl9e levell+1 etc41 etc41 & also telemetrical read+s up to great di/ances4 ,9 g5]al con/ruction1 z reg>ds telescope1 /&1 etc41 x resembles a level1 & :5 set at z]o is equal 9 e way to "o ( ! be/1 ) ! additional advantage t x may be us$ = rapid "w )\t ! tr\ble ( sett+ up by ! levell+ screws1 z ! telescope may be levell$ at any sight by means ( ! gradi5t] drum mill$ head4 ,! gradiometric arrangem5t is effect$ by ! telescope be+ m\nt$ 9 trunnions1 "o pair be+ adju/$ v]tically2 ! am\nt ( elevation or depression is indicat$ by a drum c>ry+ an op5 ext5d$ scale graduat$ to read rise or fall1 f #a 9 #ab to #a 9 #a1bjj1 :i* may be conv5i5tly & di/9ctly read )\t ! use ( a v]ni]4 ,! additional p>ts d n increase ! bulk ( ! case & add v little to ! weight4 ,illu/ration3 ,fig4 #bff4--,/anley's gradiomet]4 ,by its use a great sav+ ( "w is effect$4 ,= in/ance1 = a t[n dra9age 9 :i* x is desir$ to "w out an incl9ation1 say ! levels indicate a fall ( #aj feet betwe5 ! extreme po9ts3 if ! l9e ! dra9age is int5d$ to take be measur$1 h[ev] angul> or zigzag x may be1 & ! l5g? ( t l9e be divid$ by ! am\nt ( fall1 ?is w give ! gradi5t2 say ! l9e ( /reets measures #e1jjj feet1 ?is1 divid$ by #aj feet1 gives a gradi5t ( #a foot 9 #ejj4 ,!re=e if ! drum be set to t proportion1 all ! pipes may be laid directly )\t fur!r sett+4 ,! gradi5ts = any railway may be in/antly f\nd by m]ely turn+ ! drum until ! telescope sights1 up or d[n ! incl9e to be measur$1 a read+ on ! /aff equal to ! height ( ! in/rum5t1 & tak+ ! read+ ( ! drum at ! position ( ! indicator4 ,= levell+ /eep incl9es x also saves a great numb] ( sett+s up1 z1 in/ead ( levell+ =1 say e #ad feet rise or fall1 ! gradi5t ( ! total di/ance c be tak5 & also ! di/ance measur$ by /adia read+1 :5 ! incl9e is n too great = tak+ "o read+ ) telescope level1 or by gradi5t read+ :5 ?is _c be done1 & by add+ ! /aff read+ to ! di/ance divid$ by ! gradi5t1 & d$uct+ ! height ( ! in/rum5t ! diff]5ce ( level c at once be asc]ta9$4 ,example3 ,sight+ a /aff at a gradi5t :i* falls conv5i5tly ^u x1 say #a 9 #ce & ?is reads #hg feet4 ,di/ance measur$1 z expla9$ lat]1 say #gce feet1 !n #gce_/ce #ba feet #hg feet #big feet2 d$uct ! height ( in/rum5t1 say #di feet1 diff]5ce ( level #bdh feet4 ,= measur+ long di/ances beyond ! range ( ! /adia l9es or po9ts 9 ! diaphragm1 or = measur+ di/ance on incl9es1 ! gradiomet] w also be f\nd v useful1 z by tak+ ! diff]5ce ( any two suitable gradi5ts1 ! base di/ance is giv5 )\t calculation = diff]5ce ( hypo & base4 ,if ! gradi5t be n v /eep or bel[ ! height ( ! /aff1 ! simple/ me?od is to sight ! /aff ) ! telescope level & take ! /aff read+2 say ?is is #abde feet1 !n set ! gradi5t drum to #a 9 #ajj & aga9 take ! /aff read+ &1 say ?is is #dcj feet1 ! diff]5ce betwe5 ^! read+s #hae feet4 ,/rike out ! decimal po9t :i* multiplies x by #ajj & we h ! base di/ance #hae feet4 ,= %ort] di/ances a l>g] base ^u ! /aff may be tak51 ?us giv+ great] accuracy2 = in/ance1 if ! gradi5t drum aft] tak+ ! level read+ be set to #a 9 #ej & ! result+ diff]5ce divid$ by #b1 any error 9 tak+ exact read+s is r$uc$ by "o half1 or #a 9 #cc-a_/c & divide diff]5ce by #c2 or #a 9 #be & divide diff]5ce by #d3 or #a 9 #bj & divide diff]5ce by #e1 etc4 ,any error ( read+ w\ld be r$uc$ by "o ?ird1 "o f\r?1 "o fif?1 etc4 ,! diff]5ce ( read+s obta9$ by ei!r ( ! foll[+ two gradi5ts w also give base measurem5t )\t any calculation :atev]3 #ajj & #ej #fc-b_/c & #dj #fj & #cg #ej & #cc-a_/c #cc-a_/c & #be #be & #bj #bj & #af-b_/c #ab & #aa-a_/i #aa-a_/i & #aj4 ,example3 ,suppose ! top ( /aff is bel[ level altoge!r1 turn ! drum until ! top ( /aff is sight$ 9 ! telescope2 say ! gradi5t ( ?is is #bg g on turn+ until gradi5t #be is indicat$ & take ! /aff read+2 say ?is is #abge1 !n move ! drum until gradi5t #bj is indicat$ & take ! /aff read+3 suppose ?is to be #cdj1 !n #abge - #cdj ------ #ice ,omit ! decimal po9t & ! measurem5t reads #ice feet1 :i* is ! horizontal di/ance4 ,! two mo/ suitable gradi5ts w\ld ( c\rse be us$ accord+ to ! position4 ,di/ances may be set out ) equal facility ) ! gradiomet] by ! subt5se me?od1 by work+ out a subt5se suitable = ! di/ance4 ,?is is easily done by divid+ ! di/ance requir$ by any two numb]s hav+ a diff]5ce ( ! requir$ subt5se1 ! result be+ two gradi5ts1 :i*1 :5 work$ )1 w give t subt5se at ! requir$ di/ance4 ,example3 ,if ! di/ance requir$ to be set out be #fej feet1 a suitable size = an object to be pla9ly visible at ?is di/ance w\ld be #aj feet4 ,!n take z divisors two numb]s hav+ a diff]5ce ( #aj1 say #aj & #bj4 #fej #aj #fe #fej #bj #cb ,^! two gradi5ts w give a subt5se ( #aj feet at a di/ance ( #fej feet1 & all t is necess>y is to s5d a man out 9 ! requir$ direction ) a #aj-;feet rod 7pref]ably hav+ ends1 ?us 1 = long di/ances1 to facilitate di/9ct read+71 & signal him to move f>!r (f1 or ne>] until ! l5g? ( ! rod1 held v]tically1 is exactly cov]$ by ! movem5t ( ! telescope caus$ by revolv+ ! drum betwe5 gradi5ts #fe & #cb4 ,illu/ration3 ,fig4 #bfg4--,/anley's gradioplane4 ,x is always pref]able to make ! subt5se z l>ge z possible1 z ! l>g] x is ! m accurate ! result w be4 ,all di/ances set out by ?is me?od are base di/ances1 no matt] :at ! diff]5ce ( level may be1 & su* figures = divisors %\ld be us$ z give ! gradi5ts bel[ #ajj4 ,gradi5ts betwe5 #ab & #fe are ! be/ & quicke/ to "w )1 & ) c>e m accurate results are obta9$ ?an ) *a9+4 ,?us1 at "o "t1 a di/ance may be set out or measur$1 ! diff]5ce ( level tak51 & also ! gradi5t asc]ta9$1 & ! drum c in/antly be set to z]o & all ord9>y levell+ op]ations cont9u$4 ,if pref]r$ ! gradi5t drum c be divid$ to p]c5tage gradi5ts #jja to #h in/ead ( ord9>y gradi5ts #a 9 #ab to #a 9 #a1bjj4 #fjc4--;,gradioplane4--,?is is a new in/rum5t1 specially design$ by ! revis] = v accurate und]gr\nd survey+1 su* z is requir$ = l>ge sewage "w or wat] works1 long tunnels1 or any "w requir+ a v rigid & accurate in/rum5t1 ) a v p[]ful telescope = measur+ all horizontal & small v]tical angles4 ,! horizontal circle is #f in*es diamet]1 & reads by two v]ni]s to #bj seconds ( arc1 or x is fitt$ ) micromet] microscopes read+ to five seconds ( arc if desir$4 ,9 ! =m] case x c>ries a float+ bevell$ alum9ium r+ compass divid$ to degrees1 read+ by microscope1 & 9 ! latt] a long tr\gh compass4 ,v]tical angles are measur$ by a v accurate =m ( gradiomet] screw c>ry+ a drum ) op5 ext5d$ scale 9 exactly ! same mann] z ! =ego+ in/rum5t1 & ! rem>ks reg>d+ t & its work+ apply equally to ?is in/rum5t4 ,! telescope1 :i* is #ad in*es long & c>ries a #a in* object glass is s m\nt$ t x w revolve 9 ! plane ( any incl9ation set by ! gradiomet] drum1 & is provid$ ) a lock+ arrangem5t = fix+ x absolutely true = =e or back sight1 & x c>ries a long s5sitive _s bubble to enable x to be us$ z a mo/ accurate level & = rapid levell+2 ?is may in/antly be set level by ! drum at any sight )\t tr\bl+ to level ! in/rum5t4 ,! diaphragm is fitt$ = subt5se measurem5ts4 ,a fur!r ref9em5t is fitt$ to ! telescope :5 desir$1 by :i* any grade may be in/antly divid$ into any desir$ numb] ( p>ts2 ?is is effect$ by means ( a horizontal circle fitt$ to ! /age "u ! telescope1 :i* is read by a v]ni] atta*$ to ! telescope4 ,?is circle is divid$ f #j :5 ! telescope is fix$ at z]o r\nd ea* way to #ij degrees into #ajj p>ts1 ! v]ni] divid$ to read #ajj?s or #aj?s ( ea* division4 ,x w be se5 t :5 ! telescope is 9 l9e ) ! gradi5t drum1 t is at z]o1 x w be rais$ or depress$ to :atev] grade is indicat$ ^u ! drum1 & is !n capable ( be+ revolv$ #ahj degrees = tak+ a back sight1 :5 x sights ! opposite grade to t :i* x does :5 at z]o4 ,:5 x has revolv$ #ij degrees only ! telescope becomes level at any grade1 & !re=e at any position x is set betwe5 z]o & #ij degrees x sights a "p ( t grade2 suppos+ ! telescope at z]o is set by ! gradi5t] drum at #a #a1jjj !n by revolv+ ! telescope f t to level1 x passes ov] #ajj p>ts ( t grade1 ea* ( :i* may be subdivid$ by ! v]ni] to #ajj p>ts aga91 consequ5tly #ajj #ajj #a1jjj :i* equals #a 9 #aj1jjj1jjj or any desir$ numb] ( #aj1jjj1jjj?s may be readily set by means ( ! clamp & tang5t fitt$ to ! telescope1 or if ! grade be set by ! gradi5t drum to #a #ajj !n #ajj #ajj #ajj equals #a 9 #a1jjj1jjj1 or any o!r grade :i* is set by ! gradi5t drum may1 ) equal ease1 be divid$ by #aj1jjj or any o!r proportion t ! horizontal circle v]ni] may be divid$ to give4 ,a slid+ l[] plate is provid$ = accurately c5tr+ ! in/rum5t1 ! levell+ screws are adju/able = we>1 & ! tribra* is fitt$ ) quick-sett+ sph]ical jo9t4 ,?is in/rum5t w also be f\nd ( great utility 9 m9+ "w1 to m>k out ! g5]al l9e ( ! outcrop :5 a lode has be5 discov]$4 ,?is1 by ! ord9>y me?od1 entails a consid]able am\nt ( lab\r & c>eful "w bo? 9 ! field & (fice1 & !n only po9ts at int]vals are obta9$1 n a cont9u\s l9e4 ,) ?is in/rum5t ! l9e ( sight may be made to revolve 9 any plane1 s t if x be set up 9 l9e ) ! /rike at ! spot :]e ! lode has be5 discov]$ & ! gradi5t drum adju/$ to ! angle ( dip1 x is evid5t t ! l9e ( sight w be :olly 9 t plane1 & a cont9u\s l9e ( outcrop may be pegg$ out on a flat or undulat+ c\ntry & c be produc$ to any l5g? requir$ by tak+ ! in/rum5t to a fre% /ation4 ,illu/ration3 ,fig4 #bfh4--,/anley's gradioplane4 ,! above illu/ration1 ,fig4 #bfh1 %[s ! gradioplane fitt$ ) a horizontal circle to ! telescope = subdivid+ ! grades ( ! gradi5t] drum1 & :5 ?us fitt$ =ms ! mo/ exact in/rum5t = sett+ out or asc]ta9+ gradi5ts t has be5 devis$4 #fjd4--;,abney's ,cl9omet]4--,?is v popul> little in/rum5t1 ! inv5tion ( ,capta9 ,abney1 ,fig4 #bfi1 embraces ! same =m ( sight$ level ) reflector z t %[n 9 section1 ,fig4 #hg1 p4 #adb1 b ! level in/ead ( be+ fix$ 9 l9e ) ! tube is plac$ above x ^u an axis :i* =ms ! c5tre ( a divid$ arc4 ,! axis ) ! bubble is turn$ to any angle by means ( a light mill$-edg$ :eel plac$ 9 front ( ! arc4 ,x c>ries an index :i* reads on ! arc ! angul> position ( ! level to ! c5tre ( ! in/rum5t by a v]ni] to #aj4 ,!re is also a scale plac$ ^u ! arc giv+ gradi5ts f #a 9 #a to #a 9 #aj4 ,z ! bubble ( ! level 9 its c\rse passes ! c5tre ov] ! axis its reflection is made to become co9cid5t ) ! sight l9e ?r\gh ! tube only :5 x is q level4 ,!re=e :atev] ! incl9ation ( ! tube1 ! bubble may be br\ght level by turn+ ! mill$ head until x appe>s c5trally 9 ! sight axis ( ! tube1 & ! angle at :i* ?is occurs c be cle>ly read aft]w>ds ^u ! arc4 ,! size ( ! in/rum5t 9 its case is #e by #b by #a in*es2 weight1 #h oz4 ,illu/ration3 ,fig4 #bfi4--;,abney's cl9omet]4 ,illu/ration3 ,fig4 #bgj4--,tr\ghton's cl9omet]4 #fje4--,tr\ghton's ,abney's ,cl9omet]4--,9 ! ,tr\ghton =m1 ,fig4 #bgj1 ! arc is too!d1 & x is mov$ by a p9ion simil> to ! movem5t ( ! box sextant1 s t ! bubble moves sl[ly 9 relation to ! motion ( ! f+]s :5 adju/+4 ,! arc is read by a s+le index l9e in/ead ( by a v]ni]4 #fjf4--,telescopic ,h& ,cl9omet]4--,! au?or has rec5tly add$ a telescope to ! ,abney =m ( cl9omet]1 z %[n ,fig4 #bga4 ,! arc is mov$ by rack & p9ion & reads by a v]ni] to s+le m9utes1 !re=e good read+ )9 "o m9ute ( arc may be made ) x4 ,capta9 ,ea/1 ,r4,e41 sugge/$ a mode ( /eady+ ! in/rum5t = obs]vation :i* appe>s to answ] admirably = h& obs]vation4 ,he puts ! hook-end ( 8 walk+-/ick into 8 wai/coat pocket & clut*es a "p ( ! /ick by 8 "r h& at ! height ( 8 eye4 ,!n hold+ ! in/rum5t 9 8 "r h& support$ by ! /ick x is kept q /eady = obs]vation4 ,illu/ration3 ,fig4 #bga4--,telescopic ,abney cl9omet]4 #fjg4--;,de ,lisle's ,reflect+ ,cl9omet]4--,!re h be5 sev]al arrangem5ts made = conv]t+ ! ,burel level1 ,fig4 #hi1 into a cl9omet]2 t devis$ by ,g5]al ,a4 ,de ,lisle1 ,r4,e41 ) modifications by ,colonel ,bell & ,mr4 ,alfr$ ,cooke1 z repres5t$ 9 ,fig4 #bgb1 is ! mo/ popul>4 ,9 ?is a heavy arc is con/ruct$ ^u ! l[] "p ( ! in/rum5t4 ,?is is jo9t$ ^u a v]tical axis at ,c s t x may be revolv$ to br+ ! mass ( ! arc ei!r =w>d or backw>d1 to take incl9es upw>ds or d[nw>ds1 or to re/ at an int]m$iate position to make ! in/rum5t flat & portable 9 its case1 x takes ! position %[n 9 ! figure4 ,! arc has a /iff c5tre axis ) a radial b>1 ! edge ( :i* =ms ! index4 ,a slid+ weight is plac$ on ! radial b>1 :i* is suffici5tly heavy :5 at its greate/ ext5sion to exactly c\nt]balance ! weight ( ! arc 9 a horizontal position & to make ! mirror q v]tical4 ,9 ?is position x =ms a simple ,burel level4 ,a set ( graduations are made ^u ! arc1 :i* are numb]$ #a to #ej to #a to #a4 ,! radial b> index set to "o ( ^! numb]s gives ! am\nt ( incl9ation t w result f ! co9cid5ce ( ! reflection ( ! c5tre ( ! pupil ( ! eye cutt+ ! object to be obs]v$4 ,! l5g? ( ?is in/rum5t is ab\t #f in*es2 its weight ab\t #aj oz4 ,illu/ration3 ,fig4 #bgb4--;,de ,lisle's reflect+ cl9omet]4 #fjh4--,prismatic ,cl9omet]4--,?is in/rum5t 0 orig9ally devis$ by ! au?or ab\t #ahfj4 ,! =m ( ! in/rum5t1 ,fig4 #bgc1 is t ( a prismatic compass1 art4 #aee4 ,a simil> metal or c>d & talc dial to t ( ! prismatic is us$1 b ?is is c5tr$ ^u a transv]se axis :i* is po9t$ at ! ends to fit into holl[ c5tres4 ,?is c>d is weight$ on "o side1 s t :5 ! sights are 9 a truly horizontal position ! prism w %[ ! z]o ( ! c>d cutt+ ! sight l9e4 ,if ! in/rum5t be incl9$ upw>ds or d[nw>ds1 ! degrees ( elevation or depression w be indicat$ by ! c>d reta9+ its p5dul\s position4 ,?is is a v conv5i5t in/rum5t = use ) ! box sextant1 & z x is only ( ab\t half an in* 9 ?ickness1 & ( ! same diamet]1 x w pack conv5i5tly 9 ! case ) t in/rum5t--weight1 #h oz4 ,illu/ration3 ,fig4 #bgc4--,/anley's prismatic cl9omet]4 ,illu/ration3 ,fig4 #bgd4--;,b>k]'s cl9omet]4 ,9 ,us+ ?is ,=m ( ,cl9omet] ! prism is rais$ or l[]$ 9 its slid+ fitt+ until ! divisions ( ! c>d are %>ply def9$4 ,!n 9 look+ ov] ! edge ( ! prism ?r\gh ! slot above x1 ! hair 9 ! w9d[ ( ! back sight w appe> to cut ! divisions ( ! c>d2 & ! object se5 9 ! di/ance1 9 front ( ! hair to :i* ! in/rum5t is direct$1 w appe> co9cid5t ) ! numb] ( degrees ( incl9ation indicat$ by ! c>d4 ,?is cl9omet] is sometimes fitt$ ^u a prismatic compass1 s t incl9es may be read by ! same prism & sight arrangem5t4 ,?is is1 h[ev]1 done m neatly by ! arrangem5t next describ$1 if ! in/rum5t is int5d$ to be us$ ) ! prismatic compass only1 & is n want$ sep>ately = use ) ! *a94 #fji4--;,b>k]'s ,comb9$ ,prismatic ,compass & ,cl9omet]1#cf ,fig4 #bgd4--,! prismatic compass ( ?is arrangem5t is t ( ,hut*ison's =m1 art4 #aee4 ,! cl9omet] is ( ! same k9d z t j describ$1 b ?is1 in/ead ( be+ a sep>ate "p ( ! in/rum5t capable ( deta*m5t1 rema9s p]man5t4 ,to effect ?is arrangem5t ! cl9omet] c>d is m\nt$ ov] ! compass c>d on a p9 axis in/ead ( c5tres4 ,a "p ( ! cl9omet] c>d is cut away s z to p]mit ! compass c>d to be read b5ea?4 ,?is cut-away "p is held by a /op to a position out ( ! field ( ! prism :5 ! in/rum5t is to be us$ z a prismatic compass4 ,:5 ! /op is releas$ & ! in/rum5t is held ) its face v]tical1 ! p5dul\s cl9omet] c>d comes into view1 & cuts by its read+ ?r\gh ! prism ! sight l9e1 z be=e describ$ = ! prismatic cl9omet]4 ,! prism is focuss$ to ! upp] or l[] dial by a long1 slid+ fitt+4 ,x is us$ z ! in/rum5t la/ describ$4 ,illu/ration3 ,fig4 #bge4--;,cont95tal =m ( cl9omet] 7,burni]74 ,illu/ration3 ,fig4 #bgf4--,section ( ! same4 #faj4--;,cont95tal ,=m ( ,cl9omet]4--,h& cl9omet]s on ! ,cont95t are g5]ally made on ,capta9 ,burni]'s plan1 ,fig4 #bge1 :i* 0 expla9$ = ! prismatic compass1 art4 #aef4 ,inde$ ?is in/rum5t is m g5]ally comb9$ ) ! prismatic compass4 ,! graduation is set up on a plat$ r+ v]tical to ! plane ( ! sw+ ( a p5dulum1 %[n 9 section ,fig4 #bgf4 ,! read+ index is a hair :i* is read on ! graduation by means ( a cyl9drical l5s1 ,b1 :5 ?is is br\ght co9cid5t ) ! sights ,d,w z describ$ = ,burni]'s compass4 ,:5 ! cl9omet] & compass are comb9$ ! v]tical rims /& opposite to ea* o!r1 ,,ac4 ,a lift]1 ,fig4 #bge1 ,l1 is provid$ to take ! work+ p>ts out ( be>+1 & a /op ,s to prev5t oscillation4 ,! illu/rations %[ ! comb9$ in/rum5t3 ,b cyl9drical l5s read+ ! drums2 ,a cl9omet]2 ,c compass2 ,,dd =e sight2 ,,ww w9d[s1 bo? ( :i* fold d[n on ! top ( ! in/rum5t4 ,illu/ration3 ,fig4 #bgg4--,major ,watk9s cl9omet]4 #faa4--,major ,watk9s' ,cl9omet]4#cg--,! v]tical plane ( division is adopt$1 z 9 t ( ,capta9 ,burni]1 b ! read+1 in/ead ( be+ tak5 on ! ext]ior ( ! r+ by a magnifi]1 :i* entails a projection1 is plac$ on its int]ior4 ,?is read+ is magnifi$ by a concave reflector1 %[n ,fig4 #bgg at ,r1 :i* reads to a l9e on a slip ( ivory plac$ j beside ! eye-hole ,e %[n 9 ! engrav+4 ,! p5dulum is /opp$ by a p91 ^u :i* x spr+s :5 ! box is rotat$ v]tically to prev5t we> :5 out ( use4 ,!re is mu* less "w 9 mak+ ?is in/rum5t ?an ,burni]'s1 & ! r\nd =m is m portable4 ,! only po9t on :i* x does n be> comp>ison is 9 t ! concave mirror repres5ts a uni=m di/ance sight :i* makes ! read+ indi/9ct to p]sons ( weak sight1 :]eas ,burni]'s admits ( adju/m5t by plac+ ! in/rum5t ne>] to or fur!r f ! eye1 ! cyl9drical l5s be+ made l>ge to admit ( ?is =m ( adju/m5t4 ,?is in/rum5t c\ld be improv$ by ! mirror be+ made adju/able4 ,weight1 #f oz4 ,illu/ration3 ,fig4 #bgh4--;,compass ) cl9omet] sight4 #fab4--;,cl9omet] ,sights4--,a cl9omet] sight is (t5 atta*$ to a light pocket compass1 z %[n ,fig4 #bgh at ! upp] "p ( ! engrav+1 consi/+ ( a p9 hole & hair cross4 ,?is1 us$ 9 ! mann] %[n by ! position ( ! eye 9 ! engrav+1 c only be made to take sight incl9es by ano!r p]son read+ ! p5dulum index1 :i* m>ks ! incl9ation 9 ! degrees to :i* ! compass is divid$4 ,?is portable pocket in/rum5t is1 h[ev]1 useful 9 o!r ways4 ,/&+ face to ! in/rum5t x w measure incl9es directly v fairly by look+ ov] ! top edge & br++ ?is to ! visual rate ( incl9ation at :i* ! p5dulum index c be read 9 front view4 ,geologi/s commonly use x 9 ?is way to take ! dip ( /rata4 ,x c also be us$ by putt+ x on or aga9/ any incl9$ surface4 ,! case is g5]ally gilt or nickel plat$1 & is ab\t #b in*es diamet]1 & ! in/rum5t weighs ab\t #c oz4 ,illu/ration3 ,fig4 #bgi4--,rule =m cl9omet]4 #fac4--,rule ,=m ,cl9omet]4--,?is is made 9 ! =m ( a /\t #ab-;in*1 "o-fold boxwood rule1 ,fig4 #bgi4 ,x is mu* us$ by civil eng9e]s z a work+ tool1 & int5d$ to be appli$ directly to an incl9$ surface1 ei!r plac$ on a /raight-edge or o!rwise1 g5]ally to take ! incl9ation ( e>? "w4 ,x may be plac$ ^u a picket laid ^u ! gr\nd to take natural slope4 ,:5 us$ 9 ?is mann] ! l[] surface is plac$ on ! /raight-edge or picket1 & ! rule is sl[ly op5$ until ! bubble 9 ! level 9 ! upp] limb becomes c5tral4 ,! arc ( ! head jo9t w !n indicate ! incl9ation4 ,x may be us$ 9 ano!r way3 ! l[] limb may be set level on ! dumpy level compass or on any flat plane1 & ! incl9ation may be sight$ ?r\gh ! p9-hole & cross-hair sights %[n at ! ends ( ! upp] "p ( ! in/rum5t4 ,its size is #f by #a by in*es2 weight #i oz4 ,!re are sev]al v>ieties ( ?is in/rum5t4 ,illu/ration3 ,fig4 #bhj4--,road trac]4 #fad4--,! ,road ,trac] is a balanc$ cl9omet] mu* us$ by natives 9 ,india & ,*9a = road mak+1 ,fig4 #bhj4 ,x consi/s ( a p5dulum1 support$ ^u a /& t c>ries a sight$ tube :i* indicates ! level ( ! gr\nd :5 ! weight is c>ri$ 9 ! axis ( susp5sion4 ,! weight is adju/able to a scale by a screw4 ,! scales read incl9es1 by displacem5t ( ! weight1 up & d[n 9 p]c5tages or gradi5ts1 to :i* x may be divid$4 ,illu/ration3 ,fig4 #bha4--;,bellamy's road trac]4 ,?is in/rum5t has be5 improv$ by ,mr4 ,c4 ,v4 ,bellamy1 ,m4,i4,c4,e41 ,m4,i4,m4,e41 ,f4,g4,s41 c41 ,director ( ,public ,works1 ,lagos1 ,we/ ,africa1 a civil eng9e] :o has _h great exp]i5ce 9 ! colonies1 & x w be f\nd mu* m accurate1 less liable to get out ( ord] & f> m conv5i5t to use ?an ! old =ms4 ,x is %[n at ,fig4 #bha4 ,! *ief feature ( ?is patt]n lies 9 ! adoption ( ! arc ( a circle in/ead ( a /raight scale1 & a p5dulum weight actuat$ by a rack & p9ion 9 place ( ! screw & slid+ weight4 ,?is admits ( great] nicety 9 ! divisions & all[s a /rong] & light] con/ruction4 ,! sight+ tube is provid$ ) rev]sible slid+ %utt]s1 s t back read+s may be tak5 )\t unclamp+ ! in/rum5t or alt]+ ! v]ni] or index4 ,a p[]ful clamp is provid$ = lock+ at any desir$ grade4 ,a rec5t fur!r improvem5t by ,mr4 ,bellamy has be5 made by mak+ ?is in/rum5t 9 a =m to give read+s 9 degrees ( arc z well z 9 gradi5ts4 ,fig4 #bhb4 ,illu/ration3 ,fig4 #bhb4--;,bellamy's improv$ road trac]4 ,,footnotes3 #ce ,li/]'s ,pat5t1 ,no4 #bcge1 #ahfd4 #cf ,francis ,b>k]'s pat5t1 ,no4 #aibf1 #ahha4 #cg ,briti% pat5t1 ,no4 #bag1 #ahhd4 ,,*apt] ,,xiv4 ,,in/rum5ts ,,( ,,reflection--,,octant ,,or ,,quadrant--,,reflect+ ,,circle--,,sextant--,,pr9ciple--,,p>all ax--,,con/ruction--,,exam9ation-- ,,adju/m5t--,,artificial ,,horizon--,,s\nd+ ,,sextant--,,box ,,sextant-- ,,supplem5t>y ,,arc--,,improvem5ts ,,^u ,,?is--,,optical ,,squ>e--,,optical ,,cross--,,apomecomet]4 #fae4--,! ,octant or ,quadrant measures angles )9 #ij by an arc ( #de4 ,?is in/rum5t is g5]ally t]m$ an octant on ! ,cont95t f ! space ( ! divisions2 a quadrant by ,engli%-speak+ races1 f ! ext5t ( angles x takes4 ,! idea ( br++ ! reflection ( an object f a mirror 9 l9e ) ! direct sight l9e f ano!r object1 to measure ! angle at ! position ( ! obs]v] subt5d$ by ! two objects1 0 orig9ally propos$ & work$ out 9 a mann] by ,hooke1#ch & also by ,newton4#ci ,newton's inv5tion 0 ! m simple & important4 ,?is 0 communicat$ to ,dr4 ,halley1 !n ,a/ronom] ,royal1 b x 0 left unpubli%$ until aft] 8 dea?1 :5 x 0 f\nd 9 ,newton's own h&writ+ among ,dr4 ,halley's pap]s4 ,newton employ$ two mirrors to obta9 ! reflection ( an object plac$ at any angle ( less ?an #ij to ! axis ( ! telescope or sight tube1 to ?r[ an image directly ?r\gh ! tube4 ,"o ( ^! mirrors 0 plac$ at an angle ( #de to ! axis ( ! telescope & cov]$ half its field ap]ture1 s t a direct image ( an object c\ld be receiv$ by ! eye f ! op5 uncov]$ "p ( ! telescope at ! same "t z ! reflect$ image ( ano!r object f ! mirror4 ,! second mirror 0 plac$ s z to ?r[ its reflection into ! mirror on ! end ( ! telescope )\t giv+ any ob/ruction to ! op5 ap]ture4 ,?is side mirror 0 fix$ ) ! c5tre ( its plane ov] ! axis ( a movable arm :i* read ^u an arc ! am\nt ( its angul> displacem5t to #ij4 ,! mirrors 7 s arrang$ t _! faces %\ld be p>allel to ea* o!r :5 ! movable arm 0 plac$ at ! z]o ( ! arc4 ,! graduation ( ! arc 0 ( d\ble ! clos5ess ( ! ord9>y arc read+1 s t ! angul> positions ( ! two mirrors 9 relation to ea* o!r 0 indicat$ accord+ to ! foll[+ law3-- ,t ! angle betwe5 two reflections 9 ! same plane is equal to twice ! incl9ation ( ! reflect+ surfaces to ea* o!r4 #faf4--;,hadley's ,quadrant4--,9 ,newton's quadrant ! arc 0 br\ght mo/ inconv5i5tly 9 front ( ! face4 ,by ,hadley's arrangem5t ! telescope or sight l9e is br\ght 9 a direction ab\t p>allel ) ! *ord ( ! arc1 produc+ ! v conv5i5t =m ( in/rum5t n[ 9 use4 ,?is in/rum5t 0 exhibit$ at ! ,royal ,society1 #ac? ,may1 #agca4dj ,x 0 tri$ exp]im5tally by ! ,a/ronom] ,royal1 ,augu/1 #agcb1 9 a ya*t excursion1 :5 read+s 7 tak5 satisfactorily )9 a m9ute ( arc4#da ,x aft]w>ds came into g5]al use4 ,! quadrant 0 at fir/ held to be suffici5t = measur+ ! sun's altitude = obta9+ latitude1 b ,hadley1 z e>ly z #agca1 saw ! advantage ( ext5d+ ! arc s z to be able to obs]ve ! opposite horizon if ! direct "o 0 obscur$4 ,x 0 also f\nd t measur+ ! moon's angul> di/ance f a /> beyond #ij 0 s]viceable 9 det]m9+ longitude4 ,he !re=e propos$ by a duplicate sy/em ( reflections to ext5d ! arc by :at is t]m$ a back sight to #bbj4 ,! means he sugge/$1 :i* 7 commonly c>ri$ out 9 in/rum5ts ( ! p]iod1 7 f\nd to be too complicat$ = practice4#db ,9 ! meantime ! con/ruction ( ^! in/rum5ts1 orig9ally fram$ ( a comb9ation ( wood1 ivory1 & metal1 0 mu* improv$ by mak+ ! frame entirely ( metal4 ,!re 7 also great improvem5ts made 9 ! optical p>ts1 by :i* ! arc ( #ij 0 ext5d$4 ,9 #ageg ,capta9 ,campbell _h an in/rum5t con/ruct$ ( metal ( #fj ( arc :i* !re=e read to #abj4 ,?is in/rum5t1 ) details ( improvem5t1 pr9cipally by ,ramsd51#dc became ! mod]n sextant4 #fag4--,reflect+ ,circle4--,z soon z ! success ( ! sextant 0 assur$ !re appe>$ to be a g5]al desire to complete ! circle by reflections1 _m inv5tors ?9k+ ?is w\ld possess great advantages ov] ! arc ( #abj1 & we f9d !re=e no lack ( inv5tions to ?is end1 ev5 by em95t m54 ,reflect+ circles1 z !y are t]m$1 t 7 ( suffici5t m]it to come into limit$ use1 7 design$ by ,may]1 #aggj2 ,borda1 #aghg2 ,m5doza1 #ahja2 ,hassl]1 #ahbd2 ,fayr]1 #ahcj4 ,tr\ghton's circle ( ab\t ?is p]iod 0 no d\bt ! be/ in/rum5t ( ! class4#dd ,we h also m]itori\s reflect+ circles by ,pi/or & ,m>t9s1 & by ,amici4#de ,al?\gh ^! in/rum5ts 7 us$ at sea to a limit$ ext5t1 p>ticul>ly on =eign %ips1 !y 7 also us$ on l&1 :]e inde$ !y 7 m manageable4 ,z no fur!r ref]5ce to ^! reflect+ circles w be giv51 anyone int]e/$ 9 ! matt] may ref] to ! books m5tion$ 9 ! notes1 :]e v full p>ticul>s ( _! /ructure are giv54 ,x 0 felt necess>y to m5tion ! subject "h1 z ! same ideas are con/antly cropp+ up z assum$ advantages :]e previ\s exp]i5ce is =gott54 ,reflect+ in/rum5ts at sea are t$i\s to use :5 ! angle to be tak5 exce$s t tak5 9 by ! eye )\t movem5t ( ! :ole body4 ,on l&1 :5 ! angle exce$s #abj1 a !odolite is bett]2 b supplem5t>y angles may be tak5 ) ! sextant conv5i5tly on l&1 :]e ! portability ( ! in/rum5t is ( great consid]ation4 ,?is w be aga9 br\ght =w>d 9 discuss+ box sextants ) supplem5t>y arc4 #fah4--,! ,sextant1 ( ! inv5tion ( :i* "s p>ticul>s h j be5 giv51 is only us$ z a survey+ in/rum5t = ! exploration ( new c\ntries1 = :i* employm5t--x may be us$ ) or )\t a tripod or /&--x is f\nd to be a mo/ conv5i5t1 light1 & portable in/rum5t = ! travell] = asc]ta9+ longitude1 latitude1 & "t ) ! aid only ( an artificial horizon4 ,triangulation may also be tak5 ) x ( t]re/rial objects1 ev5 = ! complete circle1 by repetitions f /ation to /ation 9 angles )9 #abj4 ,! same pr9ciples :i* are foll[$ 9 ! con/ruction ( ! nautical sextant are foll[$ also 9 ! manufacture ( two modifi$ =ms ( ?is sextant :i* are us$ = survey+ only1 ! s\nd+ sextant & ! box sextant4 ,z ! nautical sextant is mo/ op5 to obs]vation ( its p>ts x w be m conv5i5t to discuss ! con/ruction & g5]al arrangem5ts ( ?is in/rum5t fir/4 #fai4--,optical ,arrangem5ts ( ! ,sextant4--,newton 9 ! description ( 8 in/rum5t plac$ ! mirrors p>allel to ea* o!r1 t is1 to z]o ( ! arc1 9 8 illu/ration = ! demon/ration ( ! pr9ciple4 ,9 ?is position he %[$ t ! direction ( ! reflect$ ray is co9cid5t ) ! direct ray ent]+ ! eye f ! same object or />4 ,?is s*eme ! au?or has g5]ally f\nd ! cle>e/ = illu/rat+ ! pr9ciple to p]sons n well acqua9t$ ) optics1 !re be+ "s difficulty 9 expla9+ ! law j giv51 art4 #fae1 f a m complicat$ s*eme4 ,illu/ration3 ,fig4 #bhc4--,reflection 9 direct l9e f two pla9 mirrors4 #fbj4--;,if two mirrors be plac$ ) _! faces p>allel to ea* o!r 9 su* a mann] t a ray ( light may cont9ue aft] two reflections f !m1 ! ray w cont9ue its pa? p>allel 9 its direction to its incid5ce ^u ! fir/ mirror4 ,let ,,mm1 ,fig4 #bhc1 be two mirrors plac$ ) _! faces opposite & p>allel to ea* o!r4 ,let ! incid5t ray ,,im fall on ! mirror ,m ^: normal is a4 ,!n1 z ! angles ( incid5ce & reflection are equal1 art4 #ed1 x w be reflect$ at equal & opposite angle to ! normal to ,m4 ,let ! normal ( ,m be a4 ,!n aga91 ! incid5t l9e ,,mm w be reflect$ at equal angles to ! normal to ,d1 t is1 z %[n by ! diagram1 x w cont9ue p>allel ) ! incid5t ray & 9 su* a position t an object at ,p w\ld appe> to ! eye1 plac$ at ,d1 z ?\gh x 7 at ,p 9 ! direct l9e ( sight4 #fba4--,p>allax4--,x w be se5 by ! figure t ! po9t ,p does n appe> to ! eye at ,d 9 its true position b at ,p !re=e ) ! mirrors ,,mm q p>allel1 ! po9ts ,p & ,p appe> co9cid5t1 & w\ld read z "o po9t ) ! index ( ! sextant set at z]o1 t is1 at ! position :5 ! mirrors are p>allel to ea* o!r2 :]eas ! po9ts ,p & ,p really subt5d a small angle if direct l9es be drawn f !m to ,d4 ,x is !re=e cle> t ! angle read by co9cid5t reflection & direct or1 z x is sometimes call$1 visual image is less ?an ! true angle at ab\t ! position %[n4 ,?is diff]5ce is call$ ! error ( p>allax4 ,:5 ! object is di/ant ?is error is immeasurably small4 ,! p>allax error v>ies proportionately to ! di/ance ( ! mirrors ap>t & ) _! angul> position4 ,if ! mirrors are 9 su* an angul> position t ! rays proce$+ f an object imp++ ^u ! c5tre ( ! fir/ mirror w\ld1 if cont9u$1 rea* ! eye1 !re w\ld be no error ( p>allax4 ,?is occurs 9 ! nautical sextant at ab\t #fj1 & ! p>allax error increases on ei!r side ( ?is po9t4 #fbb4--;,9 ! practice ( survey+ ?is small error is neglect$4 ,:5 ! box sextant is us$ ! mirrors are plac$ at a v small di/ance ap>t1 & ! p>allax error !re=e is extremely small ev5 = ne> objects4 ,:]e two objects are to be triangulat$1 ! "o ne> & ! o!r di/ant1 ! p>allax error is mu* decreas$ or elim9at$ by tak+ ! ne> object by direct vision1 & ! di/ant object by reflection4 ,9 ?is case1 if ! ne> object be t[>ds ! "r h&1 ! sextant mu/ be us$ 9 an inv]t$ position4 ,if ! two objects be bo? ne>1 a di/ant object may be sight$ 9 ! direction ( "o ( !m = ! reflect$ image4 #fbc4--;,x is readily se5 t if ! p>allelism ( ! glasses %[n 9 ! figure be di/urb$1 say by a *ange 9 ! relative angul> position ( ,m s t ! planes ,m & ,m cont9u$ to subt5d an angle to ea* o!r1 !n ! normal ( ,m mu/ also be *ang$ 9 direction equal to ?is2 b ! ray ,,mm rema9+ con/ant1 z !re is no movem5t ( ,m1 ?is ray w !re=e be displac$ 9 its reflection f ,m an am\nt equal to ! angle ( incid5ce on ,m f its normal1 plus ! angle ( reflection f ! opposite side ( ! normal1 t is1 to d\ble ! am\nt ( angul> *ange ( ! position ( ! mirror or ( its normal1 :i* is ! same ?+4 ,! sextant !re=e reads1 by *ange ( position ( "o ( its mirrors1 half ! angle ( reflection ^u its arc2 & to make x read to ! angul> value ( its reflection ! divisions on ! arc are made twice z close1 t is1 half degrees are made to read z degrees4 ,?is w be bett] expla9$ by ! foll[+ s*eme4-- ,illu/ration3 ,fig4 #bhd4--,pr9ciples ( reflection ( ! sextant4 #fbd4--,! above s*eme1 ,fig4 #bhd1 is tak5 f ,capta9 ,magnaghi's admirable "w be=e m5tion$1 :i* gives a v cle> geometrical demon/ration ( ! value ( angul> positions 9 comp\nd reflection4 ,a ray ( light ,,sr direct$ to a plane mirror ,r is reflect$ !refrom to a plane mirror ,r1 foll[+ a plane ( reflection p]p5dicul> to ! int]section ( ! two mirrors4 ,! direction ,r,t ( ! ray reflect$ by ! second mirror falls into ! same plane ( reflection1 & makes ) ! direction ,,sa ( ! incid5t ray an angle d\ble t :i* is compris$ betwe5 ! two mirrors4 ,! two planes ( reflection ,,sab & ,,abt unite 9 "o because !y bo? conta9 ! l9e ,,ab & ! normal ,,bp to ! mirror ,r4 ,9 prolong+ ! normals ( ! mirrors to _! po9t ( int]section ,p we f9d t-- ,,bts ,,bas - ,,abt2 b z ,,bas - ,,abt ,,bpa ,,bda1 !re=e ,,bts #b ,,bda4 #fbe4--,! mirrors be+ plac$ 9 ! position %[n 9 ! figure1 if we look ?r\gh a telescope ^: visual axis is plac$ 9 ! l9e ,,et1 ) its objective to ! mirror ,r1 we see 9 ! c5tre ( ! field ( view ! image ( ! object ,s reflect$ consecutively by ! mirrors ,r & ,r4 ,we also see 9 ! telescope :e!r ! mirror ,r is only a c]ta9 height above ! plane ( reflection1 s z to p]mit half ( ! object-glass to receive ! rays com+ f ! po9t ,e situat$ 9 ! prolongation ( ! l9e ,,tb1 also ! image ( ,e :i* is necess>ily co9cid5t ) t ( ,s1 because ! rays by :i* ea* image is =m$ ent] ! telescope 9 ! same direction ,,bt4 ,!re=e :5 ! images ( ! two objects ,e & ,s appe> sup]impos$ or co9cid5t 9 ! middle ( ! field ( view1 we h an index giv5 t ! mirrors =m an angle ) ea* o!r :i* is half t :i* is made at ! po9t ,t f ! same objects1 & :5 "o is kn[n ! o!r is easily d$uc$4 #fbf4--,nautical ,sextant4--,! ord9>y con/ruction ( ?is in/rum5t1 ,fig4 #bhe1 consi/s ( a ca/ gun-metal frame1 =m+ approximately 9 outl9e a segm5t ( a circul> disc ,,aa includ+ )9 its extreme radii ab\t #aee4 ,illu/ration3 ,fig4 #bhe4--,nautical or a/ronomical sextant4 #fbg4--,! ,limb ,g1 :i* is made only ab\t #a_/ab in* 9 ?ickness1 has g5]ally a face ( ab\t in* 9 wid?1 :i* is inlaid ) silv] or plat9um1 z ,fig4 #abg1 p4 #ahf1 to take ! graduation to ab\t #adj4 ,! limb is /iff5$ by a deep1 ?9 rib ab\t in* wide1 support$ by a corn] holl[4 ,! ext]ior radial arms & int]space fram+1 ,fig4 #bhe ,,mm1 :i* v>y v mu* 9 design accord+ to ! ta/e ( ! mak]1 is made g5]ally ( ab\t #a_/ad ( an in* 9 wid? ^u ! face ( ! b>s1 ) a dep? ( #c_/h in*4 ,?is arrangem5t ( ! b>s plac$ edgewise gives great /iffness to ! surface ( ! arc ) little weight4 ,a h&le ,l1 made g5]ally ( ebony1 is support$ on two /&>ds or brace-pieces ,n1 :i* are c>ri$ (f to ab\t #b in*es f ! back ( ! frame to hold ! h&le p>allel ) ! face4 ,! h&le has sometimes a hole bu%$ ?r\gh x ) metal1 to support ! sextant ^u a correspond+ p9 =m+ "p ( a /& or tripod :5 ! in/rum5t is us$ = tak+ obs]vations on l&4 ,?ree feet are plac$ at ! corn]s ( ! frame ( ! sextant1 "o %[n at ,q1 to support x conv5i5tly on a table to take ! read+ ( an obs]vation j made4 #fbh4--;,at ! c5tre ( ! arc a female axis ( ab\t #a in*es 9 dep? ,e is atta*$ by ?ree screws to ! frame p]p5dicul> to ! plane ( graduation4 ,?is c>ries ! male axis1 :i* c5tres ! v]ni] on ! v]ni] arm ,m4 ,! axis is cov]$ by a protect+ tube :i* =ms "o ( ! ?ree feet ^u :i* ! in/rum5t re/s :5 laid d[n4 ,! v]ni] arm is made ( gun-metal ( ab\t #a_/af in* 9 ?ickness & f #a in* dim9i%+ to in* 9 wid?4 ,?is is /iff5$ by a light rib on its upp] side4 #fbi4--,! ,v]ni] ,v reads ^u an #h-;in* sextant1 t is1 "o ( eight in*es radius1 to #aj1 ! graduations be+ to #bj & ! v]ni] tak+ #abj divisions4 ,a description ( ! v]ni] read+ 0 giv51 art4 #cah4 ,! v]ni] falls ^u ! arc on ! plan %[n ,fig4 #abg1 p4 #ahf4 ,x is clamp$ ne> to position by ! mill$-head$ screw ,h1 & is adju/$ by ! tang5t ,i4 ,a magnifi] ,j is plac$ on a jo9t$ sl+-piece ,k :i* trav]ses ! v]ni]4 ,?is is sometimes provid$ ) a gr\nd glass %ade to dull ! silv] = read+4 ,! sl+-piece moves ! magnifi] opposite to any division ( ! v]ni]4 #fcj4--,ov] ! axis ( ! v]ni] arm a l>ge1 oblong mirror1 t]m$ ! index glass1 ,a1 is fix$ ) its face 9 a plane cutt+ ! c5tre ( ! axis4 ,! index glass is plac$ ) its longe/ sides approximately 9 l9e ) ! v]ni] arm4 ,?is mirror is plac$ 9 a metal tray & is sometimes made adju/able by ?ree screws2 b x is bett] fix$ by ! mak] by screw+ ! flange-piece1 :i* =ms "o end ( ! tray1 h>d d[n4 ,! index glass moves ) ! index arm & gives ! fir/ reflection ( sun1 moon1 or /> :i* falls !nce ^u ! horizon glass ,b4 #fca4--,! ,horizon ,glass ,b is plac$ ^u a spur-piece =m$ 9 ! same ca/+ z ! frame4 ,?is glass1 :i* is work$ p]fectly p>allel1 has ! l[] half ( its surface next ! frame silv]$4 ,! silv] is cut to a %>p l9e aga9/ ! pla9 "p4 ,! horizon glass plac$ 9 its metal tray has adju/m5ts giv5 to x by means ( cap/an-head$ screws 9 a mann] t w be pres5tly describ$4 #fcb4--,! ,telescope screws into a r+ fitt$ at ,r1 :i* /&s ^u a b> erect f ne> ! edge ( ! frame4 ,! female screw by :i* ! telescope is held is =m$ ( two r+s :i* adju/ = ! am\nt & direction ( sep>ation1 s t ! telescope may be direct$ co9cid5t ) ! horizon glass4 ,! b> or /&>d supports ! r+ fitt+ & is made ( ei!r squ>e or triangul> section1 fitt$ accurately 9 a deep socket fitt+1 9 :i* x slides to raise or l[] ! r+ by means ( a mill$-head$ screw plac$ on ! end ( ! b>4 ,?is p]mits adju/m5t only suffici5t to br+ ! axis ( ! telescope opposite ! l9e ( division betwe5 ! pla9 & silv]$ p>ts ( ! horizon glass4 #fcc4--;,f\r ,circul> ,%ades1 c>ri$ 9 squ>e frames fitt$ ) d>k blui%-grey glasses1 are jo9t$ to ! frame at ,c4 ,^! h nib-pieces at ! upp] corn]s1 s t "o or m ( ! %ades may be turn$ up at a "t by ! f+]-nail to int]cept any surplus am\nt ( light f a lum9\s body reflect$ f ! index-glass2 or ! :ole ( ! %ades may be turn$ up :5 obs]vation is made ( ! mid-day sun4 ,?ree o!r simil> %ades1 b plac$ 9 circul> frames are fix$ at ,d1 :i* h+e ov] & back1 to be ?r[n 9 or out ( int]ception1 & are us$ to subdue ! light f ! horizon if requir$4 #fcd4--,! ,telescopes us$ z a "p ( ! sextant are g5]ally two 9 numb]4 ,"o = direct vision is a %ort tube ( ab\t #c in*es 9 l5g?1 focuss+ at ab\t #d in*es4 ,! optical arrangem5t is ! same z t ( an op]a glass1 consi/+ ( an a*romatic object-glass ( ab\t #d in*es focus & a concave eye-glass ( ab\t #b in*es negative focus1 ,fig4 #ad4 ,! second telescope is ab\t #g in*es to #h in*es 9 l5g?4 ,?is has two ,huyg5ian eye-pieces1 :i* h ea* a wir$ diaphragm at ! mutual focus ( ! eye-piece & ! object-glass4 ,"o ( ^! has two f9e wires plac$ p>allel = use 9 adju/+ ! telescope1 & ! o!r has two pairs ( cross$ wires to indicate ! c5tre ( ! field ( view4 ,!re is also a pla9 p9-hole sight provid$ = op5 vision4 #fce4--,! ,case 9 :i* ! in/rum5t is pack$ is g5]ally made ( well-season$ mahogany1 dovetail$ toge!r at its corn]s4 ,! fitt+s are made to put ! in/rum5t back 9 its case z x 0 la/ us$ )9 a wide range4 ,a tommy-p9 = adju/m5ts & a h& magnifi] are suppli$ ) ! in/rum5t4 ,! case is g5]ally ,fr5* poli%$ inside z well z out to prev5t absorption ( moi/ure f sea air4 #fcf4--,manufacture & ,exam9ation ( ! ,nautical ,sextant4--,besides ! g5]al good "w t ?is in/rum5t dem&s1 ! important po9ts to be obs]v$ are1 t ! glasses %\ld be ( h>d cr[n glass work$ p]fectly p>allel f face to face2 !y %\ld also be well poli%$4 ,^! obs]vations apply to bo? ! reflect+ glasses & ! %ades4 ,! silv]+ ( ! mirror %\ld be protect$ ) a good coat+ ( copal v>ni%4 ,! mirrors %\ld be held by ?ree po9ts only1 & be q free f /ra94 ,! upp] ( ! ?ree po9ts %\ld deta*1 s z to be able to remove ! glass at any "t = resilv]+4 ,! axis %\ld be fitt$ ) all ! c>e necess>y = a !odolite1 & be plac$ truly c5tral to ! arc4 ,! extremity ( ! v]ni] arm :5 free ( its clamp %\ld trav]se ! arc at equal di/ance f its face & move ) v light friction4 ,! extreme l9es ( ! v]ni] %\ld cut equal divisions all along ! arc #j to #adj1 obs]vations be+ tak5 p>ticul>ly at bo? ends & 9 ! c5tre ( ! arc4 ,! v]ni] %\ld lie flat on ! limb f end to end ( ! arc4 ,! /&>d or /em-piece = elevat+ ! telescope %\ld move upw>ds & d[nw>ds /iffly b equally by ! motion ( its mill$-head$ screw4 ,! division l9es ( ! limb & v]ni] %\ld be cut f9e b v deep3 !y %\ld be cut on ! divid+ eng9e f ! axis ( ! sextant to ensure true c5tr+ ( ! arc1 & n z 9 ! usual plan ( hav+ ! axis adju/$ to ! divisions4 ,illu/ration3 ,fig4 #bhf4--,section ( axis & index glass ( sextant4 ,illu/ration3 ,fig4 #bhg4--,section ( limb & clamp & tang5t4 #fcg4--;,axis4--,?is is ! mo/ important "p ( ! in/rum5t1 & requires ! greate/ c>e 9 con/ruction4 ,fig4 #bhf repres5ts ?is to a scale half size4 a ! axis1 made ( h>d gun-metal1 has a coll> by :i* x is atta*$ to ! index arm4 ,! axis is gr\nd & burni%$ c>efully into ,s ! socket-piece1 :i* is fitt$ into ! frame & held d[n by ?ree screws4 ,at ! end ( ! socket !re is a coll>-piece ,b atta*$ ^u an angul> or tight conical fitt+ by ! screw ,d1 :i* prev5ts ! axis ris+ out ( its socket4 ,! axis is cov]$ by a cap ,l :i* protects x f injury1 & ?is at ! same "t =ms a leg to ! in/rum5t z be=e m5tion$4 ,! index glass ,i is m\nt$ 9 a tray ,t %[n 9 section4 ,!re are two po9ts ( contact at ! l[] "p ( ! back ( ?is glass1 =m$ by p9s1 & "o po9t ( adju/m5t press+ aga9/ ! clip ,g by a spr+ ,c 9 front1 act+ contra to a screw at ! back ,e1 :i* adju/s only a small di/ance to br+ ! index glass to p]p5dicul>ity4 ,! flange-piece ,f is adju/$ 9 ! manufacture s z to leave v small sep>ate adju/+ to ! index glass necess>y4 #fch4--,section ( ! ,limb & ,clamp & ,tang5t4--,! g5]al arrangem5t is %[n 9 ,fig4 #bhg4 ,m arms ( ! frame2 ,j section ( ! limb2 ,c clamp atta*$ to ! tang5t ,n = clamp & tang5t motion1 describ$ art4 #cdf2 ,o mill$ head to clamp2 ,n mill$ head to tang5t4 ,! v]ni] is %[n at ,v1 read+ ?r\gh an op5+ on ! face ( ! index arm ,p4 ,! rib to /iff5 ?is arm is %[n at ,r4 ,illu/ration3 ,fig4 #bhh4--,v]tical section ( horizon glass4 ,illu/ration3 ,fig4 #bhi4--,plan ( section ,a to ,b4 #fci4--,! ,adju/m5t ,arrangem5t ( ! ,horizon ,glass4--,?is mo/ important adju/m5t is con/ruct$ 9 v>i\s ways4 ,! plan n[ g5]ally ?\ght to be ! be/ is = ! mak] to fix ! horizon glass frame firmly 9 its true position p]fectly p]p5dicul> to ! surface ( ! frame1 & to all[ a small am\nt ( adju/m5t to ! glass only4 ,a conv5i5t plan ( do+ ?is is %[n 9 ! v]tical section full size 9 ,fig4 #bhh4 ,! frame ,,ff is made 9 "o ca/+1 :i* has its base coll> firmly fix$ to ! frame ( ! sextant4 ,fig4 #bhi is a cross section ,a to ,b4 ,h ! horizon glass is held ^u its face by ?ree po9ts1 "o ( :i* is %[n at ,l1 :i* is plac$ 9 ! c5tre ( ! top4 ,! l[] front po9ts are ! ext]ior corn]s ( a plate :i* is cut away betwe54 ,?is plate is held by ! screw ,g4 ,! screw ,g =ms a k9d ( h+e :i*1 toge!r ) ! ela/icity ( ! plate1 gives a slight pressure direct+ ! glass h>d ^u ! po9ts ( ! screws ,j & ,q4 ,! screw ,j resi/s ?is pressure lightly & p]mits adju/m5t ( ! horizon glass ,h to angul> position 9 relation to ! plane ( ! index glass to a small ext5t1 by means ( a p9 plac$ 9 ! cap/an head ,j4 ,! p]p5dicul> position ( ! horizon glass1 ,h1 is secur$ by slight adju/m5t ( ! cap/an head ,k1 :i* moves aga9/ a spr+ ,l 9 ! v]tical c5tre ( ! top ( ,h4 ,?is piece1 ) screw & spr+1 is atta*$ to ! horizon glass frame ,,ff by ! screw ,m1 s t x may be easily remov$ to replace or resilv] ! glass4 ,! silv] on ! glass is cut to a %>p l9e at ab\t ! po9t ,h ) a razor4 #fdj4--,te/+ ! ,p>allelism ( ! ,surfaces ( ! ,glasses4--,! be/ me?od is to firmly fix a telescope provid$ ) webb$ or po9t$ index diaphragm s t ! webs or po9ts cut a di/ant1 %>ply def9$ object1 or its edge only1 q cle>ly4 ,if ! glass to be te/$ be n[ plac$ 9 f\r directions agree+ ) its f\r sides 9 front ( ! object-glass ( ! telescope1 & x is work$ p]fectly p>allel1 & is free f /ri1 ! di/ant object w n appe> to be displac$ by its pres5ce 9 ! slighte/ degree at any position4 ,if ! glass be n m\nt$ & is q squ>e1 %\ld !re be any v small error1 ! ?icke/ or ?9ne/ edge %\ld be plac$ t[>ds ! frame2 b 9 ?is case only a v small error is p]missible4 ,! col\r$ glasses require ! same te/ z ! :ite ones4 ,:]e ! p>allel glass to be te/$ is small1 ! object-glass ( ! telescope may be cov]$ by a pap] cap1 ) a small hole only left ?r\gh its c5tre1 suffici5t to take ! glass4 #fda4--,! glasses1 :5 fix$ 9 ! sextant1 may be exam9$ = p>allelism approximately by sett+ !m end up s+ly to ! sun1 ) ! sextant set at an angle t ! direct & reflect$ images ( ! sun's limb appe> j to t\*1 ! eye-piece ( ! telescope be+ con/antly cov]$ by ! sun-glass4 ,if !re be a want ( p>allelism1 ! image w be di/urb$4 ,"o reason t ! telescopic plan fir/ propos$ is bett] to be foll[$ 9 ! con/ruction ( ! in/rum5t1 is t ! telescope is fix$ & t !re is no indi/9ctness f unavoidable motion ( ! body1 su* z occurs :5 ! sextant is held 9 ! h&4 #fdb4--,! ,quality ( ! ,surfaces ( ! ,glasses may be exam9$1 bo? = flatness & brightness & = equality ( d5sity1 by hold+ !m s t ! reflect$ image ( a /raight body1 z = in/ance a /ret*$ ?9 /r+ plac$ at a di/ance1 may be obs]v$ by reflection 9 glanc+ ov] ! surfaces ) ! eye ne>ly p>allel ) its plane4 ,if ! glass be imp]fect ! image t rea*es ! eye w appe> to be wavy4 ,if ! reflection appe> mi/y1 ?is is g5]ally due to want ( p>allelism ( ! glass2 b ?is mode ( obs]vation is altoge!r some:at te*nical & difficult to atta9 )\t skill4 #fdc4--,to ,silv] ! ,index or ,horizon ,glass ) ,m]cury4--,clean ! glass ?or\ghly by boil+ x 9 wat] conta9+ an alkali 7pota% or soda71 & !n poli% x (f ) :it+ & wat]1 us+ a clean piece ( old l95 or p]fectly clean wa%-lea!r4 ,d n t\* ! surface ) ! f+]s4 ,take a piece ( clean t9-foil fre%ly op5$ f ! roll & cut out a piece slightly l>g] ?an ! glass to be silv]$4 ,lay ?is ^u a smoo? pad--an old lea!r book-cov] answ]s4 ,place a s+le drop ( clean m]cury ab\t ! size ( an ord9>y %ot ^u ! t9-foil & rub ?is g5tly ov] ! surface until x is entirely silv]$4 ,n[ p\r v g5tly suffici5t m]cury ^u ! foil till ! surface appe>s to be flood$4 ,take a %>ply cut /raight-edge =m$ ( /iff writ+-pap]1 & draw ?is ov] ! surface ( ! m]cury to cle> x4 ,take a slip ( clean smoo? writ+-pap] v little wid] ?an ! foil & ( ab\t "o & a half times its l5g?3 spr+ ! pap] to a slight curve & place "o "p ( x ov] ! silv]$ foil s t :5 x spr+s op5 x w cov] x & exclude ! air f ! surface4 ,n[ give ! glass a f9al poli% & lay x ^u ! pap] ov] ! foil4 ,hold ! glass d[n ) slight pressure ) ! left h&1 & sl[ly & /eadily draw out ! slip ( pap] 9 ! l9e> direction ( ! surface ( ! glass ) ! "r h&4 ,?is w take out ! air betwe5 ! foil & ! glass1 s z to br+ ! m]cury 9 contact & leave a p]fect mirror4 ,x mu/ n[ be set aside ) ! glass turn$ face d[nw>ds 9 an incl9$ position1 s t ! surplus m]cury may dra9 (f f ! foil4 ,small slips ( foil %\ld be put at its l[] edge1 :i*1 by _! attraction = ! m]cury1 w accel]ate ! dra9+4 ,! mirror %\ld n be t\*$ aft] sett+ x up to dra9 = twelve h\rs at lea/1 aft] :i* ! surplus foil may be trimm$ (f4 ,aft] ano!r ?irty h\rs or m x may h any v>ni% or o!r protection appli$ to ! back ( ! silv]4 #fdd4--,:]e in/rum5ts are tak5 abroad m]cury silv]+ may become spott$1 s t a small /ore ( m]cury & t9-foil %\ld be tak5 out ) ! sextant = resilv]+4 ,b x %\ld be p>ticul>ly obs]v$ t ! m]cury %\ld nev] be plac$ 9 ! same case ) ! in/rum5t1 z ! smalle/ p>ticle1 if x t\* ! frame1 w eat into ! brass & de/roy its /r5g?4 ,seal+-wax dissolv$ 9 _s answ]s = a v>ni% at ! back ( ! foil fairly well aft] resilv]+ if prop] v>ni% be n at h&4 ,x is advisable be=e attempt+ to silv] a sextant mirror to practise on a few slips ( ord9>y glass 9 ord] to get into ! way ( do+ x4 ,9 mod]n practice base silv] is deposit$1 & no m]cury is us$1 b ! process requires special skill4 #fde4--;,adju/m5t ( ! ,index ,glass4--,hold ! sextant clamp$ to ab\t #fj 9 a horizontal position ) ! index glass ne> ! eye4 ,look ne>ly along ! plane ( ! glass 9 su* a mann] z to be able to see "o "p ( ! plane ( ! arc by direct vision1 & ano!r "p by reflection ( x at ! same "t4 ,if ! direct view & ! reflect$ jo9 9 "o l9e1 & ! arc appe>s z ! cont9uity ( a s+le plane1 ! index glass is p]p5dicul> to ! plane ( ! sextant4 ,if ?is be n ! case x c be adju/$ by turn+ ! set screw plac$ at ! back ( its upp] c5tre1 ,fig4 #bhf ,e1 v g5tly4 #fdf4--;,adju/m5t ( ! ,horizon ,glass to ,p]p5dicul>ity4--,place ! v]ni] at z]o4 ,hold ! plane ( ! sextant p>allel to ! horizon & obs]ve if ! image ( ! horizon se5 by reflection at ! edge ( ! silv] l9e co9cides exactly ) ! image receiv$ directly ?r\gh ! pla9 "p ( ! glass4 ,if x does s ! horizon glass is p]p5dicul> to ! plane ( ! in/rum5t1 t is1 assum+ ! index glass is also p]p5dicul>4 ,9 ?is adju/m5t x is well to rock ! plane ( ! in/rum5t say #bj1 to see t ! horizon is cut z a cle> l9e ab\t its horizontal position = ?is am\nt ( angle4 ,if ! mirror be n p]p5dicul> adju/ g5tly by ! s+le screw at ! top ( ! horizon glass frame4 ,if ! horizon be n wat]1 ! %>p outl9e ( any di/9ct di/ant object w answ]1 or a piece ( f9e /r+ plac$ at a di/ance & /ret*$ /raight4 #fdg4--;,adju/m5t = ,index4--,?is is ! adju/m5t = p>allelism ( ! two mirrors at ! z]o ( ! arc4 ,! sextant is clamp$ at z]o z be=e3 ! arc ( ! in/rum5t is turn$ 9 a v]tical position & ! horizon aga9 obs]v$4 ,if ?is appe>s to cut a cle> l9e ?r\gh ! pla9 glass & ! mirror !re is no index error1 & ! planes ( ! glasses are truly p>allel to ea* o!r 9 ?is position4 ,if ! l9e is n cont9u\s adju/ g5tly by ! l[] screw1 ,fig4 #bhh1 at ,g4 #fdh4--;,adju/m5t ( ! ,horizon ,glass by ! ,sun4--,?is is a bett] adju/m5t ?an t giv5 above1 except t x introduces any error t may be due to ! imp]fection ( ! %ades2 & x is m difficult p>ticul>ly = ! fir/ approximate adju/m5t4 ,arrange ! telescope & %ades s t a cle> outl9e ( ! sun's limb may be obs]v$ )\t di/ress+ ! eye4 ,place ! v]ni] at z]o4 ,obs]ve ! sun1 :i* w be mo/ conv5i5tly sight$ at ab\t #dj elevation1 fir/ ) ! plane ( ! frame v]tical1 & !n horizontally p]p5dicul> to ?is4 ,if ! sun pres5ts a r\nd disc 9 bo? ^! positions ! sextant is 9 adju/m5t4 ,if 9 ! v]tical position !re appe>s to be a small not* at top & bottom ( ! sun's limb1 ! glass is n p]p5dicul> to ! plane ( ! in/rum5t1 & ?is requires adju/m5t by ! screw at ,fig4 #bhh ,k4 ,if not*es appe> at ! sides ( ! limb :5 x is held horizontally !re is an index error1 :i* may be adju/$ at ,g if x be small4 #fdi4--;,index ,error aft] ,adju/m5t ,all[ance4--,! limb ( ! sextant is graduat$ #e beyond ! z]o position :5 ! glasses are p>allel to ea* o!r4 ,?is is call$ ! arc ( excess4 ,! v]ni] is also divid$ ?ree l9es beyond its z]o position1 :i* is m>k$ by an arr[4 ,^! extra divisions are plac$ on ! in/rum5t = correct+ ! index error by measurem5t ( ! angle subt5d$ by ! diamet] ( ! sun's disc alt]nately on "o side & ! o!r ( ! z]o l9e1 9 :i* obs]vations1 if ! two read+s agree1 ! sextant mu/ be 9 p]fect adju/m5t2 :5 !y d n agree half ! error may be adju/$ by ! horizon glass4 ,! same obs]vations may also be made ) a bright /> by sett+ ! index alt]nately on "o & ! o!r side ( z]o4 ,:5 ! sun is us$ ! reflect$ & direct images are br\ght toge!r1 s t ! two suns t appe> 9 ! in/rum5t j t\* limb to limb1 fir/ ^u direct read+ & !n ^u ! arc ( excess4 ,:5 ! division is adju/$ v ne>ly1 any small error1 plus or m9us1 may be all[$ z a con/ant = all read+s4 ,9 obs]vations ( ! sun c>e %\ld be tak5 t ! eye is protect$1 bo? by ! sun-glass cov] to ! telescope & by suffici5t use ( ! %ades4 #fej4--;,adju/m5t ( ! ,telescope to ,set its ,axis ,p>allel to ! ,plane ( ! ,sextant4--,9 fix+ up ! in/rum5t aft] manufacture1 ! r+ /&>d :i* c>ries ! telescope is set at a measur$ di/ance f ! plane ( ! frame1 s t ! c5tre ( ! r+ co9cides ) ! height ( ! silv] l9e cut on ! horizon glass4 ,?is is necess>ily a prim>y adju/m5t4 ,= f9al adju/m5t ! long1 inv]t+ telescope is screw$ home 9 ! r+1 & ! eye-piece :i* has two p>allel wires across its diaphragm plac$ 9 x4 ,! telescope is br\ght to focus on any di/ant object1 ! eye-piece be+ turn$ at ! same "t to br+ ! wires p>allel ) ! face ( ! in/rum5t4 ,two objects are tak5 subt5d+ an angle ( #ij or ov]1--z ! sun & moon1 or ! moon & a bright />1--& ! index is mov$ s z to br+ ! objects1 say ! limbs ( sun & moon1 9 contact ) ! wire ne>e/ to ! sextant1 & fix$ !re4 ,!n by *ang+ ! position ( ! in/rum5t a little1 ! images are made to appe> ^u ! wire fur!/ f ! sextant4 ,if ! limbs ( ! sun & moon /ill rema9 9 exact contact z !y appe>$ be=e1 ! axis ( ! telescope is truly adju/$4 ,if ! limbs ( ! two objects appe> to sep>ate at ! wire fur!/ f ! sextant1 ! r+-adju/+ screw fur!/ mu/ be loos5$ a v little & ! screw ne>e/ ! sextant tight5$ ! same am\nt4 ,if ! rev]se1 & ! images appe> to ov]lap1 adju/ 9 ! rev]se direction4 ,by repeat+ ?is op]ation a few times ! contact w appe> to be ! same at bo? wires1 & ! axis ( ! telescope w be 9 collimation1 t is p>allel ) ! plane ( ! in/rum5t4 ,aft] ! telescope is truly adju/$ x may be rais$ or l[]$ a little to make ! reflect$ & direct images appe> equally cle>4 #fea4--;,f9al ,exam9ation ( ! ,sextant4--,x w be readily se5 t an in/rum5t1 al?\gh correct 9 !ory b dep5d+ ^u p]fection ( workman%ip 9 c5tr+1 division1 surface & p>allelism ( glasses1 & also 9 its adju/m5ts1 c sc>cely be br\ght to p]fection4 ,! errors g5]ally increase f ! z]o po9t1 :]e adju/m5ts are possible1 & are greate/ at #adj4 ,9 ! ord9>y comm]cial sextant ( ! deal]s ! errors ( c5tr+ alone are commonly #c m9utes to #e m9utes1 ) l errors 9 o!r p>ts4 ,x is !re=e bett]1 :]e ! sextant has to be absolutely reli$ ^u1 to subject x to actual trial4 ,! z]o po9t c be readily fix$ by rules already giv52 besides ?is ! m]idian altitude ( sev]al bright />s subt5d+ angles ( ab\t #cj1 #fj1 #ij1 & #abj %\ld be measur$ ei!r f a cle> horizon or f a m]cury artificial horizon1 to be describ$ pres5tly1 = angles "u #fj1 & ! errors plus or m9us tabulat$4 ,! data = ! m]idian altitudes ( c]ta9 />s ^u any night may be tak5 f ! ,nautical ,almanac1 :i* w require correction = ! latitude & longitude ( ! obs]v]4 ,?is subject is too complicat$ to be ent]$ ^u 9 detail "h4 ,at ! pres5t "t ! ,national ,physical ,laboratory und]takes ! exam9ation ( sextants = a mod]ate fee4 ,?is is effect$ by means ( fix$ collimators1 art4 #bbi4 ,= angles di/ribut$ ov] ! arc ! p>allax error is elim9at$ by plac+ ! collimators 9 pairs4 ,! ,n4,p4,l4 c]tificate may n[ be _h ) good in/rum5ts :5 pur*as$4 ,x may be not$ t an orig9ally well-made in/rum5t reta9s its qualities = all "t1 ! we> ( su* in/rum5ts be+ inappreciable4 #feb4--,to ,use ! ,sextant ! "r foot %\ld be plac$ ne>ly #b feet 9 advance ( ! left & direct$ at "r angles to x4 ,9 ?is position ! body is firm4 ,! in/rum5t is support$ by ! "r h&1 ! elb[ be+ br\ght d[n firmly ^u ! body4 ,! clamp screw fir/ & !n ! tang5t screw are mov$ by ! ?umb & f+] ( ! left h&4 ,"s practice is requir$ to make a /eady obs]vation4 ,to br+ two objects into app>5t juxtaposition1 me?ods ( obs]vation = t]re/rial objects w be reconsid]$ 9 discuss+ ! box sextant fur!r on4 ,z reg>ds cele/ial obs]vations ref]5ce %\ld be made to works on practical a/ronomy1 z ! subject w\ld take too mu* space to be ent]$ ^u "h4 ,! :ole subject1 ) _m ref9em5ts ( correction ( p>allax1 etc41 :i* fall beyond ! limits ( practical survey+ ) ! sextant1 is ably discuss$ 9 ,*auv5et's ,sph]ical & ,practical ,a/ronomy4 #fec4--;,artificial ,horizon4--,= asc]ta9+ ! latitude ( a place f ! obs]vation ( a cele/ial body by means ( a sextant1 x is necess>y to h "s means ( e/imat+ ! position ( ! horizon4 ,a me?od ( do+ ?is1 orig9ally propos$ by ! eld] ,george ,adams1 optician1 #agdh1df 0 to float a p>allel disc ( glass ^u a bas9 ( m]cury1 & to receive ! reflect$ image ( a /> f ! m]cury by ! sextant simultane\sly ) its direct image4 ,! angle !n giv5 by ! read+ ( ! arc is d\ble ! angle at :i* ! true horizon is plac$ relatively at ! same "t4 ,?is idea1 c>ri$ out 9 a practical =m 9 an in/rum5t h5ce=? call$ ! artificial horizon#dg is due to ,wm4 ,jones1 a well-kn[n optician at ! end ( ! #ah? & beg9n+ ( ! la/ c5turies1 :o arrang$ conv5i5t means ( mak+ ! in/rum5t portable1 & to keep ! m]cury f di/urbance ( ! air by cov]+ x ) a glass ro(4 ,! =m ( artificial horizon t he inv5t$ has be5 9 common use ev] s9ce4 ,he also inv5t$ ano!r simpl] =m1 :i* 0 t ( tak+ ! reflection f a piece ( silv]$1 or ( black1 glass4 ,! p]=mance ( ! artificial horizon dep5ds 9 any case entirely ^u means ( obta9+ a reflection f a p]fectly horizontal surface4 ,illu/ration3 ,fig4 #bij4--;,diagram ( artificial horizon4 #fed4--,!ory ( ! ,artificial ,horizon4--,a ray ,m ,fig4 #bij1 f a lum9\s body1 at inf9ite di/ance w h its image reflect$ f a level reflect+ surface ,,ss at an angle equal & opposite to ! incid5t ray1 ! angles ,m,,z & ,,eas be+ equal4 ,let ,e be ! place ( ! eye or ! sextant3 ?is w receive a ray f ! same di/ant body 9 direction ,,me1 :i* is s5sibly p>allel ) ,m,a4 ,! angle ,,mea be+ d\ble ! angle ( incid5ce ,m,,z1 ! half ( ?is angle w !re=e produce ! horizontal l9e ,,eh at ! height ( ! obs]v]'s eye if ! plane ( reflection ,,ss be level4 ,!re=e if we take half ?is angle ,,mea z x appe>s 9 ! sextant1 x w give an angul> position ( ! object 9 relation to ! horizon at ! height ( ! eye1 or be tang5tial to ! surface ( ! e>?4 ,if ,m,,z be #cj1 ! angle ,,aem w be #fj1 %[+ ! elevation ( object half ?is or #cj4 ,! sextant takes #abj ) c]ta9ty2 !re=e #fj w be ! limit ( m]idian altitude ! artificial horizon w measure4 ,illu/ration3 ,fig4 #bia4--;,artificial horizon ( black glass4 #fee4--;,artificial ,horizon 9 ,black ,glass4--,?is in/rum5t is ! mo/ portable1 pack+ 9 a close pocket case4 ,x is made ( bo? circul> & squ>e =m 9 plan4 ,fig4 #bia is ! ,admiralty patt]n4 ,! black glass %\ld h a truly plane surface4 ,x is fix$ ov] a brass tray by be+ float$ on pla/] ( ,p>is to avoid /ra94 ,a light rim ( brass is screw$ d[n ov] ! glass to keep x 9 position4 ,!re are ?ree adju/+ screws ,,aa,a4 ,x is adju/$ to level by a loose level tube gr\nd on its "u face ,p4 ,! level tube %[n 9 detail ,fig4 #ea1 p4 #id1 is plac$ on ! surface l9eally ) ! two screws1 ,fig4 #bia ,,aa1 & aft]w>ds at a "r angle to its fir/ position ) "o end ( ! tube t[>ds ,a4 ,x is f9ally te/$ by trav]s+ at ! position %[n 9 ! ,fig4 #bia1 & at "r angles to ?is direction4 ,!re is a great risk ( gett+ a /ra9 on ! glass 9 fix+ x 9 its frame4 ,! au?or !re=e pref]s ! circul> =m t leaves ! glass q free except at its fix+s at ?ree equidi/ant po9ts only4 ,9 ?is k9d ( artificial horizon !re is only "o surface ( glass to be work$ true2 !re=e1 !re is p]haps less risk ( error on ?is acc\nt ?an 9 o!r =ms4 ,on ! o!r h& ! m]cury pres5ts a m p]fectly level plane4 ,! circul> artificial horizons are commonly made #c in*es diamet]2 weight1 lb42 ! oblong1 ,fig4 #bia1 #d in*es by #c in*es2 weight #b lbs4 ,illu/ration3 ,fig4 #bib4--;,artificial horizon1 m]cury4 ,illu/ration3 ,fig4 #bic4--,m]cury bottle to ! same4 #fef4--;,artificial ,horizon ( ,m]cury1 ,fig4 #bib4 ,?is in/rum5t consi/s ( an oblong tray ( ab\t #f in*es by #c in*es by in* 9 dep? made ( wr\ght iron4 ,x is cov]$ by a ro( ) two slop+ sides at ab\t #de to ! plane4 ,! sides ( ! ro( are glaz$ ) work$ p>allel glass fix$ by screws at ?ree po9ts4 ,! m]cury :5 out ( use is conta9$ 9 an iron screw-/opp]$ bottle1 ,fig4 #bic4 ,x is p\r$ into ! op5 tray = use1 & ! tray is aft]w>ds cov]$ by ! ro( to prev5t curr5ts ( air di/urb+ ! level ( ! surface4 ,aft] use ! m]cury is p\r$ back into ! bottle f ! corn] ( ! tray4 ,x %\ld be p>ticul>ly obs]v$ t x is p]fectly dra9$1 z any free p>ticles 9 ! case 9 :i* all p>ts ( ! in/rum5t are pack$ w\ld be c]ta9 to attack ! ro(1 :i* is made ( brass & simply v>ni%$4 ,! in/rum5t is pack$ 9 a mahogany case1 size #g in*es by #f in*es by #e in*es2 weight1 ) #a lb4 ( m]cury1 ab\t #d lbs4 #feg4--,! ,bottle1 ,fig4 #bic1 is made ( ca/ iron4 ,x has a screw$ plug /opp] ) a lea!r coll> & a cov]+ cap ) a small hole ?r\gh its apex4 ,to p\r out ! m]cury ! cap & /opp] are unscrew$1 ! plug is tak5 away1 & ! cov] is screw$ on aga94 ,! m]cury !n issues f ! small hole 9 ! cap4 ,to return ! m]cury ! cap is rev]s$ & screw$ ^u ! bottle4 ,x !n =ms a funnel4 ,! tray has a cov]$ corn] at :i* !re is a small hole4 ,?is p]mits ! m]cury to be p\r$ into ! funnel )\t spla%+4 ,bo? plug & cap are !n screw$ d[n firmly1 & ! bottle is plac$ 9 a secure fitt+ 9 ! case4 ,illu/ration3 ,fig4 #bid4--;,capta9 ,george's artificial horizon4 #feh4--;,capta9 ,george's ,artificial ,horizon1#dh ,fig4 #bid4 ,?is is a great improvem5t on t la/ describ$4 ,! in/rum5t be+ made entirely ( iron !re is no risk ( gett+ x injur$ by escape ( ! m]cury4 ,x is also mu* m portable & conv5i5t4 ,two *amb]s ,e & ,m are connect$ toge!r by a tube ?r\gh a /em-piece 9 :i* !re is a /rong iron cock at a4 ,! *amb] ,e is cor$ out & =m a bottle into :i* ab\t #a lb4 ( m]cury is introduc$ by remov+ a screw$ /opp] at ,b4 ,! *amb] ,m is an op5 tray ) a cov] =m$ ( a piece ( p>allel glass plac$ 9 an iron rim :i* screws d[n ^u x4 ,a mill$-head$ screw at ,c =ms an air plug4 ,! cock moves v /iffly by ! lev]age giv5 by a tommy-p91 %[n a1 :i* is ins]t$ 9 ! hole at a4 ,! *amb] ,e is slightly elevat$ to cause ! m]cury to fl[ f x to ,m1 ! cock be+ turn$ on at ! same "t & ! air screw ,c releas$ a little4 ,by ! same arrangem5t1 ,m be+ rais$1 ! m]cury fl[s back into ! bottle = /orage4 #fei4--;,= ,us+ ?is ,artificial ,horizon1 :5 ! m]cury is p\r$ out 9 ! tray ,m1 x is levell$ by ! ?ree screws ,,aa,a s t x cov]s ! bottom ( ! tray & pres5ts a cle>1 level surface4 ,a sep>ate disc ( p>allel glass1 :i* fits ! tray ,m v loosely1 is provid$ ) ! in/rum5t4 ,?is floats on ! surface ( ! m]cury & keeps x q /ill1 ev5 :5 ! cov]+ glass is remov$4 ,?is arrangem5t is useful also 9 case ( an accid5t to ei!r ( ! glass cov]s4 ,! disc is kept :5 out ( use 9 a s(t lea!r bag :i* fits 9 ! tray ,m4 ,?is artificial horizon is g5]ally c>ri$ 9 a solid lea!r case ) sl+ to g ov] ! %\ld]4 ,its weight complete is ab\t #d lbs42 size1 #i in*es by #d in*es by #a in*es4 ,! surface ( m]cury is a circle ( #c in*es diamet]4 #ffj4--;,improv$ ,capta9 ,george's ,artificial ,horizon4--,mr4 ,s4 ,a4 ,ionides1 ,c4,e41 has devis$ an improv$ =m ( ! =ego+ in/rum5t %[n at ,fig4 #bie4 ,illu/ration3 ,fig4 #bie4--;,ionides's artificial horizon4 ,9 ?is ! conta9] is =m$ b5ea? ! horizon box ) a plug tap fitt$ 9 ! ?ickness ( metal betwe5 ! two2 ?is =m makes ! :ole mu* light] & less ?an half ! size ( ! usual ,capta9 ,george's patt]n4 #ffa4--;,9 ,us+ ! ,artificial ,horizon ) ! ,sextant x is g5]ally plac$ on ! gr\nd at su* a di/ance 9 front ( ! obs]v] t he c conv5i5tly see ! requir$ reflection ( ! /> or sun1 ! obs]v] mov+ ab\t until ! reflection is obta9$4 ,?is is a t$i\s process & requires "s practice4 ,x is mu* m easily effect$ if ! sextant be m\nt$ on a tripod or o!r /&4 ,:5 a /& is us$ x has g5]ally a univ]sal jo9t1 s z to be able to take surface angles also f ! fix$ position4 ,:5 ! altitude ( objects on ! e>? is tak51 ! obs]vation requires r$uction = refraction1 :i* becomes an important factor1 al?\gh ?is is v>iable ) atmosph]ic conditions2 b ^u ! :ole x always t5ds to make ! object appe> high] ?an x really is4 ,commonly "o-sev5? ( curvature is us$ z an approximate correction4 ,= sol> & /ell> refraction1 works on a/ronomy %\ld be consult$4 ,! index error ( ! sextant is correct$ be=e refraction1 :5 ! natural horizon is employ$4 ,:5 ! artificial horizon is us$ ! index error is all[$ be=e tak+ its half z a s+le measure4 ,! artificial horizon is us$ also ) ! !odolite4 ,x =ms ! mo/ p]fect means ( adju/+ ! transv]se axis by tak+ an obs]vation ( ! pole /> ) ! telescope1 fir/ directly & !n by its reflection f ! artificial horizon4 ,if ! images cut ! c5tre ( ! webs 9 ! two positions by ! movem5t ( ! transv]se axis only f ! "o to ! o!r1 ?is axis is prov$ p]fectly level4 #ffb4--,v>i\s s*emes = obta9+ ! horizon by "s sy/em ( levell+ app>atus atta*$ to ! sextant h be5 devis$1 none ( :i* are v practical1 z !y all dep5d ^u a p5dulum or a gravitation surface ( a liquid or a gyroscope1 & are all un/able z h& in/rum5ts4 ,!re h be5 num]\s pat5ts tak5 out ) ?is object f t ( ,w9t] 7#agfj7 d[nw>ds1 :i* anyone int]e/$ 9 ! subject may consult4#di ,! matt] is m5tion$ "h z ! recurr5ce ( ! idea appe>s to be frequ5t4 ,illu/ration3 ,fig4 #bif4--,s\nd+ sextant4 #ffc4--,! ,s\nd+ ,sextant4--,?is in/rum5t is us$ = coa/ surveys4 ,angles are tak5 ) x ( objects1 buoys1 etc41 f ! l& & also f a boat on ! wat] = su* objects or = o!rs ^u l&4 ,x is con/ruct$ ^u ! same pr9ciple z ! ord9>y nautical sextant2 b z x is to be us$ z an all-day work+ in/rum5t1 & n = a few diurnal obs]vations only1 x is made mu* m solid1 & its optical p>ts take a m ext5d$ field ( view4 ,! graduation is also /rong]1 su* precision ( read+ only be+ requir$ z may aft]w>ds be plott$ on a *>t4 ,?is in/rum5t is %[n 9 p]spective1 ,fig4 #bif4 ,! index glass is l>ge--ab\t #b in*es by #a in*es4 ,?is is secur$ on all sides by a firm rim to ! tray 9 :i* ! glass is held at ?ree po9ts4 ,! adju/m5t ( ! index glass is left "u control1 z x may occasionally be necess>y to remove x f effects ( spray ^u & ab\t x4 ,! horizon glass is made ab\t #a in*es 9 wid? & in* 9 dep?4 ,?is is entirely enclos$ 9 a tray1 ! :ole surface be+ a mirror )\t any plane "p to ! glass z ) ! ord9>y sextant1 s t x is entirely protect$ by ! metal4 ,by ?is arrangem5t ! eye receives ! direct ray f ! object imm$iately be=e x1 & ! reflect$ ray f an object ^: angul> position is desir$ to be tak5 ) x3 b ^! images d n come exactly into contact1 z ! n>r[ frame int]poses4 ,x is1 h[ev]1 suffici5tly ne> = t]re/rial obs]vations4 ,! adju/m5t ( ! horizon glass to ! p]p5dicul> ( ! plane ( ! arc is ! same z t %[n 9 detail = ! box sextant fur!r on4 ,! adju/m5t ( ! horizon glass to ! index is by a /iff arm ext5d$ f ! sole-plate project$ into a loose op5+1 :]e x is held firmly by two oppos+ cap/an-head$ screws1 z be=e describ$4 ,! arc ( ! sextant is ( #f in*es radius1 graduat$ ^u silv] to #bj1 & read+ by ! v]ni] to s+le m9utes only by ! microscope4 ,! clamp & tang5t are ! same z ^? describ$ = ! nautical sextant4 ,! frame is /raight brac$4 ,! telescope has a wide field1 ) a*romatic object-glass ( #d in*es focus1 ! cle> ap]ture be+ #a-a_/h in*es4 ,! support+ r+ ( ! telescope has no ris+ /em or collimat+ adju/m5t1 b is solidly fix$ 9 its true position by ! mak]4 ,! r+ c>ries a pla9 disc p9-hole sight1 :i* takes ! place ( ! telescope = ne> obs]vations4 ,! in/rum5t 9 use is held 9 ! h& by a firm oblong h&le4 ,! in/rum5t re/s1 if requir$ = read+1 ^u ?ree legs z ! ord9>y sextant4 ,its weight is ab\t #b lbs41 or :5 pack$ 9 its case1 #e lbs4 ,its exam9ation & adju/m5t are ( ! same k9d z ^? j describ$ = ! nautical sextant4 #ffd4--;,box ,sextant4--,?is v neat & portable in/rum5t 0 inv5t$ by ! late ,william ,jones4#ej ,x is us$ = tak+ angles )9 #abj ^u ! surface ( ! l& to )9 a s+le m9ute ( arc4 ,x has become des]v$ly popul> ) ,briti% surveyors z a l& survey+ in/rum5t1 & is equally s z a milit>y "o4 ,x is ! same 9 pr9ciple z ! nautical sextant already describ$1 b x possesses ! great m]it--z a survey+ in/rum5t con/antly 9 h&--t all its glasses & delicate p>ts are securely protect$ f accid5tal injury by be+ cov]$2 :]eas ! nautical sextant1 made = "o or two diurnal obs]vations only1 has all ^! p>ts expos$4 ,& x is n only t all p>ts are protect$ :5 ! in/rum5t is 9 use1 b !y are all d\bly protect$ by ! cov]+ box :5 c>ri$ ab\t out ( use2 s t x is f\nd t a well-made box sextant set orig9ally 9 p]fect adju/m5t w reta9 ?is adju/m5t 9 av]age use = v _m ye>s4 ,! au?or has se5 an in/rum5t tw5ty ye>s 9 use /ill 9 p]fect adju/m5t4 ,! box :i* cov]s ! in/rum5t out ( use =ms also a mo/ conv5i5t h&le or support = x :5 9 use by atta*+ x 9 a rev]s$ position und]nea?1 z x appe>s 9 ,fig4 #big4 ,?is atta*m5t is made ei!r by a screw cut entirely r\nd ! body ( ! in/rum5t1 or1 :at is mu* bett]1 by a bayonet fitt+1 = ! reason t l>ge screws ( ?is description are liable to cross ?read4 ,! g5]al description ( ! out] p>ts is z foll[s3-- ,illu/ration3 ,fig4 #big4--,p]spective view ( ! box sextant ready = use4 #ffe4--;,c a cov]+ box :i* inv]ts f ! position %[n 9 ! figure & cov]s ! in/rum5t4 ,?is has a diamet] ( #c in*es & a dep? ( #a in*es4 ,b box conta9+ ! optical & mov+ p>ts ( ! sextant4 ,a axis ( index glass4 ,?is axis also c>ries a too!d segm5t fix$ close "u ! front ( ! box1 by :i* bo? ! index glass & index are mov$ by means ( a p9ion to be describ$4 ,! index c>ries a v]ni] divid$ into #cj1 :i* reads into ! arc to s+le m9utes2 ! arc is divid$ to half degrees on silv]4 ,! magnifi] is c5tr$ by a swivel h+e jo9t ov] ! axis1 s z to p]mit x to be br\ght to focus ^u ! arc at any position4 ,?is magnifi] is held d[n on ! front ( ! box :5 out ( use by a nib cat* at a position ( ab\t #hj ( ! arc4 ,o a mill$ head1 ! axis ( :i* c>ries a p9ion :i* works into ! segm5t above describ$ "u ! index glass4 ,! p9ion is ab\t #a to #i ( ! segm5t1 s t ! index trav]ses ! arc ( #fj 7read+ #abj7 by "o-&-a-half turns4 ,?is gives a conv5i5tly sl[ motion to ! index glass1 & enables ?is sextant1 if x be well made1 to be set rapidly ) great precision4 ,s two nibs1 "p ( two lev]s = putt+ ! %ades 9 or out ( action4 #fff4--;,9 ! clos$ =m ( sextant ! %ades block ! reflect+ position betwe5 ! index & ! horizon glass4 ,= surface survey+ !y h !re=e to be op5$ out1 ?r\gh an op5+ clos$ by a slide %utt] :i* moves by a /ud 9 a slot on ! "u side4 ,! %ades consi/ ( "o gre5 & "o d5se r$ glass :i* mu/ be work$ p>allel1 z be=e describ$ = ! nautical sextant4 ,^! are us$ = tak+ altitudes ( ! sun1 = adju/m5ts only4 #ffg4--,! ,key ,k is a mill$ head :i* screws out1 & c>ries a wat*-key pipe at ! end ( its /em by :i* adju/m5ts may be made f ?ree squ>e-head$ screws fitt+ its pipe1 two ( :i* are close to b1 ! axis ( ! horizon glass4 ,^! adju/ p]p5dicul>ly to ! plane ( ! arc4 ,"o screw at a adju/s ! p>allelism ( ! index & horizon glasses :5 ! index is at z]o4 #ffh4--,! ,telescope is a*romatic1 ) draw tube = focuss+4 ,x magnifies ab\t #b diamet]s4 ,x has a concave eye-glass1 & !re=e gives an erect image1 ,fig4 #ad4 ,a sun-glass ,e screws ov] ! eye-glass :5 x is requir$ = sun obs]vations4 ,! telescope is atta*$ to ! sextant by means ( a crank-piece ^u ! telescope :i* is fix$ by ! mill-head$ screw ,t & two /eady p9s4 ,! crank-piece screws 9 rev]se position ^u ! telescope = portability be=e putt+ x by 9 its case4 #ffi4--;,by "s mak]s ! telescope is made to slide into ! body ( ! sextant & ?us become q portable4 ,?is plan is a v neat "o1 b x requires c>e to see t ! %ades d n int]f]e be=e x is put by4 ,! weight ( ! entire sextant ) its solid lea!r case is ab\t #ah oz4 only4 ,= close "w ! telescope is n g5]ally us$4 ,a slid+ %utt] pi]c$ ) a small hole cov]s ! telescope op5+ into ! sextant1 :i* is us$ z a sight hole4 ,illu/ration3 ,fig4 #bih4--;,box sextant "u ! face4 #fgj4--,! ,int]ior or ,optical & ,me*anical "p ( ! ,sextant is %[n ,fig4 #bih4 ,i index glass1 fix$ ov] ! too!d segm5t on ! same axis4 ,! p9ion is %[n work+ into ! segm5t mov$ by ! mill$ head ,o ( ,fig4 #big on ! face ( ! sextant4 ,fig4 #bih3 horizon glass1 cut by ,,ed1 adju/s to ! v]tical by screws ,,cc1 :i* h squ>e fitt+s on ! face ( ! in/rum5t1 %[n ,figs4 #bii & #cjj full size4 ,! diff]5tial adju/m5t betwe5 horizon & index glasses is made by a screw ) a squ>e fitt+ at ,p4 ,?is adju/m5t acts by screw+ aga9/ a helical spr+1 %[n at ,q4 ,! reflect$ rays ent] by a wide w9d[ 9 ! side ( ! box1 ,fig4 #bih d1 ! direct rays by a small w9d[ f4 ,! pa? ( a ray is %[n by f9e l9es f ,r to ,e1 = ! positions 9 :i* ! index & horizon glasses are plac$4 ,! p9-hole opposite :i* ! eye is plac$ is %[n :ite4 ,s %ades ) _! axis are %[n cut (f1 to prev5t confusion ( o!r p>ts4 ,!y are simply r\nd discs ( p>allel glass on arms :i* rise f ! back ( ! face by pressure ( ! nibs at ,s4 ,illu/ration3 ,fig4 #bii4--,plan ( horizon glass4 ,illu/ration3 ,fig4 #cjj4--,section ( ! same4 #fga4--,! ,con/ruction ( ! ,box ,sextant may be fairly inf]r$ f inspection ( ! engrav+s4 ,! face-plate is made ( a cas+ 9 brass #a_/h in* ?ick1 :i* %\ld be well hamm]$ to h>d5 & /iff5 x4 ,! axis1 :i* has a wide coll>1 is fitt$ into a hole 9 ! plate1 fir/ by turn+ x z exactly z possible1 & !n by burni%+ x 9 by friction1 ! hole be+ broa*$ slightly conical ) a ,d-broa*4 ,! c>eful fitt+ ( ! axis is an important "p4 ,! horizon glass frame1 ,fig4 #cjj1 is held d[n by a c5tral screw :i* fits tightly bo? 9 its =e hole & ?read4 ,! flange ( ! tray ,f is cut to an angle on its "u side to p]mit adju/+ to v]ticality by rock+ ov] ?is angle1 by tight5+ & loos5+ ! adju/+ screws cc :i* protrude 9 squ>e heads to ! face ( ! in/rum5t4 ,! horizon glass1 ,h1 :i* is half silv]$1 is fix$ 9 a tray-piece :i* has two n>r[ fillets turn$ to ! face ( ! glass1 & a spr+-piece at ! back br\ght up by a screw a4 ,?is glass is entirely op5 at its unsilv]$ "p4 ,! too!d segm5t %\ld be cut ^u its own axis1 & al?\gh fitt$ to ! p9ion )\t any loos5ess1 x %\ld n press ! index axis4 ,! silv] is inlaid 9 ! arc on ! plan %[n ,fig4 #abg4 ,! v]ni] is sold]$ closely on ! index & %\ld read d[n to a f9e clean edge4 #fgb4--;,exam9ation ( ! ,box ,sextant4--,! glasses %\ld be cleanly silv]$1 ) a %>p1 cle> cut betwe5 ! silv] & ! cle> glass ( ! horizon glass4 ,! p9ion %\ld move s(tly & equally 9 caus+ ! index arm to trav]se ! arc4 ,if ! p9ion be mov$ 9 little j]ks backw>ds & =w>ds !re %\ld be no %ake1 b ! index %\ld foll[ e slight motion4 ,! magnifi] ris+ jo9t %\ld move r /iff] ?an ! trav]s+ jo9t1 s t ! focus is n *ang$ by trav]s+ across ! arc4 ,! magnifi] %\ld h ab\t #a in* or less focus1 & %\ld /& squ>e to ! plane ( ! sextant :5 9 focus4 ,! graduation %\ld be deep & f9e1 & ! v]ni] %\ld read #cj #bi at ! two ends & ! c5tre ( ! arc4 ,if !re be a small excess or defect ( v]ni] to arc1 ?is %\ld be not$ & all[$ =1 ei!r at ! "t ( read+ or z an index error4 ,! slid+ fitt+s ( ! p9-hole sight1 %ades1 & "u %utt] %\ld move firmly b n /iffly4 ,! telescope %\ld fit )\t %ake4 ,! cov]+ box %\ld fit well 9 bo? positions ( cov] or h&-hold4 #fgc4--;,adju/m5t4--,! box sextant is be/ adju/$ by ! sun ^u ! plan describ$ art4 #fdh4 ,! adju/+ screws1 z already /at$1 are mov$ by ! key1 :i* unscrews f ! face ( ! sextant1 ,fig4 #big ,k4 ,! adju/m5t is made p]man5tly by ! mak]1 except only t ( ! horizon glass1 :i* is at ! comm& ( ! us]4 ,! adju/m5t to p]p5dicul>ity ( face is made by ! two screws ^u ! face ne> b2 adju/m5t to z]o ( arc by ! screw at ! side a4 ,9 defect ( appe>ance ( ! sun1 ! sextant may be adju/$ to any cle>1 %>p l9e1 z t ( a /ret*$ piece ( tw9e1 = p]p5dicul>ity ( plane1 & to any object ( cle> outl9e suffici5tly di/ant1 say at half a mile1 to avoid error ( p>allax = index z]o1 art4 #fba4 #fgd4--,use ( ! ,box ,sextant4--,! sextant has its "u %utt] op5$ by press+ ! /ud atta*$ ov] 9 its slot4 ,! nibs ( ! %ade lev]s1 ,fig4 #big ,s1 are !n rais$ & ! %ades depress$4 ,! cov] is !n screw$1 or slid on if x fixes ) bayonet not*es1 ^u ! "u side ( ! sextant to =m ! h&-hold4 ,! p9-hole sight is press$ ov] = use if n already 9 its position1 unless x be int5d$ to use ! telescope4 ,! box sextant is held 9 ! left h&1 ) ! "r-h& ?umb & =ef+] con/antly hold+ ! mill$ head1 & turn+ ?is s z to br+ ! two objects1 ( :i* x is desir$ to obta9 ! angul> position1 f ! obs]v]1 exactly 9 app>5t juxtaposition1 ! "o ov] ! o!r4 ,9 turn+ ! mill$ head x is bett] to let all ! o!r f+]s ( ! "r h& clut* & /eady ! in/rum5t4 ,to take angles objects %\ld be obs]v$ t cut %>p1 erect outl9es1 z build+s1 po/s1 trees1 etc41 if possible4 ,9 op5 c\ntry x is necess>y to use pickets1 to be describ$ fur!r on4 ,) pickets ! reflect$ image ( ! upp] half ( "o picket %\ld =m a cont9u\s outl9e ) ! direct image ( ! l[] half ( ! o!r picket 9 ! eye1 s t ! pair ( pickets appe> z "o4 ,:]e an angle great] ?an #abj is requir$ an int]m$iate picket is set up1 & angles tak5 to ! "r & left ( ?is are add$ toge!r4 #fge4--;,x mu/ always be rememb]$ t ! sextant takes angul> positions actually1 :]eas plans are made 9 azimu?al angles4 ,!re are "s n v satisfactory means ( approximate correction = ?is1 = :i* books on survey+ may be consult$2 b altoge!r ! sextant is n v useful = tak+ angles = plans on o!r ?an fairly level gr\nd1 :]e9 x has prov$ a mo/ valuable & suffici5tly exact in/rum5t4 ,:]e gr\nd is undulatory fairly good "w may be done ) x by tak+ /ations = ext]ior triangles at equal heights on ! hillsides1 z asc]ta9$ by a h& level or cl9omet] to be describ$1 or sometimes f hilltop to hilltop :]e ^! are ( fairly equal heights4 ,= sket* plans ( v hilly or m\nta9\s di/ricts ! prismatic compass1 art4 #adh1 is bett]1 z ?is gives1 al?\gh ) less precision ?an ! sextant1 its angles 9 azimu?4 ,illu/ration3 ,fig4 #cja4--;,int]ior con/ruction ( box sextant ) supplem5t>y arc4 #fgf4--;,box ,sextant ) ,supplem5t>y ,arc4--,?is sextant is pref]r$ by _m because ( its m ext5d$ use4 ,x is complete z an ord9>y sextant = angles up to #abj2 b if x be ?\ght desirable to ext5d ! angles to #bbj--;by a s+le obs]vation ?is may be done4 ,! ord9>y arrangem5t ( ! box sextant j describ$ is left intact & =ms ! upp] "p ( ! in/rum5t4 ,?is arrangem5t1 z 9 ! box sextant1 is atta*$ entirely to ! face or arc plate1 ! only diff]5ce be+ t ! index glass is made ( less dep?4 ,= ! supplem5t>y arc arrangem5t a mirror is fix$ ^u ! l[] or sole plate exactly "u ! position ( ! index glass4 ,?is mirror is t]m$ ! supplem5t>y index glass4 ,! position ( ! face ( ! index glass is at "r angles to ! face ( ! ord9>y index glass :5 ! index is at z]o4 ,! arrangem5t ( glasses is %[n ,fig4 #cja3 ,,mm index glasses4 ,! supplem5t>y angle is read ?r\gh a sep>ate p9-hole sight :i* is plac$ at ab\t #ij f ! p9-hole sight ( ! prop] sextant & a little l[] d[n on ! rim4 ,! arc ( ?is sextant reads 9 ! ord9>y mann]1 left to "r1 to an inn] circle ( figures = angles f #j to #acj4 ,! supplem5t>y arc reads by ! same v]ni]1 & is figur$ 9 ! same mann] at ! t5s2 b x reads into an out] circle ( figures :i* progress 9 ! rev]se direction1 t is1 "r to left4 ,! read+s ( ! supplem5t>y arc are f #ij to #bbj1 s t = a c]ta9 range1 t is1 = angles f #ij to #acj1 ^! may be tak5 ei!r by direct arc or by supplem5t>y arc4 ,! supplem5t>y angle is tak5 by means ( ! co9cid5t images ( two reflections1 "o f ! index glass & "o f ! supplem5t>y index glass1 & n by "o direct & "o reflect$ image z 9 ! sextant prop]4 ,illu/ration3 ,figs4 #cjb1 #cjc4--;,diagram ( supplem5t>y arc sextant4 #fgg4--,!ory ( ,supplem5t>y ,angles to ! ,sextant4--,= ! measurem5t ( ^! angles we h to consid] direct reflections only ( two reflect+ planes plac$ "o above ! o!r ne>ly 9 contact1 s t ! images project$ f bo? planes may rea* ! eye sup]impos$4 ,let ,fig4 #cjb ,,ii be ! surface ( a mirror 7index glass7 :i* is movable to any angle 9 relation to ! face ( ! mirror ,,ss 7supplem5t>y index74 ,= demon/ration ( ! pr9ciple ^! mirrors are %[n 9 ?is diagram at #ij to ea* o!r2 !re=e co9cid5t reflections w be at #ij #ij #ahj4 ,let ! l9es ,,fc & ,,bc =m a "r l9e 7#ahj72 ,f =e sight & ,b back sight4 ,an object at ,f w\ld be reflect$ f ! mirror ,,ii to ! eye at ,e1 ! angles ,,fci & ,,eci be+ equal4 ,ano!r object at ,b reflect$ f ! face ( ! mirror ,,ss w\ld also rea* ! eye at ,e1 ! angles ,,bcs & ,,ecs be+ equal4 ,& z ! angles ,,fci & ,,bci are equal 9 cross+ a "r l9e1 ! l9e ,,fcb mu/ be also a "r l9e 7#ahj7 :i* is indicat$ by ! angle ( co9cid5ce ( ! two reflections to ,e4 ,! positions ( ! reflections are %[n z angul> measurem5ts ^u ! graduat$ arc4 #fgh4--;,9 ,fig4 #cjc let ,,ss rema9 z be=e1 angle ,,bce w rema9 z %[n 9 bo? figures4 ,move ! index glass f ! position ,,ii ( ,fig4 #cjb to ! position ,,jj ( ,fig4 #cjc1 s t aft] ?is movem5t ! eye at ,e w\ld receive ! image ( an object at a new position ,f z reflect$ f ! mirror ,,jj1 ,f,,cj & ,,ecj be+ equal4 ,9 ?is process1 z ! reflector ,,jj 9 ! angle ,,icj w\ld h mov$ half ! angle ,,jcf1 ! record ( ?is movem5t ^u ! index1 :i* moves ) ,,jj1 is at ! same "t d\ble ! true angul> diff]5ce1 z ) ! sextant prop] fully describ$1 ! graduations be+ 9 bo? cases ! same pro rat4 ,! increase ( angle is tak5 supplem5t>y to ! angle giv5 by ! fir/ reflection1 by addition to ?is angle 9 a direction "r to left f ! "r l9e ( ! =m] sight ,,ec2 consequ5tly ?is increase is read backw>d on ! sextant1 t is1 "r to left1 & is indicat$ by ! out] l9e ( num]als4 #fgi4--,manufacture4--,! g5]al /ructure ( ?is in/rum5t is ne>ly ! same z ! ord9>y box sextant1 except ! p>ts j ref]r$ to4 ,! supplem5t>y index glass is an ord9>y mirror simil> to ! index glass b ( only in* 9 dep?3 x is m\nt$ 9 ! same way4 ,its adju/m5ts are simil> to ! horizon glass 9 k9d1 b !re are no ext]ior screws1 ?is glass be+ p]man5tly fix$ by ! mak]4 ,opposite ! supplem5t>y index glass a wide w9d[ is cut ?r\gh ! rim ( ! case ne> ! sole plate to take sight ( ! object at angles exce$+ #abj1 s t 9 ?is sextant two l>ge w9d[s are cut out opposite to ea* o!r4 ,! diamet] ( ?is sextant is #c in*es2 ! ext]ior dep? ab\t #a-e_/h in*es1 t is1 #a_/h in* deep] ?an ! ord9>y box sextant4 ,x weighs ab\t #bj oz4 ,x is c>ri$ 9 a solid lea!r case ) /rap to pass ov] ! %\ld]4 #fhj4--;,exam9ation & ,adju/m5t4--,exam9ation w be ne>ly ! same z = ! common box sextant4 ,! mo/ important po9t is t ! read+s tak5 )9 bo? arcs %\ld be alike1 assum+1 :i* is necess>y1 t ! "p compris+ ! sextant prop] is p]fectly adju/$4 ,?us !re is a #ij on bo? direct & rev]se arcs4 ,! #ij may be measur$ by any pair ( objects on ! direct arc1 & aft]w>ds comp>$ by %ift+ ! index to ! #ij1 on ! supplem5t>y arc4 ,if no object be f\nd at #ij1 !n #ie #cj or any o!r quantity may be comp>$4 ,x is also well to comp>e read+s at or ab\t #abj on bo? arcs4 ,! #ij & #abj fall 9 ! same position 9 ! read+1 & ?is *ecks any error 9 ei!r4 ,if ! adju/m5t be n fairly p]fect1 ! in/rum5t %\ld be return$ to ! mak]4 ,inde$1 ?is sextant w\ld be bett] )\t any ext]nal means ( adju/m5t1 leav+ ^! to be made by ! optician 9 su* a p]man5t =m t !y w n be liable to *ange4 ,x is1 z ! pla9 box sextant1 exceptionally protect$ f accid5t4 #fha4--;,9 us+ ?is in/rum5t ! arc up to #abj is tak5 exactly z ) ! pla9 box sextant4 ,beyond #abj ! sextant is %ift$ to take sight ?r\gh ! supplem5t>y p9-hole1 be+ p>ticul> to obs]ve t ! p9ion is n[ turn$ ! rev]se way to increase ! angle1 & t ! v]ni] reads = ! supplem5t>y arc "r to left4 ,x is 9 ?is rev]s+1 if n c>efully p]=m$1 t a little difficulty is exp]i5c$ 9 us+ ?is in/rum5t4 #fhb4--;,box ,sextant1 ) ,cont9u\s ,arc to #bdj4--,?is in/rum5t is an improvem5t by ! au?or ^u "o orig9ally design$ by ,mr4 ,w4 ,frankl94 ,! read+ is tak5 cont9u\sly f ! same sight-hole & by ! same arc1 & 9 a direct mann] )\t any rev]sal = "p ( ! arc4 ,?is sextant reads ) c]ta9ty to #bdj4 #fhc4--;,9 ! con/ruction ( ?is sextant !re are two horizon glasses sup]impos$ "o above ! o!r & cross+ ea* o!r1 ) faces :i* are adju/able = p]p5dicul>ity at an angle ( #abj4 ,! horizon glass is divid$ top f bottom by a cle> b& cut ?r\gh x1 z 9 ! old =m ( back-sight nautical sextants4 ,"o ( ! wide glasses reflects into ! upp]1 & ! o!r into ! l[] mirror ( ! horizon glass4 ,! p9-hole sight or ! telescope is plac$ 9 ! same position z 9 ! pla9 box sextant describ$4 ,! horizon glass is fix$ & bo? ! index mirrors adju/ to angul> positions1 or "o index glass only & ! horizon glass is adju/$1 ?is arrangem5t be+ optional4 ,! arc is graduat$ z ! pla9 box sextant1 b x reads ) two r[s ( figures f #j to #abj1 & f #abj to #bdj1 ! #j ( ! "u l9e be+ "u #abj ( ! upp]4 ,:5 ! arc is set to z]o ! index glasses are 9 su* a position t ! direct vision & ! reflection z se5 9 ! upp] mirror ( ! horizon glass are co9cid5t = direct images1 z at ! z]o ( ! pla9 sextant1 b at ?is po9t ! l[] mirror ( ! horizon glass reflects to ! eye an object at #abj4 ,:5 ! index is mov$ =w>d ! angles cont9ue onw>d1 reflect$ f bo? glasses1 s t ! upp] reads on #aj1 #bj1 #cj1 etc41 :]eas ! l[] read #acj1 #adj1 #aej1 etc42 s t if ! objects desir$ to be triangulat$ are "u #abj ! co9cid5ce is se5 9 ! upp] mirror1 & if ov] ?is 9 ! l[]1 ! great di/ance ( #abj ap>t ( ! angles prev5t+ ! risk ( accid5tally tak+ ! "o = ! o!r4 ,9 ! compact =m ( a box sextant ?is in/rum5t embraces ! uses ( ! ord9>y reflect+ circle ( d\ble ! diamet]1 due to ! entire circle graduation2 & ! range is suffici5t1 z beyond #bdj ! head mat]ially int]f]es ) obs]vation4 ,! size & weight ( ! in/rum5t are g5]ally b little ov] t ( ! pla9 box sextant4 ,! adju/m5ts are made p]man5tly by ! mak]4 ,! use ( ?is in/rum5t is fully inf]r$ f ! description giv54 ,! con/ruction is %[n 9 ,fig4 #cjd1 ,e place ( ! eye ) direct ray ?r\gh ! horizon glass ,h to ,o4 ,! index glass ,i is t ( ! ord9>y sextant1 %[n by dott$ l9es1 ?r[+ ! image ( an object at ,p to ! upp] horizon glass & !nce to ! eye at ,e4 ,b is ! fix$ supplem5t>y glass ) its surface at #fj to ! l[] horizon glass at ,a4 ,! sight l9es f an object at ,q are reflect$ f ,b to ,a & !nce to ,e4 ,a spr+ arrangem5t %[n ,,ss ) a mill$ head und]nea? p]mits ! l[] glass ,a to be drawn d[n to conv]t ! in/rum5t into a simple box sextant4 ,illu/ration3 ,fig4 #cjd4--,/anley's cont9u\s arc box sextant4 ,illu/ration3 ,fig4 #cje4--,section ( supplem5t>y horizon arrangem5t4 #fhd4--;,details ( ,spr+ ,arrangem5t to ! supplem5t>y horizon glass are %[n 9 ,fig4 #cje full size 9 section4 ,! spr+s ,,ss 9 ,fig4 #cjd & ,s ,fig4 #cje =m two po9ts ( support to ! horizon glass1 ! silv]$ face ( :i* is %[n at ,a4 ,a ?ird po9t ( contact is ne> ,d1 plac$ 9 ! c5tre ( ! end ( ! support+ plate = ! horizon glass4 ,:5 ! screw ,r1 :i* is plac$ 9 a loose fitt+1 is releas$1 ! spr+s br+ ! support+ plate tight up to ,d & hold ! horizon glass firmly 9 an elevat$ position4 ,:5 ! screw ,r is tight5$ x br+s ?is glass d[n4 ,! horizon glass is adju/$ ov] a rock+ c5tre by ! screws ,,cc4 ,a screw & coll> b prev5t ! loss ( ! screw ,r4 ,by ?is arrangem5t ! horizon glass is br\ght 9 or out ( ! field ( view1 9 ord] to use ! supplem5t>y arc or = leav+ x z a pla9 sextant4 ,illu/ration3 ,fig4 #cjf4--,/anley's portable survey+ sextant4 #fhe4--,op5 ,survey+ ,sextants1 simil> to nautical sextants b g5]ally small] & ( /rong] con/ruction1 prec$$ ! box sextant1 & are /ill us$ to a limit$ ext5t ^u ! ,cont95t1 p>ticul>ly ) "s =m ( supplem5t>y arc1 or arrangem5t to produce a l>ge "p ( ! reflect+ circle4 ,^! =ms are also occasionally reviv$ by ! opticians ( our own c\ntry4 ,! reason ( ?is is easily se54 ,to ! optician :o lives 9 a t[n1 moves on a level surface1 & has com=tably w>m h&s1 ev5 9 ! w9t]1 to hold & move ! sep>ate p>ts ( an in/rum5t1 ! op5 sextant appe>s ! mo/ p]fect1 z he c get at e "p ( x easily to clean & adju/4 ,! surveyor takes ano!r view ( ! subject4 ,he is expos$ 9 ! op5 c\ntry to all wea!rs & all difficulties ( movem5t ov] ! l&2 !re=e t =m ( in/rum5t :i* is be/ protect$ & lea/ liable to injury by a fall w be sure to be popul> ) him4 ,x is ^u ^! conditions ! box sextant ( "s =m is g5]ally pref]r$4 ,a h&y =m ( portable survey+ sextant has be5 devis$ by ! au?or & is %[n at ,fig4 #cjf4 ,! arc is ( #d in*es radius & is divid$ on silv] to read #bj1 is complete ) %ades & telescope & packs into a case #g #f #b in*es4 ,illu/ration3 ,fig4 #cjg4--,optical squ>e4 ,illu/ration3 ,fig4 #cjh4--;,d\ble optical squ>e4 #fhf4--,optical ,squ>e4--,?is extremely h&y little in/rum5t is invaluable = tak+ (fsets 9 *a9+ = any irregul>ity or obliquity to ! "r l9e 9 ! b\nd>ies ( fields1 h$g][s1 f5ces1 /reams1 etc41 giv+ z x does in/antly at sight a "r angle to any object t may be sight$ on ei!r h&4 ,! in/rum5t is optically con/ruct$ exactly z a box sextant2 b ! glasses are fix$ ) _! faces p]man5tly at ! angle ( #de to ea* o!r1 by :i* means ! reflection ( #ij is truly giv5 on pr9ciples fully discuss$ at ! comm5cem5t ( ?is *apt]4 ,?is in/rum5t be+ made v small1 t is1 #b in*es or less 9 diamet]1 x is f\nd mo/ conv5i5t = manipulation to place ! adju/m5ts to ! l>g] glass1 t is1 ! index glass4 ,! horizon glass1 ,fig4 #cjg1 h is !re=e fix$ firmly1 l ! index glass ( ! box sextant1 by two screws to ! sole plate4 ,! index glass i is held & adju/$ 9 exactly ! same mann] z ! horizon glass ( ! box sextant1 z %[n 9 detail1 ,figs4 #bii1 #cjj1 ! only diff]5ce be+ t ! frame :i* holds ! glass is made ( ! entire height4 ,! rim ( ! case ( ! optical squ>e is =m$ ( a %ort l5g?1 #c_/h in* to #e_/h in*1 ( a pair ( telescope tubes :i* slide easily toge!r4 ,"o ( ^! is atta*$ to ! sole plate & ! o!r to ! cov]1 s t at fir/ !y close toge!r z a box & lid4 ,all ! op5+s requir$ = sight1 z ,fig4 #cjg at ,q = horizon sight1 o = index sight1 & e = p9-hole or eye sight1 are cut ?r\gh ! two tubes4 ,illu/ration3 ,fig4 #cji4--,optical squ>e4 #fhg4--,! inn] case is cut 9 ! plane ( "s "p ( ! circumf]5ce ( ! in/rum5t f a p9-hole into a bayonet not*1 made ) a horizontal slot = ! two cases to revolve ^u ea* o!r ^u a p91 suffici5tly to close & op5 ! sight holes4 ,?is plan secures ! in/rum5t f any intrusion ( du/ :5 x is clos$ & out ( use4 ,an adju/+ key is plac$ 9 ! case1 held by a tube or /ud at ! position k4 ,! weight ( ! entire in/rum5t is ab\t #d oz4 if ( ord9>y make2 b small] ones are made 9 ,g]man-silv] or silv]1 #a in*es diamet]1 #c_/h in* ?ick1 weigh+ "u #b oz4 ,^! latt] are v conv5i5t = ! wai/coat pocket1 & are equally z exact z ! l>g] in/rum5ts4 ,fig4 #cji %[s ! g5]al outw>d appe>ance ( ! optical squ>e4 #fhh4--;,exam9ation & ,adju/m5t ( ! ,optical ,squ>e4--,place two pickets 9 an op5 space at a di/ance ap>t1 ! fur!r ! bett]4 ,range an int]m$iate %ort picket 9 "r l9e ) ^! or ! top ( a /ake ! height ( ! eye1 or :at is bett] /ill1 if at h&1 ! top ( a tripod /&4 ,place ! optical squ>e ov] ! int]m$iate /ation or tripod4 ,place ano!r picket1 :i* we w di/+ui% z ! #ij picket1 at a di/ance1 & make ?is appe> 9 ! optical squ>e co9cid5t by reflection ) ! direct sight ( "o ( ! pickets 9 ! "r l9e f our /ation4 ,turn ! optical squ>e "r ov] on its place1 & look+ 9 ! opposite direction take a sight at ! o!r "r l9e picket & obs]ve ! #ij picket4 ,if ?is /ill appe>s co9cid5t ) ! direct l9e 9 reflection ! optical squ>e is 9 p]fect adju/m5t4 ,if x does n appe> s1 half ! diff]5ce mu/ be adju/$ by means ( ! key tak5 f ! int]ior ( ! case & plac$ on ! squ>e at k1 ,fig4 #cjg1 & ?is obs]vation repeat$ until ! #ij is correct4 #fhi4--;,9 ,us+ ! ,optical ,squ>e x is cu/om>y to walk along ! *a9 l9e at ab\t ! desir$ position = tak+ an (fset1 look+ by direct vision ?r\gh ! pla9 "p ( ! horizon glass h at a =e sight object until ! requir$ object is sight$ by reflection at "r angles to ?is1 :]e x appe>s by co9cid5ce ( image ) ! =e sight4 ,! heel ( ! =w>d foot 9 /epp+ indicates fairly ! v]tical position ( ! optical squ>e2 b "s surveyors pref] ! use ( a drop arr[ to fix ! po9t4 ,! (fset is !n *a9$ 9 ! l9e4 #fij4--;,d\ble ,optical ,squ>e4--,?is in/rum5t is exactly :at its title indicates1 t is two optical squ>es1 ! "o plac$ exactly ov] ! o!r1 ! "o reflect+ to ! "r h& & ! o!r to ! left4 ,a simpl] "n1 h[ev]1 w\ld be an optical cross4 ,?is arrangem5t ( reflectors greatly ext5ds x use4 ,fir/1 z reg>ds ! #ij1 ?is ne$ n dep5d 9 any way ^u ! position ( ! obs]v]1 z two objects may be obs]v$1 "o to ! "r & "o to ! left1 to appe> to cut ! direct =w>d l9e ( sight1 & !re=e to cut ! base l9e at ! exact position ( ! in/rum5t at "r angles to x4 ,secondly1 an int]m$iate /ation c be f\nd 9 direct l9e betwe5 any two po9ts1 z ! #ij #ij =ms ?is l9e4 #fia4--,! arrangem5t ( ! optical "p ( ! in/rum5t is %[n ,fig4 #cjh4 ,! two index glasses ,,cd are fix$ at equal angles to ! direct l9e ( sight ,,eo4 ,! two horizon glasses ,,ab are sup]impos$ ) ! int]val ( a small space1 #a_/af in*1 betwe5 !m4 ,! horizon glasses are ea* sep>ately adju/$ s t _! reflect+ planes are respectively #de to ! index glass f :i* !y receive ! reflections4 ,! diamet] ( ! in/rum5t z usually made is ab\t #b in*es2 its dep? #g_/h in*4 ,! weight is ab\t #i oz4 ,x is g5]ally c>ri$ 9 a light1 solid lea!r1 sl+ case4 ,total weight ) in/rum5t1 #ab oz4 #fib4--;,exam9ation & ,adju/m5t ( ! ,d\ble ,optical ,squ>e4--#a4 ,place ! in/rum5t1 z already describ$ = ! optical squ>e1 at a /ation int]m$iate betwe5 two pickets4 ,exam9e ! "r angles1 fir/ look+ t[>ds "o picket & !n t[>ds ! o!r f ! same position1 z ) ! optical squ>e1 turn+ x ov] = ?is exam9ation4 #b4 ,turn ! in/rum5t half r\nd & exam9e x ?is way also by turn+ x ov] aga9 9 l mann]4 ,adju/ ei!r horizon glass if requir$4 #c4 ,n[ take ! position = ! eye ( ! =m] #ij & see :e!r ! extreme pickets appe> 9 true position by ! exact co9cid5ce ( _! images at #ahj4 #d4 ,d ?is aga91 fac+ ! opposite way & turn+ ! in/rum5t half r\nd4 ,if ! extreme pickets /ill range 9 l9e f ! c5tral /ation ! adju/m5t is p]fect4 ,if !y d n d s half ! error mu/ be correct$ by return+ to ! fir/ & second adju/m5ts to f9d out betwe5 :i* pair ( mirrors x lies4 ,= ?is adju/m5t ! in/rum5t is mu* bett] to be plac$ ^u ! top ( a tripod1 z ! position ( ! axis %\ld rema9 fix$ aft] turn+ x ov] or *ang+ ! direction ( ! in/rum5t4 ,x is only f sev]e accid5t t ! mak]'s adju/m5t w be di/urb$4 #fic4--;,apomecomet]4--,?is little in/rum5t1 ! inv5tion ( ,mr4 ,r4 ,c4 ,mill>1 is int5d$ to measure ! height ( build+s1 trees1 etc41 by measur+ ! di/ance f ! v]tical ^u ! surface ( ! gr\nd4 ,x p]=ms "o ( ! functions ( ! box sextant 9 ! same mann] z ! optical squ>e1 t is1 to measure a s+le angle by reflection4 ,! angle measur$ is #de1 consequ5tly by measur+ a space ^u level gr\nd up to a v]tical1 ! v]tical w be kn[n1 ?is be+ equal to ! horizontal4 ,( c\rse ?is w always be approximate1 z ! gr\nd w seldom be truly level2 b by tak+ a position1 ev5 on an incl9e1 z ne>ly z possible level ) ! object1 a v fair e/imate may be made4 ,horizontal di/ances may be measur$ 9 ! same mann] f a p]p5dicul> to any l9e4 #fid4--,! in/rum5t is con/ruct$ 9 exactly ! same mann] z ! optical squ>e j describ$ z reg>ds its mirrors & its adju/m5ts1 b ! faces ( ! mirrors are fix$ at ! angle ( #bb #cj1 s z to give a reflection ( #de1 ^u pr9ciples fully discuss$4 ,9 ,fig4 #caj1 ,a is ! index glass1 ,b ! horizon glass1 ,e ! p9-hole sight4 ,!re is a w9d[ opposite ! index glass1 & "o beh9d ! horizon glass1 ea* suffici5t to take 9 a wide field ( view at ab\t #de & 9 ! direct l9e ,e to ,h4 ,^! w9d[s close by rotation ( ! cas+ ( ! box1 :i* is made z ! optical squ>e4 ,:5 clos$ ! in/rum5t is du/-tight & may be c>ri$ 9 ! wai/coat pocket loose1 or 9 a light snap lea!r case4 ,its size is #a in*es diamet]1 #c_/h in* 9 ?ickness1 weight #b oz4 9 ,g]man silv]4 #fie4--,! ,use ( ! ,apomecomet]4--,to measure ! altitude ( a build+ ! op5 side ne>e/ level is select$1 & a /ation = obs]vation is tak5 :i* is at a di/ance ?\ght to be approximate to ! height4 ,! in/rum5t is held edgewise ) ! p9-hole sight to ! eye1 & ! reflection ( a po9t ( ! build+ ab\t level ) ! eye is obs]v$ by direct vision ?r\gh ! in/rum5t4 ,at ! same "t !re w appe> a reflection ( ! summit ( ! build+4 ,if we n[ walk backw>ds or =w>ds1 z ! case dem&s1 keep+ sight ( a level object1 z = in/ance 9 ,fig4 #caa ! pl9? ( a build+1 !n at a c]ta9 po9t ! summit ( ! build+ w appe> by co9cid5t reflection4 ,! height ( ! object w be ! same z ! di/ance plus ! height ( ! obs]v]'s eye4 ,?is di/ance may be measur$ on ! gr\nd1 or if a r\gh e/imate is suffici5t x may be /epp$1 ! pr9ciple ( :i* is %[n by ,fig4 #caj 9 ! l9e ,,oh1 be+ equal to ,,fh4 ,if a "p ( an object is requir$ to be measur$ su* "p may be tak5 on ! horizontal plane1 z = in/ance ! height ( ! figure 9 ,fig4 #caa1 by ab be+ ed1 z ! base ab c easily be measur$4 ,an approximate may be f\nd by dropp+ a small pebble at a & at b & !n measur+ ! di/ance ap>t ( ^! pebbles4 ,illu/ration3 ,fig4 #caj4--,optical details ( ! apomecomet]4 ,illu/ration3 ,fig4 #caa4--,s*eme = measur+ heights4 #fif4--,! di/ance ( an inaccessible object may be measur$1 z = in/ance a buoy at sea1 by measur+ 9 any /raight l9e d\ble ! di/ance & tak+ equal angles !reto by ! apomecomet] on any direct l9e4 ,an approximate idea may be =m$ by walk+ ov] measur+ po9ts4 ,z = in/ance1 b be+ a buoy at sea1 ,fig4 #cab1 walk f e1 at :i* a walk+-/ick may be set up1 t[>ds an object o4 ,at ,e ! buoy & object o w appe> to be co9cid5t4 ,!n drop a /one or make a m>k directly "u ! in/rum5t4 ,walk on till beyond ,e & turn to face e4 ,n[ 9 return+1 ! buoy & ! object e w appe> co9cid5t at ,e4 ,! di/ance ,,ee is d\ble t ( ! int]m$iate a to b4 ,illu/ration3 ,fig4 #cab4--,s*eme = measur+ di/ances4 ,,footnotes3 #ch ,po/hum\s ,works1 p4 #ejb2 also ,animadv]sions to ! ,ma*9a ,cle/is ( ,helvetius1 p4 #di4 #ci ,phil4 ,trans41 vol4 xlii4 p4 #aee4 #dj ,phil4 ,trans41 vol4 xxxvii4 p4 #adg4 #da ,ibid4 p4 #cdj4 #db ,see ,ni*olson's ,navigator's ,assi/ant4 #dc ,pe>son's ,practical ,a/ronomy1 p4 #ecg4 #dd ,ibid4 p4 #egg4 #de ,gli ,/rum5ti a ,reflessione p] ,mesur>e ,angoli1 by ,g4 ,b4 ,magnaghi1 #ahge4 #df ,description ( a ,new ,quadrant1 by ,george ,adams1 #agdh4 #dg ,adams' ,geometrical ,essays1 edit$ by ,william ,jones1 #ahjc4 #dh ,prov4 ,pat5t ,no4 #bfbd2 ,*ri/oph] ,george1 #ahfh4 #di ,see ,briti% pat5ts--,w9t]1 #agfj1 ,no4 #geb2 ,ould1 #agia1 ,no4 #ahdb2 ,nug5t1 #agid1 ,no4 #aihj2 ,wright1 #agif1 ,no4 #bjha2 ,cook1 #agif1 ,no4 #bjhg2 ,roxby1 #ahbb1 ,no4 #dfie2 ,glov]1 #ahci1 ,no4 #hbef2 ,lane1 #aheg1 ,no4 #affi2 ,rahill1 #ahfj1 ,no4 #ahde1 etc4 #ej ,adams' ,geometrical ,essays1 p4 #bfd1 #ahjc4 ,,*apt] ,,xv4 ,,graphic ,,survey+ ,,in/rum5ts ,,& ,,appliances ,,connect$ ,,!re)--,,plane ,,tables--,,alidades--,,telescopic ,,arrangem5ts--,,subt5se ,,measurem5ts--,,v>i\s ,,devices ,,= ,,hold+ ,,! ,,pap]--,,cont9u\s ,,pap]s--,,adju/m5t ,,( ,,tripod ,,heads--,,me?od ,,( ,,us+--,,edgewor?',s ,,/adiomet]--,,sket*+ ,,protractor--,,sket*+ ,,case--,,cam]a ,,lucida1 ,,etc4 #fig4--,plane ,tables4--,^! in/rum5ts h be5 us$ = fill+ 9 ! great] numb] ( topographical surveys 9 all c\ntries4 ,!y possess ! m]it t any intellig5t1 untra9$ p]son c be readily br\ght to compreh5d _! manipulation 9 ! "w to be p]=m$1 z angles ( position ( objects are tak5 directly by draw+ l9es po9t+ to !m f a po9t ^u a %eet ( pap] /ret*$ ^u a table4 ,9 new c\ntries natural objects )\t v m>k$ outl9e are conv5i5tly def9$ = position4 ,! objection to ?is me?od1 f a po9t ( view ( ! practical surveyor1 is t ! "w :i* c be done ) equal facility 9 a com=table (fice f ! field-book is ) ?is in/rum5t p]=m$ 9 ! op5 air1 "u risk ( ra91 du/1 & o!r atmosph]ic discom=ts affect+ bo? ! p]son & ! mat]ial on :i* he works4 ,b = c\ntries :]e ! climate c be dep5d$ ^u1 ! facility ) :i* surveyors ) little exp]i5ce c map details = fill+ 9 sup]ior triangulations made ) ! !odolite1 its use has ga9$ mu* fav\r4 ,natives c be easily taught to use x1 & ! *eck on _! "w ?r\gh ! previ\s triangulation is p]fect4 ,! subject ( plane tables w 9 ^! pages be consid]$ only 9 its g5]al aspect1 ) ! examples ( a few good in/rum5ts1 ref]r+ ! read] :o c>es to foll[ ! subject fur!r to an excell5t pap] by ,mr4 ,j4 ,pi]ce1 ,jun41 read be=e ! ,in/itute ( ,civil ,eng9e]s1 ,febru>y1 #ahhh4ea #fih4--,! ,plane ,table 9 its simple/ =m consi/s ( a small draw+-bo>d m\nt$ ^u a firm tripod /&1 & is %[n at ,fig4 #cac4 ,illu/ration3 ,fig4 #cac4--,simple plane table4 ,a rule t]m$ an alidade1 ) sights plac$ at its ends1 gives ! direction ( any object f a giv5 po9t on ! %eet ( pap] /ret*$ ^u ! table1 to :i* a f9e l9e is drawn by an ,,hh p5cil to po9t ! direction4 ,! alidade sometimes c>ries a tr\gh compass fix$ ^u x1 b ?is is g5]ally a sep>ate in/rum5t :i* is plac$ aga9/ its fiducial or rul+ edge to give a magnetic nor? to s\? l9e1 to :i* all o!r l9es are assum$ to take angul> direction4 ,a loose _s level is also provid$1 by means ( :i* ! bo>d may be set level by %ift+ ! legs ( ! tripod4 #fii4--,plane ,table ) ,telescope4--,:]e great] ref9em5t ( obs]vation is requir$ ?an is possible ) sights1 a telescope is m\nt$ on ! alidade1 :i* moves 9 ! v]tical plane ^u an axis1 s t x may be direct$ 9 a l9e> direction ) ! fiducial edge ( ! rule to any po9t 9 azimu?4 ,! telescope sometimes c>ries a level1 s t ! table may be set level by means ( ! alidade4 ,illu/ration3 ,fig4 #cad4--,plane table4 ,illu/ration3 ,fig4 #cae4--,tripod /&4 #gjj4--;,a class ( plane table :i* meets all necess>y ref9em5t = ord9>y fill+ 9 ( field "w is %[n 9 ! illu/ration1 ,fig4 #cad4 ,?is ne>ly resembles ^? made by ! au?or = fill+ 9 details ( ! great trigonometrical survey ( ,india4 ,! draw+ surface ( ?is table consi/s ( a loose panel :i* /ret*es ! %eet ( pap] by press+ x into its frame1 :]e x is aft]w>ds held by a pair ( l$ges :i* fit at _! ends into long slots4 ,! panel ( ! bo>d1 %[n 9 detail ,fig4 #caf1 is m\nt$ ^u a firmly brac$ tripod /&4 ,! head ( ! tripod /&1 %[n ,fig4 #cae1 is secur$ to ! bo>d ) a c5tral screw 7n %[n7 :i* p]mits ! bo>d to be set 9 any direction1 x be+ ! rule t ! edge ,w %\ld always take a nor? to s\? direction4 ,?ree screws sss at ! corn]s ( ! triangul> head c be rais$ or l[]$ by mill$ heads f ! "u side4 ,^! screws p]mit ab\t #ae ( adju/m5t to ! table )\t any un/ead9ess1 z ! c5tre screw clamps x f9ally h>d d[n ^u !m :5 all adju/m5ts are made4 ,a small tr\gh =m ( magnetic compass a is plac$ ^u ! rule to /rike ! magnetic nor? to s\? l9e1 to :i* all angles are ref]r$ 9 transpos+ ! "w ( ! plane table4 ,! diaphragm ( ! telescope is provid$ ) a plat9o-iridium po9t fix$ v]tically at ! mutual focus ( ! object-glass & ! eye-piece4 ,a pair ( po9ts to subt5d an angle to measure a /aff = di/ance1 ,fig4 #cai1 is a conv5i5t addition4 ,illu/ration3 ,fig4 #caf4--,panel bo>d ( plane table4 #gja4--,! ,telescopic ,arrangem5t ( ! alidade is v>i$ 9 diff]5t c\ntries4 ,9 "s cases x is plac$ ne> to "o end1 :i* is p]haps bett] ?an 9 ! c5tre ( ! rule1 z x is m easily read4 ,9 ! mod]n ,fr5* milit>y alidade a prismatic eye-piece is us$1 s t obs]vation is made by look+ directly d[n ^u ! eye-piece ( ! telescope4 ,9 ! ,prussian alidade adju/m5t is made to ! /&>d ( ! telescope s z to br+ ! horizontal axis ^u :i* x moves level1 t ! telescope may move 9 azimu?1 h[ev] irregul> or unev5 ! surface ( ! pap] on ! bo>d may be4 ,?is is necess>y = any great degree ( ref9em5t 9 ! plane table1 z ! surface ( a piece ( wood ^u :i* ! pap] is /ret*$ w be almo/ c]ta9 to w>p if expos$ to all wea!rs1 & ?is1 add$ to ! small wid? ( ! alidade1 c sc>cely reta9 ! axis 9 exact horizontality1 plac$ z x is high above ! surface ( ! table4 ,"s plane tables made by ! au?or = ,g5]al ,rob9son = ,indian s]vice 7 ( papi]-ma* to rem$y ! defect ( w>p+1 b ev5 ?is mat]ial w>ps ^u exposure4 ,plane tables h be5 made 9 ,g]many ( metal & ( glass1 b 9 ?is case ! weight is a great objection4 ,! au?or has f\nd surfac$ slate v good1 b x has ! same objection ( too mu* weight = a portable in/rum5t4 ,illu/ration3 ,fig4 #cag4--,/anley's plane table4 ,illu/ration3 ,fig4 #cah4--;,alidade to plane table4 #gjb4--,lat]al ,adju/m5t to ! ,alidade4--,! au?or's plan ( obta9+ ?is is to increase ! practical wid? ( ! rule by giv+ x an ext5d$ po9t ( support on "o side s z to set ! telescope 9 azimu?4 ,= ?is con/ruction ! telescope is m\nt$ ^u a plate ) an arm ext5d+ outw>ds ^u ! back ( ! rule4 ,?is has a mill$-head$ screw plac$ at ! ne> extremity ( ! arm4 ,! screw is ins]t$ 9 a deep bu% = we>2 ?is atta*m5t is %[n 9 section ,fig4 #cah4 ,! adju/+ screw ,a has a coll> fix$ ^u its po9t :i* is c5tr$ ^u a tight screw tapp$ into ! mill$ head4 ,?is coll>1 z x does n turn ) ! mill$ head1 does n abrade ! surface ( ! pap] by contact ) x4 ,a small cross level ,b is put ^u ! arm betwe5 ! mill$ head & ! /&>d ( ! telescope4 ,! "u side ( ! rule is cut away or plac$ obliquely to ! surface1 s t x be>s on ! out] rul+ edge only4 ,! mill$-head$ screw be+ at its normal position & ! table level1 less ?an half a turn "o way or ! o!r w br+ ! small cross bubble to its c5tre 9 a few seconds = any av]age irregul>ity ( ! surface ( ! table1 & by ?is means cause ! telescope to move correctly 9 azimu?4 ,illu/ration3 ,fig4 #cai4--,subt5se po9ts4 #gjc4--,! ,telescope ,arrang$ = ,subt5se ,measurem5ts4--,:]e a /adium1 art4 #eef1 is to be us$ = e/imat+ di/ances f /ation to /ation1 :5 an ord9>y telescope is us$1 ! au?or places two plat9o-iridium po9ts v]tically f top & bottom ( ! diaphragm1 & adju/s ^! by a screw until a subt5se angle ^u ! /adium ( #a foot cuts ! po9t at a di/ance ( #ajj feet1 or accord+ to ! measurem5ts to :i* ! l& is tak54 ,9 ?is case x is necess>y to h an altitude arc to ! telescope1 z %[n ^u ! alidade 9 ,fig4 #cag4 ,?is has a degree scale read+ by v]ni] to ab\t #c m9utes4 #gjd4--,v>i\s ,devices = ,fix+ ! pap] on ! ,surface ( ! ,table h be5 made4 ,_m pref] simply p9n+ x ) draw+ p9s on a q pla9 p9ewood surface4 ,9 ?is case ! table is bett] slightly sunk r\nd ! edges ) a rabbet ( ! dep? ( ! ?ickness ( ! head ( ! p91 s t ! alidade may re/ firmly ev5 ov] ! p9 heads4 ,! ,fr5* plane tables h v g5]ally roll]s at ea* end ( ! table1 ^u :i* a long slip ( pap] is roll$1 suffici5t = twelve or m /ations4 ,! roll]s = small tables are made ( brass tube ab\t #e_/h in* 9 diamet]4 ,!y commonly move ) a turn-key :i* is ins]t$ 9 a squ>e fitt+ 9 ! end ( ! roll]4 ,! roll]s keep ! pap] tight by means ( rat*et :eels & spr+ pawls at _! ends4 ,?is plan is v conv5i5t = topographical "w1 z = in/ance a riv] may be foll[$ f /ation to /ation "r d[n its c\rse & appe> on a s+le slip1 its be>+ be+ indicat$ by ! compass nor? l9e4 ,fig4 #cbj %[s ! mann] 9 :i* ! au?or has made ?is plane table4 ,illu/ration3 ,fig4 #cbj4--,plane table ) roll]s4 ,illu/ration3 ,fig4 #cba4--;,gurley's plane table adju/m5t4 #gje4--;,adju/m5t ( ! ,plane ,table4--,!re are a great _m devices = ?is4 ,mr4 ,pi]ce1 9 ! admirable pap] already m5tion$1 gives illu/rations ( ! diff]5t plans4 ,"s ( ^! h all ! complication ( ! adju/m5t ( ! /age ( a !odolite1 & "o has sup]add$ to ?is a slide-re/ motion4 ,^! ?+s ( c\rse are necess>y if ! field "w is made to take ! place ( f9i%$ (fice "w4 ,"o g5]al feature ( plane table tripods is "s means ( adju/m5t ( ! table to unev5 gr\nd1 :5 ! tripod-head _c be br\ght ne>ly level4 ,gurley's plane table adju/m5t is p]haps ! simple/ ( any ( ^! devices1 & appe>s to ! au?or to be z good z any o!r4 ,fig4 #cba1 ,d ! table top2 ,a a ball fitt+ turn$ inside & out1 & atta*$ firmly to ! table top2 ,c a socket fix$ firmly 9 ! head ( ! tripod2 ,b a bolt ) globul> head fitt+ ! int]ior ( ,a1 & c>ri$ ?r\gh ! head to a w+$ nut :i* clamps x firmly4 ,a spr+ is plac$ to act aga9/ ! w+$ nut1 s t :5 ?is is slightly loos5$ ! ball fitt+ ,a may move betwe5 ,b & ,c ) mod]ate firmness :5 ! table is be+ set to an angle4 ,illu/ration3 ,fig4 #cbb4--,/anley's high-class plane table4 ,to meet all conditions ! revisor has design$ a high-class plane table %[n at ,fig4 #cbb4 ,?is has a ball & socket r\gh levell+ arrangem5t & p>allel screws = f9e levell+1 circul> motion to table ) clamp & tang5t1 spr+ roll]s = tak+ any l5g? ( pap] & in/antly clamp+ x1 alidade ) extra p[]ful telescope ) v]tical circle divid$ on silv] read+ by two v]ni]s to m9utes ) clamp & tang5t motion1 cross levels1 diagonal scale1 & adju/m5t = sett+ telescope to revolve 9 v]tical plane1 circul> compass ) cross levels & plumb+ b>4 ,! bo>d is g5]ally made #cj #bd4 ,! telescope is /adia read+ & is made ) long s5sitive bubble m\nt$ ^u x or ^u ! v]ni]s if pref]r$ z %[n at ,fig4 #cbc4 ,illu/ration3 ,fig4 #cbc4--,/anley's high-class alidade ) bubble on v]ni]s4 #gjf4--,me?od ( ,us+ ! ,plane ,table4--,! table is fir/ set & levell$ up at a comm&+ position to obs]ve ! ext5t ( c\ntry x is int5d$ to plot f obs]vation f a s+le /ation4 ,let ,fig4 #cbd #a be ! fir/ /ation = plott+ ! enclosure abcdef4 ,draw l9es by ! alidade po9t+ to ^! angles repres5t$ by ! lett]s f a po9t ne> #a4 ,set up a picket or /adium at ! /ation #b :]e x is int5d$ t ! plane table %all next be set up1 & draw ! l9e #a #b di/9ctly on ! pap]4 ,measure ! l9e #a #b ei!r by its subt5se on ! /adium or by direct *a9 measurem5t1 & plot ?is f /ation #a on ! pap] accord+ to ! scale to be work$ to 9 mak+ ! plan4 ,on remov+ ! table set up a picket or di/9ct l& m>k v]tical ) ! position ( /ation #a occupi$ on ! pap]4 ,move ! table to /ation #b at ! measur$ di/ance & set ! direction ( ! bo>d by means ( ! alidade s t ! l9e #b #a cuts ! picket left at /ation #a4 ,n[ draw l9es f /ation #b to all ! po9ts abcde1 cutt+ ! =m] l9es z repres5t$ by dott$ l9es 9 ! figure1 & ! int]sections ( ^! l9es w give ! true positions ( abcde1 accord+ to ! scale select$ = ! base #a #b1 & ^! may be ti$ up to repres5t ! b\nd>ies1 z %[n on ! plane table #b4 ,x w be readily se5 t ! l9e #a #b repres5ts a be>+ 9 azimu?2 s t if ! edge ( ! table be set1 say truly ,n4 to ,s41 9 bo? positions ! l9e on ! pap] #a #b w agree 9 bo? ^! positions ( ! table2 b ! *eck by ! alidade ( ?is l9e is valuable to save risk ( error4 ,illu/ration3 ,fig4 #cbd4--;,diagram ( plane table "w4 #gjg4--,:]e an ext5t ( l& is to be survey$ by ! plane table1 longitud9al b&s ( a mile or s 9 wid? are tak54 ,:]e ! roll] plane table ) cont9u\s pap]1 ,fig4 #cbj1 is us$1 ! =w>d po9ts ( obs]vation are l9$ 9 & ! backw>d ones simply ti$ up1 be+ c]ta9 by obs]vations writt5 9 p5cil ^u ! pap] t id5tical objects are ti$ up f ! positions ( bo? /ations4 ,:]e an object _c be se5 f bo? /ations its position may be indicat$ by ! /adium f a s+le be>+1 or x may possibly be ti$ up f a fur!r advanc$ /ation4 #gjh4--;,edgewor?'s ,/adiomet]4#eb--,! g5]al con/ruction ( ?is in/rum5t is giv5 9 ! inv5tor's specification ( pat5t1 f :i* ! engrav+1 ,fig4 #cbe is tak54 ,! v]ni] plate ( an ord9>y !odolite is ext5d$ to a plate ( ab\t #aj in*es 9 diamet]4 ,?is is adju/$ to level by means ( p>allel plate screws4 ,! plate or plane table is divid$ on its edge 4 ,! "p repres5t+ ! limb ( a !odolite is c>ri$ out f its axis by two arms only3 ^u ^! ! /&>ds ,,rr ( ! telescope are m\nt$4 ,^! /&>ds leave a /rid+ space ne> ! plate1 into :i* any scale ,s ( equal p>ts ) a z]o c5tre is introduc$1 :i* is int5d$ to be us$ = ! plott+1 ! /rid+ space be+ s arrang$ t ! fiducial edge ( ! scale %all pass exactly ov] ! axis ( ! in/rum5t4 ,! /&>ds unite 9 ! same ca/+ to =m ! horizontal axis be>+ ( ! telescope4 ,?is axis p]mits ! telescope to move 9 azimu?4 ,! telescope c>ries a v]tical arc divid$ to degrees1 also a scale ( c5tesimal diff]5ces ( hypot5use & base1 ) ! ord9>y clamp & tang5t adju/m5t ( a !odolite4 ,x is also fitt$ ) a level above x :i* is us$ 9 sett+ up ! in/rum5t4 ,/adia webs are plac$ 9 ! diaphragm & are made adju/able to subt5d ^u ! /adium a p]c5tage ( arc agree+ ) ! unit to :i* ! l& is measur$4 ,! inv5tor does n appe> to h kn[n ! optical error ( ! sy/em propos$ = measur+ di/ance1 art4 #eeh4 ,nei!r does ?is appe> to h be5 recognis$ by o!rs writ+ ^u ! in/rum5t1 :o h g5]ally foll[$ ! late ,j4 ,f4 ,hea!r's description4#ec ,illu/ration3 ,fig4 #cbe4--;,edgewor?'s /adiomet]4 #gji4--,to ,use ,edgewor?'s ,/adiomet]4--,aft] x is set up1 a circul> disc ( pap] ( ab\t an in* less diamet] ?an ! table is held d[n ^u x by f\r spr+ clips4 ,! telescope is direct$ consecutively f object to object1 ! positions ( :i* x is desir$ to take4 ,x is clamp$ by ! screw bel[ ! plate dur+ ! obs]vation4 ,! /adium is plac$ aga9/ ! object & ! di/ance tak5 by ! subt5se ( ! webs 9 ! diaphragm1 :i* may be exact if a con/ant be add$ aft] prop] adju/m5t1 art4 #eeh4 ,if ! /adium be above or bel[ ! horizontal plane x is incl9$ by means ( a sight-hole ?r\gh x1 z orig9ally propos$ by ,gre51 s t ! subt5se is equal "u all conditions4 ,! horizontal di/ance is tak5 by ! diff]5ce ( hypot5use & base1 z %[n on ! v]tical arc1 s t ! record ( a complete obs]vation appe>s = calculation z-- /adium read+ con/ant - altitude correction4 ,?is di/ance is at once set (f f ! c5tre ( ! in/rum5t by ! scale on a l9e drawn ^u ! disc ( pap]1 & obs]vations are writt5 aga9/ ! l9e4 ,9 mak+ a numb] ( obs]vations f "o /ation two or m discs ( pap] may be employ$ to save confusion ( l9es & int]f]5ce ( descriptions4 ,^! pap]s are sep>ately us$ 9 plott+ z protractors by prick+ holes ?r\gh ! /ations def9$ 9 ! field f ! c5tre ( ! disc :i* repres5ts ! /ation ( obs]vation4 #gaj4--,! ,s&hur/ ,protractor1 ,fig4 #cbf1 is a milit>y protractor adapt$ especially = topographical del9eation1 :i* is commonly us$ ) ! plane table4 ,x is diff]5t f _m in/rum5ts ( its k9d 9 hav+ only useful matt] ^u x4 ,x is made ( boxwood1 ^u :i* ! protractor is cut1 & has also "o scale ( #f in*es to a mile 9 y>ds1 at ! l[] edge1 ! t5s ( :i* are c>ri$ across to make p>allels ( #ij 9 ! mann] ( an ord9>y milit>y protractor4 ,ov] ! back ( ! protractor is a scale :i* gives a /&>d = %ad+ slopes ( l& ^u topographical maps1 ,fig4 #cbg1 f #b to #ce1 also l9es = cont\r %ades4 ,a small plummet1 ! cord ( :i* is pass$ ?r\gh a hole 9 ! c5tre1 f :i* ! degrees are protract$1 is suppli$ ) ! in/rum5t4 ,:5 ! protractor is held up1 degrees d[nw>ds1 ! cord ( ! plummet w pass ov] ! degrees & indicate ! angle at :i* x is held4 ,by look+ ov] ! edge ! angle ( incl9ation ( ! l& may be tak5 directly1 z ) a cl9omet]1 or by look+ along ! edge by a second p]son read+ ! plummet ! angles ( altitude may be tak5 m exactly4 ,illu/ration3 ,fig4 #cbf4--,s&hur/ ,sket*+ cl9omet] protractor4 ,illu/ration3 ,fig4 #cbg4--;,example ( scale ( %ades = slopes4 #gaa4--,milit>y ,sket*+ ,bo>d4--,?is sket*+ bo>d1 ,fig4 #cbh1 ! inv5tion ( ,mr4 ,graham ,f4 ,hodgson1 w be f\nd a v great improvem5t ^u ! old patt]n bo>ds4 ,x is design$ to meet ! requirem5ts ( milit>y & o!r (fic]s n conv]sant ) ! high] bran*es ( survey+1 & x w also be f\nd ( great use to surveyors1 explor]s1 & o!r travell]s4 ,x consi/s ( a mahogany bo>d revolv+ on a circul> metal plate atta*$ to a h&le held 9 ! op]ator's left h&4 ,m\nt$ on ! metal plate is a compass1 :i* is visible ?r\gh a glass plate flu% ) ! face ( ! bo>d & ! trac+ pap] or clo? on :i* ! map is made2 ! pap] be+ /ret*$ tightly ov] ! bo>d by means ( roll]s4 ,a magnetic nor? l9e is drawn on ! pap] ov] ! c5tre ( ! compass4 ,! op]ator inv>iably has 8 bo>d 9 its relatively correct position by always keep+ ! magnetic nor? l9e imm$iately ov] ! top ( & align$ ) ! compass ne$le :5 8 sights are tak54 ,illu/ration3 ,fig4 #cbh4 ,top view4 ,"u view4 ,! sights are tak5 by means ( an alidade mov+ along a slott$ b>1 :i* itself slides along a b> fix$ at ! side ( ! bo>d4 ,! object aim$ at is sight$ 9 a mirror atta*$ to ! end ( ! alidade & align$ ) a po9t at its o!r end1 & ! alidade is clamp$ into position by a ?umb-screw on ! slott$ b>4 ,! advantages ( ?is in/rum5t are _m & w only be fully realis$ :5 x is 9 practical use4 ,no backsights are necess>y4 ,sights c be tak5 ) "o h&4 ,! op]ator is always 9 a com=table position & ! object aim$ at is always imm$iately 9 front ( him4 ,! alidade rema9s 9 position by means ( ! clamp screw along ! ray drawn till ! object sight$ at is rea*$ & ! di/ance kn[n1 :i* is m]ely m>k$ (f by means ( ! scale on ! alidade4 ,x is invaluable :5 sket*+ riv]s f laun*es or canoes :5 backsights are (t5 impossible4 ,x is light & portable1 be+ easily c>ri$ slung ov] ! %\ld] 9 a canvas case4 #gab4--,! me?od ( us+ is simple & ensures a great degree ( accuracy ) a m9imum am\nt ( "t & tr\ble3-- 7#a7 ,! trac+ clo? is fir/ fix$ by means ( ! roll]s ov] ! bo>d4 7#b7 ,a magnetic nor? l9e is !n rul$ across ! pap] & pass+ imm$iately ov] ! c5tre ( ! compass visible "u ! pap]4 7#c7 ,! op]ator !n1 hold+ ! bo>d by ! h&le und]nea?1 proce$s to make 8 map & fir/ br+s ! magnetic nor? l9e imm$iately ov] ! top ( & align$ ) ! compass ne$le4 7#d7 ,he !n f "s po9t1 m>k$ z 8 />t+ po9t on ! pap]1 proce$s to take sights to any objects he may wi% to del9eate on 8 map4 ,^! sights are tak5 by means ( ! alidade fix$ above ! bo>d4 ,! sight+ rule is pu%$ along a slott$ b>1 :i* itself slides along a b> at ! edge ( a bo>d until ! edge ( ! alidade is aga9/ ! />t+ po9t & is sight$ on ! object aim$ at4 ,! object is sight$ 9 a small mirror fix$ at ! end ( ! alidade & align$ ) ! po9t at its o!r end4 ,! alidade is !n clamp$ into position ) ! ?umb-screw on ! slott$ b> & ! op]ator draws 8 ray correspond+ ) ! direction ( ! object aim$ at4 ,! di/ance is !n m>k$ (f on ! scale on ! alidade4 7#e7 ,:5 ! op]ator moves to ! next /ation no back-sight is necess>y4 ,he at once puts ! bo>d into its relative correct position by m]ely revolv+ x until ! magnetic nor? l9e is aga9 ly+ ov] ! top ( & align$ ) ! compass ne$le & he !n proce$s to take all necess>y sights at t /ation4 ,illu/ration3 ,fig4 #cbi4--;,cavalry sket*+ case4 #gac4--;,cavalry ,sket*+ ,case4--,?is =ms a v conv5i5t explor+ sket*+ bo>d1 p]mitt+ sket*es to be made on horseback :ile en r\te4 ,! patt]n %[n 9 ,fig4 #cbi is t ( ,capta9 ,w4 ,v]ni]4 ,x consi/s ( a small bo>d #i in*es by #g in*es1 at two sides ( :i* !re are small roll]s to hold pap] #g in*es wide & f #c feet to #f feet 9 l5g?1 accord+ to its ?ickness4 ,two /\t indi>ubb] b&s1 :i* hold a small /raight-edge to scale 9 any position on ! pap] ) suffici5t firmness to be able to draw a l9e aga9/ x1 are pass$ ov] ! bo>d4 ,a small compass on "o side ( ! bo>d indicates direction4 ,aft] "o sket* is made1 a new "p ( ! pap] is roll$ =w>d4 #gad4--;,cam]a ,lucida--,optical ,compass4--,9 new c\ntries :]e l&m>ks are n cle> a sket* ( ! g5]al aspect ( ! c\ntry w make ! po9ts ( triangulation m cle>4 ,:]e ! plane table is n us$ ^! sket*es may be made ) accuracy z to positions by ! use ( ! photograph cam]a1 ! cam]a lucida1 or po9ts ( obs]vation may be tak5 9 correct be>+ by ! optical compasses4 ,^! latt] in/rum5ts are describ$ 9 ! au?or's ,treatise on ,draw+ ,in/rum5ts1 sev5? edition4 ,,footnotes3 #ea ,proc4 ,in/4 ,civil ,eng9e]s1 vol4 xciii4 "p iii4 pap] ,no4 #bcjh4 ,see also ,milit>y ,survey+ 9 ! ,field1 by ,major ,! ,hon4 ,m4 ,g4 ,talbot1 ,pr(42 ,pap]s ,royal ,eng9e]s1 vol4 xiv4 p4 #be4 #eb ,pat5t ,no4 #abjb1 ,d4 ,r4 ,edgewor?1 ,april #ahff4 #ec ,hea!r's ,survey+ ,in/rum5ts1 #ahgj1 p4 #he4 ,,*apt] ,,xvi4 ,,in/rum5ts ,,= ,,measur+ ,,l& ,,& ,,civil ,,works ,,directly--,,*a9s--,,v>i\s ,,tell]s--,,/&>d ,,*a9s--,,arr[s--,,drop ,,arr[--,,vice ,,= ,,adju/+ ,,*a9--,,ca9k',s ,,rule ,,= ,,incl9es--,,/eel ,,b&s--,,wire ,,l& ,,measures--,,comp5sation ,,sy/ems--,,l95 ,,tapes--,,(fset ,,rods--,,p9e ,,/&>d ,,rods--,,rods ,,) ,,iron ,,core--,,beam ,,compass ,,rods-- ,,co9cid5t ,,measurem5ts--,,comp5sat$ ,,rods--,,base ,,l9e ,,app>atus--,,coa/ ,,survey ,,l9es--,,p]ambulator--,,p$omet]--,,pass omet]--,,s\nd+ ,,*a9s-- ,,s\nd+ ,,l9es--,,telemet]s--,,h& ,,rods--,,rules4 #gae4--,! ,in/rum5ts ,g5]ally ,employ$ = ,measur+ ,l& are *a9s1 /eel b&s1 & tapes4 ,:]e roads are r\ghly measur$1 p$omet]s are commonly us$4 ,:]e v exact measurem5ts are requir$1 rods h be5 us$4 ,r\gh approximate measurem5ts are obta9$ by /epp+1 ) ! use ( ! passomet] to c\nt ! /eps4 #gaf4--,l& ,*a9s4--,al?\gh ^! are made 9 _m qualities ! =ms v>y v little4 ,!y are too well kn[n to ne$ mu* description4 ,9 ! ,briti% ,isles & "s ( our colonies ! *a9 ( #ajj l9ks1 equal to #ff feet1 ! inv5tion ( ,edmund ,gunt] ab\t #afbj1 is g5]ally us$1 #aj squ>e *a9s 7#ajj1jjj squ>e l9ks7 giv+ ! /atute acre1 pres5t+ a decimal sy/em ( measurem5t mu* 9 advance ( any o!r at ! pres5t "t4 ,! be/ l& *a9s are made ( /eel1 :i* is aft]w>ds h>d5$ & temp]$ to spr+ temp]1 9 ! process ( :i* ! surface is burnt (f ) asphalt v>ni% 9 ord] to produce a cov]+ to resi/ ! ru/+ effects ( moi/ure4 ,/eel *a9s are made light & /rong4 ,! light *a91 ( ,no4 #ab ,birm+ham wire gauge1 weighs "u #e lbs4 ,! /rong *a91 ( ,no4 #h ,b4,w4,g41 weighs ab\t #ab lbs4 ,a light *a9 ( #ej l9ks1 ( weight "u #c lbs41 is sometimes us$ ) ! complete *a9 ( #ajj l9ks = tak+ (fsets4 ,illu/ration3 ,fig4 #ccj4--,l& *a9 & arr[s4 ,all ! be/ *a9s1 :e!r ( /eel or iron1 are made ) long l9ks =m$ by turn+ up ! ends ( a l5g? ( wire4 ,?ree small oval l9ks are plac$ betwe5 ea* pair ( long l9ks4 ,^! ?ree int]val l9ks are f\nd to cause ! *a9 to k9k less ?an :5 only two are us$4 ,ea* oval l9k is sawn ?r\gh at ! meet+ l9e1 :i* is br\ght up on "o flat side ( ! oval 9 b5d+ x f ! wire4 ,! saw-cut =ms ! po9t ( adju/m5t4 ,! small l9k is aft]w>ds re-sawn & clos$ to %ort5 x1 or =c$ op5 to l5g!n x4 ,!re are g5]ally f\r swivels 9 ! l5g? ( ! *a91 two ( :i* are at ! h&les3 ^! prev5t ! *a9 f becom+ twi/$ 9 turn+ ! h&les ov] 9 use4 ,a swivel is %[n ,fig4 #cca at ,s4 ,iron *a9s are sometimes galvaniz$ to prev5t ru/4 ,?is process1 h[ev]1 makes ! *a9 mu* m brittle1 & _c be recomm5d$4 ,x may be not$ t all l9k *a9s l5g!n ) use4 #gag4--,tell]s are small pieces ( brass susp5d$ to ! *a9 by a sp>e l9k plac$ at e t5 l9ks4 ,!y divide ! *a9 decimally f ei!r end equally4 ,proce$+ f "o end ( ! *a9 ! tell]s read #aj1 #bj1 #cj1 #dj1 #ej1 & ! o!r end !y read by subtraction f ! complete *a93 #ajj - #aj #ij1 #ajj - #bj #hj1 #ajj - #cj #gj1 & #ajj - #dj #fj4 ,fig4 #cca %[s deta*$ pieces ( *a9 ) value ( ! tell]s figur$ "u4 ,s ins]t$ swivel4 ,! #ej tell] %[s ! l9k atta*m5t4 ,a %[s ! position at :i* ! arr[ or o!r m>k is plac$ to comm5ce or f9i% ! *a9 measurem5t1 ! h&le be+ includ$ 9 ! fir/ l9k4 ,^! tell]s are liable to cat* & get dragg$ (f 9 *a9+4 ,:5 ?is *a9 is us$ abroad1 or f> f home1 x is well to h an extra set ( tell]s to repair losses4 ,illu/ration3 ,fig4 #cca4--;,gunt]'s l& *a9s4 #gah4--;,ins]t$ ,tell]s4--,?is =m ( tell] is pref]r$ by _m1 ,fig4 #ccb4 ,x is mu* less liable to get dragg$ (f1 b x is n consid]$ q s di/9ct1 & x is a little liable to get clogg$ ) grass & we$s4 ,illu/ration3 ,fig4 #ccb4--;,ins]t$ tell]s4 #gai4--,! au?or's design = ins]t$ tell]s is %[n ,fig4 #ccc4 ,^! are p]haps q z di/9ct z ! la/4 ,! holes 9 wet wea!r fill up ) mud & ! surfaces keep bright1 s t !y rema9 v readable4 ,!re is mu* less drag1 & ! *a9 !re=e we>s long]4 ,illu/ration3 ,fig4 #ccc4--,/anley's ins]t$ tell]s4 #gbj4--;,feet ,*a9s are usually made #ajj feet1 m r>ely #ej feet4 ,!y are g5]ally made 9 foot l5g?s1 b sometimes = flexibility are pref]r$ 9 #f-;in* l5g?s4 ,!y are commonly made ( ,no4 #h ,b4,w4,g4 /eel or iron4 ,! weight ( #ej feet is #f lbs42 #ajj feet1 #aa lbs4 ,if made ( light /eel1 ,no4 #ab ,b4,w4,g41 ! #ajj feet weighs #f lbs4 #gba4--,m9+ ,*a9s us$ 9 m9]al di/ricts are made g5]ally #aj fa?oms1 or #fj feet1 #f-;in* l9ks c\nt$ (f by tell]s 9 fa?oms4 ,!y are made entirely ( brass4 ,! weight is ab\t ! same 9 brass z /eel--,no4 #h ,b4,w4,g41 #i lbs4 ,occasionally !y are made extra /rong1 ,no4 #g ,b4,w4,g42 weight #ab lbs4 ,9 coal m9es ,gunt]'s *a9s are g5]ally us$4 #gbb4--,metre ,*a9s are made #bj or #be metres long4 ,!y are m>k$ ) tell]s at e two metres ) a pla9 r+ at ! metre4 ,! tell]s are g5]ally ( ! ins]t$ k9d1 ,fig4 #ccb4 ,9 tak+ measurem5ts ! sign ( ! tell] is d\bl$3 ?us ! ord9>y #a or #aj is c\nt$ #b metres2 ! #b1 #d1 & s on4 #bj-metre *a9s 9 light /eel1 ,no4 #ab ,b4,w4,g41 weigh #d lbs42 /rong1 9 ,no4 #h ,b4,w4,g41 #i lbs4 #be-metre1 light1 #f lbs42 /rong1 #aa lbs4 ,a l& *a9 is g5]ally secur$ = c>ry+ by a lea!r /rap ) a buckle4 ,occasionally x is c>ri$ 9 a sailclo? bag ) a /rap ov] ! %\ld]4 #gbc4--,/&>d ,*a9s4--,^! are ( ! same =m z ! ord9>y /eel *a91 b all ! l9ks are h>d sold]$ aft] be+ adju/$ l9k by l9k4 ,!y are n int5d$ to be us$ = regul> *a9+1 except x be = lay+ d[n r\gh base l9es4 ,_! special employm5t is to te/ *a9s1 or to set out ) two pegs on a /raight piece ( gr\nd a /&>d l5g? or /ation :]e ! common *a9s 9 use may be te/$ daily4 ,a /&>d *a9 is commonly enclos$ 9 a box ) a lock to prev5t its accid5tal use = an ord9>y *a94 #gbd4--;,arr[s4--,^! are sometimes call$ p9s4 ,t5 =m a set4 ,!y are %[n ) ! *a9 9 ,fig4 #ccj1 & are commonly made ( ! same wire z ! *a9--,no4 #h ,b4,w4,g4 ,!y are mu* bett] made "o gauge /\t] 7equal to ab\t #a_/g in*71 & pref]ably ( h>d5$ /eel ?an ( iron4 ,! common l5g? is #ae in*es4 ,:]e hea?1 /ubble1 or woodl&s prevail #ah-;in* are bett] = use1 & 9 "s exceptional cases ev5 #b-;feet are v conv5i5t4 ,surveyors go+ to new c\ntries are recomm5d$ to take ! long] arr[s z well z ^? suppli$ ) ! *a94 ,x is common ei!r to tie a %ort l5g? ( sc>let webb+ ^u ea* r+ ( ! arr[ or to sew a piece ( r$ flannel or bunt+ ^u x to f9d x easily 9 long grass4 ,arr[s are sometimes c>ri$ 9 a quiv] ) a /rap ov] ! %\ld]1 ,fig4 #ccd1 :i* leaves ! h&s ( ! =e *a9man free to remove ob/ructions :]e !y occur4 #gbe4--;,drop ,arr[1 ,fig4 #cce4 ,:]e gr\nd is v hilly x is common to r\ghly level ! *a9 by hold+ ! l[] position %\ld] high1 ei!r by guess "w or by us+ any k9d ( r\gh h& level or cl9omet] to asc]ta9 ?is4 ,! arr[ is !n dropp$1 & ! po9t1 held at fir/ lightly 9 ! gr\nd1 is press$ h>d d[n or ano!r arr[ supplant$ = x4 ,! *a9 9 ?is case is us$ 9 odd multiples ( l9ks z !y occur1 ( :i* record is tak5 sep>ately at ea* /ation4 ,9 go+ d[nhill a drop arr[ answ]s v well4 ,9 go+ uphill a plummet to ! la/ arr[ is bett]4 ,"s use ! drop arr[ z a plummet1 c>ry+ = ?is purpose 9 ! pocket a piece ( f9e :ipcord1 ) a b5t hook ti$ to "o end1 to be us$ :5 requir$4 ,illu/ration3 ,fig4 #ccd4--,quiv] ) arr[s4 ,illu/ration3 ,fig4 #cce4--;,drop arr[4 #gbf4--;,exam9ation & ,adju/m5t ( ,*a9s4--,respectable mak]s s5d out *a9s te/$ to )9 half ( "o ( ! small l9ks ( /&>d1 t is1 )9 a qu>t] ( an in*2 b 9 use ?is error may increase ei!r by ! b5d+ ( ! long l9ks ( ! *a91 :5 x becomes %ort]1 or 9 ! m g5]al case ( friction f we> & f /ra91 by :i* x becomes long]4 ,9 ,london1 /&>ds are fix$ ^u ! pavem5t 9 ,trafalg> ,squ>e & at ! ,guildhall4 ,^! /&>ds are also fix$ at _m municipal t[n halls4 ,surveyors v commonly lay d[n a /&>d on ! pavem5t1 or by pegs on a level gravel pa?4 ,:]e a peg is us$ x %\ld be driv5 home ne>ly to ! surface4 ,x %\ld if possible be made ( a piece ( he>t ( oak #ab in*es long & ab\t #b in*es squ>e4 ,! /&>d l5g?1 :i* may be set (f by a /&>d *a9 or new /eel tape1 %\ld be f a saw-cut across ! c5tre ( "o peg to a simil> cut on ! o!r4 ,x is well also to h ! c5tre space 7#ej l9ks7 indicat$ by a small] peg4 #gbg4--,! ,*a9 to be ,adju/$ %\ld be fir/ exam9$ & its long l9ks set /raight by means ( a hamm] on a flat1 h>d /one or anvil1 aft] :i* ! error w be1 if x has be5 mu* us$1 t x is too long4 ,x %\ld be !n laid 9 direct l9e on ! /&>d j describ$1 & /ret*$ lightly ) a pull ( ab\t #g lbs41 & !n left to re/4 ,assum+ x too long1 ! c5tre ( ! *a9 %\ld be obs]v$ to asc]ta9 :i* half is ( ! great] l5g?1 !n %ort l9ks %\ld be tak5 out at di/ribut$ di/ances1 if m ?an "o be requir$1 by twi/+ ! l9k op5 9 a vice1 & op5+ & clos+ ano!r l9k to re/ore ! *a94 ,illu/ration3 ,fig4 #ccf4--,/anley's vice = adju/+ & repair+ l& *a9s4 #gbh4--;,*a9 ,vice4--,! l9ks ( /eel *a9s c seldom be twi/$ op5 )\t break+1 & brok5 l9ks _c be re/or$ by /eel l9ks4 ,iron l9ks answ]1 b !y are v /iff to twi/ op54 ,g5]ally x w be f\nd be/ = pr(essional m5 to repair ! *a9 ) sp>e brass l9ks4 ,^! we> v well4 ,:]e a smi? is ne> ) 8 vice & a light hamm] ! l9ks are readily op5$4 ,x (t5 occurs 9 op5 di/ricts & abroad t no smi?'s %op is to be f\nd4 ,to meet ^! cases ! au?or has con/ruct$ a special vice1 z %[n ,fig4 #ccf4 ,?is vice is let into a piece ( h>d wood--an old oak po/ answ]s admirably4 ,9 /one di/ricts x is p]haps bett] to let x into a /one & fix x by p\r+ hot lead r\nd x4 ,! "p ,b is us$ = an anvil = /raight5+ ! l9ks4 ,! vice ,v holds ! l9k edgewise v firmly by br++ up ! slide ,j by means ( ! screw ,s4 ,! l9k may !n be knock$ op5 by ! pane end ( a light hamm]4 ,! l9k is clos$ aga9 9 ! same mann]4 ,if ! vice be left out ( doors ! screw %\ld be well greas$ & ! :ole cov]$ ) a lead5 cov]4 ,! weight ( ! vice is ab\t #f lbs4 ,x is made ( ca/ iron ) *ill$ face1 or ! jaws are fac$ ) /eel4 #gbi4--,op5+ & ,clos+ ! ,*a9 = ,use4--,! *a9 is mo/ readily unfold$ by tak+ ! two h&les 9 ! h& & walk+ away f x z x lies on ! gr\nd4 ,x is mo/ conv5i5t to place x ab\t #de1 & half a *a9 l5g? f ! fir/ /ation1 ea* *a9man tak+ a h&le & mov+ to 8 position4 ,! only dang] 9 undo+ a *a9 is f two *a9m5 tak+ "o h&le ea* & walk+ 9 opposite directions1 9 :i* case1 if !re happ5s to =m a k9k1 ! opposite movem5t ( ! two m5 w probably /ret* or break ! *a94 ,9 clos+ ! *a9 x is tak5 by ! middle l9ks & fold$ up two l9ks at a "t till ! h&les are rea*$4 ,if ! l9ks be plac$ consecutively 9 position r\nd ! axis =m$ by ! fir/ l9ks1 x may be fold$ up v compactly 9 a twi/$ =m ready = ! /rap1 by :i* x is c>ri$1 to be pass$ r\nd x4 #gcj4--;,*a9+ is p]=m$ by two *a9m51 t]m$ ! lead] & foll[]4 ,! foll[]1 hav+ press$ a /ake into ! gr\nd = a />t+ po9t1 !n places ! c5tre ( ! outside ( ! h&le ( ! *a9 aga9/ x4 ,! lead] takes t5 arr[s 9 8 "r h& & "o h&le ( ! *a9 9 8 left1 & walks directly t[>ds a po9t :i* is to be ! t]m9ation ( ! measurem5t1 /opp+ at ne>ly ! l5g? ( ! *a91 exam9+ ! *a9 to see t x is /raight4 ,he !n places an arr[ lightly outside ! c5tre ( 8 h&le4 ,! foll[] looks ov] ?is arr[ to ! di/ant /ation to see :e!r x is 9 direct l9e4 ,if x be n s1 he waves 8 "r or left h& once1 twice1 or ?rice = #a1 #b1 or #c in*es = movem5t to "r or left4 ,! foll[] picks up ! arr[s consecutively z left by ! lead]1 & :5 he has ! t51 #aj *a9s h be5 measur$1 :i* is !n record$ 9 ! field-book1 or e>li] ?an ! t5 if a %ort] di/ance or object completes ! measurem5t4 ,x is mo/ important to obs]ve t if an arr[ be tak5 = ! fir/ /ation1 ! foll[] hav+ t5 c\nts n9e only = ! fir/ t54 ,to prev5t accid5t x is !re=e saf] to />t f a /ake or o!r l&m>k1 n "o ( ! arr[s4 ,"s surveyors advise elev5 arr[s4 ,if elev5 be us$1 "o %\ld be di/9ctly m>k$ f ! re/ s z nev] to be c\nt$4 ,?is may be done by omitt+ ! r$ webb+ tie1 or us+ a gre5 tie = ! odd arr[4 ,! ,fr5* always make ! drop arr[ ! elev5? arr[1 :i* is nev] c\nt$ 9 direct *a9+4 ,illu/ration3 ,fig4 #ccg4--;,ca9k's rule = correct+ incl9es4 #gca4--;,ca9k's ,rule = correct+ incl9es 9 *a9+ is ! inv5tion ( ,mr4 ,?os4 ,ca9k1 ,c4,e41 ( ,malv]n1 ,fig4 #ccg4 ,x is made f\r-fold1 ea* fold be+ "o l9k4 ,! l9k is divid$ decimally along ! inside ( ! rule4 ,on ! out] edge ( ! rule !re is a scale m>k$ degrees1 a "p ( :i* is subdivid$ :]e ! scale is op5 to read clos]1 t is1 to #bj or #cj m9utes4 ,^! degree divisions1 :i* read up to #af on "o side ( ! rule1 indicate ! space f ! end ( ! rule to be all[$ 9 addition = ! same degrees ( incl9ation ( ! l& up to #d l9ks ( measurem5t4 ,on ! opposite side ( ! rule ! incl9ation scale is c>ri$ f #af to #bb #aj4 ,= ^! high] numb]s ! l5g? ( ! rule is fir/ set (f1 & !n plus su* "p ( ! rule z is indicat$ by ! position m>k$ ^u x ( ! requir$ numb] ( degrees4 #gcb4--,to ,use ,ca9k's ,rule4--,! foll[] has a cl9omet] ( "o ( ! k9ds %[n1 ,figs4 #bfj or #bfd4 ,he notes at />t+ ! position ^u ! face or body ( ! lead] t corresponds ) ! height ( 8 own eye4 ,he takes ! incl9ation ( ! l& to ?is po9t ( ! lead]'s body :ile he is /&+ upright at "o end ( ! *a9 & ! lead] /&+ at ! o!r1 not+ ! numb] ( degrees %[n by ! cl9omet]4 ,he !n places ! rule 9 ! direction ( ! *a91 ) ! numb] ( degrees indicat$1 9 front ( ! arr[1 & moves ! h&le ( ! *a9 to ?is position4 ,= ! sake ( v]ification1 if he has a second arr[ he may place x 9 ! new position1 :i* gives ! true all[ance4 ,9 ei!r case ! lead] moves ! *a9 =w>d by ! am\nt requir$ & places 8 arr[ ready to cont9ue ! "w4 ,by ?is me?od x is se5 t !re is no aft] calculation or sep>ate record necess>y = undulat+ l&1 b ! true horizontal position is giv5 correctly at ea* *a9 measur$4 ,! same =m ( rule is made = feet & metres4 #gcc4--;,9 m\nta9\s c\ntries ! eight l9ks ( ! rule is insuffici5t all[ance = common incl9ations4 ,su* c\ntries are measur$ mu* m accurately by "s sy/em ( subt5se measurem5t1 = :i* see ,*apt] ,,xii42 b :]e a small piece ( sudd5 /eep incl9ation occurs half a *a9 may be tak51 & ! numb] ( degrees indicat$ ^u ! rule be d\bl$1 s t ! full rule1 in/ead ( tak+ #bb only1 w take #dd4 #gcd4--,/eel ,b&s = measur+1 t]m$ /eel b& *a9s1 are made 9 v>i\s =ms 9 ?is c\ntry1 & sold by ne>ly all opticians4 ,!y are mu* light] ?an *a9s ( equal /r5g?1 & are made ( /&>d l5g?4 ,!y are also light] to use1 be+ smoo? & )\t any projection4 ,on ! o!r h& ! read+ is less di/9ct ?an ) ! *a91 & !y ne$ m c>eful usage 9 *a9+4 ,!y also require oil+ be=e be+ put by4 ,f ! ?9ness ( ! metal !y are altoge!r m delicate & less durable ?an ! *a9s = h>d we>2 b x is ?\ght by _m to be a comp5sation t !y are always ( true l5g?4 ,illu/ration3 ,figs4 #cch1 #cci1 #cdj4--,/eel b&s & tapes4 ,illu/ration3 ,fig4 #cda4--,"o l9k ( /eel b&4 #gce4--,! b&s commonly us$ = l& measur+ are made #c_/h1 1 #e_/h1 & in* wide1 ( ,nos4 #bf & #bd ,b4,w4,g4 9 ?ickness1 respectively4 ,! *a9 is divid$ into l9ks by a small /ud rivet$ ?r\gh ! c5tre ( two small wa%]s1 a l>ge /ud be+ plac$ at ! fives & an oval plate held by two rivets at ! t5s1 :i* are num]ically indicat$ 9 pla9 engrav$ figures1 z %[n 9 detail1 ,fig4 #cda b1 or p]=at$ ) holes indicat+ ! numb] ( t5s4 ,^! b& *a9s are made 9 l9ks1 feet1 metres1 or to any =eign measure to ord]1 & ( any l5g? correspond+ ) l& *a9s4 ,weights1 approximately--#ajj feet3 in*1 #g lbs42 #e_/h in*1 #d lbs42 in*1 #d lbs4 #ajj l9ks3 in*1 #d lbs42 #e_/h in*1 #b lbs42 in*1 #b lbs4 #bj metres3 in*1 #e lbs42 #e_/h in*1 #d lbs4 #gcf4--,/eel b& measures are also made ) divisions ?r\gh\t1 et*$ ^u !m ) acid 9 su* a mann] t ! divisions & figures /& 9 relief up to ! orig9al surface1 :]eas ! new surface1 :i* is et*$ back to =m ! gr\nd1 appe>s dull4 ,! brightness ( ! figures & divisions on ! dull gr\nd makes !m easily read4 ,^! b&s are divid$ into l9ks1 feet & in*es1 metres & decimet]s1 or clos] quantities ei!r on "o or bo? sides ( ! b& z requir$4 ,) ! et*$ b& !re is p]haps a little risk ( weak places f ov]-et*+1 al?\gh ^! b&s are mo/ c>efully made1 b p]haps ?is is n great] ?an 9 ! ins]t$ /ud b&1 :]e weak places are necess>ily caus$ by ! loss ( wid? at ! po9ts :]e ! holes are made = ! /uds1 :]e9 moi/ure hides aft] use 9 damp wea!r4 #gcg4--,! /eel b&s h h&les ! same z a l& *a94 ,!y are w\nd ^u a /eel cross1 ,fig4 #cdj4 ,!y are commonly plac$ 9 a w9d-up case simil> to t ( an ord9>y measur+ tape1 b 9 /eel1 provision be+ made t "o ( ! pair ( h&les may be secur$ ab\t ! position ( ! axis ( ! tape = w9d+ x up4 ,9 ,fig4 #cch ! axis is made v l>ge1 s t ! h&le may be press$ 9 f an op5+ 9 "o side ( x4 ,! newe/ idea is to cut a slit 9 "o side ( ! plate up to ! c5tre1 z %[n1 ,fig4 #cci4 ,9 ?is case ! h&le & b& are put 9 f ! side1 s t ! axis is no l>g] ?an is necess>y to take ! h&le4 ,a /rap is plac$ on ! side ( ! case = hold+ x4 ,?is is %[n cut (f to admit sight ( ! h&le4 #gch4--,! ,fr5* make ! h&le g5]ally ,t-%ap$ & holl[ 9 ! cross "p1 :i* r5d]s x v light & p]haps less cramp+ to hold4 ,! arr[s are v commonly held by loops to ! cross on :i* ! b& is w\nd4 ,?is g5]al arrangem5t is v portable & conv5i5t to c>ry2 x is %[n ,fig4 #cdb4 #gci4--,wire ,l& ,measures4--,:]e long op5 /ret*es ( new c\ntry are to be measur$1 x is common to employ a /eel wire *a91 ( #e *a9s or ( #ejj feet 9 l5g?1 fitt$ ) a pair ( /rong cross h&les only4 ,illu/ration3 ,fig4 #cdb4--;,fr5* l& measure4 ,illu/ration3 ,figs4 #cdc1 #cdd4--,m>*ant's #ejj-;feet b&4 #gdj4--,! au?or has made _m *a9s ( #ejj l9ks2 9 ,fig4 #cdd a "p ( "o is %[n full size4 ,?is b&1 z we may t]m x1 is w\nd ^u a reel 9 an iron case1 ,fig4 #cdc4 ,a spr+ brake is plac$ at ! position ,a1 :i* holds ! reel & prev5ts ! b& f spr++ out into loose hoops :5 x is run out4 ,! #ej & #ajj l9ks are indicat$ by %ort l5g?s ( brass tube plac$ ov] ! b&--s+le at ! #ej l9ks1 b num]ically indicat$ by numb] ( b&s z #b1 #c1 & #d *a9s4 ,9 ,fig4 #cdd a #ej & a #cjj l9ks are %[n2 weight1 #c lbs4 ,?is flat1 n>r[1 /eel b& *a9 0 unkn[n until introduc$ to ! notice ( ! pr(ession 9 ! fir/ edition1 #ahij4 ,x is n[ 9 v g5]al use1 & l5g?s may be _h f /ock ( #b1 #c1 #d1 or #e *a9s1 or #bjj1 #cjj1 or #djj feet w\nd ^u a /eel cross4 ,illu/ration3 ,fig4 #cde4--,ri*mond's t5sion h&le4 #gda4--,ri*mond's ,t5sion ,h&le4--,v>i\s devices h be5 employ$ = giv+ equal t5sion to *a9s & b&s to ensure equality ( measurem5ts4 ,salt]'s spr+ balance has be5 v commonly us$ atta*$ to "o h&le ( ! *a9 to give a uni=m pull1 say ( #ae lbs4 ,?is appe>s to answ] v well4 ,mr4 ,ri*mond1 surveyor1 ( ,sydney1 has devis$ a v simple plan = t5sion ( light b&s1 :i*1 be+ light] & atta*$1 is mu* m conv5i5t ?an ,salt]'s balance4 ,?is is %[n ,fig4 #cde4 ,! b& passes ?r\gh a fitt+ 9 ! c5tre ( ! h&le1 & a spiral spr+ is fix$ to ?is & ! b& at a %ort di/ance along x4 ,by pull+ ! h&le a giv5 t5sion c be appli$1 :i* is %[n by ! m>k x rea*es t[>ds ! end ( ! b&4 ,?is is adju/$ to /&>d l5g?1 & a small not* is plac$ 9 ! c5tre ( ! end1 f :i* a plummet may be susp5d$ if necess>y4#ed ,! engrav+ is ( a slightly modifi$ =m by ! au?or1 9 :i* a ?9 tubul> cap cov]s ! free end ( ! b& to save ?is expos$ "p f accid5ts4 ,illu/ration3 ,fig4 #cdf4--;,copp] case !rmomet] = susp5d+ to a b& *a94 #gdb4--;,*a9 & ,b& ,!rmomet]4--,:]e v great accuracy ( *a9 or b& measurem5t is aim$ at1 temp]ature is tak5 to all[ = expansion ( ! metal4 ,a ?9 pla9 glass !rmomet] ( ! cl9ical =m is ! mo/ s5sitive ( any4 ,?is is c>ri$ 9 a wood5 pull-(f case l9$ ) indi>ubb]4 ,:5 x is us$ x is plac$ ^u ! gr\nd by ! side ( ! *a94 ,! delicacy ( ! cl9ical =m ( !rmomet] is (t5 object$ to by ! practical surveyor1 h5ce !re are sev]al o!r =ms ) boxwood & ivory scales4 ,^! are n v satisfactory1 z ! boxwood & ivory reta9 ! heat ( ! body1 f be+ c>ri$ 9 ! pocket1 = a long "t aft] exposure4 ,! au?or has enclos$ ! cl9ical =m ( !rmomet] 9 a copp] case ) op5 face1 ,fig4 #cdf4 ,! copp] be+ a good conductor ( heat1 ?is is v s5sitive to ! temp]ature ( ! air4 ,two turn-d[n hooks are plac$ at ! ends ( ! tube to susp5d x on ! b&4 ,! !rmomet] /em has two indi>ubb] caps1 s t x w be> dropp+ on grass4 ,x is conta9$ 9 ! same =m ( pull-(f case z ! cl9ical4 ,illu/ration3 ,fig4 #cdg4--,littlejohn's temp]ature h&le4 #gdc4--,! coeffici5t ( expansion = /eel betwe5 #cb & #bab ,fahr4 is ab\t #jjjjab1 :i* is less ?an #ja in* p] degree p] *a94 ,temp]ature corrections c !re=e be recognis$ only ^u v exact "w1 appreciable only :5 long b&s ( ! ,m>*ant type1 lately describ$1 ( f #e *a9s to #aj *a9s 9 l5g? are us$4 #gdd4--,mr4 ,littlejohn has pat5t$ an adju/able h&le = temp]ature4 ,?is is divid$ = all[ance = ! #ajj-;feet or o!r b& = e degree ,fahr4 or c5tigrade4 ,fig4 #cdg4 ,! h&le is set to ! temp]ature z x *anges dur+ ! day4 ,x (f]s1 p]haps1 ! highe/ ref9em5t 9 ord9>y l& measurem5ts4 ,illu/ration3 ,fig4 #cdh4--,/anley's repair+ sleeve4 #gde4--,repair+ ,sleeve = ,/eel ,b&s4--,! revis] has pat5t$ a sleeve :i* w be f\nd useful1 z by its use a brok5 b& c be imm$iately & p]man5tly repair$ 9 ! field )\t ! use ( tools4 ,!y are made to fit all siz$ b&s1 b x is necess>y t ! correct siz$ sleeve %\ld be us$4 ,"o ( ^! sleeves is %[n atta*$ to a b& at ,fig4 #cdh4 ,9 ord] to effect a repair x is m]ely necess>y to clean ! brok5 ends ( ! b&1 & ins]t !m into ! sleeve1 !n hold a light$ mat* "u x until ! sold]+ mat]ial is melt$1 :5 ! repair is complet$4 ,! c5tral hole 9 ! sleeve is to enable ! us] to see :5 ! brok5 ends are 9 contact1 & ! o!r two are to indicate :5 ! sold]+ mat]ial is melt$1 :i* takes place :5 x ei!r bubbles up 9 or runs away f ^! holes4 ,illu/ration3 ,fig4 #cdi4--,l95 ,tape4 ,illu/ration3 ,fig4 #cej4--,small /eel pocket tape4 #gdf4--,l95 ,tapes4--,?is mo/ useful implem5t1 ,fig4 #cdi1 is "o ( ! mo/ unsatisfactory measures ! trad] & us] has to d )4 ,x consi/s1 z is well kn[n1 ( a tape oil$1 pa9t$1 & v>ni%$1 :i* is roll$ up 9 a lea!r case :5 out ( use4 ,:5 ! wea!r is moi/ x %r9ks1 & :5 dry x exp&s4 ,if x be too heavily pa9t$ x becomes brittle & rott52 if x be lightly pa9t$ x rema9s m flexible1 b is m affect$ by moi/ure4 ,a good tape be>s v well a /ret*+ =ce ( #g lbs4 to #ad lbs41 b if /ra9$ ov] ?is x is p]man5tly /ret*$4 ,!re is no plan kn[n to ! au?or by :i* ^! defects c be rem$i$4 ,num]\s attempts h be5 made--(t5 valueless or worse--"s1 al?\gh popul>1 m]e claptraps1 su* z ! ins]tion ( wire4 ,! be/ tapes = /r5g? & p]man5cy are made entirely ( gre51 h&-made1 unblea*$ flax4 ,! tape is said to come f ,holl& to ?is c\ntry4 ,^! are at fir/ oil$ ) a dry+ oil 7boil$ l9se$ oil71 & :5 season$ = a mon? or s1 pa9t$ once or twice ) :ite lead col\r--n too ?ickly4 ,! pr9t+ is m p]man5t if done 9 oil2 b ! tape is some:at m flexible if ! figures are /5cill$ 9 ,indian ink & ! :ole aft]w>ds ?9ly v>ni%$ ov] ) copal v>ni%4 ,! great secret = pres]v+ ! tape is to use x v c>efully & only 9 f9e wea!r4 ,9 wet wea!r = tak+ (fsets a light /eel #ej-l9k *a9 is q z conv5i5t z ! tape1 & saf]4 ,tapes are divid$ into l9ks1 feet & in*es1 metres1 & all measures z requir$4 ,a decimal y>d is commonly plac$ on tapes = measur+ e>? "w4 ,= use ) ! *a9 a #ff-;feet tape is usually employ$1 b _m ?9k a #cc-;feet bett]1 us+ ! *a9 = dim5sions above ?is4 ,= measur+ build+s1 #ej-;feet or #ajj-;feet tapes subdivid$ to in*es are employ$4 #gdg4--,/eel ,tapes4--,?9 /eel tapes1 #c_/h1 1 & #e_/h in* wide are 9 v ext5sive use4 ,!y are m accurate & m co/ly ?an l95 tapes1 b less flexible & less durable4 ,:]e dim5sions are important !y %\ld always be us$ = %ort measurem5ts4 ,9 all cases x is advisable = a surveyor to keep a /eel tape = exam9ation ( ! l5g?s ( l95 tapes 9 use4 ,!y are made to all ! measurem5ts ( l95 tapes4 #gdh4--,pocket ,/eel ,tapes #f feet to #ab feet1 ,fig4 #cej1 are us$ m g5]ally by me*anical eng9e]s4 ,^! tapes1 :i* are v light1 are held op5 by a cat*1 & clos$ by a spr+4 ,illu/ration3 ,fig4 #cea4--;,jo9t$ (fset rod1 top & c5tre4 #gdi4--,(fset ,rods are g5]ally made #aj l9ks long1 ei!r 9 "o piece or jo9t$ 9 ! c5tre ) a bayonet jo9t4 ,!y are ab\t #a-a_/h in*es 9 diamet]1 dim9i%+ t[>ds ! top to #g_/h in*1 & made ei!r ( yell[ p9e or a%4 ,a hook is commonly put at ! top1 ,fig4 #cea1 :i* takes ! h&le ( a *a9 to draw x ?r\gh a h$ge or o!r ob/ruction4 ,! au?or's plan ( mak+ ?is is %[n at ,h4 ,! l[] end ( ! (fset is %od ) a /eel or wr\ght iron socket po9t1 s t x may be set up 9 ! gr\nd & us$ if requir$ z a picket4 ,b&s are pa9t$ alt]nately black & :ite at e l9k4 ,squ>e or flat rods are occasionally us$ = ! same purpose1 b !y are n g5]ally s conv5i5t4 ,! (fset is ,us$ 9 ! mann] ( an ord9>y rule to take rectangul> %ort measurem5ts f ! *a9 z x lies ^u ! gr\nd1 commonly 9 ord] to obta9 ! cont\r ( irregul> outl9es4 #gej4--,measurem5t by ,rods has become less g5]al ?an =m]ly1 f ! great] accuracy ( ,kon/at or ,inv> /eel tapes1 by :i* practically correct base l9es may be laid d[n4 ,= geodetic works requir+ ! greate/ accuracy ! bases h be5 laid ) rods ( v>i\s =ms4 ,^! rods w be briefly describ$4 ,x is only 9 ! con/ruction ( iron bridges1 ro(s1 etc41 t rods are at pres5t g5]ally employ$ 9 ! "w ( ! civil eng9e]4 #gea4--,p9e ,/&>d ,rods1 made ( /raight-gra9$ p9ewood season$ five or six ye>s & !n well soak$ 9 l9se$ oil1 make good /&>d rods4 ,! ord9>y l5g? 9 use is #aj feet by #a in*es squ>e4 ,if ! rod be us$ = butt measurem5t ! ends are tipp$ ) gun-metal 9 :i* a turn$ /eel /ud is h>d-sold]$4 ,! /ud is aft]w>ds gr\nd to true face 9 a la!1 & left ( /&>d l5g? at #fj ,fahr5heit 7#aee c5tigrade71 ,fig4 #ceb4 ,a disc ( brass #a in* diamet] is inlaid at e foot = #e feet f "o end ( ! rod1 ) a l9e at ! true foot4 ,^! rods1 aft] ! "w ^u !m is f9i%$1 are lightly ,fr5* poli%$ to keep !m clean & to prev5t ! effects ( moi/ure4 ,! effect ( temp]ature ^u deal 0 f\nd by ,roy to be ab\t ! same z ^u glass--#jjjjjhe1 av]age ( total l5g? p] degree c5tigrade1 :i* is ab\t ?ree-f\r?s t ( iron4 ,illu/ration3 ,fig4 #ceb4--,"o end ( a p9ewood butt rod4 ,illu/ration3 ,fig4 #cec4--,s--,block squ>e4 #geb4--,:]e butt rods are us$ = cont9u\s measurem5t1 x is necess>y t !y be br\ght v c>efully toge!r4 ,9 base l9e measurem5t ?ree or f\r are us$1 b = metal "w or masonry two #aj-;feet only are g5]ally employ$4 ,x is necess>y t ! rods %\ld lie ^u a /raight surface or be support$ 9 a /raight l9e4 ,9 br++ !m toge!r1 a piece ( indi>ubb] #a_/h in* or s 9 ?ickness tempor>ily plac$ at "o end w prev5t any palpable di/urbance ( ! p]cussion if ! fix$ rod be well weight$4 ,"o #e-;feet m fully divid$ butt rod is v commonly suppli$ ) a pair ( #aj-;feet rods = supplem5tal measurem5t4 #gec4--;,angle-piece4--,a solid angle-piece ) two planes at "r angles is v conv5i5t = use ) butt rods to give means ( scrib+ ! true l5g? d[n to a surface1 ,fig4 #cec ,s4 #ged4--;,butt ,rods ) ,iron ,core4--,:]e rods are to be us$ = prep>+ iron "w x is bett] to h an iron core ?r\gh ! rod1 t may exp& & contract ) ! metal on :i* !y are us$4 ,! rods t ! au?or has design$ = ?is purpose are made out ( a l5g? ( season$ p9e #b in*es squ>e1 sawn d[n & turn$ cut sides outw>ds to prev5t w>p+4 ,a #aj-;feet l5g? ( iron /eam tube ab\t in* diamet] is pa9t$ sev]al times & !n b\nd r\nd ) pap] soak$ 9 p>aff94 ,?is is plac$ 9 a pair ( meet+ grooves1 z %[n 9 section ,fig4 #cee4 ,! two p9e flit*es are cross-tongu$ toge!r & glu$ up ) ! ins]t$ tube betwe5 !m4 ,! tube has a turn$ /eel cap plac$ ov] ea* end1 ,fig4 #ced1 & ?is is gr\nd 9 a la! to true /&>d at ! temp]ature ( #fj ,fahr4 ,a /eel p9 is plac$ ?r\gh ! c5tre ( ! rod to indicate #e feet4 ,! f9i%$ size ( ! rods is #b in*es squ>e4 ,! au?or has made ^! rods 9 sets1 consi/+ ( two #aj-;feet & "o #e-;feet pack$ toge!r ) an angle-piece1 ,fig4 #cec ,s1 9 a deal case4 #gee4--,! #e-;feet ,rule is ( /eel1 in* by in*1 inlaid 9 a piece ( dry p9e1 altoge!r ( only half ! ?ickness ( ! rods1 s t x /&s ! correct height = c5tral butt measurem5t1 ,fig4 #cef4 ,! rule is divid$ into feet & in*es1 ) "o foot to eigh?s4 ,a c5tigrade !rmomet] is plac$ 9 "o ( ! rods to indicate ! prevail+ temp]ature1 & a small piece ( scale %[+ am\nt to be all[$ 9 #aj feet p] degree c5tigrade = temp]ature above or bel[ #aee c5tigrade is engrav$ ^u ! !rmomet] scale4 ,! coeffici5t = ! expansion ( wr\ght iron is giv5 by ,"l ,kelv9 z #jjjjai mean p] degree c5tigrade4 ,illu/ration3 ,figs4 #ced1 #cee1 #cef4--;,butt rods ) iron core4 ,:]e a long l5g? is laid d[n = a base l9e or o!r purpose1 x is bett] to take ! !rmomet] read+ at ea* measurem5t & def] correction to ! completion ( ! "w2 ! temp]ature errors may !n be add$ toge!r z a total1 & ! space all[ance may become a measurable quantity4 ,= example1 say t5 #aj-;feet l5g?s give by ^! unit$ c5tigrade degrees1 plus & m9us1 %[n at sep>ate read+s #afg1 & t ! /&>d ( ! rods is true at #aee4 ,!n #afg - 7#aj #aee7 #ab p] foot total all[ance1 t is1 #ab #aj feet #jjjjai #jbbh feet or #bgcf in*es to be add$4 ,9 measur+ iron ( c\rse no correction has to be made4 #gef4--;,beam ,compass ,measurem5ts are occasionally pref]r$ = iron "w4 ,9 ?is case ! beam is mov$ f c5tre pun* m>k to m>k along a surface by ! beam produc+ a scrat* = ! =w>d position 9 :i* to place ! pun* m>k4 ,rods ( p9e are commonly employ$4 ,figs4 #ceg1 #ceh w suffici5tly illu/rate ! in/rum5ts4 ,illu/ration3 ,fig4 #ceg4--;,beam compasses4 ,illu/ration3 ,fig4 #ceh4--,/&>d scale4 ,illu/ration3 ,fig4 #cei4--;,co9cid5ce rods4 #geg4--,! ,me?od ( ,co9cid5ce 9 measurem5ts by rods has (t5 be5 appli$ to measurem5t ( base l9es4 ,! plan consi/s 9 all[+ "o rod1 or a light] cont9u\s "p ( x1 to pass ! o!r rod1 s t a l9e cut to /&>d on "o rod may be read into "o on ! o!r4 ,! be/ plan to d ?is is to h a scale fix$ along ! face ( "o rod ne> its end1 z %[n ,fig4 #cei1 & to h an ext5sion f ! o!r end ( ! second rod to pass alongside ?is scale1 s t two l9es may be br\ght into co9cid5ce4 ,! rod ,b has a fix$ scale b plac$ on top ( x at "o end4 ,! rod ,a has a scale protrud+ f x4 ,?is scale may be jo9t$ ) a good gr\nd jo9t at ,j = portability4 ,! rods are laid lightly toge!r1 & any f9al adju/m5t is giv5 by light taps ) a small hamm] or mallet ^u "o or ! o!r side ( ! /ud ,p until exact co9cid5ce ( ! l9es %[n at b is br\ght ab\t4 ,?is tapp+ op]ation appe>s a r r\gh process1 b practically x is v exact4 ,illu/ration3 ,fig4 #cfj4--;,bessel comp5sat$ rod4 #geh4--;,comp5sat$ ,rods4--,! plan us$ by ,bessel = ! measurem5t ( a base ^u ! %ores ( ! ,baltic 9 #ahcf is look$ ^u z a model ( ! mo/ p]fect "w ( its k9d4 ,! rods 7 compos$ ( two b>s ( iron hav+ surfaces accurately plan$1 ) a simil> b> ( z9c plac$ betwe5 !m4 ,! b>s 7 laid "o on ! o!r1 b n 9 contact1 ! surfaces be+ kept ap>t by glass plates1 ^u :i* !y c\ld slide ) little friction4 ,! l9e> expansion ( z9c p] degree c5tigrade is ab\t #jjjjbib 7,fizeau72 t ( iron mu* less ?an half ?is--ab\t #jjjjaai 7,?omson74 ,! b>s are atta*$ to ea* o!r 9 su* a way t ! expansion ( ! z9c may act 9 ! opposite direction to ! expansion ( ! iron4 ,! =m foll[$ = ! con/ruction is %[n 9 ,fig4 #cfj :]e ,,ii are ! iron b>s1 ,z z9c4 ,! l5g? ( ! z9c requir$ = comp5sation betwe5 ! junctions is f\nd 9 ! equation-- 7,s ,z77#jjjjaai7 - ,z7#jjjjbib7 #j1 ,s be+ ! total l5g? ( ! /&>d rod 9 feet1 & ,z ! l5g? ( z9c 9 feet requir$ = comp5sation4 ,?is plan is t adopt$ = ! comp5sation ( p5dulums4 ,= ! v]ification ( a rod x may also be made to =m ! rod ( a p5dulum1 by :i* temp]ature expansion & contraction ^u ! sy/em w be cle>ly indicat$ by diff]5ce ( "t rate 9 ! *ange ( temp]ature dur+ night & day4 ,?is te/ becomes important :]e great precision is aim$ at1 z ! expansion 9 metals v>ies accord+ to _! purity & /ate4 ,! /&>d l9es 9 rods made ^u ?is model are plac$ ^u small ins]t$ discs ( plat9um plac$ ne> ! ends1 :i* are read by microscopes 9 co9cid5ce ^u a pair ( rods4 #gei4--;,colby ,comp5sat$ ,rods1 ! inv5tion ( ,major-,g5]al ,t4 ,f4 ,colby1 :o 0 = tw5ty-sev5 ye>s sup]9t5d5t ( ! ,ordnance ,survey1 ^u :i* ^! rods 7 us$4 ,ea* rod is compos$ ( "o rod ( iron & "o ( brass1 :i* are s arrang$ 9 pairs t ! diff]5ce ( expansion ( ^! metals %all act to dim9i% ! am\nt ( entire expansion at ! po9ts measur$1 a quantity equal to its increase by temp]ature1 9 a mann] to be describ$4 ,! ,rods are ea* made #aj feet #ae in*es long1 #e in*es broad1 & #ae in*es deep4 ,fig4 #cfb i is a side elevation ( "o rod1 ,fig4 #cfc ib plan ( iron & brass rods1 ,fig4 #cfe ib p]spective view4 ,by ?is x w be se5 t ! rods are plac$ edgewise4 ,! di/ance ap>t is #aabe in*es4 ,!y are support$ 9 ! middle ^u roll]s1 ,fig4 #cfb ,f4 ,!y are firmly fix$ toge!r at _! c5tres by transv]se /eel cyl9d]s1 ,fig4 #cfc ,,rr #ae in*es diamet]1 ea* rod be+ left free to exp& or contract f ! neutral c5tral po9t indep5d5tly ( ! o!r4 ,! neutral po9t is =m$ ( a ,t-piece ,e1 ,fig4 #cfc1 fix$ firmly on ! bottom ( ! box bx4 ,at ! extremity1 & at "r angles to ea* ( ^! b>s1 is a flat /eel tongue1 ,figs4 #cfd1 #cfe ,a1 #fb in*es long1 #aa in*es broad1 & #jbe in* ?ick1 :i* projects #cbe in*es f ! side ( ! iron b> i4 ,! tongue ,a is jo9t$ by d\ble conical pivots at f & f1 :i* =m axes p]p5dicul> to ! surface ( ! tongue1 all[+ x to be incl9$ to slightly diff]5t angles to ! direction ( ! b>s accord+ to ! expansion or contraction ! sy/em exp]i5ces by heat4 ,! pivots are #je in* diamet]1 & are plac$ at #bc in*es f ! end ( ! tongue next ! brass b>4 ,on ! tongue at ,p1 flu% ) its upp] surface1 a small /ud ( plat9um is ins]t$1 ^u :i* a small dot is /ruck to =m ! po9t ( /&>d measurem5t4 ,illu/ration3 ,colby ,comp5sat$ ,measur+ ,rods4 ,fig4 #cfa4--;,end ( rod m\nt$ ) microscopes1 tre/les & gr\nd plate4 ,! b>s are plac$ 9 /rong wood5 boxes1 to ! bottoms ( :i* are fix$ ! plates t hold ! brass roll]s ^u :i* ! b>s are support$1 ,fig4 #cfb ,f1 & ! c5tral /ay ,e m5tion$ be=e prev5ts any displacem5t ( ! b>s :5 ! rods are held by ! roll]s ,,rr4 ,to protect ! tongue ,a1 :i* projects beyond ! boxes1 !re is a special cov]+ nozzle hav+ a hole & cov] ov] ! dot4 ,a level is plac$ on "o ( ! b>s1 :i* is se5 ?r\gh a w9d[ 9 ! lid ( ! box4 ,at ! ends ( ! box plates are fix$ = support+ ! tripod ( ! d\ble comp5sat$ microscope1 ,fig4 #cfa ,d1 employ$ to obs]ve ! /&>d po9ts ( "o pair ( rods br\ght by adju/m5t to true position ,,mm4 ,a pair ( sight vanes :i* %ut d[n are plac$ on ! ends ( ! box = sett+ ! rods approximately 9 l9e4 ,illu/ration3 ,colby ,comp5sat$ ,measur+ ,rods4 ,fig4 #cfb4--,side elevation ( po9t ( support ( rod4 ,fig4 #cfc4--,side elevation ( c5tre1 ) section ( box bx4 ,fig4 #cfd4--,plan ( rods & comp5sat+ arm4 ,fig4 #cfe4--,p]spective view ( ! same4 ,two ,rigid ,tripod ,/&s ,fig4 #cfa ,s are us$ to ea* ( ! rods plac$ "u ! roll]s ,fig4 #cfb ,f ^u :i* ! b>s are support$ 9 ! box4 ,! tripods c>ry a univ]sal slide-re/ by :i* ! rod may be adju/$ to position bo? 9 horizontal & v]tical planes ,fig4 #cfa ,a4 ,six rods 7 us$ = ! ,ordnance ,survey at "o "t1 & 7 designat$ by ! lett]s ,a ,b ,c ,d ,e ,f4 ,! weight ( ea* rod complete ) microscopes 9 its case is #acf lbs4 ,comp5sat$ ,microscopes4--,! comp\nd microscopes1 ,fig4 #cfa ,,mm1 us$ ) ! ,colby app>atus =m a complete sep>ate in/rum5t1 consi/+ ( two microscopes plac$ p>allel to ea* o!r & unit$ toge!r = read+ ! rods :5 !y are br\ght ) _! /&>d po9ts ! di/ance ap>t t sep>ates ! axes ( ! two microscopes4 ,9 ! int]m$iate space betwe5 ! two microscopes1 & p>allel ) !m1 a telescope ,t is fix$ on ! same piece ( app>atus1 ) adju/m5t = read+ a po9t on ! gr\nd ,g p]p5dicul> to ! measur+ rod4 ,! microscopes are held ap>t by two b>s ( brass & iron #g in*es long1 #je in* broad1 & #jcge in* ?ick1 :i* are plac$ at #be in*es ap>t & secur$ ) ! telescope1 :i* =ms ! fix$ c5tre1 by coll>s to ! bodies ( ! microscopes4 ,! diff]5ce ( expansion ( ! iron & brass ma9ta9s ! sep>ation ( ! microscopes at _! foci at "o di/ance ) e *ange ( temp]ature ( ! air4 ,! object-glasses are ( #b in*es focus4 ,! microscopes are br\ght to adju/m5t & be>+ by levell+ on a tribra* ^: base is fix$ firmly to "o ( ! rod cases1 & by lat]al adju/+ screws4 ,special microscopes are us$ ) ea* ( ! six rods ( ! ,colby app>atus1 & are di/+ui%$ by ! lett]s ,m ,n ,o ,p ,q ,r ,s4 ,! weight ( ea* comp\nd microscope is #e lbs4 ,v full p>ticul>s ( ! ,colby app>atus ) engrav+s ( all p>ts1 are giv5 9 ,! ,ordnance ,survey ,acc\nt ( ! ,measurem5t ( ! ,l\gh ,foyle ,base4 ,9 measur+ a base l9e a piece ( ne>ly level l& is select$1 & ! rods are support$ ^u ! tre/les or tripod /&s at ab\t #c feet f ! gr\nd4 ,! heights ( ! upp] surfaces ( ! tripods are rang$ by a !odolite or level = all int]m$iate po9ts betwe5 ! two ends ( ! l9e4 ,g5]ally twelve tre/les are employ$ ) ^! rods1 :i* are fix$ firmly to ! gr\nd at e /ation by legs well ramm$ 91 ,fig4 #cfa ,,hh4 ,! cases conta9+ ! rods1 or ! rods !mselves1 are made suffici5tly /rong to be support$ ^u two po9ts only )\t s]i\s deflection4 ,! ,colby sy/em ( measurem5t ( base l9es v>i$ 9 detail has be5 employ$ by ne>ly all ! nations ( ,europe & 9 ,am]ica4 #gfj4--,mod]n ,base-l9e ,app>atus4--,! introduction ( ,kon/at /eel 7highe/ grade ,inv>7 tapes & wires has revolutionis$ ! me?od ( measur+ base l9es4 ,^! tapes (f] a means :i* is f> sup]ior to any?+ obta9$ by measur+ b>s1 because !y comb9e ! advantages ( great l5g? & simplicity ( work+1 ) m precision ?an ! %ort] laboratory /&>ds1 provid+ t suitable app>atus is us$ 9 apply+ !m to _! "w4 ,base l9es may n[ be rapidly measur$ ) long ,kon/at /eel tapes s t mu* long] l9es are laid d[n ?an 0 =m]ly ! practice :5 measur$ ) b>s1 ) ! result t any errors t may be introduc$ d n affect ! ultimate expansion s mu* ow+ to ! great] l5g? ( ! base4 ,! coeffici5t ( expansion ( ,kon/at /eel is "u #jjjjjje p] degree ,fahr5heit1 s t provid$ accurate means ( susp5d+ ! tape & read+ x & transf]r+ ! read+s to a plate prop]ly let 9 ! gr\nd are us$1 we h a mo/ exact & rapid me?od = ?is important "w4 ,! tapes are usually #ajj feet or #cj metres long1 b #cjj feet or #ajj metres are (t5 us$4 ,! tapes are a few feet long] ?an ^! measurem5ts1 s t ! r+s are well cle> ( ! read+ l9es4 ,a silk cord is atta*$ to ^! r+s & passes ov] ! end susp5sion supports1 "o ( :i* is %[n at ,fig4 #cff4 ,^! are made ) two /eel b>s rigidly m\nt$ on two tripods2 ^u ! b>s a slid+ c>riage is m\nt$ c>ry+ a pulley runn+ on ball be>+s ) a v]tical motion = f9al adju/m5t ( ! tape = height4 ,a weight is atta*$ to ! o!r end ( ! silk cord to give ! same t5sion z t "u :i* ! tape 0 divid$4 ,illu/ration3 ,fig4 #cff4--,"o ( ! two end supports ( ! b&1 %[+ t5sion weight1 ) cord runn+ ov] ! ball-be>+ pulley4 ,to prev5t cat5]y light int]m$iate /&s1 z %[n at ,b ,fig4 #cfg1 are us$ at ab\t e t5 feet2 ^! h a ris+ cross piece ) guides :i* are adju/able = height & sideways to support ! tape 9 p]fect alignm5t4 ,hav+ ! tape prop]ly susp5d$ ! read+ in/rum5ts1 ,c ,fig4 #cfg1 are plac$ 9 position at ei!r end4 ,^! are m\nt$ on rigid-fram$ /&s & provid$ ) levell+ screws1 cross levels1 transv]se screw motions & movem5t 9 azimu?1 ) clamp & tang5t motions & align+ telescopes4 ,a p[]ful microscope is rigidly fix$ ov] a little table ov] :i* ! tape passes & reads its division ) great exactness1 co9cid5ce ) ! division be+ made by ! trav]s+ screw4 ,by ! side ( ! read+ microscope1 & 9 exact collimation ) x1 a plumb+ telescope is rigidly fix$1 & ?is sights d[n to a transf]r+ app>atus1 ,d ,fig4 #cfg1 :i* is ov] ! plate let into ! gr\nd4 ,illu/ration3 ,fig4 #cfg4--,two read+ & plumb+ in/rum5ts1 ,c1 ,c2 transf]r+ in/rum5t1 ,d2 & "o ( ! adju/able int]m$iate supports1 ,b4 ,! transf]r+ app>atus is a spr+ c5tre pun* rigidly m\nt$ truly v]tical on a support+ plate hav+ transv]se motions1 cross levels & levell+ screws4 ,! top ( ! c5tre pun* has a small plat9um disc let 9 a recess1 & ^u ?is disc v f9e cross l9es are m>k$4 ,?is app>atus is plac$ on ! gr\nd ov] :atev] has be5 let 9 to receive ! m>k1 x is !n levell$ & ! cross l9es ^u ! pun* top br\ght by means ( ! transv]se motion screws exactly to co9cide ) ! spid] web ( ! plumb+ telescope1 & 9 ?is position ! c5tre pun* is lightly /ruck ) a mallet :i* m>ks ! plate let 9 ! gr\nd 9 ! exact position ( ! c5tre ( ! cross l9es at its top1 s t if n[ ! transf]r+ app>atus be remov$ ! cross webs ( ! plumb+ telescope w\ld cut ! dot m>k$ 9 ! plate by ! c5tre pun*4 ,?is me?od is f> m exact ?an any hang+ plumb-bob1 z ev5 if !y are scre5$ to prev5t sw++ v few hang ) ! po9t p]fectly true4 ,9 lay+ d[n a base l9e ,no4 #a read+ & plumb+ in/rum5t is set up & levell$ ov] ! />t+ end block1 :i* is usually ( h>d /one or granite set on a firm f\ndation1 ) a copp] plate let 9 its top ab\t ! c5tre1 ! l9e hav+ be5 previ\sly set out ) a !odolite1 & ! int]m$iate /ations be+ r\ghly measur$ ) an ord9>y /eel tape4 ,at ea* int]m$iate /ation or l5g? ( ,kon/at tape us$ a teak po/ is driv5 into ! gr\nd & a z9c plate screw$ ^u its top2 ! o!r end block is simil> to ! />t+ "o4 ,! ,kon/at tape is n[ m\nt$ betwe5 ! end susp5sion supports1 "o be+ outside ! />t+ end block & ! o!r outside ! fir/ teak po/ :i* has be5 put 9 = ! fir/ l5g?4 ,no4 #b read+ & plumb+ in/rum5t is set up ov] ?is po/1 & ,no4 #a & ,no4 #b are align$ ^u ea* o!r by _! align+ telescopes1 & ! ,kon/at tape adju/$ ov] ! little tables "u ! microscope ( ea*2 ! int]m$iate /&s are !n put 9 & adju/$ = height to prev5t cat5]y1 & ! guide pieces are br\ght up to ! tape on ei!r side & clamp$ to prev5t side deflection by w9d4 ,! tape be+ prop]ly susp5d$ x c be easily mov$ ) ! f+]s l5g?ways1 z x is susp5d$ at ei!r end by silk cords ov] ball-be>+ pulleys4 ,x is br\ght 9 position ) its />t+ end division some:]e "u ! microscope ( ,no4 #a read+ app>atus1 & ! microscope is !n br\ght into exact co9cid5ce by ! trav]s+ screws4 ,! transf]r+ app>atus is put on ! granite block ) ! c5tre pun* 9 ! field ( view ( ! plumb+ telescope & !n levell$2 ! cross l9es 9 ! top ( ! c5tre pun* are !n br\ght to exactly co9cide ) ! plumb+ telescope webs by ! transv]se motion ( ! transf]r+ app>atus1 ! c5tre pun* is /ruck & ! m>k ?us made 9 ! copp] plate has a l9e engrav$ ?r\gh x4 ,! transf]r+ app>atus is !n remov$ to ! position "u ,no4 #b read+ & plumb+ app>atus4 ,no4 #b microscope is made to co9cide ) ! end division on ! ,kon/at tape by its trav]s+ screws1 ! c5tre pun* ( transf]r+ app>atus1 br\ght by its trav]s+ screws to co9cide ) ! webs ( ! plumb+ telescope & /ruck1 m>ks ! fir/ section4 ,no4 #a read+ & plumb+ app>atus is !n transf]r$ to ! next po/1 ,no4 #b rema9+ ov] ! fir/ section po/1 ! fir/ end susp5sion /& is transf]r$ outside ,no4 #b po/ & ! tape m\nt$ betwe5 z be=e1 ! trav]s+ motion ( ,no4 #b read+ app>atus mu/ n be t\*$1 b ! end division ( ! tape br\ght to co9cide ) its microscope web by %ift+ l5g?ways4 ,no4 #a microscope at ! fur!r end is adju/$ to co9cide by its trav]s+ screws & ! transf]r+ app>atus z be=e1 & s on until ! entire l5g? is measur$1 ! la/ c5tre pun* m>k on ! copp] plate let 9 ! fur!r end block or /one hav+ a l9e engrav$ ?r\gh x4 ,a few #a-ajj? ( an in* divisions1 or #a-aj?s ( a millimetre1 are divid$ on ei!r side ( "o end division ( ! ,kon/at tape s t any all[ance = expansion or contraction may be made "u ! microscope at ! "t1 b ) ,kon/at tapes ?is is v small inde$4 ,) fairly level gr\nd any slight diff]5ces ( level c be all[$ = 9 sett+ up ! /&s1 s t ! tape rema9s level2 if ! diff]5ce is too great = ?is ! diff]5ce ( hypo & base mu/ be calculat$4 ,!rmomet]s are us$1 g5]ally "o susp5d$ on ! tape at ea* end4 #gfa4--,p]ambulator4--,a v anci5t in/rum5t1 describ$ by ,vitruvius z be+ among ! effects ( ! ,emp]or ,commodus2 x 0 us$ by h&1 or atta*$ to a c>riage to measure di/ances4 ,! in/rum5t is at pres5t us$ z =m]ly = measur+ roads4 ,^u pavem5ts & asphalt roads x measures accurately1 :]e by reason ( traffic x is sometimes a difficult or v sl[ process to use ! *a94 ,! plan ( manufacture is v>i$ consid]ably4 ,! au?or makes ! felloe ( ! :eel 9 segm5ts ( well-season$ mahogany 9 two r+s1 ,fig4 #cfh4 ,^! are rivett$ toge!r f side to side 9 su* a mann] t ! gra9 ( ! wood is cross$ z mu* z possible to prev5t lat]al w>p+4 ,! tyre1 :i* is #f feet 9 circumf]5ce1 is made ( h>d roll$ brass #a in* by in* ?ick4 ,! spokes are light /eel tubes cov]$ ) brass tube1 & screw$ into a brass hub4 ,! axle ( ! :eel is plac$ 9 a /eel =k :i* is =m$ by screw+1 by means ( a w+$ nut1 two b>s ( ab\t #ah by #a by #c_/h in*es ^u a boss =m$ at ! end ( ! /eel /em ( ! turn$ wood h&le4 ,made 9 ?is mann] ! h&le may be easily deta*$ & plac$ flatwise ^u ! :eel1 s t ! :ole may be pack$ 9 a squ>e deal case ( mod]ate dim5sions = transport4 ,illu/ration3 ,fig4 #cfh4--,p]ambulator4 ,illu/ration3 ,fig4 #cfi4--;,details ( regi/]+ box4 ,illu/ration3 ,fig4 #cgj4--,section4 ,! ,regi/]+ ,"p ( ! ,in/rum5t1 ,figs4 #cfi1 #cgj4 ,! axle is protrud$ ?r\gh ! =k on ! left-h& side1 & !nce ?r\gh ! regi/]+ box support+ "o ( its ends4 ,! o!r end ( ! box is support$ by a /ud :i* fits into ! side ( ! =k4 ,! axle 9 ! "p conta9$ )9 ! box is cut into a screw1 ,fig4 #cgj ,s1 ( ab\t sixte5 ?reads to ! in*4 ,! screw works 9 ! edges ( a pair ( discs ,r1 plac$ "o ^u ! o!r ^u ! same axis2 ^! are cut on _! edges ) tee? to =m worm :eels 9 :i* ! screw ^u ! axis ( ! :eel works4 ,! upp] disc has #aaj tee?4 ,?is !re=e moves "o revolution by #aaj turns ( ! :eel4 ,x is divid$ into #aaj divisions at its circumf]5ce1 b is figur$ #bj y>ds to #bbj y>ds or #a furlong1 s t ea* division repres5ts #b y>ds1 correspond+ ) ! circumf]5ce ( ! :eel1 ,fig4 #cfi ,o4 ,! divisions are read by a po9t atta*$ to ! side ( ! box %[n at ! top ( ! figure4 ,s+le y>ds are %[n by ! int]m$iate position ( ! po9t] betwe5 ! divisions1 b s+le feet may v well be e/imat$ approximately4 ,! l[] disc is cut ) #aaa tee?4 ,! ratio #aaj to #aaa gives a diff]5tial displacem5t ( "o too? only aft] #aaj revolutions ( ! :eel1 or ( #bbj y>ds trav]se4 ,! two discs take1 !re=e1 by revolution ov] ! surface #bbj #aaj #bd1bjj y>ds or #ace miles be=e !y return to ! same relative position z at />t+4 ,?is is1 !re=e1 ! space ?is p]ambulator w trav]se )\t resett+4 ,to enable ! l[] disc to be read ! upp] disc is cut away = half ! int]ior circumf]5ce ( its circle4 ,a "p ( ! upp] disc is =m$ into a po9t1 to read direct f ! c5tre into divisions on ! l[] disc1 9 furlongs up to #ac miles4 ,! ,measur+ ,box is cov]$ ) glass = protection4 ,! box c be tak5 (f by removal ( ! mill$-head$ screw at any "t to set x back to z]o1 b 9 practice x is (t5 f\nd m conv5i5t to sp9 ! :eel r\nd to z]o or an ev5 mile ( ! out] circle1 & record diff]5ces ( read+1 if ?is c be done 9 ! di/ance )9 ! record ( #ac miles ( ! l[] disc4 ,! screw & axis1 :i* are ( h>d /eel1 %\ld be occasionally oil$ ) wat* oil to keep ! p]ambulator 9 good work+ ord]4 #gfb4--,! revis] has design$ a light =m ( p]ambulator on ! bicycle :eel pr9ciple4 ,x is %[n at ,fig4 #cga1 & is v light & portable4 ,! rim ( ! :eel is ( gun-metal & is usually made two y>ds 9 circumf]5ce4 ,x is fitt$ ) a c\nt] :i* d5otes two y>ds to e revolution1 & ! di/ance is giv5 9 numb] ( y>ds only4 ,! h&le is deta*able f ! =k = pack+1 & ! :ole is conta9$ 9 a light p9e case4 ,! :eel is also made two metres & t5 l9ks 9 circumf]5ce4 ,illu/ration3 ,fig4 #cga4 #gfc4--,p$omet]4--,us$ = r\ghly asc]ta9+ di/ances pass$ ov] 9 walk+4 ,?is +5i\s in/rum5t 0 ! inv5tion ( ,william ,payne 9 #ahca 7pat5t ,no4 #fjgh74 ,x is ! size ( an ord9>y wat*1 & has a simil> face2 b betwe5 ! figures1 :i* indicate miles #a to #ab1 !re are f\r divisions only1 to indicate qu>t] miles4 ,! p$omet] is slung up by a loop1 ,fig4 #cga1 ,h fix$ ^u ! h&le1 :i* 9 use is pass$ ov] ! edge ( ! wai/coat pocket s z to keep ! in/rum5t 9 an approximately v]tical position4 ,illu/ration3 ,fig4 #cgb4--;,con/ruction ( p$omet]4 ,illu/ration3 ,fig4 #cgc4--;,face ( passomet]4 #gfd4--,! ,regi/]+ ,app>atus consi/s ( a p5dulum1 ,fig4 #cgb1 ,p plac$ horizontally by be+ support$ by a delicate spr+ ,l to its highe/ position1 :]e x re/s aga9/ a /ud4 ,! action ( ! p5dulum is caus$ by its foll[+ ! motion ( ! body 9 /epp+1 until /opp$ by ! foot rea*+ ! gr\nd1 :5 ! mom5tum atta9$ by ! p5dulum c>ries x f its upp] position ( re/ :]e x is sprung aga9/ ! /op to its l[] free position1 :]e x is /opp$ by a screw$ adju/able /ud ,s1 %[n "u x4 ,! axis ( ! p5dulum is free ^u ! axis ( ! rat*et :eel ,r4 ,:5 ! p5dulum falls1 a f9e spr+1 fix$ to its upp] surface1 drops its end into ! tee? ( ! rat*et1 mov+ ov] two or ?ree tee?1 :i* are held aga9/ retrograde motion by ! spr+ pawl ,d4 ,:5 ! p5dulum rises1 ! rat*et is mov$ =w>d ! numb] ( tee? t ! spr+ at fir/ slipp$ ov]4 ,! rat*et is connect$ ) a pair ( ge>$ :eels1 n %[n1 ! axis ( ! second ( :i* =ms ! axis ( ! h&4 ,9 ?is mann] ea* oscillation ( ! p5dulum is communicat$ to ! index h&4 ,! rat*et is made ) extremely f9e tee?1 s t by adju/m5t ( ! screw /ud ,s a great] or less numb] ( ^! tee? may be tak5 by "o beat ( ! p5dulum1 & ?us ! mileage rate may be adju/$ approximately to ! /ep4 ,?is is done1 h[ev]1 v imp]fectly1 z ! v>iation ( ! av]age /eps ( m5 am\nts to "o or two in*es1 & ! diff]5ce f ! numb] ( tee? tak5 w sc>cely indicate less ?an ?ree in*es 9 ! /ep4 #gfe4--,passomet]4--,?is in/rum5t 0 orig9ally inv5t$ by ! au?or z an improvem5t ^u ! p$omet] 7#ahfh74 ,! in/rum5t1 ,fig4 #cgc1 is n int5d$ to indicate miles or any di/ance1 x simply c\nts ! numb] ( /eps tak54 ,! action is j ! same z ! p$omet]1 b ! rat*et tee? are l>g] & less liable to miss a too?1 z x is made to take "o too? only at a s+le /ep4 ,! dial arrangem5t is entirely *ang$4 ,! /eps are num]ically indicat$ by a sep>ate h& :i* reads into ! graduations up to #ej /eps ^u a small dial4 ,ea* revolution ( ! small h& reads ?r\gh ge>+ "o division ( ! c5tral h&1 :i* moves ov] ! complete circumf]5ce ( ! dial1 read+ up to #be1jjj /eps4 ,?is is ! ext5t ( indication4 ,x is necess>y 9 cont9uation beyond #be1jjj /eps to take a record ( progression p] #be1jjj :]e a great] di/ance is requir$ to be measur$4 #gff4--,! av]age /ep may be e/imat$ p]haps )9 #a or #b p] c5t4 by tra9+ 9 walk+ sev]al miles /eadily1 c\nt+ ! /eps1 always rememb]+ t we take %ort] /eps uphill & :5 we are tir$4 ,b ! mean /ep ( ! individual "u all ! diff]5t circum/ances is ! only rule t c be foll[$4 ,illu/ration3 ,fig4 #cgd4--,s\nd+ *a94 #gfg4--,s\nd+ ,*a9s us$ = coa/ surveys are g5]ally made ( iron1 b sometimes ( brass4 ,!y are usually made ( #aj fa?oms entire l5g?4 ,! l9ks are #a in*1 & ! feet are indicat$ by tell]s4 ,! =m ( tell] design$ by ! au?or is %[n 9 ,fig4 #cgd = ! #c4 ,a lead5 weight1 simil> to t %[n ,fig4 #cge1 is us$ ^u ! end ( ! *a9--( #bh lbs41 = ord9>y coa/ "w1 or heavi] if !re are /rong curr5ts4 ,! *a9 is conta9$ 9 a /rong wood5 box4 ,illu/ration3 ,fig4 #cge4--,s\nd+ l9e & weight4 ,a v elaborate app>atus ) /eel wire l9e has be5 made = deep-sea s\nd+ by ,"l ,kelv9 & o!rs2 b ?is subject is beyond ! prov9ce ( ! pres5t "w4 #gfh4--,s\nd+ ,l9es1 us$ = survey ( %all[ coa/s & h>b\rs1 are made ( wat]-laid l9e ( f9e gre5 hemp1 ab\t in* circumf]5ce1 ,fig4 #cge4 ,:ite tapes are ins]t$ z tell]s at e foot1 & r$ tapes at e fa?om4 #c to #f fa?oms are ! ord9>y l5g?s employ$4 ,if ! wat] is %all[ ! fa?oms are easily c\nt$1 b if ?\ght necess>y knots may be ti$ to indicate ! numb] ( fa?oms on ! r$ tell]s4 ,! weight is ab\t #g lbs4 = #ej feet l9e1 ab\t #ae lbs4 = #ajj feet4 ,! "u side ( ! weight is commonly recess$ to take tall[ :5 x is desir$ to br+ up a specim5 ( ! bottom1 if ?is is loose s& or mud4 #gfi4--;,coa/ ,survey ,l9es4--,= survey+ di/ances1 f po9t to po9t ( s\nd+s along a coa/1 l9es ( f9e copp] wire rope m>k$ ) tell]s at #ej & #ajj feet are commonly us$4 ,! l9e is g5]ally all[$ to re/ on ! bottom ( %all[ wat]1 & is float$ up by means ( atta*$ corks 9 deep wat]4 ,x is usually laid & pick$ up by means ( a reel fix$ at ! /]n ( ! survey+ boat4 ,! l5g?s ( l9e us$ v>y f #ajjj to #ejjj feet4 #ggj4--,telemet]s4--,^! sc>cely ent] )9 ! practical limits ( survey+ in/rum5ts1 b z sev]al attempts h be5 made to introduce _! use x is necess>y to m5tion !m4 ,! g5]al attempt has be5 to measure a great di/ance1 #ajjj feet or m1 by means ( ! angles subt5d$ f ! ends ( a %ort base to a di/ant po9t4 ,?is base 9 ! telemet] ( ,piazzi ,smy? is #fj in*es2 ,colonel ,cl>ke1 #gb in*es2 ,otto ,/ruve1 #gce in*es2 & ,adie1 #cf in*es4 ,! angles are usually tak5 ^u ! pr9ciple ( ! sextant by co9cid5ce ( image4 ,v mu* great] success has be5 atta9$ rec5tly by ,messrs4 ,b>r & ,/r\d by means ( _! range-f9d] ( #ed in*es base4 ,! au?or1 z f> z 8 in=mation rea*es1 is assur$ t no in/rum5t ( ! class is satisfactory = survey+ purposes4 ,fur!r1 ! subject is "o to :i* he has devot$ "s /udy1 & design$ two telemet]s4#ee ,"o ( ^! appe>$ to him = a "t satisfactory )9 c]ta9 limits4 ,! base 9 ?is in/rum5t 0 #ej feet1 =m$ ( a f9e pian(orte wire /ret*$ betwe5 two obs]v+ telescopes1 ! t5sion ( ! wire direct+ ! "o telescope to a "r angle1 & ! o!r telescope to an arc :i* read ei!r degrees & m9utes or absolute di/ances 9 ! eye-piece to ! direction 9 :i* ! telescope 0 po9t$4 ,9 fir/ trials ?is in/rum5t 0 f\nd fairly satisfactory2 b subsequ5tly 9 w9dy wea!r ! deflection ( ! wire r5d]$ ! action ( a pair ( in/rum5ts q unreliable4 ,!re are "s in/rum5ts1 z ,colonel ,gauti]'s telemet] us$ 9 ! ,fr5* army1 :i* dep5d ^u comb9$ reflectors plac$ normally at #ae to #de1 z 9 ! apomecomet]1 art4 #fic1 b ) a tang5t screw to give a small motion ( displacem5t to "o mirror :i* reads on a scale ( calculat$ di/ances to angle f a c]ta9 base measur$ betwe5 two /ations ( obs]vation4 ,a v simil> in/rum5t1 inv5t$ by ,labez1 has "o reflector only at #de4 ,^! in/rum5ts may be useful = measur+ approximate di/ances = range 9 ! army1 b c sc>cely rank z survey+ in/rum5ts1 ! box sextant1 art4 #ffd1 be+ 9 e way a sup]ior telemet] = ! purpose :5 a measur$ base c be fix$ & well-kn[n trigonometrical calculation us$4 #gga4--,! simple/ & be/ telemet] = survey+ purposes is ! subt5se telescope1 & all good1 up-to-date survey+ in/rum5ts h _! telescopes s fitt$1 b = ^? :o d n c>ry an in/rum5t ) a telescope ! revis] has design$ a small subt5se telemet]1 ,fig4 #cgf1 :i* consi/s ( a small telescope fitt$ ) subt5se po9ts1 & m\nt$ 9 a coll> :i* has v]tical & horizontal motions & a c5tre socket to fit a ,jacob's /aff4 ,! /adia is set to read #a 9 #ajj4 ,! telescope has rack & p9ion focuss+ & may be revolv$ 9 its socket s t ! /adia rod may be read held ei!r horizontally or v]tically4 ,x is pack$ 9 a lea!r hol/] case1 & a f\r-fold #aj-;feet spr+-po9t$ /adia rod is suppli$ ) x divid$ into feet1 t5?s1 & hundr$?s4 ,illu/ration3 ,fig4 #cgf4 #ggb4--;,h& ,rods1 al?\gh us$ m g5]ally by build+ surveyors1 are extremely useful also to ! civil eng9e] & l& surveyor = t[n "w among build+s & 9 m9es4 ,!y are made #e feet 9 l5g?1 less g5]ally #aj feet4 ,! #e-;feet are made ( s+le blades ( lancewood or ( two jo9t$ to fold4 ,! #aj-;feet are always jo9t$ & made mu* /\t] ?an ! #e-;feet4 ,! #e-;feet are g5]ally sold 9 pairs4 ,illu/ration3 ,fig4 #cgg4--,ord9>y #e-;feet jo9t$ rods--plan & section ( jo9t4 #ggc4--,ord9>y #e-;feet ,rods are divid$ to e #c in*es1 ) feet only /amp$ ) numb]s1 z %[n ,fig4 #cgg4 ,:]e ! rod is jo9t$ ! be/ =m ( fold+ jo9t is %[n 9 ! figure 9 section & plan4 ,! spr+ ,s is sunk into ! face ( ! rod at ! jo9t on "o side1 & spr+s into a groove 7h\s+7 9 ! o!r side s z to lock ! jo9t :5 x is ei!r op5 or clos$4 ,! mo/ useful dim5sion = ! rod is #a in* by #a_/f in*4 ,rods are ne>ly always made ( lancewood1 b !y are pref]r$ dy$ black = neatness by _m surveyors4 ,a pair ( rods is usually c>ri$ 9 a c[hide case4 ,!y are also (t5 c>ri$ 9 ! /em ( a walk+-/ick holl[$ out = ! purpose4 ,! rod or rods 9 ?is case are made mu* light]1 g5]ally in* by #a_/h in* = a pair ( rods1 or #g_/af in* by #g_/cb in* = a s+le rod4 ,! s+le rod is to be pref]r$ 9 ?is case = its extra /r5g?4 #ggd4--;,fully ,divid$ ,rods4--,! au?or has made rods = _m ye>s divid$ to s+le in*es4 ,^! measure f bo? ends--"o end direct z ,fig4 #cgh & ! o!r end rev]s$ by turn+ ! rod ov] z ,fig4 #cgi4 ,by ?is plan ! rod gives direct measurem5t 9 feet1 in*es1 & p>ts f ei!r end1 & ! division is always plac$ outw>ds aga9/ ! "w1 s t measures may be tak5 f ei!r end by turn+ ! rod ov] sideways1 )\t turn+ x end = end4 ,illu/ration3 ,figs4 #cgh1 #cgi4--,/anley's surveyors' rods4 #gge4--;,connect+ ,l9k = ,rods1 :i* weighs only #a oz4 & may be c>ri$ loose 9 ! pocket1 is (t5 f\nd conv5i5t = measur+ heights1 z x p]mits ! ends ( a pair ( rods to be br\ght toge!r1 ,fig4 #chj4 ,by ?is means ! arm w raise ! rods ab\t #g feet1 & ) #aj feet1 ! height ( ! pair ( #e-;feet rods1 ?is w make #ag feet ( measurem5t4 ,:5 ! #aj-;feet is set aga9/ a wall1 its height1 if #bj or #cj feet1 may be guess$ v approximately by /&+ at a di/ance f x4 ,illu/ration3 ,fig4 #chj4--;,connect+ l9k = rods4 ,illu/ration3 ,fig4 #cha4--,slip jo9t$ rod4 #ggf4--,slip ,jo9t$ ,rod4--,?is =m is less g5]al1 b x is a v conv5i5t =m ( rod4 ,! jo9t+ is effect$ by two loops :i* are fix$ to ! c5tre end ( "o "p ( ! rod 9 su* a mann] t ! o!r "p may slide ?r\gh ! loops4 ,:5 ! rod is ext5d$ to #e feet !re is a /op :i* prev5ts fur!r ext5sion1 & a spr+ to keep x at ?is exact position1 ,fig4 #cha4 ,! outside ( ! rod is divid$ into feet & in*es4 ,! inside is divid$ s t any addition to ! half rod1 produc$ by ext5d+ x2 may give ! measurem5t f end to end ( ! rod at ?is position1 ?us3--,! half rod be+ #b feet #g in*es clos$1 if ! loose side be drawn out #ai in*es ! rod f end to end w be #d feet #b in*es1 :i* w be indicat$ by ! division & figur+ inside ! rod4 ,?is is v conv5i5t = measur+ op5+s su* z doorways or passages4 #ggg4--;,brace-piece4--,a #aj-;feet rod is sometimes made ) a brace-piece1 :i* folds up inside ! rod4 ,?is brace-piece is jo9t$ to fix bo? half rods to #ij :5 x is desirable to use ! rod z a squ>e4 ,illu/ration3 ,fig4 #chb4--;,civil eng9e]'s rule4 #ggh4--;,civil ,eng9e]'s ,rule is made f\rfold 9 bo? boxwood & ivory1 ,fig4 #chb4 ,! mo/ conv5i5t size is #a in* wide4 ,"s ( ! pr(ession pref] !m n>r[ = lightness-- in*2 & "s wide = /r5g?--#a in*es4 ,?is rule is g5]ally well made1 ) ,g]man-silv] jo9ts & outside jo9t-plates4 ,! divisions plac$ on ! rule outside are in*es 9 eigh?s & t5?s2 ! inside1 ! ord9>y ar*itects' scales1 #a_/h1 1 1 #a1 & f\r *a9 scales1 #bj1 #cj1 #dj1 & #ej4 ,a #aj is got by halv+ ! #bj2 #fj1 by d\bl+ ! #cj4 ,a protractor read+ to #e is divid$ on ! head4 ,) silv] jo9ts & 9 f9e ivory ?is rule is (t5 made a pres5tation in/rum5t4 ,,footnotes3 #ed ,! ,surveyor1 vol4 ii4 ,no4 #e4 ,sydney1 ,nov4 #ahhi4 #ee ,pat5t ,no4 #badb1 ,may1 #ahhj4 ,,*apt] ,,xvii4 ,,/ations ,,( ,,obs]vation--,,pickets--,,false ,,picket--,,p]man5t ,,/ations-- ,,ref]r+ ,,object--,,heliotrope--,,helio/at--,,he liograph--,,signall+-- ,,morse ,,alphabet--,,night ,,lights--,,oil ,,lant]ns--,,magnesium ,,light4 #ggi4--,/ations ( ,obs]vation v>y mat]ially accord+ to ! ext5t ( ! survey & its purpose4 ,= geodetic works /ations are rais$ at great exp5se1 (t5 9 masonry or solid woodwork4 ,= ord9>y local or civil surveys ! /ations are commonly =m$ ( s+le poles set up v]tically1 :i* v>y 9 dim5sions accord+ to ! ext5t ( survey & ! difficulties :i* may be enc\nt]$ by v>i\s ob/ructions to direct visions by woods1 lakes1 m>%es1 etc4 ,! app>atus t may be useful 9 ! "w ( ! civil eng9e] 9 ord9>y practice w only be consid]$ "h4 ,illu/ration3 ,fig4 #chc4--,rang+ pole or picket4 #ghj4--,pickets or ,rang+ ,poles1 ,fig4 #chc1 z ! "n indicates1 are us$ = rang+ a direct l9e ?r\gh a di/rict1 ei!r by a s]ies ( poles sight$ f "o to ! o!r or by be+ plac$ 9 position conv5i5t = triangulat+ by ! !odolite :]e ! c\ntry is op51 or free f _m build+s1 trees1 or o!r conv5i5t l&m>ks4 #gha4--,! picket 7,fr4 piquet7 is a /raight1 slightly tap]+ pole %od ) wr\ght iron or /eel4 ,x is g5]ally made ( ab\t #a-a_/h in*es diamet]1 & is pa9t$ 9 alt]nate feet r$ & :ite ) an enamel pa9t t w n soil ! h&s or take dirt f !m4 ,! %oes %\ld be made ) /rap-pieces1 s t ! picket1 :i* is g5]ally made ( yell[ p9e = lightness1 %\ld n be liable to break (f at ! %oe 9 use4 ,fig4 #cha repres5ts ! l[] "p ( a picket z made by ! au?or3 ,b black1 ,w :ite1 ,r r$4 ,x is usual to h six pickets at lea/ out 9 use ) a !odolite 9 op5 c\ntry4 ,illu/ration3 ,fig4 #chd4--;,false picket4 ,illu/ration3 ,fig4 #che4--,spur-%od picket4 #ghb4--;,false ,picket4--,= ! plac+ ( a picket x is usual to cle> ! sod ) a small spade :]e possible1 s z to susp5d ! plummet f ! !odolite into ! hole made by ! picket to triangulate f its position4 ,9 m>%y l&s & "u _m conditions ?is is n easily done4 ,x w g5]ally be f\nd m exp$iti\s to c>ry ab\t "o ( ! au?or's false pickets1 to place directly 9 ! hole f :i* ! picket is remov$1 :i* saves ! tr\ble ( remov+ ! grass4 ,?is is %[n 9 ,fig4 #chd4 ,x consi/s ( a wood5 peg1 ^u ! top ( :i* a cross is sawn to repres5t ! axis4 ,?is cross is fill$ 9 ) a v5e] ( ebony1 & ! :ole is poli%$ ov] to keep x clean4 ,x w be readily se5 t any picket accid5tally brok5 w make a false picket4 ,9 sett+ up ! !odolite ov] x ! plummet is br\ght to v]ticality ) ! c5tre ( ! cross4 ,9 mov+ ! false picket ! orig9al "o is easily replac$1 if requir$1 9 ! same position = cont9u+ ! "w4 #ghc4--,spur-%od ,picket4--,mu* /\t] poles ?an may readily be press$ 9 by h&1 z = in/ance1 ( #b in*es diamet]1 may be driv5 into ! gr\nd by hav+ a spur or cross-b> ( /eel1 ab\t #g in*es long & ab\t #c_/h in* diamet]1 plac$ ?r\gh ! pole1 say at #a foot di/ance f ! po9t1 a =m :i* is mu* us$ on ! ,cont95t4 ,?is picket may be j]k$ d[n = a c]ta9 di/ance by pressure ( ! foot on ea* side1 & !n j]k$ home to ! gr\nd by /&+ ^u x1 to make a #aj-;feet or #ab-;feet pole /& suffici5tly rigid = tempor>y "w1 ,fig4 #che4 ,illu/ration3 ,fig4 #chf4--,socket = /ation pole4 #ghd4--,p]man5t ,/ations are commonly con/ruct$ ^u hilltops or o!r comm&+ positions4 ,a v g5]al way is to set up a long pole ( fir or o!r wood at comm&1 f #aj to #bj feet 9 height1 accord+ to ! circum/ances4 ,occasionally x is desirable to remove ! pole & place ! !odolite c5trally ov] its v]tical position4 ,a v good way to d ?is is to h a slightly tap]$ wood5 socket1 ,fig4 #chf ,s1 con/ruct$ ( /\t bo>ds1 say #a in*es ?ick1 made into a holl[ squ>e ) a cross ( bo>ds1 ,,wwww fix$ to x4 ,! socket is plac$ 9 a hole dug out entirely bel[ ! gr\nd1 & is ramm$ 9 & fix$ z an ord9>y gate po/4 ,! pole ,p is squ>$ at ! end to fit ! tap]$ socket up to %\ld]s :i* are =m$ by leav+ ! o!r "p ( ! pole r\nd4 ,! socket = a #ae-;feet pole %\ld be #ah in*es deep2 = a #bj-;feet "o1 #b feet deep4 ,:]e ^! poles are prop]ly prep>$ !y may be jo9t$ toge!r 9 two or m p>ts = portability4 ,bunt+ flags1 r$ & :ite1 ab\t #ah in*es by #i in*es1 may be fix$ at ! tops ( ! poles4 ,9 fix+ ! socket ! pole %\ld be erect$ 9 x to be able to keep x con/antly v]tical dur+ ! ramm+4 ,a plummet susp5d$ at arm's l5g?1 at a di/ance f ! pole 9 two positions at ab\t "r angles to ea* o!r f ! c5tre ( ! pole1 w provide a means ( keep+ x erect dur+ ! fix+ ( its socket4 ,! socket hole1 ^u lift+ ! pole out1 =ms ! c5tre = erect+ ! !odolite ov] its position4 #ghe4--,ref]r+ ,object4--,x is desirable t all arcs tak5 by ! !odolite f an important /ation %\ld conta9 "o po9t 9 common1 = :i* ! be/ def9$ object to be f\nd at a di/ance may be select$4 ,colonel ,cl>k1 ( ! ,ordnance ,survey1 recomm5ds z a ref]r+ object two rectangul> plates ( metal plac$ ) _! edges p>allel to ea* o!r 9 ! v]tical plane1 at su* a di/ance ap>t t ! light ( ! sky se5 ?r\gh ! op5+ appe>s z a v]tical l9e ( ab\t #aj 9 wid?4 ,! be/ di/ance = ?is object is f #a mile to #b miles4 ,two pieces ( bo>d1 fix$ a small di/ance ap>t by l$ges screw$ !reon1 answ] ! same purpose4 ,! description fully conveys ! me?od )\t illu/ration4 ,/ations ,visible at ,great ,di/ances are =m$ by means ( reflection ( ! sun's rays or by artificial light4 ,illu/ration3 ,fig4 #chg4--,/anley's heliotrope4 #ghf4--;,heliotrope1 or helio/at z x is sometimes call$1 may be any =m ( mirror to ?r[ ! sun's ray 9 a con/ant direction or to a di/ant /ation at a "t ( day fix$ = mak+ obs]vation4 ,! in/rum5t is uni=mly con/ruct$ ) a small glass mirror hav+ a plane surface4 ,! angle ( div]g5ce ( ! extreme rays 9 ! reflection is ! same z t subt5d$ by ! sun's diamet] at ! position ( ! mirror1 t is1 ( ab\t #cb m9utes ( arc4 ,?is div]g5ce is suffici5t to r5d] ! reflector visible at a great di/ance4 ,! plan ^u :i* ! au?or has con/ruct$ ?is in/rum5t is %[n 9 ,fig4 #chg4 ,x consi/s ( a reflector ,m =m$ ( a pla9 glass mirror ( ab\t #e or #f in*es 9 diamet]1 plac$ 9 a metal tray4 ,! mirror is c5tr$ v]tically ^u an axis to :i* a worm :eel ,b is atta*$ ^u "o side t works into a tang5t screw :i* is mov$ by a mill$ head s z to place ! mirror at any angle to ! horizon4 ,! mirror & its v]tical adju/m5t j describ$ are c>ri$ by a =k :i* is erect$ f ! base bo>d ( ! in/rum5t ^u a socket jo9t :i* p]mits ! mirror to be turn$ ab\t4 ,^u ! l[] "p ( ! =k above its socket ano!r worm :eel is con/ruct$ c5trally to ! axis4 ,?is works into a tang5t screw atta*$ by fitt+s to ! base bo>d4 ,! tang5t screw has a long %ank lead+ to a mill$ head ,a4 ,by means ( ! mill$ heads ! mirror may be set to any position1 s z to ?r[ ! reflection ( ! sun 9 any requir$ =w>d direction4 ,a small hole is cut ?r\gh ! silv] 9 ! c5tre ( ! mirror to sight ! position to :i* ! sun's reflection is direct$4 #ghg4--,! ,base ,bo>d is ( in* mahogany ab\t #bj in*es by #aj in*es1 & is support$ ^u a v firm tripod /&1 l t describ$ = a plane table1 art4 #gjj4 ,at "o end ( ! bo>d a sight+ scre5 ( mahogany1 #aj in*es by #aj in*es & in* ?ick1 is h+$1 s z to be held erect by means ( a /ay b> ,e4 ,9 ! c5tre ( ! scre5 an op5+ is turn$ out #c in*es diamet]1 & a frame-piece ( half circle only is plac$ ov] ?is4 ,! frame piece is groov$ out at ! back s z to hold discs1 %[n abc 9 ! figure4 #ghh4--,! ,discs abc1 are ( ?9 brass & h op5+s respectively 1 1 & #a in*es wide1 s z to r$uce ! wid? ( ! l9e ( light :i* appe>s ?r\gh !m :5 ! reflection ( ! sun is ?r[n f ! back4 ,^! h ea* a f9e wire /ret*$ across !m to indicate ! c5tre4 ,a f\r? disc1 n %[n1 has a d\ble cross ( wires to indicate ! c5tre only4 #ghi4--,to ,pack ! ,in/rum5t1 ! scre5 is turn$ d[n ! index frame1 fall+ into ! op5+ ,f2 ! mirror ) its =k is lift$ out & secur$ to ! surface ( ! base bo>d by buttons2 & ! :ole app>atus is put 9 a p9e case4 ,its weight )\t tripod /& is #h lbs4 #gij4--,to ,use ! ,heliotrope1 ! /ation on :i* ! sun's light is to be ?r[n is sight$ by look+ ?r\gh ! small hole 9 ! c5tre ( ! mirror1 & adju/+ ! base bo>d until ! /ation appe>s 9 ! c5tre space ( ! disc op5+4 ,! mirror is !n turn$ t[>ds ! sun by means ( ! mill$ heads until its image1 reflect$ ^u ! back ( ! scre51 appe>s c5tral ) "o ( ! discs :i* is int5d$ to be us$4 ,all p>ts ( ! /& & fitt+s be+ made q firm1 ! att5dant moves ! mill$ heads1 z requir$1 to foll[ ! app>5t motion ( ! sun1 at int]vals ( five m9utes or less4 ,x mu/ be obs]v$ t ! c5tre ( ! slit 9 ! disc repres5ts ! /ation visible to ! obs]v]4 ,?is po9t mu/ !re=e be plumb$ to ! /ation po9t 9 sett+ up ! in/rum5t4 ,a "p ( ! scre5 at ,p is cut away to admit ( ! susp5sion ( a plummet4 #gia4--,! heliotrope 0 mu* us$ 9 ,india = ! great trigonometrical survey4 ,colonel ,h4 ,?uilli] /ates f exp]im5t t ,a heliotrope ( #i in*es diamet] answ]s = #ij to #ajj miles4 ,= ne>] di/ances x is mu* too bright to be obs]v$ ?r\gh a telescope1 & ! light mu/ be dim9i%$ 9 ! foll[+ proportion4 ,= di/ances ( #b or #c miles 7! usual di/ance ( a ref]r+ m>k7 an ap]ture ( #jbe ( an in* w answ]1 & = long] di/ances ab\t #ja ( an in* ( ap]ture p] mile ( di/ance w suffice1 viz41 an in* = #aj miles1 #b in*es = #bj miles1 & s on1 provid$ always ! app>atus is c>efully adju/$ & ! man :o works is al]t & skilful4#ef ,practically ! discs "h describ$ w give all ! v>iation requir$4 ,9 less fav\r$ climates ?an ,india m opacity w be f\nd 9 ! atmosph]e1 & l>g] ap]tures requir$ ?an ^? j /at$4 ,signall+ ) ! ,heliotrope4--,a ?9 wood5 bat ,d is mov$ ov] & (f ! outside front ( ! op5 disc ap]ture1 foll[+ ! rule ( ,morse signals1 :i* w be pres5tly describ$ = ! heliograph4 #gib4--;,helio/at4--,is a small] in/rum5t ?an ! heliotrope1 9 :i* ! mirror or mirrors are mov$ by clockwork1 s z to keep ! sun's reflection 9 a uni=m direction ?r\gh\t ! day4 ,?is in/rum5t is delicate & n g5]ally well adapt$ to field "w4 ,illu/ration3 ,fig4 #chh4--;,heliograph4 #gic4--;,heliograph4--,?is in/rum5t is ! inv5tion ( ,sir ,h4 ,c4 ,mance1#eg s9ce improv$ by ,major ,macgregor1 ,colonel ,bonham1 & o!rs4 ,x is us$ = a milit>y signall+ app>atus1 b x is also employ$1 on acc\nt ( its portability 9 place ( ! heliotrope = survey+1 :]e great precision by limit+ ! area ( light reflection is n requir$4 ,! con/ruction ( ! in/rum5t is %[n 9 ,fig4 #chh4 ,b is ! back ( a pla9 circul> mirror ( #e in*es diamet]1 support$ ^u pivots on a =k frame ,j1 ! l[] "p ( :i* =ms a socket4 ,! socket is furni%$ ) a ?umb-screw to secure ! mirror & its frame :5 plac$ ^u a cone project+ f ! app>atus connect$ ) ! base plate =m$ on ! top ( ! tripod head4 ,! cone is erect$ ^u a disc or :eel cut at its edge 9 tee? & c5tr$ ^u ! axis ( ! tripod head4 ,! :eel is revolv$ by means ( a p9ion connect$ ) a mill$ head ,a :i* moves ! mirror & ! entire app>atus above 9 horizontal revolution4 #gid4--,! ,sight+ ,arm ,l is atta*$ to a coll> fitt+ project$ f ! tripod head4 ,?is may be fix$ 9 any horizontal direction by means ( ! tang5t clamp+ screw ,c4 ,! arm ,l has a supplem5t>y ext5sion by ! piece ,sj1 :i* is jo9t$ at ! position ( ^! lett]s & also by a socket fitt+ into ! arm4 ,! t]m9ation ( ! ext5sion is a sight+ po9t ,i =m$ ( a ?9 blade ( metal4 ,! arm & its fitt+s p]mit ! sight+ po9t ,i to be set 9 any direction or elevation to foll[ ! incl9ation ( ! l&4 #gie4--,! ,sight+ ,vane is a piece ( :ite metal ^u :i* !re is plac$ a black dot t]m$ ! sight+ spot4 ,a small circle1 ab\t #a_/e in* diamet]1 is left unsilv]$ 9 ! c5tre ( ! mirror1 :i* does n reflect ! sun's rays4 ,x !re=e causes a small disc ( %ad[ 9 ! c5tre ( ! reflection ( ! mirror1 t]m$ ! %ad[ spot4 ,! %ad[ spot is made to appe> ^u ! sight+ spot :5 ! in/rum5t is adju/$ to ?r[ ! sun's image ^u a di/ant /ation4 #gif4--,! ,supplem5t>y ,mirror ,m is simil> to t already describ$1 c5tr$ also on pivots & plac$ 9 a =k$ frame4 ,?is is m\nt$ on a cone ,s :i* fits into a socket at ,s1 :5 ! ext5sion arm ,j is remov$4 ,?is mirror is int5d$ to receive ! image ( ! sun :5 plac$ t[>ds ! back ( ! po9t+ ( ! in/rum5t to ?r[ ! sun's image f ! mirror ,m to ,b1 to signal by d\ble reflection1 :5 ! sun is at a =w>d angle to ! di/ant /ation4 ,! co9cid5ce ( reflection is tak5 ) ?is mirror by ! reflection ( a piece ( pap] pa/$ on its c5tre ( ! same =m z ! index ,i4 #gig4--,telegraph+ ,app>atus1 call$ te*nically fla%+ app>atus4 ,?is consi/s ( a rod ,r h+$ to ! top ( ! mirror at its upp] end & also to a lev] :i* =ms a ,morse key at ! l[] end4 ,! rod is =m$ ( a screw ( ab\t half its l5g?1 :i* passes into a female screw tube s z to %ort5 or l5g!n x z requir$ to direct ! reflection ( ! sun's rays by turn+ ! mill$ head above ,r1 :i* =ms a "p ( ! tube4 ,! ,morse key is h+$ at ,j to ! /em ( ! in/rum5t1 & is kept up to a fix$ /op by means ( a spr+ ,p ext5d$ by an arm f ! /em ( ! in/rum5t1 s t pressure ^u ! disc ,f moves ! key d[n to its /op ,p1 & also tilts ! mirror to ?r[ its reflection (f ! obs]v+ /ation dur+ ! pressure4 ,! fla%+ describ$ by ! j> ( its action is liable to displace ! mirrors4 ,! use ( ! bat1 %[n at ,fig4 #chg ,d1 is m c]ta9 = signall+ words4 #gih4--,! ,tripod ( ! ,heliograph ,,tt,t consi/s ( ?ree circul> mahogany legs #a-a_/h in*es 9 diamet] & ab\t #d feet #i in*es long4 ,! legs are capp$ ) sockets c>ry+ coll>-pieces :i* are atta*$ to ! t5on-pieces ( ! head4 ,! head =ms a box = ! revolv+ app>atus & rema9s atta*$ to x :5 ! mirror app>atus & arm are remov$4 ,! tripod head is protect$ :5 out ( use by a lea!r cap atta*$ by a /rap to "o ( ! legs4 ,! weight ( ! tripod is #f lbs4 ,9 fix+ ! tripod = use x %\ld h ! legs ext5d$ ne>ly #fj1 & ! toes %\ld be firmly press$ into ! gr\nd4 ,at w9dy /ations x is well to dig holes & s9k ! toes1 or to h a heavy /one susp5d$ "u ! c5tre ( ! head4 #gii4--,! ,case = ! ,heliograph is made ( solid lea!r1 ) sep>ate divisions = mirrors1 arm1 & sight4 ,a sp>e mirror is sometimes pack$ 9 ! same case t ! in/rum5t may n be made useless by accid5tal breakage4 ,a /rap is provid$ ) ! case to g ov] ! %\ld]4 ,! in/rum5t weighs #e lbs4 complete 9 its case4 ,great c>e %\ld be tak5 to obs]ve ! arrangem5t & position ( ! p>ts ( ! in/rum5t be=e tak+ x f its case1 z x is always pack$ closely4 #hjj4--,to use ! ,heliograph ) a ,s+le ,mirror4--,9 ?is case ! reflection is direct4 ,! in/rum5t is approximately direct$ by look+ ?r\gh ! mirror f beh9d1 mov+ ! arm ,l & ! sight ,i to cut ! di/ant /ation1 & !n clamp+ ! screw ,c4 ,aft] ?is is done ! exact position is f\nd by plac+ ! head ne>ly 9 front ( ! mirror1 ) ! back to ! di/ant /ation ) :i* x is int5d$ to communicate4 ,!n to adju/ ! mirror1 if requir$1 & move ! eye until ! di/ant /ation appe>s reflect$ 9 ! exact c5tre ( ! mirror4 ,aft] ?is1 )\t mov+ ! head1 f9ally to adju/ ! sight vane ,i until ! reflection ( ! sight+ spot is br\ght exactly 9 l9e ) ! c5tre ( ! mirror & appe>s reflect$ ^u ! image ( ! di/ant /ation4 ,! sight+ spot is !n 9 direct l9e betwe5 ! di/ant /ation & ! c5tre ( ! mirror1 9 :atev] direction or incl9ation ! mirror may be aft]w>ds plac$ to reflect ! sun's image4 ,c>e %\ld be tak5 n to di/urb ! /& nor arm 9 future movem5ts ( ! mirror4 #hja4--,to ,adju/ ! ,mirror1 /& beh9d ! in/rum5t & adju/ ! v]tical screw ,r & ! horizontal p9ion ,a until ! black spot1 z x appe>s on ! mirror f ! reflection ( ! hole ?r\gh x1 is se5 ^u ! c5tre ( ! po9t ( ! sight vane surr\nd$ by a r+ ( bright reflection f ! silv]$ surface ( ! mirror4 ,! di/ant /ation w !n receive ! reflection1 :i* mu/ aft]w>ds be kept con/antly ^u x by g5tly mov+ ! screw ,r & p9ion ,a1 foll[+ ! app>5t pa? ( ! sun4 #hjb4--,to ,use ! ,heliograph ) ,two ,mirrors1 :i* is necess>y :5 ! sun is %9+ t[>ds ! di/ant /ation & its image c only be project$ by d\ble reflection1 ! second mirror is plac$ ^u ! end ( ! arm 9 ! socket ,s4 ,?is has a :ite pap] vane cem5t$ ^u x1 z %[n at ,m4 ,! mirror ,b is plac$ r\ghly fac+ ! sun4 ,! mirror ,m is turn$ t[>ds ! di/ant /ation ^u :i* x is int5d$ to direct ! rays1 be+ c>eful at ! same "t to obs]ve t ! two mirrors d n int]cept ea* o!r's rays4 ,n[ f ! back ( ! mirror ,m we look into ! mirror ,b1 mov+ ! head until ! c5tres ( ! two mirrors appe> 9 a l9e ) ! eye4 ,!n )\t mov+ ! head1 adju/ ! direction & incl9ation ( ,m until ! reflection ( ! di/ant /ation appe>s 9 ! c5tres ( ! mirrors4 ,n[ clamp ! mirror ,m 9 ?is position1 f :i* x mu/ n be mov$ s long z x is requir$ to keep ! same /ation 9 communication4 ,to keep ! reflection foll[+ ! sun a position is tak5 at ! back ( ! mirror ,b1 & ?is mirror is work$ z be=e describ$1 :5 x is us$ s+ly1 by ! mill$ heads1 only t 9 ! pres5t case ! pap] vane ,m takes ! place ( ! metal vane ,i4 #hjc4--,telegraph+ by ! ,heliograph4--,! communication is made by ! alt]nate pressure & release ( ! ,morse key ,f1 ea* pressure ?r[+ ! reflect$ image ( ! sun (f ! obs]v+ /ation4 ,! ,morse alphabet1 :i* is univ]sally us$1 consi/s ( rapid t\*es repres5t$ by dots1 & pressures ( at lea/ f\r times ! "t ( a t\* repres5t$ by da%es4 ,! foll[+ arrangem5t =ms ! alphabet3-- ,a - ,n - ,b - ,o --- ,c -- ,p -- ,d - ,q --- ,e ,r - ,f - ,s ,g -- ,t - ,h ,u - ,i ,v - ,j --- ,w -- ,k -- ,x -- ,l - ,y --- ,m -- ,z -- ,! "t betwe5 ! words is d\ble t ( a da%4 ,_m o!r signs are commonly us$ = figures1 etc41 = :i* ! read] may consult ,! ,manual ( ,in/ructions 9 ,army ,signall+4 ,! same sy/em is us$ = signall+ by flags2 & by /opp+ (f light ( lamps ?is sy/em is mo/ valuable = ! surveyor 9 new c\ntries = in=mation ( =w>d gr\nd & o!r matt]s4 #hjd4--,lights = ,obs]vations by ,night4--,"u _m conditions an obs]vation ( a di/ant /ation may be mu* m conv5i5tly & accurately tak5 at night by obs]vation ( a lum9\s object ( limit$ area4 ,= ?is purpose ! arc light1 lime light1 blue signal light & o!rs h be5 employ$4 ,= ! civil eng9e] :]e regul> /ations are n erect$1 z ) geodetic "w1 oil lights or ! burn+ ( magnesium ribbon are ! mo/ conv5i5t4 #hje4--,oil ,lant]ns4--,9 ! great trigonometrical survey ( ,india l>ge rev]b]atory lamps 7 us$1 :i* 7 furni%$ ) ,arg& burn]s ) circul> wicks ab\t #b in*es 9 diamet]4 ,! back arc ( rays 0 reflect$ by a p>abolic reflector #ab in*es 9 diamet] & #di in*es 9 dep?4 ,! lamp 0 enclos$ 9 a /rong box ) a plate-glass face #ab in*es 9 diamet]1 ) ap]tures to admit suffici5t air & *imney to c>ry (f fumes4 ,! box 0 con/ruct$ to =m a pack+ case = conveyance ( ! app>atus4#eh #hjf4--,! oil lant]n :i* w be f\nd mo/ conv5i5t = ! civil eng9e] w be "o ( ! same =m ( con/ruction z ! bull's-eye lant]n1 b mu* l>g]--#f in*es squ>e is a good size4 ,?is may be made to g on ! same tripod z ! heliograph1 & w take its place = signall+ by night1 or telegraph+ by ! ,morse signals by ! h& or bat %[n ,fig4 #chg1 ,d4 ,a #f-;in* bull's-eye lamp ) treble wick may be se5 well 9 cle> wea!r #e miles to #aj miles (f4 ,a railway signalman's h& lamp =ms a v good signal1 or ev5 an ord9>y #d-;in* bull's-eye is v useful 9 work+ ov] new c\ntries4 #hjg4--,magnesium4--,! int5se light giv5 by burn+ ribbon magnesium1 & ! extreme lightness 9 weight ( ?is mat]ial1 r5d] x ( especial value = night signall+4 ,magnesium ribbon is n[ sold at a v l[ price 7ab\t two %ill+s p] oz471 & #a oz4 w give a cont9u\s int5se light1 visible at #cj miles1 = ov] an h\r1 :]eas = a night signal arrang$ to be giv5 at a /at$ "t1 fifte5 m9utes is amply suffici5t = a s+le obs]vation4 ,great difficulty is (t5 f\nd 9 light+ magnesium ribbon :5 ?is is slightly oxidiz$ f exposure to air4 ,! be/ me?od is to employ ! flame ( a portable _s lamp1 made = ! purpose4 ,"u any condition ! burn+ ribbon %\ld be %ad$ f w9d4 ,a common plan is to hang a /raight slip ( ribbon f ! c5tre ( a tripod :i* c be readily %ad$ by a pocket h&k]*ief4 ,:]e exp5se is n ! object to be consid]$1 lamps may be _h = burn+ ! wire4 ,t9 cases are made = sold]+ up & /or+ ! ribbon 9 = use abroad4 ,,footnotes3 #ef ,manual ( ,survey+ = ,india1 p4 #dgh1 #ahge4 #eg ,pat5t ,no4 #ccij1 ,octob] #ahgd4 #eh ,= full description & plate1 see ,ev]e/'s ,measurem5t ( ! ,m]idional ,arc ( ,india1 ,introd4 p4 cxv4 ,,*apt] ,,xviii4 ,,measurem5t ,,( ,,altitudes ,,by ,,diff]5ces ,,( ,,atmosph]ic ,,pressure-- ,,hi/orical ,,note--,,m]curial ,,b>omet]--,,con/ruction--,,op]ation--,, an]oid ,,b>omet]--,,con/ruction--,,v>i\s ,,improvem5ts--,,hypsomet]4 #hjh4--;,hi/orical ,note4--,! obs]vation t ! atmosph]e decreases 9 d5sity ) increase ( height is due to ,alhaz5 ! ,s>ac51 ab\t a4d4 #ajjj4 ,by ?is he expla9s t a ray ( light ent]+ ! atmosph]e obliquely foll[s a curvil9e> pa?1 b5d+ t[>ds ! d5s] /rata1 t is concave t[>ds ! e>?4 ,he %[$ t a body w receive diff]5ce ( pressure 9 a r>e & a d5se atmosph]e1 & calculat$ t ! height ( ! atmosph]e to its f9al att5uation w\ld be f 8 data ne>ly #eh miles4 ,! practical in/rum5ts t h be5 devis$ = measur+ altitudes1 by ! diff]5ces ( pressure due to ! weight ( sup]9cumb5t atmosph]e are ! b>omet]1 ! an]oid1 & ! hypsomet]4 ,! b>omet] 0 inv5t$ by ,torricelli ab\t ! ye> #afdj4 ,its pr9ciple 0 demon/rat$ & fir/ appli$ to altitude measurem5t by ,pascal 9 #afdg4 ,! an]oid b>omet] 0 sugge/$ by ,conti 9 #agih1 & said to be devis$ z a practical in/rum5t by ,vidie 9 #ahjh4 ,! hypsomet] or boil+-po9t !rmomet]1 :i* dep5ds = its boil+ temp]ature ^u ! pressure ( ! atmosph]e above ! liquid :i* surr\nds x1 0 sugge/$ by ,fahr5heit 9 #agbd1 exp]im5t$ ) by de ,luc 9 #aggb1 & br\ght to its pres5t practical =m by ,regnault ab\t #ahdj4 ,at ! pres5t "t ! an]oid is almo/ exclusively us$ by ! civil eng9e]1 z ?is in/rum5t :5 made ) great c>e is suffici5tly reliable1 m portable1 & n s delicate 9 use z ! o!rs4 ,s t x is only :5 v great precision is desir$1 or :5 ! "o in/rum5t is us$ z a *eck ^u ! o!r1 t ! m]curial b>omet]1 or ! hypsomet]1 or bo? are n[ employ$4 ,at ! same "t x mu/ be und]/ood t ! an]oid b>omet] scale is 9 a c]ta9 degree arbitr>y1 z ! divisions at be/ are only made up f a c]ta9 numb] ( po9ts tak5 f obs]vations ( ! m]curial b>omet] plac$ simultane\sly ) ! an]oid "u an air pump1 & !re=e its errors comprise ^? ( ! p>ticul> m]curial b>omet] ) :i* x is comp>$1 & ^? due to ! difficulties ( ! comp>ison1 & ( mak+ subdivision aft]w>ds 9 ! same relative proportion1 by copy+ to ! scale ( ! an]oid4 #hji4--,! ,m]curial ,b>omet]4--,! pr9ciple ( ! b>omet] is g5]ally und]/ood4 ,if a glass tube1 clos$ at "o end1 #cc in*es long1 say ( in* or ov] 9 bore1 be fill$ brimful ( m]cury & ! po9t ( ! =ef+] be firmly press$ on ! surface ( ! m]cury1 ! tube may be inv]t$ )\t ! admission ( air4 ,if ! cov]$ end ( ! tube be n[ plung$ into a bas9 ( m]cury & ! f+] sl[ly )drawn f "u ! tube b5ea? ! surface ( ! m]cury1 ! latt] w s9k 9 ! tube to ab\t #cj in*es above ! surface ( t 9 ! bas9--t is1 if ! exp]im5t be p]=m$ at ab\t ! sea level4 ,! empty space 9 :at n[ becomes ! top ( ! tube is t]m$ a ,torricellian vacuum4 #haj4--;,9 remov+ ! pressure ( ! atmosph]e f its surface 9 ! tube1 :i* 9 ! above exp]im5t produces ! b>omet]1 ! pressure ( ! atmosph]e !n falls only ^u ! expos$ surface ( ! m]cury 9 ! bas91 or :at is te*nically t]m$ ! ci/]n4 ,?is pressure is equal p] area1 accord+ to hydro/atic laws1 to ! upp] surface area ( any equal column ( m]cury t ! b>omet] may conta94 ,!re=e ! weight ( ! column ( m]cury 9 ! tube1 if cyl9drical1 above ! surface ( t 9 ! ci/]n1 is ! same z t ( a column ( air ( equal size rea*+ upw>ds to ! full height ( ! atmosph]e4 ,9 fact ! "o exactly balances ! o!r1 & x is by ! diff]5ce ( ! weight or quantity ( air above ! b>omet] p] area ( be>+ surface t x is possible to asc]ta9 ! altitude ( its position by means ( ! height ( m]cury 9 ! tube1 aft] prop] all[ance is made = sudd5 *anges ( conditions ( ! atmosph]e itself f "t to "t1 capill>y attraction ( ! tube1 temp]ature1 etc4 #haa4--,! mean height ( ! b>ometrical column 9 ,great ,brita91 at sea level at ! temp]ature ( #cb ,fahr41 is ab\t #biie ins4 ,a cubic in* ( m]cury at ?is temp]ature weighs #jdhifg lbs4 ,!re=e #biie #jdhifg #adff lbs4 gives ! mean pressure ( ! atmosph]e on ea* squ>e in* ( surface ( ! e>? 9 ?is latitude4 ,ne>] ! tropics ! pressure is great]1 ne> ! poles less4 ,x c be %[n t z ! heights asc5d$ by ! b>omet] increase 9 ari?metical progression1 ! pressure ^u ! m]cury dim9i%es 9 geometrical progression4 #hab4--,m\nta9 ,b>omet]4--,! b>omet] us$ = measur+ altitudes1 to :i* ! above t]m has be5 appli$1 is n[ made only ^u ,=t9's plan1 9 :i* ! bottom ( ! ci/]n :]e9 ! glass tube is plung$ is made ( f9e1 close-gra9$ lea!r1 ! be/ = ! purpose be+ a /\t kid4 ,! pores ( ! lea!r mu/ be suffici5tly f9e n to admit ( ! escape ( ! m]cury1 & yet at ! same "t suffici5tly s(t & pliable to transmit ! ext]ior pressure ( ! air4 ,=t9's con/ruction p]mits ! ci/]n to be clos$ entirely secure f leakage ( ! m]cury1 9 :atev] position ! b>omet] may be plac$4 ,! clos+ is effect$ by means ( an adju/+ screw1 ,fig4 #cij ,f1 :i* by its pressure decreases ! capacity ( ! ci/]n & =ces ! m]cury up ! tube1 or adju/s x to a giv5 height1 s t ! scale ( ! b>omet] may be read correctly f a giv5 po9t ,x plac$ )9 ! ci/]n4 ,to prev5t injury to ! tube ! adju/+ screw is made ( a l5g? j suffici5t to =ce ! m]cury to fill x1 s t :5 x is clos$ home !re is no j> or p]cussion ( ! m]cury 9 c>ry+ ! b>omet]4 ,! details ( ! m\nta9 b>omet] may be be/ foll[$ by ! illu/rations4 #hac4--,! ,glass ,tube is made ( mild fl9t glass ?or\ghly anneal$ & suffici5tly /\t to resi/ all ! /ra9 & p]cussion t may occur ) fair usage4 ,"o end ( ! tube is sl[ly seal$ by ! bl[-pipe1 s t ! clos$ end may be z /rong z ! o!r p>ts4 #had4--,m]cury--,fill+ ! ,b>omet] ,tube4--,! m]cury ( comm]ce is g5]ally impure1 & x conta9s occlud$ air4 ,= /&>d & m\nta9 b>omet]s ! m]cury %\ld be di/ill$ 9 an iron app>atus1 at j its boil+ heat1 leav+ ab\t "o-six? ( ! m]cury 9 ! /ill4 ,! tube1 :i* %\ld be p]fectly clean1 is left ab\t #ab in*es too long = ! b>omet]4 ,x is *>g$ ) clean m]cury = ab\t #cf in*es 9 height4 ,x is !n boil$ 9 a special circul> *>coal /ove1 9 ! c5tre ( :i* !re is a v]tical iron tube ( #b in*es diamet]4 ,! b>omet] tube is introduc$ f ! bottom ( ! /ove1 to heat ab\t #d in*es ( ! top ( ! m]cury only4 ,! tube rema9s 9 ?is position till ! m]cury boils4 ,x is !n elevat$ = ano!r #d in*es & aga9 br\ght to boil+ po9t1 & s on until ! end ( ! tube is rea*$4 ,"u ?is process ! air & "s impurities rise to ! surface ( ! m]cury1 & ! tube is consid]$ to be prop]ly boil$4 ,! end ( ! tube is !n cut (f to its prop] l5g? & ins]t$ 9 ! ci/]n1 9 :i* !re is left suffici5t clean m]cury to complete ! b>omet]4 #hae4--,! l[] "p ( ! b>omet] tube1 aft] x is fill$1 is atta*$ to a ?9 boxwood socket ( ab\t an in* 9 dep? by means ( hot ?9 glue4 ,! socket piece is aft]w>ds b\nd ov] ) sew+ silk1 :i* is aga9 cov]$ ) glue1 & is f9ally v>ni%$ s z to =m an ela/ic1 secure fitt+ ^u ! glass4 ,! socket-piece is secur$ to a wide boxwood coll>1 ,fig4 #cij1 ,d4 ,^u ! "u side ( ! coll> an ivory gauge peg ,x is ins]t$1 :i* =ms ! index po9t = read+ ! surface ( ! m]cury 9 ! ci/]n ^u ! ,=t9 pr9ciple4 #haf4--,! ,ci/]n4--,! glass sight+ tube1 ,fig4 #cij ,h1 ( ! ci/]n1 ?r\gh :i* ! m]cury & gauge po9t ,x are visible1 is made ab\t #a in*es long & f #a in* to #a in*es int]nal diamet]1 ! glass be+ #a_/h in* to #a_/e in* 9 ?ickness1 gr\nd squ>e at its ends4 ,! upp] end ( ! glass fits ^u ! boxwood coll> ,d1 ) ! int]val ( an indi>ubb] b& to make ! fitt+ air-tight4 ,! l[] end ( ! glass tube fits ^u ! boxwood coll> ,i1 ) an int]val ( a turn$ lea!r coll>4 ,! boxwood coll> prolong$ =ms ! l[] "p ( ! ci/]n4 ,?is has a second boxwood coll> screw$ ^u x1 to :i* ! lea!r bag ,e is atta*$ by silk & glue4 ,a /\t lea!r capp+ plug is glu$ ^u ! l[] end ( ! bag1 ^u :i* ! boxwood cap ( ! adju/+ screw ,f presses = adju/m5t ( ! m]cury1 or to close ! tube4 ,illu/ration3 ,fig4 #chi4--,m\nta9 b>omet] erect$ = use4 ,illu/ration3 ,fig4 #cij4--,section ?r\gh ! ci/]n4 ,illu/ration3 ,fig4 #cia4--,v]ni] read+1 %[+ gauge po9t ,s4 ,illu/ration3 ,fig4 #cib4--,sl+ case = c>ry+4 #hag4--,! ,ci/]n ,cas+1 :i* is ( brass1 consi/s ( upp] & l[] coll> pieces1 ,fig4 #cij ,,aa & ,,bb1 & _! atta*m5ts4 ,! upp] coll> is fix$ to ! cas+ tube ( ! b>omet]4 ,9 ! inside ( ?is coll> a lea!r wa%] is plac$1 :i* comes above ! boxwood coll> on ! glass tube ,d & makes s(t contact betwe5 ^! p>ts4 ,! l[] coll> has be5 p>tly describ$ ) ! ci/]n4 ,?is has a brass tube ,e screw$ ^u x1 cov]+ ! bag & l[] "p ( ! plug ( ! ci/]n4 ,! l[] clos$ end ( ! cov]+ tube is =m$ into a nut = ! adju/+ screw ,f plac$ 9 ! axis ( ! tube4 ,!re are f\r bolts or screws ,,gg :i* br+ ! two coll>s ( ! ci/]n cas+ t[>ds ea* o!r1 support ! l[] "p ( ?is cas+1 & produce a pressure betwe5 ! boxwood coll> on ! b>omet] tube & ! top ( ! glass sight+ tube ) ! int]v5+ rubb] coll>1 s t ! m]cury at ?is po9t is secur$4 #hah4--,! ,/em1 or ,b>omet] ,cas+ ,tube1 is made ( brass1 ab\t in* diamet]4 ,?is has a slot1 ( ab\t in* 9 wid?1 d[n two conc5trically opposite sides1 f ne> ! top ( ! tube d[nw>ds = ab\t #bj in*es4 ,! tube is graduat$ along "o op5 edge next ! slot 9 in*es & t5?s1 ^! be+ aga9 subdivid$ to tw5tie?s1 & figur$ to read f #ac in*es to #cb in*es ( m]cury1 z %[n 9 detail = ! upp] "p 9 ,fig4 #cia4 ,! same space is divid$ into c5timetres & millimetres if metrical measure be us$4 ,)9 ! out] tube an inn] tube ( ab\t #ab in*es 9 l5g? fits telescopically to move ) a s(t smoo? motion4 ,?is inn] tube c>ries "o v]ni] at top & "o at bottom1 ,fig4 #chi1 rr4 ,! top v]ni]1 %[n ,fig4 #cia1 is plac$ above a slot 9 ?is tube :i* corresponds ) ! out] tube1 s t ! level ( ! m]cury c be se5 bel[ ! top v]ni]-piece at ,s4 ,! v]ni]s are divid$ into #ej1 s t1 read+ into ! #bj1 !y give read+ #ej #bj1 or #ajjj to ! in*4 ,! inn] tube c>ries a rack ab\t #aa in*es long1 :i* moves by a p9ion fix$ ^u a cock-piece1 ,fig4 #chi m1 on ! out] tube 9 ! same mann] z be=e describ$ = telescope rack+1 art4 #if4 ,two /ay-pieces plac$ ov] ! out] tube hold ! slots firmly at an equal op5+4 ,a r+ is plac$ at ! head ( ! b>omet] to susp5d x 9 a room1 to be us$1 if requir$1 z an ord9>y meteorological b>omet]1 z %[n at ! top ( ,fig4 #cia4 #hai4--,m\nt+ ( ! ,b>omet]4--,! b>omet] is m\nt$ ^u a tripod =m$ ( ?ree light tubes ) /eel po9ts1 z %[n ,fig4 #chi4 ,^! screw into a coll> :i* is pack$ 9 ! cap ( ! lea!r case4 ,! coll> has two opposite screws t screw into a second coll>1 :i* is also held by two opposite po9ts at "r angles to ! fir/4 ,! po9ts ( ! screws =m axes 9 ! mann] ( a ,hook's jo9t1 p]mitt+ ! b>omet] to take a v]tical position by ! sup]ior gravity ( its ci/]n & l[] p>ts4 #hbj4--,! ,!rmomet]1 %[n at ,fig4 #chi t1 has its bulb br\ght z ne>ly z possible into contact ) ! glass tube enclos$ 9 ! cas+ tube4 ,x is commonly divid$ ) bo? c5tigrade & ,fahr5heit scales4 ,correct obs]vation ( ! !rmomet] is necess>y to be made ) e obs]vation ( ! b>omet]1 z ! specific gravity ( ! m]cury1 & consequ5tly ! height ( ! column1 dep5d p>tly ^u ?is = its correct det]m9ation4 #hba4--,! ,pack+ ,case1 ,fig4 #cib1 is made ( solid lea!r l9$ ) ?ick felt to fit ! b>omet]4 ,! legs are plac$ 9 pack+s outside ! case4 ,9 pack+ = c>riage ! screw ( ! ci/]n is turn$ ne>ly home1 leav+ only suffici5t space = any probable expansion ( ! m]cury f increase ( temp]ature4 ,! b>omet] %\ld always be c>ri$ 9 an inv]t$ position1 z ?is precludes ! possibility ( air gett+ into x1 & ev5 t5ds to exclude1 by ! j>r+ motion ( c>ry+1 any air t may h accid5tally become occlud$4 ,a /rap is atta*$ to ! case = hold+ x ov] ! %\ld]4 #hbb4--,read+ ! ,b>omet]4--,x w be obs]v$ t ! m]cury aga9/ ! sides ( ! tube pres5ts an upw>d curv$ appe>ance1 due to ! resi/ance ( ! glass to p]fect contact1 & ! cohesion ( ! m]cury 9 :at is t]m$ capill>y action4 ,?is bead+1 z x is t]m$1 v>ies accord+ to :e!r ! m]cury is ris+ or fall+4 ,x is always necess>y be=e tak+ an obs]vation to raise ! m]cury1 by turn+ ! screw ,f1 until its surface j t\*es ! peg ,x1 to make obs]vations uni=m4 ,! read+ is tak5 by sl[ly l[]+ ! index-piece by means ( ! mill$ screw until light is j exclud$ betwe5 ! =e & back index surfaces1 z %[n ,fig4 #cia at ,s1 at ! highe/ po9t ( ! surface ( ! m]cury4 ,! in*es1 t5?s1 & half-t5?s 7#je7 are read on ! scale1 & ! ?\s&?s on ! v]ni]4 ,?us1 suppose ! scale reads #bfde & ! v]ni] #be #be ?\s&?s1 ! read+ w be-- #bfde #jbe ------ #bfdge ,= altitude ! upp] & l[] /ations are tak51 & ! diff]5ce subtract$ = diff]5ce ( b>ometrical scale4 #hbc4--;,diff]5ce 9 ,altitude 9 feet tak5 f ,b>ometrical ,in*es4--,complete b>ometrical tables = ?is comp>ison w be f\nd 9 ,moleswor?'s & o!r pocket-books 9 use by all eng9e]s4 ,x is !re=e unnecess>y to occupy our space ) !m4 ,a v approximate rule may be giv51 :i* 0 propos$ by ,mr4 ,r4 ,/ra*an 9 ! ,meteorological ,magaz9e1 z foll[s3-- ,read ! b>omet] to ! ne>e/ hundr$? ( an in*2 subtract ! upp] read+ f ! l[]1 leav+ out ! decimal po9t2 & !n multiply ! diff]5ce by #i1 :i* gives ! elevation 9 feet4 ,?us3-- ,l[] /ation #bibe in*es ,upp] #bhjb ------ #abc #i ------ ,elevation #aajg feet4 #hbd4--;,capill>ity4--,= meteorological obs]vations a quantity mu/ be add$ to ! read+ equal to ! resi/ance ( ! tube 9 capill>y action to ! rise ( ! m]cury4 ,?is is great] 9 an unboil$ tube ?an 9 "o 9 :i* ! m]cury is boil$4 ,= altitude measurem5ts ) a s+le b>omet]1 or by two b>omet]s ) equal tubes1 x may be neglect$1 z x w be equal 9 all p>ts ( ! tube4 ,:]e two b>omet]s ( diff]5t bores are us$1 ! foll[+ table gives ! correction3-- ,correction ( ,capill>ity to be ,add$ to ! ,read+4 ,diamet] ( ,tube 9 ,in*es #f #ee #e #de #d #ce #c #be #b ,unboil$ ,tube1 ,in*es #jjd #jje #jjg #ja #jad #jb #jbe #jd #jei ,boil$ #jjb #jjc #jjd #jje #jjg #ja #jac #jb #jbi #hbe4--,temp]ature ,correction4--,z ! m]cury increases 9 temp]ature x becomes specifically light]1 !re=e rises high] 9 ! tube "u equal atmosph]ic pressure4 ,! temp]ature is indicat$ by ! !rmomet]1 %[n at ,fig4 #chi t4 ,! expansion ( m]cury = #a ,fahr4 is #jjjjaja2 b ! brass tube also exp&s #jjjjjajd1 & x is ! diff]5ce betwe5 ! two expansions t we require1 ! m]cury exp&+ ab\t #gae m ?an ! brass4 ,if we subtract f ! read+ #jjjad ( ! obs]v$ altitude = e degree ( ,fahr5heit above #cb1 ! correction w be practically v ne>4 ,?us = a s+le read+--!rmomet]1 #eb ,fahr42 b>omet]1 #cj in*es -7#eb - #cb7 #cj #jjjad #jhd1 mak+ ! true read+ #cj - #jhd #biiaf in*es at #cb ,fahr4 ,tables = correction )\t any calculation w be f\nd 9 ,moleswor?'s & o!r pocket-books4 #hbf4--;,gravity ,correction4--,! =ce ( gravity decreases z we asc5d to a high] level 9 proportion to ! squ>e ( ! di/ance f ! c5tre ( ! e>?4 ,x foll[s t ! =ce ( gravity z we asc5d at ! equator dim9i%es at a less rapid rate ?an at ! poles4 ,its am\nt is always small--on an av]age x may be tak5 at ab\t #jjja in* ( m]cury p] #djj feet ( asc5t4 ,"t4--,humboldt discov]$ t ! b>omet] v>i$ )9 ! tropics at diff]5t h\rs ( ! day4 ,?is has also be5 f\nd to be g5]al to "s ext5t 9 all c\ntries1 dep5d+ ^u _m conditions4 ,x is only important = consid]ation ( altitude measurem5ts1 t x is advisable if possible to take ! upp] & l[] /ations simultane\sly by a pair ( b>omet]s = exact det]m9ation ( altitude4 #hbg4--;,an]oid ,b>omet]4--,! fir/ introduction ( ?is in/rum5t into ,engl& 0 by ,pi]re ,arm&1 le ,comte de ,fonta9m>eau4#ei ,?is in/rum5t consi/$ ( a vacuum *amb] z its prime mov]4 ,! *amb] 0 made a flat cyl9drical box1 ) its upp] surface ( ?9 metal1 ) corrugations cov]+ its surface 9 conc5tric r+s4 ,! *amb] 0 fill$ ) a numb] ( spiral spr+s :i* resi/$ ! pressure ( air1 to prev5t ! collaps+ ( ! corrugat$ surface :5 ! *amb] 0 exhau/$1 & s plac$ ! surface 9 equilibrium ) ! pressure x receiv$ f ! atmosph]e4 ,! movem5ts "u v>i\s pressures 7 multipli$ by ge> "w & lev]s s z to make a small movem5t ( ! corrugat$ surface evid5t 9 ! ext5t ( motion ( an index h& read+ ^u a dial4 ,illu/ration3 ,fig4 #cic4--,/anley's civil eng9e]'s an]oid4 ,! an]oid practically 9 its pres5t =m 0 devis$ by ,luci5 ,vidie f #ahdh to #ahfb4fj ,9 ?is in/rum5t ! vacuum *amb]1 :i* is a ?91 flat1 circul> box1 is corrugat$ equally on bo? sides1 s z to obta9 d\ble area ( active surface "u atmosph]ic pressure to t ( ! old] =m4 ,! *amb] has its surfaces drawn ap>t by an ext]ior spr+1 ! po9t ( communication or t5sion be+ plac$ at ! c5tre ( its corrugat$ sides only4 ,illu/ration3 ,fig4 #cid4--,p]spective view ( ! int]ior ( an an]oid4 #hbh4--,! con/ruction ( ?is an]oid is %[n 9 ,fig4 #cid1 :i* is ( a #d-;in* in/rum5t1 an]oids made = survey+ be+ ( two sizes1 #c in*es & #d in*es4 ,a is a solid plate ( metal #a_/h in* 9 ?ickness1 t]m$ ! base plate2 ,b ! vacuum *amb]1 circul>ly corrugat$ on bo? sides1 made ( ?91 h>d-roll$ ,g]man silv] conta9+ a l>ge p]c5tage ( nickel4 #hbi4--;,an axis is project$ f ! l[] side ( ! *amb]1 ( ab\t #a_/e in* diamet]4 ,?is is tapp$ ) a screw & screw$ firmly d[n into ! base plate ) a c\nt]nut4 ,on ! upp] side ( ! vacuum *amb] ! axis is project$ upw>ds to receive ! t5sion ( a /rong1 v flexible spr+ ,d above x1 to be describ$4 ,a bridge-piece ,,ee ( /eel ( /rong section /rides ov] ! vacuum *amb]4 ,?is piece has a /\t arm-piece project+ f x t[>ds ,a1 :i* is secur$ to ! base plate by a screw t is left op5 to a hole indicat$ ne> ,a ?r\gh ! out] case ( ! in/rum5t1 by means ( :i* ! bridge-piece c be rock$ s z to produce m or less t5sion ( ! spr+ ,d ^u ! vacuum *amb] = f9al adju/m5t4 ,! bridge-piece has two po9ts ( rigid support 9 "r l9e1 :i* =m a prim>y--adju/$ :5 ! in/rum5t is made--( ! spr+ contra to ! pull ( ! vacuum *amb]4 ,! ma9 spr+ ,d is made ( f9e ?9 /eel1 c>efully temp]$1 z broad z ! *amb]4 ,?is spr+ is con/ruct$ s t by its ela/icity x may h s5sitive movem5t "u ! pull ( #aj lbs4 to #ae lbs4 p] in* ( active surface ( ! vacuum *amb]4 ,x is ^u ! p]fection ( ?is spr+ z mu* z ^u ! con/ruction ( ! vacuum *amb] t ! s5sitiv5ess ( ! in/rum5t dep5ds4 ,! upp] axis ( ! vacuum *amb] is secur$ by a cross cott] p9 ,c :i* gives an exact po9t ( resi/ance & yet secures flexibility ( ! spr+ at ! junction4 ,?is cott] p9 is plac$ 9 ! c5tre ( ! ?ree po9ts ( support ( ! bridge-piece ,,ee4 ,a lev] arm ,g is fix$ to ! ma9 spr+ ,d ^u a /\t plate ( metal :i* is 9 direct connection ) ! po9t ( t5sion ( ! vacuum *amb]4 ,x is ! small movem5t ( ?is lev] arm 7ab\t #ja in* at ! *amb]7 t gives motion to ! indicat+ app>atus4 ,! lev] moves a crank$ arm on ! axis ,,hk1 :i* communicates ?r\gh ! axis to a second crank$ arm plac$ at "r angles to ! fir/ ,i4 ,?is pulls a *a9 ,q atta*$ to ! arm ,j4 ,! *a9 is w\nd r\nd a small drum fix$ ^u ! axis :i* c>ries ! h& ne> ,r4 ,! drum keeps ! h& 9 "o direction contra to ! pull ( ! *a9 by a hair spr+ ,r :i* is j suffici5t to ov]come ! friction ( ! axis ( ! h& ,f4 ,! h& & drum & _! fix+s are c>ri$ by ! plate ,m1 :i* is a light piece ( brass project$ f a /iff /&>d fix$ f ! base plate ,k4 ,! comp\nd lev] app>atus describ$ moves ! po9t ( ! h& ab\t five hundr$ times ! am\nt ( movem5t ov] ! fir/ fulcrum ( ! lev] at ! *amb]4 #hcj4--;,comp5sation = ,temp]ature4--,?is is a some:at difficult matt]1 :i* is g5]ally br\ght ab\t by sev]al modifications ( p>ts4 ,"s ord9>y an]oids w move upw>ds ab\t #a_/aj in* ( m]cury by a rise ( temp]ature ( #h c5tigrade only4 ,?is is caus$ pr9cipally by ! increase ( temp]ature s(t5+ ! spr+ to r5d] x less rigid1 & ! s(t5+ ( ! vacuum *amb] to r5d] x m flexible or s5sitive to atmosph]ic pressure4 ,"s little diff]5ce is also caus$ by ! unequal relative expansion ( ! lev]1 arms1 spr+1 & *a91 ^! p>ts be+ ( /eel & brass4 ,comp5sation c be made 9 ! lev] arm ,g by mak+ ?is curv$ & ( two unequally expansive metals1 z z9c & /eel1 s t ! curvature increases ) increase ( temp]ature & ! lev] %ort5s4 ,comp5sation c also be p>tially made by mak+ ! base plate 9 two metals--iron & brass--s z to press ! /&>ds fix$ ?r\gh ! two metals ne>] or fur!r ap>t ) temp]ature *anges4 ,b ! :ole subject is too te*nical to be ent]$ ^u 9 our limit$ space1 z x dep5ds s mu* ^u ! con/ruction ( ! in/rum5t1 :i* is modifi$ 9 v>i\s ways by diff]5t mak]s 9 ord] to effect ?is correction4 #hca4--;,dial & ,h&4--,f ! delicacy ( ! /ructure ( ! an]oid x becomes evid5t t no two in/rum5ts c be made to exactly ! same rate ( movem5t2 !re=e ea* in/rum5t has to be sep>ately graduat$ :5 x is int5d$ to measure altitudes ) x exactly4 ,h[ev] close or op5 ! scale may be1 x becomes clos] z great] altitudes are asc5d$1 ! d5sity ( ! atmosph]e z a gase\s fluid decreas+ 9 geometrical progression z ! altitude increases 9 ari?metical progression4 ,f ?is we c und]/& t a v]ni] to ! index h& c only read approximately1 al?\gh x w act fairly well at a c]ta9 po9t ( ! scale4 ,! be/ & possibly only correct me?od ( divid+ ! scale is to put at fir/ a false scale to ! in/rum5t1 & to read ?is scale by ! index h& ) a microscope "u an air-pump1 comp>$ at e half-in* ( height ( ! column ( ! m]cury by ! gauge atta*$ to ! pump4 ,:5 ?is is c>efully done1 a z]o po9t is tak5 ( ! position ( ! index h& at ! atmosph]ic pressure at ! "t1 z indicat$ on ! false scale4 ,! prop] scale1 z x appe>s ^u ! dial1 is divid$ f ! position ( ! read+s ( ! false scale1 ! two scales be+ sup]impos$ ^u a special divid+ ma*9e4 ,! dial is aft]w>ds figur$ & f9i%$4 #hcb4--,! ord9>y me?od ( read+ ! an]oid is to let ! index po9t read ov] ! divisions4 ,! au?or devis$ a plan1 :i* he has us$ = _m ye>s1 ( fix+ a small plate ( alum9ium ^u ! po9t ( ! h&1 level ) ! scale1 :i* is rais$ on a /ep to read x ^u its inside edge1 to a f9e l9e on ! alum9ium4 ,by ?is means error ( p>allax 9 read+ is entirely avoid$4 ,! au?or also places an adju/able magnifi] to move ov] ! index = read+4 ,?is la/ improvem5t is n[ foll[$ by o!r mak]s4 ,a po9t] also revolves ) ! out] rim to %[ ! la/ read+ be=e asc5t or desc5t4 ,in/rum5ts made ) c>e 9 ! po9ts j indicat$ mu/ necess>ily become exp5sive4 ,:]e ! an]oid is to be us$ z a wea!r glass1 or ev5 z a travell+ companion to judge ( approximate heights 9 climb+ m\nta9s1 su* c>e is n ne$$1 & ! in/rum5t may be produc$ v *eaply ( useful quality4 ,on ! o!r h&1 :]e precision is requir$1 a delicately made an]oid w indicate a movem5t ( #c feet or less 9 rais+ or depress+1 :5 hold+ ! in/rum5t horizontally 9 ! h& & giv+ a light tap on ! glass ) ! f+]-nail be=e read+1 s z to put all motive p>ts 9 equilibrium4 #hcc4--,! ,altitude ,scale is g5]ally plac$ ne> ! p]iph]y ( ! dial2 x is ! all-important "p to ! surveyor4 ,?is scale is usually set out f a mean ( atmosph]ic pressure at sea level1 tak5 f ,sir ,george ,b4 ,airy's tables1 :i* give ! extreme pressure ( #ca in*es b>ometric pressure = z]o at sea level4 ,) ?is pressure altitudes are tak5 at int]vals accord+ to ! indices te/$ "u ! air-pump1 & ! int]m$iate divisions are graduat$ to scale4 ,^! index po9ts are %[n 9 ! table bel[ = a few po9ts3-- ,table ( ,altitude ) ,b>ometrical ,scale4 ,height ,b>omet] 9 ,height ,b>omet] 9 9 ,feet4 ,in*es4 9 ,feet4 ,in*es4 #j #ca #fjjj #bdhge #bej #cjgag #gjjj #bcigi #ejj #cjdcf #hjjj #bcabe #gej #cjaei #ijjj #bbbhb #ajjj #bihhc #aj1jjj #badgi #aejj #bicdj #aa1jjj #bjgjf #bjjj #bhhjg #ab1jjj #aiiei #bejj #bhbhc #ac1jjj #aibcf #cjjj #bggfi #ad1jjj #ahece #djjj #bfgfi #ae1jjj #aghec #ejjj #behjd ,x may be g5]ally obs]v$ t ! m op5 ! scale ! less altitude c be obta9$ by a s+le revolution ( ! h&2 !re=e ! m po9ts c be tak5 p] #ajjj feet4 ,?us1 ) an altitude b>omet] read+ to #cjjj feet1 read+s c be po9t$ 9 con/ruction at e #bej feet2 ) "o ( #fjjj feet1 at e #ejj feet2 & ov] ?is at e #ajjj feet4 #hcd4--,movable ,altitude ,scale4--,9 ?is ! altitude scale revolves s z to be able to set x at z]o = asc5d+ f any po9t4 ,z ! b>ometrical scale dim9i%es1 x is necess>ily inaccurate1 & _c !re=e be us$ ^u a survey+ an]oid2 b ! plan is pleasant = approximate measurem5ts = amusem5t 9 mak+ asc5ts4 ,x is only m5tion$ "h = ! reason t ! inaccuracy ( ! movable scale is n always recognis$4 #hce4--;,adju/m5t ( ! ,an]oid4--,!re is a screw at ! back ( e an]oid some:]e "u ! po9t ,a1 ,fig4 #cid1 by means ( :i* an an]oid may be br\ght to ! read+ ( a m]curial b>omet] at ! position ! m]cury may be read4 ,:]e a good in/rum5t has be5 set by ! mak] to a /&>d b>omet]1 x is n wise to alt] x frequ5tly if x keeps 9 good work+ ord] = altitude measurem5ts )\t be+ aga9 set by a /&>d4 ,on ! o!r h&1 h[ev] well ! an]oid may h be5 made x works gradually to a slight *ange1 caus$ by ! smoo? we>+ ( p>ts 9 action4 ,x is well to h an an]oid1 aft] "o or two ye>s' we>1 clean$ & adju/$ by ! mak]4 ,x w !n1 if a good in/rum5t1 "w well = _m ye>s4 #hcf4--;,directions = ,measur+ ,altitudes4--,turn ! out] rim ( ! in/rum5t until ! index c>ri$ !reby reads to ! same po9t z ! index h&4 ,raise ! magnifi] until ! read+ comes into %>p focus4 ,hold ! in/rum5t z ne>ly horizontal z possible1 & tap ! case lightly ) ! ?umb-nail two or ?ree times1 s z to ov]come any slight friction ( its me*anism4 ,?is places ! action ( ! works 9 equilibrium4 ,write d[n ! obs]vation z x n[ reads 9 ! pocket-book1 tak+ ?\s&s f ! "r h& 7l>ge figures71 hundr$s f ! "r h& 7small figures71 t5s f ! l9es to ! left ( ?is1 & units f obs]vation ( ! position ( ! index l9e 9 ! space betwe5 ! la/ & ! next l9e4 ,say ?is obs]vation reads #bdfe4 ,:e!r we asc5d or desc5d1 ! in/rum5t acts simil>ly4 ,we w n[ presume we asc5d to ! height we require to asc]ta91 & take a second read+1 #aide2 ! diff]5ce betwe5 ^! numb]s1 #bdfe - #aide #ebj feet1 is ! numb] ( feet asc5t4 ,x is necess>y1 :]e exact measurem5t is requir$1 to take ! rev]se read+1 z ! atmosph]ic pressure may h *ang$4 ,we n[ desc5d1 tak+ ! la/ obs]vation1 #aide1 & f9d ! read+ at ! fir/ position #bdfc in/ead ( #bdfe1 t is #b diff]5ce1 :i* proves t ! atmosph]ic pressure has decreas$4 ,if we take half ?is diff]5ce #a & correct ! fir/ d$uction1 #ebj - #a #eai w give u ! correct measurem5t1 subject only 9 ?is in/ance to ! irregul> possible fall ( atmosph]ic pressure1 :i* w n 9 _m in/ances1 if ! times ( obs]vation h be5 ne>ly equal1 be a quantity wor?y ( consid]ation4 ,x is n necess>y to make any correction = ! height ( ! obs]v] 9 positions above gr\nd1 z ! in/rum5t mu/ be plac$ at a uni=m di/ance f ! eye to obta9 ! read+4 ,9 m9es x w frequ5tly be necess>y to measure ! heights f ! gr\nd at :i* ! obs]vation is made4 #hcg4--,v>i\s ,improvem5ts 9 ! ,an]oid4--,x is unc]ta9 :e!r any great int]nal improvem5ts h be5 made 9 ?is in/rum5t1 except by ,vidie1 at v>i\s times4 ,_m attempts h be5 made to increase ! l5g? ( scale to obta9 m op5 read+4 ,^! attempts h all be5 9 ! direction ( increas+ ! diff]5ce ( space betwe5 ! fulcra ( ! lev]s or by additional ge>work1 produc+ !reby a great] multiplication ( ! small unit ( displacem5t ( ! axis ( ! vacuum *amb] beyond ! normal #ejj1 :i* is already great4 ,! multiplication has be5 tak5 up to #bjjj or m4 ,?is increases ! difficulty ( manufacture & c]ta9ty ( p]man5t action4 ,_m ( ^! plans 7 tri$ by ,vidie & ab&on$4 ,a plan ( ,vidie's#fa ( giv+ ! h& ?ree or f\r revolutions1 & to regi/] ?is ^u a spiral scale ^u ! dial1 also by c\nt+ on a second dial ! numb] ( revolutions1 has be5 repeat$ ) slight v>iation by ,e4 ,t4 ,loseby 9 #ahfjfb & by ,major ,watk9 lat]4 ,vidie's plan ( draw+ back ! h& to read ! spiral has be5 modifi$ also by ,major ,watk9 9 a mann] :i* may be a little less frictional4#fc ,illu/ration3 ,fig4 #cie4--,watk9's ext5d$ scale survey+ an]oid4 #hch4--,watk9's ,ext5d$ ,scale ,an]oid4--,?is in/rum5t is %[n at ,fig4 #cie1 & has a v ext5d$ read+1 consi/+ ( ?ree complete circles1 9 place ( ! usual s+le scale1 ) a h& or po9t] suffici5tly long to ext5d across !m all4 ,9 ord] to %[ cle>ly :i* circle ( scales %\ld be read !re is an indicator atta*$ to ! movem5t ( ! in/rum5t :i* causes a s]ies ( figures 7,i41 ,,ii41 ,,iii41 correspond+ ) ! ?ree circles7 to be exhibit$ ?r\gh an ap]ture 9 ! dial4 ,= in/ance1 :5 ! in/rum5t is 9 its normal /ate ! h& w po9t to ! fir/ or out] circle1 & ! figure ,i4 w appe> & rema9 9 ! ap]ture until ! b>omet] falls to #bgh1 :]e ! break takes place 9 ! circle1 z w be se5 9 ! illu/ration4 ,! h& !n takes up ! read+ on ! second circle 7:]e ! break appe>s at #bgh7 & figure ,,ii4 replaces figure ,i4 9 ! ap]ture1 rema9+ !re until ! b>omet] falls to #be1 :5 ! read+ is transf]r$ to ! ?ird circle1 & figure ,,iii4 appe>s 9 ! ap]ture4 ,illu/ration3 ,fig4 #cif4--;,face4 ,illu/ration3 ,fig4 #cig4--;,back4 #hci4--,watk9's ,new ,pat5t ,m\nta9 ,an]oid ,b>omet]4--,?is in/rum5t1 ( :i* bo? a front & back view is %[n above at ,figs4 #cif & #cig1 is ! inv5tion ( ,colonel ,h4 ,s4 ,watk94 ,! special feature is t x c be put 9 or out ( action z requir$1 & :5 out ( action is imp]vi\s to ! influ5ce ( v>iations 9 atmosph]ic pressure4 ,?is relieves ! /ra9 on ! me*anism ( ! an]oid1 z x is only put into action :5 a read+ is requir$4 ,! l[] portion ( ! vacuum-box in/ead ( be+ a fixture 7z is ! case ) ord9>y in/rum5ts7 is all[$ to rise1 :i* is effect$ by atta*+ to ! l[] portion ( ! vacuum box a screw arrangem5t actuat$ by a fly nut on ! outside ( ! case4 ,"u ord9>y conditions ?is screw is releas$1 & ! vacuum-box put out ( /ra94 ,:5 a read+ is requir$1 ! fly nut is screw$ up z f> z x w g1 ?us br++ ! in/rum5t into ! normal condition 9 :i* x 0 graduat$4 ,x has an alum9ium case = lightness1 is made 9 two sizes 7#c in* & #d in*71 & has a sl+ lea!r case4 ,^! plans are aga9 on _! trial4 ,x is ! au?or's op9ion on ! subject1 kn[+ ! delicacy & skill %[n 9 ,vidie's "w1 t little improvem5t is likely to be obta9$ by magnification ( ! small motion ( ! vacuum *amb] by me*anical means1 :i* mu/ necess>ily be by a process bo? delicate & highly frictional4 ,attempts1 he ?9ks1 may o!rwise be successfully made 9 ! magnification ( ! small motion ( ! h& 9 a frictionless mann] by optical means to obta9 cle>] def9ition4 #hdj4--;,an improvem5t 0 made 9 ! an]oid 9 "o direction by ! late ,?omas ,cooke#fd by replac+ ! *a9 by a ?9 gold b& ^u1 & lead+ f1 ! drum4 ,?is obviat$ ! small diff]5ce ( rate ( displacem5t due to sep>ate jo9t$ l9ks z !y leave ! tang5t ( ! drum4 ,x is said1 h[ev]1 to cause a little spr+9ess at ?is po9t1 :]e x %\ld be v dead1 :i* some:at m9imises ! improvem5t2 s t x has n be5 v g5]ally adopt$4 #hda4--;,b\rdon's ,an]oid1 inv5t$ by ,c4 ,b\rdon 9 #ahdi4fe ,! motor ( ?is in/rum5t consi/s ( a flat1 oval tube b5t into a circul> =m4 ,?is tube op5s to great] & less] curvature by diff]5ce ( ext]nal pressure ^u x4 ,! small motion giv5 at "o free end ( ! tube is multipli$ up by ge>work4 ,?is in/rum5t is f\nd to act mo/ delicately z a /eam gauge2 b exp]i5ce has %[n t x is n s s5sitive or durable = indicat+ atmosph]ic pressure z ! vacuum-*amb] an]oid la/ describ$4 #hdb4--;,hypsomet]1 or ,boil+-po9t ,!rmomet]4--,t wat] or any o!r liquid boils at a c]ta9 temp]ature1 accord+ to ! am\nt ( atmosph]ic pressure surr\nd+ x1 is easily obs]v$ by plac+ a cup ( boil+ hot wat] "u ! receiv] ( an air-pump4 ,at fir/ ! surface w rema9 /ill1 b z ! pressure ( ! air is pump$ (f x may be made to boil "t aft] "t until x arrives at a l[ temp]ature4 ,! temp]ature at :i* ! wat] boils z ! air is r>ifi$ may be easily foll[$ by obs]vation ( a !rmomet] imm]s$ 9 ! cup ( wat]2 & at ! same "t1 if a b>omet] be plac$ 9 connection ) ! receiv] x w indicate ! pressure1 f :i* ! scale ( diff]5ces may be practically made4 ,= ! civil eng9e] ?is in/rum5t1 accompani$ by ! an]oid1 is 9 e way sup]ior to ! m\nta9 b>omet]1 :i* mu/ necess>ily h a ?ree-feet tube1 z ! hypsomet] is mu* light]1 m portable1 & less liable to injury1 & p]haps1 f ! unc]ta9ty ( keep+ a pure vacuum 9 ! b>omet]1 saf] z a means ( obs]vation4 ,illu/ration3 ,fig4 #cih4--;,hypsomet]1 or boil+ po9t !rmomet]4 ,illu/ration3 ,fig4 #cii4--;,case = hypsomet]4 #hdc4--,! mod]n =m ( in/rum5t is %[n 9 ,fig4 #cih4 ,! boil] %[n imm$iately ov] ! lamp is fill$ ab\t half full ( ra9 wat] by lift+ (f its cov]+ tube ,c4 ,! cov]+ tube has a small] tube1 ab\t #c in*es long & in* diamet] lead+ upw>ds f x1 ?r\gh :i* ! !rmomet] bulb is pass$ into ! boil]4 ,?is tube is cov]$ by ! jacket ,j1 =m$ ( f\r telescopic tubes t are ext5d$1 z %[n 9 ! figure1 = use1 b :i* close up q compactly :5 ! in/rum5t is put 9 its case4 ,! upp] draw] ( ! jacket tube is ab\t in* diamet]1 s t ! tube enclos+ x passes ov] ! lead+ tube :5 ! app>atus is clos$4 ,! lamp1 :i* is fill$ ) pure _s1 draws out f ! bottom ( ! out] cas+ ,o4 ,x c>ries a wick hold] ) screw cap1 & ?is aga9 has a cov]+ cap to secure ! _s p]fectly :5 ! in/rum5t is c>ri$ ab\t4 ,! inn] cas+ ,a is p]=at$ ) holes to admit air at ! level ( ! body ( ! lamp4 ,:5 ! lamp is light$ & complete = use x is plac$ v]tically 9 its out] case ,o1 :i* is jo9t$ 9 two p>ts & p]=at$ by l>ge holes surr\nd+ x top & bottom3 ! bottom holes are cov]$ ) wire gauze4 ,by ?is arrangem5t ! flame is n s]i\sly di/urb$ by w9d or ra94 #hdd4--,! ,!rmomet]1 ^u :i* ! action ( ! in/rum5t dep5ds1 has a /\t /em ab\t #f in*es long & in* diamet]1 ) a v f9e1 flat1 oval bore ab\t #ja in* wide & n mu* ov] #jje in* 9 ?ickness4 ,! /em is divid$ v op5ly = ab\t #be bel[ #ajj c5tigrade1 ea* degree be+ subdivid$ into #aj1 bel[ #bab if ,fahr5heit scale be us$1 ) ea* degree divid$ into #e4 ,! divisions are fill$ 9 ) lamp-black1 & ! /em is back$ ) :ite enamel to give cle> read+4 ,! !rmomet] ,t :5 9 use is surr\nd$ by a vulcaniz$ indi>ubb] coll> ,i :i* slips ov] its /em to adju/ x to position 9 ! boil] tube z %[n4 ,9 plac+ ! !rmomet] 9 its jacket1 x is important to hold x erect to be sure x passes into ! lead+ tube f ! boil]1 z !re is g5]ally j room = x to cat* by ! side ( ?is tube1 :]e if x 7 press$ d[n x w\ld break ! bulb4 ,:5 ! !rmomet] is out ( use ! rubb] coll> is remov$1 & ! !rmomet] is plac$ 9 a tubul> metal case :i* is l9$ ) indi>ubb] tub+1 s t no j> c injure x4 ,! :ole app>atus :5 clos$ is c>ri$ 9 a solid lea!r case1 :i* conta9s divisions = ! sep>ate p>ts ( ! app>atus1 & a /rap = pass+ ov] ! %\ld] = c>ry+ x4 ,fig4 #cii %[s ! g5]al =m ( case4 #hde4--,use ( ! ,hypsomet]4--,saussure calculat$1 f data ( 8 asc5ts ( ,swiss m\nta9s1 t ! temp]ature ( boil+ wat] decreas$ #a c5tigrade = e #ighe feet ( asc5t1 :]e ! mean temp]ature ( ! atmosph]e 0 e/imat$ at #j c5tigrade1 or freez+ po9t4 ,if ! temp]ature ( ! surr\nd+ atmosph]e be tak5 z #ee c5tigrade1 ! asc5t p] degree ( t scale is #ajjj feet4 ,?is becomes1 !re=e1 ! mo/ conv5i5t data to calculate f1 all[+ #ci feet p] #ajjj p] degree c5tigrade = temp]ature above or bel[ #ee c5tigrade at any two /ations ( obs]vation1 ( :i* ! diff]5ce ( level is requir$4 ,?us3--,if at ! fir/ /ation ! temp]ature ( air be #aef c5tigrade1 ! boil+ po9t #iee c5tigrade2 second /ation temp]ature ( air #ada c5tigrade1 boil+ po9t #idb c5tigrade1 ! b>ometrical pressure ( ! l[] /ation be+ tak5 z a con/ant1 or ref]r$ to ! an]oid = correction2 !n #aef - #ee 7#ia7 7#ci7 #bib dif4 #iee - #idb 7#ac7 7#ajjj7 #acbib - dif4 ext]nal temp]ature 7#aef - #ada7 7#ci7 #acbcd diff]5ce ( level 9 feet4 ,sometimes ! !rmomet] is divid$ to ,fahr5heit degrees1 subdivid$ into #e to read by int]space & l9e to #a ,f4 ,?is may be *ang$ to c5tigrade = use ( ! above =mula by tak+ #cb ,f4 l[] ?an ! read+ & multiply+ by #e_/i4 ,?us-- #fj ,fahr4 #e_/i 7#fj - #cb7 #aeee c5tigrade4 ,! calculation propos$ by ,lefroy is1 h[ev]1 simpl] = ,fahr5heit scale4 ,to all[ = dim9ution ( boil+ temp]ature1 ) height f #bab1 ) b>omet] at #cj in*es1 take #eaa feet ( altitude = ! fir/ degree & add #b feet = ea* succe$+ degree4 ,?us1 tak+ height ( fir/ /ation h correct$ = #bab ,fahr41 #cj in*es b>omet]1 rememb]+ decrease ( b>ometrical pressure acts ! same z increase ( height4 ,!n-- #baa boil po9t h #eaa feet4 #baj h #eaa #eac h #ajbd feet4 #bji h #eaa #eac #eae h #aeci feet4 ,,footnotes3 #ei ,briti% pat5t1 ,no4 #ajaeg1 ,april1 #ahdd4 #fj ,briti% pat5ts--,no4 #acccb1 ,novemb]1 #ahej2 & ,no4 #fhb1 ,m>*1 #ahfb4 #fa ,pat5t1 ,no4 #acccb1 ,may1 #ahej4 #fb ,pat5t ,no4 #cded1 ,decemb]1 #ahfb4 #fc ,pat5t ,no4 #cdbe1 ,m>*1 #ahhf4 #fd ,pat5t ,no4 #bgad1 ,octob]1 #ahfe4 #fe ,pat5t ,no4 #abhhi1 ,decemb]1 #ahdi4 ,,*apt] ,,xix4 ,,miscellane\s ,,surveyors' ,,& ,,eng9e]s' ,,in/rum5ts1 ,,appliances1 ,,& ,,accessories--,,cross ,,/aff--,,me*anics' ,,levels ,,& ,,cl9omet]s-- ,,bon+ ,,rods--,,footn]',s ,,railway ,,gauge--,,gir? ,,/rap ,,= ,,timb] ,,measurem5t--,,gir? ,,tapes--,,timb] ,,m>k]--,,sla%+ ,,knife--,,bill-,,hook-- ,,reconnoitr+ ,,glass--,,telescope--,,sun ,,spectacles--,,:i/les--,,pione] ,,tools--,,sket* ,,block ,,book--,,cam]a--,,geological ,,tools--,,wealemefna-- ,,opisomet]--,,b\*]',s ,,calculator--,,slide ,,rules--,,full]',s ,,calculator-- ,,eng9e]s' ,,pocket ,,books--,,*ronomet]--,,outfits4 #hdf4--;,cross ,/aff4--,^? ( ,ty*o ,brah & ( ,gunt] 7 v elaborate affairs1 consi/+ ( a pair ( not*$ cross-b>s slid+ on a divid$ rod :i* gave directions to =m any angle 9 a quadrant f ! eye by slid+ ! b>s fur!r f or ne>] to x4 ,! survey+ cross /aff1 aft] bett] in/rum5ts 7 inv5t$ to take angles1 became a cross at "r angles1 sawn ^u a disc ( wood & support$ ^u a /aff :i* 0 press$ into ! gr\nd4 ,?is 0 us$ by look+ along ! saw cuts to take (fsets to ! *a91 & = sett+ out build+s4 ,! fix$ cross-head 0 mu* improv$ by mak+ x a cross ( metal ) turn$-up ends1 d[n ! c5tre ( :i* v]tical saw cuts 7 made at "r angles1 ,fig4 #djj4 ,?is1 9 ! au?or's op9ion1 is /ill ! be/ =m4 #hdg4--;,cyl9drical heads sup]s$$ ! op5 cross-head4 ,! mod]n in/rum5t 9 use is ! ,fr5* =m1 ,fig4 #dja1 :i* is made ( octagon brass tube4 ,?is is cut ) alt]nate sight slit & opposite w9d[1 ) v]tical hair on ea* ( f\r rectangul> sides ( ! octagon4 ,on ! o!r f\r sides !re are pla9 slits subt5d+ #de to ^? fir/ m5tion$4 ,! octagon tube is m\nt$ ^u a socket-piece :i* fits ^u a conical po9t$ /aff4 ,! defect ( ?is cross-head is ! clos5ess ( ! slits1 due to ! small diamet] ( ! tube1 :i* r5d]s ! direction giv5 = sight+ unc]ta94 ,illu/ration3 ,fig4 #djj4--,op5 cross-head4 ,illu/ration3 ,fig4 #dja4--;,fr5* =m4 ,illu/ration3 ,fig4 #djb4--;,adju/able cross /aff head4 #hdh4--;,adju/able ,cross ,/aff ,head4--,! cross /aff head is sometimes made cyl9drical1 9 two p>ts1 ,fig4 #djb4 ,! upp] "p is c5tr$ ^u ! l[] s t ! upp] s]ies ( sights move to any angle 9 relation to ! l[]4 ,9 ?is con/ruction a :eel is cut ab\t ! axis ( ! upp] "p1 :i* works into a p9ion 9 ! l[] "p1 s t ! upp] "p may be revolv$ horizontally by x4 ,! meet+ planes ( ! two cyl9d]s are divid$1 ! l[] into degrees & ! upp] ) a v]ni]4 ,! v]ni] is almo/ an unnecess>y ref9em5t1 z ! sight+ di/ance f slit to hair is only ab\t ?ree in*es1 & no v great exactness c be obta9$ 9 ! sight+4 ,?is in/rum5t has commonly a magnetic compass ^u ! upp] surface4 ,x is ab\t z exp5sive z ! semi-circumf]5t]1 %[n ,fig4 #bcb1 p4 #cdg1 & v inf]ior to t in/rum5t ow+ to ! extreme clos5ess ( ! sights4 ,its use is obvi\s4 ,_m ( ! foll[+ articles1 briefly describ$1 may be beyond ! direct prov9ce ( ?is "w2 b ! utility ( ^! implem5ts = complet+ ! equipm5t ( a surveyor or eng9e] = special "w x is hop$ w be suffici5t apology = _! introduction4 ,! subject c sc>cely be treat$ except 9 a desultory mann]4 #hdi4--,me*anics' ,levels4--,9 cr[d$ ,ea/]n cities1 9 levell+ ?r\gh close passages1 9 _m cases ! surveyor has to resort to me*anical levell+ to c>ry 8 levels ?r\gh4 ,me*anics' levels are too well kn[n to ne$ mu* description4 ,! ord9>y good k9ds are made f #f in*es to #ah in*es long1 g5]ally ( rosewood1 z ?is wood is v h>d & /&s well4 ,!y h a brass plate at ! top1 & tips ( ! same metal at ! base4 ,! illu/ration1 ,fig4 #djc1 is ( a #ab-;in* level4 ,! level tube1 :i* is ( bl[n glass1 is fix$ 9 pla/] ( ,p>is1 & ! upp] plate screw$ d[n ov] x4 ,illu/ration3 ,figs4 #djc1 #djd4--,me*anics' ,levels4 #hej4--,! ,au?or's ,h& ,level is %[n ,fig4 #djd--ab in*4 ,?is is made ( a ca/+ ei!r ( iron or brass4 ,! level tube is gr\nd to curvature & is some:at sup]ior to ! ord9>y run ( ?is class ( "w4 ,! level tube is fitt$ ) ball socket at "o end & /iff spr+ fitt+ at ! o!r1 :i* is adju/able1 s t ! tube may be easily replac$ if brok54 ,^! levels are commonly fix$ ^u a /\t fir /raight-edge ( ab\t #e feet to #aj feet 9 l5g? by ! lugs at ! ends4 ,! level is tak5 by block+s ^u ! gr\nd4 ,corrections ( error1 bo? 9 level & /raight-edge1 may be made = any consid]able di/ance by rev]s+ ! =w>d & backw>d position ( ! level ) its /raight-edge alt]nately4 #hea4--,squ>e ,level--,circul> ,level4--,fig4 #dje repres5ts a v useful class ( level = sett+ up "s in/rum5t /&s1 plane tables1 etc41 9 :i* a pair ( level tubes are plac$ at "r angles to ea* o!r4 ,x is g5]ally made v small--#a in*es squ>e only4 ,a circul> level1 ! upp] surface ( :i* is =m$ ( a work$ concave glass1 0 lately v popul>1 & is /ill us$ to a small ext5t4 ,z ! _s _c be h]metically seal$ 91 x evaporates1 & ?is level soon fails4 ,mr4 ,j4 ,j4 ,hicks has tak5 out a pat5t = a h]metically seal$ circul> level1 describ$ p4 #if1 :i* appe>s to answ] v well4 ,illu/ration3 ,fig4 #dje4--,squ>e level4 ,illu/ration3 ,fig4 #djf4--,surface level & cl9omet]4 #heb4--;,incl9e ,level4--,= lay+ railway rails & dra9age works ! bubble is frequ5tly made adju/able by ! tube 9 :i* x is conta9$ be+ h+$ at "o end & fitt$ 9 slides to rise ) a screw at ! o!r end1 z %[n ,fig4 #djf4 ,a scale ( p]c5tage ( incl9ation ,s is commonly divid$ ^u ! adju/able end4 ,! tube is rais$ or l[]$ by ! key ,a1 :i* is remov$ aft] sett+ & _c be tamp]$ )4 ,illu/ration3 ,fig4 #djg4--,/anley's sight = me*anics' levels4 ,illu/ration3 ,fig4 #djh4--,section4 #hec4--,sight$ ,levels4--,a me*anic's level is commonly made ) a hole longitud9ally ?r\gh x ( ab\t in* diamet]1 clos$ at "o end1 except a small hole ( #a_/cj in* or s1 & a cross ^u a piece ( glass at ! o!r end4 ,?is plan p]mits a sight to be tak5 ?r\gh x :i* gives an approximate level4 ,occasionally ! same =m ( sight z t describ$ is h+$ on ! top surface at ea* end ( ! level4 ,! au?or has f\nd a bett] plan ( sight+ to be giv5 by a pair ( sights plac$ on a c5tre ^u ! ends ( ! level to turn up :5 requir$ = use1 z %[n ,fig4 #djh1 ,p ,s "o ( ! pair ( po9ts4 ,?is1 :5 turn$ up1 %\ld]s on ! /op-piece ,a ,b4 ,! /op-piece is made ( suffici5t ?ickness to admit ! po9t 9 ! hole ne> ,b = protection :5 x is fold$ away out ( use4 ,! section ( ! level1 z %[n by ! end view ,d1 is ! same z t ( ! level1 ,fig4 #djd4 ,v fair accuracy may be obta9$ by mak+ ^! sights appe> co9cid5t ^u a di/ant /aff or rod4 ,illu/ration3 ,fig4 #dji4--;,bon+-rod4 ,illu/ration3 ,fig4 #daj4--;,bon+-rod ) /&>d4 #hed4--;,bon+-,rods1 ,fig4 #dji4 ,^! are v commonly employ$ ) me*anics' levels4 ,!y are made some:at l a /\t ,t-squ>e ( #c feet to #d feet 9 l5g?1 ab\t #c in*es 9 wid?1 & in* 9 ?ickness bo? ( ! /em & head4 ,!y are at fir/ plac$ at a di/ance ap>t1 #i or #aj feet1 & a /raight-edge ( ?is l5g? is laid f "o to ! o!r1 ^u :i* ! m\nt$ level is aft]w>ds plac$1 ! bon+-rod be+ tapp$ d[n 9 ! gr\nd till ! bubble is 9 ! c5tre ( its run4 ,a ?ird bon+-rod is !n plac$ at ! same di/ance z ! fir/ pair1 & ! /raight-edge ) ! level ^u x is rev]s$ end = end4 ,?is1 if ! "w be fairly d[n1 leaves ! two out] bon+-rods level1 h[ev] imp]fect ! /raight-edge & level may be1 if ! run ( ! bubble be tak5 correctly4 ,by remov+ ! c5tral bon+-rod f ! out] pair ( rods1 levels may be cont9u$ by sight+ ov] !m1 or bon+ =w>d z x is t]m$4 ,on ! ,cont95t bon+-rods are commonly fix$ by driv+ a sep>ate /&>d into ! gr\nd1 :i* has a pair ( brass sl+s by its side to hold ! rod1 ,fig4 #daj4 ,?is is a mu* neat] plan ?an t 9 common use ( block+ ! rod up ) /ones4 ,bon+-rods are also sometimes us$ conv5i5tly ) a prop] survey+ level1 f ! tops ( wat]-pipes1 etc4 ,illu/ration3 ,fig4 #daa4--;,footn]'s railway gauge & cl9omet]4 #hee4--,railway ,gauge1 comb9+ level & cl9omet]4 ,?is high-class gauge1 ,fig4 #daa1 is ! inv5tion ( ,mr4 ,h4 ,footn]1 ,c4,e41 late ( ! ,london & ,nor?-,we/]n ,railway4 ,x is =m$ ( a b> ( ,spani% mahogany neatly %ap$4 ,! end fitt+s are ( /eel4 ,! gaug+ "p is =m$ ( two turn-up /eel flap-pieces ) back /ops4 ,a _s level is sunk 9 ! end fitt+1 %[n 9 ! figure t[>ds ! left h&4 ,! cl9omet] is =m$ by a gun-metal p9 ( in* 9 diamet]2 #i in*es long4 ,?is slides p]p5dicul>ly 9 a spr+ fitt+ suffici5tly /iff to support ! gauge1 & is made to fall on ! c5tre ( ! rail4 ,! p9 is divid$ into in*es & eigh?s4 ,:5 x is out ( use x slides up ! end ( ! gauge & leaves ! :ole in/rum5t smoo? & portable to c>ry op5 or g into a lea!r case4 ,its use is impli$4 #hef4--,timb] ,gir? ,/rap4--,! direction = removal & e/imate ( ! value ( timb] (t5 falls into ! h&s ( ! surveyor4 ,! height ( /&+ timb] may be tak5 by a long rod1 or a pair unit$ by a l9k1 art4 #gge1 or by ! apomecomet]1 art4 #fic4 ,! gir? is mo/ conv5i5tly tak5 by a lea!r gir? /rap1 ( :i* !re are v>i\s patt]ns3 b t illu/rat$ bel[1 ,fig4 #dab1 is p]haps ! mo/ popul> =m4 ,?is /rap is made ( two /raps ( bullock's hide #a in* wide1 ?9n$ d[n to ab\t #a_/h in* 9 ?ickness2 ! two pieces are /it*$ toge!r to make x #ab feet to #ad feet long4 ,! /rap is divid$ by l9es into in*es1 b figur$ 9 units at e #d in*es s+le in*es ( qu>t]-gir?4 ,! figures & l9es are /amp$4 ,a brass weight1 %[n at "o end ( ! /rap1 is ?r[n by ! /rap ) a sw+ r\nd ! /&+ tree1 & encompasses x 9 a second ( "t4 ,! weight is caught by ! h& & ! /rap br\ght up to x to read ! qu>t]-gir?4 ,! qu>t]-gir? gives r\ghly ! equal sides ( a squ>e2 z1 = in/ance if a qu>t]-gir? reads #aj1 ! size ( ! tree is #aj #aj #ajj in*es1 or #hd cubic foot-in*es p] foot run4 ,illu/ration3 ,fig4 #dab4--,lea!r gir? /rap ) ?r[+ reel4 ,"s surveyors pref] a hook in/ead ( a weight1 z be+ m conv5i5t to measure close timb]4 ,?is is %[n ,fig4 #dac4 ,! hook is /uck into ! b>k & ! tree is gir!d by walk+ r\nd until ! hook is met4 ,illu/ration3 ,fig4 #dac4--,lea!r gir? /rap ) clut* hook4 #heg4--;,gir? ,tapes1 simil> to measur+ tapes1 ,fig4 #cdi1 p4 #ejf1 are occasionally us$1 b ^! are m conv5i5t = fell$ timb]4 ,tapes = ! purpose are made f in* to #a in* wide1 & #f1 #ab1 & #bd feet long4 ,!y h ! ord9>y feet & in*es on "o side & qu>t]-gir?s on ! o!r4 ,x is cu/om>y to all[ #a or #a in*es1 & sometimes m = b>k1 accord+ to ! species ( tree & ! cu/om ( ! c\ntry4 #heh4--,m>k+ (f ,timb]4--,= ?is a special tool ) a g\ge po9t1 ,fig4 #dad1 & /rong buck-horn h&le1 t]m$ a timb]-m>k]1 is us$ = /&+ timb] int5d$ to be fell$4 ,! cont5ts ( ! tree are sometimes m>k$ ) ! m>k] ^u x if = sale1 good b>k all[ance be+ made 9 cases ( difficulty ( extraction f ! =e/1 etc4 ,a pla9 knife is usually put ) ! m>k]1 :i* is useful z a food knife4 ,illu/ration3 ,fig4 #dad4--,timb] m>k]1 ne>ly full size4 #hei4--,! au?or makes a v small1 neat surveyor's knife1 ) m>k]1 = ! wai/coat pocket1 ,fig4 #dae1 :i* comb9es--,m tree m>k] 7small72 ,s screw-driv] = small screws ( in/rum5ts2 ,p tommy-p9 = turn+ cap/an heads2 ,f file = %>p5+ lead ( p5cil1 :5 ?is is us$ = ! field-book2 & ,e ,r two p5knife blades4 ,! knife is simil> to ! au?or's ar*itect's knife1 :i* is well kn[n4 ,! tree m>k] is n /rong en\gh = con/ant "w4 ,illu/ration3 ,fig4 #dae4--,surveyor's pocket knife4 #hfj4--,sla%+ ,knife--,bill-,hook--,axe4--,9 new c\ntries :]e sight way has to be obta9$ = ! survey ?r\gh =e/s & jungles1 "o or m ( ! tools illu/rat$ next is mo/ valuable z a "p ( ! surveyor's equipm5t4 ,! sla%+ knife1 ,fig4 #daf1 :i* is ov] a y>d long1 wield$ by a /rong man w remove light bru%wood v quickly4 ,:]e ! wood is close & ( l>g] gr[? ! bill-hook1 ,fig4 #dag1 is bett]2 & ) ?ickset timb] ! axe becomes necess>y4 ,! well-kn[n ,canadian axe is f\nd to be ! be/4 ,illu/ration3 ,fig4 #daf4--,sla%+ knife4 ,illu/ration3 ,fig4 #dag4--;,bill-hook4 #hfa4--;,h$g+ ,gloves--,iron ,hooks = ,climb+ ,trees4--,= cle>+ l& to avoid sp9es h$g+ gloves are g5]ally us$2 ^! are made ( s(t horse-hide1 & al?\gh pliable resi/ ?orns to a great ext5t4 ,clut* hooks are also v conv5i5t to climb trees1 to look =w>d = ! easie/ direction = sight way4 #hfb4--,rods = ,measur+ ,/&+ ,timb]4--,^! are g5]ally made #be feet long1 jo9t$ 9 #e feet l5g?s1 simil> to a fi%+ rod1 b mu* /iff]4 ,! rod is set by ! side ( a tree to be measur$ & obs]v$ f a di/ance :]e ! fir/ bree* cuts its l5g?4 ,illu/ration3 ,fig4 #dah4--,reconnoitr+ glass1 ,india patt]n4 #hfc4--,reconnoitr+ ,glass4--,at pres5t x is cu/om>y to use a b9ocul> field-glass 9 pref]5ce to a telescope4 ,! telescope gives great] p5etration f its high] p[]2 ! field-glass is pref]r$ = its wid] field ( view4 ,! field-glass ! au?or has suppli$ to ! ,indian ,gov]nm5t has neutral-t9t glasses c5tr$ on ! eye-pieces to take (f ! gl>e :5 look+ t[>ds ! sun1 ,fig4 #dah4 ,^! h also h+e jo9ts betwe5 ! pair ( bodies1 :i* p]mit adju/m5t ( di/ance ( c5tres to ! di/ance ( ! eyes4 ,! object-glass %\ld be #a in*es1 n ov] ?is4 ,:]e a telescope is us$1 ! #cj-;in*--! orig9al1 n ! pres5t--,india milit>y telescope is to be recomm5d$1 ,fig4 #dai4 ,?is is portable1 has a sl+ case & a good #b-;in* object glass4 ,= lightness1 alum9ium bodies are pref]r$ by _m = bo? field-glasses & telescopes2 at pres5t ! price ( ?is metal is v l[1 s t x is probable x may become 9 a %ort "t g5]al = ! purpose4 ,illu/ration3 ,fig4 #dai4--;,army telescope4 #hfd4--,prism ,b9ocul>s4--,^! w be f\nd a great improvem5t on ! old =m ( field-glasses1 z ow+ to ! optical arrangem5t a high p[] is obta9$ comb9$ ) a l>g] field ( view & good illum9ation4 ,fig4 #dbj %[s ! mo/ mod]n =m ) all ref9em5ts2 h+$ body1 c5tral focuss+ & sep>ate focuss+ to suit ea* eye4 ,x has a v compact & /rong body1 & ! size magnify+ #h diamet]s or ab\t #fd times weighs only #ac ozs4 ,illu/ration3 ,fig4 #dbj4--,/anley's prism b9ocul>4 #hfe4--;,dome ,spectacles--,bogles4--,spectacles ( neutral t9t are mo/ com=table = g5]al we> 9 sunny or sn[y c\ntries4 ,! dome or globul> =m is g5]ally pref]r$4 ,:]e !re is hot du/ gauze sides are to be pref]r$4 ,!re is a v *eap =m ) gauze sides1 :i* holds on ! head by an ela/ic b&1 t]m$ bogles4 ,^! are r hot to ! face1 & ! b& aft] a "t becomes /icky4 ,! spectacle =m is mu* bett]4 ,! glasses are made 9 v>i\s %ades to *oice3 "s v d>k or ev5 black1 ! latt] be+ made = view+ & t5d+ arc lights4 #hff4--,:i/les made v p[]ful are mu* us$ 9 explor+ abroad to br+ ! p>ty toge!r1 & = signall+ g5]ally by s\nd1 us+ ! ,morse signals1 art4 #hjc4 #hfg4--,pione]s' ,tools4--,a small set ( ^! is (t5 v useful to ! surveyor 9 new =e/ c\ntries4 ,! common set consi/s ( a claw-hamm]1 wood-*isel1 /one-*isel1 p9c]s1 screw-driv]1 gimlet1 & brad-awl4 ,! lea!r case is #h by #d by #b in*es2 x weighs #a lbs4 ) /rap4 ,?is may be supplem5t$ by a small ,am]ican saw1 cutt+ bo? edges1 ab\t #bj in*es long1 & ! axe previ\sly describ$1 ) a few p\nds ( wire nails4 ,! tools s]ve = m>k+ trees or rocks1 erect+ signals1 tempor>y cov]s1 etc4 #hfh4--,sket* ,block ,book--,pocket ,book4--,9 reconnoitr+ no bett] in=mation c be giv5 ( a track ?an =w>d sket*es f comm&+ /ation to /ation4 ,sket* books ab\t #g in*es by #e in*es are g5]ally f\nd suffici5t4 ,! draw+-pap] %\ld be ?91 & ! pocket l>ge en\gh to conta9 all ! sep>ate %eets z !y are tak5 (f by ! p5knife aft] completion f ! block4 ,! sket*es may be made ) p5cil1 or a f9e f\nta9 p52 or if ! surveyor be a col\ri/ a light box ( moi/ col\rs & a wat] bottle w (t5 leave pleas+ sket*es z rem9isc5ces4 ,pocket-books ) section l9es to #a_/h in* or #a_/aj in* scale are sometimes us$ to give approximate plans to scale ( build+s1 etc41 :]e requir$1 z well z ! ord9>y field-book record4 #hfi4--;,cam]a4--,rec5tly ! cam]a has be5 mu* us$ = reconnoitr+4 ,^! are n[ made v light & portable to take plate or #c #c in* films1 ei!r on roll]s or 9 sep>ate films4 #hgj4--;,cem5t ,te/]s are made 9 v>i\s mann]s1 g5]ally to te/ ! cohesion ( ! cem5t z a homog5e\s h>d body4 ,mr4 ,mann's cem5t te/]1 ,fig4 #dba1 goes on ano!r pr9ciple--x te/s ! adhesion ( ! cem5t to /one1 :i* appe>s to ! au?or to be its mo/ important function2 x is always h>d en\gh4 ,illu/ration3 ,fig4 #dba4--,mann's cem5t te/]4 #hga4--,watson's ,improv$ ,vicat ,ne$le is a mo/ ref9$ & accurate in/rum5t = det]m9+ ! "t tak5 by cem5t 9 sett+4 ,! cem5t is plac$ 9 ! circul> conta9] %[n 9 ! illu/ration1 & ! weight$ ne$le is l[]$ into x by means ( ! h&le at ! top4 ,! dep? ( p5etration is %[n 9 millimetres on ! divid$ arc4 ,illu/ration3 ,fig4 #dbb4--,watson's vicat ne$le4 #hgb4--;,geological ,tools4--,acid-bottle--,bl[-pipe--,t\*-/ one4-- ,:]e c\ntries are prospect$ = railways x (t5 becomes important to exam9e ! rocks1 bo? to detect ! s(t] rocks = cutt+ & to f9d lime/one suitable = mort>4 ,a geological hamm]1 weight ab\t #b lbs4 to #c lbs41 is ! ord9>y tool4 ,?is1 ) a *isel & sailclo? bag ) /rap1 is all ! necess>y appliance4 ,9 se>*+ = lime/one a small bottle ( sulphuric acid sewn up 9 a lea!r case is useful4 ,a dipp] is bl[n on ! /opp] ( ! bottle1 & a s+le drop ( acid w detect lime/one by ! bubble ( fro? x produces4 ,:]e m9]als are to be exam9$1 a small bl[-pipe app>atus is necess>y4 ,?is %\ld be accompani$ by a book ( in/ructions4 ,:]e ! surveyor has n be5 tra9$ to use ! bl[-pipe1 "o ) con/ant bla/ %\ld be employ$4 ,= exam9ation = preci\s metals a t\*-/one & two-acid bottle--sulphuric & nitric--= silv] & gold1 are useful4 ,! metal is m]ely rubb$ on ! /one & ! acid appli$4 ,if ! metal is base ! acid removes x f ! surface ( ! /one4 ,if preci\s x removes o!r matt] & leaves x visible4 #hgc4--,wealemefna--,opisomet]4--,! wealemefna is a v neat =m ( space runn] inv5t$ by ,mr4 ,e4 ,r4 ,morris1 :i* is f\nd a v conv5i5t in/rum5t = measur+ di/ances on maps 9 prospect+4 ,x is v small & light1 & may be1 if desir$1 atta*$ to ! wat*-*a94 ,x gives di/ances run ov] 9 in*es & eigh?s1 to be aft]w>ds calculat$ to ! scale ( ! map1 ,fig4 #dbc4 ,! opisomet] = ! same purpose1 ,fig4 #dbd1 is =m$ ( a spur :eel at ! end ( an ivory h&le runn+ ^u a screw4 ,?is in/rum5t gives measurem5t by rev]s+ its run ^u ! scale ( ! map4 ,illu/ration3 ,fig4 #dbc4--,wealemefna4 ,illu/ration3 ,fig4 #dbd4--,opisomet]4 #hgd4--;,b\*] ,calculator1 ! inv5tion ( ,m4 ,alex4 ,e4 ,m4 ,b\*]1 eng9e]1 ( ,p>is4#ff ,?is is "o ( ! mo/ conv5i5t pocket calculators t a civil eng9e] c desire1 be+ only ( ! size ( an ord9>y wat*4 ,! in/rum5t 0 =m]ly made 9 ,france = ?is c\ntry 9 a v slov5ly mann]4 ,x is n[ made 9 ,london by ! au?or1 ( s\nd "w & accurate c5tr+1 ,fig4 #dbe4 ,x has face back & front4 ,! front "o1 :i* is %[n 9 ! illu/ration1 c>ries log>i?mic scales ( s9es1 numb]s & squ>e roots1 & is made to revolve by turn+ ! mill$ head plac$ "u ! h&le1 z ! w9d] ( a keyless wat*4 ,! back dial1 :i* is fix$ & does n revolve1 has ^u x a scale ( equal p>ts giv+ ! decimal p>ts ( log>i?ms1 & a log>i?mic scale ( cube roots4 ,!re are ?ree index h&s1 "o fix$ on ! side ( ! case ov] ! front dial1 z %[n 9 ,fig4 #dbe1 & "o on ea* end ( ! c5tral axis made to revolve simultane\sly ov] ! back & front dials by means ( ! mill$ head at ! side ( ! case4 ,any op]ation involv+ multiplication1 division1 proportion1 p[]s or roots c be p]=m$ approximately ) great rapidity by ! aid ( ?is calculator1 & x is practically z simple to use z an ord9>y slide rule1 z w be se5 f ! foll[+ explanation ( its use3-- ,illu/ration3 ,fig4 #dbe4--;,b\*]'s calculator4 ,illu/ration3 ,fig4 #dbf4--,/anley-,b\*] calculator4 ,multiplication1 us+ ! second circle ( divisions f ! outside ( ! front dial3--,br+ ! fir/ factor "u ! fix$ index1 set ! movable index to #a1 !n br+ ! second factor "u ! movable index1 & ! product w be f\nd "u ! fix$ index4 ,division is p]=m$ on ! same scale z foll[s3--,br+ ! divid5d "u ! fix$ index1 set ! movable index to ! divisor1 !n br+ #a to ! movable index1 & ! quoti5t w be f\nd "u ! fix$ index4 ,= proportion ! second circle is also us$3--,set ! fir/ factor "u ! fix$ index & set ! movable index to ! second "o1 !n ! proportionate equival5t ( any numb] br\ght "u ! =m] w be f\nd at ! movable index4 ,squ>e roots1 us+ ! same scale3--,br+ ! numb] "u ei!r ( ! indices1 & ! squ>e root w be f\nd ^u "o ( ! two inn] circles ( ! same dial4 ,cube root3--,9 ?is case x is necess>y to fir/ br+ ! #a on ! front dial "u ! fix$ index1 !n set ! movable index to ! numb]1 & ! cube root w be f\nd on "o ( ! inn] circles ( ! back or fix$ dial4 ,to use ! trigonometrical dial3--,br+ ! ne$le ( ?is dial ov] ! angle ( :i* ! s9e or tang5t is requir$1 & read ^u ! o!r dial 7indicat$ by ! ne$le7 ! natural trigonometrical l9e ^u ! inn] circle1 or its log>i?m ^u ! out] circle4 ,! book ( in/ructions suppli$ ) ! in/rum5ts1 writt5 by ,pr(essor ,george ,full]1 ,c4,e41 = ! au?or1 gives all directions = work+ & also gauge po9ts f :i* calculations are made z ) ! slide rule4 #hge4--;,9 r$uction ( factors ( a calculation collectively ,b\*]'s calculator may take m ?an "o turn or less ?an unity4 ,! au?or has add$ a c5tral index to record ! numb] ( turns4 ,?is is said to be ( great value = ! p]fection ( ! in/rum5t1 ,fig4 #dbf4 #hgf4--,slide ,rules1 ( :i* !re are great v>ieties1 are ( too complex a nature to discuss1 except v briefly1 9 our limit$ space1 p>ticul>ly z g5]al descriptions h be5 (t5 giv54 ,! ord9>y log>i?mical scales ( ,gunt] 7#afai71 kn[n z ,gunt]'s l9es1 are plac$ ^u mo/ slide rules4 ,! ari?metical l9es are lett]$ ,a1 ,b1 ,c1 ,d1 & ,e4 ,a & ,b are alike3 ^! are te*nically t]m$ d\ble radius log4 l9es4 ,!y are us$ = all processes ( multiplication & division4 ,c & ,d are also alike & are t]m$ s+le radius log4 l9es4 ,!y are us$ toge!r = ord9>y multiplication & division1 & 9 conjunction ) ,a & ,b scales = squ>es & squ>e roots4 ,! ,e l9e1 n orig9ally a ,gunt]'s l9e1 b f\nd e>ly 9 ! c5tury on sev]al rules1 is t]m$ a triple radius log4 l9e4 ,! numb]s ( ! divisions on ?is l9e are ! cubes ( ! numb]s ( ! correspond+ divisions ( ! ,d l9e1 ) :i* x g5]ally works4 ,all ^! l9es "w reciprocally toge!r1 p]=m+ ! mo/ complex calculations by simply sett+ !m to numb]s or gauge po9ts ( :i* giv5 solutions are requir$1 z = in/ance1 ! fir/ f\r l9es 9 comb9ation give answ]s to su* que/ions z3--,to divide by a numb] two numb]s multipli$ toge!r1 "o ( :i* is squ>$2 to divide ! product ( two numb]s by ! squ>e ( a ?ird numb]1 etc41 ea* ( :i* calculations is p]=m$ at a s+le sett+4 ,by inv]sion ( ! slide ,a to ,c ! reciprocal ( a giv5 numb] is f\nd1 also ! mean proportional betwe5 two numb]s1 ! f\r? t]m is inv]se proportion1 etc4 ,trigonometrical calculations are p]=m$ by ! l9es ( s9es1 tang5ts1 etc4 ,in/ructions are to be f\nd 9 ! books suppli$ ) ! rules1 & z a "p ( _m works4 ,among ! mo/ complete books may be m5tion$ ,! ,slide ,rule1 by ,r4 ,g4 ,bla9e1 ,m4,e41 & ,! ,slide ,rule1 by ,*as4 ,n4 ,pickwor?4 ,^! bo? conta9 v full in=mation on ! subject4 #hgg4--,! ,slide ,rules 9 mo/ g5]al use are ,a4 ,ne/l]'s & ,a4 ,w4 ,fab]'s4 ,bo? ^! well-kn[n firms make a v complete s]ies1 applicable to a great v>iety ( te*nical calculations4 #hgh4--,! revis] has rec5tly complet$ f ! designs ( ! au?or an entirely automatic divid+ eng9e = ^! rules1 :i* is ! only "o 9 exi/5ce4 ,a great numb] ( slide rules are made = special purposes only3 "s ( ^! are v useful to ! civil eng9e]4 #hgi4--;,hudson's ,slide ,rules give /r5g? ( %afts1 beams1 & gird]s2 pump duty2 & computation ( horse-p[] 9 eng9es4 #hhj4--;,honeysett's ,hydraulic ,slide ,rule gives dis*>ge ( wat] f *annels & pipes ( diff]5t =ms & incl9ations4 #hha4--,ta*eometrical ,slide ,rules ) scale ( s9e#b & s9e cos4 = calculat+ ! horizontal equival5ts & v]tical heights f ta*eometrical obs]vations4 ,^! are made ei!r = use ) in/rum5ts divid$ sexagesimally to #cfj or c5tesimally to #djj4 #hhb4--,%epp>d's ,slide ,rule has duodecimal l9es1 d\ble read+1 = squ>+ & cub+ timb]4 #hhc4--,"y's ,slide ,rule is design$ = squ>+ & valu+ timb] simultane\sly1 :i* op]ations x p]=ms 9 a v exp$iti\s mann]4 #hhd4--;,essex's ,slide ,rule is ! be/ = calculat+ ! rates ( velocity & dis*>ge f sew]s1 wat] ma9s1 *annels1 & culv]ts ( diff]5t =ms1 z x works ) all =mul4 #hhe4--,! ,slide ,rule ( ,pr(4 ,geo4 ,full]1 ,c4,e41 ,fig4 #dbg1 pres5ts p]haps ! highe/ pres5t ref9em5t ( ?is class ( rules1 capable ( greatly facilitat+ ! num]\s ari?metical calculations ( ! civil eng9e]4 ,its range is great] ?an mo/ calculat+ ma*9es1 & besides ! op]ations ( multiplication & division1 squ>+ & cub+1 results requir+ ! reciprocals1 p[]s1 roots1 or log>i?ms ( numb]s c be quickly & easily work$ out by its use4 ,illu/ration3 ,fig4 #dbg4--,pr(essor ,full]'s calculat+ slide scale4 ,! rule consi/s ( an out] cyl9d] t c be mov$ up or d[n1 & turn$ r\nd ^u ! cyl9drical axis :i* is held by ! h&le4 ,^u ! out] cyl9d] a s+le spiral1 log>i?mical scale is cont9u$ f end to end1 ! total l5g? ( :i* makes ! scale #ejj in*es long4 ,?is is graduat$ into #gbej divisions4 ,"o index is fix$ to ! h&le4 ,a second index is atta*$ to ! inn] tube block$ out by a flange to read ^u any "p ( ! scale2 s t altoge!r !re are ?ree tubes :i* "w toge!r telescopically1 by means ( :i* ! indices may be set to any position on ! graduat$ cyl9d]4 ,/ops are plac$ s t ! indices may be br\ght to z]o4 ,by ^! means1 ! indices be+ set to any ( ! gauge po9ts1 ! log>i?mical scale1 mov+ by itself1 w ma9ta9 ! same proportion = any numb]s4 ,9 ?is rule a s+le log4 radius is repeat$ by co9cid5ce ( indices1 s t its scale ( divisions1 #da feet #h in*es long1 if comp>$ ) an ord9>y d\ble radius slide rule1 becomes equal to a slide rule ( #hc feet #d in*es long4 ,! ord9>y #ab-;in* slide rule has ab\t #hj divisions to ea* radius1 s t x is easily se5 h[ mu* m exact quantities may be br\ght out ) a rule ( #gbej divisions4 ,x is a mo/ valuable rule = calculations = ! ta*eomet]4 ,copi\s tables ( gauge po9ts = civil eng9e]s are pr9t$ ^u ! c5tral tube1 :i* is supplem5t$ by a book ( in/ructions4 ,! value ( ?is rule has be5 mu* ext5d$ by scales to facilitate subt5se calculations1 by ,mr4 ,w4 ,n4 ,bakewell1 ,c4,e41 9 ! ,full]-,bakewell slide rule4 ,illu/ration3 ,fig4 #dbh4--;,improv$ ,full]'s slide rule4 ,an additional improvem5t1 z %[n at ,fig4 #dbh1 has n[ be5 effect$ 9 ^! in/rum5ts by adapt+ ! case to support ! rule :5 9 use1 ?us ov]com+ ! objection ( be+ always oblig$ to hold x 9 ! h&4 ,! use ( ,pr(essor ,full]'s rule is1 h[ev]1 conf9$ to ari?metical computations4 ,! num]ical solution ( =mul compris+ trigonometrical functions c only be p]=m$ by extract+1 ) consid]able loss ( "t1 ! values ( ^! functions f a book ( tables4 ,to d s requires a c]ta9 ef=t ( m9d ) its consequ5t risk ( mi/akes4 ,?is limitation has re/rict$ its use 9 a consid]able body ( calculations1 su*1 = example1 z 9 ! computation ( ! co-ord9ates ( surveys f ! l5g?s & be>+s ( _! l9es1 a me?od ( plott+ :i* is v l>gely us$ by l& surveyors at pres5t2 9 a/ronomical computations2 9 civil & me*anical eng9e]+1 etc42 ! use ( log>i?ms be+ pref]r$ on ! score ( spe$1 al?\gh ! degree ( accuracy atta9$ ) ,pr(essor ,full]'s rule is amply suffici5t 9 ! l>ge majority ( cases4 ,illu/ration3 ,fig4 #dbi4--;,b>n>d's co-ord9ate spiral slide rule4 #hhf4--,! ,co-ord9ate ,spiral ,slide ,rule has be5 design$ to meet ^! requirem5ts by ,mr4 ,h4 ,o4 ,b>n>d1 ,a4,c4,h41 ,f4,r4,a4,s41 etc41 ,sup]9t5d5t ( ,trigonometrical ,surveys1 ,ceylon1 ,fig4 #dbi4 ,l ,pr(essor ,full]'s rule1 ^u :i* x is an improvem5t1 x enables ! us] to p]=m ) spe$ & accuracy ari?metical computations involv+ multiplication1 division1 proportion1 cont9u\s fractions1 p[]s1 roots1 & log>i?ms2 b 9 addition1 ! natural & log>i?mic values ( trigonometrical functions ( any angle c be det]m9$ by inspection ) ! same accuracy z 9 num]ical computation1 :ile ! products1 quoti5ts1 etc41 ( ^! functions1 by l5g?s or numb]s1 integral or fractional1 are obta9$ ) equal ease1 rapidity & precision4 ,! scope ( its op]ations w be ga!r$ f ! examples :i* are giv5 to illu/rate its use 9 ! in/ructions suppli$ ) ! rule4 ,illu/ration3 ,fig4 #dcj4--,?a*]'s slide rule4 ,al?\gh ! co-ord9ate spiral rule1 z all v>ieties ( slide rules1 is bas$ prim>ily ^u ! !ory ( log>i?ms1 a k ( t !ory is by no means ess5tial to its practical use4 #hhg4--,?a*]'s ,slide ,rule4--,fig4 #dcj4 ,?is conta9s a %ort] scale ?an ,pr(essor ,full]'s1 & ! sy/em is n q s simple4 ,full pr9t$ in/ructions are giv5 9 ! book suppli$ by ! inv5tor1 ,mr4 ,edw9 ,?a*]1 ( ,pittsburg1 ,u4,s4,a41 or ( ! au?or1 :o is 8 ag5t = ?is c\ntry4 ,! orig9al divisions ( ?is rule 7 made by ! au?or4 ,! scale is manufactur$ 9 ! ,unit$ ,/ates4 ,!re appe>s to be f\nd "s difficulty 9 its con/ruction to keep ! scales to true l5g? & get !m to exact position4 #hhh4--,pocket ,sets ( ,*a9 ,scales4--,^! are made #c1 #d1 #e1 & #f in*4 ,?ree ( #f in* =m ! ord9>y set4 ,! *a9 scales1 if ?ree only1 are #aj1 #bj1 #cj1 #dj1 #ej1 & #fj2 if six !y g5]ally conta9 ! same scales ) feet equal to ! l9ks4 ,an extra scale ) ! ordnance or o!r scale ( ! c\ntry is f\nd also useful = measur+ f maps or plans4 ,"s civil eng9e]s pref] ! pocket scales made wide ) q squ>e ends1 to be us$ z (fsets or = sket*+4 ,^! scales are g5]ally made 9 ivory & plac$ 9 a light morocco or ,russia lea!r case4 ,! numb]s ( divisions ( ! scales %\ld be /amp$ on ! ends to prev5t ! wrong scale be+ drawn f ! case4 ,illu/ration3 ,fig4 #dca4--;,biram's anemomet]4 ,illu/ration3 ,fig4 #dcb4--,l[ne's anemomet]4 #hhi4--;,anemomet]s are us$ by m9+ eng9e]s = te/+ ! v5tilation ( m9es4 ,! orig9al & be/ kn[n =m is t ( ,biram1 ,fig4 #dca4 ,?is in/rum5t is held 9 any curr5t ( air1 & ! velocity ( ! curr5t is regi/]$ by ! motion ( oblique fans1 by means ( ord9>y decimal ge>work on five dials giv+ feet & multiples by #aj4 ,l[ne's anemomet]1 ) ! au?or's improvem5ts1 ,fig4 #dcb1 is ( simil> pr9ciples ( con/ruction1 b x is arrang$ 9 portable =m to g 9 a pocket case4 ,ano!r well-kn[n =m ( anemomet] is built ^u ! same pr9ciple1 b ( cubical =m4 ,x is cu/om>y to take ! velocity ( ! curr5t = "o m9ute by a wat*1 !re be+ a det5t provid$ 9 mo/ in/rum5ts to />t & /op ! motion ( ! h&s ^u ! dials4 #hij4--;,books ( ,tables & ,=mul4--,few ,briti% ,surveyors are )\t ,moleswor?'s pocket-book4 ,?is conta9s all ! useful tables & notes ( ref]5ce valuable to ! civil eng9e] 9 8 ord9>y "w--weight1 #e ozs4 ,_m pocket-books h be5 writt5 on ! same plan4 ,hur/'s pocket-book conta9s all matt]s ( ref]5ce = ! t[n surveyor among build+s4 ,trautw9e's ,civil ,eng9e]'s ,pocket-book 7,am]ican7 is ! mo/ complete1 b x is ( d\ble ! weight ( ! ,moleswor?4 ,spon's ,eng9e]s' ,tables = ! ,wai/coat ,pocket--weight1 little ov] oz4--is a v useful little book4 ,( ,trav]se ,tables bo? ,gurd5's & ,boileau's are compreh5sive & reliable4 ,!re are sev]al pocket-books ( ,curve ,tables1 ^? ( ,cutl] ,edge1 ,beazeley1 & ,k5n$y ,hackwood be+ p]haps 9 ! mo/ g5]al use4 #hia4--,te*nical ,books--,ordnance ,maps are publi%$ on special di/ricts & subjects :i* are (t5 relative to ! c\ntry or ! special conditions ( "w abroad & at home = m9]als1 etc4 ,x is v useful to possess su* ( ^! z may be requir$1 & ! note is only made "h z a rem9d]4 #hib4--,sl+ ,case = ,draw+s4--,! mo/ conv5i5t me?od ( c>ry+ maps or draw+s = public works 9 execution is to h a solid lea!r case simil> to a telescope case4 ,?is is be/ if made ) ! cap or lid ( ! same l5g? z ! body3 x c !n be drawn out any di/ance accord+ to ! l5g? ( ! roll$ draw+4 ,if ?\ght m conv5i5t1 & ! map or draw+s are heavy1 a /rap may be add$ to pass ov] ! %\ld]1 ,fig4 #dcc4 #hic4--;,*ronomet]4--,?is may be any =m ( wat* ) comp5sat$ escapem5t4 ,at pres5t ! prices run high = ?is class ( "w2 b f ! simplicity & mod]ate c]ta9ty ( comp5sation x does n appe> t ?is %\ld be necess>y = ! production ( a fair work+ in/rum5t useful = ! surveyor 9 new c\ntries to *eck 8 longitude4 ,:]e a good *ronomet] is us$ x is bett] to keep x to ,gre5wi* "t )\t alt]ation4 ,if !re is a ga9+ or los+ rate ?is w mo/ probably rema9 con/ant 9 equal times1 s t corrections may be made pro rat = all obs]vations until a *eck c be tak5 ) c]ta9ty :5 arriv+ at a t[n :i* possesses an obs]vatory4 ,! quality ( a *ronomet] is fully asc]ta9$ by hav+ a c]tificate f "o ( our obs]vatories1 t ( ,kew be+ ! mo/ popul>4 ,illu/ration3 ,fig4 #dcc4--,sl+ case = draw+s4 #hid4--;,*ronograph4--,= ! obs]vation ( />s 9 transit = ! purpose ( tak+ longitude1 a dead-/op wat* or *ronograph is mo/ useful4 ,?is c n[ be _h 9 comb9ation ) an o!rwise fair go+ wat* at a v mod]ate price4 #hie4--,outfit ( a ,surveyor = ,"w 9 a ,new ,c\ntry4--,! ord9>y items ( /rong1 du/-col\r$ wooll5 clo?+1 good boots1 saddle1 fire>ms1 etc41 d n come )9 ! prov9ce ( ?is "w4 ,! in/rum5ts he w require w dep5d p>tly ^u ! nature ( ! c\ntry & ! k9d ( "w to be done4 ,if = prospect+ only1 light in/rum5ts are commonly select$--! sextant1 or box sextant ) glass artificial horizon1 good pocket *ronomet]1 telescope1 an]oid b>omet]1 prismatic compass1 & cl9omet]4 ,if a g5]al survey is to be made1 ! fir/ in/rum5t ( importance is ! !odolite1 ! #d or #e-;in* be+ ! mo/ usual4 ,) ?is1 pickets1 l& *a9 & arr[s1 a /eel tape = te/+1 & a l95 tape4 ,if = survey 9 m9]al di/ricts1 a good m9+-dial is requir$1 ) all accessories ( *a9s1 etc4 ,if = railway "w1 a #e-;in* !odolite1 a good level1 /aves1 pickets1 cl9omet]1 & prismatic compass4 ,9 all cases1 field-books1 draw+ in/rum5ts1 supply ( pap]1 draw+ bo>ds1 squ>es1 p>allel rule1 p5cils1 ,indian ink1 col\rs1 /5cil plates1 & o!r articles = (fice use1 ( :i* ! e/abli%$ optician or trad] w give full in=mation f 8 exp]i5ce1 or g5]al ref]5ce may be tak5 f any complete catalogue ( su* in/rum5ts4 ,,footnote3 #ff ,pat5t1 ,no4 #dcaj1 ,novemb]1 #ahgf4 ,,index ,abney's cl9omet]1 #daa ,a*romatism expla9$1 #ce ,adju/able axis1 ( plane table1 #dgi ( !odolite1 #bcg ,adju/able tripod1 #cbi ,alidades = plane tables1 #dgc ,alloys us$ = survey+ in/rum5ts1 #g ,altazimu? !odolite1 #bie ,altitudes1 measurem5ts (1 #eej ,alum9ium alloys1 #h ,anallatic telescope1 #cfd ,anemomet]s1 #eif ,an]oid b>omet]s1 ,vidie's1 #eeh ,b\rdon's1 #efh ,apomecomet]1 #dfi ,arr[s1 = *a91 #did ,artificial horizons1 #ddc ,atmosph]ic pressure1 measurem5ts (1 #eej ,axes1 workman%ip 91 #aa ,bakewell's tang5tial index1 #chd ,ball & socket adju/m5ts3 ,h(fmann's1 ,pa/orelli's1 #ccj ,b&s1 /eel1 = measur+ l&1 #ddi ,b>k]'s cl9omet]1 #dae ,b>omet]1 an]oid1 #eeh m\nta91 #eej m]curial1 #edi ,base l9e app>atus1 #eag ,beam compass measurem5ts1 #eaj ,bellamy's road trac]1 #dbj ,bill-hook1 #ehb ,b9ocul>s1 prism1 #ehd ,black1 optical1 #ad ,boil+-po9t !rmomet]1 hypsomet]1 #efi ,bon+ rods1 #egh ,books1 levell+1 #agc ,b\*]'s calculator1 #ehg improv$1 #eij ,box sextant1 #dea ) cont9u\s arc1 #dfa ) supplem5t>y arc1 #deh ,bronz+ in/rum5ts1 #ad ,brunton m9e transit1 #cec ,bubble tri]1 #hh ,burel's reflect+ level1 #add ,burni]'s cl9omet]1 #daf ,ca9k's rule = correct+ incl9es1 #dih ,calculators3 ,b>n>d's1 #eid ,b\*]'s1 #ehg ,full]'s1 #eib ,?a*]'s1 #eie ,cam]a1 #bdc1 #ehe ,cases1 = c>ry+ maps1 #eig lea!r1 = in/rum5ts1 #bc ,cavalry sket*+ case1 #dhh ,cem5t te/]1 ,mann's1 #ehe ,c5tesimal division1 #ahe ,*a9 scales1 pocket sets1 #eif ,*a9 vice1 #dif ,*a9+1 #dig ,*a9s1 l&1 v>i\s1 #dij ,*a9s1 s\nd+1 #ebf ,*ronomet] & *ronograph1 #eih ,circumf]5tor1 #cjg ,clamp & tang5t motions1 v>i\s1 #bjb ,classification ( in/rum5ts1 #e ,cl9omet] compasses1 #dah hang+1 #cdd ,cl9omet]s1 v>i\s1 #daa ,coa/ survey l9es1 #ebg ,co9cid5ce rods1 #eaa ,collimation1 #ee ,collimator1 #aba ,compass1 survey+ )1 #hj ,compasses3 magnetic1 b>1 #ei ,b>k]'s1 #hd ,burni]'s1 #hj hang+1 #cdd ,hut*9son's1 #gi lum9\s1 #hd m>9]s'1 #gc prismatic1 #ge pocket1 #hb r+1 #gb tr\gh1 #gd1 #hc ,comp5sat$ rods1 #eab ,connect+ l9k1 to ext5d h& rods1 #eca ,convex & concave l5ses1 #cb ,cooke's level1 #ach ,co-ord9ate slide rule1 #eid ,cross-/aff heads1 #egc ,curvature1 correction =1 #agj ,cu%+'s level1 #acf ,de ,lisle's reflect+ cl9omet]1 #dac ,decl9ation ( ne$les1 #fg ,deville's !odolite1 #bfc ,diagonal eye-piece1 #de ,dials1 m9+1 #cji ,diaphragm ( telescope1 #ej1 #aad1 #ace ,dip compass1 #ced ,dip ( ne$les1 #ff ,disp]sion ( light1 #ce ,divid+ eng9e1 #agf ,division ( ! circle1 #age ,d\ble optical squ>e1 #dfg ,drop arr[1 #did ,dumpy level1 #aaj improv$1 #abc ,dynamet]1 #dc ,edgewor?'s /adiomet]1 #dhb ,eng9e]'s level1 #acc ,engrav+1 note on1 #af ,ev]e/'s !odolite1 #bga tripod1 #bgc ,excise ink bottle1 #agd ,eye-pieces3 ,ramsd51 #da erect+1 #dd diagonal1 #de reflect+1 #df ,field-books1 #bhi1 #cgd1 #chj ,field-glasses1 #ehb ,f9i%+ ( survey+ in/rum5ts1 #ad ,=mation ( images 9 a telescope1 #cc ,fr5* =ms ( m9]s' dials1 #ccf ,full]'s rule1 #eib ,geological tools1 #ehg ,george's artificial horizon1 #ddf ,gir? /raps1 tapes1 etc41 #egi ,glass diaphragm1 #ec ,glass1 work+1 #af refraction (1 #be ,gradi5t scale1 #bac ,gradi5t] ,screw1 #chf ,gradiomet]1 #djd ,gradioplane1 #dji ,graduation1 #agi ,gre51 ,william1 ,subt5se in/rum5ts1 #cee ,hadley's quadrant1 #dbc ,hang+ m9+ compass1 #cdd ,h$ley's dial1 #cbb improv$1 #cbf1 #cbi1 #ccc ,heliograph1 #edj ,helio/at & heliotrope1 #ecg ,h5d]son's m9]s' dial1 #cae ,hick's pat5t level1 #if ,hi/orical sket* ( survey+ in/rum5ts1 #a ,h(fmann's ball & socket head1 #ccj ,horizontal scale ( tang5ts1 #bac ,hypot5use & base1 #bab ,hypsomet]1 #efi ,illum9ation ( axis ( telescope1 #bcd ,incl9omet]3 ,li/]'s1 #chi ,lacqu]+ "w1 #ae ,lamp1 magnesium1 #ede = levell+1 #afi m9+1 #cdh !odolite1 #bce ,l& *a9s1 #dij vice = adju/+1 #dif ,lant]ns1 oil1 #ede ,lean's m9]s' dial1 #cae ,lea!r cases1 #bc ,l5ses1 #cc a*romatic1 #cf ,level3 = levell+ /aff1 #afc me*anics'1 #ege ) incl9es1 #egf ,levels3 surveyors'1 #ig ,cooke's1 #ach ,cu%+'s1 #acf dumpy1 #aaj same improv$1 #abc eng9e]s'1 #acc reflect+1 #add pocket1 #adb simple con/ruction (1 #ada supplem5t>y p>ts to1 #aci wat]1 #adf ,y-=m1 #ih same improv$1 #ajg ,level tubes1 #hf circul>1 #if1 #egf curvature (1 #hg divisions ^u1 #ij read]s =1 #ie ,scott's1 #ic s5sitiv5ess (1 #hi ,/range's1 #ib ) air cell1 #ic ,level tube tri]1 #hh ,levell+3 books1 #agb /aves1 telescopic1 #adh semicircul>1 #aej m9+1 #aeh pap]+ (1 #aei pres]vation (1 #afa v>i\s patt]ns (1 #aea hold] =1 #afc pads =1 #afa pegs =1 #aga practice (1 #afc ,light = night obs]vations1 #afi1 #ede ,light1 refraction (1 #bg ,l9e1 s\nd+1 #ebg ,lubrication ( jo9ts1 etc41 #bj ,lum9\s compass1 #hd ,magnesium lamp1 #edf ,magnetic compasses1 #ei correction (1 #fd decl9ation (1 #fg incl9ation (1 #ff tr\gh1 #gd v>iation (1 #fh v>i\s =ms1 #hb ,magnetic ne$les1 #ei lift+1 #fe m\nt+1 #fd ,magnetic ne$les1 v>i\s1 #ei ,magnetism1 #ei pres]vation (1 #ga ,magnify+ p[] ( telescope1 #dc ,measur+ rods1 #ecj ,me*anics' levels1 #ege ,m]curial b>omet]1 #edi ,metals employ$ 9 survey+ in/rum5ts1 #g ,micromet] microscopes3 v>i\s1 #aib ,/anley's1 #aig ,micromet] !odolites1 #bei ,milit>y sket*+ bo>d1 #dhe cavalry1 #dhh ,m9]s' circumf]5tor1 #cjg ,m9]s' compasses3 ,fr5*1 #ccf hang+1 #cdd ,/anley's prismatic1 #cdc ,m9]s' dials3 v>i\s1 #cji hang+1 #cdd ,h$ley's1 #cbb ,h5d]son's1 #cae ,lean's1 #cae improvem5ts 9 ,h$ley's dial1 #cbf1 #cbi1 #ccc ,m9+1 survey lamp1 #cdh t>gets1 #cdi !odolite1 #cdb ,morse signal+1 #edd ,m\nta9 b>omet]1 #eej !odolite1 #beh ,nautical sextant1 #dbi ,ne$les1 magnetic1 #ei ,night signall+ /ations1 #ede ,octant or quadrant1 #dbb ,(fset rods1 #ejg ,omnimet]1 #cgd ,opisomet]1 #ehg ,optical black1 #ad ,optical pr9ciples ( telescope1 #be ,optical squ>e1 #dfe ,outfits = surveyors abroad1 #eih ,pack+ ( in/rum5ts1 #ba ,p>allax1 9 eye-piece1 #ee ,p>allel plates1 to level1 #ii to !odolite1 #bai ,passomet]1 #ebe ,pa/orelli's ball & socket head1 #ccj ,p$omet]1 #ebd ,p]ambulator1 #eba ,p]man5t /ations1 #ece ,pickets or rang+ poles1 #ecc ,p9e measur+ rods1 #ejh ,pione] tools1 #ehe ,photographic cam]a1 #bdc1 #ehe ,pla9 !odolite1 #bae1 #bfg ,plane tables1 #dgb ,plat9um-iridium po9ts1 #ec1 #abi1 #ace ,plummets1 #bcb ,pocket-books1 #ecd1 #eif ,pocket levels1 #if sight$1 #adb1 #ebe ,pocket magnetic compasses1 #hc ,po9t diaphragm1 #ec1 #abi1 #ace ,poli%+ "w1 #ad ,pres]vation ( in/rum5ts1 #bj ,prismatic cl9omet]s1 #dad ,prismatic compasses1 #ge ,hut*9son's1 #gi /&s1 #gh ,prismatic m9+ survey compass1 #cdc ,prisms z reflectors1 #bi ,protectors = ! eyes1 #ehd ,protractors1 sket*+1 #hb1 #cgd1 #dhe ,quadrant1 #dbb ,qualities ( "w1 #g ( a telescope1 #ef ,quick-sett+ surveyor's level1 #acb ,quick-sett+ !odolites1 #beg ,quiv] = arr[s1 #did ,railway gauge1 #egi !odolite1 #beh ,ramsd5 eye-piece1 #da ,rang+ poles1 #ecc ,ray %ade1 #abi ,read] = level tube1 #ie ,read+ microscopes1 #ahh ,reconnoitr+ glass & telescope1 #ehb ,reflect+ cap to telescope1 #ccd ,reflect+ circle1 #dbd ,reflect+ cl9omet]s1 #dac ,reflect+ levels1 #add ,reflection ( glass1 #be ,reflector 9 eye-piece1 #df ,refraction ( light1 #be ,repair+ sleeves = /eel b&s1 #eje ,revolv+ compass to dial1 #cah ,ri*mond's t5sion h&le1 = /eel b&1 #ejc ,road trac]1 #dbj ,rods3 co9cid5ce1 #eaa comp5sat$1 #eab h&1 #ecj /&>d1 #ejh ,rule1 civil eng9e]'s1 #ecb ,rule = correct+ incl9$ measurem5t1 #dih ,rule =m cl9omet]1 #dah ,semi-circumf]5tor1 #cdf ,sextants1 #dbe box1 #dea ) supplem5t>y arc1 #dfa cont9u\s arc1 #deh s\nd+1 #ddi survey+ 7op571 #dfd ,sight director to /adium1 #cfd ,sight$ pocket level1 #adb ,silv]+ sextant glasses1 #dcg ,sket* books1 etc41 #ehe ,sket*+ bo>d1 milit>y1 #dhe ,sla%+ knife1 #ehb ,slide rules1 v>i\s1 #eij ,slid+ /age to !odolite1 #bdi ,socket = /ation pole1 #ece ,sol> atta*m5t to !odolite1 #bci1 #bei ,sold]+1 #ac ,s\nd+ *a91 #ebf l9es1 #ebg ,s\nd+ sextant1 #ddi ,spectacles = protect+ ! eyes1 #ehd ,sph]ical ab]ration1 #cc ,spur %od picket1 #ece ,/adia po9ts1 #aca webs1 #aad ,/adium = ta*eomet]1 #aee1 #cgc ,/adiomet]1 #dhb ,/&>d rods1 #ejh ,/&s ( in/rum5ts1 #ai ,/ations = obs]vation1 #ecc ,/aves1 levell+1 #adi ,/eel b&s & tapes1 #dii1 #ejg ,/rid+ level1 #bcg ,/yle ( "w1 #af ,subt5se1 in/rum5ts1 #cee diaphragm1 #aad1 #cfc ,supplem5t>y arc to box sextant1 #dfa ,sun glass to telescope1 etc41 #dg ,ta*eomet]s3 g5]al description1 #cgj ,/anley's1 etc41 #cga ,ta*eomet]s3 /adium =1 #aee1 #cgc field book1 #cgd ,tang5t motions1 #bjb ,tapes1 l951 etc41 #eje ,t>gets1 m9+1 #cdi ,telemet]s1 #ebh ,telescope3 g5]al description (1 #bd ,kepl]'s1 ,galileo's1 #dj body (1 #dg ,telescope3 optical arrangem5ts1 #dg optical pr9ciples1 #be qualities1 #ef reconnoitr+1 #ehb ,telescopic pocket level1 #adc ,t5sion h&les = /eel b&s1 #ejc ,!odolites1 #bad adju/m5t1 #bgf adju/able axis1 #bcg1 #bdh ,deville's1 #bfc ,ev]e/'s1 #bga micromet]1 #bei m\nta91 #beh pla91 #bfe1 #bfg railway1 #beh simple con/ruction1 #bge sol> atta*m5t to1 #bci ,s\t]ra9 #cdh ,/anley's1 #bdg transit1 #bae1 #bca1 #bdg #ad-;in*1 #bie #cf-;in* ,colonel ,/range's1 #bih ,univ]sal1 #bfe ,!rmomet] = /eel b&1 #ejc boil+ po9t1 #efi ,timb] gir? /rap1 #egi m>k+ knife1 #eha rods1 #ehb ,tools us$ 9 manufacture ( in/rum5ts1 #aa ,triangle = levell+ /aff1 #afb ,tribra* adju/m5ts1 #abf ,ev]e/'s1 #bgb ) me*anical /age1 #bea ,tripods1 #aad1 #bag1 #cbb fram$1 #bej m9]s'1 #cac ,tripods1 jo9t$1 = m9+ in/rum5ts1 #cac ,tr\gh compass1 #gd1 #hc1 #bcf ,v]ni] scale read+s1 #ahj ,vicat ne$le1 #ehf ,vice = adju/+ l& *a91 #dif ,wat] levels1 #adf ,wat]pro( cov]s1 #bc ,watk9's an]oid1 #efg ,watk9's cl9omet]1 #dag ,wealemefna1 #ehg ,webs1 collect+ & m\nt+1 #ea ,:i/les1 #ehe ,y-levels1 #ih improv$ con/ruction1 #ajg ,illu/ration3 ,,wire ,,up ,,y\r ,,own ,,h\se ,h ,electric ,,light ,,heat ,,p[] ,?is ,book ,,wir+ ,,h\ses--,,s*neid] ,%[s y 9 detail h[ to in/all electric wires4 ,read ! 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