,transcrib]'s ,notes3 ,und]scores 80 be=e & aft] a ^w or phrase indicate italics 9 ! orig9al text4 ,equal signs 80 be=e & aft] a ^w or phrase indicate bold 9 ! orig9al text4 ,small capitals h be5 conv]t$ to ,,solid capitals4 ,illu/rations & footnotes h be5 mov$ s !y d n break up p>agraphs4 ,antiquat$ spell+s h be5 pres]v$4 ,typographical & punctuation errors h be5 sil5tly correct$4 ,9 ! ,table ( ,cont5ts1 ,*apt]s ,,xv & ,,xvi 7 correct$ f page #bjj to #baa & #baf respectively4 ,figure #df 0 incorrectly labell$ ,figure #de1 ?is has be5 correct$4 ,,! ,,/]eoscope ,,its ,,hi/ory1 ,,!ory1 ,,& ,,con/ruction ,,) ,,its ,,application ,,to ,,! ,,f9e ,,& ,,useful ,,arts ,,& ,,to ,,education4 ,,by ,,sir ,,david ,,brew/]1 ,k4,h41 ,d4,c4,l41 ,f4,r4,s41 ,m4,r4,i4,a41 ,,vice-,,presid5t ,,( ,,! ,,royal ,,society ,,( ,,ed9burgh1 ,,"o ,,( ,,! ,,eight ,,associates ,,( ,,! ,,imp]ial ,,in/itute ,,( ,,france1 ,,(fic] ,,( ,,! ,,legion ,,( ,,hon\r1 ,,*evali] ,,( ,,! ,,prussian ,,ord] ,,( ,,m]it1 ,,honor>y ,,or ,,correspond+ ,,memb] ,,( ,,! ,,academies ,,( ,,pet]sburgh1 ,,vi5na1 ,,b]l91 ,,cop5hag51 ,,/ockholm1 ,,brussels1 ,g,,tt+51 ,,mod5a1 ,,& ,,( ,,! ,,national ,,in/itute ,,( ,,wa%+ton1 ,,etc4 ,,) ,,fifty ,,wood ,,engrav+s4 ,,london3 ,,john ,,murray1 ,,albem>le ,,/reet4 #ahef4 ,! ,"r ( ,translation is res]v$4 ,,ed9burgh3 ,t4 ,,con/able1 ,,pr9t] ,,to ,,h] ,,maje/y4 ,,cont5ts ,,page ,,introduction1 #a ,,*ap4 ,i4--,,hi/ory ,,( ,,! ,,/]eoscope1 #e ,,ii4--,,on ,,monocul> ,,vision1 ,,or ,,vision ,,) ,,"o ,,eye1 #ch ,,iii4--,,on ,,b9ocul> ,,vision1 ,,or ,,vision ,,) ,,two ,,eyes1 #dg ,,iv4--,,description ,,( ,,! ,,ocul>1 ,,reflect+1 ,,& ,,l5ticul> ,,/]eoscopes1 #ec ,v4--,,on ,,! ,,!ory ,,( ,,! ,,/]eoscopic ,,vision1 #gf ,,vi4--,,on ,,! ,,union ,,( ,,simil> ,,pictures ,,9 ,,b9ocul> ,,vision1 #ij ,,vii4--,,description ,,( ,,diff]5t ,,/]eoscopes1 #ajg ,,viii4--,,me?od ,,( ,,tak+ ,,pictures ,,= ,,! ,,/]eoscope1 #aca ,,ix4--,,on ,,! ,,adaptation ,,( ,,! ,,pictures ,,to ,,! ,,/]eoscope4--,,_! ,,size1 ,,position1 ,,& ,,illum9ation1 #aei ,x4--,,application ,,( ,,! ,,/]eoscope ,,to ,,pa9t+1 #aff ,,xi4--,,application ,,( ,,! ,,/]eoscope ,,to ,,sculpture1 ,,ar*itecture1 ,,& ,,eng9e]+1 #ahc ,,xii4--,,application ,,( ,,! ,,/]eoscope ,,to ,,natural ,,hi/ory1 #ahi ,,xiii4--,,application ,,( ,,! ,,/]eoscope ,,to ,,educational ,,purposes1 #aic ,,xiv4--,,application ,,( ,,! ,,/]eoscope ,,to ,,purposes ,,( ,,amusem5t1 #bjd ,,xv4--,,on ,,! ,,production ,,( ,,/]eoscopic ,,pictures ,,f ,a ,,s+le ,,picture1 #baa ,,xvi4--,,on ,,c]ta9 ,,fallacies ,,( ,,sight ,,9 ,,! ,,vision ,,( ,,solid ,,bodies1 #baf ,,xvii4--,,on ,,c]ta9 ,,difficulties ,,exp]i5c$ ,,9 ,,! ,,use ,,( ,,! ,,/]eoscope1 #bca ,,on ,,! ,,/]eoscope4 ,,introduction4 ,! ,/]eoscope1 a ^w d]iv$ f 1 solid1 & 1 to see1 is an optical in/rum5t1 ( mod]n inv5tion1 = repres5t+1 9 app>5t relief & solidity1 all natural objects & all gr\ps or comb9ations ( objects1 by unit+ into "o image two plane repres5tations ( ^! objects or gr\ps z se5 by ea* eye sep>ately4 ,9 its mo/ g5]al =m ! ,/]eoscope is a b9ocul> in/rum5t1 t is1 is appli$ to bo? eyes2 b 9 two ( its =ms x is monocul>1 or appli$ only to "o eye1 ?\gh ! use ( ! o!r eye1 )\t any in/rum5tal aid1 is necess>y 9 ! comb9ation ( ! two plane pictures1 or ( "o plane picture & its reflect$ image4 ,! ,/]eoscope1 !re=e1 _c1 l ! telescope & microscope1 be us$ by p]sons :o h lo/ ! use ( "o eye1 & its rem>kable effects _c be prop]ly appreciat$ by ^? ^: eyes are n equally good4 ,:5 ! arti/ repres5ts liv+ objects1 or gr\ps ( !m1 & del9eates build+s or l&scapes1 or :5 he copies f /atues or models1 he produces app>5t solidity1 & diff]5ce ( di/ance f ! eye1 by light & %ade1 by ! dim9i%$ size ( kn[n objects z regulat$ by ! pr9ciples ( geometrical p]spective1 & by ^? v>iations 9 di/9ctness & col\r :i* con/itute :at has be5 call$ a]ial p]spective4 ,b :5 all ^! appliances h be5 us$ 9 ! mo/ skilful mann]1 & art has exhau/$ its p[]s1 we seldom1 if ev]1 mi/ake ! plane picture = ! solid :i* x repres5ts4 ,! two eyes scan its surface1 & by _! di/ance-giv+ p[] indicate to ! obs]v] t e po9t ( ! picture is ne>ly at ! same di/ance f 8 eye4 ,b if ! obs]v] closes "o eye1 & ?us deprives himself ( ! p[] ( det]m9+ diff]5ces ( di/ance by ! conv]g5cy ( ! optical axes1 ! relief ( ! picture is increas$4 ,:5 ! pictures are tru?ful photographs1 9 :i* ! v>iations ( light & %ade are p]fectly repres5t$1 a v consid]able degree ( relief & solidity is ?us obta9$2 & :5 we h practis$ = a :ile ?is species ( monocul> vision1 ! draw+1 :e!r x be ( a /atue1 a liv+ figure1 or a build+1 w appe> to rise 9 its diff]5t p>ts f ! canvas1 ?\gh only to a limit$ ext5t4 ,9 ^! obs]vations we ref] *iefly to ord9>y draw+s held 9 ! h&1 or to portraits & l&scapes hung 9 rooms & gall]ies1 :]e ! proximity ( ! obs]v]1 & lights f v>i\s directions1 reveal ! surface ( ! pap] or ! canvas2 = 9 panoramic & dioramic repres5tations1 :]e ! light1 conceal$ f ! obs]v]1 is introduc$ 9 an oblique direction1 & :]e ! di/ance ( ! picture is su* t ! conv]g5cy ( ! optic axes loses mu* ( its di/ance-giv+ p[]1 ! illusion is v p]fect1 especially :5 aid$ by correct geometrical & a]ial p]spective4 ,b :5 ! panorama is illum9at$ by light f v>i\s directions1 & ! slighte/ motion imp>t$ to ! canvas1 its surface becomes di/9ctly visible1 & ! illusion in/antly disappe>s4 ,! effects ( /]eoscopic repres5tation are ( a v diff]5t k9d1 & are produc$ by a v diff]5t cause4 ,! s+ul> relief :i* x imp>ts is indep5d5t ( light & %ade1 & ( geometrical z well z ( a]ial p]spective4 ,^! important accessories1 s necess>y 9 ! visual p]ception ( ! draw+s 9 plano1 avail no?+ 9 ! evolution ( _! relievo1 or ?ird dim5sion4 ,!y add1 d\btless1 to ! beauty ( ! b9ocul> pictures2 b ! /]eoscopic creation is due solely to ! sup]position ( ! two plane pictures by ! optical app>atus employ$1 & to ! di/9ct & in/antane\s p]ception ( di/ance by ! conv]g5cy ( ! optic axes ^u ! simil> po9ts ( ! two pictures :i* ! /]eoscope has unit$4 ,if we close "o eye :ile look+ at photographic pictures 9 ! /]eoscope1 ! p]ception ( relief is /ill consid]able1 & approximates to ! b9ocul> repres5tation2 b :5 ! pictures are m]e diagrams consi/+ ( :ite l9es ^u a black gr\nd1 or black l9es ^u a :ite gr\nd1 ! relief is in/antly lo/ by ! %utt+ ( ! eye1 & x is only ) su* b9ocul> pictures t we see ! true p[] ( ! /]eoscope4 ,z an amus+ & useful in/rum5t ! /]eoscope d]ives mu* ( its value f photography4 ,! mo/ skilful arti/ w\ld h be5 incapable ( del9eat+ two equal repres5tations ( a figure or a l&scape z se5 by two eyes1 or z view$ f two diff]5t po9ts ( sight2 b ! b9ocul> cam]a1 :5 rightly con/ruct$1 enables u to produce & to multiply photographically ! pictures :i* we require1 ) all ! p]fection ( t int]e/+ art4 ,) ?is in/rum5t1 inde$1 ev5 be=e ! inv5tion ( ! ,dagu]reotype & ! ,talbotype1 we might h exhibit$ tempor>ily ^u gr\nd-glass1 or susp5d$ 9 ! air1 ! mo/ p]fect /]eoscopic creations1 by plac+ a ,/]eoscope beh9d ! two dissimil> pictures =m$ by ! cam]a4 ,,*apt] ,i4 ,,hi/ory ,,( ,,! ,,/]eoscope4 ,:5 we look ) bo? eyes op5 at a sph]e1 or any o!r solid object1 we see x by unit+ into "o two pictures1 "o z se5 by ! "r1 & ! o!r z se5 by ! left eye4 ,if we hold up a ?9 book p]p5dicul>ly1 & midway betwe5 bo? eyes1 we see di/9ctly ! back ( x & bo? sides ) ! eyes op54 ,:5 we %ut ! "r eye we see ) ! left eye ! back ( ! book & ! left side ( x1 & :5 we %ut ! left eye we see ) ! "r eye ! back ( x & ! "r side4 ,! picture ( ! book1 !re=e1 :i* we see ) bo? eyes1 consi/s ( two dissimil> pictures unit$1 namely1 a picture ( ! back & ! left side ( ! book z se5 by ! left eye1 & a picture ( ! back & "r side ( ! book z se5 by ! "r eye4 ,9 ?is exp]im5t ) ! book1 & 9 all cases :]e ! object is ne> ! eye1 we n only see diff]5t pictures ( ! same object1 b we see diff]5t ?+s ) ea* eye4 ,^? :o we> spectacles see only ! left-h& spectacle-glass ) ! left eye1 on ! left side ( ! face1 :ile ) ! "r eye !y see only ! "r-h& spectacle-glass on ! "r side ( ! face1 bo? glasses ( ! spectacles be+ se5 unit$ midway betwe5 ! eyes1 or above ! nose1 :5 bo? eyes are op54 ,x is1 !re=e1 a fact well kn[n to e p]son ( common sagacity t ! pictures ( bodies se5 by bo? eyes are =m$ by ! union ( two dissimil> pictures =m$ by ea*4 ,?is palpable tru? 0 kn[n & publi%$ by anci5t ma!maticians4 ,euclid knew x m ?an two ?\s& ye>s ago1 z may be se5 9 ! #bf?1 #bg?1 & #bh? !orems ( 8 ,treatise on ,optics4#a ,9 ^! !orems he %ews t ! "p ( a sph]e se5 by bo? eyes1 & hav+ its diamet] equal to1 or great] or less ?an ! di/ance betwe5 ! eyes1 is equal to1 & great] or less ?an a hemisph]e2 & hav+ previ\sly %ewn 9 ! #bc;d & #bd? !orems h[ to f9d ! "p ( any sph]e t is se5 by "o eye at diff]5t di/ances1 x foll[s1 f con/ruct+ 8 figure1 t ea* eye sees diff]5t portions ( ! sph]e1 & t x is se5 by bo? eyes by ! union ( ^! two dissimil> pictures4 #a ,edit4 ( ,p5a1 pp4 #ag1 #ah1 ,p>is1 #aegg2 or ,op]a1 by ,gregory1 pp4 #fai1 #fbj4 ,oxon4 #agjc4 ,m ?an fifte5 hundr$ ye>s ago1 ! celebrat$ physician ,gal5 treat$ ! subject ( b9ocul> vision m fully ?an ,euclid4 ,9 ! twelf? *apt] ( ! t5? book ( 8 "w1 ,on ! use ( ! diff]5t p>ts ( ! ,human ,body1 he has describ$ ) great m9ut5ess ! v>i\s ph5om5a :i* are se5 :5 we look at bodies ) bo? eyes1 & alt]nately ) ! "r & ! left4 ,he %ews1 by diagrams1 t dissimil> pictures ( a body are se5 9 ea* ( ^! ?ree modes ( view+ x2 &1 aft] f9i%+ 8 demon/ration1 he adds1-- 8,b if any p]son does n und]/& ^! demon/rations by means ( l9es1 he w f9ally give 8 ass5t to !m :5 he has made ! foll[+ exp]im5t3--,/&+ ne> a column1 & %utt+ ea* ( ! eyes 9 succession2--:5 ! "r eye is %ut1 "s ( ^? p>ts ( ! column :i* 7 previ\sly se5 by ! "r eye on ! "r side ( ! column1 w n n[ be se5 by ! left eye2 & :5 ! left eye is %ut1 "s ( ^? p>ts :i* 7 =m]ly se5 by ! left eye on ! left side ( ! column1 w n n[ be se5 by ! "r eye4 ,b :5 we1 at ! same "t1 op5 bo? eyes1 bo? ^! w be se51 = a great] "p is conceal$ :5 we look ) ei!r ( ! two eyes1 ?an :5 we look ) bo? at ! same "t40#b #b ,de ,usu ,p>tium ,corporis ,humani1 edit4 ,lugduni1 #aeej1 p4 #eic4 ,9 su* di/9ct & unambigu\s t]ms1 intelligible to ! meane/ capacity1 does ?is illu/ri\s writ] ann\nce ! fundam5tal law ( b9ocul> vision--! gr& pr9ciple ( ! ,/]eoscope1 namely1 t ! picture ( ! solid column :i* we see ) bo? eyes is compos$ ( two dissimil> pictures1 z se5 by ea* eye sep>ately4 ,z ! vision ( ! solid column1 !re=e1 0 obta9$ by ! union ( ^! dissimil> pictures1 an in/rum5t only 0 want$ to take su* pictures1 & ano!r to comb9e !m4 ,! ,b9ocul> ,photographic ,cam]a 0 ! "o in/rum5t1 & ! ,/]eoscope ! o!r4 ,! subject ( b9ocul> vision 0 /udi$ by v>i\s optical writ]s :o h fl\ri%$ s9ce ! "t ( ,gal54 ,bapti/a ,porta1 "o ( ! mo/ em95t ( !m1 repeats1 9 8 "w ,on ,refraction1 ! propositions ( ,euclid on ! vision ( a sph]e ) "o & bo? eyes1 & he cites f ,gal5 ! v passage :i* we h giv5 above on ! dissimil>ity ( ! ?ree pictures se5 by ea* eye & by bo?4 ,believ+ t we see only ) "o eye at a "t1 he d5ies ! accuracy ( ,euclid's !orems1 & :ile he admits ! correctness ( ! obs]vations ( ,gal51 he endeav\rs to expla9 !m ^u o!r pr9ciples4 ,illu/ration3 ,,fig4 #a4 ,9 illu/rat+ ! views ( ,gal5 on ! dissimil>ity ( ! ?ree pictures :i* are requisite 9 b9ocul> vision1 he employs a mu* m di/9ct diagram ?an t :i* is giv5 by ! ,greek physician4 8,let ,a10 he says1 8be ! pupil ( ! "r eye1 ,b t ( ! left1 & ,,dc ! body to be se54 ,:5 we look at ! object ) bo? eyes we see ,,dc1 :ile ) ! left eye we see ,,ef1 & ) ! "r eye ,,gh4 ,b if x is se5 ) "o eye1 x w be se5 o!rwise1 = :5 ! left eye ,b is %ut1 ! body ,,cd1 on ! left side1 w be se5 9 ,,hg2 b :5 ! "r eye is %ut1 ! body ,,cd w be se5 9 ,,fe1 :]eas1 :5 bo? eyes are op5$ at ! same "t1 x w be se5 9 ,,cd40 ,^! results are !n expla9$ by copy+ ! passage f ,gal51 9 :i* he supposes ! obs]v] to repeat ^! exp]im5ts :5 he is look+ at a solid column4 ,9 look+ at ?is diagram1 we recognise at once n only ! pr9ciple1 b ! con/ruction ( ! /]eoscope4 ,! d\ble /]eoscopic picture or slide is repres5t$ by ,,he2 ! "r-h& picture1 or ! "o se5 by ! "r eye1 by ,,hf2 ! left-h& picture1 or ! "o se5 by ! left eye1 by ,,ge2 & ! picture ( ! solid column 9 full relief by ,,dc1 z produc$ midway betwe5 ! o!r two dissimil> pictures1 ,,hf & ,,ge1 by _! union1 precisely z 9 ! /]eoscope4#c #c ,joan4 ,bapti/ ,port ,neap41 ,de ,refractione ,optices p>te1 lib4 v4 p4 #acb1 & lib4 vi4 pp4 #adc-e4 ,neap4 #aeic4 ,gal51 !re=e1 & ! ,neapolitan philosoph]1 :o has employ$ a m di/9ct diagram1 c]ta9ly knew & adopt$ ! fundam5tal pr9ciple ( ! /]eoscope2 & no?+ m 0 requir$1 = produc+ pictures 9 full relief1 ?an a simple in/rum5t = unit+ ,,hf & ,,ge1 ! "r & left h& dissimil> pictures ( ! column4 ,illu/ration3 ,,fig4 #b4 ,9 ! treatise on pa9t+ :i* he left beh9d him 9 ,,ms41#d ,leon>do da ,v9ci has made a di/9ct ref]5ce to ! dissimil>ity ( ! pictures se5 by ea* eye z ! reason :y 8a pa9t+1 ?\gh conduct$ ) ! greate/ art1 & f9i%$ to ! la/ p]fection1 bo? ) reg>d to its cont\rs1 its lights1 its %ad[s1 & its col\rs1 c nev] %ew a relievo equal to t ( ! natural objects1 unless ^! be view$ at a di/ance & ) a s+le eye10#e :i* he ?us demon/rates4 8,if an object ,c be view$ by a s+le eye at ,a1 all objects 9 ! space beh9d x--includ$1 z x 71 9 a %ad[ ,,ecf1 ca/ by a c&le at ,a--are invisible to an eye at ,a2 b :5 ! o!r eye at ,b is op5$1 "p ( ^! objects become visible to x2 ^? only be+ hid f bo? eyes t are includ$1 z x 71 9 ! d\ble %ad[ ,,cd1 ca/ by two lights at ,a & ,b & t]m9at$ 9 ,d2 ! angul> space ,,edg1 beyond ,d1 be+ always visible to bo? eyes4 ,& ! hidd5 space ,,cd is s mu* ! %ort] z ! object ,c is small] & ne>] to ! eyes4 ,?us he obs]ves t ! object ,c1 se5 ) bo? eyes1 becomes1 z x 71 transp>5t1 accord+ to ! usual def9ition ( a transp>5t ?+1 namely1 t :i* hides no?+ beyond x4 ,b ?is _c happ5 :5 an object1 ^: bread? is bigg] ?an t ( ! pupil1 is view$ by a s+le eye4 ,! tru? ( ?is obs]vation is1 !re=e1 evid5t1 because a pa9t$ figure int]cepts all ! space beh9d its app>5t place1 s z to preclude ! eyes f ! sight ( e "p ( ! imag9>y gr\nd beh9d x4 ,h5ce10 cont9ues ,dr4 ,smi?1 8we h "o help to di/+ui% ! place ( a ne> object m accurately ) bo? eyes ?an ) "o1 inasmu* z we see x m deta*$ f o!r objects beyond x1 & m ( its own surface1 especially if x be r\ndi%40 #d ,trattata della ,pictura1 ,scultura1 ed ,ar*itettura4 ,milan1 #aehd4 #e ,dr4 ,smi?'s ,compleat ,sy/em ( ,opticks1 vol4 ii41 ,rem>ks1 pp4 #da & #bdd4 ,we h quot$ ?is passage1 n f its prov+ t ,leon>do da ,v9ci 0 acqua9t$ ) ! fact t ea* eye1 ,a1 ,b1 sees dissimil> pictures ( ! sph]e ,c1 b because x has be5 ref]r$ to by ,mr4 ,:eat/one z ! only rem>k on ! subject ( b9ocul> vision :i* he c\ld f9d 8aft] look+ ov] ! works ( _m au?ors :o might be expect$ to h made !m40 ,we ?9k x q cle>1 h[ev]1 t ! ,italian arti/ knew z well z 8 comm5tator ,dr4 ,smi?1 t ea* eye1 ,a & ,b1 sees dissimil> p>ts ( ! sph]e ,c4 ,x 0 n 8 purpose to treat ( ! b9ocul> pictures ( ,c1 b 8 figure proves _! dissimil>ity4 ,! subject ( b9ocul> vision 0 successfully /udi$ by ,francis ,aguillon or ,aguilonius1#f a le>n$ ,jesuit1 :o publi%$ 8 ,optics 9 #afac4 ,9 ! fir/ book ( 8 "w1 :]e he is treat+ ( ! vision ( solids ( all =ms1 7de g5]e illorum qu ta /]ea nuncupantur17 he has "s difficulty 9 expla9+1 & fails to d x1 :y ! two dissimil> pictures ( a solid1 se5 by ea* eye1 d n1 :5 unit$1 give a confus$ & imp]fect view ( x4 ,?is discussion is app5d$ to ! demon/ration ( ! !orem1 8t :5 an object is se5 ) two eyes1 two optical pyramids are =m$ ^: common base is ! object itself1 & ^: v]tices are 9 ! eyes10#g & is z foll[s3-- #f ,opticorum ,libri ,sex ,philosophis juxta ac ,ma!maticis utiles4 ,folio4 ,antv]pi1 #afac4 #g ,9 ,,fig4 #a1 ,,ahf is ! optical pyramid se5 by ! eye ,a1 & ,,bge ! optical pyramid se5 by ! eye ,b4 8,:5 "o object is se5 ) two eyes1 ! angles at ! v]tices ( ! optical pyramids 7namely1 ,,haf1 ,,gbe1 ,fig4 #a7 are n always equal1 = beside ! direct view 9 :i* ! pyramids ought to be equal1 into :atev] direction bo? eyes are turn$1 !y receive pictures ( ! object "u inequal angles1 ! greate/ ( :i* is t :i* is t]m9at$ at ! ne>] eye1 & ! less] t :i* reg>ds ! remot] eye4 ,?is1 ,i ?9k1 is p]fectly evid5t2 b ,i consid] x z wor?y ( admiration1 h[ x happ5s t bodies se5 by bo? eyes are n all confus$ & %apeless1 ?\gh we view !m by ! optical axes fix$ on ! bodies !mselves4 ,= great] bodies1 se5 "u great] angles1 appe> less] bodies "u less] angles4 ,if1 !re=e1 "o & ! same body :i* is 9 reality great] ) "o eye1 is se5 less on acc\nt ( ! inequality ( ! angles 9 :i* ! pyramids are t]m9at$1 7namely1 ,,haf1 ,,gbe1#h7 ! body itself mu/ assur$ly be se5 great] or less at ! same "t1 & to ! same p]son t views x2 &1 !re=e1 s9ce ! images 9 ea* eye are dissimil> 7m9ime sibi congruunt7 ! repres5tation ( ! object mu/ appe> confus$ & di/urb$ 7confusa ac p]turbata7 to ! prim>y s5se40 #h ,^! angles are equal 9 ?is diagram & 9 ! vision ( a sph]e1 b !y are inequal 9 o!r bodies4 8,?is view ( ! subject10 he cont9ues1 8is c]ta9ly consi/5t ) reason1 b1 :at is truly wond]ful is1 t x is n correct1 = bodies are se5 cle>ly & di/9ctly ) bo? eyes :5 ! optic axes are conv]g$ ^u !m4 ,! reason ( ?is1 ,i ?9k1 is1 t ! bodies d n appe> to be s+le1 because ! app>5t images1 :i* are =m$ f ea* ( !m 9 sep>ate eyes1 exactly coalesce1 7sibi mutuo exacte congruunt17 b because ! common s5se imp>ts its aid equally to ea* eye1 ex]t+ its own p[] equally 9 ! same mann] z ! eyes are conv]g$ by means ( _! optical axes4 ,:atev] body1 !re=e1 ea* eye sees ) ! eyes conjo9$1 ! common s5se makes a s+le notion1 n compos$ ( ! two :i* belong to ea* eye1 b belong+ & accommodat$ to ! imag9ative faculty to :i* x 7! common s5se7 assigns x4 ,?\gh1 !re=e1 ! angles ( ! optical pyramids :i* proce$ f ! same object to ! two eyes1 view+ x obliquely1 are inequal1 & ?\gh ! object appe>s great] to "o eye & less to ! o!r1 yet ! same diff]5ce does n pass into ! prim>y s5se if ! vision is made only by ! axes1 z we h said1 b if ! axes are conv]g$ on ?is side or on ! o!r side ( ! body1 ! image ( ! same body w be se5 d\ble1 z we %all %ew 9 ,book iv41 on ! fallacies ( vision1 & ! "o image w appe> great] & ! o!r less on acc\nt ( ! inequality ( ! angles "u :i* !y are se540#i #i ,aguilonius1 ,opticorum1 lib4 ii4 book xxxviii4 pp4 #adj1 #ada4 ,su* is ,aguilonius's !ory ( b9ocul> vision1 & ( ! union ( ! two dissimil> pictures 9 ea* eye by :i* a solid body is se54 ,x is obvi\sly m correct ?an t ( ,dr4 ,:ewell & ,mr4 ,:eat/one4 ,aguilonius affirms x to be contr>y to reason t two dissimil> pictures c be unit$ into a cle> & di/9ct picture1 z !y are actually f\nd to be1 & he is !re=e driv5 to call 9 ! aid ( :at does n exi/1 a common s5se1 :i* rectifies ! picture4 ,dr4 ,:ewell & ,mr4 ,:eat/one h cut ! ,gordian knot by ma9ta9+ :at is impossible1 t 9 b9ocul> & /]eoscopic vision a long l9e is made to co9cide ) a %ort "o1 & a l>ge surface ) a small "o2 & 9 place ( conceiv+ ?is to be done by a common s5se ov]rul+ optical laws1 z ,aguilonius supposes1 !y give to ! t5d] & pulpy ret9a1 ! recipi5t ( ocul> pictures1 ! /range p[] ( contract+ or exp&+ itself 9 ord] to equalize inequal l9es & inequal surfaces6 ,illu/ration3 ,,fig4 #c4 ,9 8 f\r? & v int]e/+ book1 on ! fallacies ( di/ance1 magnitude1 position1 & figure1 ,aguilonius resumes ! subject ( ! vision ( solid bodies4 ,he repeats ! !orems ( ,euclid & ,gass5di on ! vision ( ! sph]e1 %ew+ h[ mu* ( x is se5 by ea* eye1 & by bo?1 :atev] be ! size ( ! sph]e1 & ! di/ance ( ! obs]v]4 ,at ! end ( ! !orems1 9 :i* he demon/rates t :5 ! diamet] ( ! sph]e is equal to ! di/ance betwe5 ! eyes we see exactly a hemisph]e1 he gives ! annex$ draw+ ( ! mode 9 :i* ! sph]e is se5 by ea* eye1 & by bo?4 ,9 ?is diagram ,e is ! "r eye & ,d ! left1 ,,*fi ! section ( t "p ( ! sph]e ,,bc :i* is se5 by ! "r eye ,e1 ,,bhga ! section ( ! "p :i* is se5 by ! left eye ,d1 & ,,blc ! half ( ! great circle :i* is ! section ( ! sph]e z se5 by bo? eyes4#aj ,^! ?ree pictures ( ! solids are all dissimil>4 ,! "r eye ,e does n see ! "p ,,blcif ( ! sph]e2 ! left eye does n see ! "p ,,blcga1 :ile ! "p se5 ) bo? eyes is ! hemisph]e ,,blcgf1 ! dissimil> segm5ts ,,bfg1 ,,cgf be+ unit$ 9 its vision4#aa ,aft] demon/rat+ 8 !orems on ! vision ( sph]es ) "o & bo? eyes1#ab ,aguilonius in=ms u1 be=e he proce$s to ! vision ( cyl9d]s1 t x is agre$ ^u t x is n m]ely true ) ! sph]e1 b also ) ! cyl9d]1 ! cone1 & all bodies :atev]1 t ! "p :i* is se5 is compreh5d$ by tang5t rays1 su* z ,,eb1 ,,ec = ! "r eye1 9 ,fig4 #c4 8,=10 says he1 8s9ce ^! tang5t l9es are ! out]mo/ ( all ^? :i* c be drawn to ! propos$ body f ! same po9t1 namely1 t 9 :i* ! eye is und]/ood to be plac$1 x cle>ly foll[s t ! "p ( ! body :i* is se5 mu/ be conta9$ by ! rays t\*+ x on all sides4 ,= 9 ?is "p no po9t c be f\nd f :i* a "r l9e _c be drawn to ! eye1 by :i* ! correct visible =m is br\ght out40#ac #aj ,x is obvi\s t a complete hemisph]e is n se5 ) bo? eyes4 #aa ,aguilonius1 ,opticorum1 lib4 iv4 pp4 #cjf1 #cjg4 #ab ,9 ! la/ ( ^! !orems ,aguilonius describes & expla9s1 we believe = ! fir/ "t1 ! conv]sion ( relief 9 ! vision ( convex & concave surfaces4 ,see ,prop4 xciv4 p4 #cab4 #ac ,id41 p4 #cac4 ,optical writ]s :o liv$ aft] ! "t ( ,aguilonius seem to h consid]$ ! subject ( b9ocul> vision z exhau/$ 9 8 admirable "w4 ,gass5di1#ad ?\gh he treats ! subject v slightly1 & )\t any figures1 tells u t we see ! left side ( ! nose ) ! left eye1 & ! "r side ( x ) ! "r eye1--two pictures suffici5tly dissimil>4 ,&rew ,tacquet1#ae ?\gh he quotes ,aguilonius & ,gass5di on ! subject ( see+ di/ances ) bo? eyes1 says no?+ on ! b9ocul> vision ( solids2 & ,smi?1 ,h>ris1 & ,port]field1 only t\* ^u ! subject incid5tally4 ,9 comm5t+ on ! passage :i* we h already quot$ f ,leon>do da ,v9ci1 ,dr4 ,smi? says1 8,h5ce we h "o help to di/+ui% ! place ( a ne> object m accurately ) bo? eyes ?an ) "o1 inasmu* z we see x m deta*$ f o!r objects beyond x1 & m ( its own surface1 especially if x be r\ndi%40#af ,if any f>!r evid5ce 7 requir$ t ,dr4 ,smi? 0 acqua9t$ ) ! dissimil>ity ( ! images ( a solid se5 by ea* eye1 x w be f\nd 9 8 exp]im5t ) a 8long rul] plac$ betwe5 ! eyebr[s1 & ext5d$ directly =w>d ) its flat sides1 respect+ ! "r h& & ! left40 8,by direct+ ! eyes to a remote object10 he adds1 8! "r side ( ! rul] se5 by ! "r eye w appe> on ! left h&1 & ! left side on ! "r h&1 z repres5t$ 9 ! figure40#ag #ad ,op]a1 tom4 ii4 p4 #cid4 ,lugduni1 #afeh4 #ae ,op]a ,ma!matica ,optica1 tribus libris exposita1 p4 #acf4 #af ,opticks1 vol4 ii41 ,rem>ks1 pp4 #da & #bde4 #ag ,id41 vol4 i4 p4 #dh1 ,fig4 #aif4 ,9 8 ,treatise on ,optics1 publi%$ 9 #agge1 ,mr4 ,h>ris1 :5 speak+ ( ! visible or app>5t figures ( objects1 obs]ves1 t 8we h o!r helps = di/+ui%+ prom95ces ( small p>ts besides ^? by :i* we di/+ui% di/ances 9 g5]al1 z _! degrees ( light & %ade1 & ! prospect we h r\nd !m40 ,& by ! p>allax1 on acc\nt ( ! di/ance betwixt our eyes1 we c di/+ui% besides ! front "p ( ! two sides ( a ne> object n ?ick] ?an ! said di/ance1 & ?is gives a visible relievo to su* objects1 :i* helps greatly to raise or deta* !m f ! plane 9 :i* !y lie4 ,?us ! nose on a face is ! m rem>kably rais$ by our see+ bo? sides ( x at once48#ah ,t is1 ! relievo is produc$ by ! comb9ation ( ! two dissimil> pictures giv5 by ea* eye4 ,)\t ref]r+ to a figure giv5 by ,dr4 ,port]field1 9 :i* he actually gives draw+s ( an object z se5 by ea* eye 9 b9ocul> vision1#ai ! "o exhibit+ ! object z se5 endwise by ! "r eye1 & ! o!r ! same object z se5 lat]ally by ! left eye1 we may appeal to ! exp]i5ce ( e optical1 or ev5 ( e ord9>y obs]v]1 9 support ( ! fact1 t ! dissimil>ity ( ! pictures 9 ea* eye1 by :i* we see solid objects1 is kn[n to ^? :o h nev] read x 9 ,gal51 ,porta1 or ,aguilonius4 ,:o has n obs]v$ ! fact m5tion$ by ,gass5di & ,h>ris1 t _! left eye sees only ! left side ( _! nose1 & _! "r eye ! "r side1 two pictures suffici5tly dissimil>8 ,:o has n notic$1 z well z ,dr4 ,smi?1 t :5 !y look at any ?91 flat body1 su* z a ?9 book1 !y see bo? sides ( x--! left eye only ! left side ( x1 & ! "r eye only ! "r side1 :ile ! back1 or ! "p ne>e/ ! face1 is se5 by ea* eye1 & bo? ! sides & ! back by bo? ! eyes8 ,:at /ud5t ( p]spective is !re--ma/] or pupil1 male or female--:o does n "k1 z c]ta9ly z he kn[s 8 alphabet1 t ! picture ( a *air or table1 or any?+ else1 drawn f "o po9t ( sight1 or z se5 by "o eye plac$ 9 t po9t1 is necess>ily dissimil> to ano!r draw+ ( ! same object tak5 f ano!r po9t ( sight1 or z se5 by ! o!r eye plac$ 9 a po9t #b in*es di/ant f ! fir/8 ,if su* a p]son is to be f\nd1 we might !n admit t ! dissimil>ity ( ! pictures 9 ea* eye 0 n kn[n to e /ud5t ( p]spective4#bj #ah ,treatise on ,optics1 p4 #aga2 see also sect4 #fd1 p4 #aac4 #ai ,treatise on ! ,eye1 vol i4 p4 #dab1 ,plate #e1 ,fig4 #cg4 #bj ,z ,mr4 ,:eat/one himself describes ! dissimil> pictures or draw+s z 8two diff]5t projections ( ! same object se5 f two po9ts ( sight1 ! di/ance betwe5 :i* is equal to ! int]val betwe5 ! eyes ( ! obs]v]10 x is inconceivable on :at gr\nd he c\ld imag9e himself to be ! discov]] ( s palpable & notori\s a fact z t ! pictures ( a body se5 by two eyes--two po9ts ( sight1 mu/ be dissimil>4 ,su* 0 ! /ate ( our k ( b9ocul> vision :5 two individuals1 ,mr4 ,:eat/one1 & ,mr4 ,elliot1 n[ ,tea*] ( ,ma!matics 9 ,ed9burgh1 7 direct+ _! att5tion to ! subject4 ,mr4 ,:eat/one communicat$ an important pap] on ! ,physiology ( ,vision to ! ,briti% ,association at ,newca/le 9 ,augu/ #ahch1 & exhibit$ an in/rum5t call$ a ,/]eoscope1 by :i* he unit$ ! two dissimil> pictures ( solid bodies1 ! 1 7ta /]ea ( ,aguilonius17 & ?us reproduc$1 z x 71 ! bodies !mselves4 ,mr4 ,:eat/one's pap] on ! subject1 :i* _h be5 previ\sly read at ! ,royal ,society on ! #ba/ ( ,june1 0 pr9t$ 9 _! ,transactions = #ahch4ba #ba ,phil4 ,trans41 #ahch1 pp4 #cga-cid4 ,mr4 ,elliot 0 l$ to ! /udy ( b9ocul> vision 9 consequ5ce ( hav+ writt5 an ,essay1 s e>ly z #ahbc1 = ! ,class ( ,logic 9 ! ,univ]sity ( ,ed9burgh1 8,on ! means by :i* we obta9 our k ( di/ances by ! ,eye40 ,ev] s9ce t date he 0 famili> ) ! idea1 t ! relief ( solid bodies se5 by ! eye 0 produc$ by ! union ( ! dissimil> pictures ( !m 9 ea* eye1 b he nev] imag9$ t ?is idea 0 8 own1 believ+ t x 0 kn[n to e /ud5t ( vision4 ,previ\s to or dur+ ! ye> #ahcd1 he _h resolv$ to con/ruct an in/rum5t = unit+ two dissimil> pictures1 or ( con/ruct+ a /]eoscope2 b he delay$ do+ ?is till ! ye> #ahci1 :5 he 0 reque/$ to prep>e an orig9al communication = ! ,polyte*nic ,society1 :i* _h be5 rec5tly e/abli%$ 9 ,liv]pool4 ,he 0 ?us induc$ to con/ruct ! in/rum5t :i* he _h project$1 & he exhibit$ x to 8 fri5ds1 ,mr4 ,ri*>d ,adie1 optician1 & ,mr4 ,george ,hamilton1 lectur] on *emi/ry 9 ,liv]pool1 :o be> te/imony to its exi/5ce at t date4 ,?is simple /]eoscope1 )\t l5ses or mirrors1 consi/$ ( a wood5 box #ah in*es long1 #g broad1 & #d deep1 & at ! bottom ( x1 or r its f>!r end1 0 plac$ a slide conta9+ two dissimil> pictures ( a l&scape z se5 by ea* eye4 ,photography did n !n exi/1 to enable ,mr4 ,elliot to procure two views ( ! same sc5e1 z se5 by ea* eye1 b he drew ! transp>5cy ( a l&scape ) ?ree di/ances4 ,! fir/ & mo/ remote 0 ! moon & ! sky1 & a /ream ( wat] f :i* ! moon 0 reflect$1 ! two moons be+ plac$ ne>ly at ! di/ance ( ! two eyes1 or #b in*es1 & ! two reflect$ moons at ! same di/ance4 ,! second di/ance 0 m>k$ by an old cross ab\t a hundr$ feet (f2 & ! ?ird di/ance by ! )]$ bran* ( a tree1 ?irty feet f ! obs]v]4 ,9 ! "r-h& picture1 "o arm ( ! cross j t\*$ ! disc ( ! moon1 :ile1 9 ! left-h& "o1 x project$ ov] "o-?ird ( ! disc4 ,! bran* ( ! tree t\*$ ! outl9e ( a di/ant hill 9 ! "o picture1 b 0 8a full moon's-bread?0 f x on ! o!r4 ,:5 ^! dissimil> pictures 7 unit$ by ! eyes1 a l&scape1 c]ta9ly a v imp]fect "o1 0 se5 9 relief1 compos$ ( ?ree di/ances4 ,ow+1 no d\bt1 to ! difficulty ( procur+ good b9ocul> pictures1 ,mr4 ,elliot did n see t 8 contrivance w\ld be v popul>1 & !re=e c>ri$ x no f>!r4 ,he _h nev] he>d ( ,mr4 ,:eat/one's /]eoscope till he saw 8 pap] on ,vision repr9t$ 9 ! ,philosophical ,magaz9e = ,m>* #aheb1 & hav+ p]us$ x1 he 0 conv9c$ n only t ,mr4 ,:eat/one's !ory ( ! in/rum5t 0 incorrect1 b t 8 claim to ! discov]y ( ! dissimil>ity ( ! images 9 ea* eye _h no f\ndation4 ,he 01 !re=e1 l$ to communicate to ! same j\rnal ! fact ( 8 hav+ himself1 ?irte5 ye>s be=e1 con/ruct$ & us$ a /]eoscope1 :i* 0 /ill 9 8 possession4 ,9 mak+ ?is claim1 ,mr4 ,elliot _h no int5tion ( depriv+ ,mr4 ,:eat/one ( ! cr$it :i* 0 ju/ly due to him2 & z ! claim has be5 publicly made1 we h describ$ ! nature ( x z a "p ( sci5tific hi/ory4 ,9 ,mr4 ,:eat/one's +5i\s pap] ( #ahch1 ! subject ( b9ocul> vision is treat$ at consid]able l5g?4 ,he gives an acc\nt ( ! op9ions ( previ\s writ]s1 ref]r+ repeat$ly to ! works ( ,aguilonius1 ,gass5di1 & ,bapti/a ,porta1 9 ! la/ ( :i* ! views ( ,gal5 are giv5 & expla9$4 ,9 cit+ ! passage :i* we h already quot$ f ,leon>do da ,v9ci1 & ins]t+ ! figure :i* illu/rates x1 he ma9ta9s t ,leon>do da ,v9ci 0 n aw>e 8t ! object 7,c 9 ,fig4 #b7 pres5t$ a diff]5t appe>ance to ea* eye40 8,he fail$10 he adds1 8to obs]ve ?is1 & no subsequ5t writ]1 to my k1 has suppli$ ! omission4 ,! projection ( two obvi\sly dissimil> pictures on ! two ret91 :5 a s+le object is view$1 :ile ! optic axes conv]ge1 mu/ !re=e be reg>d$ z a new fact 9 ! !ory ( vision40 ,n[1 al?\gh ,leon>do da ,v9ci does n /ate 9 s _m words t he 0 aw>e ( ! dissimil>ity ( ! two pictures1 ! fact is obvi\s 9 8 own figure1 & he 0 n l$ by 8 subject to /ate ! fact at all4 ,b ev5 if ! fact _h n />$ him 9 ! face he mu/ h kn[n x f ! ,optics ( ,euclid & ! writ+s ( ,gal51 ) :i* he c\ld n fail to h be5 well acqua9t$4 ,t ! dissimil>ity ( ! two pictures is n a new fact we h already plac$ beyond a d\bt4 ,! fact is express$ 9 words1 & del9eat$ 9 draw+s1 by ,aguilonius & ,bapti/a ,porta4 ,x 0 obvi\sly kn[n to ,dr4 ,smi?1 ,mr4 ,h>ris1 ,dr4 ,port]field1 & ,mr4 ,elliot1 be=e x 0 kn[n to ,mr4 ,:eat/one1 & we _c und]/& h[ he fail$ to obs]ve x 9 works :i* he has s (t5 quot$1 & 9 :i* he pr(esses to h se>*$ = x4 ,?is rem>kable prop]ty ( b9ocul> vision be+ ?us cle>ly e/abli%$ by prec$+ writ]s1 & admitt$ by himself1 z ! cause ( ! vision ( solidity or di/ance1 ,mr4 ,:eat/one1 z ,mr4 ,elliot _h done be=e him1 ?\ght ( an in/rum5t = unit+ ! two dissimil> pictures optically1 s z to produce ! same result t is obta9$ by ! conv]g5ce ( ! optical axes4 ,mr4 ,elliot ?\ght ( do+ ?is by ! eyes alone2 b ,mr4 ,:eat/one adopt$ a mu* bett] me?od ( do+ x by reflexion4 ,he 0 ?us l$ to con/ruct an app>atus1 to be aft]w>ds describ$1 consi/+ ( two plane mirrors1 plac$ at an angle ( #ij1 to :i* he gave ! "n ( /]eoscope1 anticipat+ ,mr4 ,elliot bo? 9 ! con/ruction & publication ( 8 inv5tion1 b n 9 ! g5]al conception ( a /]eoscope4 ,aft] describ+ 8 app>atus1 ,mr4 ,:eat/one proce$s to consid] 79 a section entitl$1 8,b9ocul> vision ( objects ( diff]5t magnitudes07 8:at effects w result f pres5t+ simil> images1 diff]+ only 9 magnitude1 to analog\s p>ts ( ! ret9a40 8,= ?is purpose10 he says1 8two squ>es or circles1 diff]+ obvi\sly b n extravagantly 9 size1 may be drawn on two sep>ate pieces ( pap]1 & plac$ 9 ! /]eoscope1 s t ! reflect$ image ( ea* %all be equally di/ant f ! eye by :i* x is reg>d$4 ,x w !n be se5 t not)/&+ ?is diff]5ce !y coalesce & occasion a s+le resultant p]ception40 ,! fact ( coalesc5ce be+ suppos$ to be p]fect1 ! au?or next seeks to det]m9e ! diff]5ce betwe5 ! l5g? ( two l9es :i* ! eye c =ce into coalesc5ce1 or 8! limits )9 :i* ! s+le appe>ance subsi/s40 ,he1 !re=e1 unites two images ( equal magnitude1 by mak+ "o ( !m visually less f di/ance1 & he /ates t1 8by ?is exp]im5t1 ! s+le appe>ance ( two images ( diff]5t size is demon/rat$40 ,n satisfi$ ) ^! errone\s ass]tions1 he proce$s to give a sort ( rule or law = asc]ta9+ ! relative size ( ! two unequal pictures :i* ! eyes c =ce into co9cid5ce4 ,! inequality1 he concludes1 mu/ n exce$ ! diff]5ce 8betwe5 ! projections ( ! same object :5 se5 9 ! mo/ oblique position ( ! eyes 7i4e41 bo? turn$ to ! extreme "r or ! extreme left7 ord9>ily employ$40 ,n[1 ?is rule1 tak5 9 ! s5se 9 :i* x is meant1 is simply a truism4 ,x m]ely /ates t ! diff]5ce ( ! pictures :i* ! eyes c make to coalesce is equal to ! diff]5ce ( ! pictures :i* ! eyes d make to coalesce 9 _! mo/ oblique position2 b ?\gh a truism x is n a tru?1 fir/1 because no real co9cid5ce ev] c take place1 &1 secondly1 because no app>5t co9cid5ce is effect$ :5 ! diff]5ce ( ! picture is great] ?an :at is above /at$4 ,f ^! pr9ciples1 :i* w aft]w>ds be %ewn to be errone\s1 ,mr4 ,:eat/one proce$s 8to exam9e :y two dissimil> pictures project$ on ! two ret9 give rise to ! p]ception ( an object 9 relief40 8,i w n attempt10 he says1 8at pres5t to give ! complete solution ( ?is "q1 :i* is f> f be+ s easy z at fir/ glance x may appe> to be1 & is1 inde$1 "o ( great complexity4 ,i %all1 9 ?is case1 m]ely consid] ! mo/ obvi\s explanations :i* might be (f]$1 & %ew _! insuffici5cy to expla9 ! :ole ( ! ph5om5a4 8,x may be suppos$ t we see only "o po9t ( a field ( view di/9ctly at ! same in/ant1 ! "o1 namely1 to :i* ! optic axes are direct$1 :ile all o!r po9ts are se5 s indi/9ctly t ! m9d does n recognise !m to be ei!r s+le or d\ble1 & t ! figure is appreciat$ by successively direct+ ! po9t ( conv]g5ce ( ! optic axes successively to a suffici5t numb] ( its po9ts to enable u to judge accurately ( its =m4 8,t !re is a degree ( indi/9ctness 9 ^? p>ts ( ! field ( view to :i* ! eyes are n imm$iately direct$1 & :i* increases ) ! di/ance f t po9t1 _c be d\bt$2 & x is also true t ! objects !re obscurely se5 are frequ5tly d\bl$4 ,9 ord9>y vision1 x may be said1 ?is indi/9ctness & duplicity are n att5d$ to1 because ! eyes %ift+ cont9ually f po9t to po9t1 e "p ( ! object is successively r5d]$ di/9ct1 & ! p]ception ( ! object is n ! consequ5ce ( a s+le glance1 dur+ :i* a small "p ( x only is se5 di/9ctly1 b is =m$ f a comp>ison ( all ! pictures successively se51 :ile ! eyes 7 *ang+ f "o po9t ( an object to ano!r4 8,all ?is is ,,9 ,,"s ,,degree true1 b 7 x entirely s no appe>ance ( relief %\ld pres5t itself :5 ! eyes rema9 int5tly fix$ on "o po9t ( a b9ocul> image 9 ! /]eoscope4 ,b 9 p]=m+ ! exp]im5t c>efully1 x w be f\nd1 provid$ ! picture d n ext5d f> beyond ! c5tres ( di/9ct vision1 t ! image is /ill se5 s+le1 & 9 relief1 :5 9 ?is condition40#bb #bb ,phil4 ,trans41 #ahch1 pp4 #cia1 #cib4 ,9 ?is passage ! au?or makes a di/9ction betwe5 ord9>y b9ocul> vision1 & b9ocul> vision ?r\gh ! /]eoscope1 :]eas 9 reality !re is none4 ,! !ory ( bo? is exactly ! same4 ,! muscles ( ! two eyes unite ! two dissimil> pictures1 & exhibit ! solid1 9 ord9>y vision2 :]eas 9 /]eoscopic vision ! images are unit$ by reflexion or refraction1 ! eyes 9 bo? cases obta9+ ! vision ( diff]5t di/ances by rapid & successive conv]g5ces ( ! optical axes4 ,mr4 ,:eat/one notices ! degree ( indi/9ctness 9 ! p>ts ( ! picture to :i* ! eyes are n imm$iately direct$2 b he does n notice ! 8confusion & incongruity0 :i* ,aguilonius says ought to exi/1 9 consequ5ce ( "s p>ts ( ! result+ relievo be+ se5 ( "o size by ! left eye alone1--o!r p>ts ( a diff]5t size by ! "r eye alone1 & o!r p>ts by bo? eyes4 ,?is confusion1 h[ev]1 ,aguilonius1 z we h se51 f\nd n to exi/1 & he ascribes x to ! influ5ce ( a common s5se ov]rul+ ! op]ation ( physical laws4 ,errone\s z ?is explanation is1 x is /ill bett] ?an t ( ,mr4 ,:eat/one1 :i* we %all n[ proce$ to expla94 ,9 ord] to disprove ! !ory ref]r$ to 9 ! prec$+ extract1 ,mr4 ,:eat/one describes two exp]im5ts1 :i* he says are equally decisive aga9/ x1 ! fir/ ( !m only be+ subject to rigor\s exam9ation4 ,) ?is view he draws 8two l9es ab\t two in*es long1 & incl9$ t[>ds ea* o!r1 on a %eet ( pap]1 & hav+ caus$ !m to co9cide by conv]g+ ! optic axes to a po9t ne>] ?an ! pap]1 he looks int5tly on ! upp] end ( ! resultant l9e )\t all[+ ! eyes to w&] f x = a mom5t4 ,! entire l9e w appe> s+le1 & 9 its prop] relief1 c4444 ,! eyes10 he cont9ues1 8sometimes become fatigu$1 :i* causes ! l9e to become d\ble at ^? p>ts to :i* ! optic axes are n fix$1 b 9 su* case all appe>ance ( relief vani%es4 ,! same exp]im5t may be tri$ ) small complex figures1 b ! pictures %\ld n ext5d too f> beyond ! c5tre ( ! ret940 ,n[ ^! exp]im5ts1 if rightly made & int]pret$1 are n decisive aga9/ ! !ory4 ,x is n true t ! entire l9e appe>s s+le :5 ! axes are conv]g$ ^u ! upp] end ( ! resultant l9e1 & x is n true t ! disappe>ance ( ! relief :5 x does disappe> arises f ! eye be+ fatigu$4 ,9 ! comb9ation ( m complex figures1 su* z two simil> rectil9eal figures conta9$ by l9es ( unequal l5g?1 nei!r ! inequalities nor ! entire figure w appe> s+le :5 ! axes are conv]g$ ^u any "o po9t ( x4 ,9 ! diff]5t passages :i* we h quot$ f ,mr4 ,:eat/one's pap]1 & 9 ! o!r p>ts ( x :i* relate to b9ocul> vision1 he is obvi\sly halt+ betwe5 tru? & error1 betwe5 !ories :i* he p>tly believes1 & ill-obs]v$ facts :i* he _c reconcile ) !m4 ,accord+ to him1 c]ta9 tru?s 8may be suppos$0 to be true1 & o!r tru?s may be 89 "s degree true10 b 8n entirely s20 & ?us1 z he confesses1 ! problem ( b9ocul> & /]eoscopic vision 8is inde$ "o ( great complexity10 ( :i* 8he w n attempt at pres5t to give ! complete solution40 ,if he _h plac$ a prop] reliance on ! law ( visible direction :i* he ackn[l$ges ,i h e/abli%$1 & 8) :i*10 he says1 8! laws ( visible direction = b9ocul> vision ought to conta9 no?+ inconsi/5t10 he w\ld h se5 ! impossibility ( ! two eyes unit+ two l9es ( inequal l5g?2 & _h he believ$ 9 ! law ( di/9ct vision he w\ld h se5 ! impossibility ( ! two eyes obta9+ s+le vision ( any m ?an "o po9t ( an object at a "t4 ,^! laws ( vision are z rigor\sly true z any o!r physical laws1--z completely demon/rat$ z ! law ( gravity 9 ,a/ronomy1 or ! law ( ! ,s9es 9 ,optics2 & ! mom5t we all[ !m to be tamp]$ ) to obta9 an explanation ( physical puzzles1 we conv]t sci5ce into leg]dema91 & philosoph]s into conjurors4 ,su* 0 ! /ate ( our /]eoscopic k 9 #ahch1 aft] ! publication ( ,mr4 ,:eat/one's int]e/+ & important pap]4 ,previ\s to ?is ,i communicat$ to ! ,briti% ,association at ,newca/le1 9 ,augu/ #ahch1 a pap]1 9 :i* ,i e/abli%$ ! law ( visible direction already m5tion$1 :i*1 ?\gh x _h be5 ma9ta9$ by prec$+ writ]s1 _h be5 prov$ by ! illu/ri\s ,d',alemb]t to be incompatible ) obs]vation1 & ! admitt$ anatomy ( ! human eye4 ,at ! same meet+ ,mr4 ,:eat/one exhibit$ 8 /]eoscopic app>atus1 :i* gave rise to an animat$ discussion on ! !ory ( ! in/rum5t4 ,dr4 ,:ewell ma9ta9$ t ! ret9a1 9 unit+1 or caus+ to coalesce into a s+le resultant impression two l9es ( diff]5t l5g?s1 _h ! p[] ei!r ( contract+ ! longe/1 or l5g!n+ ! %orte/1 or :at might h be5 sugge/$ 9 ord] to give ! ret9a only half ! tr\ble1 t x contract$ ! long l9e z mu* z x exp&$ ! %ort "o1 & ?us caus$ !m to comb9e ) a less ex]tion ( muscul> p[]6 ,9 opposition to ^! views1 ,i ma9ta9$ t ! ret9a1 a s(t pulpy membrane :i* ! smalle/ =ce te>s 9 pieces1 _h no su* p[]1--t a hypo!sis s gratuit\s 0 n requir$1 & t ! law ( visible direction af=d$ ! mo/ p]fect explanation ( all ! /]eoscopic ph5om5a4 ,9 consequ5ce ( ?is discussion1 ,i 0 l$ to repeat my exp]im5ts1 & to inquire :e!r or n ! eyes 9 /]eoscopic vision did actually unite ! two l9es ( diff]5t l5g?s1 or ( diff]5t app>5t magnitudes4 ,i f\nd t !y did n1 & t no su* union 0 requir$ to conv]t by ! /]eoscope two plane pictures into ! app>5t :ole f :i* !y 7 tak5 z se5 by ea* eye4 ,^! views 7 made public 9 ! lectures on ! ,philosophy ( ! ,s5ses1 :i* ,i occasionally deliv]$ 9 ! ,college ( ,/4 ,salvator & ,/4 ,leon>d1 ,/4 ,&rews1 & ! diff]5t /]eoscopes :i* ,i _h inv5t$ 7 also exhibit$ & expla9$4 ,9 exam9+ ,dr4 ,b]keley's celebrat$ ,!ory ( ,vision1 ,i saw ! va/ importance ( e/abli%+ ! law ( visible direction1 & ( prov+ by ! aid ( b9ocul> ph5om5a1 & 9 opposition to ! op9ion ( ! mo/ di/+ui%$ metaphysicians1 t we actually see a ?ird dim5sion 9 space1 ,i !re=e submitt$ to ! ,royal ,society ( ,ed9burgh1 9 ,janu>y #ahdc1 a pap] ,on ! law ( visible position 9 s+le & b9ocul> vision1 & on ! repres5tation ( solid figures by ! union ( dissimil> plane pictures on ! ret9a4 ,m ?an twelve ye>s h n[ elaps$ s9ce ?is pap] 0 read1 & nei!r ,mr4 ,:eat/one nor ,dr4 ,:ewell h made any attempt to def5d ! views :i* x refutes4 ,9 cont9u+ my rese>*es1 ,i communicat$ to ! ,royal ,society ( ,ed9burgh1 9 ,april #ahdd1 a pap] ,on ! k ( di/ance z giv5 by b9ocul> vision1 9 :i* ,i describ$ sev]al int]e/+ ph5om5a produc$ by ! union ( simil> pictures1 su* z ^? :i* =m ! patt]ns ( c>pets & pap]-hang+s4 ,9 c>ry+ on ^! inquiries ,i f\nd ! reflect+ /]eoscope ( little s]vice1 & ill fitt$1 n only = popul> use1 b = ! application ( ! in/rum5t to v>i\s useful purposes4 ,i 0 ?us l$ to ! con/ruction ( sev]al new /]eoscopes1 b p>ticul>ly to ! ,l5ticul> ,/]eoscope1 n[ 9 univ]sal use4 ,!y 7 con/ruct$ 9 ,/4 ,&rews & ,dundee1 ( v>i\s mat]ials1 su* z wood1 t9-plate1 brass1 & ( all sizes1 f t n[ g5]ally adopt$1 to a microscopic v>iety :i* c\ld be c>ri$ 9 ! pocket4 ,new geometrical draw+s 7 execut$ = !m1 & b9ocul> pictures tak5 by ! sun 7 li?ograph$ by ,mr4 ,s*5ck ( ,ed9burgh4 ,/]eoscopes ( ! l5ticul> =m 7 made by ,mr4 ,l\don1 optician1 9 ,dundee1 & s5t to sev]al ( ! nobility 9 ,london1 & 9 o!r places1 & an acc\nt ( ^! /]eoscopes1 & ( a b9ocul> cam]a = tak+ portraits1 & copy+ /atues1 0 communicat$ to ! ,royal ,scotti% ,society ( ,arts1 & publi%$ 9 _! ,transactions4 ,x _h nev] be5 propos$ to apply ! reflect+ /]eoscope to portraiture or sculpture1 or1 inde$1 to any useful purpose2 b x 0 v obvi\s1 aft] ! discov]y ( ! ,dagu]reotype & ,talbotype1 t b9ocul> draw+s c\ld be tak5 ) su* accuracy z to exhibit 9 ! /]eoscope excell5t repres5tations 9 relief1 bo? ( liv+ p]sons1 build+s1 l&scape sc5]y1 & e v>iety ( sculpture4 ,9 ord] to %ew its application to ! mo/ int]e/+ ( ^! purposes1 ,dr4 ,adamson ( ,/4 ,&rews1 at my reque/1 execut$ two b9ocul> portraits ( himself1 :i* 7 g5]ally circulat$ & greatly admir$4 ,?is successful application ( ! pr9ciple to portraiture 0 communicat$ to ! public1 & recomm5d$ z an art ( great dome/ic int]e/4 ,aft] endeav\r+ 9 va9 to induce opticians1 bo? 9 ,london & ,birm+ham1 7:]e ! in/rum5t 0 exhibit$ 9 #ahdi to ! ,briti% ,association17 to con/ruct ! l5ticul> /]eoscope1 & photograph]s to execute b9ocul> pictures = x1 ,i took ) me to ,p>is1 9 #ahej1 a v f9e in/rum5t1 made by ,mr4 ,l\don 9 ,dundee1 ) ! b9ocul> draw+s & portraits already m5tion$4 ,i %ew$ ! in/rum5t to ! ,abb ,moigno1 ! di/+ui%$ au?or ( ,l',optique ,mod]ne1 to ,m4 ,soleil & 8 son-9-law1 ,m4 ,duboscq1 ! em95t ,p>isian opticians1 & to "s memb]s ( ! ,in/itute ( ,france4 ,^! g5tlem5 saw at once ! value ( ! in/rum5t1 n m]ely z "o ( amusem5t1 b z an important auxili>y 9 ! arts ( portraiture & sculpture4 ,m4 ,duboscq imm$iately began to make ! l5ticul> /]eoscope = sale1 & execut$ a s]ies ( ! mo/ beautiful b9ocul> ,dagu]reotypes ( liv+ individuals1 /atues1 b\quets ( fl[]s1 & objects ( natural hi/ory1 :i* ?\s&s ( individuals flock$ to exam9e & admire4 ,9 an int]e/+ article 9 ,la ,presse1#bc ! ,abb ,moigno gave ! foll[+ acc\nt ( ! introduction ( ! in/rum5t into ,p>is3-- #bc ,decemb] #bh1 #aeej4 8,9 8 la/ visit to ,p>is1 ,sir ,david ,brew/] intru/$ ! models ( 8 /]eoscope to ,m4 ,jules ,duboscq1 son-9-law & successor ( ,m4 ,soleil1 & ^: intellig5ce1 activity1 & affability w ext5d ! reputation ( ! di/+ui%$ arti/s ( ! ,rue de l',odeon1 #ce4 ,m4 ,jules ,duboscq has set himself to "w ) indefatigable ard\r4 ,)\t requir+ to h rec\rse to ! b9ocul> cam]a1 he has1 ) ! ord9>y ,dagu]reotype app>atus1 procur$ a great numb] ( dissimil> pictures ( /atues1 bas-reliefs1 & portraits ( celebrat$ individuals1 c4 ,8 /]eoscopes are con/ruct$ ) m elegance1 & ev5 ) m p]fection1 ?an ! orig9al ,engli% 7,scot*7 in/rum5ts1 & :ile he is %ew+ _! wond]ful effects to natural philosoph]s & amateurs :o h flock$ to him 9 cr[ds1 !re is a spontane\s & unanim\s cry ( admiration40 ,:ile ! l5ticul> /]eoscope 0 ?us excit+ mu* int]e/ 9 ,p>is1 n a s+le in/rum5t _h be5 made 9 ,london1 & x 0 n till a ye> aft] its introduction into ,france t x 0 exhibit$ 9 ,engl&4 ,9 ! f9e collection ( philosophical in/rum5ts :i* ,m4 ,duboscq contribut$ to ! ,great ,exhibition ( #ahea1 & = :i* he 0 hon\r$ ) a ,c\ncil m$al1 he plac$ a l5ticul> /]eoscope1 ) a beautiful set ( b9ocul> ,dagu]reotypes4 ,?is in/rum5t attract$ ! p>ticul> att5tion ( ! ,que51 & be=e ! clos+ ( ! ,cry/al ,palace1 ,m4 ,duboscq execut$ a beautiful /]eoscope1 :i* ,i pres5t$ to ,h] ,maje/y 9 8 "n4 ,9 consequ5ce ( ?is public exhibition ( ! in/rum5t1 ,m4 ,duboscq receiv$ sev]al ord]s f ,engl&1 & a l>ge numb] ( /]eoscopes 7 ?us introduc$ into ?is c\ntry4 ,! dem&1 h[ev]1 became s great1 t opticians ( all k9ds devot$ !mselves to ! manufacture ( ! in/rum5t1 & photograph]s1 bo? 9 ,dagu]reotype & ,talbotype1 f\nd x a mo/ lucrative bran* ( _! pr(ession1 to take b9ocul> portraits ( views to be ?r[n into relief by ! /]eoscope4 ,its application to sculpture1 :i* ,i _h po9t$ out1 0 fir/ made 9 ,france1 & an arti/ 9 ,p>is actually copi$ a /atue f ! relievo produc$ by ! /]eoscope4 ,?ree ye>s aft] ,i _h publi%$ a description ( ! l5ticul> /]eoscope1 & aft] x _h be5 9 g5]al use 9 ,france & ,engl&1 & ! reflect+ /]eoscope =gott51#bd ,mr4 ,:eat/one pr9t$1 9 ! ,philosophical ,transactions = #aheb1 a pap] on ,vision1 9 :i* he says t he _h previ\sly us$ 8an app>atus 9 :i* prisms 7 employ$ to deflect ! rays ( light proce$+ f ! pictures1 s z to make !m appe> to occupy ! same place20 & he adds1 8,i h call$ x ! refract+ /]eoscope40#be ,n[1 :atev] ,mr4 ,:eat/one may h done ) prisms1 & at :atev] "t he may h done x1 ,i 0 ! fir/ p]son :o publi%$ a description ( /]eoscopes bo? ) refract+ & reflect+ prisms2 & dur+ ! ?ree ye>s t elaps$ aft] he _h read my pap]1 he made no claim to ! sugge/ion ( prisms till aft] ! great success ( ! l5ticul> /]eoscope4 ,! reason :y he !n made ! claim1 & ! only reason :y we d n make him a pres5t ( ! sugge/ion1 w appe> f ! foll[+ hi/ory3-- #bd 8,le fait e/10 says ! ,abb ,moigno1 8que le /roscope p> rflexion tait presque compltem5t oubli1 lorsque ,sir ,david ,brew/] con/ruisit son /roscope p> refraction que n\s allons dcrire40--,cosmos1 vol4 i4 p4 #d1 #aheb4 #be ,phil4 ,trans41 #aheb1 p4 #f4 ,9 ! pap] above ref]r$ to1 ,mr4 ,:eat/one says1--8,i recomm5d1 z a conv5i5t arrangem5t ( ! refract+ /]eoscope = view+ ,dagu]reotypes ( small dim5sions1 ! in/rum5t repres5t$1 7,fig4 #d17 %ort5$ 9 its l5g? f #h in*es to #e1 & l5ses #e in*es focal di/ance1 plac$ be=e & close to ! prisms40#bf ,al?\gh ?is refract+ app>atus1 :i* is simply a det]ioration ( ! l5ticul> /]eoscope1 is recomm5d$ by ,mr4 ,:eat/one1 nobody ei!r makes x or uses x4 ,! semi-l5ses or qu>t]-l5ses ( ! l5ticul> /]eoscope include a virtual & absolutely p]fect prism1 &1 :at is ( f> m consequ5ce1 ea* l5s is a v>iable l5ticul> prism1 s t1 :5 ! eye-tubes are plac$ at diff]5t di/ances1 ! l5ses h diff]5t p[]s ( displac+ ! pictures4 ,!y c ?us unite pictures plac$ at diff]5t di/ances1 :i* _c be done by any comb9ation ( :ole l5ses & prisms4 #bf ,ibid41 pp4 #i1 #aj4 ,9 ! autumn ( #ahed1 aft] all ! facts ab\t ! /]eoscope 7 be=e ! public1 & ,mr4 ,:eat/one 9 full possession ( all ! m]it ( hav+ anticipat$ ,mr4 ,elliot 9 ! publication ( 8 /]eoscopic app>atus1 & ( 8 explanation ( ! !ory ( /]eoscopic relief1 su* z x 01 he ?\ght x prop] to revive ! controv]sy by transmitt+ to ! ,abb ,moigno1 = publication 9 ,cosmos1 an extract ( a lett] ( m9e dat$ #bg? ,septemb] #ahch4 ,?is extract 0 publi%$ 9 ! ,cosmos ( ! #ae? ,augu/ #ahed1bg ) ! foll[+ illogical comm5t>y by ! editor4 8,n\s avons eu tort mille fois d'accord] notre illu/re ami1 ,sir ,david ,brew/]1 l'inv5tion du /roscope p> rfraction4 ,m4 ,:eat/one1 en effet1 a mis entre nos ma9s une lettre date1 le croirait on1 du #bg ,septembre #ahch1 dans lequel n\s avons l ces mots crits p> l'illu/re savant ,ecossais3 #8,i h also /at$ t y promis$ to ord] = me y\r /]eoscope1 bo? ) reflectors & ,,prisms4 ,j'ai aussi dit 7 ,"l ,rosse#bh7 que v\s aviez promis de comm&] p\r moi votre /roscope1 celui avec rflecteurs et celui avec prismes4' ,le /roscope p> rfraction e/ donc1 aussi bi5 que le /roscope p> rflexion1 le /roscope de ,m4 ,:eat/one1 qui l'avait inv5t en #ahch1 et le faisait con/ruire cette poque p\r ,sir ,david ,brew/] lui-mme4 ,ce que ,sir ,david ,brew/] a imag9e1 et c'e/ une ide trs +nieuse1 dont ,m4 ,:eat/one ne lui disputt jamais la gloire1 c'e/ de =m] les deux prismes du /roscope p> rfraction avec les deux moitis d'une mme l5tille40 #bg ,vol4 v4 livre viii4 p4 #bda4 #bh ,mr4 ,&rew ,ross1 ! celebrat$ optician6 ,t ! read] may =m a correct idea ( ! conduct ( ,mr4 ,:eat/one 9 mak+ ?is claim indirectly1 & 9 a =eign j\rnal1 ^: editor he has will+ly misl$1 ,i mu/ rem9d him t ,i fir/ saw ! reflect+ /]eoscope at ! meet+ ( ! ,briti% ,association at ,newca/le1 9 ! middle ( ,augu/ #ahch4 ,x is prov$ by my lett] t he & ,i !n conv]s$ on ! subject ( prisms1 :i* at t "t he _h nev] ?\ght (4 ,i sugge/$ prisms = displac+ ! pictures1 & ,mr4 ,:eat/one's natural reply 01 t !y mu/ be a*romatic prisms4 ,?is fact1 if d5i$1 may be prov$ by v>i\s circum/ances4 ,8 pap] ( #ahch conta9s no ref]5ce to prisms4 ,if he _h sugge/$ ! use ( prisms 9 ,augu/ #ahch1 he w\ld h ins]t$ 8 sugge/ion 9 t pap]1 :i* 0 !n unpubli%$2 & if he _h only once tri$ a prism /]eoscope1 he nev] w\ld h us$ ano!r4 ,on my return to ,scotl&1 ,i ord]$ f ,mr4 ,&rew ,ross "o ( ! reflect+ /]eoscopes1 & "o made ) a*romatic prisms2 b my words d n imply t ,mr4 ,:eat/one 0 ! fir/ p]son :o sugge/$ prisms1 & /ill less t he ev] made or us$ a /]eoscope ) prisms4 ,b h[ev] ?is may be1 x is a mo/ extraord9>y /atem5t1 :i* he all[s ! ,abb ,moigno to make1 & :i*1 ?\gh made a ye> & a half ago1 he has n enabl$ ! ,abb to correct1 t a /]eoscope ) prisms 0 made = me 7or = any o!r p]son7 by ,mr4 ,ross4 ,i nev] saw su* an in/rum5t1 or he>d ( its be+ con/ruct$3 ,i suppos$ t aft] our conv]sation ,mr4 ,:eat/one might h tri$ a*romatic prisms1 & 9 #ahdh1 :5 ,i describ$ my s+le prism /]eoscope1 ,i /at$ :at ,i n[ f9d is n correct1 t ,i believ$ ,mr4 ,:eat/one _h us$ two a*romatic prisms4 ,! foll[+ lett] f ,mr4 ,&rew ,ross w prove ! ma9 fact t he nev] con/ruct$ = me1 or = ,mr4 ,:eat/one1 any refract+ /]eoscope3-- 0#b1 ,,fea!r/one ,,build+s1 #bh? ,septemb] #ahed4 8,,de> ,,sir1--,9 reply to y\rs ( ! #aa? in/ant1 ,i beg to /ate t ,i nev] suppli$ y ) a /]eoscope 9 :i* prisms 7 employ$ 9 place ( plane mirrors4 ,i h a p]fect recollection ( be+ call$ ^u ei!r by y\rself or ,pr(essor ,:eat/one1 "s f\rte5 ye>s s9ce1 to make a*romatiz$ prisms = ! above in/rum5t4 ,i also recollect t ,i did n proce$ to manufacture !m 9 consequ5ce ( ! great bulk ( an a*romatiz$ prism1 ) ref]5ce to _! p[] ( deviat+ a ray ( light1 & at t p]iod glass suffici5tly free f /ri c\ld n readily be obta9$1 & 0 consequ5tly v high-pric$4--,i rema91 c4 c4 8,,&rew ,,ross4 8,to ,sir ,david ,brew/]40 ,^u ! receipt ( ?is lett] ,i transmitt$ a copy ( x to ! ,abb ,moigno1 to %ew him h[ he _h be5 misl$ into ! /atem5t1 8t ,mr4 ,:eat/one _h caus$ a /]eoscope ) prisms to be con/ruct$ = me20 b nei!r he nor ,mr4 ,:eat/one h felt x _! duty to )draw t errone\s /atem5t4 ,9 ref]5ce to ! comm5ts ( ! ,abb ,moigno1 x is necess>y to /ate1 t :5 he wrote !m he _h 9 8 possession my pr9t$ description ( ! s+le-prism1 & o!r /]eoscopes1#bi 9 :i* ,i m5tion my belief1 n[ prov$ to be errone\s1 t ,mr4 ,:eat/one _h us$ a*romatic prisms1 s t he _h1 on my express au?ority1 ! in=mation :i* surpris$ him 9 my lett]4 ,! ,abb also mu/ be> ! responsibility ( a gl>+ mis9t]pretation ( my lett] ( #ahch4 ,9 t lett] ,i say t ,mr4 ,:eat/one promis$ to ord] c]ta9 ?+s f ,mr4 ,ross1 & ! ,abb decl>es1 contr>y to ! express t]ms ( ! lett]1 z well z to fact1 t ^! ?+s 7 actually con/ruct$ = me4 ,! lett]1 on ! contr>y1 does n ev5 /ate t ,mr4 ,:eat/one compli$ ) my reque/1 & x does n ev5 appe> f x t ! reflect+ /]eoscope 0 made = me by ,mr4 ,ross4 #bi ,! ,abb gave an ab/ract ( ?is pap] 9 ! ,fr5* j\rnal ,la ,presse1 ,decemb] #bh1 #ahej4 ,su* is a brief hi/ory ( ! l5ticul> /]eoscope1 ( its introduction into ,p>is & ,london1 & ( its application to portraiture & sculpture4 ,x is n[ 9 g5]al use ov] ! :ole _w1 & x has be5 e/imat$ t upw>ds ( half a million ( ^! in/rum5ts h be5 sold4 ,a ,/]eoscope ,company has be5 e/abli%$ 9 ,london#cj = ! manufacture & sale ( ! l5ticul> /]eoscope1 & = ! production ( b9ocul> pictures = educational & o!r purposes4 ,photograph]s are n[ employ$ 9 e "p ( ! globe 9 tak+ b9ocul> pictures = ! in/rum5t1--among ! ru9s ( ,pompeii & ,h]culaneum--on ! glaci]s & 9 ! valleys ( ,switz]l&--among ! public monum5ts 9 ! ,old & ! ,new ,_w--amid ! %ipp+ ( our comm]cial h>b\rs--9 ! museums ( anci5t & mod]n life--9 ! sacr$ prec9cts ( ! dome/ic circle--& among ^? sc5es ( ! picturesque & ! sublime :i* are s affectionately associat$ ) ! recollection ( our e>ly days1 & amid :i*1 ev5 at ! close ( life1 we r5ew1 ) l(ti] s5tim5ts & nobl] aspirations1 ! y\? ( our be+1 :i*1 9 ! worlds ( ! future1 is to be ! comm5cem5t ( a long] & a happi] exi/5ce4 #cj ,no4 #ed1 ,*eapside1 & #cac1 ,ox=d ,/reet4 ,! prize ( tw5ty gu9eas :i* !y (f]$ = ! be/ %ort popul> treatise on ! ,/]eoscope1 has be5 adjudg$ to ,mr4 ,lonie1 ,tea*] ( ,ma!matics 9 ! ,madras ,in/itution1 ,/4 ,&rews4 ,! second prize 0 giv5 to ! ,rev4 ,r4 ,graham1 ,ab]nyte1 ,p]?%ire4 ,,*apt] ,,ii4 ,,on ,,monocul> ,,vision1 ,,or ,,vision ,,) ,,"o ,,eye4 ,9 ord] to und]/& ! !ory & con/ruction ( ! /]eoscope we mu/ be acqua9t$ ) ! g5]al /ructure ( ! eye1 ) ! mode 9 :i* ! images ( visible objects are =m$ )9 x1 & ) ! laws ( vision by means ( :i* we see ^? objects 9 ! position :i* !y occupy1 t is1 9 ! direction & at ! di/ance at :i* !y exi/4 ,e visible object radiates1 or ?r[s out 9 all directions1 p>ticles or rays ( light1 by means ( :i* we see !m ei!r directly by ! images =m$ 9 ! eye1 or indirectly by look+ at images ( !m =m$ by _! pass+ ?r\gh a small hole1 or ?r\gh a l5s plac$ 9 a d>k room or cam]a1 at ! end ( :i* is a piece ( pap] or gr\nd-glass to receive ! image4 ,9 ord] to und]/& ?is let ,h be a v small p9-hole 9 a %utt] or cam]a1 ,,mn1 & let ,,ryb be any object ( diff]5t col\rs1 ! upp] "p1 ,r1 be+ r$1 ! middle1 ,y1 yell[1 & ! l[] "p1 ,b1 blue4 ,if a %eet ( :ite pap]1 br1 is plac$ beh9d ! hole ,h1 at ! same di/ance z ! object ,,rb is be=e x1 an image1 br1 w be =m$ ( ! same ray & ! same col\rs z ! object ,,rb4 ,z ! p>ticles or rays ( light move 9 /raight l9es1 a r$ ray f ! middle "p ( ,r w pass ?r\gh ! hole ,h & illum9ate ! po9t r ) r$ light4 ,9 l mann]1 rays f ! middle po9ts ( ,y & ,b w pass ?r\gh ,h & illum9ate ) yell[ & blue light ! po9ts y & b4 ,e o!r po9t ( ! col\r$ spaces1 ,r1 ,y1 & ,b1 w1 9 ! same mann]1 pa9t itself1 z x 71 on ! pap]1 & produce a col\r$ image1 byr1 exactly ! same 9 =m & col\r z ! object ,,ryb4 ,if ! hole ,h is suffici5tly small no ray f any "o po9t ( ! object w int]f]e ) or mix ) any o!r ray t falls ^u ! pap]4 ,if ! pap] is held at half ! di/ance1 at by = example1 a col\r$ image1 byr1 ( half ! size1 w be =m$1 & if we hold x at twice ! di/ance1 at br = example1 a col\r$ image1 byr1 ( twice ! size1 w be pa9t$ on ! pap]4 ,illu/ration3 ,,fig4 #d4 ,z ! hole ,h is suppos$ to be s small z to receive only "o ray f e po9t ( ! object1 ! images ( ! object1 viz41 br1 br1 br1 w be v fa9t4 ,by wid5+ ! hole ,h1 s z to admit m rays f ea* lum9\s po9t ( ,,rb1 ! images w\ld become bright]1 b !y w\ld become at ! same "t indi/9ct1 z ! rays f "o po9t ( ! object w\ld mix ) ^? f adjac5t po9ts1 & at ! b\nd>ies ( ! col\rs ,r1 ,y1 & ,b1 ! "o col\r w\ld oblit]ate ! o!r4 ,9 ord]1 !re=e1 to obta9 suffici5tly bright images ( visible objects we mu/ use l5ses1 :i* h ! prop]ty ( =m+ di/9ct images beh9d !m1 at a po9t call$ _! focus4 ,if we wid5 ! hole ,h1 & place 9 x a l5s ^: focus is at y1 = an object at ! same di/ance1 ,,hy1 x w =m a bright & di/9ct image1 br1 ( ! same size z ! object ,,rb4 ,if we remove ! l5s1 & place ano!r 9 ,h1 ^: focus is at y1 = a di/ance ,,hy1 an image1 br1 half ( ! size ( ,,rb1 w be =m$ at t po9t2 & if we sub/itute = ?is l5s ano!r1 ^: focus is at y1 a di/9ct image1 br1 twice ! size ( ! object1 w be =m$1 ! size ( ! image be+ always to t ( ! object z _! respective di/ances f ! hole or l5s at ,h4 ,) ! aid ( ^! results1 :i* any p]son may confirm by mak+ ! exp]im5ts1 we %all easily und]/& h[ we see ext]nal objects by means ( ! images =m$ 9 ! eye4 ,! human eye1 a section & a front view ( :i* is %ewn 9 ,fig4 #e1 ,a1 is almo/ a sph]e4 ,its out] membrane1 ,,abcde1 or ,,mno1 ,fig4 #e1 ,b1 consi/s ( a t\gh sub/ance1 & is call$ ! scl]otic coat1 :i* =ms ! :ite ( ! eye1 ,a1 se5 9 ! front view4 ,! front "p ( ! eyeball1 ,cx,d1 :i* resembles a small wat*-glass1 is p]fectly transp>5t1 & is call$ ! cornea4 ,beh9d x is ! iris1 cabe1 or ,c 9 ! front view1 :i* is a circul> disc1 ) a hole1 ab1 9 its c5tre1 call$ ! pupil1 or black ( ! eye4 ,x is1 z x 71 ! w9d[ ( ! eye1 ?r\gh :i* all ! light f visible objects mu/ pass4 ,! iris has diff]5t col\rs 9 diff]5t p]sons1 black1 blue1 or grey2 & ! pupil1 ab1 or ,h1 has ! p[] ( contract+ or enl>g+ its size accord+ z ! light :i* ent]s x is m or less bright4 ,9 sunlight x is v small1 & 9 twilight its size is consid]able4 ,beh9d ! iris1 & close to x1 is a d\bly convex l5s1 df1 or ,,ll 9 ,fig4 #e1 ,b1 call$ ! cry/all9e l5s4 ,x is m convex or r\nd on ! inn] side1 & x is susp5d$ by ! cili>y processes at ,,lc1 ,,lc1 by :i* x is suppos$ to be mov$ t[>ds & f ,h1 9 ord] to accommodate ! eye to diff]5t di/ances1 or obta9 di/9ct vision at ^! di/ances4 ,at ! back ( ! eye is a ?9 pulpy transp>5t membrane1 rr ,o rr1 or vvv1 call$ ! ret9a1 :i*1 l ! gr\nd glass ( a cam]a obscura1 receives ! images ( visible objects4 ,?is membrane is an expansion ( ! optic n]ve ,o1 or ,a 9 ,fig4 #e1 ,a1 :i* passes to ! bra91 &1 by a process ( :i* we are ignorant1 gives u vision ( ! objects ^: images are =m$ on its exp&$ surface4 ,! globul> =m ( ! eye is ma9ta9$ by two fluids :i* fill x1--! aque\s hum\r1 :i* lies betwe5 ! cry/all9e l5s & ! cornea1 & ! vitre\s hum\r1 ,,zz1 :i* fills ! back ( ! eye4 ,illu/ration3 ,,fig4 #e1 ,a4 ,illu/ration3 ,,fig4 #e1 ,b4 ,b ?\gh we are ignorant ( ! mann] 9 :i* ! m9d takes cognizance ?r\gh ! bra9 ( ! images on ! ret9a1 & may probably nev] "k x1 we c det]m9e exp]im5tally ! laws by :i* we obta91 ?r\gh _! images on ! ret9a1 a k ( ! direction1 ! position1 & ! =m ( ext]nal objects4 ,if ! eye ,,mn consi/$ only ( a holl[ ball ) a small ap]ture ,h1 an inv]t$ image1 ab1 ( any ext]nal object ,,ab w\ld be =m$ on ! ret9a r,or1 exactly z 9 ,fig4 #d4 ,a ray ( light f ,a pass+ ?r\gh ,h w\ld /rike ! ret9a at a1 & "o f ,b w\ld /rike ! ret9a at b4 ,if ! hole ,h is v small ! inv]t$ image ab w\ld be v di/9ct1 b v obscure4 ,if ! hole 7 ! size ( ! pupil ! image w\ld be suffici5tly lum9\s1 b v indi/9ct4 ,to rem$y ?is ! cry/all9e l5s is plac$ beh9d ! pupil1 & gives di/9ctness to ! image ab =m$ 9 its focus4 ,! image1 h[ev]1 /ill rema9s inv]t$1 a ray f ! upp] "p ,a ( ! object necess>ily fall+ on ! l[] "p a ( ! ret9a1 & a ray f ! l[] "p ,b ( ! object ^u ! upp] "p b ( ! ret9a4 ,n[1 x has be5 prov$ by accurate exp]im5ts t 9 :atev] direction a ray ,,aha falls ^u ! ret9a1 x gives u ! vision ( ! po9t ,a f :i* x proce$s1 or causes u to see t po9t1 9 a direction p]p5dicul> to ! ret9a at a1 ! po9t on :i* x falls4 ,x has also be5 prov$ t ! human eye is ne>ly sph]ical1 & t a l9e drawn p]p5dicul> to ! ret9a f any po9t a ( ! image ab w v ne>ly pass ?r\gh ! correspond+ po9t ,a ( ! object ,,ab1#ca s t ! po9t ,a is1 9 virtue ( ?is law1 :i* is call$ ! ,law ( visible direction1 se5 9 ne>ly its true direction4 #ca ,ed9burgh ,transactions1 vol4 xv4 p4 #cdi1 #ahdc2 or ,philosophical ,magaz9e1 vol4 xxv4 pp4 #cef1 #dci1 ,may & ,june #ahdd4 ,:5 we look at any object1 ,,ab1 = example1 we see only "o po9t ( x di/9ctly4 ,9 ,fig4 #e ! po9t ,d only is se5 di/9ctly1 & e po9t f ,d to ,a1 & f ,d to ,b1 less di/9ctly4 ,! po9t ( di/9ct vision on ! ret9a is at d1 correspond+ ) ! po9t ,d ( ! object :i* is se5 di/9ctly4 ,?is po9t d is ! c5tre ( ! ret9a at ! extremity ( ! l9e ,,aha1 call$ ! optical axis ( ! eye1 pass+ ?r\gh ! c5tre ( ! l5s ,lh1 & ! c5tre ( ! pupil4 ,! po9t ( di/9ct vision d corresponds ) a small hole 9 ! ret9a call$ ! ,=am5 c5trale1 or c5tral hole1 f its be+ 9 ! c5tre ( ! membrane4 ,:5 we wi% to see ! po9ts ,a & ,b1 or any o!r po9t ( ! object1 we turn ! eye ^u !m1 s t _! image may fall ^u ! c5tral po9t d4 ,?is is done s easily & quickly t e po9t ( an object is se5 di/9ctly 9 an in/ant1 & we obta9 ! mo/ p]fect k ( its =m1 col\r1 & direction4 ,! law ( di/9ct vision may be ?us express$4 ,vision is mo/ di/9ct :5 x is p]=m$ by ! c5tral po9t ( ! ret9a1 & ! di/9ctness decreases ) ! di/ance f ! c5tral po9t4 ,x is a curi\s fact1 h[ev]1 t ! mo/ di/9ct po9t d is ! lea/ s5sitive to light1 & t ! s5sitiv5ess increases ) ! di/ance f t po9t4 ,?is is prov$ by ! rem>kable fact1 t :5 an a/ronom] _c see a v m9ute /> by look+ at x directly along ! optical axis d,d1 he c see x by look+ away f x1 & br++ its image ^u a m s5sitive "p ( ! ret9a4 ,b ?\gh we see ) "o eye ! direction 9 :i* any object or po9t ( an object is situat$1 we d n see its position1 or ! di/ance f ! eye at :i* x is plac$4 ,if a small lum9\s po9t or flame is put into a d>k room by ano!r p]son1 we _c ) "o eye =m any?+ l a correct e/imate ( its di/ance4 ,ev5 9 good light we _c ) "o eye snuff a c&le1 or p\r w9e into a small glass at arm's l5g?4 ,9 monocul> vision1 we le>n f exp]i5ce to e/imate all di/ances1 b p>ticul>ly great ones1 by v>i\s means1 :i* are call$ ! crit]ia ( di/ance2 b x is only ) bo? eyes t we c e/imate ) any?+ l accuracy ! di/ance ( objects n f> f u4 ,! crit]ia ( di/ance1 by :i* we are enabl$ ) "o eye to =m an approximate e/imate ( ! di/ance ( objects are five 9 numb]4 #a4 ,! int]position ( num]\s objects betwe5 ! eye & ! object ^: di/ance we are appreciat+4 ,a di/ance at sea appe>s mu* %ort] ?an ! same di/ance on l&1 m>k$ ) h\ses1 trees1 & o!r objects2 & = ! same reason1 ! sun & moon appe> m di/ant :5 ris+ or sett+ on ! horizon ( a flat c\ntry1 ?an :5 9 ! z5i?1 or at great altitudes4 #b4 ,! v>iation 9 ! app>5t magnitude ( kn[n objects1 su* z man1 animals1 trees1 doors & w9d[s ( h\ses4 ,if "o ( two m51 plac$ at diff]5t di/ances f u1 appe>s only half ! size ( ! o!r1 we _c be f> wrong 9 believ+ t ! smalle/ 9 appe>ance is at twice ! di/ance ( ! o!r4 ,x is possible t ! "o may be a dw>f1 & ! o!r ( gigantic /ature1 9 :i* case our judgm5t w\ld be errone\s1 b ev5 9 ?is case o!r crit]ia might enable u to correct x4 #c4 ,! degree ( vivacity 9 ! col\rs & t9ts ( objects4 #d4 ,! degree ( di/9ctness 9 ! outl9e & m9ute p>ts ( objects4 #e4 ,to ^! crit]ia we may add ! s5sation ( muscul> action1 or r ef=t1 by :i* we close ! pupil 9 accommodat+ ! eye to ne> di/ances1 & produce ! accommodation4 ,) all ^! means ( e/imat+ di/ances1 x is only by b9ocul> vision1 9 :i* we conv]ge ! optical axes ^u ! object1 t we h ! p[] ( see+ di/ance )9 a limit$ range4 ,b ?is is ! only po9t 9 :i* ,monocul> is inf]ior to ,b9ocul> vision4 ,9 ! foll[+ respects x is sup]ior to x4 #a4 ,:5 we look at oil pa9t+s1 ! v>ni% on _! surface reflects to ea* eye ! light :i* falls ^u x f c]ta9 p>ts ( ! room4 ,by clos+ "o eye we %ut out ! quantity ( reflect$ light :i* ent]s x4 ,pictures %\ld always be view$ by ! eye f>!/ f w9d[s or lights 9 ! ap>tm5t1 z light dim9i%es ! s5sibility ( ! eye to ! r$ rays4 #b4 ,:5 we view a picture ) bo? eyes1 we discov]1 f ! conv]g5cy ( ! optic axes1 t ! picture is on a plane surface1 e "p ( :i* is ne>ly equidi/ant f u4 ,b :5 we %ut "o eye1 we d n make ?is discov]y2 & !re=e ! effect ) :i* ! arti/ gives relief to ! pa9t+ ex]cises its :ole effect 9 deceiv+ u1 & h5ce1 9 monocul> vision1 ! relievo ( ! pa9t+ is mu* m complete4 ,?is influ5ce ov] our judgm5t is beautifully %ewn 9 view+1 ) "o eye1 photographs ei!r ( p]sons1 or l&scapes1 or solid objects4 ,aft] a little practice1 ! illusion is v p]fect1 & is aid$ by ! correct geometrical p]spective & *i>oscuro ( ! ,dagu]reotype or ,talbotype4 ,to ?is effect we may give ! "n ( ,monocul> ,relief1 :i*1 z we %all see1 is necess>ily inf]ior to ,b9ocul> ,relief1 :5 produc$ by ! /]eoscope4 #c4 ,z x v frequ5tly happ5s t "o eye has n exactly ! same focal l5g? z ! o!r1 & t1 :5 x has1 ! vision by "o eye is less p]fect ?an t by ! o!r1 ! picture =m$ by unit+ a p]fect ) a less p]fect picture1 or ) "o ( a diff]5t size1 mu/ be m imp]fect ?an ! s+le picture =m$ by "o eye4 ,,*apt] ,,iii4 ,,on ,,b9ocul> ,,vision1 ,,or ,,vision ,,) ,,two ,,eyes4 ,we h already se51 9 ! hi/ory ( ! /]eoscope1 t 9 ! b9ocul> vision ( objects1 ea* eye sees a diff]5t picture ( ! same object4 ,9 ord] to prove ?is1 we require only to look att5tively at our own h& held up be=e u1 & obs]ve h[ "s p>ts ( x disappe> ^u clos+ ea* eye4 ,?is exp]im5t proves1 at ! same "t1 9 opposition to ! op9ion ( ,bapti/a ,porta1 ,tacquet1 & o!rs1 t we always see two pictures ( ! same object comb9$ 9 "o4 ,9 confirmation ( ?is fact1 we h only to pu% aside "o eye1 & obs]ve ! image :i* belongs to x sep>ate f ! o!r1 & aga9 unite ) x :5 ! pressure is remov$4 ,x might h be5 suppos$ t an object se5 by bo? eyes w\ld be se5 twice z brightly z ) "o1 on ! same pr9ciple z ! light ( two c&les comb9$ is twice z bright z ! light ( "o4 ,t ?is is n ! case has be5 long kn[n1 & ,dr4 ,jur9 has prov$ by exp]im5ts1 :i* we h c>efully repeat$ & f\nd correct1 t ! brightness ( objects se5 ) two eyes is only _/? "p great] ?an :5 !y are se5 ) "o eye4#cb ,! cause ( ?is is well kn[n4 ,:5 bo? eyes are us$1 ! pupils ( ea* contract s z to admit ! prop] quantity ( light2 b ! mom5t we %ut ! "r eye1 ! pupil ( ! left dilates to ne>ly twice its size1 to comp5sate = ! loss ( light aris+ f ! %utt+ ( ! o!r4#cc #cb ,smi?'s ,opticks1 vol4 ii41 ,rem>ks1 p4 #ajg4 ,h>ris makes ! diff]5ce _/? or _/?2 ,optics1 p4 #aag4 #cc ,?is v>iation ( ! pupil is m5tion$ by ,bacon4 ,illu/ration3 ,,fig4 #f4 ,?is beautiful provision to supply ! prop] quantity ( light :5 we c use only "o eye1 answ]s a /ill m important purpose1 :i* has escap$ ! notice ( optical writ]s4 ,9 b9ocul> vision1 z we h j se51 c]ta9 p>ts ( objects are se5 ) bo? eyes1 & c]ta9 p>ts only ) "o2 s t1 if ! p>ts se5 ) bo? eyes 7 twice z bright1 or ev5 mu* bright] ?an ! p>ts se5 ) "o1 ! object w\ld appe> spott$1 f ! diff]5t brightness ( its p>ts4 ,9 ,fig4 #f1 = example1 7see p4 #ad17 ! areas ,,bfi & ,,cgi1 ! =m] ( :i* is se5 only by ! left eye1 ,d1 & ! latt] only by ! "r eye1 ,e1 & ! correspond+ areas on ! o!r side ( ! sph]e1 w\ld be only half z bright z ! portion ,,figh1 se5 ) bo? eyes1 & ! sph]e w\ld h a s+ul> appe>ance4 ,x has long be51 & /ill is1 a vex$ "q among philosoph]s1 h[ we see objects s+le ) two eyes4 ,bapti/a ,porta1 ,tacquet1 & o!rs1 got ov] ! difficulty by d5y+ ! fact1 & ma9ta9+ t we use only "o eye1 :ile o!r philosoph]s ( di/+ui%$ em95ce h adopt$ explanations /ill m gr\ndless4 ,! law ( visible direction supplies u ) ! true explanation4 ,illu/ration3 ,,fig4 #g4 ,let u fir/ suppose t we look ) bo? eyes1 ,r & ,l1 ,fig4 #g1 ^u a lum9\s po9t1 ,d1 :i* we see s+le1 ?\gh !re is a picture ( x on ! ret9a ( ea* eye4 ,9 look+ at ! po9t ,d we turn or conv]ge ! optical axes d,,hd1 d,h ,d1 ( ea* eye to ! po9t ,d1 an image ( :i* is =m$ at d 9 ! "r eye ,r1 & at d 9 ! left eye ,l4 ,9 virtue ( ! law ( visible direction ! po9t ,d is se5 9 ! direction d,d ) ! eye ,r1 & 9 ! direction d,d ) ! eye ,l1 ^! l9es be+ p]p5dicul> to ! ret9a at ! po9ts d1 d4 ,! "o image ( ! po9t ,d is !re=e se5 ly+ ^u ! o!r1 & consequ5tly se5 s+le4 ,consid]+ ,d1 !n1 z a s+le po9t ( a visible object ,,ab1 ! two eyes w see ! po9ts ,a & ,b s+le by ! same process ( turn+ or conv]g+ ^u !m _! optical axes1 & s quickly does ! po9t ( conv]g5ce pass backw>d & =w>d ov] ! :ole object1 t x appe>s s+le1 ?\gh 9 reality only "o po9t ( x c be se5 s+le at ! same in/ant4 ,! :ole picture ( ! l9e ,,ab1 z se5 ) "o eye1 seems to co9cide ) ! :ole picture ( x z se5 ) ! o!r1 & to appe> s+le4 ,! same is true ( a surface or area1 & also ( a solid body or a l&scape4 ,only "o po9t ( ea* is se5 s+le2 b we d n obs]ve t o!r po9ts are d\ble or indi/9ct1 because ! images ( !m are ^u p>ts ( ! ret9a :i* d n give di/9ct vision1 ow+ to _! di/ance f ! =am5 or po9t :i* gives di/9ct vision4 ,h5ce we see ! reason :y di/9ct vision is obta9$ only on "o po9t ( ! ret9a4 ,7 x o!rwise we %\ld see e o!r po9t d\ble :5 we look fix$ly ^u "o "p ( an object4 ,if 9 place ( two eyes we _h a hundr$1 capable ( conv]g+ _! optical axes to "o po9t1 we %\ld1 9 virtue ( ! law ( visible direction1 see only "o object4 ,! mo/ important advantage :i* we d]ive f ! use ( two eyes is to enable u to see di/ance1 or a ?ird dim5sion 9 space4 ,t we h ?is p[] has be5 d5i$ by ,dr4 ,b]keley1 & _m di/+ui%$ philosoph]s1 :o ma9ta9 t our p]ception ( di/ance is acquir$ by exp]i5ce1 by means ( ! crit]ia already m5tion$4 ,?is is und\bt$ly true = great di/ances1 b we %all pres5tly see1 f ! effects ( ! /]eoscope1 t ! successive conv]g5cy ( ! optic axes ^u two po9ts ( an object at diff]5t di/ances1 exhibits to u ! diff]5ce ( di/ance :5 we h no o!r possible means ( p]ceiv+ x4 ,if1 = example1 we suppose ,g1 ,d1 ,fig4 #g1 to be sep>ate po9ts1 or p>ts ( an object1 ^: di/ances are ,,g1 ,,d1 !n if we conv]ge ! optical axes ,,hg1 ,h ,g ^u ,g1 & next turn !m ^u ,d1 ! po9ts w appe> to be situat$ at ,g & ,d at ! di/ance ,,gd f ea* o!r1 & at ! di/ances ,,og1 ,,od f ! obs]v]1 al?\gh !re is no?+ :atev] 9 ! appe>ance ( ! po9ts1 or 9 ! lights & %ades ( ! object1 to indicate di/ance4 ,t ?is vision ( di/ance is n ! result ( exp]i5ce is obvi\s f ! fact t di/ance is se5 z p]fectly by *ildr5 z by adults2 & x has be5 prov$ by naturali/s t animals newly born appreciate di/ances ) ! greate/ correctness4 ,we %all aft]w>ds see t s infallible is our vision ( ne> di/ances1 t a body ^: real di/ance we c asc]ta9 by plac+ bo? our h&s ^u x1 w appe> at ! great] or less di/ance at :i* x is plac$ by ! conv]g5cy ( ! optical axes4 ,we are n[ prep>$ to und]/& g5]ally1 h[1 9 b9ocul> vision1 we see ! diff]5ce betwe5 a picture & a /atue1 & betwe5 a real l&scape & its repres5tation4 ,:5 we look at a picture ( :i* e "p is ne>ly at ! same di/ance f ! eyes1 ! po9t ( conv]g5ce ( ! optical axes is ne>ly at ! same di/ance f ! eyes2 b :5 we look at its orig9al1 :e!r x be a liv+ man1 a /atue1 or a l&scape1 ! optical axes are conv]g$ 9 rapid succession ^u ! nose1 ! eyes1 & ! e>s1 or ^u objects 9 ! =egr\nd1 ! middle & ! remote di/ances 9 ! l&scape1 & ! relative di/ances ( all ^! po9ts f ! eye are in/antly p]ceiv$4 ,! b9ocul> relief ?us se5 is greatly sup]ior to ! monocul> relief already describ$4 ,s9ce objects are se5 9 relief by ! app>5t union ( two dissimil> plane pictures ( !m =m$ 9 ea* eye1 x 0 a supposition h>dly to be ov]look$1 t if we c\ld del9eate two plane pictures ( a solid object1 z se5 dissimil>ly ) ea* eye1 & unite _! images by ! conv]g5cy ( ! optical axes1 we %\ld see ! solid ( :i* !y 7 ! repres5tation4 ,! exp]im5t 0 accord+ly made by m ?an "o p]son1 & 0 f\nd to succe$2 b z few h ! p[]1 or r ! art1 ( ?us conv]g+ _! optical axes1 x became necess>y to contrive an in/rum5t = do+ ?is4 ,! fir/ contrivances = ?is purpose 71 z we h already /at$1 made by ,mr4 ,elliot & ,mr4 ,:eat/one4 ,a description ( ^!1 & ( o!rs bett] fitt$ = ! purpose1 w be f\nd 9 ! foll[+ *apt]4 ,,*apt] ,,iv4 ,,description ,,( ,,! ,,ocul>1 ,,! ,,reflect+1 ,,& ,,! ,,l5ticul> ,,/]eoscopes4 ,al?\gh x is by ! comb9ation ( two plane pictures ( an object1 z se5 by ea* eye1 t we see ! object 9 relief1 yet ! relief is n obta9$ f ! m]e comb9ation or sup]position ( ! two dissimil> pictures4 ,! sup]position is effect$ by turn+ ea* eye ^u ! object1 b ! relief is giv5 by ! play ( ! optic axes 9 unit+1 9 rapid succession1 simil> po9ts ( ! two pictures1 & plac+ !m1 = ! mom5t1 at ! di/ance f ! obs]v] ( ! po9t to :i* ! axes conv]ge4 ,if ! eyes 7 to unite ! two images into "o1 & to reta9 _! p[] ( di/9ct vision1 :ile !y lo/ ! p[] ( *ang+ ! position ( _! optic axes1 no relief w\ld be produc$4 ,?is is equally true :5 we unite two dissimil> photographic pictures by fix+ ! optic axes on a po9t ne>] to or f>!r f ! eye4 ,?\gh ! pictures app>5tly coalesce1 yet ! relief is giv5 by ! subsequ5t play ( ! optic axes v>y+ _! angles1 & conv]g+ !mselves successively ^u1 & unit+1 ! simil> po9ts 9 ea* picture t correspond to diff]5t di/ances f ! obs]v]4 ,z v few p]sons h ! p[] ( ?us unit+1 by ! eyes alone1 ! two dissimil> pictures ( ! object1 ! /]eoscope has be5 contriv$ to enable !m to comb9e ! two pictures1 b x is n ! /]eoscope1 z has be5 imag9$1 t gives ! relief4 ,! in/rum5t is m]ely a sub/itute = ! muscul> p[] :i* br+s ! two pictures toge!r4 ,! relief is produc$1 z =m]ly1 solely by ! subsequ5t play ( ! optic axes4 ,if ! relief 7 ! effect ( ! app>5t union ( ! pictures1 we %\ld see x by look+ ) "o eye at ! comb9$ b9ocul> pictures--an exp]im5t :i* c\ld be made by optical means2 b we %\ld look = x 9 va94 ,! comb9$ pictures w\ld be z flat z ! comb9ation ( two simil> pictures4 ,^! exp]im5ts require to be made ) a ?or\gh k ( ! subject1 = :5 ! eyes are conv]g$ on "o po9t ( ! comb9$ picture1 ?is po9t has ! relief1 or di/ance f ! eye1 correspond+ to ! angle ( ! optic axes1 & !re=e ! adjac5t po9ts are1 z x 71 br\ght into a sort ( indi/9ct relief along ) x2 b ! optical read] w see at once t ! true b9ocul> relief _c be giv5 to any o!r p>ts ( ! picture1 till ! axes ( ! eyes are conv]g$ ^u !m4 ,^! views w be m readily compreh5d$ :5 we h expla9$1 9 a subsequ5t *apt]1 ! !ory ( /]eoscopic vision4 ,! ,ocul> ,/]eoscope4 ,we h already /at$ t objects are se5 9 p]fect relief :5 we unite two dissimil> photographic pictures ( !m1 ei!r by conv]g+ ! optic axes ^u a po9t s f> 9 front ( ! pictures or s f> beyond !m1 t two ( ! f\r images are comb9$4 ,9 bo? ^! cases ea* picture is se5 d\ble1 & :5 ! two inn]mo/ ( ! f\r1 ?us produc$1 unite1 ! orig9al object is se5 9 relief4 ,! simple/ ( ^! me?ods is to conv]ge ! optical axes to a po9t ne>] to u ?an ! pictures1 & ?is may be be/ done by hold+ up a f+] betwe5 ! eyes & ! pictures1 & plac+ x at su* a di/ance t1 :5 we see x s+le1 ! two inn]mo/ ( ! f\r pictures are unit$4 ,if ! f+] is held up ne> ! dissimil> pictures1 !y w be slightly d\bl$1 ! two images ( ea* ov]lapp+ "o o!r2 b by br++ ! f+] ne>] ! eye1 & see+ x s+ly & di/9ctly1 ! ov]lapp+ images w sep>ate m & m till !y unite4 ,we h1 !re=e1 made our eyes a /]eoscope1 & we may1 ) great propriety1 call x ! ,ocul> ,/]eoscope4 ,if we wi% to magnify ! picture 9 relief1 we h only to use convex spectacles1 :i* w produce ! requisite magnify+ p[]2 or :at is /ill bett]1 to magnify ! unit$ pictures ) a p[]ful read+-glass4 ,! two s+le images are hid by advanc+ ! read+-glass1 & ! o!r two pictures are kept unit$ ) a less /ra9 ^u ! eyes4 ,z v few p c use _! eyes 9 ?is mann]1 "s in/rum5tal auxili>y became necess>y1 & x appe>s to u /range t ! simple/ me?od ( do+ ?is did n occur to ,mr4 ,elliot & ,mr4 ,:eat/one1 :o fir/ ?\ght ( giv+ u ! help ( an in/rum5t4 ,by enabl+ ! left eye to place an image ( ! left-h& picture ^u ! "r-h& picture1 z se5 by ! nak$ eye1 we %\ld h obta9$ a simple in/rum5t1 :i* might be call$ ! ,monocul> ,/]eoscope1 & :i* we %all h occasion to describe4 ,! same contrivance appli$ also to ! "r eye1 w\ld make ! in/rum5t ,b9ocul>4 ,ano!r simple contrivance = assi/+ ! eyes w\ld h be5 to furni% !m ) a m9ute op]a-glass1 or a small a/ronomical telescope ab\t an in* long1 :i*1 :5 held 9 ! h& or plac$ 9 a pyramidal box1 w\ld unite ! dissimil> pictures ) ! greate/ facility & p]fection4 ,?is =m ( ! /]eoscope w be aft]w>ds describ$ "u ! "n ( ! ,op]a-,glass ,/]eoscope4 ,illu/ration3 ,,fig4 #h4 ,description ( ! ,ocul> ,/]eoscope4 ,a /]eoscope ^u ! pr9ciple already describ$1 9 :i* ! eyes alone are ! ag5t1 0 contriv$1 9 #ahcd1 by ,mr4 ,elliot1 z we h already _h occasion to /ate4 ,he plac$ ! b9ocul> pictures1 describ$ 9 ,*apt] ,i41 at "o end ( a box1 & )\t ! aid ei!r ( l5ses or mirrors1 he obta9$ a l&scape 9 p]fect relief4 ,i h exam9$ ?is /]eoscope1 & h giv51 9 ,fig4 #h1 an accurate ?\gh r$uc$ draw+ ( ! b9ocul> pictures execut$ & us$ by ,mr4 ,elliot4 ,i h also unit$ ! two orig9al pictures by ! conv]g5cy ( ! optic axes beyond !m1 & h ?us se5 ! l&scape 9 true relief4 ,to del9eate ^! b9ocul> pictures ^u /]eoscopic pr9ciples 0 a bold und]tak+1 & e/abli%es1 beyond all controv]sy1 ,mr4 ,elliot's claim to ! inv5tion ( ! ocul> /]eoscope4 ,if we unite ! two pictures 9 ,fig4 #h1 by conv]g+ ! optic axes to a po9t ne>] ! eye ?an ! pictures1 we %all see di/9ctly ! /]eoscopic relief1 ! moon be+ 9 ! remote di/ance1 ! cross 9 ! middle di/ance1 & ! /ump ( a tree 9 ! =egr\nd4 ,if we place ! two pictures z 9 ,fig4 #i1 :i* is ! position !y _h 9 ,mr4 ,elliot's box1 & unite !m1 by look+ at a po9t beyond !m we %all also obs]ve ! /]eoscopic relief4 ,9 ?is position ,mr4 ,elliot saw ! relief )\t any ef=t1 & ev5 )\t be+ consci\s t he 0 n view+ ! pictures "u ord9>y vision4 ,?is t5d5cy ( ! optic axes to a di/ant conv]g5cy is s r>e t ,i h met ) x only 9 "o p]son4 ,illu/ration3 ,,fig4 #i4 ,z ! relief produc$ by ! union ( su* imp]fect pictures 0 suffici5t only to %ew ! correctness ( ! pr9ciple1 ! fri5ds to :om ,mr4 ,elliot %ew$ ! in/rum5t ?\ght x ( little int]e/1 & he !re=e nei!r prosecut$ ! subject1 nor publi%$ any acc\nt ( 8 contrivance4 ,mr4 ,:eat/one sugge/$ a simil> contrivance1 )\t ei!r mirrors or l5ses4 ,9 ord] to unite ! pictures by conv]g+ ! optic axes to a po9t betwe5 !m & ! eye1 he propos$ to place !m 9 a box to hide ! lat]al image & assi/ 9 mak+ !m unite ) ! nak$ eyes4 ,9 ord] to produce ! union by look+ at a po9t beyond ! picture1 he sugge/$ ! use ( 8a pair ( tubes capable ( be+ incl9$ to ea* o!r at v>i\s angles10 ! pictures be+ plac$ on a /& 9 front ( ! tubes4 ,^! contrivances1 h[ev]1 ?\gh auxili>y to ! use ( ! nak$ eyes1 7 sup]s$$ by ! ,reflect+ ,/]eoscope1 :i* we %all n[ describe4 ,description ( ! ,reflect+ ,/]eoscope4 ,?is =m ( ! /]eoscope1 :i* we owe to ,mr4 ,:eat/one1 is %ewn 9 ,fig4 #aj1 & is describ$ by him 9 ! foll[+ t]ms3--8,,aa are two plane mirrors1 7:e!r ( glass or metal is n /at$17 ab\t f\r in*es squ>e1 ins]t$ 9 frames1 & s adju/$ t _! backs =m an angle ( #ij ) ea* o!r2 ^! mirrors are fix$ by _! common edge aga9/ an upright ,b1 or1 :i* 0 less easy to repres5t 9 ! draw+ aga9/ ! middle ( a v]tical bo>d1 cut away 9 su* a mann] z to all[ ! eyes to be plac$ be=e ! two mirrors4 ,c1 ,c are two slid+ bo>ds1 to :i* are atta*$ ! upright bo>ds ,d1 ,d1 :i* may ?us be remov$ to diff]5t di/ances f ! mirrors4 ,9 mo/ ( ! exp]im5ts h]eaft] to be detail$ x is necess>y t ea* upright bo>d %all be at ! same di/ance f ! mirror :i* is opposite to x4 ,to facilitate ?is d\ble adju/m5t1 ,i employ a "r & a left-h&$ wood5 screw1 r1 l2 ! two ends ( ?is comp\nd screw pass ?r\gh ! nuts e1 e1 :i* are fix$ to ! l[] p>ts ( ! upright bo>ds ,d1 ,d1 s t by turn+ ! screw p9 p "o way ! two bo>ds w approa*1 & by turn+ !m ! o!r !y w rec$e f ea* o!r1 "o always pres]v+ ! same di/ance z ! o!r f ! middle l9e f2 ,e1 ,e are pannels to :i* ! pictures are fix$ 9 su* mann] t _! correspond+ horizontal l9es %all be on ! same level2 ^! pannels are capable ( slid+ backw>ds or =w>ds 9 grooves on ! upright bo>ds ,d1 ,d4 ,! app>atus hav+ be5 describ$1 x n[ rema9s to expla9 ! mann] ( us+ x4 ,! obs]v] mu/ place 8 eyes z ne> z possible to ! mirrors1 ! "r eye be=e ! "r-h& mirror1 & ! left eye be=e ! left-h& mirror1 & he mu/ move ! slid+ pannels ,e1 ,e to or f him till ! two reflect$ images co9cide at ! int]section ( ! optic axes1 & =m an image ( ! same app>5t magnitude z ea* ( ! compon5t pictures4 ,! picture w1 inde$1 co9cide :5 ! slid+ pannels are 9 a v>iety ( diff]5t positions1 &1 consequ5tly1 :5 view$ "u diff]5t incl9ations ( ! optic axes1 b !re is only "o position 9 :i* ! b9ocul> image w be imm$iately se5 s+le1 ( its prop] magnitude1 & )\t fatigue to ! eyes1 because 9 ?is position only ! ord9>y relations betwe5 ! magnitude ( ! pictures on ! ret9a1 ! incl9ation ( ! optic axes1 & ! adaptation ( ! eye to di/9ct vision at diff]5t di/ances1 are pres]v$4 ,9 all ! exp]im5ts detail$ 9 ! pres5t memoir ,i %all suppose ^! relations to rema9 undi/urb$1 & ! optic axes to conv]ge ab\t six or eight in*es be=e ! eyes4 ,illu/ration3 ,,fig4 #aj4 8,if ! pictures are all drawn to be se5 ) ! same incl9ation ( ! optic axes ! app>atus may be simplifi$ by omitt+ ! screw rl1 & fix+ ! upright bo>ds ,d1 ,d at ! prop] di/ance4 ,! slid+ pannels may also be disp5s$ )1 & ! draw+s !mselves be made to slide 9 ! grooves40 ,! figures to :i* ,mr4 ,:eat/one appli$ ?is in/rum5t 7 pairs ( outl9e repres5tations ( objects ( ?ree dim5sions1 su* z a cube1 a cone1 ! fru/um ( a squ>e pyramid1 :i* is %ewn on "o side ( ,e1 ,e 9 ,fig4 #aj1 & 9 o!r figures2 & he employ$ !m1 z he obs]ves1 8= ! purpose ( illu/ration1 = _h ei!r %ad+ or col\r+ be5 introduc$ x might be suppos$ t ! effect 0 :olly or 9 "p due to ^! circum/ances1 :]eas1 by leav+ !m out ( consid]ation1 no room is left to d\bt t ! entire effect ( relief is ow+ to ! simultane\s p]ception ( ! two monocul> projections1 "o on ea* ret9a40 8,c>eful att5tion10 he adds1 8w\ld enable an arti/ to draw & pa9t ! two compon5t pictures1 s z to pres5t to ! m9d ( ! obs]v]1 9 ! resultant p]ception1 p]fect id5tity ) ! object repres5t$4 ,fl[]s1 cry/als1 bu/s1 vases1 in/rum5ts ( v>i\s k9ds1 c41 might ?us be repres5t$1 s z n to be di/+ui%$ by sight f ! real objects !mselves40 ,?is expectation has nev] be5 realiz$1 = x is obvi\sly beyond ! rea* ( ! highe/ art to draw two copies ( a fl[] or a bu/ ) su* accuracy ( outl9e or col\r z to produce 8p]fect id5tity10 or any?+ approa*+ to x1 8) ! object repres5t$40 ,photography alone c furni% u ) su* repres5tations ( natural & artificial objects2 & x is s+ul> t nei!r ,mr4 ,elliot nor ,mr4 ,:eat/one %\ld h avail$ !mselves ( ! well-kn[n photographic process ( ,mr4 ,w$gewood & ,sir ,humphry ,davy1 :i*1 z ,mr4 ,w$gewood rem>ks1 want$ only 8a me?od ( prev5t+ ! un%ad$ p>ts ( ! del9eation f be+ col\r$ by exposure to ! day1 to r5d] ! process z useful z x is elegant40 ,:5 ! two dissimil> photographs 7 tak5 !y c\ld h be5 us$ 9 ! /]eoscope 9 c&le-light1 or 9 fa9t daylight1 till !y disappe>$1 or p]man5t outl9es ( !m might h be5 tak5 & col\r$ aft] nature4 ,mr4 ,fox ,talbot's beautiful process ( produc+ p]man5t photographs 0 communicat$ to ! ,royal ,society 9 ,janu>y #ahci1 b no attempt 0 made till "s ye>s lat] to make x available = ! /]eoscope4 ,9 a *apt] on b9ocul> pictures1 & ! me?od ( execut+ !m 9 ord] to reproduce1 ) p]fect accuracy1 ! objects :i* !y repres5t1 we %all recur to ?is bran* ( ! subject4 ,^u obta9+ "o ( ^! reflect+ /]eoscopes z made by ! celebrat$ optician1 ,mr4 ,&rew ,ross1 ,i f\nd x to be v ill adapt$ = ! purpose ( unit+ dissimil> pictures1 & to be imp]fect 9 v>i\s respects4 ,its imp]fections may be ?us enum]at$3-- #a4 ,x is a clumsy & unmanageable app>atus1 r ?an an in/rum5t = g5]al use4 ,! "o con/ruct$ = me 0 #af in*es long1 #f in*es broad1 & #h in*es high4 #b4 ,! loss ( light occasion$ by reflection f ! mirrors is v great4 ,9 all optical in/rum5ts :]e images are to be =m$1 & light is valuable1 mirrors & specula h be5 discont9u$4 ,reflect+ microscopes h ceas$ to be us$1 b l>ge telescopes1 su* z ^? ( ,sir ,w4 & ,sir ,john ,h]s*el1 ,"l ,rosse1 & ,mr4 ,lassel1 7 necess>ily made on ! reflect+ pr9ciple1 f ! impossibility ( obta9+ plates ( glass ( suffici5t size4 #c4 ,9 us+ glass mirrors1 ( :i* ! reflect+ /]eoscope is always made1 we n only lose mu* m ?an half ! light by ! reflections f ! glass & ! metallic surface1 & ! absorb+ p[] ( ! glass1 b ! images produc$ by reflection are made indi/9ct by ! oblique incid5ce ( ! rays1 :i* sep>ates ! image produc$ by ! glass surface f ! m brilliant image produc$ by ! metallic surface4 #d4 ,9 all reflections1 z ,sir ,isaac ,newton /ates1 ! errors are great] ?an 9 refraction4 ,) glass mirrors 9 ! /]eoscope1 we h f\r refractions 9 ea* mirror1 & ! light transmitt$ ?r\gh twice ! ?ickness ( ! glass1 :i* lead to two s\rces ( error4 #e4 ,ow+ to ! exposure ( ! eye & e "p ( ! app>atus to light1 ! eye itself is unfitt$ = di/9ct vision1 & ! b9ocul> pictures become indi/9ct1 especially if !y are ,dagu]reotypes1#cd by reflect+ ! light incid5t f e "p ( ! room ^u _! glass or metallic surface4 #cd ,mr4 ,:eat/one himself says1 8t x is some:at difficult to r5d] ! two ,dagu]reotypes equally visible40--,phil4 ,trans41 #aheb1 p4 #f4 #f4 ,! reflect+ /]eoscope is inapplicable to ! beautiful b9ocul> slides :i* are n[ be+ tak5 = ! l5ticul> /]eoscope 9 e "p ( ! _w1 & ev5 if we cut 9 two ^? on pap] & silv]-plate1 !y w\ld give1 9 ! reflect+ in/rum5t1 conv]se pictures1 ! "r-h& "p ( ! picture be+ plac$ on ! left-h& side1 & vice v]sa4 #g4 ,) transp>5t b9ocul> slides cut 9 two1 we c\ld obta9 pictures by reflection t are n conv]se2 b 9 us+ !m1 we w\ld require to h two lights1 "o opposite ea* ( ! pictures1 :i* c seldom be obta9$ 9 daylight1 & :i* x is inconv5i5t to h at night4 ,ow+ to ^! & o!r causes1 ! reflect+ /]eoscope nev] came into use1 ev5 aft] photography 0 capable ( supply+ b9ocul> pictures4 ,z a set-(f aga9/ ^! disadvantages1 x has be5 av]r$ t 9 ! reflect+ /]eoscope we c use l>g] pictures1 b ?is1 z we %all %ew 9 a future *apt]1 is altoge!r an errone\s ass]tion4 ,description ( ! ,l5ticul> ,/]eoscope4 ,hav+ f\nd t ! reflect+ /]eoscope1 :5 int5d$ to produce accurate results1 possess$ ! defects :i* ,i h describ$1 & 0 ill fitt$ = g5]al use1 bo? f its size & its price1 x occurr$ to me t ! union ( ! dissimil> pictures c\ld be bett] effect$ by means ( l5ses1 & t a consid]able magnify+ p[] w\ld be ?us obta9$1 )\t any addition to ! in/rum5t4 ,illu/ration3 ,,fig4 #aa4 ,if we suppose ,a1 ,b1 ,fig4 #aa1 to be two portraits1--,a a portrait ( a g5tleman1 z se5 by ! left eye ( a p]son view+ him at ! prop] di/ance & 9 ! be/ position1 & ,b 8 portrait z se5 by ! "r eye1 ! purpose ( ! /]eoscope is to place ^! two pictures1 or r _! images1 "o above ! o!r4 ,! me?od ( do+ ?is by l5ses may be expla9$1 to p]sons n acqua9t$ ) optics1 9 ! foll[+ mann]3-- ,if we look at ,a ) "o eye ?r\gh ! c5tre ( a convex glass1 ) :i* we c see x di/9ctly at ! di/ance ( #f in*es1 :i* is call$ its focal di/ance1 x w be se5 9 its place at ,a4 ,if we n[ move ! l5s f "r to left1 ! image ( ,a w move t[>ds ,b2 & :5 x is se5 ?r\gh ! "r-h& edge ( ! l5s1 ! image ( ,a w h rea*$ ! position ,c1 half-way betwe5 ,a & ,b4 ,if we repeat ?is exp]im5t ) ! portrait ,b1 & move ! l5s f left to "r1 ! image ( ,b w move t[>ds ,a2 & :5 x is se5 ?r\gh ! left-h& edge ( ! l5s1 ! image ( ,b w h rea*$ ! position ,c4 ,n[1 x is obvi\sly by ! "r-h& half ( ! l5s t we h transf]r$ ! image ( ,a to ,c1 & by ! left-h& half t we h transf]r$ ! image ( ,b to ,c4 ,if we cut ! l5s 9 two1 & place ! halves--"o 9 front ( ea* picture at ! di/ance ( #b in*es--9 ! same position 9 :i* !y 7 :5 ,a 0 transf]r$ to ,c & ,b to ,c1 !y w /& z 9 ,fig4 #ab1 & we %all see ! portraits ,a & ,b unit$ into "o at ,c1 & /&+ out 9 beautiful relief1--a result :i* w be expla9$ 9 a subsequ5t *apt]4 ,illu/ration3 ,,fig4 #ab4 ,! same effect w be produc$ by qu>t] l5ses1 su* z ^? %ewn 9 ,fig4 #ac4 ,^! l5ses are cut into a r\nd or squ>e =m1 & plac$ 9 tubes1 z repres5t$ at ,r1 ,l1 9 ,fig4 #ad1 :i* is a draw+ ( ! ,l5ticul> ,/]eoscope4 ,illu/ration3 ,,fig4 #ac4 ,?is in/rum5t consi/s ( a pyramidal box1 ,fig4 #ad1 black5$ inside1 & hav+ a lid1 ,,cd1 = ! admission ( light :5 requir$4 ,! top ( ! box consi/s ( two p>ts1 9 "o ( :i* is ! "r-eye tube1 ,r1 conta9+ ! l5s ,g1 ,fig4 #ac1 & 9 ! o!r ! left-eye tube1 ,l1 conta9+ ! l5s ,h4 ,! two p>ts :i* hold ! l5ses1 & :i* =m ! top ( ! box1 are (t5 made to slide 9 grooves1 s z to suit diff]5t p]sons ^: eyes1 plac$ at ,r1 ,l1 are m or less di/ant4 ,?is adju/m5t may be made by v>i\s pieces ( me*anism4 ,! simple/ ( ^! is a jo9t$ p>allelogram1 mov$ by a screw =m+ its long] diagonal1 & work+ 9 nuts fix$ on ! top ( ! box1 s z to sep>ate ! semi-l5ses1 :i* foll[ ! movem5ts ( ! obtuse angles ( ! p>allelogram4 ,! tubes ,r1 ,l move up & d[n1 9 ord] to suit eyes ( diff]5t focal l5g?s1 b !y are prev5t$ f turn+ r\nd by a brass p91 :i* runs 9 a groove cut ?r\gh ! movable tube4 ,imm$iately bel[ ! eye-tubes ,r1 ,l1 !re %\ld be a groove1 ,g1 = ! introduction ( convex or concave l5ses1 :5 requir$ = v long-sight$ or %ort-sight$ p]sons1 or = col\r$ glasses & o!r purposes4 ,illu/ration3 ,,fig4 #ad4 ,if we n[ put ! slide ,,ab1 ,fig4 #aa1 into ! horizontal op5+ at ,s1 turn+ up ! sneck above ,s to prev5t x f fall+ out1 & place ourselves beh9d ,r1 ,l1 we %all see1 by look+ ?r\gh ,r ) ! "r eye & ,l ) ! left eye1 ! two images ,a1 ,b unit$ 9 "o1 & 9 ! same relief z ! liv+ p]son :om !y repres5t4 ,no portrait ev] pa9t$1 & no /atue ev] c>v$1 approximate 9 ! slighte/ degree to ! liv+ reality n[ be=e u4 ,if we %ut ! "r eye ,r we see ) ! left eye ,l m]ely ! portrait ,a1 b x has n[ sunk into a flat picture1 ) only monocul> relief4 ,by clos+ ! left eye we %all see m]ely ! portrait ,b1 hav+1 l ! o!r1 only monocul> relief1 b a relief great] ?an ! be/-pa9t$ pictures c possibly h1 :5 se5 ev5 ) "o eye4 ,:5 we op5 bo? eyes1 ! two portraits in/antly />t into all ! r\ndness & solidity ( life4 ,_m p]sons exp]i5ce a difficulty 9 see+ ! portraits s+le :5 !y fir/ look into a /]eoscope1 9 consequ5ce ( _! eyes hav+ less p[] ?an common ov] _! optic axes1 or f _! be+ m or less di/ant ?an two & a half in*es1 ! av]age di/ance4 ,! two images ?us produc$ frequ5tly disappe> 9 a few m9utes1 ?\gh sometimes x requires a little pati5ce & "s practice to see ! s+le image4 ,we h kn[n p]sons :o h lo/ ! p[] ( unit+ ! images1 9 consequ5ce ( hav+ discont9u$ ! use ( ! in/rum5t = "s mon?s2 b !y h always acquir$ x aga9 aft] a little practice4 ,if ! portraits or o!r pictures are ^u opaque pap] or silv]-plate1 ! /]eoscope1 :i* is usually held 9 ! left h&1 mu/ be incl9$ s z to all[ ! light ( ! sky1 or any o!r light1 to illum9ate e "p ( ! pictures4 ,if ! pictures are on transp>5t pap] or glass1 we mu/ %ut ! lid ,,cd1 & hold up ! /]eoscope aga9/ ! sky or ! artificial light1 = :i* purpose ! bottom ( ! in/rum5t is made ( glass f9ely gr\nd on ! outside1 or has two op5+s1 ! size ( ea* ( ! b9ocul> pictures1 cov]$ ) f9e pap]4 ,9 us+ ! /]eoscope ! obs]v] %\ld always be seat$1 & x is v conv5i5t to h ! in/rum5t m\nt$ l a telescope1 ^u a /&1 ) a weight & pulley = regulat+ ! motion ( ! lid ,,cd4 ,! l5ticul> /]eoscope may be con/ruct$ ( v>i\s mat]ials & 9 diff]5t =ms4 ,i _h !m made orig9ally ( c>d-bo>d1 t9-plate1 wood1 & brass2 b wood is c]ta9ly ! be/ mat]ial :5 *eapness is n an object4 ,illu/ration3 ,,fig4 #ae4 ,"o ( ! e>lie/ =ms :i* ,i adopt$ 0 t :i* is %ewn 9 ,fig4 #ae1 z made by ,m4 ,duboscq 9 ,p>is1 & :i* may be call$ /]eoscopic spectacles4 ,! two-eye l5ses ,l1 ,r are held by ! h&le ,h1 s t we c1 by mov+ !m to or f ! b9ocul> pictures1 obta9 di/9ct vision & unite !m 9 "o4 ,! effect1 h[ev]1 is n s good z t :i* is produc$ :5 ! pictures are plac$ 9 a box4 ,! same objection applies to a =m o!rwise m conv5i5t1 :i* consi/s 9 fix+ a cyl9drical or squ>e rod ( wood or metal to ,c1 ! middle po9t betwe5 ,l & ,r4 ,! b9ocul> slide hav+ a hole 9 ! middle betwe5 ! two pictures is mov$ along ?is rod to its prop] di/ance f ! l5ses4 ,illu/ration3 ,,fig4 #af4 ,ano!r =m1 analog\s to ?is1 b )\t ! means ( mov+ ! pictures1 is %ewn 9 ,fig4 #af1 z made by ,m4 ,duboscq4 ,! adju/m5t is effect$ by mov+ ! eye-pieces 9 _! respective tubes1 & by means ( a screw-nut1 %ewn above ! eye-pieces1 !y c be adapt$ to eyes plac$ at diff]5t di/ances f "o ano!r4 ,! advantage ( ?is =m1 if x is an advantage1 consi/s 9 all[+ u to use l>g] pictures ?an c be admitt$ into ! box-/]eoscope ( ! usual size4 ,a box-/]eoscope1 h[ev]1 ( ! same size1 w\ld h ! same prop]ty & o!r advantages n possess$ by ! op5 in/rum5t4 ,ano!r =m ( ! l5ticul> /]eoscope1 "u ! "n ( ! cosmorama /]eoscope1 has be5 adopt$ by ,mr4 ,knight4 ,! box is rectangul> in/ead ( pyramidal1 & ! adju/m5t to di/9ct vision is made by pull+ out or pu%+ 9 a "p ( ! box1 in/ead ( ! common & bett] me?od ( mov+ ea* l5s sep>ately4 ,! illum9ation ( ! pictures is made 9 ! same mann] z 9 ! ,fr5* in/rum5t1 call$ ! cosmorama1 = exhibit+ dissolv+ views4 ,! l5ses are l>ge 9 surface1 :i*1 )\t any reason1 is suppos$ to facilitate ! view ( ! b9ocul> pictures1 & ! in/rum5t is support$ 9 a horizontal position ^u a /&4 ,!re is no contrivance = adju/+ ! di/ance ( ! l5ses to ! di/ance betwe5 ! eyes1 & ow+ to ! quantity ( light :i* gets into ! int]ior ( ! box1 ! /]eoscopic picture is injur$ by false reflections1 & ! s5sibility ( ! eyes dim9i%$4 ,! exclusion ( all light f ! eyes1 & ( e o!r light f ! picture b t :i* illum9ates x1 is ess5tially necess>y to ! p]fection ( /]eoscopic vision4 ,:5 by means ( any ( ^! in/rum5ts we h succe$$ 9 =m+ a s+le image ( ! two pictures1 we h only1 z ,i h already expla9$1 plac$ ! "o picture above ! o!r1 9 s f> z ! /]eoscope is conc]n$4 ,x is by ! subsequ5t action ( ! two eyes t we obta9 ! desir$ relief4 ,7 we to unite ! two pictures :5 transp>5t1 & take a copy ( ! comb9ation by ! be/ possible cam]a1 ! result w\ld be a blurr$ picture1 9 :i* none ( ! po9ts or l9es ( ! "o w\ld be unit$ ) ! po9ts or l9es ( ! o!r2 b 7 we to look at ! comb9ation ) bo? eyes ! blurr$ picture w\ld />t into relief1 ! eyes unit+ 9 succession ! sep>ate po9ts & l9es ( :i* x is compos$4 ,n[1 s9ce1 9 ! /]eoscope1 :5 look$ into ) two eyes1 we see ! picture 9 relief ) ! same accuracy z1 9 ord9>y b9ocul> vision1 we see ! same object 9 relief by unit+ on ! ret9a two pictures exactly ! same z ! b9ocul> ones1 ! m]e /atem5t ( ?is fact has be5 reg>d$ z ! !ory ( ! /]eoscope4 ,we %all see1 h[ev]1 t x is n1 & t x rema9s to be expla9$1 m m9utely ?an we h done 9 ,*apt] ,,iii41 bo? h[ we see objects 9 relief 9 ord9>y b9ocul> vision1 & h[ we see !m 9 ! same relief by unit+ ocul>ly1 or 9 ! /]eoscope1 two dissimil> images ( !m4 ,be=e proce$+1 h[ev]1 to ?is subject1 we mu/ expla9 ! mann] 9 :i* half & qu>t] l5ses unite ! two dissimil> pictures4 ,illu/ration3 ,,fig4 #ag4 ,9 ,fig4 #ag is %ewn a semi-l5s ,,mn1 ) its section ,m,n4 ,if we look at any object successively ?r\gh ! portions ,,aa,a 9 ! semi-l5s ,,mn1 correspond+ to aaa 9 ! section ,m,n1 :i* is ! same z 9 a qu>t]-l5s1 ! object w be magnifi$ equally 9 all ( !m1 b x w be m displac$1 or m refract$1 t[>ds ,n1 by look+ ?r\gh ,a or a ?an ?r\gh ,a or a1 & mo/ ( all by look+ ?r\gh ,a or a1 ! refraction be+ greate/ at ,a or a1 less at ,a or a1 & /ill less at ,a or a4 ,by means ( a semi-l5s1 or a qu>t] ( a l5s ( ! size ( ,,mn1 we c1 ) an ap]ture ( ! size ( ,a1 obta9 ?ree diff]5t degrees ( displacem5t or refraction1 )\t any *ange ( ! magnify+ p[]4 ,if we use a ?ick] l5s1 z %ewn at ,m,nnm1 keep+ ! curvature ( ! surface ! same1 we increase ! refract+ angle at its m>g9 ,nn1 we c produce any degree ( displacem5t we require1 ei!r = ! purposes ( exp]im5t1 or = ! duplication ( l>ge b9ocul> pictures4 ,:5 two half or qu>t] l5ses are us$ z a /]eoscope1 ! displacem5t ( ! two pictures is produc$ 9 ! mann] %ewn 9 ,fig4 #ah1 :]e ,,ll is ! l5s = ! left eye ,e1 & ,l,l t = ! "r eye ,e1 plac$ s t ! middle po9ts1 no1 no1 ( ea* are #b in*es di/ant1 l ! two eyes4 ,! two b9ocul> pictures :i* are to be unit$ are %ewn at ab1 ,,ab1 & plac$ at ne>ly ! same di/ance4 ,! pictures be+ fix$ 9 ! focus ( ! l5ses1 ! p5cils ano1 ,ano1 bno1 ,bno1 w be refract$ at ! po9ts n1 o1 n1 o1 & at _! po9ts ( incid5ce on ! second surface1 s z to ent] ! eyes1 ,e1 ,e1 9 p>allel directions1 ?\gh n %ewn 9 ! ,figure4 ,! po9ts a1 ,a1 ( "o ( ! pictures1 w !re=e be se5 di/9ctly 9 ! direction ( ! refract$ ray--t is1 ! p5cils an1 ao1 issu+ f a1 w be se5 z if !y came f a1 & ! p5cils bn1 bo1 z if !y came f b1 s t ab w be transf]r$ by refraction to ab4 ,9 l mann]1 ! picture ,,ab w be transf]r$ by refraction to ,a,b1 & ?us unit$ ) ab4 ,illu/ration3 ,,fig4 #ah ,! pictures ab1 ,,abb ?us unit$ are m]ely circles1 & w !re=e be se5 z a s+le circle at ,a,b4 ,b if we suppose ab to be ! base ( ! fru/um ( a cone1 & cd its summit1 z se5 by ! left eye1 & ! circles ,,ab1 ,,cd to repres5t ! base & summit ( ! same solid z se5 by ! "r eye1 !n x is obvi\s t :5 ! pictures ( cd & ,,cd are simil>ly displac$ or refract$ by ! l5ses ,,ll ,l,l1 s t cc is equal to a,a & ,,dd to ,,bb1 ! circles w n be unit$1 b w ov]lap "o ano!r z at ,c,d1 cd1 9 consequ5ce ( be+ c>ri$ beyond _! place ( union4 ,! eyes1 h[ev]1 w in/antly unite !m into "o by conv]g+ _! axes to a remot] po9t1 & ! unit$ circles w rise f ! pap]1 or f ! base ,a,b1 & place ! s+le circle at ! po9t ( conv]g5ce1 z ! summit ( ! fru/um ( a holl[ cone ^: base is ,a,b4 ,if cd1 ,,cd _h be5 f>!r f "o ano!r ?an ab1 ,,ab1 z 9 ,figs4 #bj & #ba1 !y w\ld /ill h ov]lapp$ ?\gh n c>ri$ up to _! place ( union4 ,! eyes1 h[ev]1 w in/antly unite !m by conv]g+ _! axes to a ne>] po9t1 & ! unit$ circles w rise f ! pap]1 or f ! base ,,ab1 & =m ! summit ( ! fru/um ( a rais$ cone ^: base is ,a,b4 ,9 ! prec$+ illu/ration we h suppos$ ! solid to consi/ only ( a base & a summit1 or ( p>ts at two diff]5t di/ances f ! eye2 b :at is true ( two di/ances is true ( any numb]1 & ! in/ant t ! two pictures are comb9$ by ! l5ses !y w exhibit 9 relief ! body :i* !y repres5t4 ,if ! pictures are refract$ too little1 or if !y are refract$ too mu*1 s z n to be unit$1 _! t5d5cy to unite is s great1 t !y are soon br\ght toge!r by ! increas$ or dim9i%$ conv]g5cy ( ! optic axes1 & ! /]eoscopic effect is produc$4 ,:5ev] two pictures are se51 no relief is visible2 :5 only "o picture is di/9ctly se51 ! relief mu/ be complete4 ,9 ! prec$+ diagram we h n %ewn ! refraction at ! second surface ( ! l5ses1 nor ! p>allelism ( ! rays :5 !y ent] ! eye1--facts well kn[n 9 elem5t>y optics4 ,,*apt] ,v4 ,,on ,,! ,,!ory ,,( ,,/]eoscopic ,,vision4 ,hav+1 9 ! prec$+ *apt]1 describ$ ! ocul>1 ! reflect+1 & ! l5ticul> /]eoscopes1 & expla9$ ! mann] 9 :i* ! two b9ocul> pictures are comb9$ or laid ^u "o ano!r 9 ! la/ ( ^! in/rum5ts1 we %all n[ proce$ to consid] ! !ory ( /]eoscopic vision4 ,illu/ration3 ,,fig4 #ai4 ,9 ord] to und]/& h[ ! two pictures1 :5 plac$ ! "o above ! o!r1 rise into relief1 we mu/ fir/ expla9 ! mann] 9 :i* a solid object itself is1 9 ord9>y vision1 se5 9 relief1 & we %all !n %ew h[ ?is process takes place 9 ! two =ms ( ! ocul> /]eoscope1 & 9 ! l5ticul> /]eoscope4 ,= ?is purpose1 let ,,abcd1 ,fig4 #ai1 be a section ( ! fru/um ( a cone1 t is1 a cone ) its top cut (f by a plane ,ce,dg1 & hav+ ,,aebg = its base4 ,9 ord] t ! figure may n be complicat$1 x w be suffici5t to consid] h[ we see1 ) two eyes1 ,l & ,r1 ! cone z project$ ^u a plane pass+ ?r\gh its summit ,ce,dg4 ,! po9ts ,l1 ,r be+ ! po9ts ( sight1 draw ! l9es ,,ra1 ,,rb1 :i* w cut ! plane on :i* ! projection is to be made 9 ! po9ts a1 b1 s t ab w repres5t ! l9e ,,ab1 & a circle1 ^: diamet] is ab1 w repres5t ! base ( ! cone1 z se5 by ! "r eye ,r4 ,9 l mann]1 by draw+ ,,la1 ,,lb1 we %all f9d t ,a,b w repres5t ! l9e ,,ab1 & a circle1 ^: diamet] is ,a,b1 ! base ,,aebg1 z se5 by ! left eye4 ,! summit1 ,ce,dg1 ( ! fru/um be+ 9 ! plane ( projection1 w be repres5t$ by ! circle ,ce,dg4 ,! repres5tation ( ! fru/um ,,abcd1 !re=e1 ^u a plane surface1 z se5 by ! left eye ,l1 consi/s ( two circles1 ^: diamet]s are ,,ab1 ,,cd2 &1 z se5 by ! "r eye1 ( o!r two circles1 ^: diamet]s are ab1 ,,cd1 :i*1 9 ,fig4 #bj1 are repres5t$ by ,,ab1 ,,cd1 & ab1 cd4 ,^! plane figures be+ also ! repres5tation ( ! solid on ! ret9a ( ! two eyes1 h[ comes x t we see ! solid & n ! plane pictures8 ,:5 we look at ! po9t ,b1 ,fig4 #ai1 ) bo? eyes1 we conv]ge ^u x ! optic axes ,,lb1 ,,rb1 & we !re=e see ! po9t s+le1 & at ! di/ances ,,lb1 ,,rb f ea* eye4 ,:5 we look at ! po9t ,d1 we )draw ! optic axes f ,b1 & conv]ge !m ^u ,d4 ,we !re=e see ! po9t ,d s+le1 & at ! di/ances ,,ld1 ,,rd f ea* eye2 & 9 l mann] ! eyes run ov] ! :ole solid1 see+ e po9t s+le & di/9ct ^u :i* !y conv]ge _! axes1 & at ! di/ance ( ! po9t ( conv]g5ce f ! obs]v]4 ,dur+ ?is rapid survey ( ! object1 ! :ole ( x is se5 di/9ctly z a solid1 al?\gh e po9t ( x is se5 d\ble & indi/9ct1 except+ ! po9t ^u :i* ! axes are = ! in/ant conv]g$4 ,illu/ration3 ,,fig4 #bj4 ,f ^! obs]vations x is obvi\s1 t :5 we look ) bo? eyes at any solid or body 9 relief1 we see m ( ! "r side ( x by ! "r eye1 & m ( ! left side ( x by ! left eye4 ,! "r side ( ! fru/um ,,abcd1 ,fig4 #ai1 is repres5t$ by ! l9e ,db1 z se5 by ! "r eye1 & by ! %ort] l9e ,,db1 z se5 by ! left eye4 ,9 l mann]1 ! left side ,,ac is repres5t$ by ,,ca1 z se5 by ! left eye1 & by ! %ort] l9e ,ca1 z se5 by ! "r eye4 ,:5 ! body is holl[1 l a w9e glass1 we see m ( ! "r side ) ! left eye1 & m ( ! left side ) ! "r eye4 ,if we n[ sep>ate1 z 9 ,fig4 #bj1 ! two projections %ewn toge!r on ,fig4 #ai1 we %all see t ! two summits1 ,,cd1 cd1 ( ! fru/um are f>!r f "o ano!r ?an ! m di/ant bases1 ,,ab1 ab1 & x is true g5]ally t 9 ! two pictures ( any solid 9 relief1 ! simil> p>ts t are ne> ! obs]v] are m di/ant 9 ! two pictures ?an ! remot] p>ts1 :5 ! plane ( p]spective is beyond ! object4 ,9 ! b9ocul> picture ( ! human face ! di/ance betwe5 ! two noses is great] ?an ! di/ance betwe5 ! two "r or left eyes1 & ! di/ance betwe5 ! two "r or left eyes great] ?an ! di/ance betwe5 ! two remot] e>s4 ,we are n[ 9 a condition to expla9 ! process by :i*1 ) ! eyes alone1 we c see a solid 9 relief by unit+ ! "r & left eye pictures ( x1--or ! !ory ocul> /]eoscope4 ,9 ord] to obta9 ! prop] relief we mu/ place ! "r eye picture on ! left side1 & ! left eye picture on ! "r side1 z %ewn 9 ,fig4 #ba1 by ! pictures ,,abcd1 abcd1 ( ! fru/um ( a cone1 z obta9$ f ,fig4 #ai4 ,illu/ration3 ,,fig4 #ba4 ,9 ord] to unite ^! two dissimil> projections1 we mu/ conv]ge ! optical axes to a po9t ne>] ! obs]v]1 or look at "s po9t ab\t ,m4 ,bo? pictures w imm$iately be d\bl$4 ,an image ( ! figure ab w advance t[>ds ,p1 & an image ( ,,ab w likewise advance t[>ds ,p2 & ! in/ant ^! images are unit$1 ! fru/um ( a cone1 :i* !y repres5t1 w appe> 9 relief at ,,mn1 ! place :]e ! optic axes meet or cross ea* o!r4 ,at fir/ ! solid figure w appe> 9 ! middle1 betwe5 ! two pictures f :i* x is =m$ & ( ! same size1 b aft] "s practice x w appe> small] & ne>] ! eye4 ,its smallness is an optical illusion1 z x has ! same angle ( app>5t magnitude z ! plane figures1 namely1 mn,l ,,abl2 b its position at ,,mn is a reality1 = if we look at ! po9t ( our f+] held beyond ,m ! solid figure w be se5 ne>] ! eye4 ,! difficulty :i* we exp]i5ce 9 see+ x ( ! size & 9 ! position %ewn 9 ,fig4 #ba1 arises f its be+ se5 along ) its two plane repres5tations1 z we %all prove exp]im5tally :5 we treat 9 a future *apt] ( ! union ( simil> figures by ! eye4 ,! two images be+ ?us sup]impos$1 or unit$1 we %all n[ see t ! comb9$ images are se5 9 relief 9 ! v same way t 9 ord9>y vision we saw ! real solid1 ,,abcd1 ,fig4 #ai1 9 relief1 by ! union ( ! two pictures ( x on ! ret9a4 ,f ! po9ts ,a1 ,b1 ,c1 ,d1 a1 b1 c1 d1 draw l9es to ,l & ,r1 ! c5tres ( visible direction ( ea* eye1 & x w be se5 t ! circles ,,ab1 ab1 repres5t+ ! base ( ! cone1 c be unit$ by conv]g+ ! optical axes to po9ts 9 ! l9e mn1 & t ! circles ,,cd1 cd1 :i* are m di/ant1 c be unit$ only by conv]g+ ! optic axes to po9ts 9 ! l9e op4 ,! po9ts ,a1 a1 = example1 unit$ by conv]g+ ! axes to m1 are se5 at t po9t s+le2 ! po9ts ,b1 b at n s+le1 ! po9ts ,c1 c at o s+le1 ! po9ts ,d1 d at p s+le1 ! c5tres ,s1 s ( ! base at ,m s+le1 & ! c5tres ,s1 s ( ! summit plane at ,n s+le4 ,h5ce ! eyes ,l & ,r see ! comb9$ pictures at ,,mn 9 relief1 exactly 9 ! same mann] z !y saw 9 relief ! orig9al solid ,,mn 9 ,fig4 #ai4 ,9 ord] to f9d ! height ,,mn ( ! conical fru/um ?us se51 let ,d di/ance ,,op2 d ,ss1 ! di/ance ( ! two po9ts unit$ at ,m2 d ,ss1 ! di/ance ( ! two po9ts unit$ at ,n2 & ,c ,,lr #b in*es1 ! di/ance ( ! eyes4 ,!n we h-- ,dd ,,mp -------------- ,c d ,dd ,,np -------------- 1 & ,c d ,dd ,dd ,,mn ------------ - -------------- ,c d ,c d ,if ,d #ibd in*es1 ,c #bej1 !n d #bad1 d #bdb1 & ,,mn #jbhc1 ! height ( ! cone4 ,,dc ,:5 ,c d1 ,,mp -------- #b;,c4 ,z ! summit plane op rises above ! base mn by ! successive conv]g5cy ( ! optic axes to diff]5t po9ts 9 ! l9e o,np1 x may be ask$ h[ x happ5s t ! conical fru/um /ill appe>s a solid1 & ! plane op :]e x is1 :5 ! optic axes are conv]g$ to po9ts 9 ! l9e m,mn1 s z to see ! base di/9ctly8 ,! reason ( ?is is t ! rays emanate f op exactly 9 ! same mann]1 & =m exactly ! same image ( x1 on ! two ret9as z if x 7 ! summit ,,cd1 ,fig4 #ai1 ( ! real solid :5 se5 ) bo? eyes4 ,! only effect ( ! advance ( ! po9t ( conv]g5ce f ,n to ,m is to ?r[ ! image ( ,n a little to ! "r side ( ! optic axis ( ! left eye1 & a little to ! left ( ! optic axis ( ! "r eye4 ,! summit plane op w !re=e reta9 its place1 & w be se5 slightly d\bl$ & indi/9ct till ! po9t ( conv]g5ce aga9 returns to x4 ,x has be5 already /at$ t ! two dissimil> pictures may be unit$ by conv]g+ ! optical axes to a po9t beyond !m4 ,9 ord] to d ?is1 ! di/ance ,,ss ( ! pictures1 ,fig4 #ba1 mu/ be greatly less ?an ! di/ance ( ! eyes ,l1 ,r1 9 ord] t ! optic axes1 9 pass+ ?r\gh simil> po9ts ( ! two plane pictures1 may meet at a mod]ate di/ance beyond !m4 ,9 ord] to expla9 h[ ! relief is produc$ 9 ?is case1 let ,,ab1 ,,cd1 ab1 cd1 ,fig4 #bb1 be ! dissimil> pictures ( ! fru/um ( a cone ^: summit is ,,cd1 z se5 by ! "r eye1 & cd z se5 by ! left eye4 ,f ,l & ,r1 z be=e1 draw l9es ?r\gh all ! lead+ po9ts ( ! pictures1 & we %all h ! po9ts ,a1 a unit$ at m1 ! po9ts ,b1 b at n1 ! po9ts ,c1 c at o1 & ! po9ts ,d1 d at p1 ! po9ts ,s1 s at ,m1 & ! po9ts ,s1 s at ,n1 =m+ ! cone mnop1 ) its base mn t[>ds ! obs]v]1 & its summit op m remote4 ,if ! cone _h be5 =m$ ( l9es drawn f ! outl9e ( ! summit to ! outl9e ( ! base1 x w\ld n[ appe> holl[1 ! inside ( x be+ se5 9 place ( ! outside z be=e4 ,if ! pictures ,,ab1 ab are made to *ange places ! comb9$ picture w\ld be 9 relief1 :ile 9 ! case %ewn 9 ,fig4 #ba x w\ld h be5 holl[4 ,h5ce ! "r-eye view ( any solid mu/ be plac$ on ! left h&1 & ! left-eye view ( x on ! "r h&1 :5 we wi% to obta9 x 9 relief by conv]g+ ! optic axes to a po9t betwe5 ! pictures & ! eye1 & vice v]sa :5 we wi% to obta9 x 9 relief by conv]g+ ! optic axes to a po9t beyond ! pictures4 ,9 e case :5 we wi% ! comb9$ pictures to repres5t a holl[1 or ! conv]se ( relief1 _! places mu/ be ex*ang$4 ,illu/ration3 ,,fig4 #bb4 ,9 ord] to f9d ! height ,,mn1 or r ! dep? ( ! cone 9 ,fig4 #bb1 let ,d1 d1 ,c1 c1 repres5t ! same quantities z be=e1 & we %all h ,dd ,,mp -------------- ,c - d ,dd ,,np -------------- 1 & ,c - d ,dd ,dd ,,op -------------- - ------------ ,c - d ,c - d ,:5 ,d1 ,c1 d1 d h ! same values z be=e1 we %all h ,,mn #ahg feet6 ,:5 ,c d1 ,,mp w be inf9ite4 ,we h already expla9$ h[ ! two b9ocul> pictures are comb9$ or laid ^u "o ano!r 9 ! l5ticul> /]eoscope4 ,let u n[ see h[ ! relief is obta9$4 ,! two plane pictures abcd1 ,,abcd1 9 ,fig4 #ah1 are1 z we h already expla9$1 comb9$ or simply laid ^u "o ano!r by ! l5ses ,,ll1 ,l,l1 & 9 ?is /ate are %ewn by ! middle circles at ,aa,bb1 ,cc,dd4 ,! images ( ! bases ,,ab1 ab ( ! cone are accurately unit$ 9 ! d\ble base ,,ab1 ab1 b ! summits ( ! conical fru/um rema9 sep>ate1 z se5 at ,c,d1 cd4 ,x is n[ ! bus9ess ( ! eyes to unite ^!1 or r to make !m appe> z unit$4 ,we h already se5 h[ !y are br\ght into relief :5 ! summits are refract$ s z to pass "o ano!r1 z 9 ,fig4 #ah4 ,let u !re=e take ! case %ewn 9 ,fig4 #bj1 :]e ! summits ,,cd1 cd are m di/ant ?an ! bases ,,ab1 ab4 ,! union ( ^! figures is in/antly effect$1 z %ewn 9 ,fig4 #bc1 by conv]g+ ! optic axes to po9ts m & n successively1 & ?us unit+ ,c & c & ,d & d1 & mak+ ^! po9ts ( ! summit plane appe> at m & n1 ! po9ts ( conv]g5ce ( ! axes ,lm1 ,rm1 & ,ln1 ,rn4 ,9 l mann]1 e pair ( po9ts 9 ! summit plane1 & 9 ! sides ,am1 ,bn ( ! fru/um1 are conv]g$ to po9ts correspond+ to _! di/ance f ! base ,,ab ( ! orig9al solid fru/um1 f :i* ! plane pictures ,,abcd1 abcd1 7 tak54 ,we %all1 !re=e1 see 9 relief ! fru/um ( a cone ^: section is ,amn,b4 ,illu/ration3 ,,fig4 #bc4 ,! !ory ( ! /]eoscope may be express$ & illu/rat$ 9 ! foll[+ mann]1 )\t any ref]5ce to b9ocul> vision3-- #a4 ,:5 a draw+ ( any object or s]ies ( objects is execut$ on a plane surface f "o po9t ( sight1 accord+ to ! pr9ciples ( geometrical p]spective1 e po9t ( its surface t is visible f ! po9t ( sight w be repres5t$ on ! plane4 #b4 ,if ano!r draw+ ( ! same object or s]ies ( objects is simil>ly execut$ on ! same plane f a second po9t ( sight1 suffici5tly di/ant f ! fir/ to make ! two draw+s sep>ate )\t ov]lapp+1 e po9t ( its surface visible f ?is second po9t ( sight w also be repres5t$ on ! plane1 s t we %all h two diff]5t draw+s ( ! object plac$1 at a %ort di/ance f ea* o!r1 on ! same plane4 ,illu/ration3 ,,fig4 #bd4 #c4 ,call+ ^! diff]5t po9ts ( ! object #a1 #b1 #c1 #d1 c41 x w be se5 f ,fig4 #bd1 9 :i* ,l1 ,r are ! two po9ts ( sight1 t ! di/ances #a1 #a1 on ! plane ,,mn1 ( any pair ( po9ts 9 ! two pictures repres5t+ ! po9t #a ( ! object1 w be to ! di/ance ( any o!r pair #b1 #b1 repres5t+ ! po9t #b1 z ! di/ances #a,p1 #b,p ( ! po9ts ( ! object f ! plane ,,mn1 multipli$ inv]sely by ! di/ances ( ^! po9ts f ! po9ts ( sight ,l1 ,r1 or ! middle po9t ,o betwe5 !m4 #d4 ,if ! sculptor1 !re=e1 or ! ar*itect1 or ! me*ani/1 or ! surveyor1 possesses two su* pictures1 ei!r z drawn by a skilful arti/ or tak5 photographically1 he c1 by measur+ ! di/ances ( e pair ( po9ts1 obta9 ! relief or prom95ce ( ! orig9al po9t1 or its di/ance f ! plane ,,mn or ,,ab2 & )\t ! use ( ! /]eoscope1 ! sculptor may model ! object f its plane picture1 & ! di/ances ( e po9t f a giv5 plane4 ,9 l mann]1 ! o!r arti/s may det]m9e di/ances 9 build+s1 9 ma*9]y1 & 9 ! field4 #e4 ,if ! di/ance ( ! po9ts ( sight is equal to ! di/ance ( ! eyes ,l1 ,r1 ! two plane pictures may be unit$ & rais$ into relief by ! /]eoscope1 & ?us give ! sculptor & o!r arti/s an accurate model1 f :i* !y w d]ive additional aid 9 ! execution ( _! "w4 #f4 ,9 /]eoscopic vision1 !re=e1 :5 we jo9 ! po9ts #a1 #a by conv]g+ ! optic axes to #a 9 ! l9e ,,pq1 & ! po9ts #b1 #b by conv]g+ !m to #b 9 ! same l9e1 we place ^! po9ts at ! di/ances ,o#a1 ,,oo#b1 & see ! relief1 or ! v>i\s diff]5ces ( di/ance :i* ! sculptor & o!rs obta9$ by ! me?od :i* we h describ$4 #g4 ,h5ce we inf]1 t if ! /]eoscopic vision ( relief _h nev] be5 ?\ght (1 ! pr9ciples ( ! in/rum5t are involv$ 9 ! geometrical relief :i* is embodi$ 9 ! two pictures ( an object tak5 f two po9ts ( sight1 & 9 ! prom95ce ( e "p ( x obta9$ geometrically4 ,,*apt] ,,vi4 ,,on ,,! ,,union ,,( ,,simil> ,,pictures ,,9 ,,b9ocul> ,,vision4 ,9 unit+ by ! conv]g5cy ( ! optic axes two dissimil> pictures1 z %ewn 9 ,fig4 #ah1 ! solid cone ,,mn ought to appe> at ,,mn mu* ne>] ! obs]v] ?an ! pictures :i* compose x4 ,i f\nd1 h[ev]1 t x nev] took its "r position 9 absolute space1 ! base ,,mn ( ! solid seem+ to re/ on ! same plane ) its con/itu5t pictures ,,ab1 ab1 :e!r x 0 se5 by conv]g+ ! axes z 9 ,fig4 #ah or 9 ,fig4 #bb4 ,^u inquir+ into ! reason ( ?is ,i f\nd t ! di/urb+ cause 0 simply ! simultane\s p]ception ( o!r objects 9 ! same field ( view ^: di/ance 0 kn[n to ! obs]v]4 ,9 ord] to avoid all su* influ5ces ,i made exp]im5ts on l>ge surfaces cov]$ ) simil> plane figures1 su* z fl[]s or geometrical patt]ns ^u pap]-hang+s & c>pets4 ,^! figures be+ always at equal di/ances f ea* o!r1 & almo/ p]fectly equal & simil>1 ! coalesc5ce ( any pair ( !m1 effect$ by direct+ ! optic axes to a po9t betwe5 ! pap]-hang+ & ! eye1 is accompani$ by ! in/antane\s coalesc5ce ( !m all4 ,if we1 !re=e1 look at a pap]$ wall )\t pictures1 or doors1 or w9d[s1 or ev5 at a consid]able portion ( a wall1 at ! di/ance ( ?ree feet1 & unite two ( ! figures1--two fl[]s1 = example1 at ! di/ance ( twelve in*es f ea* o!r horizontally1 ! :ole wall or visible portion ( x w appe> cov]$ ) fl[]s z be=e1 b z ea* fl[] is n[ compos$ ( two fl[]s unit$ at ! po9t ( conv]g5ce ( ! optic axes1 ! :ole pap]$ wall ) all its fl[]s w be se5 susp5d$ 9 ! air at ! di/ance ( six in*es f ! obs]v]6 ,at fir/ ! obs]v] does n decide ^u ! di/ance ( ! susp5d$ wall f himself4 ,x g5]ally advances sl[ly to its new position1 & :5 x has tak5 its place x has a v s+ul> "*4 ,! surface ( x seems slightly curv$4 ,x has a silv]y transp>5t aspect4 ,x is m beautiful ?an ! real pap]1 :i* is no long] se51 & x moves ) ! slighte/ motion ( ! head4 ,if ! obs]v]1 :o is n[ ?ree feet f ! wall1 retires f x1 ! susp5d$ wall ( fl[]s w foll[ him1 mov+ f>!r & f>!r f ! real wall1 & also1 b v slightly1 f>!r & f>!r f ! obs]v]4 ,:5 he /&s /ill1 he may /ret* out 8 h& & place x on ! o!r side ( ! susp5d$ wall1 & ev5 hold a c&le on ! o!r side ( x to satisfy himself t ! gho/ ( ! wall /&s betwe5 ! c&le & himself4 ,9 look+ att5tively at ?is /range picture "s ( ! fl[]s h ! aspect ( real fl[]s4 ,9 "s ! /alk retires f ! plane ( ! picture4 ,9 o!rs x rises f x4 ,"o leaf w come f>!r out ?an ano!r4 ,"o col\r$ portion1 r$1 = example1 w be m prom95t ?an ! blue1 & ! fl[] w ?us appe> ?ick] & m solid1 l a real fl[] compress$1 & deviat+ consid]ably f ! plane repres5tation ( x z se5 by "o eye4 ,all ?is arises f slight & accid5tal diff]5ces ( di/ance 9 simil> or correspond+ p>ts ( ! unit$ figures4 ,if ! di/ance1 = example1 betwe5 two correspond+ leaves is great] ?an ! di/ance betwe5 o!r two correspond+ leaves1 !n ! two fir/ :5 unit$ w appe> ne>] ! eye ?an ! o!r two1 & h5ce ! appe>ance ( a fl[] 9 l[ relief1 is giv5 to ! comb9ation4 ,9 cont9u+ our survey ( ! susp5d$ image ano!r curi\s ph5om5on (t5 pres5ts itself4 ,a "p ( "o1 or ev5 two pieces ( pap]1 & g5]ally ! :ole l5g? ( !m f ! ro( to ! floor1 w retire beh9d ! g5]al plane ( ! image1 z if !re 7 a recess 9 ! wall1 or rise above x z if !re 7 a projection1 ?us display+ on a l>ge scale ! imp]fection 9 ! workman%ip :i* o!rwise x w\ld h be5 difficult to discov]4 ,?is ph5om5on1 or defect 9 ! "w1 arises f ! pap]-hang] hav+ cut (f too mu* ( ! m>g9 ( "o or m ( ! adjac5t /ripes or pieces1 or leav+ too mu* ( x1 s t1 9 ! fir/ case1 :5 ! two halves ( a fl[] are jo9$ toge!r1 "p ( ! middle ( ! fl[] is left out1 & h5ce1 :5 ?is defective fl[] is unit$ b9ocul>ly ) ! "o on ! "r h& ( x1 & ! "o on ! left h& unit$ ) ! defective "o1 ! unit$ or correspond+ portion be+ at a less di/ance1 w appe> f>!r f ! eye ?an ^? p>ts ( ! susp5d$ image :i* are compos$ ( complete fl[]s4 ,! opposite effect w be produc$ :5 ! two portions ( ! fl[]s are n br\ght toge!r1 b sep>at$ by a small space4 ,all ^! ph5om5a may be se51 ?\gh n s conv5i5tly1 ) a c>pet f :i* ! furniture has be5 remov$4 ,we h1 !re=e1 an accurate me?od ( discov]+ defects 9 ! workman%ip ( pap]-hang]s1 c>pet-mak]s1 pa9t]s1 & all arti/s ^: pr(ession x is to comb9e a s]ies ( simil> patt]ns or figures to =m an uni=mly ornam5t$ surface4 ,! smalle/ defect 9 ! simil>ity or equality ( ! figures or l9es :i* compose a patt]n1 & any diff]5ce 9 ! di/ance ( s+le figures is in/antly detect$1 & :at is v rem>kable a small inequality ( di/ance 9 a l9e p]p5dicul> to ! axis ( vision1 or 9 "o dim5sion ( space1 is exhibit$ 9 a magnifi$ =m at a di/ance co9cid5t ) ! axis ( vision1 & 9 an opposite dim5sion ( space4 ,a little practice w enable ! obs]v] to realize & to ma9ta9 ! s+ul> b9ocul> vision :i* replaces ! real picture4#ce ,! occasional ret5tion ( ! picture aft] "o eye is clos$1 & ev5 aft] bo? h be5 clos$ & quickly reop5$1 %ews ! influ5ce ( "t ov] ! evanesc5ce z well z ov] ! creation ( ?is class ( ph5om5a4 ,on "s occasions1 a s+ul> effect is produc$4 ,:5 ! fl[]s or figures on ! pap] are di/ant six in*es1 we may ei!r unite two six in*es di/ant1 or two twelve in*es di/ant1 & s on4 ,9 ! latt] case1 :5 ! eyes h be5 accu/om$ to survey ! susp5d$ picture1 ,i h f\nd t1 aft] %utt+ or op5+ !m1 ,i nei!r saw ! picture =m$ by ! two fl[]s twelve in*es di/ant1 nor ! pap]$ wall itself1 b a picture =m$ by unit+ all ! fl[]s six in*es di/ant6 ,! b9ocul> c5tre 7! po9t to :i* ! optic axes conv]g$1 & consequ5tly ! locality ( ! picture7 _h %ift$ its place1 & in/ead ( advanc+ to ! real wall & see+ x1 x advanc$ exactly z mu* z to unite ! ne>e/ fl[]s1 j z 9 a rat*et :eel1 :5 ! det5t /ops "o too? at a "t2 or1 to speak m correctly1 ! b9ocul> c5tre advanc$ 9 ord] to relieve ! eyes f _! /ra91 & :5 ! eyes 7 op5$1 x _h j rea*$ t po9t :i* correspond$ ) ! union ( ! fl[]s six in*es di/ant4 #ce ,a %eet ( ,que5's heads may be advantage\sly us$ to accu/om ! eyes to ! union ( simil> figures4 ,illu/ration3 ,,fig4 #be4 ,we h already se51 z %ewn 9 ,fig4 #bb1 t :5 we fix ! b9ocul> c5tre1 t is1 conv]ge ! optic axes on a po9t beyond ! dissimil> pictures1 s z to unite !m1 !y rise into relief z p]fectly z :5 ! b9ocul> c5tre1 z %ewn 9 ,fig4 #ah1 is fix$ betwe5 ! pictures us$ & ! eye4 ,9 l mann] we may unite simil> pictures1 b1 ow+ to ! opacity ( ! wall & ! floor1 we _c accompli% ?is ) pap]-hang+s & c>pets4 ,! exp]im5t1 h[ev]1 may be made ) great effect by look+ ?r\gh transp>5t patt]ns cut out ( pap] or metal1 su* z ^? 9 z9c :i* are us$ = l>d]s & o!r purposes4 ,p>ticul> k9ds ( trellis-"w1 & w9d[s ) small squ>es or rhombs ( glass1 may also be us$1 &1 :at is /ill bett]1 a scre5 might be prep>$1 by cutt+ out ! small figures f "o or m pieces ( pap]-hang+s4 ,! readie/ means1 h[ev]1 ( mak+ ! exp]im5t1 is to use ! cane bottom ( a *air1 :i* (t5 exhibits a succession ( octagons ) small lum9\s spaces betwe5 !m4 ,to d ?is1 place ! back ( ! *air ^u a table1 ! height ( ! eye ei!r :5 sitt+ or /&+1 s t ! cane bottom ) its lum9\s patt]n may h a v]tical position1 z %ewn 9 ,fig4 #be1 :]e ,,mn is ! real bottom ( ! *air ) its op5+s1 :i* g5]ally v>y f half an in* to ?ree-f\r?s4 ,suppos+ ! di/ance to be half an in*1 & ! eyes1 ,l1 ,r1 ( ! obs]v] #ab in*es di/ant f ,,mn1 let ,lad1 ,lbe be l9es drawn ?r\gh ! c5tres ( two ( ! op5 spaces a1 b1 & ,rbd1 ,rce l9es drawn ?r\gh ! c5tres ( b & c1 & meet+ ,lad1 ,lbe at d & e1 d be+ ! b9ocul> c5tre to :i* ! optic axes conv]ge :5 we look at x ?r\gh a & b1 & c ! b9ocul> c5tre :5 we look at x ?r\gh b & c4 ,n[1 ! "r eye1 ,r1 sees ! op5+ b at d1 & ! left eye sees ! op5+ a at d1 s t ! image at d ( ! op5+ consi/s ( ! simil> images ( a & b unit$1 & s on ) all ! re/2 s t ! obs]v] at ,l1 ,r no long] sees ! real patt]n ,,mn1 b an image ( x susp5d$ at mn1 ?ree in*es beh9d ,,mn4 ,if ! obs]v] n[ approa*es ,,mn1 ! image mn w approa* to him1 & if he rec$es1 mn w rec$e also1 be+ #a in*es beh9d ,,mn :5 ! obs]v] is six in*es be=e x1 & twelve in*es beh9d ,,mn :5 ! obs]v] is =ty-eight in*es be=e x1 ! image mn mov+ f mn ) a velocity "o-f\r? ( t ) :i* ! obs]v] rec$es4 ,! obs]v] resum+ ! position 9 ! figure :]e 8 eyes1 ,l1 ,r1 are twelve in*es di/ant f ,,mn1 let u consid] ! important results ( ?is exp]im5t4 ,if he n[ grasps ! cane bottom at ,,mn1 8 ?umbs press+ ^u ,,mn1 & 8 f+]s try+ to grasp mn1 he w !n feel :at he does n see1 & see :at he does n feel6 ,! real patt]n is absolutely invisible at ,,mn1 :]e he feels x1 & x /&s fix$ at mn4 ,! f+]s may be pass$ ?r\gh & ?r\gh betwe5 ! real & ! false image1 & beyond x1--n[ se5 on ?is side ( x1 n[ 9 ! middle ( x1 & n[ on ! o!r side ( x4 ,if we next place ! palms ( ea* h& ^u ,,mn1 ! real bottom ( ! *air1 feel+ x all ov]1 ! result w be ! same4 ,no k d]iv$ f t\*--no measurem5t ( real di/ance--no actual demon/ration f previ\s or subsequ5t vision1 t !re is a real solid body at ,,mn1 & no?+ at all at mn1 w remove or %ake ! infallible conviction ( ! s5se ( sight t ! cane bottom is at mn1 & t d,l or d,r is its real di/ance f ! obs]v]4 ,if ! b9ocul> c5tre be n[ drawn back to ,,mn1 ! image se5 at mn w disappe>1 & ! real object be se5 & felt at ,,mn4 ,if ! b9ocul> c5tre be br\ght fur!r back to f1 t is1 if ! optic axes are conv]g$ to a po9t ne>] ! obs]v] ?an ! object1 z illu/rat$ by ,fig4 #ah1 ! cane bottom ,,mn w aga9 disappe>1 & w be se5 at uv1 z previ\sly expla9$4 ,?is me?od ( unit+ small simil> figures is m easily atta9$ ?an t ( do+ x by conv]g+ ! axes to a po9t betwe5 ! eye & ! object4 ,x puts a v little /ra9 ^u ! eyes1 z we _c ?us unite figures ! di/ance ( ^: c5tre is equal to or exce$s #b in*es1 z appe>s f ,fig4 #bb4 ,9 mak+ ^! exp]im5ts1 ! obs]v] _c fail to be /ruck ) ! rem>kable fact1 t ?\gh ! op5+s ,,mn1 mn1 uv1 h all ! same app>5t or angul> magnitude1 t is1 subt5d ! same angle at ! eye1 viz41 d,lc1 d,re1 yet ^? at mn appe> l>g]1 & ^? at uv small]1 ?an ^? at ,,mn4 ,if we cause ! image mn to rec$e & approa* to u1 ! figures 9 mn w inv>iably increase z !y rec$e1 & ^? 9 uv dim9i% z !y approa* ! eye1 & _! visual magnitudes1 z we may call !m1 w dep5d on ! respective di/ances at :i* ! obs]v]1 :e!r "r or wrong 9 8 e/imate1 conceives !m to be plac$1--a result :i* is f9ely illu/rat$ by ! diff]5t size ( ! moon :5 se5 9 ! horizon & 9 ! m]idian4 ,! fact n[ /at$ is a g5]al "o1 :i* ! prec$+ exp]im5ts demon/rate2 & ?\gh our e/imate ( magnitude ?us =m$ is errone\s1 yet x is "o :i* nei!r reason nor exp]i5ce is able to correct4 ,x is a curi\s circum/ance1 t1 previ\s to ! publication ( ^! exp]im5ts1 no examples h be5 record$ ( false e/imates ( ! di/ance ( ne> objects 9 consequ5ce ( ! accid5tal b9ocul> union ( simil> images4 ,9 a room :]e ! pap]-hang+s h a small patt]n1 a %ort-sight$ p]son might v readily turn 8 eyes on ! wall :5 _! axes conv]g$ to "s po9t betwe5 him & ! wall1 :i* w\ld unite "o pair ( ! simil> images1 & 9 ?is case he w\ld see ! wall ne>] him ?an ! real wall1 & mov+ ) ! motion ( 8 head4 ,9 l mann] a long-sight$ p]son1 ) 8 optical axes conv]g$ to a po9t beyond ! wall1 might see an image ( ! wall m di/ant1 & mov+ ) ! motion ( 8 head2 or a p]son :o has tak5 too mu* w9e1 :i* (t5 fixes ! optical axes 9 opposition to ! w1 might1 accord+ to ! nature ( 8 sight1 witness ei!r ( ! illusions above m5tion$4 ,illusions ( bo? ^! k9ds1 h[ev]1 h rec5tly occurr$4 ,a fri5d to :om ,i _h occasion to %ew ! exp]im5ts1 & :o is %ort-sight$1 m5tion$ to me t he _h on two occasions be5 greatly p]plex$ by ! vision ( ^! susp5d$ images4 ,hav+ tak5 too mu* w9e1 he saw ! wall ( a pap]$ room susp5d$ ne> him 9 ! air2 & on ano!r occasion1 :5 kneel+1 & re/+ 8 arms on a cane-bottom$ *air1 he _h fix$ 8 eyes on ! c>pet1 :i* _h accid5tally unit$ ! two images ( ! op5 octagons1 & ?r[n ! image ( ! *air bottom beyond ! plane on :i* he re/$ 8 arms4 ,aft] he>+ my pap] on ?is subject read at ! ,royal ,society ( ,ed9burgh1 ,pr(essor ,*ri/ison communicat$ to me ! foll[+ int]e/+ case1 9 :i* "o ( ! ph5om5a above describ$ 0 se5 by himself3--8,"s ye>s ago10 he obs]ves1 8:5 ,i resid$ 9 a h\se :]e sev]al rooms are pap]$ ) r =mally recurr+ patt]ns1 & "o 9 p>ticul> ) />s only1 ,i us$ occasionally to be mu* plagu$ ) ! wall sudd5ly /&+ out ^u me1 & wav+1 z y describe1 ) ! movem5ts ( ! head4 ,i 0 s5sible t ! cause 0 an error z to ! po9t ( union ( ! visual axes ( ! two eyes2 b ,i rememb] x sometimes co/ me a consid]able ef=t to rectify ! error2 & ,i f\nd t ! be/ way 0 to increase /ill m ! deviation 9 ! fir/ in/ance4 ,z ?is accid5t occurr$ mo/ frequ5tly :ile ,i 0 recov]+ f a sev]e attack ( fev]1 ,i ?\ght my ne>-sight$ eyes 7 ?reat5$ ) "s new mis*ief2 & ?is op9ion 0 ju/ifi$ 9 f9d+ t1 aft] removal to my pres5t h\se1 :]e1 h[ev]1 ! pap]s h no v =mal patt]n1 no su* occurr5ce has ev] tak5 place4 ,! reason is n[ easily und]/ood f y\r rese>*es40#cf ,o!r cases ( an analog\s k9d h be5 communicat$ to me2 & v rec5tly ,m4 ,soret ( ,g5eva1 9 look+ ?r\gh a trellis-"w 9 metal /ret*$ ^u a frame1 saw ! ph5om5on repres5t$ 9 ,fig4 #be1 & has giv5 ! same explanation ( x :i* ,i _h publi%$ long be=e4#cg #cf ,see ,ed94 ,transactions1 #ahdf1 vol4 xv4 p4 #ffc1 & ,phil4 ,mag41 ,may #ahdg1 vol4 xxx4 p4 #cje4 #cg ,bibl4 ,univ]selle1 ,octob] #ahee1 p4 #acf4 ,be=e quitt+ ! subject ( ! b9ocul> union ( simil> pictures1 ,i mu/ give "s acc\nt ( a s]ies ( curi\s ph5om5a :i* ,i obs]v$ by unit+ ! images ( l9es meet+ at an angul> po9t :5 ! eye is plac$ at diff]5t heights above ! plane ( ! pap]1 & at diff]5t di/ances f ! angul> po9t4 ,illu/ration3 ,,fig4 #bf4 ,let ,,ac1 ,,bc1 ,fig4 #bf1 be two l9es meet+ at ,c1 ! plane pass+ ?r\gh !m be+ ! plane ( ! pap]1 & let !m be view$ by ! eyes successively plac$ at ,e1 ,e1 ,e1 & ,e1 at diff]5t heights 9 a plane1 ,,gmn1 p]p5dicul> to ! plane ( ! pap]4 ,let ,r be ! "r eye1 & ,l ! left eye1 & :5 at ,e1 let !m be /ra9$ s z to unite ! po9ts ,a1 ,b4 ,! unit$ image ( ^! po9ts w be se5 at ! b9ocul> c5tre ,d1 & ! unit$ l9es ,,ac1 ,,bc1 w h ! position ,d,c4 ,9 l mann]1 :5 ! eye desc5ds to ,e1 ,e1 ,e1 ! unit$ image ,d,c w rise & dim9i%1 tak+ ! positions ,d,c1 ,d,c1 ,,dc1 till x disappe>s on ! l9e ,,cm1 :5 ! eyes rea* ,m4 ,if ! eye deviates f ! v]tical plane ,,gmn1 ! unit$ image w also deviate f x1 & is always 9 a plane pass+ ?r\gh ! common axis ( ! two eyes & ! l9e ,,gm4 ,if at any altitude ,,em1 ! eye advances t[>ds ,,acb 9 ! l9e ,,eg1 ! b9ocul> c5tre ,d w also advance t[>ds ,,acb 9 ! l9e ,,eg1 & ! image ,,dc w rise1 & become %ort] z its extremity ,d moves along ,,dg1 &1 aft] pass+ ! p]p5dicul> to ,,ge1 x w increase 9 l5g?4 ,if ! eye1 on ! o!r h&1 rec$es f ,,acb 9 ! l9e ,,ge1 ! b9ocul> c5tre ,d w also rec$e1 & ! image ,,dc w desc5d to ! plane ,,cm1 & increase 9 l5g?4 ,illu/ration3 ,,fig4 #bg4 ,! prec$+ diagram is1 = ! purpose ( illu/ration1 drawn 9 a sort ( p]spective1 & !re=e does n give ! true positions & l5g?s ( ! unit$ images4 ,?is defect1 h[ev]1 is rem$i$ 9 ,fig4 #bg1 :]e ,e1 ,e1 ,e1 ,e is ! middle po9t betwe5 ! two eyes1 ! plane ,,gmn be+1 z be=e1 p]p5dicul> to ! plane pass+ ?r\gh ,,acb4 ,n[1 z ! di/ance ( ! eye f ,g is suppos$ to be ! same1 & z ,,ab is inv>iable z well z ! di/ance betwe5 ! eyes1 ! di/ance ( ! b9ocul> c5tres ,,oo1 ,d1 ,d1 ,d1 ,d1 ,p f ,g1 w also be inv>iable1 & lie 9 a circle ,,odp1 ^: c5tre is ,g1 & ^: radius is ,,g1 ! po9t ,o be+ det]m9$ by ! =mula ,,gm ,,ab ,,g ,,gd ------------------ ,,ab ,,rl4 ,h5ce1 9 ord] to f9d ! b9ocul> c5tres ,d1 ,d1 ,d1 ,d1 c41 at any altitude1 ,e1 ,e1 c41 we h only to jo9 ,,eg1 ,e,g1 c41 & ! po9ts ( int]section ,d1 ,d1 c41 w be ! b9ocul> c5tres1 & ! l9es ,,dc1 ,d,c1 c41 drawn to ,c1 w be ! real l5g?s & incl9ations ( ! unit$ images ( ! l9es ,,ac1 ,,bc4 ,:5 ,,g is great] ?an ,,gc !re is obvi\sly "s angle ,a1 or ,e,,gm1 at :i* ,d,c is p]p5dicul> to ,,gc4 ,?is takes place :5 ,,gc ,cos4 ,a --------4 ,,g ,:5 ,o co9cides ) ,c1 ! images ,,cd1 ,,cd1 c41 w h ! same positions & magnitudes z ! *ords ( ! altitudes ,a ( ! eyes above ! plane ,,gc4 ,9 ?is case ! rais$ or unit$ images w j rea* ! p]p5dicul> :5 ! eye is 9 ! plane ,,gcm1 = s9ce ,,gc ,,g1 ,cos4 ,a #a & ,a #j4 ,:5 ! eye at any position1 ,e = example1 sees ! po9ts ,a & ,b unit$ at ,d1 x sees also ! :ole l9es ,,ac1 ,,bc =m+ ! image ,d,c4 ,! b9ocul> c5tre mu/1 !re=e1 run rapidly along ! l9e ,d,c2 t is1 ! incl9ation ( ! optic axes mu/ gradually dim9i% till ! b9ocul> c5tre rea*es ,c1 :5 all /ra9 is remov$4 ,! vision ( ! image ,d,c1 h[ev]1 is c>ri$ on s rapidly t ! b9ocul> c5tre returns to ,d )\t ! eye be+ s5sible ( ! removal & resumption ( ! /ra9 :i* is requir$ 9 ma9ta9+ a view ( ! unit$ image ,d,c4 ,if we n[ suppose ,,ab to dim9i%1 ! b9ocul> c5tre w advance t[>ds ,g1 & ! l5g? & incl9ation ( ! unit$ images ,,dc1 ,d,c1 c41 w dim9i% also1 & vice v]sa4 ,if ! di/ance ,,rl 7,fig4 #bf7 betwe5 ! eyes dim9i%es1 ! b9ocul> c5tre w retire t[>ds ,e1 & ! l5g? & incl9ation ( ! images w increase4 ,h5ce p]sons ) eyes m or less di/ant w see ! unit$ images 9 diff]5t places & ( diff]5t sizes1 ?\gh ! quantities ,a & ,,ab be inv>iable4 ,:ile ! eyes at ,e are runn+ along ! l9es ,,ac1 ,,bc1 let u suppose !m to re/ ^u ! po9ts ab equidi/ant f ,c4 ,jo9 ab1 & f ! po9t g1 :]e ab int]sects ,,gc1 draw ! l9e g,e1 & f9d ! po9t d f ! =mula g,e ab gd -----------------------4 ab ,,rl ,h5ce ! two po9ts a1 b w be unit$ at d1 & :5 ! angle ,e,,gc is su* t ! l9e jo9+ ,d & ,c is p]p5dicul> to ,,gc1 ! l9e jo9+ d,c w also be p]p5dicul> to ,,gc1 ! loci ( ! po9ts ,dd1 c41 w be 9 t p]p5dicul>1 & ! image ,,dc1 se5 by successive movem5ts ( ! b9ocul> c5tre f ,d to ,c1 w be a /raight l9e4 ,9 ! prec$+ obs]vations we h suppos$ t ! b9ocul> c5tre ,d1 c41 is betwe5 ! eye & ! l9es ,,ac1 ,,bc2 b ! po9ts ,a1 ,c1 & all ! o!r po9ts ( ^! l9es1 may be unit$ by fix+ ! b9ocul> c5tre beyond ,,ab4 ,let ! eyes1 = example1 be at ,e2 !n if we unite ,a1 ,b :5 ! eyes conv]ge to a po9t1 1 7n se5 9 ! ,figure7 beyond ,g1 we %all h ,,ge ,,ab ,g --------------2 ,,rl - ,,ab & if we jo9 ! po9t ?us f\nd & ,c1 ! l9e ,c w be ! unit$ image ( ,,ac & ,,bc1 ! b9ocul> c5tre rang+ f to ,c1 9 ord] to see x z "o l9e4 ,9 l mann]1 we may f9d ! position & l5g? ( ! image ,c1 ,c1 & ,c1 correspond+ to ! position ( ! eyes at ,e,e & ,e4 ,h5ce all ! unit$ images ( ,,ac1 ,,bc1 viz41 ,c1 ,c1 c41 w lie bel[ ! plane ( ,,abc1 & ext5d beyond a v]tical l9e ,,ng cont9u$2 & !y w gr[ l>g] & l>g]1 & approximate 9 direction to ,,cg z ! eyes desc5d f ,e to ,m4 ,:5 ! eyes are ne> to ,m1 & a little above ! plane ( ,,abc1 ! l9e1 :5 n c>efully obs]v$1 w h ! appe>ance ( co9cid+ ) ,,cg1 b /ret*+ a great way beyond ,g4 ,?is extreme case repres5ts ! celebrat$ exp]im5t ) ! compasses1 describ$ by ,dr4 ,smi?1 & ref]r$ to by ,pr(essor ,:eat/one4 ,he took a pair ( compasses1 :i* may be repres5t$ by ,,acb1 ,,ab be+ _! po9ts1 ,,ac1 ,,bc _! legs1 & ,c _! jo9t2 & hav+ plac$ 8 eyes ab\t ,e1 above _! plane1 he made ! foll[+ exp]im5t3--8,hav+ op5$ ! po9ts ( a pair ( compasses some:at wid] ?an ! int]val ( y\r eyes1 ) y\r arm ext5d$1 hold ! head or jo9t 9 ! ball ( y\r h&1 ) ! po9ts outw>ds1 & equidi/ant f y\r eyes1 & some:at high] ?an ! jo9t4 ,!n fix+ y\r eyes ^u any remote object ly+ 9 ! plane t bisects ! int]val ( ! po9ts1 y w fir/ p]ceive two pair ( compasses1 7ea* by be+ d\bl$ ) _! inn] legs cross+ ea* o!r1 n unlike ! old %ape ( ! lett] ,w74 ,b by compress+ ! legs ) y\r h& ! two inn] po9ts w come ne>] to ea* o!r2 & :5 !y unite 7hav+ /opp$ ! compression7 ! two inn] legs w also entirely co9cide & bisect ! angle "u ! outw>d ones1 & w appe> m vivid1 ?ick]1 & l>g]1 ?an !y d1 s z to rea* f y\r h& to ! remote/ object 9 view ev5 9 ! horizon itself1 if ! po9ts be exactly co9cid5t40#ch ,ow+ to 8 imp]fect appreh5sion ( ! nature ( ?is ph5om5on1 ,dr4 ,smi? has omitt$ to notice t ! unit$ legs ( ! compasses lie bel[ ! plane ( ,,abc1 & t !y nev] c ext5d fur!r ?an ! b9ocul> c5tre at :i* _! po9ts ,a & ,b are unit$4 ,!re is ano!r v>iation ( ^! exp]im5ts :i* possesses "s int]e/1 9 consequ5ce ( its extreme case hav+ be5 made ! basis ( a new !ory ( visible direction1 by ! late ,dr4 ,wells4#ci ,let u suppose ! eyes ( ! obs]v] to advance f ,e to ,n1 & to desc5d along ! opposite quadrant on ! left h& ( ,,ng1 b n drawn 9 ,fig4 #bg1 !n ! unit$ image ( ,,ac1 ,,bc w gradually desc5d t[>ds ,,cg1 & become l>g] & l>g]4 ,:5 ! eyes are a v little above ! plane ( ,,abc1 & s f> to ! left h& ( ,,ab t ,,ca po9ts ne>ly to ! left eye & ,,cb to ! "r eye1 !n we h ! circum/ances "u :i* ,dr4 ,wells made ! foll[+ exp]im5t3--8,if we hold two ?9 rules 9 su* a mann] t _! %>p edges 7,,ac1 ,,bc 9 ,fig4 #bg7 %all be 9 ! optic axes1 "o 9 ea*1 or r a little bel[ !m1 ! two edges w be se5 unit$ 9 ! common axis1 7,,gc 9 ,fig4 #bg27 & ?is app>5t edge w seem ( ! same l5g? ) t ( ei!r ( ! real edges1 :5 se5 alone by ! eye 9 ! axis ( :i* x is plac$40 ,?is exp]im5t1 x w be se51 is ! same ) t ( ,dr4 ,smi?1 ) ?is diff]5ce only1 t ! po9ts ( ! compasses are direct$ t[>ds ! eyes4 ,l ,dr4 ,smi?1 ,dr4 ,wells has omitt$ to notice t ! unit$ image rises above ,,gh1 & he commits ! opposite error ( ,dr4 ,smi?1 9 mak+ ! l5g? ( ! unit$ image too %ort4 #ch ,smi?'s ,opticks1 vol4 ii4 p4 #chh1 #igg4 #ci ,essay on ,s+le ,vision1 c41 p4 #dd4 ,if 9 ?is =m ( ! exp]im5t we fix ! b9ocul> c5tre beyond ,c1 !n ! unit$ images ( ,,ac1 & ,,bc desc5d bel[ ,,gc1 & v>y 9 _! l5g?1 & 9 _! incl9ation to ,,gc1 accord+ to ! height ( ! eye above ! plane ( ,,abc1 & its di/ance f ,,ab4 ,,*apt] ,,vii4 ,,description ,,( ,,diff]5t ,,/]eoscopes4 ,al?\gh ! l5ticul> /]eoscope has e advantage t su* an in/rum5t c possess1 :e!r x is want$ = exp]im5ts on b9ocul> vision--= assi/+ ! arti/ by ! reproduction ( objects 9 relief1 or = ! purposes ( amusem5t & in/ruction1 yet !re are o!r =ms ( x :i* h p>ticul> prop]ties1 & :i* may be con/ruct$ )\t ! aid ( ! optician1 & ( mat]ials )9 ! rea* ( ! humble/ inquir]s4 ,! fir/ ( ^! is-- #a4 ,! ,tubul> ,reflect+ ,/]eoscope4 ,9 ?is =m ( ! in/rum5t1 %ewn 9 ,fig4 #bh1 ! pictures are se5 by reflexion f two specula or prisms plac$ at an angle ( #ij1 z 9 ,mr4 ,:eat/one's in/rum5t4 ,9 o!r respects ! two in/rum5ts are ess5tially diff]5t4 ,9 ,mr4 ,:eat/one's /]eoscope he employs two mirrors1 ea* f\r in*es squ>e--t is1 he employs ?irty-two squ>e in*es ( reflect+ surface1 & is !re=e "u ! necessity ( employ+ glass mirrors1 & mak+ a clumsy1 unmanageable1 & unsci5tific in/rum5t1 ) all ! imp]fections :i* we h po9t$ out 9 a prec$+ *apt]4 ,x is n easy to und]/& :y mirrors ( su* a size %\ld h be5 adopt$4 ,! reason ( _! be+ made ( common look+-glass is1 t metallic or prismatic reflectors ( su* a size w\ld h be5 extremely exp5sive4 ,illu/ration3 ,,fig4 #bh4 ,x is obvi\s1 h[ev]1 f ! slighte/ consid]ation1 t reflectors ( su* a size are :olly unnecess>y1 & t "o squ>e in* ( reflect+ surface1 9 place ( ?irty-two1 is q suffici5t = unit+ ! b9ocul> pictures4 ,we c1 !re=e1 at a price z l[ z t ( ! #d-;in* glass reflectors1 use mirrors ( speculum metal1 /eel1 or ev5 silv]1 or rectangul> glass prisms1 9 :i* ! images are obta9$ by total reflexion4 ,9 ?is way ! /]eoscope becomes a real optical in/rum5t1 9 :i* ! reflexion is made f surfaces s+le & p]fectly flat1 z 9 ! second reflexion ( ! ,newtonian telescope & ! microscope ( ,amici1 9 :i* pieces ( look+-glass 7 nev] us$4 ,by ?us dim9i%+ ! reflectors1 we obta9 a portable tubul> in/rum5t occupy+ ne>ly z little room z ! l5ticul> /]eoscope1 z w be se5 f ,fig4 #bh1 :]e ,,abcd is a tube ^: diamet] is equal to ! l>ge/ size ( "o ( ! b9ocul> pictures :i* we propose to use1 ! left-eye picture be+ plac$ at ,,cd1 & ! "r-eye "o at ,,ab4 ,if !y are transp>5t1 !y w be illum9at$ ?r\gh pap] or gr\nd glass1 & if opaque1 ?r\gh op5+s 9 ! tube4 ,! image ( ,,ab1 reflect$ to ! left eye ,l f ! small mirror mn1 & t ( ,,cd to ! "r eye ,r f ! mirror op1 w be unit$ exactly z 9 ,mr4 ,:eat/one's in/rum5t already describ$4 ,! di/ance ( ! two ends1 n1 p1 ( ! mirrors %\ld be a little great] ?an ! smalle/ di/ance betwe5 ! two eyes4 ,if we wi% to magnify ! picture1 we may use two l5ses1 or sub/itute = ! reflectors a totally reflect+ glass prism1 9 :i* "o or two ( its surfaces are made convex4#dj #dj ,we may use also ! l5s prism1 :i* ,i propos$ _m ye>s ago 9 ! ,ed9burgh ,philosophical ,j\rnal4 #b4 ,! ,s+le ,reflect+ ,/]eoscope4 ,?is v simple in/rum5t1 :i*1 h[ev]1 answ]s only = symmetrical figures1 su* z ^? %ewn at ,a & ,b1 :i* mu/ be ei!r two "r-eye or two left-eye pictures1 is %ewn 9 ,fig4 #bi4 ,a s+le reflector1 ,,mn1 :i* may be ei!r a piece ( glass1 or a piece ( mirror-glass1 or a small metallic speculum1 or a rectangul> prism1 is plac$ at ,,mn4 ,if we look into x ) ! left eye ,l1 we see1 by reflexion f its surface at ,c1 a rev]t$ image1 or a "r-eye picture ( ! left-eye picture ,b1 :i*1 :5 se5 9 ! direction ,,lca1 & comb9$ ) ! figure ,a1 se5 directly ) ! "r eye ,r1 produces a rais$ cone2 b if we turn ! reflector ,l r\nd1 s t ! "r eye may look into x1 & comb9e a rev]t$ image ( ,a1 ) ! figure ,b se5 directly ) ! left eye ,l1 we %all see a holl[ cone4 ,z ,,bc ,,cl is great] ?an ,,ra1 ! reflect$ image w be slightly less 9 size ?an ! image se5 directly1 b ! diff]5ce is n su* z to produce any p]ceptible effect ^u ! appe>ance ( ! holl[ or ! rais$ cone4 ,by br++ ! picture view$ by reflexion a little ne>] ! reflector ,,mn1 ! two pictures may be made to h ! same app>5t magnitude4 ,illu/ration3 ,,fig4 #bi4 ,if we sub/itute = ! s+le reflector ,,mn1 two reflectors su* z are %ewn at ,m1 ,n1 ,fig4 #cj1 or a prism ,p1 :i* gives two int]nal reflexions1 we %all h a g5]al /]eoscope1 :i* answ]s = l&scapes & portraits4 ,illu/ration3 ,,fig4 #cj4 ,! reflectors ,m1 ,n or ,p may be fitt$ up 9 a conical tube1 :i* has an elliptical section to accommodate two figures at its f>!r end1 ! major axis ( ! ellipse be+ p>allel to ! l9e jo9+ ! two eyes4 #c4 ,! ,d\ble ,reflect+ ,/]eoscope4 ,?is in/rum5t diff]s f ! prec$+ 9 hav+ a s+le reflector1 ,,mn1 ,m,n1 = ea* eye1 z %ewn 9 ,fig4 #ca1 & ! effect ( ?is is to exhibit1 at ! same "t1 ! rais$ & ! holl[ cone4 ,! image ( ,b1 se5 by reflexion f ,,mn at ! po9t ,c1 is comb9$ ) ! picture ( ,a1 se5 directly by ! "r eye ,r1 & =ms a holl[ cone2 :ile ! image ( ,a1 se5 by reflexion f ,m,n at ! po9t ,c1 is comb9$ ) ! picture ( ,b1 se5 directly by ! left eye ,l1 & =ms a rais$ cone4 ,illu/ration3 ,,fig4 #ca4 ,illu/ration3 ,,fig4 #cb4 ,ano!r =m ( ! d\ble reflect+ /]eoscope is %ewn 9 ,fig4 #cb1 :i* diff]s f t %ewn 9 ,fig4 #ca 9 ! position ( ! two reflectors & ( ! figures to be unit$4 ,! reflect+ faces ( ! mirrors are turn$ outw>ds1 _! di/ance be+ less ?an ! di/ance betwe5 ! eyes1 & ! effect ( ?is is to exhibit at ! same "t ! rais$ & ! holl[ cone1 ! holl[ cone be+ n[ on ! "r-h& side4 ,if 9 place ( two "r or two left eye pictures1 z %ewn 9 ,figs4 #bi1 #ca1 & #cb1 we use "o "r eye & "o left eye picture1 & comb9e ! reflect$ image ( ! "o ) ! reflect$ image ( ! o!r1 we %all h a rais$ cone ) ! /]eoscope1 %ewn 9 ,fig4 #ca1 & a holl[ cone ) ! "o 9 ,fig4 #cb4 ,! d\ble reflect+ /]eoscope1 9 bo? its =ms1 is a g5]al in/rum5t = portraits & l&scapes1 & ?us possesses prop]ties peculi> to itself4 ,! reflectors may be glass or metallic specula1 or total reflexion prisms4 #d4 ,! ,total ,reflexion-,/]eoscope4 ,?is =m ( ! /]eoscope is a v int]e/+ "o1 & possesses valuable prop]ties4 ,x requires only a small prism & "o diagram1 or picture ( ! solid1 z se5 by "o eye2 ! o!r diagram1 or picture :i* is to be comb9$ ) x1 be+ creat$ by total reflexion f ! base ( ! prism4 ,?is in/rum5t is %ewn 9 ,fig4 #cc1 :]e ,d is ! picture ( a cone z se5 by ! left eye ,l1 & ,,abc a prism1 ^: base ,,bc is s l>ge1 t :5 ! eye is plac$ close to x1 x may see1 by reflexion1 ! :ole ( ! diagram ,d4 ,! angles ,,abc1 ,,acb mu/ be equal1 b may be ( any magnitude4 ,great accuracy 9 ! equality ( ! angles is n necess>y2 & a prism con/ruct$1 by a lapid>y1 out ( a fragm5t ( ?ick plate-glass1 ! face ,,bc be+ "o ( ! surfaces ( ! plate1 w answ] ! purpose4 ,:5 ! prism is plac$ at a1 ,fig4 #cd1 at "o end ( a conical tube ,,ld1 & ! diagram ,d at ! o!r end1 9 a cap1 :i* c be turn$ r\nd s z to h ! l9e mn1 ,fig4 #cc1 :i* passes ?r\gh ! c5tre ( ! base & summit ( ! cone p>allel to ! l9e jo9+ ! two eyes1 ! in/rum5t is ready = use4 ,! obs]v] places 8 left eye at ,l1 & views ) x ! picture ,d1 z se5 by total reflexion f ! base ,,bc ( ! prism1 ,figs4 #cc & #ce1 :ile ) 8 "r eye ,r1 ,fig4 #cc1 he views ! real picture directly4 ,! fir/ ( ^! pictures be+ ! rev]se ( ! second ,d1 l all pictures =m$ by "o reflexion1 we ?us comb9e two dissimil> pictures into a rais$ cone1 z 9 ! figure1 or into a holl[ "o1 if ! picture at ,d is turn$ r\nd #ahj4 ,if we place ! images ( two diagrams1 "o l "o ( ^? at ,a1 ,fig4 #ca1 & ! o!r l ! "o at ,b1 v]tically above "o ano!r1 we %all !n see1 at ! same "t1 ! rais$ & ! holl[ cone1 z produc$ 9 ! l5ticul> /]eoscope by ! ?ree diagrams1 two l ^? 9 ,fig4 #ca1 & a ?ird l ! "o at ,a4 ,:5 ! prism is good1 ! dissimil> image1 produc$ by ! two refractions at ,b & ,c1 & ! "o reflexion at ,e1 is1 ( c\rse1 m accurate ?an if x _h be5 drawn by ! mo/ skilful arti/2 & !re=e ?is =m ( ! /]eoscope has 9 ?is respect an advantage ov] e o!r 9 :i* two dissimil> figures1 execut$ by art1 are necess>y4 ,9 consequ5ce ( ! l5g? ( ! reflect$ p5cil ,,db ,,be ,,ec ,,cl be+ a little great] ?an ! direct p5cil ( rays ,,dr1 ! two images comb9$ h n exactly ! same app>5t magnitude2 b ! diff]5ce is n p]ceptible to ! eye1 & a rem$y c\ld easily be provid$ 7 x requir$4 ,illu/ration3 ,,fig4 #cc4 ,illu/ration3 ,,fig4 #cd4 ,if ! conical tube ,,ld is held 9 ! left h&1 ! left eye mu/ be us$1 & if 9 ! "r h& ! "r eye mu/ be us$1 s t ! h& may n ob/ruct ! direct vision ( ! draw+ by ! eye :i* does n look ?r\gh ! prism4 ,! cone ,,ld mu/ be turn$ r\nd slightly 9 ! h& till ! l9e mn jo9+ ! c5tre & apex ( ! figure is p>allel to ! l9e jo9+ ! two eyes4 ,! same l9e mu/ be p>allel to ! plane ( reflexion f ! prism2 b ?is p>allelism is secur$ by fix+ ! prism & ! draw+4 ,x is sc>cely necess>y to /ate t ?is /]eoscope is applicable only to ^? diagrams & =ms :]e ! "o image is ! reflect$ picture ( ! o!r4 ,illu/ration3 ,,fig4 #ce4 ,if we wi% to make a microscopic /]eoscope ( ?is =m1 or to magnify ! draw+s1 we h only to cem5t plano-convex l5ses1 ( ! requisite focal l5g?1 ^u ! faces ,,ab1 ,,ac ( ! prism1 or1 :at is simpl] /ill1 to use a section ( a deeply convex l5s ,,abc1 ,fig4 #ce1 & apply ! o!r half ( ! l5s to ! "r eye1 ! face ,,bc hav+ be5 previ\sly gr\nd flat & poli%$ = ! prismatic l5s4 ,by us+ a l5s ( l>g] focus = ! "r eye1 we may correct1 if requir$1 ! imp]fection aris+ f ! diff]5ce ( pa?s 9 ! reflect$ & direct p5cils4 ,?is diff]5ce1 ?\gh trivial1 might be correct$1 if ?\ght necess>y1 by apply+ to ! "r eye ! c5tral portion ( ! same l5s ^: m>g9 is us$ = ! prism4 ,illu/ration3 ,,fig4 #cf4 ,if we take ! draw+ ( a six-sid$ pyramid z se5 by ! "r eye1 z %ewn 9 ,fig4 #cf1 & place x 9 ! total-reflexion /]eoscope at ,d1 ,fig4 #cc1 s t ! l9e ,,mn co9cides ) mn1 & is p>allel to ! l9e jo9+ ! eyes ( ! obs]v]1 we %all p]ceive a p]fect rais$ pyramid ( a giv5 height1 ! reflect$ image ( ,,cd1 ,fig4 #cf1 be+ comb9$ ) ,,af1 se5 directly4 ,if we n[ turn ! figure r\nd #cj1 ,,cd w come into ! position ,,ab1 & unite ) ,,ab1 & we %all /ill p]ceive a rais$ pyramid1 ) less height & less symmetry4 ,if we turn x r\nd #cj m1 ,,cd w be comb9$ ) ,,bc1 & we %all /ill p]ceive a rais$ pyramid ) /ill less height & /ill less symmetry4 ,:5 ! figure is turn$ r\nd o!r #cj1 or #ij degrees f its fir/ position1 ,,cd w co9cide ) ,,cd se5 directly1 & ! comb9$ figures w be p]fectly flat4 ,if we cont9ue ! rotation ?r\gh o!r #cj1 ,,cd w co9cide ) ,,de1 & a slightly holl[1 b n v symmetrical figure1 w be se54 ,a rotation ( o!r #cj w br+ ,,cd into coales5ce ) ,,ef1 & we %all see a /ill m holl[ & m symmetrical pyramid4 ,a fur!r rotation ( o!r #cj1 mak+ #ahj f ! comm5cem5t1 w br+ ,,cd into union ) ,,af2 & we %all h a p]fectly symmetrical holl[ pyramid ( /ill great] dep?1 & ! exact c\nt]p>t ( ! rais$ pyramid :i* 0 se5 be=e ! rotation ( ! figure comm5c$4 ,if ! pyramid _h be5 squ>e1 ! rais$ w\ld h pass$ into ! holl[ pyramid by rotations ( #de ea*4 ,if x _h be5 rectangul>1 ! *ange w\ld h be5 effect$ by rotations ( #ij4 ,if ! space betwe5 ! two circul> sections ( ! cone 9 ,fig4 #ca _h be5 uni=mly %ad$1 or if l9es _h be5 drawn f e degree ( ! "o circle to e correspond+ degree 9 ! o!r1 9 place ( f e #ij? degree1 z 9 ! ,figure1 ! rais$ cone w\ld h gradually dim9i%$ 9 height1 by ! rotation ( ! figure1 till x became flat1 aft] a rotation ( #ij2 & by cont9u+ ! rotation x w\ld h become holl[1 & gradually rea*$ its maximum dep? aft] a revolution ( #ahj4 #e4 ,! ,s+le-,prism ,/]eoscope4 ,al?\gh ! idea ( unit+ ! b9ocul> pictures by a s+le prism appli$ to "o eye1 & refract+ "o ( ! pictures s z to place x ^u ! o!r se5 directly by ! o!r eye1 or by a prism appli$ to ea* eye1 c\ld h>dly h escap$ ! notice ( any p]son /udy+ ! subject1 yet ! exp]im5t 01 s f> z ,i "k1 fir/ made & publi%$ by myself4 ,i f\nd two prisms q unnecess>y1 & !re=e ab&on$ ! use ( !m1 = reasons :i* w be readily appreciat$4 ,?is simple in/rum5t is %ewn 9 ,fig4 #cg1 :]e ,a1 ,b are ! dissimil> pictures1 & ,p a prism ) su* a refract+ angle z is suffici5t to lay ! image ( ,a ^u ,b1 z se5 by ! "r eye4 ,if we place a second prism be=e ! eye ,r1 we require x only to h half ! refract+ angle ( ! prism ,p1 because ea* prism n[ refracts ! picture opposite to x only half way betwe5 ,a & ,b1 :]e !y are unit$4 ,?is1 at fir/ sight1 appe>s to be an advantage1 = z !re mu/ always be a c]ta9 degree ( col\r produc$ by a s+le prism1 ! use ( two prisms1 ) half ! refract+ angle1 might be suppos$ to r$uce ! col\r "o-half4 ,b :ile ! col\r produc$ by ea* prism is ?us r$uc$1 ! col\r ov] ! :ole picture is ! same4 ,ea* lum9\s edge ) two prisms has bo? r$ & blue t9ts1 :]eas ) "o prism ea* lum9\s edge has only "o col\r1 ei!r r$ or blue4 ,if ! picture is v lum9\s ^! col\rs w be se51 b 9 _m ( ! f9e/ opaque pictures x is h>dly visible4 ,9 ord]1 h[ev]1 to dim9i% x1 ! prism %\ld be made ( glass ) ! l[e/ disp]sive p[]1 or ) rock cry/al4 ,a s+le plane surface1 gr\nd & poli%$ by a lapid>y1 ^u ! edge ( a piece ( plate-glass1 a little l>g] ?an ! pupil ( ! eye1 w give a prism suffici5t = e ord9>y purpose4 ,any p]son may make "o 9 a few m9utes = himself1 by plac+ a little bit ( good w9d[ glass ^u ano!r piece incl9$ to x at ! prop] angle1 & ins]t+ 9 ! angle a drop ( fluid4 ,su* a prism w sc>cely produce any p]ceptible col\r4 ,illu/ration3 ,,fig4 #cg4 ,if a s+le-prism reflector is to be made p]fect1 we h only to make x a*romatic1 :i* c\ld be done extempore1 by correct+ ! col\r ( ! fluid prism by ano!r fluid prism ( diff]5t refractive & disp]sive p[]4 ,) a good a*romatic prism ! s+le-prism /]eoscope is a v f9e in/rum5t2 & no advantage ( any value c\ld be ga9$ by us+ two a*romatic prisms4 ,9 ! article on ,new ,/]eoscopes1 publi%$ 9 ! ,transactions ( ! ,royal ,society ( ,arts = #ahdi1 & 9 ! ,philosophical ,magaz9e = #aheb1 ,i h /at$ 9 a note t ,i believ$ t ,mr4 ,:eat/one _h us$ two a*romatic prisms4 ,?is1 h[ev]1 0 a mi/ake1 z already expla9$1#da = su* an in/rum5t 0 nev] made1 & has nev] be5 nam$ 9 any "w previ\s to #ahdi1 :5 x 0 m5tion$ by myself 9 ! note above ref]r$ to4 #da ,see ,*ap4 i4 pp4 #cc-cf4 ,if we make a d\ble prism1 or jo9 two1 z %ewn at ,p1 ,p 9 ,fig4 #ch1 & apply x to two dissimil> figures ,a1 ,b1 "o ( :i* is ! reflect$ image ( ! o!r1 s t ) ! left eye ,l & ! prism ,p we place ! refract$ image ( ,a ^u ,b1 z se5 by ! "r eye ,r1 we %all see a rais$ cone1 & if ) ! prism ,p we place ! image ( ,b ^u ,a we %all see a holl[ cone4 ,if we place ! left eye ,l at ,o1 beh9d ! common base ( ! prism1 we %all see ) "o-half ( ! pupil ! holl[ cone & ) ! o!r half ! rais$ cone4 ,illu/ration3 ,,fig4 #ch4 #f4 ,! ,op]a-,glass ,/]eoscope4 ,z ! eyes !mselves =m a /]eoscope to ^? :o h ! p[] ( quickly conv]g+ _! axes to po9ts ne>] ?an ! object :i* !y contemplate1 x might h be5 expect$ t ! fir/ attempt to make a /]eoscope = ^? :o d n possess su* a p[]1 w\ld h be5 to supply !m ) auxili>y eyeballs capable ( comb9+ b9ocul> pictures ( diff]5t sizes at diff]5t di/ances f ! eye4 ,?is1 h[ev]1 has n be5 ! case1 & ! /]eoscope = ?is purpose1 :i* we are ab\t to describe1 is "o ( ! late/ ( its =ms4 ,illu/ration3 ,,fig4 #ci4 ,illu/ration3 ,,fig4 #dj4 ,9 ,fig4 #ci1 ,,mn is a small inv]t+ telescope1 consi/+ ( two convex l5ses ,m1 ,n1 plac$ at ! sum ( _! focal di/ances1 & ,,op ano!r ( ! same k9d4 ,:5 ! two eyes1 ,r1 ,l1 look ?r\gh ! two telescopes directly at ! dissimil> pictures ,a1 ,b1 !y w see !m ) p]fect di/9ctness2 b1 by ! slighte/ incl9ation ( ! axes ( ! telescopes1 ! two images c be comb9$1 & ! /]eoscopic effect imm$iately produc$4 ,) ! dissimil> pictures 9 ! diagram a holl[ cone is produc$2 b if we look at ,b ) ! telescope ,m,n1 z 9 ,fig4 #dj1 & at ,a ) ,o,p1 a rais$ cone w be se54 ,) ! usual b9ocul> slides conta9+ portraits or l&scapes1 ! pictures are se5 9 relief by comb9+ ! "r-eye "o ) ! left-eye "o4 ,! in/rum5t n[ describ$ is no?+ m ?an a d\ble op]a-glass1 :i* itself =ms a good /]eoscope4 ,ow+1 h[ev]1 to ! use ( a concave eye-glass1 ! field ( view is v small1 & !re=e a convex glass1 :i* gives a l>g] field1 is greatly to be pref]r$4 ,! little telescopes1 ,,mn1 ,,op1 may be made "o & a half or ev5 "o in* long1 & fitt$ up1 ei!r at a fix$ or ) a v>iable incl9ation1 9 a pyramidal box1 l ! l5ticul> /]eoscope1 & made equally portable4 ,"o ( ^! in/rum5ts 0 made = me "s ye>s ago by ,messrs4 ,horne & ,?orn?waite1 & ,i h describ$ x 9 ! ,nor? ,briti% ,review#db z hav+ ! prop]ties ( a ,b9ocul> ,cameoscope1 & ( :at has be5 absurdly call$ a ,pseudoscope1 see+ t e inv]t+ eye-piece & e /]eoscope is entitl$ to ! v same "n4 ,! little telescope may be made ( "o piece ( glass1 convex at ea* end1 or concave at ! eye-end if a small field is n objectionable1--! l5g? ( ! piece ( glass1 9 ! fir/ case1 be+ equal to ! sum1 &1 9 ! second case1 to ! diff]5ce ( ! focal l5g?s ( ! virtual l5ses at ea* end4#dc #db ,= #aheb1 vol4 xvii4 p4 #bjj4 #dc ,^! solid telescopes may be made a*romatic by cem5t+ concave l5ses ( fl9t glass ^u ea* end1 or ( cr[n glass if !y are made ( fl9t glass4 #g4 ,! ,eye-,glass ,/]eoscope4 ,z x is impossible to obta91 by ! ocul> /]eoscope1 pictures 9 relief f ! beautiful b9ocul> slides :i* are made 9 e "p ( ! _w = ! l5ticul> /]eoscope1 x is v desirable to h a portable /]eoscope :i* c be c>ri$ safely 9 our purse1 = ! purpose ( exam9+ /]eoscopically all su* b9ocul> pictures4 ,if plac$ toge!r ) _! plane sides 9 contact1 a plano-convex l5s1 ,,ab1 & a plano-concave "o1 ,,cd1 ( ! same glass & ! same focal l5g?1 w resemble a ?ick wat*-glass1 & on look+ ?r\gh !m1 we %all see objects ( _! natural size & 9 _! prop] place2 b if we slip ! concave l5s1 ,,cd1 to a side1 z %ewn 9 ,fig4 #da1 we m]ely displace ! image ( ! object :i* we view1 & ! displacem5t increases till ! c5tre ( ! concave l5s comes to ! m>g9 ( ! convex "o4 ,we ?us obta9 a v>iable prism1 by means ( :i* we c1 ) ! left eye1 displace "o ( ! b9ocul> pictures1 & lay x ^u ! o!r1 z se5 by ! "r eye4 ,we may use semi-l5ses or qu>t]s ( l5ses1 & we may make !m a*romatic or ne>ly s if we desire x4 ,d\ble convex & d\ble concave l5ses may also be us$1 & ! motion ( ! concave "o regulat$ by a screw4 ,9 "o :i* ,i con/antly use1 ! concave l5s slides 9 a groove ov] a convex qu>t]-l5s4 ,illu/ration3 ,,fig4 #da4 ,by employ+ two ( ^! v>iable prisms1 we h an ,univ]sal ,/]eoscope = unit+ pictures ( v>i\s sizes & at v>i\s di/ances f ea* o!r1 & ! prisms may be plac$ 9 a pyramidal box1 l ! l5ticul> /]eoscope4 #h4 ,! ,read+-,glass ,/]eoscope4 ,if we take a read+-glass ^: diamet] is n less ?an two in*es & ?ree qu>t]s1 & look ?r\gh x ) bo? eyes at a b9ocul> picture 9 :i* ! "r-eye view is on ! left h&1 & ! left-eye view on ! "r h&1 z 9 ! ocul> /]eoscope1 we %all see ea* picture d\bl$1 & ! degree ( sep>ation is proportional to ! di/ance ( ! picture f ! eye4 ,if ! di/ance ( ! b9ocul> pictures f ea* o!r is small1 ! two middle images ( ! f\r w be unit$ :5 _! di/ance f ! l5s is n v mu* great] ?an its focal l5g?4 ,) a read+-glass #d in*es 9 diamet]1 ) a focal l5g? ( two feet1 b9ocul> pictures1 9 :i* ! di/ance ( simil> p>ts is n9e in*es1 are unit$ )\t any ex]tion ( ! eyes at ! di/ance ( eight feet4 ,) ! same read+-glass1 b9ocul> pictures1 at ! usual di/ance ( #b in*es1 w be unit$ at ! di/ance ( #b or ev5 #b feet4 ,if we advance ! read+-glass :5 ! di/ance is #b or #c feet1 ! picture 9 relief w be magnifi$1 b1 ?\gh ! obs]v] may n notice x1 ! sep>at$ images are n[ kept unit$ by a slight conv]g5cy ( ! optic axes4 ,al?\gh ! pictures are plac$ s f> beyond ! ant]ior focus ( ! l5s1 !y are exce$+ly di/9ct4 ,! di/9ctness ( vision is suffici5t1 at lea/ to long-sight$ eyes1 :5 ! pictures are plac$ )9 #af or #ah in*es ( ! obs]v]1 t is1 #f or #h in*es ne>] ! eye ?an ! ant]ior focus ( ! l5s4 ,9 ?is case we c ma9ta9 ! union ( ! pictures only :5 we beg9 to view !m at a di/ance ( #b or #c feet1 & !n gradually advance ! l5s )9 #af or #ah in*es ( ! pictures4 ,at consid]able di/ances1 ! pictures are mo/ magnifi$ by advanc+ ! l5s :ile ! head ( ! obs]v] is /ation>y4 #i4 ,! ,cam]a ,/]eoscope4 ,! object ( ?is in/rum5t is to unite ! transi5t pictures ( gr\ps ( p]sons or l&scapes1 z del9eat$ 9 two dissimil> pictures1 on ! gr\nd-glass ( a b9ocul> cam]a4 ,if we atta* to ! back ( ! cam]a a l5ticul> /]eoscope1 s t ! two pictures on ! gr\nd-glass occupy ! same place z its usual b9ocul> slides1 we %all see ! gr\p ( figures 9 relief "u e *ange ( attitude1 position1 & expression4 ,! two pictures may be =m$ 9 ! air1 or1 m curi\sly /ill1 ^u a wrea? ( smoke4 ,z ! figures are necess>ily inv]t$ 9 ! cam]a1 !y w rema9 inv]t$ by ! l5ticul> & e o!r in/rum5t b ! op]a-glass /]eoscope1 :i* inv]ts ! object4 ,by apply+ x !re=e to ! cam]a1 we obta9 an in/rum5t by :i* ! photographic arti/ c make exp]im5ts1 & try ! effect :i* w be produc$ by 8 pictures be=e he takes !m4 ,he c ?us select ! be/ =ms ( gr\ps ( p]sons & ( l&scapes1 & ?us produce works ( great int]e/ & value4 #aj4 ,! ,*romatic ,/]eoscope4 ,! *romatic /]eoscope is a =m ( ! in/rum5t 9 :i* relief or app>5t solidity is giv5 to a s+le figure ) diff]5t col\rs del9eat$ ^u a plane surface4 ,if we look ) bo? eyes ?r\gh a l5s ,,ll1 ,fig4 #db1 ab\t #b in*es 9 diamet] or upw>ds1 at any object hav+ col\rs ( diff]5t degrees ( refrangibility1 su* z ! col\r$ b\nd>y l9es on a map1 a r$ rose among gre5 leaves & on a blue backgr\nd1 or any sc>let object :atev] ^u a violet gr\nd1 or 9 g5]al any two simple col\rs n ( ! same degree ( refrangibility1 ! diff]5tly col\r$ p>ts ( ! object w appe> at diff]5t di/ances f ! obs]v]4 ,illu/ration3 ,,fig4 #db4 ,let u suppose ! rays to be r$ & violet1 ^? :i* diff] mo/ 9 refrangibility4 ,if ! r$ rays radiate f ! ant]ior focus ,r1 or r$ rays ( ! l5s ,,ll1 !y w em]ge p>allel1 & ent] ! eye at m2 b ! violet rays radiat+ f ! same focus1 be+ m refrangible1 w em]ge 9 a /ate ( conv]g5ce1 z %ewn at mv1 nv1 ! r$ rays be+ mr1 nr4 ,! "p ( ! object1 !re=e1 f :i* ! r$ rays come1 w appe> ne>] to ! obs]v] ?an ! p>ts f :i* ! violet rays come1 & if !re are o!r col\rs or rays ( int]m$iate refrangibilities1 !y w appe> to come f int]m$iate di/ances4 ,if we place a small r$ & violet disc1 l ! smalle/ waf]1 beside "o ano!r1 s t ! l9e jo9+ _! c5tres is p]p5dicul> to ! l9e jo9+ ! eyes1 & suppose t rays f bo? ent] ! eyes ) _! optical axes p>allel1 x is obvi\s t ! di/ance betwe5 ! violet images on ea* ret9a w be less ?an ! di/ance betwe5 ! r$ images1 & consequ5tly ! eyes w require to conv]ge _! axes to a ne>] po9t 9 ord] to unite ! r$ images1 ?an 9 ord] to unite ! violet images4 ,! r$ images w !re=e appe> at ?is ne>] po9t ( conv]g5ce1 j z1 9 ! l5ticul> /]eoscope1 ! m di/ant pair ( po9ts 9 ! dissimil> images appe> :5 unit$ ne>] to ! eye4 ,by ! two eyes alone1 !re=e1 we obta9 a c]ta91 ?\gh a small degree ( relief f col\rs4 ,) ! l5s ,,ll1 h[ev]1 ! effect is greatly increas$1 & we h ! sum ( ! two effects4 ,f ^! obs]vations1 x is manife/ t ! rev]se effect mu/ be produc$ by a concave l5s1 or by ! common /]eoscope1 :5 two col\r$ objects are employ$ or unit$4 ,! blue "p ( ! object w be se5 ne>] ! obs]v]1 & ! r$ "p ( x m remote4 ,x is1 h[ev]1 a curi\s fact1 & "o :i* appe>$ difficult to expla91 t 9 ! /]eoscope ! col\r-relief 0 n br\ght out z might h be5 expect$4 ,sometimes ! r$ 0 ne>e/ ! eye1 & sometimes ! blue1 & sometimes ! object appe>$ )\t any relief4 ,! cause ( ?is is1 t ! col\r-relief giv5 by ! common /]eoscope 0 ! opposite ( t giv5 by ! eye1 & x 0 only ! diff]5ce ( ^! effects t ought to h be5 obs]v$2 & ?\gh ! influ5ce ( ! eyes 0 an inf]ior "o1 x (t5 act$ alone1 & sometimes ceas$ to act at all1 9 virtue ( t prop]ty ( vision by :i* we see only ) "o eye :5 we are look+ ) two4 ,9 ! *romatic /]eoscope1 ,fig4 #db1 ! int]m$iate "p mn ( ! l5s is ( no use1 s t out ( ! m>g9 ( a l5s upw>ds ( #b in*es 9 diamet]1 we may cut a doz5 ( portions capable ( mak+ z _m in/rum5ts4 ,^! portions1 h[ev]1 a little l>g] only ?an ! pupil ( ! eye1 mu/ be plac$ 9 ! same position z 9 ,fig4 #db4 ,all ! effects :i* we h describ$ are greatly increas$ by us+ l5ses ( highly-disp]s+ fl9t glass1 oil ( cassia1 & o!r fluids ( a great disp]sive p[]1 & avoid+ ! use ( comp\nd col\rs 9 ! objects plac$ 9 ! /]eoscope4 ,x is an obvi\s result ( ^! obs]vations1 t 9 pa9t+1 & 9 col\r$ decorations ( all k9ds1 ! r$ or less refrangible col\rs %\ld be giv5 to ! prom95t p>ts ( ! object to be repres5t$1 & ! blue or m refrangible col\rs to ! backgr\nd & ! p>ts ( ! objects t are to retire f ! eye4 #aa4 ,! ,microscope ,/]eoscope4 ,! l5ticul> =m ( ! /]eoscope is admirably fitt$ = its application to small & microscopic objects4 ,! fir/ in/rum5ts ( ?is k9d 7 con/ruct$ by myself ) qu>t]-in* l5ses1 & 7 #c in*es long & only #a & #a deep4#dd ,!y may be c>ri$ 9 ! pocket1 & exhibit all ! prop]ties ( ! in/rum5t to ! greate/ advantage4 ,! mode ( con/ruct+ & us+ ! in/rum5t is precisely ! same z 9 ! common /]eoscope2 b 9 tak+ ! dissimil> pictures1 we mu/ use ei!r a small b9ocul> cam]a1 :i* w give consid]ably magnifi$ repres5tations ( ! objects1 or we mu/ procure !m f ! comp\nd microscope4 ,! pictures may be obta9$ ) a small s+le cam]a1 by fir/ tak+ "o picture1 & !n %ift+ ! object 9 ! focus ( ! l5s1 ?r\gh a space correspond+ ) ! b9ocul> angle4 ,to f9d ?is space1 :i* we may call x1 make d ! di/ance ( ! object f ! l5s1 n ! numb] ( times x is to be magnifi$1 or ! di/ance ( ! image beh9d ! l5s1 & ,d ! di/ance ( ! eyes2 !n we %all h ,d nd 3 d ,d 3 x1 & x ------4 n t is1 ! space is equal to ! di/ance betwe5 ! eyes divid$ by ! magnify+ p[]4 #dd ,phil4 ,mag41 ,jan4 #aheb1 vol4 iii4 p4 #ai4 ,) ! b9ocul> microscope ( ,pr(essor ,riddell1#de & ! same in/rum5t z improv$ by ,m4 ,na*et1 b9ocul> pictures are obta9$ directly by hav+ !m drawn1 z ,pr(essor ,riddell sugge/s1 by ! cam]a lucida1 b x w\ld be pref]able to take !m photographically4 ,portraits = lockets or r+s might be put into a v small /]eoscope1 by fold+ ! "o l5s back ^u ! o!r4 #de ,am]ican ,j\rnal ( ,sci5ce1 #aheb1 vol4 xv4 p4 #fh4 ,,*apt] ,,viii4 ,,me?od ,,( ,,tak+ ,,pictures ,,= ,,! ,,/]eoscope4 ,h[ev] p]fect be ! /]eoscope :i* we employ1 ! effect :i* x produces dep5ds ^u ! accuracy ) :i* ! b9ocul> pictures are prep>$4 ,! pictures requir$ = ! /]eoscope may be arrang$ 9 f\r classes3-- #a4 ,! repres5tations ( geometrical solids z se5 ) two eyes4 #b4 ,portraits1 or gr\ps ( portraits1 tak5 f liv+ p]sons or animals4 #c4 ,l&scapes1 build+s1 & ma*9es or in/rum5ts4 #d4 ,solids ( all k9ds1 ! productions ( nature or ( art4 99_/ ,geometrical ,solids4 ,repres5tations ( geometrical solids1 71 z we h already se51 ! only objects :i* = _m ye>s 7 employ$ 9 ! reflect+ /]eoscope4 ,! figures ?us us$ are s well kn[n t x is unnecess>y to devote mu* space to _! consid]ation4 ,= ord9>y purposes !y may be drawn by ! h&1 & compos$ ( squ>es1 rectangles1 & circles1 repres5t+ quadrangul> pyramids1 truncat$1 or t]m9at+ 9 a po9t1 cones1 pyramids ) polygonal bases1 or m complex =ms 9 :i* rais$ pyramids or cones rise out ( quadrangul> or conical holl[s4 ,all ^! figures may be drawn by ! h&1 & w produce solid =ms suffici5tly /rik+ to illu/rate ! prop]ties ( ! /]eoscope1 ?\gh n accurate repres5tations ( any actual solid se5 by b9ocul> vision4 ,if "o ( ! b9ocul> pictures is n equal to ! o!r 9 its base or summit1 & if ! l9es ( ! "o are made crook$1 x is curi\s to obs]ve h[ ! appe>ance ( ! result+ solid is /ill ma9ta9$ & v>i$4 ,! foll[+ me?od ( draw+ ^u a plane ! dissimil> repres5tations ( solids1 w give results 9 ! /]eoscope t are p]fectly correct3-- ,illu/ration3 ,,fig4 #dc4 ,let ,l1 ,r1 ,fig4 #dc1 be ! left & "r eye1 & ,a ! middle po9t betwe5 !m4 ,let ,,mn be ! plane on :i* an object or solid ^: height is ,,cb is to be drawn4 ,?r\gh ,b draw ,,lb1 meet+ ,,mn 9 c2 !n if ! object is a solid1 ) its apex at ,b1 ,cc w be ! di/ance ( its apex f ! c5tre ,c ( its base1 z se5 by ! left eye4 ,:5 se5 by ! "r eye ,r1 ,cc w be its di/ance1 c ly+ on ! left side ( ,c4 ,h5ce if ! figure is a cone1 ! dissimil> pictures ( x w be two circles1 9 "o ( :i* its apex is plac$ at ! di/ance ,cc f its c5tre1 & 9 ! o!r at ! di/ance ,cc on ! o!r side ( ! c5tre4 ,:5 ^! two plane figures are plac$ 9 ! /]eoscope1 !y w1 :5 comb9$1 repres5t a rais$ cone :5 ! po9ts c1 c are ne>] "o ano!r ?an ! c5tres ( ! circles repres5t+ ! cone's base1 & a holl[ cone :5 ! figures are int]*ang$4 ,if we call ,e ! di/ance betwe5 ! two eyes1 & h ! height ( ! solid1 we %all h ,e ,,ab3h ------ 3 ,cc1 #b h,e #e;h & ,cc --------1 or --------1 #b;,,ab #d;,,ab :i* w give u ! results 9 ! foll[+ table1 ,e be+ #b1 & ,,ac #h in*es3-- ,height ( object4 ,,bc h ,,ab ,,ac - h ,cc ,in*es4 #a #g #j4agi #b #f #j4daff #c #e #j4ge #d #d #a4be #e #c #b4jhc #f #b #c4ge #g #a #h4ge #h #j ,inf9ite4 ,if we n[ conv]ge ! optic axes to a po9t b1 & wi% to asc]ta9 ! value ( ,cc1 :i* w give diff]5t dep?s1 d1 ( ! holl[ solids correspond+ to diff]5t values ( ,cb1 we %all h ,e ,ab3---- d3,cc1 #b d,e & ,cc ---------- ,,ab1 #b :i*1 mak+ ,,ac #h in*es1 z be=e1 w give ! foll[+ results3-- ,dep?4 ,cb d ,ab ,,ac d ,cc ,in*es4 #a #i #j4aci #b #aj #j4be #c #aa #j4cd #d #ab #j4daff #e #ac #j4dh #f #ad #j4ece #g #ae #j4eh #h #af #j4fbe #i #ag #j4ffc #aj #ah #j4fif #aa #ai #j4gbc #ab #bj #j4ge ,! values ( h & d :5 ,cc1 ,cc are kn[n1 w be f\nd f ! =mul #b;,,ab ,cc h ------------------------1 ,e #b;,,ab ,cc & d ------------------------4 ,e4 ,z ,cc is always equal to ,cc 9 ea* pair ( figures or dissimil> pictures1 ! dep? ( ! holl[ cone w always appe> mu* great] ?an ! height ( ! rais$ "o4 ,:5 ,cc ,cc #j4ge1 h3d #c3ab4 ,:5 ,cc ,cc #j4daff1 h3d #b3d1 & :5 ,cc ,cc #j4aci1 h3d #j4h3a4j4 ,:5 ! solids ( :i* we wi% to h b9ocul> pictures are symmetrical1 ! "o picture is ! reflect$ image ( ! o!r1 or its rev]se1 s t :5 we h drawn ! solid z se5 by "o eye1 we may obta9 ! o!r by copy+ its reflect$ image1 or by simply tak+ a copy ( x z se5 ?r\gh ! pap]4 ,:5 ! geometrical solids are n symmetrical1 _! dissimil> pictures mu/ be tak5 photographically f models1 9 ! same mann] z ! dissimil> pictures ( o!r solids4 ,portraits ( ,liv+ ,p]sons or ,animals4 ,al?\gh x is possible = a clev] arti/ to take two portraits1 ! "o z se5 by 8 "r1 & ! o!r z se5 by 8 left eye1 yet1 ow+ to ! impossibility ( fix+ ! sitt]1 x w\ld be a v difficult task4 ,a bu/ or /atue w\ld be m easily tak5 by fix+ two ap]tures #b in*es di/ant1 z ! two po9ts ( sight1 b ev5 9 ?is case ! result w\ld be imp]fect4 ,! photographic cam]a is ! only means by :i* liv+ p]sons & /atues c be repres5t$ by means ( two plane pictures to be comb9$ by ! /]eoscope2 & b = ! art ( photography1 ?is in/rum5t w\ld h _h a v limit$ application4 ,x is g5]ally suppos$ t photographic pictures1 :e!r 9 ,dagu]reotype or ,talbotype1 are accurate repres5tations ( ! human face & =m1 :5 ! sitt] sits /eadily1 & ! arti/ kn[s ! res\rces ( 8 art4 ,quis solem esse falsum dic]e audeat8 says ! photograph]1 9 rapture ) 8 art4 ,solem esse falsum dic]e audeo1 replies ! man ( sci5ce1 9 ref]5ce to ! hide\s repres5tations ( humanity :i* proce$ f ! /udio ( ! photograph]4 ,! sun nev] errs 9 ! "p :i* he has to p]=m4 ,! sitt] may sometimes contribute 8 %>e to ! hide\sness ( 8 portrait by involunt>y n]v\s motion1 b x is ^u ! arti/ or 8 art t ! blame mu/ be laid4 ,if ! s+le portrait ( an individual is a misrepres5tation ( 8 =m & expression1 ! comb9ation ( two su* pictures into a solid mu/ be m hide\s /ill1 n m]ely because ! error 9 =m & expression is reta9$ or d\bl$1 b because ! s\rce ( error 9 ! s+le portrait is incompatible ) ! application ( ! /]eoscopic pr9ciple 9 giv+ relief to ! plane pictures4 ,! art ( /]eoscopic portraiture is 9 its infancy1 & we %all !re=e devote "s space to ! developm5t ( its true pr9ciples & practice4 ,9 treat+ ( ! images ( objects =m$ by l5ses & mirrors ) sph]ical surfaces1 optical writ]s h satisfi$ !mselves by %ew+ t ! images ( /raight l9es s =m$ are conic sections1 elliptical1 p>abolic1 or hyp]bolic4 ,i am n aw>e t any writ] has treat$ ( ! images ( solid bodies1 & ( _! %ape z affect$ by ! size ( ! l5ses or mirrors by :i* !y are =m$1 or has ev5 attempt$ to %ew h[ a p]fect image ( any object c be obta9$4 ,we %all endeav\r to supply ?is defect4 ,9 a previ\s *apt] we h expla9$ ! mann] 9 :i* images are =m$ by a small ap]ture1 ,h1 9 ! side1 ,,mn1 ( a cam]a1 or 9 ! w9d[-%utt] ( a d>k room4 ,! rectangles br1 br1 & br1 are images ( ! object ,,rb1 accord+ z !y are receiv$ at ! same di/ance f ! l5s z ! object1 or at a less or a great] di/ance1 ! size ( ! image be+ to t ( ! object z _! respective di/ances f ! hole ,h4 ,pictures ?us tak5 are accurate repres5tations ( ! object1 :e!r x be l9eal1 sup]ficial1 or solid1 z se5 f or ?r\gh ! hole ,h2 & if we c\ld ?r[ suffici5t light ^u ! object1 or make ! mat]ial :i* receives ! image v s5sitive1 we %\ld require no o!r cam]a = giv+ u photographs ( all sizes4 ,! only s\rce ( error :i* we c conceive1 is t :i* may arise f ! inflexion ( light1 b we believe t x w\ld ex]cise a small influ5ce1 if any1 & x is only by exp]im5t t its effect c be asc]ta9$4 ,illu/ration3 ,,fig4 #dd4 ,! ,rev4 ,mr4 ,eg]ton & ,i h obta9$ photographs ( a bu/1 9 ! c\rse ( t5 m9utes1 ) a v fa9t sun1 & ?r\gh an ap]ture less ?an ! hundr$? ( an in*2 & ,i h no d\bt t :5 *emi/ry has furni%$ u ) a mat]ial m s5sitive to light1 a cam]a )\t l5ses1 & ) only a p9-hole1 w be ! fav\rite in/rum5t ( ! photograph]4 ,at pres5t1 no sitt] c\ld pres]ve 8 composure & expression dur+ ! numb] ( m9utes :i* are requir$ to complete ! picture4 ,b ?\gh we _c use ?is !oretical cam]a1 we may make "s approximation to x4 ,if we make ! hole ,h a qu>t] ( an in*1 ! pictures br1 c41 w be fa9t & indi/9ct2 b by plac+ a ?9 l5s a qu>t] ( an in* 9 diamet] 9 ! hole ,h1 ! di/9ctness ( ! picture w be re/or$1 &1 f ! introduction ( s mu* light1 ! photograph may be complet$ 9 a suffici5tly %ort "t4 ,! l5s %\ld be made ( rock cry/al1 :i* has a small disp]sive p[]1 & ! ratio ( curvature ( its surfaces %\ld be z six to "o1 ! flatte/ side be+ turn$ to ! picture4 ,9 ?is way !re w be v little col\r & sph]ical ab]ration1 & no error produc$ by any /ri or want ( homog5eity 9 ! glass4 ,z ! hole ,h is ne>ly ! same z ! greate/ op5+ ( ! pupil1 ! picture :i* is =m$ by ! enclos$ l5s w be almo/ id5tical ) ! "o we see 9 monocul> vision1 :i* is always ! mo/ p]fect repres5tation ( figures 9 relief4 ,illu/ration3 ,,fig4 #de4 ,) ?is approximately p]fect cam]a1 let u n[ comp>e ! exp5sive & magnific5t in/rum5ts ) :i* ! photograph] practises 8 art4 ,we %all suppose 8 cam]a to h its l5s or l5ses ) an ap]ture ( only ?ree in*es1 z %ewn at ,,lr 9 ,fig4 #de4 ,if we cov] ! :ole l5s1 or r$uce its ap]ture to a qu>t] ( an in*1 z %ewn at a1 we %all h a correct picture ( ! sitt]4 ,let u n[ take o!r f\r pictures ( ! same p]son1 by remov+ ! ap]ture successively to b1 c1 d1 & e3 ,x is obvi\s t ^! pictures w all diff] v p]ceptibly f ea* o!r4 ,9 ! picture obta9$ ?r\gh d1 we %all see p>ts on ! left side ( ! head :i* are n se5 9 ! picture ?r\gh c1 & 9 ! "o ?r\gh c1 p>ts on ! "r side ( ! head n se5 ?r\gh d4 ,9 %ort1 ! pictures obta9$ ?r\gh c & d are accurate dissimil> pictures1 su* z we h 9 b9ocul> vision1 7! di/ance cd be+ #b in*es17 & fitt$ = ! /]eoscope4 ,9 l mann]1 ! pictures ?r\gh b & e w be diff]5t f ! prec$+1 & diff]5t f "o ano!r4 ,9 ! "o ?r\gh b1 we %all see p>ts bel[ ! eyebr[s1 bel[ ! nose1 bel[ ! upp] lip1 & bel[ ! *91 :i* are n visible 9 ! picture ?r\gh e1 nor 9 ^? ?r\gh c & d2 :ile 9 ! picture ?r\gh e1 we %all see p>ts above ! br[1 & above ! upp] lip1 c41 :i* are n se5 9 ! pictures ?r\gh b1 c1 & d4 ,9 :atev] "p ( ! l5s1 ,,lr1 we place ! ap]ture1 we obta9 a picture diff]5t f t ?r\gh any o!r "p1 & !re=e x foll[s1 t ) a l5s ^: ap]ture is ?ree in*es1 ! photographic picture is a comb9ation ( ab\t "o hundr$ & ?irty dissimil> pictures ( ! sitt]1 ! simil> p>ts ( :i* are n co9cid5t2 or to express x 9 ! language ( p]spective1 ! picture is a comb9ation ( ab\t "o hundr$ & ?irty pictures ( ! sitt]1 tak5 f "o hundr$ & ?irty diff]5t po9ts ( sight6 ,if su* is ! picture =m$ by a ?ree-in* l5s1 :at mu/ be ! am\nt ( ! anamorphism1 or di/ortion ( =m1 :i* is produc$ by photographic l5ses ( diamet]s f ?ree to twelve in*es1 actually us$ 9 photography8#df #df ,see my ,treatise on ,optics1 #b;d edit41 *ap4 vii4 p4 #fe4 ,b x is n m]ely by ! size ( ! l5ses t hide\s portraits are produc$4 ,9 cam]as ) two a*romatic l5ses1 ! rays :i* =m ! picture pass ?r\gh a l>ge ?ickness ( glass1 :i* may n be altoge!r homog5e\s1--?r\gh eight surfaces :i* may n be truly sph]ical1 & :i* c]ta9ly scatt] light 9 all directions1--& ?r\gh an optical comb9ation 9 :i* /raight l9es 9 ! object mu/ be conic sections 9 ! picture6 ,photography1 !re=e1 _c ev5 approximate to p]fection till ! arti/ works ) a cam]a furni%$ ) a s+le qu>t] ( an in* l5s ( rock cry/al1 hav+ its radii ( curvature z six to "o1 or :at exp]i5ce may f9d bett]1 ) an a*romatic l5s ( ! same ap]ture4 ,& we may /ate ) equal confid5ce1 t ! photograph] :o has ! sagacity to p]ceive ! defects ( 8 in/rum5ts1 ! hone/y to av[ x1 & ! skill to rem$y !m by ! applications ( mod]n sci5ce1 w take a place z high 9 photographic portraiture z a ,reynolds or a ,lawr5ce 9 ! si/] art4 ,su* be+ ! nature ( s+le portraits1 we may =m "s notion ( ! effect produc$ by comb9+ dissimil> ones 9 ! /]eoscope1 s z to repres5t ! orig9al 9 relief4 ,! s+le pictures !mselves1 includ+ b9ocul> & multocul> repres5tations ( ! individual1 mu/1 :5 comb9$1 exhibit a v imp]fect portrait 9 relief1--s imp]fect1 inde$1 t ! arti/ is oblig$ to take 8 two pictures f po9ts ( sight diff]5t f ! correct po9ts1 9 ord] to produce ! lea/ disagreeable result4 ,?is w appe> aft] we h expla9$ ! correct me?od ( tak+ b9ocul> portraits = ! /]eoscope4 ,no p]son b a pa9t]1 or "o :o has ! eye & ! ta/e ( a pa9t]1 is qualifi$ to be a photograph] ei!r 9 s+le or b9ocul> portraiture4 ,! fir/ /ep 9 tak+ a portrait or copy+ a /atue1 is to asc]ta9 9 :at aspect & at :at di/ance f ! eye x ought to be tak54 ,9 ord] to und]/& ?is subject1 we %all fir/ consid] ! vision1 ) "o eye1 ( objects ( ?ree dim5sions1 :5 ( diff]5t magnitudes & plac$ at diff]5t di/ances4 ,:5 we ?us view a build+1 or a full-l5g? or colossal /atue1 at a %ort di/ance1 a picture ( all its visible p>ts is =m$ on ! ret9a4 ,if we view x at a great] di/ance1 c]ta9 p>ts cease to be se51 & o!r p>ts come into view2 & ?is *ange 9 ! picture w g on1 b w become less & less p]ceptible z we retire f ! orig9al4 ,if we n[ look at ! build+ or /atue f a di/ance ?r\gh a telescope1 s z to pres5t x to u ) ! same di/9ctness1 & ( ! same app>5t magnitude z we saw x at our fir/ position1 ! two pictures w be ess5tially diff]5t2 all ! p>ts :i* ceas$ to be visible z we retir$ w /ill be invisible1 & all ! p>ts :i* 7 n se5 at our fir/ position1 b became visible by retir+1 w be se5 9 ! telescopic picture4 ,h5ce ! p>ts se5 by ! ne> eye1 & n by ! di/ant telescope1 w be ^? t[>ds ! middle ( ! build+ or /atue1 ^: surfaces conv]ge1 z x 71 t[>ds ! eye2 :ile ^? se5 by ! telescope1 & n by ! eye1 w be ! ext]nal p>ts ( ! object1 ^: surfaces conv]ge less1 or approa* to p>allelism4 ,x w dep5d on ! nature ( ! build+ or ! /atue :i* ( ^! pictures gives u ! mo/ fav\rable repres5tation ( x4 ,if we n[ suppose ! build+ or /atue to be r$uc$ 9 ! mo/ p]fect mann]1--to half its size1 = example1--!n x is obvi\s t ^! two p]fectly simil> solids w af=d a diff]5t picture1 :e!r view$ by ! eye or by ! telescope4 ,9 ! r$uc$ copy1 ! inn] surfaces visible 9 ! orig9al w disappe>1 & ! out] surfaces become visible2 &1 z =m]ly1 x w dep5d on ! nature ( ! build+ or ! /atue :e!r ! r$uc$ or ! orig9al copy gives ! be/ picture4 ,if we repeat ! prec$+ exp]im5ts ) two eyes 9 place ( "o1 ! build+ or /atue w h a diff]5t appe>ance2 surfaces & p>ts1 =m]ly invisible1 w become visible1 & ! body w be bett] se5 because we see m ( x2 b !n ! p>ts ?us br\ght into view be+ se51 g5]ally speak+1 ) "o eye1 w h less brightness ?an ! re/ ( ! picture4 ,b ?\gh we see m ( ! body 9 b9ocul> vision1 x is only p>ts ( v]tical surfaces p]p5dicul> to ! l9e jo9+ ! eyes t are ?us br\ght into view1 ! p>ts ( simil> horizontal surfaces rema9+ invisible z ) "o eye4 ,x w\ld require a pair ( eyes plac$ v]tically1 t is1 ) ! l9e jo9+ !m 9 a v]tical direction1 to enable u to see ! horizontal z well z ! v]tical surfaces2 & x w\ld require a pair ( eyes incl9$ at all possible angles1 t is1 a r+ ( eyes #b in*es 9 diamet]1 to enable u to h a p]fectly symmetrical view ( ! /atue4 ,^! obs]vations w enable u to answ] ! "q1 :e!r or n a r$uc$ copy ( a /atue1 ( precisely ! same =m 9 all its p>ts1 w give u1 ei!r by monocul> or b9ocul> vision1 a bett] view ( x z a "w ( art4 ,z x is ! out] p>ts or surfaces ( a l>ge /atue t are invisible1 its great outl9e & l>ge/ p>ts mu/ be be/ se5 9 ! r$uc$ copy2 & consequ5tly its relief1 or ?ird dim5sion 9 space1 mu/ be mu* great] 9 ! r$uc$ copy4 ,?is w be bett] und]/ood if we suppose a sph]e to be sub/itut$ = ! /atue4 ,if ! sph]e exce$s 9 diamet] ! di/ance betwe5 ! pupils ( ! "r & left eye1 or #b in*es1 we %all n see a complete hemisph]e1 unless f an inf9ite di/ance4 ,if ! sph]e is v mu* l>g]1 we %all see only a segm5t1 ^: relief1 9 place ( be+ equal to ! radius ( ! sph]e1 is equal only to ! v]s$ s9e ( half ! visible segm5t4 ,h5ce x is obvi\s t a r$uc$ copy ( a /atue is n only bett] se5 f m ( its p>ts be+ visible1 b is also se5 9 /rong] relief4 ,on ! ,prop] ,position ( ! ,sitt]4 ,) ^! obs]vations we are n[ prep>$ to expla9 ! prop] me?od ( tak+ b9ocul> portraits = ! /]eoscope4 ,! fir/ & mo/ important /ep is to fix ^u ! position ( ! sitt]1--to select ! be/ aspect ( ! face1 &1 :at is ( m importance ?an is g5]ally suppos$1 to det]m9e ! be/ di/ance f ! cam]a at :i* he %\ld be plac$4 ,at a %ort di/ance c]ta9 p>ts ( "o face & figure :i* %\ld be se5 are conceal$1 & c]ta9 p>ts ( o!r faces are conceal$ :i* %\ld be se54 ,prom95t e>s may be ei!r hid or made less prom95t by dim9i%+ ! di/ance1 & if ! sight ( bo? e>s is desirable ! di/ance %\ld be increas$4 ,prom95t features become less prom95t by di/ance1 & _! influ5ce 9 ! picture is also dim9i%$ by ! increas$ vision :i* di/ance gives ( ! r\nd ( ! head4 ,! outl9e ( ! face & head v>ies ess5tially ) ! di/ance1 & h5ce x is ( great importance to *oose ! be/4 ,a long & n>r[ face requires to be view$ at a diff]5t di/ance f "o t is %ort & r\nd4 ,articles ( dress ev5 may h a bett] or a worse appe>ance accord+ to ! di/ance at :i* we see !m4 ,let u n[ suppose ! prop] di/ance to be six feet1 & s9ce x is impossible to give any rules = tak+ b9ocul> portraits ) l>ge l5ses we mu/ assume a /&>d cam]a ) a l5s a qu>t] ( an in* 9 diamet]1 z ! only "o :i* c give a correct picture z se5 ) "o eye4 ,if ! portrait is want$ = a r+1 a locket1 or a b9ocul> slide1 its size is det]m9$ by its purpose1 & ! photograph] mu/ h a cam]a 7:i* he has n7 to produce ^! diff]5t pictures4 ,8 own cam]a w1 no d\bt1 take a picture = a r+1 a locket1 or a b9ocul> slide1 b he does ?is by plac+ ! sitt] at diff]5t di/ances1--at a v great di/ance = ! r+ picture1 at a consid]able di/ance = ! locket picture1 & at a %ort] di/ance = ! b9ocul> "o2 b none ( ^! di/ances are ! di/ance :i* has be5 select$ z ! prop] "o4 ,) a s+le l5s cam]a1 h[ev]1 he requires only sev]al qu>t]-in* l5ses ( diff]5t focal l5g?s to obta9 ! portrait ( ! sitt] :5 plac$ at ! prop] di/ance f ! cam]a4 ,9 ord] to take b9ocul> portraits = ! /]eoscope a b9ocul> cam]a is requir$1 hav+ its l5ses ( su* a focal l5g? z to produce two equal pictures ( ! same object & ( ! prop] size4 ,^? 9 g5]al use = ! l5ticul> /]eoscope v>y f #b4a in*es to #b4c 9 bread?1 & f #b4e in*es to #b4h 9 height1 ! di/ance betwe5 simil> po9ts 9 ! two pictures v>y+ f #b4cj in*es to #b4eg1 accord+ to ! diff]5t di/ances ( ! =egr\nd & ! remote/ object 9 ! picture4 ,hav+ fix$ ^u ! prop] di/ance ( ! sitt]1 :i* we %all suppose to be six feet1--a di/ance v suitable = exam9+ a bu/ or a picture1 we h n[ to take two portraits ( him1 :i*1 :5 plac$ 9 ! /]eoscope1 %all h ! same relief & ! same appe>ance z ! sitt] :5 view$ f ! di/ance ( six feet4 ,?is w be be/ done by a b9ocul> cam]a1 :i* we %all n[ describe4 ,! ,b9ocul> ,cam]a4 ,?is in/rum5t diff]s f ! common cam]a 9 hav+ two l5ses ) ! same ap]ture & focal l5g?1 = tak+ at ! same in/ant ! picture ( ! sitt] z se5 at ! di/ance ( six feet1 or any o!r di/ance4 ,z x is impossible to gr9d & poli% two l5ses1 :e!r s+le or a*romatic1 ( exactly ! same focal l5g?1 ev5 :5 we h ! same glass = bo?1 we mu/ bisect a good l5s1 & use ! two semi-l5ses1 gr\nd into a circul> =m1 9 ord] to obta9 pictures ( exactly ! same size & def9ition4 ,^! l5ses %\ld be plac$ ) _! diamet]s ( bisection p>allel to "o ano!r1 & p]p5dicul> to ! horizon1 at ! di/ance ( #b in*es1 z %ewn 9 ,fig4 #de1 :]e ,,mn is ! cam]a1 ,l1 ,l ! two l5ses1 plac$ 9 two %ort tubes1 s t by ! usual me*anical means !y c be direct$ to ! sitt]1 or h _! axes conv]g$ ^u him1 z %ewn 9 ! ,figure1 :]e ,,ab is ! sitt]1 ab 8 image z giv5 by ! l5s ,l1 & ab z giv5 by ! l5s ,l4 ,^! pictures are obvi\sly ! v same t w\ld be se5 by ! arti/ ) 8 two eyes at ,l & ,l1 & z ,,alb a,lb a,lb1 ! pictures w h ! same app>5t magnitude z ! orig9al1 & w 9 no respect diff] f x z se5 by ea* eye f ,e1 ,e1 ,ea be+ equal to a,l1 & ,ea to a,l4 ,illu/ration3 ,,fig4 #df4 ,s9ce ! publication 9 #ahdi ( my description ( ! b9ocul> cam]a1 a simil> in/rum5t 0 propos$ 9 ,p>is by a photograph]1 ,m4 ,qu9et1 :o gave x ! "n ( ,qu9etoscope1 :i*1 z ! ,abb ,moigno obs]ves1 means an in/rum5t = see+ ,m4 ,qu9et6 ,i h n se5 ?is cam]a1 b1 f ! foll[+ notice ( x by ! ,abb ,moigno1 x does n appe> to be diff]5t f m9e3--8,n\s avons t la fois surpris et trs-satisfait de retr\v] dans le ,qu9etoscope la *ambre b9oculaire de notre ami ,sir ,david ,brew/]1 telle que n\s l'avons dcrite aprs lui il y a dix-huit mois dans notre bro*ure intitule ,/roscope40 ,cont9u+ to speak ( ,m4 ,qu9et's cam]a1 ! ,abb is l$ to criticise unju/ly :at he calls ! limitation ( ! in/rum5t3--8,en un mot1 ce *>mant app>eil e/ aussi bi5 con/ruit qu'il peut tre1 et n\s dsirons ardemm5t qu'il se rp& assez p\r rcomp5s] ,m4 ,qu9et de son habilet et de ses pe9es4 ,employ dans les limites fixes l'avance p> son vritable inv5teur1 ,sir ,david ,brew/]2 c'e/--dire1 employ reproduire des objets de petite et moy5ne gr&eur1 il donn]a assez beaux rsultats4 ,il ne p\rra pas s]vir1 evidemm5t1 il ne donn]a pas bi5 l'effet /roscopique v\lu1 qu& on v\dra l'appliqu] de trs-gr&s objets1 on a des vues ou pay sages pris d'une trs-gr&e di/ance2 mais il e/ de la nature des uvres huma9es d'tre ess5tiellem5t bornes40#dg ,?is criticism on ! limitation ( ! cam]a is :olly incorrect2 & x w be made app>5t1 9 a future "p ( ! ,*apt]1 t = objects ( all sizes & at all di/ances ! b9ocul> cam]a gives ! v repres5tations :i* we see1 & t o!r me?ods1 ref]r$ to z sup]ior1 give unreal & untru?ful pictures1 = ! purpose ( produc+ a />tl+ relief4 ,9 /at+1 z he subsequ5tly does1 t ! angles at :i* ! pictures %\ld be tak5 8are too vaguely indicat$ by !ory10#dh ! ,abb _c h appeal$ to 8 own optical k1 b mu/ h tru/$ to ! practice ( ,mr4 ,claudet1 :o ass]ts 8t !re _c be any rule = fix+ ! b9ocul> angle ( cam]a obscuras4 ,x is a matt] ( ta/e & arti/ic illusion40#di ,no "q ( sci5ce c be a matt] ( ta/e1 & no illusion c be arti/ic :i* is a misrepres5tation ( nature4 #dg ,see ,cosmos1 vol4 ii4 pp4 #fbb1 #fbd4 #dh ,id4 vol4 vii4 p4 #did4 #di ,id4 vol4 iii4 p4 #feh4 ,:5 ! arti/ has n a b9ocul> cam]a he mu/ place 8 s+le cam]a successively 9 su* positions t ! axis ( 8 l5s may h ! directions ,,el1 ,,el mak+ an angle equal to ,,lcl1 ! angle :i* ! di/ance betwe5 ! eyes subt5ds at ! di/ance ( ! sitt] f ! l5ses4 ,?is angle is f\nd by ! foll[+ =mula3-- d #a4be ,tang4 ,a -------- -------- ,d ,d d be+ ! di/ance betwe5 ! eyes1 ,d ! di/ance ( ! sitt]1 & ,a ! angle :i* ! di/ance betwe5 ! eyes1 #b4e1 subt5ds at ! di/ance ( ! sitt]4 ,^! angles = diff]5t di/ances are giv5 9 ! foll[+ table3-- ,d ,di/ance ,a ,angle =m$ ( ,cam]a by ! two f ! directions ,sitt]4 ( ! ,cam]a4 #e in*es1 #bh #f #f1 #bc #cb #g1 #bj #ad #h1 #ag #df #i1 #ae #dh #aj1 #ad #ae #aa1 #ac #j #ab1 #a foot1 #aa #ed #ac1 #aa #j #ad1 #aj #ag #ae1 #i #cb #af1 #h #ef #ag1 #h #bd #ah1 #g #ef #ai1 #g #ca #bj1 #g #aj #bd1 #b feet1 #e #eh #cj1 #d #df #cf in*es1 #c feet1 #c #ei #db1 #c #be #dh1 #d feet1 #b #ei #ed1 #b #ci #fj1 #e feet1 #b #bc #gb1 #f feet1 #a #ei #hd1 #g feet1 #a #db #if1 #h feet1 #a #cj #ajh1 #i feet1 #a #bj #abj1 #aj feet1 #a #ab ,! numb]s giv5 9 ! great] "p ( ! prec$+ table c be ( use only :5 we wi% to take b9ocul> pictures ( small objects plac$ at %ort di/ances f cam]as ( a dim9utive size4 ,9 photographic portraiture !y are ( no use4 ,! correct angle = a di/ance ( six feet mu/ n exce$ two degrees1--= a di/ance ( eight feet1 "o & a half degrees1 & = a di/ance ( t5 feet1 "o & a fif? degree4 ,mr4 ,:eat/one has giv5 q a diff]5t rule4 ,he makes ! angle to dep5d1 n on ! di/ance ( ! sitt] f ! cam]a1 b on ! di/ance ( ! b9ocul> picture 9 ! /]eoscope f ! eyes ( ! obs]v]6 ,accord+ to ! rule :i* ,i h demon/rat$1 ! angle ( conv]g5cy = a di/ance ( six feet mu/ be #a #ei1 :]eas 9 a /]eoscope ( any k9d1 ) ! pictures six in*es f ! eyes1 ,mr4 ,:eat/one makes x #bc #cb6 ,z su* a diff]5ce is a sc&al to sci5ce1 we mu/ endeav\r to place ! subject 9 its true light1 & x w be int]e/+ to obs]ve h[ ! problem has be5 dealt ) by ! pr(essional photograph]4 ,! foll[+ is ,mr4 ,:eat/one's explanation ( 8 own rule1 or r 8 mode ( /at+ x3-- 8,) respect10 says he1 8to ! means ( prep>+ ! b9ocul> photographs1 7& 9 ?is t]m ,i include bo? ,talbotypes & ,dagu]reotypes17 little requires to be said beyond a few directions z to ! prop] positions 9 :i* x is necess>y to place ! cam]a 9 ord] to obta9 ! two requir$ projections4 8,we w suppose t ! b9ocul> pictures are requir$ to be se5 9 ! /]eoscope at a di/ance ( eight in*es be=e ! eyes1 9 :i* case ! conv]g5ce ( ! optic axes is ab\t #ah4 ,to obta9 ! prop] projections = ?is di/ance1 ! cam]a mu/ be plac$ ) its l5s accurately direct$ t[>ds ! object successively 9 two po9ts ( ! circumf]5ce ( a circle1 ( :i* ! object is ! c5tre1 & ! po9ts at :i* ! cam]a is s plac$ mu/ h ! angul> di/ance ( #ah f ea* o!r1 exactly t ( ! optic axes 9 ! /]eoscope4 ,! di/ance ( ! cam]a f ! object may be tak5 arbitr>ily1 = s long z ! same angle is employ$1 :atev] t di/ance may be1 ! picture w exhibit 9 ! /]eoscope ! same relief1 & be se5 at ! same di/ance ( eight in*es1 only ! magnitude ( ! picture w appe> diff]5t4 ,m9iature /]eoscopic repres5tations ( build+s & full-siz$ /atues are1 !re=e1 obta9$ m]ely by tak+ ! two projections ( ! object f a consid]able di/ance1 b at ! same "t z if ! object 7 only eight in*es di/ant1 t is1 at an angle ( #ah40ej #ej ,phil4 ,trans41 #aheb1 p4 #g4 ,su* is ,mr4 ,:eat/one's rule1 = :i* he has assign$ no reason :atev]4 ,9 describ+ ! b9ocul> cam]a1 9 :i* ! l5ses mu/ be only #b in*es di/ant = portraits1 ,i h %ewn t ! pictures :i* x gives are p]fect repres5tations ( ! orig9al1 & !re=e pictures tak5 ) l5ses or cam]as at any o!r di/ance1 mu/ be diff]5t f ^? :i* are se5 by ! arti/ look+ at ! sitt] f 8 cam]a4 ,!y are1 d\btless1 bo? pictures ( ! sitt]1 b ! picture tak5 by ,mr4 ,:eat/one's rule is "o :i* no man ev] saw or c see1 until he c place 8 eyes at ! di/ance ( tw5ty in*es6 ,x is1 9 %ort1 ! picture ( a liv+ doll1 9 :i* p>ts are se5 :i* are nev] se5 9 society1 & p>ts hid :i* are always se54 ,9 ord] to ?r[ "s light ^u 8 views1 ,mr4 ,:eat/one got 8a numb] ( ,dagu]reotypes ( ! same bu/ tak5 at a v>iety ( diff]5t angles1 s t he 0 enabl$ to place 9 ! /]eoscope two pictures tak5 at any angul> di/ance f #b to #ah1 ! =m] correspond+ to a di/ance ( ab\t six feet1 & ! latt] to a di/ance ( ab\t eight in*es40 ,9 ^? tak5 at #b1 7! prop] angle17 !re is 8an undue elongation ( l9es jo9+ two unequally di/ant po9ts1 s t all ! features ( a bu/ appe> to be exagg]at$ 9 dep?20 :ile 9 ^? tak5 at #ah1 8!re is an undue %ort5+ ( ! same l9es1 s t ! appe>ance ( a bas-relief is obta9$ f ! two projections ( ! bu/1 ! app>5t dim5sions 9 bread? & height rema9+ 9 bo? cases ! same40 ,al?\gh ,mr4 ,:eat/one speaks ?us decid$ly ( ! relative effect produc$ by comb9+ pictures tak5 at #b & #ah1 yet 9 ! v next p>agraph he makes /atem5ts entirely incompatible ) 8 previ\s obs]vations4 8,:5 ! optic axes10 he says1 8are p>allel1 9 /rictness !re %\ld be no diff]5ce betwe5 ! pictures pres5t$ to ea* eye1 & 9 ?is case !re w\ld be no b9ocul> relief1 b ,i f9d t an excell5t effect is produc$ :5 ! axes are ne>ly p>allel1 by pictures tak5 at an incl9ation ( #g or #h1 & ev5 a diff]5ce ( #af or #ag has no decid$ly bad effect60 ,t ,mr4 ,:eat/one obs]v$ all ^! contradictory facts we d n d\bt1 b :y he obs]v$ !m1 & :at 0 _! cause1 is a "q ( sci5tific z well z ( practical importance4 ,mr4 ,:eat/one 0 n aw>e#ea t ! ,dagu]reotype pictures :i* he 0 comb9+1 tak5 ) l>ge l5ses1 7 n pictures z se5 ) two human eyes1 b 7 actually b9ocul> & multocul> mon/rosities1 entirely unfit = ! exp]im5ts he 0 c>ry+ on1 & !re=e incapable ( te/+ ! only true me?od ( tak+ b9ocul> pictures :i* we h already expla9$4 #ea ,mr4 ,:eat/one's pap] 0 publi%$ be=e ,i _h po9t$ out ! de=mities produc$ by l>ge l5ses4 ,see p4 #acj4 ,_h ,mr4 ,:eat/one comb9$ pictures1 ea* ( :i* 0 a correct monocul> picture1 z se5 ) ea* eye1 & z tak5 ) a small ap]ture or a small l5s1 he w\ld h f\nd no discrepancy betwe5 ! results ( obs]vation & ( sci5ce4 ,f ! same cause1 we presume1 namely1 ! use ( multocul> pictures1 ,mr4 ,alfr$ ,smee#eb has be5 l$ to a s+ul> me?od ( tak+ b9ocul> ones4 ,9 "o place he implicitly adopts ,mr4 ,:eat/one's errone\s rule4 8,! pictures = ! /]eoscope10 he says1 8are tak5 at two /ations1 at a great] or less di/ance ap>t1 accord+ to ! di/ance at :i* !y are to be view$4 ,= a di/ance ( #h in*es ! two pictures are tak5 at angles ( #ah1 = #ac in*es #aj1 = #ah in*es #h1 & = #d feet #d40 ,b :5 he comes to describe 8 own me?od he seems to "k & to foll[ ! true me?od1 if we rightly und]/& 8 mean+4 8,to obta9 a b9ocul> picture ( anybody10 he says1 8! cam]a mu/ be employ$ to take half ! impression1 & !n x mu/ be mov$ 9 ! arc ( a circle ( :i* ! di/ance f ! cam]a to ! po9t ( sight#ec is ! radius = ab\t #b in*es :5 a second picture is tak51 & ! two impressions conjo9tly =m "o b9ocul> picture4 ,!re are _m ways by :i* ?is result may be obta9$4 ,a spot may be plac$ on ! gr\nd-glass on :i* ! po9t ( sight %\ld be made exactly to fall4 ,! cam]a may !n be mov$ #b in*es1 & adju/$ till ! po9t ( sight falls aga9 ^u ! same spot on ! gr\nd-glass1 :51 if ! cam]a has be5 mov$ 9 a true horizontal plane ! effect ( ! d\ble picture w be p]fect40 ,?is is precisely ! true me?od ( tak+ b9ocul> pictures :i* we _h giv5 long be=e1 b x is true only :5 small l5ses are us$4 ,9 ord] to obta9 ?is motion 9 ! true arc ( a circle ! cam]a 0 mov$ on two cones :i* conv]g$ to ! po9t ( sight1 & ,mr4 ,smee ?us obta9$ pictures ( ! usual "*4 ,b 9 mak+ ^! exp]im5ts he 0 l$ to take pictures :5 ! cam]a 0 9 cont9ual motion backw>ds & =w>ds = #b in*es1 & he rem>ks t 89 ?is case ! picture 0 ev5 m beautiful ?an :5 ! two images 7 sup]impos$60 8,?is exp]im5t10 he adds1 8is v rem>kable1 = :o w\ld h ?\ght =m]ly t a picture c\ld possibly h be5 made ) a cam]a 9 cont9ual motion8 ,nev]!less we accompli% x e day ) ease1 & ! "* ( ! lik5ess is wond]fully improv$ by x40 ,we h n[ left ! regions ( sci5ce1 & h to adjudicate on a matt] ( op9ion & ta/e4 ,mr4 ,smee has be5 s k9d z to s5d me a picture ?us tak54 ,x is a good photograph ) features enl>g$ 9 all azimu?s1 b x has no o!r relief ?an t :i* we h describ$ z monocul>4 #eb ,! ,eye 9 ,heal? & ,disease1 by ,alfr$ ,smee1 #b;d edit4 #ahed1 pp4 #he-ie4 #ec ,?is expression has a diff]5t mean+ 9 p]spective4 ,we und]/& x to mean "h ! po9t ( ! sitt] or object1 :i* is to be ! c5tre ( ! picture4 ,a s+ul> effect ( comb9+ pictures tak5 at extreme angles has be5 notic$ by ,admiral ,lageol4 ,hav+ tak5 ! portrait ( "o ( 8 fri5ds :5 8 eyes 7 direct$ to ! object-glass ( ! cam]a1 ! ,admiral made him look at an object #de6 to ! "r1 & took a second picture4 ,:5 ^! pictures 7 plac$ 9 ! /]eoscope1 & view$ 8)\t ceas+1 turn+ fir/ to ! "r & !n to ! left1 ! eyes ( ! portrait foll[ ?is motion z if !y 7 animat$40#ed ,?is fact mu/ h be5 notic$ 9 common /]eoscopic portraits by e p]son :o has view$ !m alt]nately ) ea* eye1 b x is n m]ely ! eyes :i* move4 ,! nose1 & inde$ e feature1 *anges its place1 or1 to speak m correctly1 ! :ole figure leaps f ! "o b9ocul> position into ! o!r4 ,z x is unpleasant to op5 & %ut ! eyes alt]nately1 ! same effect may be m agreeably produc$ 9 ord9>y portraits by m]ely int]cept+ ! light :i* falls ^u ea* picture1 or by mak+ an opaque scre5 pass quickly betwe5 ! eyes & ! l5s1 or imm$iately bel[ ! l5s1 s z to give successive vision ( ! pictures ) ea* eye1 & ) bo?4 ,! motion ( ! light reflect$ f ! r\nd eyeball has (t5 a /rik+ effect4 #ed ,cosmos1 ,feb4 #bi1 #ahef1 vol4 viii4 p4 #bjb4 ,f ^! discussions1 our read]s w obs]ve t ! sci5ce1 z well z ! art ( b9ocul> portraiture = ! /]eoscope1 is 9 a transition /ate 9 :i* x _c long rema94 ,! photograph] :o works ) a v l>ge l5s *ooses an angle :i* gives ! lea/ unfav\rable results2 8 rival1 ) a l5s ( less size1 *ooses1 on ! same pr9ciple1 a diff]5t angle2 & ! public1 :o are no judges ( ! result1 are delight$ ) _! pictures 9 relief1 & :5 _! noses are ei!r pull$ f _! face1 or flatt5$ ^u _! *eek1 or :5 an arm or a limb ?reat5s to escape f _! articulation1 !y are assur$ t nature & n art is to blame4 ,we come n[ to consid] "u :at circum/ances ! photograph] may place ! l5ses ( 8 b9ocul> cam]a at a great] di/ance ?an #b in*es1 or 8 two cam]as at a great] angle ?an t :i* we h fix$4 #a4 ,9 tak+ family portraits = ! /]eoscope1 ! cam]as mu/ be plac$ at an angle ( #b = #f feet1 :5 ! b9ocul> cam]a is n us$4 #b4 ,9 tak+ b9ocul> pictures ( any object :atev]1 :5 we wi% to see !m exactly z we d ) our two eyes1 we mu/ adopt ! same me?od4 #c4 ,if a portrait is want$ to assi/ a sculptor 9 modell+ a /atue1 a great angle might be adopt$1 9 ord] to %ew m ( ! head4 ,b 9 ?is case ! be/ way w\ld be to take ! correct social lik5ess1 & !n take photographs ( ! head 9 diff]5t azimu?s4 ,if we wi% to h a great] degree ( relief ?an we h ) our two eyes1 ei!r 9 view+ colossal /atues1 or build+s1 or l&scapes1 :]e ! deviation f nature does n1 z 9 ! human face1 affect ! expression1 or injure ! effect1 we mu/ increase ! di/ance ( ! l5ses 9 ! b9ocul> cam]a1 or ! angle ( direction ( ! common cam]a4 ,let u take ! case ( a colossal /atue #aj feet wide1 & suppose t dissimil> draw+s ( x ab\t ?ree in*es wide are requir$ = ! /]eoscope4 ,^! draw+s are =ty times n>r[] ?an ! /atue1 & mu/ be tak5 at su* a di/ance1 t ) ! b9ocul> cam]a ! relief w\ld be almo/ evanesc5t4 ,we mu/ !re=e suppose ! /atue to be r$uc$ n times1 & place ! semi-l5ses at ! di/ance n #b in*es4 ,if n #aj1 ! /atue #aj feet wide w be r$uc$ to _/1 or to #a foot1 & n #b1 or ! di/ance ( ! semi-l5ses w be #be in*es4 ,) ! l5ses at ?is di/ance1 ! dissimil> pictures ( ! /atue w reproduce1 :5 comb9$1 a /atue "o foot wide1 :i* w h exactly ! same appe>ance & relief z if we _h view$ ! colossal /atue ) eyes #be in*es di/ant4 ,b ! reproduc$ /atue w h also ! same appe>ance & relief z a /atue a foot wide r$uc$ f ! colossal "o ) ma!matical precision1 & x w !re=e be a bett] or m reliev$ repres5tation ( ! "w ( art ?an if we _h view$ ! colossal orig9al ) our own eyes1 ei!r "u a great]1 an equal1 or a less angle ( app>5t magnitude4 ,we h suppos$ t a /atue a foot broad w be se5 9 prop] relief by b9ocul> vision2 b x rema9s to be decid$ :e!r or n x w\ld be m advantage\sly se5 if r$uc$ ) ma!matical precision to a bread? ( #b in*es1 ! wid? ( ! eyes1 :i* gives ! vision ( a hemisph]e #b in*es 9 diamet] ) ! mo/ p]fect relief4#ee ,if we adopt ?is pr9ciple1 & call ,b ! bread? ( ! /atue ( :i* we require dissimil> pictures1 we mu/ make n ,b_/#b1 & n #b ,b1 t is1 ! di/ance ( ! semi-l5ses 9 ! b9ocul> cam]a1 or ( ! l5ses 9 two cam]as1 mu/ be made equal to ! bread? ( ! /atue4 ,9 conclud+ ?is *apt]1 x may be prop] to rem>k1 t unless we require an increas$ relief = "s special purpose1 l&scapes & build+s %\ld be tak5 ) ! normal b9ocul> cam]a1 t is1 ) its l5ses #b in*es di/ant4 ,sc5]y ( e k9d1 :e!r ( ! picturesque1 or ( ! sublime1 _c be made m beautiful or gr& ?an x is :5 se5 by ! travell] himself4 ,to add an artificial relief is b a trick :i* may />tle ! vulg>1 b _c gratify ! lov] ( :at is true 9 nature & 9 art4 ,! ,s+le ,l5s ,b9ocul> ,cam]a4 ,z e photograph] possesses a cam]a ) a l5s betwe5 #b & #c in*es 9 diamet]1 x may be useful to him to "k h[ he may conv]t x into a b9ocul> in/rum5t4 ,9 a cov] = ! l5s take two po9ts equidi/ant f ea* o!r1 & make two ap]tures1 c1 d1 ,fig4 #dc1 _/?s ( an in* 9 diamet]1 or ( any l>g] size t may be ?\ght prop]1 ?\gh _/ is ! prop] size4 ,place ! cov] on ! end ( ! tube1 & br+ ! l9e jo9+ ! ap]tures into a horizontal position4 ,clos+ "o ap]ture1 take ! picture ( ! sitt]1 or ( ! /atue1 ?r\gh ! o!r1 & :5 ! picture is %ift$ aside by ! usual contrivances = ?is purpose1 take ! picture ?r\gh ! o!r ap]ture4 ,^! w be good b9ocul> portraits1 fitt$ = any /]eoscope1 b p>ticul>ly = ! ,a*romatic ,read+ ,glass ,/]eoscope4 ,if great] relief is want$1 x may be obta9$ 9 l>g] l5ses by plac+ ! two ap]tures at ! greate/ di/ance :i* ! diamet] ( ! l5s w p]mit4 #ee ,x is only 9 a horizontal direction t we c see #ahj ( ! hemisph]e4 ,we w\ld require a circle ( eyes #b in*es di/ant to see a complete hemisph]e4 ,! ,b9ocul> ,cam]a made ! ,/]eoscope4 ,if ! l5ses ( ! b9ocul> cam]a1 :5 !y are :ole l5ses1 be made to sep>ate a little1 s t ! di/ance betwe5 ! c5tres ( _! inn] halves may be equal to #b in*es1 !y become a l5ticul> /]eoscope1 9 :i* we may view ! pictures :i* !y !mselves create4 ,! b9ocul> pictures are plac$ 9 ! cam]a 9 ! v place :]e _! negatives 7 =m$1 & ! obs]v]1 look+ ?r\gh ! halves ( 8 cam]a l5ses1 w see ! pictures unit$ & 9 relief4 ,if ! b9ocul> cam]a is made ( semi-l5ses1 we h only to place !m ) _! ?9 edges fac+ ea* o!r to obta9 ! same result4 ,x w appe>1 f ! discussions 9 ! foll[+ *apt]1 t su* a /]eoscope1 indep5d5tly ( its be+ a*romatic1 if ! cam]a is a*romatic1 w be ! mo/ p]fect ( /]eoscopic in/rum5ts4 ,! prec$+ me?ods are equally applicable to l&scapes1 ma*9es1 & in/rum5ts1 & to solid con/ructions ( e k9d1 :e!r !y be ! production ( nature or ( art4#ef #ef ,see ,*apt]s ,x4 & ,,xi4 ,,*apt] ,,ix4 ,,on ,,! ,,adaptation ,,( ,,! ,,pictures ,,to ,,! ,,/]eoscope4 --,,_! ,,size1 ,,position1 ,,& ,,illum9ation4 ,hav+ describ$ ! v>i\s =ms ( ! /]eoscope1 & ! me?od ( tak+ ! b9ocul> portraits & pictures to :i* x is to be appli$1 we h n[ to consid] ! relation t ought to exi/ betwe5 ! in/rum5t & ! pictures1--a subject :i* has n be5 notic$ by prec$+ writ]s4 ,if we unite two dissimil> pictures by ! simple conv]g5cy ( ! optical axes1 we %all obs]ve a c]ta9 degree ( relief1 at a c]ta9 di/ance ( ! eyes f ! pictures4 ,if we dim9i% ! di/ance1 ! relief dim9i%es1 & if we increase x1 x increases4 ,9 l mann]1 if we view ! dissimil> pictures 9 ! l5ticul> /]eoscope1 !y h a c]ta9 degree ( relief2 b if we use l5ses ( a high] magnify+ p[]1 s z to br+ ! eyes ne>] ! pictures1 ! relief w dim9i%1 & if we use l5ses ( a less magnify+ p[]1 ! relief w increase4 ,by br++ ! eyes ne>] ! pictures1 :i* we d by magnify+ !m z well z by approa*+ !m1 we increase ! di/ance betwe5 simil> po9ts ( ! two pictures1 & !re=e ! di/ance ( ^! po9ts1 :5 unit$1 f any plane 9 ! picture1 t is1 its relief w be dim9i%$4 ,= ! same reason1 ! dim9ution ( ! di/ance betwe5 simil> po9ts by ! removal ( ! eyes f ! picture1 w produce an increase ( relief4 ,?is w be readily und]/ood if we suppose ! eyes ,r1 ,l1 9 ,fig4 #bd1 to be br\ght ne>] ! plane ,,mn1 to ,r,l1 ! po9ts #a1 #a & #b1 #b w be unit$ at po9ts ne>] ,,mn ?an :5 ! eyes 7 at ,r1 ,l1 & consequ5tly _! relief dim9i%$4 ,n[ we h se51 t 9 tak+ portraits1 z expla9$ 9 ,fig4 #df1 we view ! two pictures1 ab1 ab1 ) ! eyes at ,e & ,e1 exactly1 & ) ! same relief 9 ! air1 z :5 we saw ! orig9al ,,ab1 f ,l1 ,l1 & !re=e ,ec is ! di/ance at :i* ! dissimil> pictures %\ld be view$ 9 ! /]eoscope1 9 ord] t we may see ! diff]5t p>ts ( ! solid figure "u _! prop] relief4 ,b ! di/ance ,ec ,lc is ! conjugate focal l5g? ( ! l5s ,l1 if "o l5s is us$1 or ! conjugate equival5t focal l5g?1 if two a*romatic l5ses are us$2 & consequ5tly e picture tak5 = ! /]eoscope %\ld be tak5 by a cam]a1 ! conjugate focal l5g? ( ^: l5s correspond+ to ! di/ance ( ! sitt]1 is equal to five in*es1 :5 x is to be us$ 9 ! common /]eoscope1 :i* has g5]ally t dep?4 ,betwe5 ! pictures & ! purely optical "p ( ! /]eoscope1 !re are o!r relations ( v consid]able importance4 ,! exclusion ( all ext]nal objects or s\rces ( light1 except+ t :i* illum9ates ! pictures1 is a po9t ( ess5tial importance1 ?\gh its advantages h nev] be5 appreciat$4 ,! spectacle /]eoscope held 9 ! h&1 ! reflect+ /]eoscope1 & ! op5 l5ticul> /]eoscope1 are all1 9 ?is respect1 defective4 ,! b9ocul> pictures mu/ be plac$ 9 a d>k box1 9 ord] to produce _! full effect2 & x w\ld be a great improvem5t on ! l5ticul> /]eoscope1 if1 on ! left & "r side ( ea* eye-tube1 a piece ( brass 7 to be plac$1 s z to prev5t any light f ent]+ ! left angle ( ! left eye1 & ! "r angle ( ! "r eye4#eg ,! eyes1 ?us protect$ f ! action ( all ext]nal light1 & see+ no?+ b ! picture1 w see x ) a di/9ctness & brilliancy :i* c\ld n o!rwise be obta9$4 #eg ,:5 any ext]nal light falls ^u ! eye1 its picture is reflect$ back f ! metallic surface ( ! ,dagu]reotype1 & a negative picture ( ! "p ( ! ,dagu]reotype opposite ea* eye is mix$ ) ! positive picture ( ! same "p4 ,! prop] illum9ation ( ! picture1 :5 se5 by reflect$ light1 is also a po9t ( ess5tial importance4 ,! me?od univ]sally adopt$ 9 ! l5ticul> /]eoscope is n good1 & is n ! "o :i* ,i f\nd to be ! be/1 & :i* ,i employ$ 9 ! fir/-con/ruct$ in/rum5ts4 ,! light :i* falls ^u ! picture is prev5t$ f rea*+ ! obs]v] only by its be+ incid5t at an angle great] or less ?an ! angle ( reflexion :i* w\ld c>ry x to 8 eyes4 ,a portion ( ! scatt]$ light1 h[ev]1 does rea* ! eye1 & 9 ,dagu]reotypes especially1 :5 any "p ( ! surface is injur$1 ! injury1 or any o!r imp]fection 9 ! plate1 is m di/9ctly se54 ,! illum9ation %\ld be lat]al1 ei!r by a diff]5t =m ( w9d[ 9 ! front1 or by op5+s on ! two sides1 or by bo? ^! me?ods4 ,:5 ! l5ticul> /]eoscope is ?us fitt$ up1 & ! pictures 9 ?is mann] illum9at$1 ! diff]5ce ( effect is equally great z x is betwe5 a picture z commonly se51 & ! same picture exhibit$ z a panorama or a diorama1 9 :i* no light rea*es ! eyes b t :i* radiates f ! pa9t+ itself1 ! reflexion f ! v>ni% be+ remov$ by oblique or lat]al illum9ation4 ,! great value ( transp>5t b9ocul> slides1 :5 ! picture is to be ^u glass1 is obvi\s f ! prec$+ consid]ations4 ,! illum9ation is uni=m & excell5t1 b c>e mu/ be tak5 to h ! gr\nd-glass 9 front ( ! picture1 or ! pap]1 :5 x is us$1 ( a v f9e gra91 s t x may ?r[ no black specks ^u ! sky or ! lights ( ! picture4 ,ano!r advantage ( ! transp>5t slides is1 t ! pictures are bett] protect$ f injury ?an ^? ^u pap]4 ,x is obvi\s f ^! consid]ations t ! size ( ! pictures is det]m9$1 z well z ! di/ance at :i* !y are to be view$4 ,mu* ignorance prevails ^u ?is subject1 bo? among practical photograph]s & optical writ]s4 ,l>ge b9ocul> pictures h be5 spok5 ( z desirable productions1 & x has be5 ass]t$1 & claim$ too1 z a valuable prop]ty ( ! reflect+ /]eoscope1 t x all[s u to use l>g] pictures ?an o!r in/rum5ts4 ,!re nev] 0 a great] mi/ake4 ,if we take a l>ge picture = ! /]eoscope we mu/ place x at a great di/ance f ! eye1 & consequ5tly use a l>ge /]eoscope4 ,a small picture1 se5 di/9ctly ne> ! eye1 is ! v same ?+ z a l>ge picture se5 at a great] di/ance4 ,! size ( a picture1 speak+ optically & correctly1 is measur$ by ! angle :i* x subt5ds at ! eye1 t is its app>5t magnitude4 ,a portrait ?ree in*es high1 = example1 & plac$ 9 ! l5ticul> /]eoscope five in*es f ! eye1 has ! same app>5t size z a ,kit ,cat portrait 9 oil ! size ( life1 ?ree feet high1 se5 at ! di/ance ( five feet1 ! di/ance at :i* x is commonly exam9$2 & if we increase ! magnify+ p[] s z to see ! ?ree-in* picture at ! di/ance ( two in*es1 x w h ! same app>5t size z ! ?ree feet oil portrait se5 at ! di/ance ( two feet4 ,if ! pictures us$ 9 ! /]eoscope 7 imp]fect pictures t w\ld n be> be+ magnifi$1 x w\ld be improp] to use !m2 b ! ,dagu]reotypes1 & ! transp>5t pictures1 :i* are tak5 by ! fir/ arti/s1 = ! l5ticul> /]eoscope1 w be> a magnify+ p[] t5 times great] ?an t :i* is appli$ to !m4 ,if we take a l>ge picture = ! /]eoscope1 we are compell$ by pictorial tru? to place x at a di/ance f ! eye equal to ! equival5t focal di/ance ( ! cam]a4 ,e picture 9 e cam]a has ! same app>5t magnitude z ! object :i* x repres5ts2 :e!r x be a human figure1 or ! mo/ di/ant l&scape2 & if we desire to see x 9 its true relief 9 ! /]eoscope1 we mu/ place x at a di/ance f ! eye equal to ! focal l5g? ( ! l5s1 :e!r x be an in* or a foot high4 ,!re is1 !re=e1 no?+ ga9$ by us+ l>ge pictures4 ,!re is1 on ! contr>y1 mu* inconv5i5ce 9 _! use4 ,!y are 9 !mselves less portable1 & require a l>g] /]eoscope2 & we believe1 no p]son :atev]1 :o is acqua9t$ ) ! p]fection & beauty ( ! b9ocul> slides 9 univ]sal use1 w\ld ei!r incur ! exp5se1 or take ! tr\ble ( us+ pictures ( a l>g] size4 ,9 ! beautiful comb9ation ( l5ticul> /]eoscopes1 :i* 0 exhibit$ by ,mr4 ,claudet1 ,mr4 ,williams1 & o!rs1 9 ! ,p>is ,exhibition1 & into :i* six or eight p]sons 7 look+ at ! same "t1 b9ocul> pictures ( a l>g] size c\ld n h be5 conv5i5tly us$4 ,b1 indep5d5tly ( ^! reasons1 ! "q ( l>ge pictures has be5 practically settl$4 ,no su* pictures are tak5 by ! ,dagu]reotypi/s or ,talbotypi/s1 :o are n[ enri*+ art ) ! *oice/ views ( ! antiquities1 & mod]n build+s1 & picturesque sc5]y ( e "p ( ! _w2 & ev5 if !y c\ld be obta9$1 !re are no in/rum5ts fitt$ = _! exhibition4 ,9 ! magnific5t collection ( /]eoscopic pictures1 am\nt+ to above a ?\s&1 adv]tis$ by ! ,london ,/]eoscopic ,company1 !re are no few] ?an sixty tak5 9 ,rome1 & repres5t+1 bett] ?an a travell] c\ld see !m !re1 ! anci5t & mod]n build+s ( t r5[n$ city4 ,7 ^! sixty views plac$ on ! sides ( a revolv+ polygon1 ) a /]eoscope be=e ea* ( its faces1 a score ( p]sons might1 9 ! c\rse ( an h\r1 see m ( ,rome1 & see x bett]1 ?an if !y _h visit$ x 9 p]son4 ,at all ev5ts1 ^? :o are nei!r able nor will+ to be> ! exp5se1 & und]go ! toil ( p]sonal travel1 w\ld1 9 su* a panorama1--an analytical view ( ,rome1--acquire z p]fect a k ( its localities1 anci5t & mod]n1 z ! ord9>y travell]4 ,9 ! same mann]1 we might /udy ! o!r metropolitan cities ( ! _w1 & travel f !m to its riv] & m\nta9 sc5]y1--admir+ its noble ca/les 9 our desc5t ( ! ,rh9e1--its gr& & wild sc5]y on ! banks ( ! ,mississippi1 or ! ,or9oco1--! m\nta9 gorges1 ! glaci]s1 & ! peaks ( ! ,alps & ! ,ural1--& ! m sublime gr&eur :i* reigns among ! solitudes ( ! ,himalaya & ! ,&es4 ,! foll[+ g5]al rule = tak+ & comb9+ b9ocul> pictures is ! demon/rable result ( ! pr9ciples expla9$ 9 ?is *apt]3-- ,suppos+ t ! cam]a obscura employ$ to take b9ocul> portraits1 l&scapes1 c41 gives p]fect repres5tations ( !m1 ! relief picture 9 ! /]eoscope1 produc$ by _! sup]position & b9ocul> union1 w n be correct & tru?ful1 unless ! dissimil> pictures are plac$ 9 ! /]eoscope at a di/ance f ! eyes1 equal to ! focal di/ance1 real or equival5t1 ( ! object-glass or object-glasses ( ! cam]a1 &1 :atev] be ! size ( ! pictures1 !y w appe>1 :5 !y are s plac$1 ( ! same app>5t magnitude1 & 9 ! same relief1 z :5 !y 7 se5 f ! object-glass ( ! cam]a by ! photograph] himself4 ,,*apt] ,x4 ,,application ,,( ,,! ,,/]eoscope ,,to ,,pa9t+4 ,hav+ expla9$ ! only true me?od ( tak+ b9ocul> portraits :i* w appe> 9 correct relief :5 plac$ 9 ! /]eoscope1 we %all proce$ 9 ?is *apt] to po9t out ! application ( ! /]eoscope to ! art ( pa9t+ 9 all its bran*es4 ,9 do+ ?is we mu/ n =get h[ mu* ! /]eoscope owes to photography1 & h[ mu* ! arts ( design might reasonably expect f ! sol> p5cil1 :5 rightly guid$1 ev5 if ! /]eoscope _h nev] be5 inv5t$4 ,:5 ! processes ( ! ,dagu]reotype & ,talbotype1 ! si/] arts ( ,photography1 7 fir/ giv5 to ! _w1 x 0 ! expectation ( "s1 & ! dread ( o!rs1 t ! excell5ce & correctness ( _! del9eations w\ld ca/ into ! %ade ! less tru?ful repres5tations ( ! portrait & ! l&scape pa9t]4 ,an inv5tion :i* sup]s$es animal p[]1 or ev5 ! pr(essional lab\r ( man1 might h be5 ju/ly hail$ z a social bless+1 b an art :i* %\ld sup]s$e ! ef=ts ( g5ius1 & int]f]e ) ! ex]cise ( ^? creative p[]s :i* repres5t to u :at is beautiful & sublime 9 nature1 w\ld1 if su* a ?+ 7 possible1 be a social evil4 ,! arts ( pa9t+1 sculpture1 & ar*itecture h 9 e age1 & 9 e region ( civilisation1 call$ into ex]cise ! l(tie/ g5ius & ! deepe/ reason ( man4 ,consecrat$ by piety1 & hall[$ by affection1 ! *oice/ productions ( ! p5cil & ! *isel h be5 pres]v$ by ! lib]ality ( individuals & ! munific5ce ( pr9ces1 :ile ! palaces ( sov]eigns1 ! edifices ( social life1 ! temples ( religion1 ! wat*-t[]s ( w>1 ! obelisks ( fame1 & ! mausolea ( dome/ic grief1 /& "u ! azure cupola ( heav51 to atte/ by _! liv+ beauty1 or _! ru9$ gr&eur1 ! g5ius & lib]ality :i* gave !m bir?4 ,to ! cultivation & patronage ( su* noble arts1 ! vanity1 ! hopes1 & ! holie/ affections ( man /& irrevocably pl$g$2 & we %\ld deplore any inv5tion or discov]y1 or any tide 9 ! nation's ta/e1 :i* %\ld p>alyse ! arti/'s p5cil1 or break ! sculptor's *isel1 or div]t into new *annels ! g5ius :i* wields !m4 ,b in/ead ( sup]s$+ ! arts ( design1 photography w b supply !m ) new mat]ials1--) collections ( co/ume1--) /udies ( drap]y & ( =ms1 & ) sc5es 9 life1 & facts 9 nature1 :i*1 if !y possess at all1 !y possess imp]fectly1 & )\t :i* art mu/ be /ation>y1 if %e does n langui% & decl9e4 ,s5tim5ts analog\s to ^! h be5 m pr(essionally express$ by ,m4 ,del>o*e1 a di/+ui%$ ,fr5* arti/1--by ,sir ,*>les ,ea/lake1 ^: ta/e & k ( art is unrivall$1--& by ,mr4 ,rusk91 :o has already giv5 laws to art1 & ^: g5ius is de/9$ to elevate & to re=m x4 ,m4 ,del>o*e consid]s photography 8z c>ry+ to su* p]fection c]ta9 ( ! ess5tial pr9ciples ( art1 t !y mu/ become subjects ( /udy & obs]vation1 ev5 to ! mo/ accompli%$ arti/40444 8,! f9i% ( inconceivable m9ut5ess10 he says1 8di/urbs 9 no respect ! repose ( ! masses1 nor impairs 9 any way ! g5]al effect4444 ,! correctness ( ! l9es1 ! precision ( ! =ms 9 ! designs ( ,m4 ,dagu]re1 are z p]fect z x is possible !y c be1 & yet1 at ! same "t1 we discov] 9 !m a broad & en]getic mann]1 & a :ole equally ri* 9 hue & 9 effect4 ,! pa9t] w obta9 by ?is process a quick me?od ( mak+ collections ( /udies1 :i* he c\ld n o!rwise procure )\t mu* "t & lab\r1 & 9 a /yle v f> inf]ior1 :atev] might be 8 tal5ts 9 o!r respects40 ,9 ! same _s1 ,mr4 ,rusk9#eh consid]s 8! art ( photography z enabl+ u to obta9 z _m memor&a ( ! facts ( nature z we ne$20 & long be=e ,mr4 ,talbot taught u to fix ^u pap] ! pictures ( ! cam]a obscura1 ! ,rev4 ,john ,?omson1 "o ( ! mo/ di/+ui%$ ( our ,scotti% l&scape pa9t]s1 /udi$1 9 "o ( ^! in/rum5ts1 ! =ms & col\rs ( ! sc5es :i* he 0 to repres5t4 ,o!r arti/s1 bo? 9 portrait & 9 l&scape1 n[ avail !mselves ( photography1 bo? z an auxili>y & a guide 9 _! pr(ession2 b !re are c]ta9 difficulties & imp]fections 9 ! art itself1 & s _m precautions requir$ 9 its "r application1 :e!r we use its pictures s+le1 z repres5tations on a plane1 or take !m b9ocul>ly1 to be rais$ into relief by ! /]eoscope1 t we mu/ draw f ! pr9ciples ( optics ! only rules :i* c be ( real s]vices to ! arts ( design4 #eh ,mod]n ,pa9t]s1 vol4 iii41 ,preface1 pp4 #aa1 #ab4 ,9 pa9t+ a l&scape1 a build+1 a figure1 or a gr\p ( figures1 ! object ( ! arti/ is to repres5t x on 8 canvas j z he sees x1 hav+ previ\sly select$ ! be/ po9t ( view1 & m>k$ = omission or improvem5t :at is n beautiful1 or :at w\ld int]f]e ) ! effect ( 8 picture z a "w ( high art4 ,8 fir/ /ep1 !re=e1 is to fix ^u ! size ( 8 canvas1 or ! di/ance at :i* ! picture is to be se51 :i* det]m9es its size4 ,8 own eye is a cam]a obscura1 & ! relation betwe5 ! picture or image on its ret9a is su*1 t if we c\ld view x f ! c5tre ( curvature ( ! ret9a1 7! c5tre ( visible direction17 a di/ance ( half an in*1 x w\ld h precisely ! same app>5t magnitude z ! object ( :i* x is ! image4 ,let u n[ suppose t ! arti/ wi%es to avail himself ( ! picture 9 ! cam]a obscura z receiv$ ei!r on pap] or gr\nd-glass1 or ( a photograph ( ! sc5e he is to pa9t4 ,he mu/ make use ( a cam]a ^: focal l5g? is equal to ! di/ance at :i* 8 picture is to be se51 & :5 ! picture ?us tak5 is view$ at ?is di/ance 7suppose two feet7 x w1 z a :ole1 & 9 all its p>ts1 h ! same app>5t magnitude z ! orig9al object4 ,?is w be und]/ood f ,fig4 #dg1 9 :i* we may suppose ,h to be ! l5s ( ! cam]a1 ,,rb ! object1 & ,hy ! di/ance at :i* x is to be view$4 ,! size ( ! picture tak5 ) a l5s at ,h1 ^: focal l5g? is ,hy1 w be br1 & an eye plac$ at ,h w see ! picture br "u an angle b,hr1 equal to ! angle ,,rhb1 "u :i* ! real object ,,rb 0 se5 by ! arti/ f ,h4 ,9 l mann]1 a l>g] picture1 byr1 tak5 by a cam]a ! focal di/ance ( ^: l5s at ,h is ,hy1 w be an accurate repres5tation ( ! object ,,rb1 :5 view$ f ,h1 & ( ! same app>5t magnitude4 ,if ei!r ( ^! pictures1 br or br1 are view$ f great] or less di/ances ?an ,hy1 or ,hy1 !y w n be correct repres5tations ( ! object ,,rb1 ei!r 9 app>5t magnitude or =m4 ,t !y w be ( a diff]5t app>5t magnitude1 great] :5 view$ at less di/ances ?an ,hy1 ,hy1 & less :5 view$ at great] di/ances1 is too obvi\s to require any illu/ration4 ,t !y w diff] 9 =m1 or 9 ! relative app>5t size ( _! p>ts1 has1 s f> z ,i "k1 n be5 conjectur$4 ,9 ord] to %ew ?is1 let u suppose a man six feet high to occupy ! =egr\nd1 & ano!r ( ! same size to be plac$ 9 ! middle di/ance1 ! di/ance ( ! two f ! arti/ be+ t5 & tw5ty feet4 ,! app>5t magnitudes ( ^! two m5 on ! photograph w be z two to "o2 & if we look at x at any di/ance great] or less ?an ! focal l5g? ,hy ( ! l5s1 ! same proportion ( two to "o w be pres]v$1 :]eas if we look at ! orig9al figures at a great] or less di/ance f !m ?an ! place ( ! arti/1 ! ratio ( _! app>5t magnitudes w be alt]$4 ,if ! arti/1 = example1 advances five feet1 ! ne>e/ man w be five feet di/ant & ! o!r fifte5 feet1 s t _! app>5t magnitude w n[ be z ?ree to "o4 ,illu/ration3 ,,fig4 #dg4 ,! same obs]vations apply to a portrait ( ! human face4 ,9 look+ at a human pr(ile let u suppose ! bread? ( ! nose to be "o in*1 t ( ! e> "o in*1 & t we view ?is pr(ile at ! di/ance ( ?ree feet f ! e>1 :i* is two in*es ne>] ! obs]v] ?an ! nose4 ,! app>5t magnitude ( ! e> & nose w be z ?irty-eight to ?irty-six in*es1 :]eas if we view ! pr(ile f ! di/ance ( "o foot ! ratio w be z f\rte5 to twelve1 t is1 ! e> w be increas$ 9 app>5t size m ?an ! nose4 ,h5ce x foll[s t all pictures %\ld be view$ "u ! same angle ( app>5t magnitude "u :i* !y 7 se5 by ! arti/ z tak5 photographically1 = if we view !m at a great] or less angle ?an ?is we d n see ! same picture z :5 we look$ at ! orig9al l&scape or portrait1 "u ! same angle ( app>5t magnitude4 ,f ! obs]vations made 9 ! prec$+ ,*apt] on photographic & /]eoscopic portraiture1 ! read] mu/ h already drawn ! inf]5ce t ! same l&scape or build+1 se5 at diff]5t di/ances1 v>ies ess5tially 9 its "*1--beauties disclos+ !mselves & defects disappe>+ z we approa* or rec$e f !m4 ,! picture 9 ! cam]a1 !re=e1 z us$ by ,mr4 ,?omson1 or1 :at is /ill bett]1 ) ! exception ( col\r1 ! photograph obta9$ by ! same in/rum5t1 w supply ! arti/ ) all ! g5]al mat]ials = 8 picture4 ,! photograph w diff] consid]ably f any sket* :i* ! arti/ may h himself made1 ow+ to c]ta9 optical illusions to :i* 8 eye is subject4 ,! hills & o!r v]tical l9es 9 ! di/ance w be l[] 9 ! photograph ?an 9 8 sket*4#ei ,! v]tical l9es ( build+s w conv]ge upw>ds 9 ! photograph1 z !y ought to d1 9 rec$+ f ! eye2 & 9 ! same picture !re w be a confusion1 z we %all aft]w>ds %ew1 9 ! del9eation ( ne> & m9ute objects 9 ! =egr\nd1 increas+ ) ! size ( ! l5s :i* he has employ$4 #ei ,sir ,francis ,*antrey1 ! celebrat$ sculptor1 %ew$ me1 _m ye>s ago1 a ,sket*-,book1 conta9+ num]\s draw+s :i* he _h made ) ! ,cam]a ,lucida1 :ile travell+ f ,london to ,ed9burgh by ! ,lakes4 ,he po9t$ out to me ! flatness1 or r l[ness1 ( hills1 :i* to 8 own eye appe>$ mu* high]1 b :i*1 not)/&+1 gave to him ! idea ( a great] elevation4 ,9 ord] to put ?is op9ion to ! te/ ( exp]im5t1 ,i _h draw+s made by a skilful arti/ ( ! ?ree ,eildon hills opposite my resid5ce on ! ,twe$1 & 0 surpris$ to obta91 by comp>+ !m ) _! true p]spective outl9es1 a /rik+ confirmation ( ! obs]vation made by ,sir ,francis ,*antrey4 ,9 8 admirable *apt] 8,on ,f9i%10 ,mr4 ,rusk9 has e/abli%$1 beyond a d\bt1 ! mo/ important pr9ciple 9 ! art ( pa9t+4 8,! f9i%+ ( nature10 he /ates1 8consi/s n 9 ! smoo?+ ( surface1 b ! fill+ ( space1 & ! multiplication ( life & ?\ght20 & h5ce he draws ! conclusion1 t 8f9i%+ means1 9 art1 simply tell+ m tru?40 ,titian1 ,t9toret1 ,bell9i1 & ,v]onese h1 z he has %ewn1 wr\ght ^u ?is pr9ciple1 del9eat+ ve9 by ve9 9 ! leaf ( ! v9e1 petal by petal 9 ! borage-blossoms1 ! v snail-%ells on ! gr\nd1 ! /ripe ( black b>k 9 ! bir*-tree1 & ! clu/]s ( ! ivy-leav$ toad-flax 9 ! r5ts ( _! walls2 & we h se5 t a mod]n arti/1 ,del>o*e1 consid]s a f9i% ( inconceivable m9ut5ess z nei!r di/urb+ ! repose ( ! masses1 nor int]f]+ ) ! g5]al effect 9 a picture4 ,! ,pre-,raphaelites1 !re=e1 may appeal to high au?ority = ! c>d9al doctr9e ( _! cre$2 & :atev] be _! errors 9 judgm5t or 9 ta/e1 !y h inaugurat$ a revolution :i* w release art f its fett]s1 & give x a fre] & a nobl] aim4 ,nature is too gr& 9 h] m9ut5ess1 & too beautiful 9 h] humility1 to be ov]look$ 9 ! poetry ( art4 ,if h] t5d]e/ & mo/ delicate =ms are wor?y ( admiration1 %e w dem& f ! arti/ 8 highe/ p[]s ( design4 ,if ! liv+ organizations ( ! teem+ e>?1 ^u :i* we h\rly tread1 are mat*less 9 /ructure1 & fasc9at+ 9 col\r1 ! palette ( ! pa9t] mu/ surr5d] to !m its *oice/ t9ts4 ,9 ! =egr\nd ( ! highe/ art1 ! snail-%ell may in(f5sively creep f b5ea? ! )]$ leaf or ! liv+ blade2 ! h>ebell & ! violet may claim a place 9 ! sylvan dell2 ! moss may display its t9y frond1 ! gn>l$ oak or ! twi/$ p9e may dem& ! recognition ( ! botani/1 :ile ! ca/le wall rises 9 gr&eur beh9d !m1 & ! gigantic cliffs or ! l(ty m\nta9 range t]m9ate ! sc5e4 ,if ^! views are s\nd1 ! man ( ta/e w no long] endure slov5l9ess 9 art4 ,he w dem& tru? z well z beauty 9 ! l&scape2 & t pa9t] may *ange 8 pr(ession :o _c impress geology ^u 8 rocks1 & botany ^u 8 plants & trees1 or :o refuses to display1 ^u 8 summ] or 8 autumn tablet1 ! gre5 crop z well z ! gr[+ & ! ga!r$ h>ve/4 ,?us enl>g$ 9 its p[]s & elevat$ 9 its purposes1 ! art ( pa9t+ w be inve/$ ) a new "*1 dem&+ f its vot>ies high] skill & m ext5d$ k4 ,9 =m] times1 ! m9ute & accurate del9eation ( nature 0 a task almo/ impossible1 requir+ an am\nt ( toil :i* c\ld h>dly be repaid ev5 :5 slightly p]=m$2 b sci5ce has n[ furni%$ art ) ! mo/ p]fect means ( arre/+1 9 _! mo/ delicate =ms1 e object1 h[ev] m9ute1 t c ent] into ! composition ( a picture4 ,^! means are ! arts ( photography & /]eoscopic re-comb9ation1 :5 rightly direct$1 & x is ! object ( ! pres5t *apt] to %ew h[ ! arti/ may be/ avail himself ( _! valuable & indisp5sable aid4 ,e c\ntry & di/rict1 & ev5 diff]5t p>ts ( ! same di/rict1 h a ,flora & ,geology peculi> to !mselves2 & ! arti/ :o und]takes to repres5t its beauties owes to tru? ! same obligations z ! botani/ :o is to describe its plants1 or ! m9]alogi/ its rocks & /ones4 ,! critic c\ld n1 9 =m] times1 expect m details f 8 unaid$ p5cil ?an x has g5]ally furni%$2 b ) ! means n[ at 8 comm&1 he mu/ collect1 l ! naturali/1 all ! mat]ials = 8 subject4 ,aft] ! cam]a has giv5 him ! great features ( 8 l&scape1 he mu/ appeal to x = accurate del9eations ( its m9ut] p>ts1--! trunks1 & /ems1 & leafage ( 8 trees--! dipp+ /rata ( its s&/one b$s--! contortions ( its knead$ gneiss1 or ! rud] features ( its trap & its granite4 ,= ! mo/ important ( ^! details he w f9d ! cam]a1 z at pres5t con/ruct$1 ( little s]vice4 ,x is fitt$ only to copy surfaces2 & !re=e1 :5 direct$ to solid bodies1 su* z liv+ be+s1 /atues1 c41 x gives false & hide\s repres5tations ( !m1 z ,i h %ewn 9 a prec$+ *apt]4 ,x is peculi>ly defective :5 appli$ to p>ts ( bodies at diff]5t di/ances f x1 & ( a less diamet] ?an ! l5s4 ,! photograph ( a cube tak5 by a l5s ( a great] diamet]1 w display five ( its sides 9 a position1 :5 its true p]spective repres5tation is simply a s+le squ>e ( its surface4 ,:5 appli$ to trees1 & %rubs1 & fl[]s1 its pictures are /ill m unsatisfactory4 ,e /em & leaf small] ?an ! l5s1 ?\gh absolutely opaque1 is transp>5t1 & leaves & /ems beh9d & beyond are se5 l gho/s ?r\gh ! photographic image4 ,illu/ration3 ,,fig4 #dh4 ,?is w be und]/ood f ,fig4 #dh1 9 :i* ,,ll is ! l5s ( ! cam]a1 ,,ab ! bread? ( ! trunk or /em ( a tree less ?an ,,ll 9 wid?4 ,draw ,,la1 ,,lb1 t\*+ ,,ab 9 ! po9ts ,a1 ,b1 & cross+ at ,c4 ,objects beh9d ,,ab1 & plac$ )9 ! angle ,,acb1 w n h any images ( !m =m$ by ! l5s ,,ll1 because none ( ! rays :i* proce$ f !m c fall ^u ! l5s1 b objects plac$ )9 ! angle ,,ecf1 h[ev] remote be _! di/ance1 w h images ( !m =m$ by ! l5s4 ,if ,d1 = example1 be a leaf or a fruit1 or a portion ( a bran*1 ! rays :i* x emits w fall ^u ! portions ,lm1 ,ln ( ! l5s1 det]m9$ by draw+ ,dm1 ,dn t\*+ ,,ab1 & an image ( x w be =m$ 9 ! c5tre ( ! photographic image ( ,,ab1 z if ,,ab 7 transp>5t4 ,?is image w be =m$ by all ! portions ( ! surface ( ! l5s on :i* ! %ad[ ( ,,ab1 =m$ by rays emanat+ f ,d1 w\ld n fall4 ,if ! object ,d is m remote1 ! %ad[ ( ,,ab w dim9i% 9 size1 & ! image ( ! object w be =m$ by a great] portion ( ! l5s4 ,if ! sun 7 to be 9 ! direction ,,mn1 8 image w\ld appe> 9 ! c5tre ( ! trunk or /em1 correspond+ to ,,ab1 ,fig4 #di4 ,illu/ration3 ,,fig4 #di4 ,if ! /em occupies any o!r position1 ab1 ,fig4 #dh1 9 ! l&scape1 objects1 su* z d1 )9 ! angle ecf1 w h images ( !m =m$ )9 ! correspond+ portion ( ! trunk or /em4 ,h5ce1 if ,,ab1 ,fig4 #di1 repres5ts ! %ad[ ( ! /em across ! l5s ,,ll1 ! image ( any object1 :i* if lum9\s w\ld give ?is %ad[1 w be =m$ )9 ! photographic image ( ! /em1 & z e "p ( x may h bran*es1 or leaves1 or fruit beh9d x1 its photographs w be fill$ ) _! pictures1 :i* w h ! same di/9ctness z o!r equidi/ant p>ts ( ! l&scape4 ,^! obs]vations are applicable to ! limbs & sl5d] p>ts ( animate & inanimate figures1 :5 !y are ( a less size ?an ! l5s ) :i* _! photograph is tak54 ,!y w be transp>5t to all objects beh9d !m1 & _! true =ms & %ades _c be tak5 ) ! cam]as n[ 9 use4#fj ,9 ord]1 !re=e1 to collect f nature ! mat]ials ( 8 pr(ession1 ! arti/ mu/ use a cam]a ) a l5s n mu* l>g] ?an ! pupil ( 8 eye1 & ) su* an in/rum5t he w obta9 ! mo/ correct draw+s ( ! trunks & /ems ( trees1 ( ! texture & m>k+s ( _! b>k1 ( ! =m ( _! leaves1 & ( all ^? peculi>ities ( /ructure & ( leafage by :i* alone ! trees ( ! =e/ c be di/+ui%$4 ,9 l mann]1 he w obta9 ! mo/ correct repres5tations ( ! rocks & precipices1 & ! individual /ones#fa :i* may ent] into 8 picture1--( ! plants :i* spr+ f _! crevices or gr[ at _! base1 & ( ^? fl[]s 9 _! native grace & beauty1 :i* hi!rto he has ei!r drawn f recollection1 or copi$ f ! =mal repres5tations ( ! botani/4 #fj ,by us+ l>ge l5ses1 we may obta9 ! picture ( an object )9 ! picture ( an opaque "o 9 front ( x2 & ) a telescope1 we may see ?r\gh opaque objects ( a c]ta9 size4 ,_m s+ul> exp]im5ts may be made by tak+ photographs ( solid objects1 simple or comp\nd1 ) l5ses l>g] ?an ! objects !mselves4 #fa ,9 a l&scape by ,mr4 ,wall] ,paton1 call$ ! 8,highl& ,/ream10 n[ 9 ! ,ed9burgh ,exhibition1 ! =egr\nd consi/s pr9cipally ( a b$ ( wat]-worn /ones1 on ! m>g9 ( a pool at ! bottom ( a wat]fall4 ,! /ones are s exquisitely pa9t$1 t nature only c\ld h furni%$ ! orig9als4 ,we may exam9e !m at a few in*es' di/ance1 & recognise =ms & /ructures ) :i* we h be5 long famili>4 ,a wat]-ousel1 peculi> to ,scotti% brooks & riv]s1 p]*$ ^u "o ( !m1 looks z anxi\sly ar\nd z if a s*oolboy 7 ab\t to avail himself ( ! missiles at 8 feet4 ,9 addition to _! correctness z true repres5tations ( natural =ms1 photographs h a peculi> value1 = :i* no lab\r or skill on ! "p ( ! arti/ c comp5sate4 ,9 draw+ ! sket* ( a l&scape1 or del9eat+ ! trees1 rocks1 & foliage :i* are ne> him1 or ! objects 9 ! middle or remote di/ance1 sev]al h\rs mu/ be sp5t4 ,dur+ ?is p]iod1 ! l&scape & its individual p>ts are und]go+ no inconsid]able *ange4 ,a breeze may di/urb ! masses ( 8 foliage1 & b5d 8 tree /ems1 & ruffle 8 v]dure1 & ?r[ new reflect$ lights ^u ! wav+ crops1 :ile e direct light is *ang+ 9 int5sity & direction dur+ ! culm9ation or desc5t ( ! sun4 ,:at he has del9eat$ 9 ! morn+ w h>dly correspond ) :at he draws at noon1 & ! di/ances :i* at "o "t are f9ely m>k$ 9 a]ial p]spective1 w disappe>1 or ev5 suff] inv]sion by v>iations 9 ! int5sity & position ( ! haze4 ,if cottages1 or ca/les1 or build+s ( any k9d1 ent] into ! picture1 ! %ad[s ( _! projections1 & ! lights ^u _! walls & ro(s w1 9 sun%9e1 und]go /ill great] v>iations1 & ! arti/ w be p]plex$ ) ! ana*ronisms & inconsi/5cies ( 8 *oice/ mat]ials4 ,! l&scape ?us compos$ 9 pat*es w1 9 its photograph1 h a v diff]5t aspect1 z mu* 9 its =ms z 9 its lights & %ad[s4 ,! tru?s ( nature are fix$ at "o in/ant ( "t2 ! self-del9eat$ l&scape is embalm$ amid ! co-exi/+ ev5ts ( ! physical & social _w4 ,if ! sun %9es1 8 rays ?r[ _! gild+ on ! picture4 ,if ! ra9-%[] falls1 ! e>? & ! trees gli/5 ) its reflexions4 ,if ! w9d bl[s1 ! p>tially oblit]at$ foliage w display ! ext5t ( its agitation4 ,! objects ( /ill life1 too1 give reality & animation to ! sc5e4 ,! /reets display _! /ation>y *>iots1 ! esplanade its milit>y array1 & ! m>ket-place its colloquial gr\ps1 :ile ! fields are /udd$ ) ! =ms & attitudes ( animal life4 ,! incid5ts ( "t & ! =ms ( space are ?us simultane\sly record$1 & e picture f ! sob] palette ( ! sun becomes an au!ntic *apt] 9 ! hi/ory ( ! _w4#fb #fb ,^! views are well illu/rat$ by ! rem>kable photographs ( ! ,crimean w>4 ,b1 h[ev] valuable photography has become to ! arti/1 sci5ce has rec5tly giv5 him ano!r important auxili>y4 ,9 ord] to make ?is available1 he mu/ employ a small pocket b9ocul> cam]a1 to take d\ble pictures to be unit$ 9 ! /]eoscope4 ,8 trees w ?us exhibit ! r\ndness ( _! trunks & /ems1 ! leaves & bran*es w place !mselves at _! prop] di/ance1 & he w discov] ! reason ( peculi> effects :i* 9 ! plane photograph he has be5 unable to und]/&4 ,see+ t 8 own picture is to be ^u a plane surface1 ,i c h>dly expect to conv9ce ! arti/ t he w obta9 m in=mation by reproduc+ ! orig9al 9 relief4 ,x is a fact1 h[ev]1 beyond dispute1 t effects are produc$ by ! /]eoscopic union ( two plane photographs :i* are invisible 9 ! s+le picture4 ,^! effects1 :i* are *iefly ^? ( lu/re & %ade1 are peculi>ly rem>kable 9 ,dagu]reotype1 & x is by no means easy to expla9 ! cause4 ,9 a ,dagu]reotype1 = example1 ( two figures 9 black bronze1 ) a high metallic lu/re1 x is impossible1 by look+ at ! s+le picture1 to tell ! mat]ial ( :i* !y are made2 b ! mom5t !y are unit$ into /]eoscopic relief _! true "* is in/antly se54 ,9 a ,dagu]reotype ( ,alex&] & ,bucephalus1 portions ( ! figure seem z if %ad$ ) ,*9a ink ( a ne>ly uni=m t9t1 b :5 se5 9 relief ! peculi> %ade entirely disappe>s4 ,! /]eoscopic comb9ation ( two surfaces ( diff]5t int5sities1 ?\gh ( ! same col\r1 produces effects :i* h n yet be5 suffici5tly /udi$4 ,b1 indep5d5tly ( ^! peculi>ities1 ! arti/ w c]ta9ly d]ive m aid f 8 l&scape 9 relief1 & f ! /udy ( its individual p>ts1 9 _! r\ndness & relative di/ances1 ?an :5 he exam9es !m 9 _! plane repres5tations4 ,! %ad[s :i* ! bran*es ( leaves ca/ ^u ! trunks & /ems ( 8 trees he w be able to trace to ! causes :i* produce !m4 ,effects 9 outl9e1 z well z 9 light & %ad[1 :i* may p]plex him1 w f9d an explanation 9 ! relative di/ances & diff]5ces ( app>5t magnitude ( individual p>ts2 &1 aft] becom+ famili> ) 8 l&scape 9 relief1 z x exi/s 9 ,nature1 he _c fail to acquire new pr9ciples & me?ods ( manipulation4 ,nature flatt5$ ^u pap] or metal1 & ,nature r\nd & plump1 z if fre% f ! *isel ( ! ,div9e sculptor1 mu/ tea* v diff]5t lessons to ! aspir+ arti/4 ,! hi/orical pa9t]1 or ! m humble arti/ :o del9eates ! sc5es ( common or dome/ic life1 w d]ive f ! photographic cam]a & ! /]eoscope advantages ( equal importance4 ,! h]o1 ! sage1 & ! m>tyr1 drawn f liv+ orig9als1 may be plac$ 9 ! sc5es :]e !y suff]$1 or 9 ! localities :i* !y hall[$4 ,! lawgiv] ( ,egypt1 ?\gh he exi/s only 9 ! pa9t]'s eye1 may take 8 place beside ! giant flanks ( ,horeb or ! awe-inspir+ summit ( ,m\nt ,s9ai2 & ,he :om we may n "n may *all5ge our love & admiration amid ! sun-pa9t$ sc5es ( 8 y\?1 ( 8 miracles1 & ( 8 humiliation4 ,! fragm5ts ( anci5t gr&eur :i* "t & w> h sp>$1 ! relics ( bygone ages :i* h resi/$ ! de/ructive elem5ts1 w1 z ! mat]ials ( art1 give reality & tru? to ! pictorial hi/ory ( times pa/1 :ile ! pa9t] ( mod]n ev5ts c comm& ! mo/ accurate repres5tations n only ( ! co/ume1 b ( ! v p]sons ( ! great m5 ^: de$s he is call$ ^u to immortalize4 ,! h]oes ( ! ,crimean w>1 :e!r fri5ds or foes1 w be descri$ 9 ! tr5*es 9 :i* !y f\ght1 amid ! ranks :i* !y l$ to victory1 or among ! wrecks ( ! fatal enc\nt] 9 :i* !y fell4 ,! sun w ?us become ! hi/oriograph] ( ! future1 & 9 ! fidelity ( 8 p5cil & ! accuracy ( 8 *ronicle1 tru? itself w be embalm$ & hi/ory cease to be fabul\s4 ,b ev5 9 ! n>r[]1 ?\gh n less hall[$ sph]e ( dome/ic life1 :]e ! magic names ( k9dr$ & home are inscrib$1 ! realities ( /]eoscopic photography w excite ! mo/ ?rill+ int]e/4 ,9 ! transition =ms ( 8 (fspr+1 :i* l9k infancy ) manhood1 ! p>5t w recognise ! progress ( 8 mortal c>e]1 & 9 ! successive phases :i* m>k ! sunset ( life1 ! /ripl+ 9 8 turn w read ! lesson t 8 pilgrimage too has a t]m :i* mu/ close4 ,nor are su* del9eations int]e/+ only z works ( art1 or z inc5tives to virtue2 !y are in/9ct ) associations vivid & ende>+4 ,! picture is connect$ ) its orig9al by s5sibilities peculi>ly t5d]4 ,x 0 ! v light :i* radiat$ f h] br[1--! id5tical gleam :i* light$ up h] eye1--! hectic flu% or ! pallid hue t hung ^u h] *eek1 :i* p5cill$ ! *]i%$ image1 & fix$ !mselves = ev] !re4 ,,*apt] ,,xi4 ,,application ,,( ,,! ,,/]eoscope ,,to ,,sculpture1 ,,ar*itecture1 ,,& ,,eng9e]+4 ,to ! arts ( sculpture & ar*itecture1 ! processes ( b9ocul> photography & /]eoscopic comb9ation are p>ticul>ly applicable4 ,! l&scape pa9t] has e day )9 8 rea* examples ( ! picturesque1 ! wild & ! sublime 9 nature4 ,9 ! fields :i* surr\nd him1 9 ! riv]1 or ev5 9 ! 8brook t bubbles by10 on ! %ore1 on ! hea?1 or on ! m\nta9 side1 he has ! *oice ( mat]ials = e dep>tm5t ( 8 art4 ,! sculptor has no su* advantage4 ,swa!d 9 imp5etrable drap]y ! human figure mocks 8 eag] eye1 & x is only by /ol5 glances1 or dur+ angel visits1 few & f> betwe51 t he c see ^? div9e =ms :i* x is 8 bus9ess to portray4 ,he mu/ !re=e quit 8 home & seek = ! models ( anci5t & mod]n art4 ,9 ! ,briti% ,museum1 9 ! ,l\vre1 9 ! ,vatican1 & 9 ! repositories ( art 9 ,b]l91 ,muni*1 & o!r ,european cities1 he mu/ sp5d mon?s & ye>s 9 ! /udy ( 8 pr(ession4 ,he mu/ copy1 day aft] day1 ^? ma/] triumphs ( g5ius :i* ! ta/e ( ages has consecrat$1 & ga!r f _! /udy ! true pr9ciples ( 8 art4 ,transf]r$ to 8 own /udio1 ^! copies w be 8 in/ructor & 8 guide4 ,!y w exhibit to him =ms m ?an human1 ?\gh human /ill1 embody+ all t is true & beautiful 9 :at might be man4 ,! value ( ^! copies1 h[ev]1 dep5ds on ! skill & c>e ) :i* !y h be5 tak52 b no lab\r h[ev] great1 & no p[] ( draw+ h[ev] ma/]ly1 c give ev5 an approximate idea ei!r ( ! outl9e or r\nd ( solid figures1 :e!r s+le or 9 gr\ps4 ,light & %ade c alone evolve ^? muscul> prom95ces1 or ^? s(t & sph]e-l relievos :i* give su* p[] & beauty to =ms1 male & female2 b h[ c an arti/ cat* & fix ^? lights & %ades :i* give relief to ! p>ts :i* !y illum9ate or obscure8 ,! light ( ! sun1 ev5 9 a cl\dless sky1 is ev] v>y+ 9 int5sity1 & ! bread? & direction ( ! %ad[s :i* he ca/s are v>y+ f h\r to h\r4 ,9 a cl\dy day1 ! motion ( ! cl\ds1 & ! v>y+ reflexions )9 8 ap>tm5t1 subject ! lights & %ad[s to con/ant *ange4 ,! portions ( ! draw+ execut$ 9 ! morn+ w n h>monize ) :at is drawn at noon1 or dur+ ! decl9e ( day4 ,we consid] x1 !re=e1 impossible to execute a draw+ ( a /atue1 or ( a gr\p ( /atues1 f :i* ! arti/ c h any?+ l an accurate idea ( ! =ms :i* compose !m4 ,f all ^! difficulties ! sculptor has be5 reliev$ by ! inv5tion ( ! photographic process4 ,he may ?us take copies ( /atues 9 a few m9utes1 & take !m 9 all _! aspects1 & z se5 at v>i\s di/ances1 & 9 ?is mann] he w obta9 draw+s ) ! %ad[s z !y exi/$ at a p>ticul> in/ant1 s t ! lights & %ades1 ^u e individual "p ( ! /atue1 w be correctly relat$ to ea* o!r4 ,b valuable z ^! draw+s are1 comp>$ ) ^? execut$ by ! p5cil1 _! value becomes t5fold great] :5 !y are tak5 ) ! b9ocul> cam]a1 & ) small l5ses1 z already describ$4 ,:5 comb9$ 9 ! /]eoscope1 he may reproduce ! /atue 9 relief1 9 all its aspects1 & ( diff]5t sizes1 & d]ive f its /udy ! same advantages :i* ! /atue itself w\ld h furni%$4 ,9 "o respect ! creations ( ! /]eoscope surpass ! orig9al4 ,:ile ! arti/ is survey+ & draw+ in/ruction f ! m>ble prototype1 its lights & %ad[s1 & consequ5tly ! delicate =ms1 convex & concave1 by :i* !y are produc$1 are con/antly *ang+1 :]eas1 9 ! /]eoscopic /atue1 ev]y?+ is fix$ & inv>iable4#fc ,9 tak+ bu/s & /atues f ! liv+ subject1 ! sculptor w d]ive great advantage f ! /]eoscope4 ,d\ble pictures ( ! :ole1 or ( any portion ( ! subject1 may be tak5 & rais$ into relief1 & f su* b9ocul> pictures1 execut$ on "o side ( ! globe1 an arti/1 on ! o!r side1 may complete an admirable /atue4 ,! dy+ & ! dead may ?us be modell$ )\t ! rude contact ( a mask1 & ^? noble =ms p]petuat$ :i* affection or gratitude has ende>$4 #fc ,a ,fr5* sculptor has actually modell$ a /atue f ! /]eoscopic relief ( b9ocul> pictures4 ,we mu/ w>n ! sculptor1 h[ev]1 aga9/ ! employm5t ( b9ocul> pictures tak5 ) l>ge l5ses4 ,n only w ! individual picture be de=m$1 b a d\ble de=mity w be induc$ by _! union2 & :e!r he copies f a /atue or f a liv+ figure1 8 "w mu/ be defective1 ev5 to an ord9>y eye4 ,9 ar*itecture1 & all ^? arts 9 :i* ornam5tal =ms are giv5 to solid mat]ials1 ! b9ocul> cam]a & ! /]eoscope w be f\nd indisp5sable4 ,! c>v+s ( anci5t1 or m$ival1 or mod]n art may be copi$ & reproduc$ 9 relief1 :atev] be ! mat]ial f :i* !y h be5 cut4 ,! ri* =ms ( ,go?ic ar*itecture1 & ! m classical productions ( ,greek & ,roman g5ius1 w swell ! arti/'s portfolio1 & possess all ! value ( ca/s4 ,) ! aid ( ! ,kaleidoscope ! mod]n arti/ may surpass all 8 pr$ecessors4 ,he may create an inf9ite v>iety ( ^? =ms ( symmetry :i* ent] s l>gely into ! decorative arts2 & if ! individual =ms1 :i* con/itute ! symmetrical picture1 are !mselves solid1 ! b9ocul>-kaleidoscopic pictures1 tak5 photographically1 w be rais$ into ! orig9al relief ( _! compon5t p>ts1 or !y may be repres5t$ directly to ! eye 9 relief1 by semi-l5ses plac$ at ! ocul> extremities ( ! reflect+ plates4#fd ,if ! symmetrical =ms are tak5 f l9es 9 ! same plane1 no relief w be obta9$ f ! kaleidoscopic pictures4 #fd ,see my ,treatise on ! ,kaleidoscope1 second edition1 j publi%$4 ,b x is n m]ely to ! decorative p>ts ( ar*itecture t ! /]eoscope is applicable4 ,! noble/ edifices1 :e!r ( a civil1 a religi\s1 or a milit>y "*1 :i* he c\ld o!rwise /udy only z a travell]1 & repres5t 9 hurri$ & imp]fect sket*es1 w1 :5 tak5 b9ocul>ly1 /& be=e him 9 _! full relief & gr&eur1 reflect+ to 8 eye ! v lights & %ad[s :i* at a giv5 h\r ! sun ca/ ^u _! walls4 ,9 ! erection ( public build+s1 h\rly or daily photographs h be5 tak5 ( !m1 to %ew to ! abs5t sup]9t5d5t ! progress ( 8 "w2 b ^! pictures w be /ill m expressive if b9ocul> ones are comb9$ 9 ! /]eoscope4 ,to ! eng9e] & ! me*ani/1 & ! mak]s ( in/rum5ts ( all k9ds1 ! /]eoscope w be ( ine/imable value4 ,! difficulty ( repres5t+ ma*9]y is s great t x is n easy to und]/& its con/ruction or its mode ( op]ation f plans & p]spective views ( x4 ,! union ( "o or two b9ocul> pictures ( x1 :5 ?r[n into relief1 w1 9 _m cases1 remove ! difficulty bo? ( draw+ & und]/&+ x4 ,photographs ( ma*9]y1 h[ev]1 consi/+ ( a numb] ( m9ute p>ts at diff]5t di/ances f ! eye1 h1 :5 tak5 by l>ge l5ses1 all ! defects :i* we expla9$ 9 ref]5ce to trees & _! bran*es & leaves4 ,supports & axles w be transp>5t1 & ! tee? ( ! :eels1 & ! small & di/ant p>ts ( ! me*anism1 w be se5 ?r\gh all ! ne>] p>ts ^: wid? is less ?an ! diamet] ( ! l5s4 ,9 tak+ a b9ocul> picture ( a ma*9e or in/rum5t consi/+ ( v>i\s p>ts1 t m9ute accuracy :i* is necess>y to give ! true =m & expression ( ! human face is n requir$2 b if x %\ld happ5 t1 9 a correct b9ocul> view ( ! object1 p>ts are conceal$ :i* x w\ld be useful to see1 we mu/ discov] ! b9ocul> angle :i* w %ew ^! p>ts 9 ! two pictures1 or1 g5]ally speak+1 :i* w give ! be/ view ( ! me*anism1 & !n adju/ ! l5ses ( ! cam]a to give ! desir$ repres5tations ( x4 ,^! obs]vations w be f\nd useful 9 obta9+ /]eoscopic views ( ! /ructures 9 c>p5try & %ip-build+4 ,,*apt] ,,xii4 ,,application ,,( ,,! ,,/]eoscope ,,to ,,natural ,,hi/ory4 ,9 treat+ ( ^? objects ( natural hi/ory :i* ent] into ! composition ( l&scape sc5]y1 su* z trees1 plants1 & rocks1 we h po9t$ out ! me?od ( hav+ !m accurately drawn = ! /]eoscope2 b x is to ! importance ( /]eoscopic photography 9 natural hi/ory z a sci5ce t we propose to devote ! pres5t ,*apt]4 ,:5 we reflect ^u ! va/ numb] ( species :i* h be5 describ$ by zoologi/s1 ! noble =ms ( animat$ nature1 :e!r wild or dome/icat$1 & ! valuable s]vices :i* _m ( !m p]=m z ! slaves ( man1 we c h>dly atta* too mu* importance to ! advantage ( hav+ !m accurately del9eat$ & rais$ into /]eoscopic relief4 ,! animal pa9t]s ( ! pres5t day1--! ,l&se]s1 ! ,c[p]s1 & ! ,ansdells1 h br\ght ?is bran* ( _! art to a high degree ( p]fection1 b ! subjects ( _! p5cil h be5 pr9cipally dogs1 horses1 de]1 & cattle1 & a few o!r animals1 ) :i* !y are well acqua9t$1 & specim5s ( :i* 7 )9 _! rea*4 ,to give accurate repres5tations ( giraffes1 hynas1 & ! r>] animals :i* are f\nd alive only 9 zoological g>d5s & travell+ c>avans1 is a m difficult task1 & "o :i* has be5 necess>ily intru/$ to inf]ior h&s4 ,9 ?is bran* ( 8 art ! photograph] is p]plex$ ) ! difficulty ( arre/+ 8 subject 9 a position ( repose & 9 ! attitude :i* he requires4 ,b ?is difficulty w dim9i% z 8 mat]ials become m s5sitive to light2 & means may be f\nd = fix+1 )\t con/ra9t1 c]ta9 animals 9 ! desir$ position4 ,we h se5 ! portrait ( a dog tak5 ) su* m9ute accuracy t ! slighte/ trace ( any motion c\ld n be p]ceiv$4 ,its ma/] direct$ 8 att5tion to a piece ( bread1 & he /ood firmly wait+ = 8 rew>d4 ,consid]+ tru? z an ess5tial elem5t 9 all photographs1 we are unwill+ to c\nsel ! arti/ to h rec\rse to a l>ge l5s = ! purpose ( accel]at+ 8 process by seiz+ 8 re/less object 9 a s+le in/ant ( "t2 b :at _c be tol]at$ 9 ! human =m may be p]mitt$ 9 animal portraiture z a necess>y evil4 ,! div9e l9eam5ts & delicate =ms :i* 9 man ! intellect & ! affections conspire to m\ld1 are conceal$ "u ! %aggy drap]y ( ! _w ( in/9ct2 & ev5 if !y exi/$ & 7 p]ceiv$1 c\ld h>dly be appreciat$ by ^? :o h n /udi$ its mann]s & submitt$ to its laws4 ,b ev5 9 ! pres5t /ate ( photography su* a cel]ity ( process has be5 atta9$ t a di/+ui%$ amateur 9 ,ed9burgh has con/ruct$ a portable cam]a1 :i*1 by pull+ a trigg]1 in/antane\sly records ^u its s5sitive ret9a ! surf :i* is hurry+ to ! %ore1 or ! /rang] :o is pass+ 9 ! /reet4 ,) su* an in/rum5t1 9 su* h&s1 ! d5iz5s ( ! jungle or ( ! pla9s may be tak5 captive 9 _! f9e/ attitudes & 9 _! mo/ re/less moods4 ,photographs ?us obta9$ w possess a value ( no ord9>y k9d1 & :5 tak5 9 ! b9ocul> cam]a & rais$ into relief by ! /]eoscope1 w be valuable auxili>ies to ! naturali/1 & ev5 to ! pa9t]s & ! poets ^: works or ^: lyrics may require an introduction to ! brutes t p]i%4 ,9 repres5t+ ) accuracy ! o/eology & integum5ts ( ! zoological _w--! framework :i* protects life1 & to :i* life gives activity & p[]1 ! aid ( ! /]eoscope is indisp5sable4 ,! repose ( dea?1 & ! %>p p5cil :i* resides 9 ! small l5s1 w place be=e ! /ud5t's eye ! skeleton1 clo!d or unclo!d1 9 accurate p]spective & true relief1 :ile he contemplates ) wond]1 9 _! true app>5t magnitude1 ! gigantic ,ma/odon1 ! colossal ,mega!rion1 & ! huge ,d9ornis1 or exam9es ! cru%$ rema9s ( ! l5g!n$ ,saurian1 or ! holl[ foot/eps :i* anci5t life has impress$ on ! massive s&/one or ! indurat$ clay4 ,9 ! o!r bran*es ( natural hi/ory1 i*?yology1 orni?ology1 con*ology1 c41 ! /]eoscope w be f\nd equally useful4 ,9 entomology1 :]e insects are to be repres5t$1 ! microscopic b9ocul> cam]a mu/ be us$2 & 9 ord] to prev5t ! legs1 ! ant5n1 & o!r small p>ts ( ! object f be+ transp>5t1 & !re=e spott$1 ) ! images ( objects or p>ts beyond !m1 z expla9$ 9 a prec$+ *apt]1 ! smalle/ l5ses %\ld be employ$4 ,! roots & bulbs :i* are rais$ by ! agriculturi/ & ! horticulturi/1 ! turnip1 ! beet1 ! c>rot1 & ! onion2 & ! fruits rais$ 9 ! or*>d1 on ! wall1 or 9 ! ho?\se1 may be exhibit$ 9 all _! r\ndness & solidity 9 ! /]eoscope2 & z articles ( comm]ce !y might be pur*as$ on ! au?ority ( _! pictures 9 relief4 ,! microscopic /]eoscope w1 9 l mann]1 give accurate magnifi$ repres5tations 9 relief ( gra9s & se$s ( all k9ds1 & by comp>+ ^! ) ! repres5tations ( ^? ( a /&>d =m & quality1 ! pur*as] may be enabl$ to =m a bett] idea ( _! excell5ce ?an if he saw !m ) 8 own eyes1 or _h !m 9 8 own h&s4 ,,*apt] ,,xiii4 ,,application ,,( ,,! ,,/]eoscope ,,to ,,educational ,,purposes4 ,! obs]vations conta9$ 9 ! prec$+ *apt]s prep>e u = appreciat+ ! value ( ! /]eoscope z an indisp5sable auxili>y 9 elem5t>y z well z 9 pr(essional education4 ,:5 ! s*ol> has le>n$ to read1 to write1 & to c\nt1 he has obta9$ only ! tools ( in/ruction4 ,to acquire a g5]al k ( ! works ( ,god & ( man--( ?+s common & uncommon--( ! miracles ( nature & ( art1 is ! fir/ /ep 9 ! education ( ! p4 ,)\t su* k1 ! humble/ ( our race is unfit = any place 9 ! social scale4 ,he may h le>n$ to read 8 ,bible1 & he may h read x aft] he _h le>n$ to read2--he may h committ$ to memory e s5t5ce 9 ! ,decalogue2--he may h pack$ into ! /oreh\se ( 8 bra9 all ! wisdom ( ,solomon1 & all ! div9e precepts ( a great] ?an ,solomon1 :ile he is utt]ly ignorant ( ev]y?+ above him1 ar\nd him1 & )9 him1--ignorant1 too1 ( ! =m1 ! magnitude1 & ! motions ( 8 t]re/rial home1--ignorant ( ! gigantic /ructures :i* con/itute ! mat]ial univ]se1--ignorant ( ! fabrics :i* indu/ry prep>es = 8 use1 & ( ! luxuries :i* comm]ce br+s f ! ends ( ! e>? & places at 8 door1--ignorant ev5 ( ! wond]ful op]ations ( t b5efic5t commiss>iat1 :i* is e mom5t1 :ile he sleeps & dreams1 elaborat+ ! mat]ials by :i* he is f$ & clo!d4 ,7 we to say1 ?\gh we d n say x1 t 9 our own c\ntry ! tea*]s1 s p5uri\sly end[$ by ! ,/ate1 are n mu* 9 advance ( _! pupils1 we %\ld err only 9 /at+ :at is n univ]sally true2 & yet !re are m5 ( influ5ce & "* insi/+ ^u ! imposition ( sect>ian te/s1 & ?us b>ricad+ our s*ools aga9/ ! admission ( ! wise/ & ! fitte/ ma/]s6 ,& :ile e civiliz$ community 9 ! _w is eag]ly tea*+ _! p1 irrespective ( religi\s cre$s1 ! same bigots1 civil & ecclesia/ical1 9 our own c\ntry1 h comb9$ to resi/ ! only sy/em ( education :i* c /em ! tide ( vice & crime :i* is desolat+ ! l&4 ,mission>y lab\r & re=matory in/itutions1 valuable z !y are1 presuppose an educat$ community4 ,to in/ruct & re=m a race t c nei!r read _! ,bible nor d]ive k f books1 is a task beyond human a*ievem5t4 ,! de>e/ int]e/s ( society1 !re=e1 call l\dly = ,secul> ,education1--! greate/ boon :i* philan?ropy ev] dem&$ f ! ,/ate4 ,! m9i/] :o1 9 ! face ( sect>ian factions1 d>es n id5tify himself ) a l>ge legislative measure = ! education ( ! p1 & resigns (fice :5 he fails to c>ry x1 pref]s p[] to duty1 &1 if he ev] possess$ x1 dive/s himself ( ! "* ( a /atesman & a patriot4 ,he may be ju/ifi$ 9 puni%+ ! law-break] :o _c read 8 /atutes1 b he is himself ! break] ( laws ( a high] ord]1 & sanction$ by a high] tribunal4 ,if ! education ( ! p is to be attempt$ ei!r by p>tial or compreh5sive legislation1 ! exi/+ sy/em is utt]ly ineffici5t4 ,! tea*]1 h[ev] wisely *os5 & well qualifi$1 has n at 8 comm& ! means ( imp>t+ k4 ,he may p\r x 9 by ! e>1 or extract x f ! pr9t$ page1 or exhibit x 9 c>icature 9 ! mis]able embelli%m5ts ( ! s*ool-book1 b unless he tea*es ?r\gh ! eye1 ! great in/rum5t ( k1 by means ( tru?ful pictures1 or in/rum5ts1 or models1 or by ! direct exhibition ( ! products ( nature & ( art1 :i* c be submitt$ to ! scrut9y ( ! s5ses1 no satisfactory in/ruction c be convey$4#fe ,e s*ool1 inde$1 %\ld h a museum1 h[ev] limit$ & humble4 ,ev5 f )9 its n>r[ sph]e objects ( natural hi/ory & antiquities might be collect$1 & duplicates ex*ang$2 & we are sure t _m a *imney-piece 9 ! di/rict w\ld surr5d] a ti! ( its curiosities = ! public use4 ,7 ! ,briti% ,museum1 & o!r ov]fl[+ collections1 to di/ribute among prov9cial museums ! num]\s duplicates :i* !y possess1 !y w\ld gradually pass into ! s*ools1 & be=e a qu>t] ( a c5tury elaps$1 museums w\ld be f\nd 9 e prop] locality4 #fe 8,! importance ( e/abli%+ a p]man5t ,museum ( ,education 9 ?is c\ntry1 ) ! view ( introduc+ improvem5ts 9 ! exi/+ me?ods ( in/ruction1 & specially direct+ public att5tion 9 a practical mann] to ! "q ( ,national ,education1 has be5 ( late g5]ally recognis$40--,?ird ,report ( ! ,commission]s = ! ,exhibition ( #ahea1 pres5t$ to bo? ,h\ses ( ,p>liam5t1 p4 #cg4 ,lond41 #ahef4 ,z we _c indulge 9 ! hope t any su* boon w be conf]r$ on our educational in/itutions1 x becomes an important "q h[ f> x is possible to supply ! defect by ! means )9 our rea*4 ,! photographic process may be advantage\sly employ$ 9 produc+ accurate repres5tations ( ^? objects1 bo? ( nature & ( art1 :i* x w\ld be desirable to describe & expla9 9 ! in/ruction ( y\?2 b z exp]i5ce has n yet taught u t su* pictures w be p]man5t1 & capable ( resi/+ ! action ( "t & ! elem5ts1 x w\ld be haz>d\s to employ !m 9 ! illu/ration ( popul> works4 ,x is =tunate1 h[ev]1 t ! new art ( galvanography enables u1 by a *eap process1 to give to photographs ! p]man5ce ( engrav+s1 & to employ !m 9 ! illu/ration ( educational works4#ff #ff ,?is f9e inv5tion we owe to ,mr4 ,paul ,prets*1 late director ( ! ,imp]ial ,pr9t+ ,(fice at ,vi5na4 ,x is secur$ by pat5t1 & is n[ 9 practical op]ation 9 ,holl[ay ,place1 ,isl+ton4 ,b h[ev] mu* we may value su* an auxili>y1 repres5tations or draw+s1 on a plane1 ( solids or comb9ations ( solids at diff]5t di/ances f ! eye1 are 9 _m cases un9telligible ev5 to p]sons well in=m$2 s t1 on ?is gr\nd alone1 we _c b appreciate ! advantages to be d]iv$ f b9ocul> pictures & _! /]eoscopic relievo1 n only 9 ! in/ruction ( y\?1 b 9 ! diffusion ( k among all ranks ( society4 ,"o ( ! mo/ palpable advantages to be d]iv$ f ! illu/ration ( s*ool-books by pictures 9 relief1 is ! communication ( correct k ( ! v>i\s objects ( natural hi/ory4 ,if1 z we h already %ewn1 ! naturali/ d]ives important assi/ance 9 8 /udies f correct repres5tations ( animat$ nature1 h[ mu* m valuable mu/ !y be to ! s*ol> :o nev] saw1 & may nev] see ! objects !mselves4 ,9 ! dep>tm5t ( zoology1 ! picture might frequ5tly be tak5 f ! liv+ animal1 /&+ be=e ! cam]a 9 vigor\s life & transc5d5t beauty2 or :5 ?is _c be done1 f ! f9e specim5s ( zoological =ms :i* adorn our metropolitan & prov9cial museums4 ,! trees & plants1 too1 ( di/ant zones1 :e!r nak$ 9 _! o/eology1 or luxuri\s 9 _! foliage1 w\ld %ew !mselves 9 full relief2--! banyan1 cl++ ) its hundr$ roots to ! gr\nd1--! bread-fruit tree1 ) its b5efic5t burd51--! c[ tree1 ) its :olesome bev]age1--! ca\t*\c tree1 yield+ its valuable juice1--or ! deadly upas1 prep>+ its poison = ! arr[ ( ! savage or ! poni>d ( ! assass94 ,) no less int]e/ w ! s*oolboy gaze on ! =ms ( insect life1 :i* w almo/ flutt] be=e him1 & on ! t5ants ( ! air & ( ! ocean1 defective only 9 ! col\rs :i* adorn !m4 ,! /ructures ( ! inorganic _w w equally comm& 8 admiration4 ,! m9]als :i* h gr[n 9 ! e>? b5ea? 8 feet1 & ! cry/als :i* *emi/ry has conjur$ into be+1 w display to him _! geometric =ms1 inf9ite 9 v>iety1 & int]e/+ f _! r>ity & value4 ,pa9t$ by ! v light :i* /ream$ f !m1 he w see1 9 _! retir+ & advanc+ facets1 ! ,koh9oor & o!r diamonds1 & ! huge rubies1 & sapphires1 & em]alds1 :i* h adorn$ ! *aplet ( beauty1 or sp>kl$ 9 ! diadem ( k+s4 ,! gigantic productions ( ! e>? w appeal to him ) equal p[]1--! colossal granites1 :i* h travell$ 9 *>iots ( ice1 & ! r\nd$ b\ld]s1 :i* h be5 transport$ 9 torr5ts ( mud2 & :ile he admires1 9 _! /rong relief1 ! precipices ( anci5t lava--! ,doric colonnades ( basalt--! upheav$ & contort$ /rata beside !m1 & ! undi/urb$ b$s :i* no int]nal convulsions h %ak51 he w /& appall$ be=e ! fossil giants ( ! primeval _w t trod ! e>? dur+ its prep>ation = man1 & h be5 embalm$ 9 /one to in/ruct & to humble him4 ,9 acquir+ a k ( physical geography1 9 :i* ! gr&] aspects ( nature arre/ our att5tion1 _! /]eoscopic repres5tations w be p>ticul>ly in/ructive4 ,! m\nta9 range1 :e!r abrupt 9 its elevation1 or retir+ f our view1--:e!r sc>r$ ) peaks or undulat+ 9 outl9e1--! insulat$ m\nta9 tipp$ ) sn[ or gl[+ ) fire1--! volcano eject+ its burn+ missiles1#fg--! iceb]g fix$ 9 ! %ore1 or float+ on ! deep1--! deaf5+ cat>act1--! glaci] & its mora9es1 s9k+ g5tly to ! pla9s1--& ev5 ! colossal wave ) its foam+ cre/1 w be portray$ 9 ! b9ocul> cam]a1 & exhibit$ 9 all ! gr&eur & life ( nature4 #fg ,an accompli%$ travell]1 ! ,rev4 ,mr4 ,bridges1 :o asc5d$ ,m\nt ,etna = ! purpose ( tak+ ,talbotype draw+s ( its sc5]y1 plac$ 8 cam]a on ! edge ( ! crat] to obta9 a repres5tation ( x4 ,no soon] 0 ! cam]a fix$ & ! s5sitive pap] introduc$1 ?an an eruption took place1 :i* =c$ ,mr4 ,bridges to quit 8 cam]a 9 ord] to save 8 life4 ,:5 ! eruption clos$1 he return$ to collect ! fragm5ts ( 8 in/rum5t1 :51 to 8 great surprise & delight1 he f\nd t 8 cam]a 0 n only un9jur$1 b conta9$ a picture ( ! crat] & its eruption4 ,! works ( human h&s1--! /ructures ( civilisation1 w /& be=e ! hi/orian & ! antiqu>y1 z well z ! /ud5t1 9 _! pri/9e solidity1 or 9 _! ru9$ gr&eur1--! monum5ts by :i* sov]eigns & nations h s\ght to p]petuate _! names1--! gorge\s palaces ( k+s1--! g>i% temples ( sup]/ition1--! humbl] edifices ( ,*ri/ian fai?1--! ba/ions & /rongholds ( w>1 w display !mselves 9 ! /]eoscope z if ! obs]v] 7 plac$ at _! base1 & w>m$ by ! v sun :i* %one ^u _! walls4 ,al?\gh few ( our village y\? may become sculptors1 yet ! exhibition ( anci5t /atues 9 _! actual relief1 & real app>5t magnitude1 _c fail to give !m salut>y in/ruction & rational pleasure4 ,to gaze ^u ! ,apollo ,belvid]e1--! ,v5us de ,m$ici1--! ,laocoon1 & ! o!r ma/]pieces ( anci5t art1 /&+ 9 ! v halls :i* !y n[ occupy2 or to see ! *ef d'uvres ( ,canova1 ,?orvalds51 & ,*antrey1 or ! productions ( liv+ arti/s 9 _! own /udio1 ) ! sculptor himself /&+ by _! side1 w excite an int]e/ ( no ord9>y k9d4 ,f ! works ( ! ar*itect1 ! eng9e]1 & ! me*ani/1 z exhibit$ 9 full relief1 ! /ud5t1 :e!r at our s*ools or colleges1 w d]ive ! mo/ valuable in/ruction4 ,! gigantic aqu$ucts ( anci5t & mod]n times1--! viaducts & bridges :i* span our valleys & our riv]s1 & ! ma*9]y 9 our ars5als1 factories1 & work%ops1 w be objects ( deep int]e/ to ! g5]al z well z ! pr(essional inquir]4 ,!re is yet ano!r application ( ! /]eoscope to educational purposes1 n less important ?an ^? :i* h be5 m5tion$4 ,9 ! production ( diagram repres5t+ in/rum5ts & app>atus1 :i* _c be und]/ood f draw+s ( !m on a plane1 x w be ( incalculable use to ! tea*] to h /]eoscopic pictures ( !m4 ,9 e bran* ( physical sci5ce1 diagrams ( ?is k9d are requir$4 ,:5 !y are int5d$ to repres5t app>atus & in/rum5ts1 ei!r = illu/rat+ kn[n tru?s1 or c>ry+ on physical rese>*es1 b9ocul> pictures c be easily obta9$2 b :5 ! diagrams h n be5 tak5 f app>atus1 b are m]ely comb9ations ( l9es1 we c obta9 b9ocul> photographs ( !m only f models con/ruct$ on purpose4 ,^! models w give b9ocul> repres5tations 9 v>i\s azimu?s1 s t ! true position ( planes at diff]5t incl9ations1 & l9es at v>i\s angles ) ea* o!r1 & at diff]5t di/ances f ! eye1 w be readily appreh5d$4 ,a/ronomical diagrams1 9 :i* orbits1 c41 may be repres5t$ by wires1 & optical figures1 9 :i* ! rays may be =m$ by ?reads or wires1 w\ld be ?us easily execut$4 ,among ! b9ocul> diagrams1 consi/+ ( :ite l9es ^u a black gr\nd1 :i* h be5 execut$ 9 ,p>is1 !re is "o repres5t+ ! app>atus 9 :i* a ray ( light1 pol>iz$ by reflexion f a glass plate1 passes ?r\gh a cry/alliz$ film p]p5dicul> to ! plane ( ! pap]1 & is subsequ5tly analys$ by reflexion f ano!r plate at "r angle to ! foll[+ plate4 ,?is diagram1 :5 plac$ 9 relief by ! /]eoscope1 gives z correct an idea ( ! process z ! app>atus itself4 ,z an auxili>y 9 ! inve/igation ( que/ions ( difficulty & importance1 bo? 9 physics & metaphysics1 ! /]eoscope is peculi>ly valuable4 ,x enables u to place 9 its true light ! celebrat$ !ory ( vision on :i* ,bi%op ,b]keley re>$ ! ideal philosophy1 ( :i* he 0 ! f\nd]1 & x gives u p[]ful aid 9 expla9+ _m physical ph5om5a :i* h long baffl$ ! +5uity ( philosoph]s4 ,x w\ld be out ( place to give any acc\nt ( ^! 9 a "w l ?is1 b !re is "o s rem>kable1 & at ! same "t s in/ructive1 z to m]it special notice4 ,9 ord] to exhibit1 by means ( ?ree diagrams1 a solid 9 relief & holl[ at ! same "t1 :i* _h n be5 previ\sly done1 ,i execut$ ?ree draw+s ( ! fru/um ( a cone1 resembl+ ^? 9 ,fig4 #ca1 s t ! left-h& "o & ! middle "o gave ! holl[ cone1 :ile ! middle "o & ! "r-h& "o gave ! rais$ cone4 ,hav+ _! summits truncat$1 z 9 ! figure1 ! cones exhibit1 9 ! "o case1 a circle at ! bottom ( ! holl[ cone1 & 9 ! o!r1 a circle on ! summit ( ! rais$ cone4 ,:5 ^! ?ree diagrams#fh are plac$ 9 an op5 l5ticul> /]eoscope1 or are unit$ by ! conv]g5cy ( ! optical axes1 s t we c n only see ! holl[ & ! rais$ cones1 b ! flat draw+ on ea* side ( !m1 we are enabl$ to give an ocul> & exp]im5tal pro( ( ! cause ( ! l>ge size ( ! horizontal moon1 ( h] small size :5 9 ! m]idian or at a great altitude1 & ( h] int]m$iate app>5t magnitude at int]m$iate altitudes1--ph5om5a :i* _h long p]plex$ a/ronom]s1 & :i* ,dr4 ,b]keley1 reject+ previ\s & well-f\nd$ explanations1 ascrib$ to ! diff]5t degrees ( brightness ( ! moon 9 ^! diff]5t positions4 #fh ,a b9ocul> slide1 copi$ f ! "o orig9ally design$ by myself1 =ms ,no4 #bg ( ! ,s]ies ( :ite-l9$ diagrams ^u a black gr\nd execut$ 9 ,p>is4 ,! draw+s1 h[ev]1 are too l>ge = ! common /]eoscope4 ,z ! circul> summit ( ! rais$ cone appe>s to be ne>e/ ! eye ( ! obs]v]1 ! summit ( ! holl[ cone f>!/ (f1 & ! simil> c5tral circle 9 ! flat draw+ on ea* side1 at an int]m$iate di/ance1 ! app>5t di/ances f ! eye ( diff]5t & equal circles w repres5t ! app>5t di/ance ( ! moon 9 ! z5i?1 or v high 9 ! elliptical cele/ial vault1--! same di/ance :5 %e is 9 ! horizon1 & ! same :5 at an int]m$iate altitude4 ,be+ 9 reality ( exactly ! same size1 & at ! same di/ance f ! eye1 ^! circul> summits1 or sections ( ! cone1 are precisely 9 ! same circum/ances z ! moon 9 ! ?ree positions already m5tion$4 ,if we n[ contemplate !m 9 ! l5ticul> /]eoscope1 we %all see ! circul> summit ( ! holl[ cone ! l>ge/1 l ! horizontal moon1 because x seems to be at ! greate/ di/ance f ! eye1--! circul> summit ( ! rais$ cone ! smalle/1 because x appe>s at ! lea/ di/ance1 l ! z5i? or culm9at+ moon1--& ! circul> summits ( ! flat cones on ea* side1 ( an int]m$iate size1 l ! moon at an int]m$iate altitude1 because _! di/ance f ! eye is int]m$iate4 ,! same effect w be equally well se5 by plac+ ?ree small waf]s ( ! same size & col\r on ! squ>e summits ( ! draw+s ( ! quadrangul> pyramids1 or m simply1 by obs]v+ ! l>g] size ( ! squ>e summit ( ! holl[ pyramid4 ,?is explanation ( ! cause ( ! increas$ size ( ! horizontal moon is rigor\sly correct4 ,if any p]son %\ld suspect t ! circles :i* repres5t ! moon are unequal 9 size1 or are at diff]5t di/ances f ! eye1 !y h only to cut ! diagram into ?ree p>ts1 & make ea* draw+ ( ! fru/um ( ! cone occupy a diff]5t place 9 ! b9ocul> slide1 & !y w obta9 ! v same results4 ,h5ce we place beyond a d\bt ! incorrectness ( ,dr4 ,b]keley's !ory ( ! size ( ! horizontal moon1--a !ory to :i* ! /]eoscope enables u to apply ano!r te/1 = if we make "o or m ( ^! circles less bright ?an ! re/1 no *ange :atev] w be produc$ 9 _! app>5t magnitude4 ,,*apt] ,,xiv4 ,,application ,,( ,,! ,,/]eoscope ,,to ,,purposes ,,( ,,amusem5t4 ,e exp]im5t 9 sci5ce1 & e in/rum5t dep5d+ on sci5tific pr9ciples1 :5 employ$ = ! purpose ( amusem5t1 mu/ necess>ily be in/ructive4 8,philosophy 9 sport0 nev] fails to become 8,sci5ce 9 e>ne/40 ,! toy :i* amuses ! *ild w in/ruct ! sage1 & _m an em95t discov]] & inv5tor c trace ! pursuits :i* immortalize !m to "s exp]im5t or in/rum5t :i* amus$ !m at s*ool4 ,! soap bubble1 ! kite1 ! balloon1 ! wat] :eel1 ! sun-dial1 ! burn+-glass1 ! magnet1 c41 h all be5 valuable inc5tives to ! /udy ( ! sci5ces4 ,9 a li/ ( ab\t #aej b9ocul> pictures issu$ by ! ,london ,/]eoscopic ,company1 "u ! title ( 8,miscellane\s ,subjects ( ! #8,wilkie' "*10 !re are _m ( an amus+ k9d1 9 :i* sc5es 9 common life are admirably repres5t$4 ,foll[+ out ! same idea1 ! mo/ int]e/+ sc5es 9 our be/ com$ies & trag$ies might be repres5t$ ) ! same di/9ctness & relief z if ! actors 7 on ! /age4 ,ev5ts & sc5es 9 anci5t & mod]n hi/ory might be simil>ly exhibit$1 & 9 our day1 b9ocul> pictures ( trials1 congresses1 political1 legislative1 & religi\s assemblies1 9 :i* ! lead+ actors 7 repres5t$1 might be provid$ = ! /]eoscope4 ,= ! purpose ( amusem5t1 ! photograph] might c>ry u ev5 into ! regions ( ! sup]natural4 ,8 art1 z ,i h else:]e %ewn1 enables him to give a spiritual appe>ance to "o or m ( 8 figures1 & to exhibit !m z 8?9 air0 amid ! solid realities ( ! /]eoscopic picture4 ,:ile a p>ty is engag$ ) _! :i/ or _! gossip1 a female figure appe>s 9 ! mid/ ( !m ) all ! attributes ( ! sup]natural4 ,h] =m is transp>5t1 e object or p]son beyond h] be+ se5 9 %ad[y b di/9ct outl9e4 ,%e may occupy m ?an "o place 9 ! sc5e1 & diff]5t portions ( ! gr\p might be made to gaze ^u "o or o!r ( ! visions be=e !m4 ,9 ord] to produce su* a sc5e1 ! p>ties :i* are to compose ! gr\p mu/ h _! portraits ne>ly f9i%$ 9 ! b9ocul> cam]a1 9 ! attitude :i* !y may be suppos$ to take1 & ) ! expression :i* !y may be suppos$ to assume1 if ! vision 7 real4 ,:5 ! p>ty h ne>ly sat ! prop] l5g? ( "t1 ! female figure1 suitably attir$1 walks quickly into ! place assign$ h]1 & aft] /&+ a few seconds 9 ! prop] attitude1 retires quickly1 or takes z quickly1 a second or ev5 a ?ird place 9 ! picture if x is requir$1 9 ea* ( :i* %e rema9s a few seconds1 s t h] picture 9 ^! diff]5t positions may be tak5 ) suffici5t di/9ctness 9 ! negative photograph4 ,if ?is op]ation has be5 well p]=m$1 all ! objects imm$iately beh9d ! female figure1 hav+ be51 previ\s to h] introduction1 impress$ ^u ! negative surface1 w be se5 ?r\gh h]1 & %e w h ! appe>ance ( an a]ial p]sonage1 unlike ! o!r figures 9 ! picture4 ,?is exp]im5t may be v>i$ 9 _m ways4 ,"o body may be plac$ )9 ano!r1 a *ick51 = example1 )9 an egg1 & s+ul> effects produc$ by comb9+ plane pictures ) solid bodies 9 ! arrangem5t ( ! p]sons & ?+s plac$ be=e ! b9ocul> cam]a4 ,any individual 9 a gr\p may appe> m ?an once 9 ! same picture1 ei!r 9 two or m *>act]s1 & no difficulty w be exp]i5c$ by ! +5i\s photograph] 9 giv+ to ^! d\ble or triple portraits1 :5 x is requir$1 ! same appe>ance z t ( ! o!r p>ties :o h n *ang$ _! place4 ,9 gr\ps ( ?is k9d curi\s effects might be produc$ by plac+ a second b9ocul> slide betwe5 ! pr9cipal slide & ! eye1 & giv+ x a motion )9 ! /]eoscope4 ,! figures ^u x mu/ be del9eat$ photographically ^u a plate ( glass1 ?r\gh :i* ! figures on ! pr9cipal slide are se51 & ! second>y slide mu/ be s close to ! o!r t ! figures on bo? may be di/9ctly visible1 if di/9ct vision is requir$ = ^? :i* are to move4 ,ano!r me?od ( mak+ solid figures transp>5t 9 a photograph has be5 ref]r$ to 9 ! prec$+ *apt]1 & may be employ$ 9 produc+ amus+ comb9ations4 ,! transp>5cy is1 9 ?is case1 produc$ by us+ a l>ge l5s1 ! m>g9 ( :i* receives ! rays :i* issue f bodies1 or p>ts ( bodies1 situat$ beh9d o!r bodies1 or p>ts ( bodies1 ^: images are giv5 9 ! photograph4 ,! body ?us r5d]$ transp>5t mu/ be less 9 sup]ficial ext5t ?an ! l5s1 & ! body se5 ?r\gh x mu/ be s f> beh9d x t rays emanat+ f x w\ld fall ^u "s "p ( ! l5s1 ! lum9osity ( ?is body on ! photograph be+ proportional to ! "p ( ! surface ( ! l5s ^u :i* ! rays fall4 ,?is w be readily und]/ood f ,figs4 #dh & #di1 & _! description1 & ! +5i\s photograph] w h no difficulty 9 produc+ v curi\s effects f ?is prop]ty ( l>ge object-glasses4 ,"o ( ! mo/ int]e/+ applications ( ! /]eoscope is 9 comb9+ b9ocul> pictures1 con/ruct$ l ! plane picture1 us$ 9 :at has be5 call$ ! cosmorama = exhibit+ dissolv+ views4 ,^! plane pictures are s con/ruct$1 t :5 we view !m by reflect$ light1 z pictures are g5]ally view$1 we see a p>ticul> sc5e1 su* z ! ,*amb] ( ,deputies 9 its ext]nal aspect2 b :5 we all[ no light to fall ^u x1 b view x by transmitt$ light1 we see ! int]ior ( ! build+ brilliantly light$ up1 & ! deputies li/5+ to ! debate4 ,9 l mann]1 ! "o picture may repres5t two armies 9 battle array1 :ile ! o!r may repres5t !m 9 action4 ,a ca!dral 9 all its ar*itectural beauty may be comb9$ ) ! same build+ 9 ! act ( be+ burn$ to ! gr\nd2 or a w9t] sc5e cov]$ ) sn[ may be conjo9$ ) a l&scape gl[+ ) ! w>m? & v]dure ( summ]4 ,9 ! cosmorama1 ! reflect$ light :i* falls ^u ! front ( ! "o picture is obta9$ by op5+ a lid simil> to t ( ! /]eoscope1 z %ewn at ,,cd1 ,fig4 #ad1 :ile ano!r lid op5+ beh9d ! picture /ops any light :i* might pass ?r\gh x1 & prev5ts ! second picture f be+ se54 ,if1 :5 ! fir/ picture is visible1 we gradually op5 ! lid beh9d x1 & close ! lid ,,cd be=e x1 x gradually disappe>s1 or dissolves1 & ! second picture gradually appe>s till ! fir/ vani%es & ! second occupies its place4 ,a great deal ( +5uity is display$ by ! ,p>isian arti/s 9 ! composition ( ^! pictures1 & ! exhibition ( !m1 ei!r 9 small portable in/rum5ts held 9 ! h&1 or plac$ on ! table1 or on a great scale1 to an audi5ce1 by means ( ! oxyg5 & hydrog5 light1 nev] fails to excite admiration4 ,! pictures ?us exhibit$1 ?\gh f9ely execut$1 h only t degree ( relief :i* ,i h call$ monocul>1 & :i* dep5ds on correct %ad+ & p]spective2 b :5 ! dissolv+ views are obta9$ f b9ocul> pictures1 & h all ! high relief giv5 !m by _! /]eoscopic comb9ation1 ! effect mu/ be s+ul>ly f9e4 ,v int]e/+ & amus+ effects are produc$ by int]*ang+ ! "r & ! left eye pictures 9 ! /]eoscope4 ,9 g5]al1 :at 0 =m]ly convex is n[ concave1 :at 0 r\nd is holl[1 & :at 0 ne> is di/ant4 ,! effect ( ?is int]*ange is f9ely se5 9 ! symmetrical diagrams1 consi/+ ( :ite l9es ^u black gr\nd1 su* z ,nos4 #a1 #e1 #i1 #ab1 #ah & #bg ( ! ,p>isian set2 b :5 ! diagrams are n symmetrical1 t is1 :5 ! "o half is n ! reflect$ image ( ! o!r1 su* z ,nos4 #bf1 c41 :i* are transp>5t polygonal solids1 =m$ z x 7 by :ite ?reads or wires1 no effect1 beyond a slight flutt]+1 is p]ceiv$4 ,z ! "r & left eye pictures are insep>able :5 on glass or silv] plate1 ! exp]im5ts mu/ be made by cutt+ 9 two ! slides on ,bri/ol bo>d4 ,?is1 h[ev]1 is unnecess>y :5 we h ! p[] ( unit+ ! two pictures by ! conv]g5cy ( ! optic axes to a ne>] po9t1 z we obta91 9 ?is case1 ! same effect z if we _h int]*ang$ ! pictures4 ,! foll[+ are "s ( ! results obta9$ 9 ?is mann] f well-kn[n slides3-- ,9 s+le portraits no effect is produc$ by ! int]*ange ( ! "r & left eye pictures4 ,if any loose "p ( ! dress is 9 ! =egr\nd x may be c>ri$ into ! di/ance1 & vice v]sa4 ,9 "o portrait1 ! end ( ! hat-b&1 :i* hung d[n loosely beh9d ! p>ty1 0 made to hang 9 front ( x4 ,9 pictures ( /reets or valleys1 & o!r objects 9 :i* ! =egr\nd is connect$ ) ! middle-gr\nd1 & ! middle-gr\nd ) ! di/ance1 )\t any break1 no effect is produc$ by ! int]*ange4 ,sometimes !re is a little bulg+ out ( ! middle di/ance1 injuri\s to ! monocul> effect4 ,9 ! b9ocul> picture ( ! ,bridge ( ,h&eck1 ! ,*alet 9 ! =egr\nd retires1 & ! middle di/ance above x advances4 ,9 ! picture ( ! sacri/y ( ,notre ,dame1 ! sacri/y retires )9 ! ca!dral4 ,9 ! ,maison des ,*apiteaux at ,pompeii1 ! picture is completely inv]t$1 ! objects 9 ! di/ance com+ into ! =egr\nd4 ,9 ! ,dagu]reotype ( ! ,cry/al ,palace1 ! wat] 9 ! =egr\nd1 ) ! float+ plants1 retires & takes an incl9$ position bel[ a horizontal plane4 ,9 ! b9ocul> picture ( ! l[] glaci] ( ,ros5laui1 ! ro( ( ! ice-cave becomes holl[1 & ! :ole =egr\nd is ?r[n into a disord]$ p]spective4 ,9 ,copel&'s ,v5us1 ! arm hold+ ! bun* ( grapes is curi\sly b5t & ?r[n beh9d ! head1 :ile ! left arm advances be=e ! *ild4 ,9 ! picture ( ! ,greek ,c\rt 9 ! ,cry/al ,palace1 ! wall beh9d ! /atues & columns advances 9 front ( !m4 ,! s+ul> fallacy 9 vision :i* ?us takes place is be/ se5 9 a picture :]e a numb] ( sep>ate articles are plac$ ^u a table1 & 9 o!r cases :]e ! judgm5t ( ! spectator is n call$ ^u to resi/ ! optical effect4 ,al?\gh ! nose ( ! human face %\ld retire beh9d ! e>s yet no su* effect is produc$1 z all ! features ( ! face are connect$ ) ea* o!r1 b if ! nose & e>s _h be5 repres5t$ sep>ately 9 ! position :i* !y occupy 9 ! human head1 ! ne>] features w\ld h retir$ beh9d ! m remote ones1 l ! sep>ate articles on a table4 ,we %all h occasion to resume ?is subject 9 our conclud+ *apt] on ! fallacies :i* take place 9 view+ solids1 :e!r rais$ or holl[1 & :e!r se5 by direct or inv]t$ vision4 ,,*apt] ,,xv4 ,,on ,,! ,,production ,,( ,,/]eoscopic ,,pictures ,,f ,a ,,s+le ,,picture4 ,^? :o are desir\s ( hav+ /]eoscopic relievos ( abs5t or deceas$ fri5ds1 & :o possess s+le photographic portraits ( !m1 or ev5 oil pa9t+s or m9iatures1 w be anxi\s to "k :e!r or n x is possible to obta9 f "o plane picture ano!r :i* c\ld be comb9$ ) x 9 ! /]eoscope2 t is1 if we consid] ! picture z "o se5 by ei!r eye alone1 c we by any process obta9 a second picture z se5 by ! o!r eye8 ,we h no hesitation 9 say+ t x is impossible to d ?is by any direct process4 ,e picture1 :e!r tak5 photographically or by ! eye1 is necess>ily a picture se5 by "o eye1 or f "o po9t ( sight2 &1 !re=e1 a skilful arti/1 :o fully und]/&s ! pr9ciple ( ! /]eoscope1 might make a copy ( any picture z se5 by ! o!r eye1 s approximately correct z to appe> 9 relief :5 unit$ ) ! orig9al 9 ! /]eoscope2 b ! task w\ld be a v difficult "o1 & if well execut$1 s z to give a relievo )\t di/ortion1 ! =tune ( ! pa9t] w\ld be made4 ,:5 ! arti/ executes a portrait1 he does x f "o po9t ( sight1 :i* we may suppose fix$1 & correspond+ ) t :i* is se5 ) 8 left eye4 ,if he takes ano!r portrait ( ! same p]son1 occupy+ exactly ! same position1 f ano!r po9t ( sight1 two & a half in*es to ! "r ( himself1 z se5 ) 8 "r eye1 ! two pictures w diff] only 9 ?is1 t ea* po9t 9 ! head1 & bu/1 & drap]y1 w1 9 ! second picture1 be c>ri$ f>!r to ! left ( ! arti/ on ! plane ( repres5tation4 ,! po9ts :i* project mo/1 or are mo/ di/ant f t plane1 w be c>ri$ f>!r to ! left ?an ^? :i* project less1 ! ext5t to :i* !y are c>ri$ be+ proportional to ! am\nt ( _! projection1 or _! di/ance f ! plane4 ,b s9ce ! pa9t] _c discov] f ! orig9al or left-eye plane picture ! degree ( prom95ce ( ! lead+ po9ts ( ! head1 ! bu/1 & ! drap]y1 he mu/ "w by guess1 & submit 8 empirical t\*es1 /ep by /ep1 to ! judgm5t ( ! /]eoscope4 ,9 devot+ himself to ?is bran* ( ! art he w d\btless acquire mu* k & dext]ity f exp]i5ce1 & may succe$ to a v consid]able ext5t 9 obta9+ pictures 9 relief1 if he foll[s c]ta9 rules1 :i* we %all endeav\r to expla94 ,if ! giv5 portrait1 or picture ( any k9d1 is n ( ! prop] size = ! /]eoscope1 x mu/ be r$uc$ to t size1 by tak+ a photographic copy ( x1 f :i* ! "r-eye picture is to be drawn4 ,illu/ration3 ,,fig4 #ej4 ,9 ord] to dim9i% ! size ( ! diagram1 let u suppose t ! plane on :i* ! portrait is tak5 t\*es ! back ( ! head1 & is repres5t$ 9 section by ,,ab1 ,fig4 #ej4 ,we mu/ n[ assume1 "u ! guidance ( ! orig9al1 a c]ta9 =m ( ! head1 ^: bread? f e> to e> is ,,ee1 ,n be+ ! po9t ( ! nose 9 ! horizontal section ( ! head1 ,e,,n51 pass+ ?r\gh ! nose ,n1 & ! lobes ,,ee ( ! two e>s4 ,let ,l1 ,r be ! left & "r eyes ( ! p]son view+ !m1 & ,,ln ! di/ance at :i* !y are view$1 & let l9es be drawn f ,l & ,r1 ?r\gh ,l1 ,n1 ,e & ,e1 meet+ ! plane ,,ab on :i* ! portrait is tak5 9 e1 ,e1 n1 ,n1 e1 & ,e4 ,! bread?1 ,ee1 & ! di/ances ( ! nose f ! e>s ,n,e1 ,n,e1 be+ giv5 by measurem5t ( ! photograph suit$ to ! /]eoscope1 ! di/ances ,,nn1 ,,ee1 ,e,e may be approximately obta9$ f ! kn[n =m ( ! human head1 ei!r by projection or calculation4 ,) ^! data1 procur$ z correctly z we c1 we %all1 f ! position ( ! nose n1 z se5 by ! "r eye ,r1 h ! =mula ,,lr ,,nn ,nn ---------------- ,,nl4 ,! di/ance ( ! "r e> e1 f ! "r-eye picture1 w be1 ne e,n - ,nn2 ,,lr ,,ee & z ,ee ------------------ ,,el4 ,! di/ance ( ! left e> e1 9 ! "r-eye picture1 f ! nose n1 w be ne ,nn ,n,e - ,ee4 ,9 ord] to simplify ! diagram we h made ! orig9al1 or left-eye picture1 a front view1 9 :i* ! nose is 9 ! middle ( ! face1 & ! l9e jo9+ ! e>s p>allel to ! plane ( ! picture4 ,:5 ! position ( ! nose & ! e>s has be5 ?us approximately obta9$1 ! arti/ may1 9 l mann]1 det]m9e ! place ( ! pupils ( ! two eyes1 ! po9t ( ! *91 ! summit ( ! eyebr[s1 ! prom95ce ( ! lips1 & ! junction ( ! nose ) ! tee?1 by assum+1 "u ! guidance ( ! orig9al picture1 ! di/ance ( ^! diff]5t p>ts f ! plane ( projection4 ,9 ! same way o!r lead+ po9ts 9 ! figure & drap]y may be f\nd1 & if ^! po9ts are det]m9$ ) tol]able accuracy ! arti/ w be able to draw ! features 9 _! new place ) su* correctness z to give a good result 9 ! /]eoscope4 ,9 draw+ ! "r-eye picture ! arti/ w1 ( c\rse1 employ z ! gr\ndwork ( x a fa9t photographic impression ( ! orig9al1 or left-eye picture1 & he may1 p]haps1 d]ive "s advantage f plac+ ! orig9al1 :5 be=e ! cam]a1 at su* an incl9ation to ! axis ( ! l5s z w produce ! same dim9ution 9 ! horizontal di/ance betwe5 any two po9ts 9 ! head1 at a mean di/ance betwe5 ,n & ,n1 z project$ ^u ! plane ,,ab4 ,! l9e ,n,e1 = example1 :i* 9 ! left-eye photograph is a repres5tation ( ! *eek ,,ne1 is r$uc$1 9 ! "r-eye photograph1 to ne1 &1 !re=e1 if ! photograph on ,,ab1 z se5 by ! "r eye1 7 plac$ s obliquely to ! axis ( ! l5s t ,ne 0 r$uc$ to ne1 ! copy obta9$ 9 ! cam]a w\ld h an approximate resemblance to ! "r-eye picture requir$1 & might be a bett] gr\ndwork = ! "r-eye picture ?an an accurate copy ( ! photograph on ,,ab1 tak5 :5 x is p]p5dicul> to ! axis ( ! l5s4 ,9 prep>+ ! "r-eye picture1 ! arti/1 9 place ( us+ pa9t1 might use v dilute solutions ( aceto-nitrate ( silv]1 beg9n+ ) ! fa9te/ t9t1 & d>k5+ ^! ) light till he obta9$ ! desir$ effect1 &1 :5 necess>y1 dim9i%+ ! %ades ) solutions ( ! hypo-sulphite ( soda4 ,:5 ! picture is f9i%$1 & f\nd satisfactory1 aft] exam9+ its relief 9 ! /]eoscope1 a negative picture ( x %\ld be obta9$ 9 ! cam]a1 & positive copies tak51 to =m1 ) ! orig9al photographs1 ! pair ( b9ocul> portraits requir$4 ,,*apt] ,,xvi4 ,,on ,,c]ta9 ,,fallacies ,,( ,,sight ,,9 ,,! ,,vision ,,( ,,solid ,,bodies4 ,9 a prec$+ *apt] ,i h expla9$ a rem>kable fallacy ( sight :i* takes place 9 ! /]eoscope :5 we int]*ange ! b9ocul> pictures1 t is1 :5 we place ! "r-eye picture on ! left side1 & ! left-eye picture on ! "r side4 ,! objects 9 ! =egr\nd ( ! picture are ?us ?r[n into ! backgr\nd1 &1 vice v]sa1 ! same effect1 z we h se51 takes place :5 we unite ! b9ocul> pictures1 9 _! usual position1 by ! ocul> /]eoscope1 t is1 by conv]g+ ! optic axes to a po9t betwe5 ! eye & ! pictures4 ,9 bo? ^! cases ! objects are only ! plane repres5tations ( solid bodies1 & ! *ange :i* is produc$ by _! union is n 9 _! =m b 9 _! position4 ,9 c]ta9 cases1 h[ev]1 :5 ! object is ( "s magnitude 9 ! picture1 ! =m is also *ang$ 9 consequ5ce ( ! inv]se position ( its p>ts4 ,t is1 ! draw+s ( objects t are naturally convex w appe> concave1 & ^? :i* are naturally concave w appe> convex4 ,9 ^! ph5om5a !re is no m5tal illusion 9 _! production4 ,! two simil> po9ts 9 ea* picture1 if !y are ne>] to "o ano!r ?an o!r two simil> po9ts1 mu/1 9 con=mity ) ! laws ( vision1 appe> ne>] ! eye :5 comb9$ 9 ! common /]eoscope4 ,:5 ?is *ange ( place & =m does n appe>1 z 9 ! case ( ! human figure1 previ\sly expla9$1 x is by a m5tal illusion t ! law ( vision is controll$4 ,! ph5om5a :i* we are ab\t to describe are1 9 sev]al respects1 diff]5t f ^? to :i* we h ref]r$4 ,!y are se5 9 monocul> z well z 9 b9ocul> vision1 & !y are produc$ 9 all cases "u a m5tal illusion1 aris+ ei!r f causes ov] :i* we h no control1 or volunt>ily creat$ & ma9ta9$ by ! obs]v]4 ,! fir/ notice ( ?is class ( optical illusion 0 giv5 by ,aguilonius 9 8 "w on optics1 to :i* we h already _h occasion to ref]4#fi ,aft] prov+ t convex & concave surfaces appe> plane :5 se5 at a consid]able di/ance1 he %ews t ! same surfaces1 :5 se5 at a mod]ate di/ance1 frequ5tly appe> :at he calls conv]se1 t is1 ! concave convex1 & ! convex concave4 ,?is conv]sion ( =ms1 he says1 is (t5 se5 9 ! globes or balls :i* are fix$ on ! walls ( =tifications1 & he ascribes ! ph5om5a to ! circum/ance ( ! m9d be+ impos$ ^u f n kn[+ 9 :at direction ! light falls ^u ! body4 ,he /ates t a concavity diff]s f a convexity only 9 ?is respect1 t if ! %ad[ is on ! same side z t f :i* ! light comes x is a concavity1 & if x is on ! opposite side1 x is a convexity4 ,aguilonius obs]ves also1 t 9 pictures imitat+ nature1 a simil> mi/ake is committ$ z to ! =m ( surfaces4 ,he supposes t a circle is drawn ^u a table & %ad$ on "o side s z to repres5t a convex or a concave surface4 ,:5 ?is %ad$ circle is se5 at a great di/ance1 x appe>s a plane surface1 not)/&+ ! %ad[ on "o side ( x2 b :5 we view x at a %ort di/ance1 & suppose ! light to come f ! same side ( x z ! "p n 9 %ad[1 ! plane circle w appe> to be a convexity1 & if we suppose ! light to come f ! same side z ! %ad$ "p1 ! circle w appe> to be a concavity4 #fi ,see ,*ap4 i4 p4 #ae4 ,m ?an half a c5tury aft] ! "t ( ,aguilonius1 a memb] ( ! ,royal ,society ( ,london1 at "o ( ! meet+s ( t body1 :5 look+ at a gu9ea ?r\gh a comp\nd microscope :i* inv]t$ ! object1 0 surpris$ to see ! head ^u ! co9 depress$1 :ile o!r memb]s 7 n subject to ?is illusion4 ,dr4 ,philip ,gmel9#gj ( ,wurtemb]g1 hav+ le>n$ f a fri5d1 t :5 a common seal is view$ ?r\gh a comp\nd microscope1 ! depress$ "p ( ! seal appe>$ elevat$1 & ! elevat$ "p depress$1 obta9$ ! same result1 & f\nd1 z ,aguilonius did1 t ! effect 0 ow+ to ! inv]sion ( ! %ad[ by ! microscope4 ,"o p]son (t5 saw ! ph5om5a & ano!r did n1 & no effect 0 produc$ :5 a rais$ object 0 s plac$ betwe5 two w9d[s z to be illum9at$ on all sides4 #gj ,phil4 ,trans4 #agdd4 ,9 #aghj ,mr4 ,ritt5h\se1 an ,am]ican writ]1 repeat$ ^! exp]im5ts ) an inv]t+ eye-tube1 consi/+ ( two l5ses plac$ at a di/ance great] ?an ! sum ( _! focal l5g?s1 & he f\nd t :5 a reflect$ light 0 ?r[n on a cavity1 9 a direction opposite to t ( ! light :i* came f 8 w9d[1 ! cavity 0 rais$ into an elevation by look+ ?r\gh a tube )\t any l5s4 ,9 ?is exp]im5t ! %ad[ 0 inv]t$1 j z if he _h look$ ?r\gh 8 inv]t+ eye-tube4 ,9 /udy+ ?is subject ,i obs]v$ a numb] ( s+ul> ph5om5a1 :i* ,i h describ$ 9 my ,lett]s on ,natural ,magic1#ga b z !y 7 n se5 by b9ocul> vision ,i %all m5tion only "s ( ! m important facts4 ,if we take "o ( ! intaglio m\lds us$ by ! late ,mr4 ,h5n+ = 8 bas-reliefs1 & direct ! eye to x /eadily1 )\t notic+ surr\nd+ objects1 we may di/9ctly see x z a bas-relief4 ,aft] a little practice ,i h succe$$ 9 rais+ a complete holl[ mask ( ! human face1 ! size ( life1 into a project+ head4 ,?is result is v surpris+ to ^? :o succe$ 9 ! exp]im5t1 & x w no d\bt be reg>d$ by ! sculptor :o c use x z an auxili>y 9 8 art4 #ga ,lett] v4 pp4 #ih-ajg4 ,see also ! ,ed9burgh ,j\rnal ( ,sci5ce1 ,jan4 #ahbf1 vol4 iv4 p4 #ii4 ,till )9 ! la/ few ye>s1 no ph5om5on ( ?is k9d1 ei!r z se5 ) "o or ) two eyes1 _h be5 notic$ by ! casual obs]v]4 ,philosoph]s alone _h be5 subject to ! illusion1 or _h subject$ o!rs to its influ5ce4 ,! foll[+ case1 h[ev]1 :i* occurr$ to ,lady ,georgiana ,wolff1 possesses mu* int]e/1 z x c\ld n possibly h be5 produc$ by any volunt>y ef=t4 8,lady ,georgiana10 says ,dr4 ,joseph ,wolff 9 8 ,j\rnal1 8obs]v$ a curi\s optical deception 9 ! s&1 ab\t ! middle ( ! day1 :5 ! sun 0 /rong3 all ! foot-pr9ts1 & o!r m>ks t are ind5t$ 9 ! s&1 _h ! appe>ance ( be+ rais$ out ( x4 ,at ^! times !re 0 su* a gl>e1 t x 0 unpleasant = ! eye40#gb ,hav+ no d\bt ( ! correctness ( ?is obs]vation1 ,i h (t5 endeav\r$1 ?\gh 9 va91 to witness s rem>kable a ph5om5on4 ,9 walk+1 h[ev]1 9 ! mon? ( ,m>* la/1 ) a fri5d on ! bea* at ,/4 ,&rews1 ! ph5om5on pres5t$ itself1 at ! same in/ant1 to myself & to a lady :o 0 unacqua9t$ ) ?is class ( illusions4 ,! impressions ( ! feet ( m5 & ( horses 7 di/9ctly rais$ out ( ! s&4 ,9 a %ort "t !y resum$ _! holl[ =m1 b at diff]5t places ! ph5om5on aga9 pres5t$ itself1 sometimes to myself1 sometimes to ! lady1 & sometimes to bo? ( u simultane\sly4 ,! sun 0 ne> ! horizon on our left h&1 & ! :ite surf ( ! sea 0 on our "r1 /rongly reflect+ ! sol> rays4 ,x is v probable t ! illusion arose f our consid]+ ! light z com+ f ! :ite surf1 9 :i* case ! %ad[s 9 ! holl[ foot-pr9ts 7 su* z c\ld only be produc$ by foot-pr9ts rais$ f ! s&1 z if !y 7 9 relief4 ,x is possible t1 :5 ! ph5om5on 0 obs]v$ by ,lady ,georgiana ,wolff1 !re may h be5 "s s\rce ( direct or reflect$ light opposite to ! sun1 or "s unusual brightness ( ! cl\ds1 if !re 7 any 9 t qu>t]1 :i* gave rise to ! illusion4 #gb ,j\rnal1 #ahci1 p1 #ahi4 ,:5 ^! illusions1 :e!r monocul> or b9ocul>1 are produc$ by an inv]sion ( ! %ad[1 ei!r real or suppos$1 !y are in/antly dissipat$ by hold+ a p9 9 ! field ( view1 s z to indicate by its %ad[ ! real place ( ! illum9at+ body4 ,! figure w appe> rais$ or depress$1 accord+ to ! k :i* we obta9 ( ! s\rce ( light1 by introduc+ or )draw+ ! p94 ,:5 ! inv]sion is produc$ by ! eye-piece ( a telescope1 or a comp\nd microscope1 9 :i* ! field ( view is necess>ily small1 we _c see ! illum9at+ body & ! convex or concave object 7! cameo or intaglio7 at ! same "t2 b if we use a small inv]t+ telescope1 #a or #b in*es long1 su* z t %ewn at ,,mn1 ,fig4 #cf1 we obta9 a l>ge field ( view1 & may see at ! same "t ! object & a c&le plac$ beside x4 ,9 ?is case ! illusion w take place accord+ z ! c&le is se5 beside ! object or )drawn4 ,if ! object is a :ite tea-cup1 or b[l1 h[ev] l>ge1 & if x is illum9at$ f beh9d ! obs]v]1 ! reflect$ image ( ! w9d[ w be 9 ! concave bottom ( ! tea-cup1 & x w n rise into a convexity if ! illum9ation f surr\nd+ objects is uni=m2 b if ! obs]v] moves a little to "o side1 s t ! reflect$ image ( ! w9d[ passes f ! c5tre ( ! cup1 !n ! cup w rise into a convexity1 :5 se5 ?r\gh ! inv]t+ telescope1 9 consequ5ce ( ! position ( ! lum9\s image1 :i* c\ld occupy its place only ^u a convex surface4 ,if ! concave body 7 cut out ( a piece ( *alk1 or pure unpoli%$ m>ble1 x w\ld appe> nei!r convex nor concave1 b flat4 ,v s+ul> illusions take place1 bo? ) "o & two eyes1 :5 ! object1 :e!r concave or convex1 is a holl[ or an elevation 9 or ^u a limit$ or ext5d$ surface--t is1 :e!r ! surface occupies ! :ole visible field1 or only a "p ( x4 ,if we view1 ?r\gh ! inv]t+ telescope or eye-piece1 a dimple or a hemisph]ical cavity 9 a broad piece ( wood laid horizontally on ! table1 & illum9at$ by quaquav]sus light1 l t ( ! sky1 x w in/antly rise into an elevation1 ! end ( ! telescope or eye-piece re/+ on ! surface ( ! wood4 ,! *ange ( =m is1 !re=e1 n produc$ by ! inv]sion ( ! %ad[1 b by ano!r cause4 ,! surface 9 :i* ! cavity is made is obvi\sly inv]t$ z well z ! cavity1 t is1 x n[ looks d[nw>d 9 place ( upw>d2 b x does n appe> s to ! obs]v] lean+ ^u ! table1 & re/+ ! end ( 8 eye-piece ^u ! wood5 surface 9 :i* ! cavity is made4 ,! surface seems to him to rema9 :]e x 01 & /ill to look upw>ds1 9 place ( look+ d[nw>ds4 ,if ! obs]v] /rikes ! wood5 surface ) ! end ( ! eye-piece1 ?is conviction is /r5g!n$1 & he believes t x is ! l[] edge ( ! field ( view1 or object-glass1 t /rikes ! app>5t wood5 surface or re/s ^u x1 :]eas ! wood5 surface has be5 inv]t$1 & optically sep>at$ f ! l[] edge ( ! object-glass4 ,9 ord] to make ?is pla9]1 place a p5 ^u a %eet ( pap] ) ! quill end ne>e/ y1 & view x ?r\gh ! inv]t+ telescope3 ,! quill end w appe> f>!/ f y1 & ! pap] w n appe> inv]t$4 ,9 l mann]1 ! lett]s on a pr9t$ page are inv]t$1 ! top ( ea* lett] be+ ne>e/ ! obs]v]1 :ile ! pap] seems to reta9 its usual place4 ,n[ 9 bo? ^! cases ! pap] is inv]t$ z well z ! quill & ! lett]s1 & 9 reality ! image ( ! quill & ( ! p51 & ( ! l[] end ( ! lett]s1 is ne>e/ ! obs]v]4 ,let u next place a tea-cup on its side ^u ! table1 ) its concavity t[>ds ! obs]v]1 & view x ?r\gh ! inv]t+ telescope4 ,x w rise into a convexity1 ! ne>] m>g9 ( ! cup appe>+ f>!r (f ?an ! bottom4 ,if we place a %ort p5 )9 ! cup1 measur+ z x 7 its dep?1 & hav+ its quill end ne>e/ ! obs]v]1 ! p5 w be inv]t$1 9 correspond5ce ) ! conv]sion ( ! cup into a convexity1 ! quill end appe>+ m remote1 l ! m>g9 ( ! cup :i* x t\*es1 & ! fea!r end next ! eye l ! summit ( ! convex cup on :i* x re/s4 ,9 ^! exp]im5ts1 ! conv]sion ( ! concavity into a convexity dep5ds on two sep>ate illusions1 "o ( :i* spr+s f ! o!r4 ,! fir/ illusion is ! errone\s conviction t ! surface ( ! table is look+ upw>ds z usual1 :]eas x is really inv]t$2 & ! second illusion1 :i* arises f ! fir/1 is1 t ! ne>e/ po9t ( ! object appe>s f>!/ f ! eye1 :]eas x is ne>e/ to x4 ,all ^! obs]vations are equally applicable to ! vision ( convexities1 & h5ce x foll[s1 t ! conv]sion ( relief1 caus$ by ! use ( an inv]t+ eye-piece1 is n produc$ directly by ! inv]sion1 b by an illusion aris+ f ! inv]sion1 9 virtue ( :i* we believe t ! remote/ side ( ! convexity is ne>] our eye ?an ! side next u4 ,9 ord] to demon/rate ! correctness ( ?is explanation1 let ! hemisph]ical cavity be made 9 a /ripe ( wood1 n>r[] ?an ! field ( ! inv]t+ telescope ) :i* x is view$4 ,x w !n appe> really inv]t$1 & free f bo? ! illusions :i* =m]ly took place4 ,! ?ickness ( ! /ripe ( wood is n[ di/9ctly se51 & ! inv]sion ( ! surface1 :i* n[ looks d[nw>d1 imm$iately recognis$4 ,! edge ( ! cavity n[ appe>s ne>e/ ! eye1 z x really is1 & ! concavity1 ?\gh inv]t$1 /ill appe>s a concavity4 ,! same effect is produc$ :5 a convexity is plac$ on a n>r[ /ripe ( wood4 ,"s curi\s ph5om5a take place :5 we view1 at diff]5t degrees ( obliquity1 a hemisph]ical cavity rais$ into a convexity4 ,at e degree ( obliquity f #j to #ij1 t is1 f a v]tical to a horizontal view ( x1 ! elliptical m>g9 ( ! convexity w always be visible1 :i* is impossible 9 a real convexity1 & ! elevat$ apex w gradually s9k till ! elliptical m>g9 becomes a /raight l9e1 & ! imag9>y convexity completely levell$4 ,! /ruggle betwe5 tru? & error is "h s s+ul>1 t :ile "o "p ( ! object has become concave1 ! o!r "p reta9s its convexity6 ,9 l mann]1 :5 a convexity is se5 z a concavity1 ! concavity loses its true %ape z x is view$ m & m obliquely1 till its remote elliptical m>g9 is encroa*$ ^u1 or eclips$1 by ! apex ( ! convexity2 & t[>ds an incl9ation ( #ij ! concavity disappe>s altoge!r1 "u circum/ances analog\s to ^? already describ$4 ,if 9 place ( us+ an inv]t+ telescope we inv]t ! concavity1 by look+ at its inv]t$ image 9 ! focus ( a convex l5s1 x w sometimes appe> a convexity & sometimes n4 ,9 ?is =m ( ! exp]im5t ! image ( ! concavity1 & consequ5tly its app>5t dep?1 is greatly dim9i%$1 & !re=e any trivial cause1 su* z a preconception ( ! m9d1 or an approximation to a %ad[1 or a t\* ( ! concavity by ! po9t ( ! f+]1 w ei!r produce a conv]sion ( =m or dissipate ! illusion :5 x is produc$4 ,9 ! prec$+ ,*apt] we h suppos$ ! convexity to be high & ! concavity deep & circul>1 & we h suppos$ !m also to be %ad[less1 or illum9at$ by a quaquav]sus light1 su* z t ( ! sky 9 ! op5 fields4 ,?is 0 done 9 ord] to get rid ( all second>y causes :i* might int]f]e ) & modify ! normal cause1 :5 ! concavities are %all[1 & ! convexities l[ & h di/9ct %ad[s1 or :5 ! concavity1 z 9 seals1 has ! %ape ( an animal or any body :i* we are accu/om$ to see 9 relief4 ,let u n[ suppose t a /rong %ad[ is ?r[n ^u ! concavity4 ,9 ?is case ! normal exp]im5t is mu* m p]fect & satisfactory4 ,! illusion is complete & inv>iable :5 ! concavity is 9 or ^u an ext5d$ surface1 & x z inv>iably disappe>s1 or r is n produc$1 :5 x is 9 a n>r[ /ripe4 ,9 ! second>y =ms ( ! exp]im5t1 ! inv]sion ( ! %ad[ becomes ! pr9cipal cause ( ! illusion2 b 9 ord] t ! result may be inv>iable1 or ne>ly s1 ! concavities mu/ be %all[ & ! convexities b slightly rais$4 ,at great obliquities1 h[ev]1 ?is cause ( ! conv]sion ( =m ceases to produce ! illusion1 & 9 v>y+ ! incl9ation f #j to #ij ! cessation takes place soon] ) deep ?an ) %all[ cavities4 ,! reason ( ?is is t ! %ad[ ( a concavity is v diff]5t at great obliquities f ! %ad[ ( a convexity4 ,! %ad[ nev] c em]ge out ( a cavity s z to d>k5 ! surface 9 :i* ! cavity is made1 :]eas ! %ad[ ( a convexity soon ext5ds beyond ! outl9e ( its base1 & f9ally ?r[s a long /ripe ( d>kness ov] ! surface on :i* x re/s4 ,h5ce x is impossible to mi/ake a convexity = a concavity :5 its %ad[ ext5ds beyond its base4 ,:5 ! concavity ^u a seal is a horse1 or any o!r animal1 x w (t5 rise into a convexity :5 se5 ?r\gh a s+le l5s1 :i* does n inv]t x2 b ! illusion disappe>s at great obliquities4 ,9 ?is case1 ! illusion is fav\r$ or produc$ by two causes2 ! fir/ is1 t ! =m ( ! horse or o!r animal 9 relief is ! "o :i* ! m9d is mo/ dispos$ to seize1 & ! second is1 t we use only "o eye1 ) :i* we _c measure dep?s z well z ) two4 ,! illusion1 h[ev]1 /ill takes place :5 we employ a l5s ?ree or m in*es wide1 s z to p]mit ! use ( bo? eyes1 b x is less c]ta91 z ! b9ocul> vision enables u 9 "s degree to keep 9 *eck ! o!r causes ( illusion4 ,! influ5ce ( ^! second>y causes is /rik+ly display$ 9 ! foll[+ exp]im5t4 ,9 ! armorial be>+s ^u a seal1 ! %ield is (t5 m deeply cut ?an ! surr\nd+ p>ts4 ,) b9ocul> vision1 ! %all[ p>ts rise into relief soon] ?an ! %ield1 & cont9ue s :ile ! %ield rema9s depress$2 b if we %ut "o eye ! %ield !n rises into relief l ! re/4 ,9 ^! exp]im5ts ) a s+le l5s a slight v>iation 9 ! position ( ! seal1 or a slight *ange 9 ! int5sity or direction ( ! illum9ation1 or p>ticul> reflexions f ! int]ior ( ! /one1 if x is transp>5t1 w fav\r or oppose ! illusion4 ,9 view+ ! %ield at ! deepe/ portion ) a s+le l5s1 a slight rotation ( ! seal r\nd ! wri/1 backw>ds & =w>ds1 w remove ! illusion1 9 consequ5ce ( ! eye p]ceiv+ t ! *ange 9 ! p]spective is diff]5t f :at x ought to be4 ,9 my ,lett]s on ,natural ,magic1 ,i h describ$ sev]al cases ( ! conv]sion ( =m 9 :i* inv]t$ vision is n employ$4 ,holl[s 9 "m-(-pe>l & o!r semi-transp>5t bodies (t5 rise into relief1 9 consequ5ce ( a quantity ( light1 occasion$ by refraction1 appe>+ on ! side next ! light1 :]e !re %\ld h be5 a %ad[ 9 ! case ( a depression4 ,simil> illusions take place 9 c]ta9 pieces ( poli%$ wood1 calc$ony1 "m-(-pe>l1 & o!r %ells1 :]e ! surface is p]fectly plane4 ,?is arises f !re be+ at t place a knot1 or gr[?1 or nodule1 diff]+ 9 transp>5cy f ! surr\nd+ mass4 ,! ?9 edge ( ! knot1 c41 opposite ! c&le1 is illum9at$ by refract$ light1 s t x takes ! appe>ance ( a concavity4 ,f ! same cause arises ! appe>ance ( dimples 9 c]ta9 plates ( calc$ony1 :i* h receiv$ ! "n ( hamm]$ calc$ony1 or agate1 f _! hav+ ! look ( be+ dimpl$ ) a hamm]4 ,! surface on :i* ^! cavities are se5 conta9s sections ( small sph]ical =mations ( silice\s matt]1 :i* exhibit ! same illusion z ! cavities 9 wood4 ,"m-(-pe>l pres5ts simil> ph5om5a1 & s common are !y 9 ?is sub/ance t x is difficult to f9d a "m-(-pe>l button or c\nt] :i* seems to h its surface flat1 al?\gh x is p]fectly s :5 exam9$ by ! t\*4 ,ow+ to ! diff]5t refractions ( ! incid5t light by ! diff]5t gr[?s ( ! %ell1 cut 9 diff]5t directions by ! artificial surface1 l ! annual gr[? ( wood 9 a dress$ plank1 ! surface ( ! m9]al has necess>ily an inequal & undulat+ appe>ance4 ,9 view+ good photographic or well-pa9t$ m9iature portraits 9 an erect & inv]t$ position1 & ) or )\t a l5s1 consid]able *anges take place 9 ! app>5t relief4 ,"u ord9>y vision !re is a c]ta9 am\nt ( relief dep5d+ ^u ! excell5ce ( ! picture4 ,if we inv]t ! picture1 by turn+ x upside d[n1 ! relief is p]ceptibly increas$4 ,if we view x :5 erect1 ) a l5s ( ab\t an in* 9 focal l5g?1 ! relief is /ill great]2 b if we view x :5 inv]t$ ) ! same l5s ! relief is v consid]ably dim9i%$4 ,illu/ration3 ,,fig4 #ea4 ,a v rem>kable illusion1 affect+ ! app>5t position ( ! draw+s ( geometrical solids1 0 fir/ obs]v$ by ! late ,pr(essor ,neck>1 ( ,g5eva1 :o communicat$ x to me p]sonally 9 #ahcb4gc 8,! rhomboid ,,ax10 7,fig4 #ea17 he says1 8is drawn s t ! solid angle ,a %\ld be se5 ne>e/ to ! spectator1 & ! solid angle ,x ! f>!/ f him1 & t ! face ,,acbd %\ld be ! =emo/1 :ile ! face ,,xdc is beh9d4 ,b 9 look+ repeat$ly at ! same figure1 y w p]ceive t at times ! app>5t position ( ! rhomboid is s *ang$ t ! solid angle ,x w appe> ! ne>e/1 & ! solid angle ,a ! f>!/1 & t ! face ,,acdb w rec$e beh9d ! face ,,xdc1 :i* w come =w>d1--:i* effect gives to ! :ole solid a q contr>y app>5t incl9ation40 ,pr(essor ,neck> obs]v$ ?is *ange 8z well ) "o z ) bo? eyes10 & he consid]$ x z ow+ 8to an involunt>y *ange 9 ! adju/m5t ( ! eye = obta9+ di/9ct vision4 ,& t :5ev] ! po9t ( di/9ct vision on ! ret9a 0 direct$ to ! angle ,a = in/ance1 ?is angle1 se5 m di/9ctly ?an ! o!r1 0 naturally suppos$ to be ne>] & =emo/1 :ile ! o!r angles1 se5 indi/9ctly1 7 suppos$ to be f>!r away & beh9d4 ,! rev]se took place :5 ! po9t ( di/9ct vision 0 br\ght to be> ^u ! angle ,x4 ,:at ,i h said ( ! solid angles 7,a & ,x7 is equally true ( ! edges1 ^? edges ^u :i* ! axis ( ! eye1 or ! c5tral hole ( ! ret9a1 are direct$1 w always appe> =w>d2 s t n[ x seems to me c]ta9 t ?is little1 at fir/ s puzzl+1 ph5om5on dep5ds ^u ! law ( di/9ct vision40 #gc ,see ,ed9burgh ,philosophical ,j\rnal1 ,novemb] #ahcb1 vol4 i4 p4 #ccd4 ,9 consequ5ce ( completely misund]/&+ ,mr4 ,neck>'s explanation ( ?is illusion1 ,mr4 ,:eat/one has pron\nc$ x to be errone\s1 b !re c be no d\bt ( its correctness2 & !re are v>i\s exp]im5ts by :i* ! pr9ciple may be illu/rat$4 ,by hid+ ) ! f+] "o ( ! solid angles1 or mak+ x indi/9ct1 by a piece ( dimm$ glass1 or ?r[+ a slight %ad[ ov] x1 ! o!r w appe> =emo/ till ! obscur+ cause is remov$4 ,! exp]im5t may be /ill m satisfactorily made by hold+ above ! rhomboid a piece ( f9ely gr\nd-glass1 ! gr\nd side be+ f>!/ f ! eye1 & br++ "o edge ( x gradually d[n till x t\*es ! po9t ,a1 ! o!r edge be+ kept at a di/ance f ! pap]4 ,9 ?is way all ! l9es div]g+ f ,a w become dimm] z !y rec$e f ,a1 & consequ5tly ,a w appe> ! mo/ =w>d po9t4 ,a simil> result w be obta9$ by putt+ a black spot ^u ,a1 :i* w h ! effect ( draw+ our att5tion to ,a r ?an to ,x4 ,f ^! exp]im5ts & obs]vations1 x w be se5 t ! conv]sion ( =m1 except+ 9 ! normal case1 dep5ds ^u v>i\s causes1 :i* are influ5tial only "u p>ticul> conditions1 su* z ! dep? ( ! holl[ or ! height ( ! relief1 ! di/ance ( ! object1 ! %>pness ( vision1 ! use ( "o or bo? eyes1 ! inv]sion ( ! %ad[1 ! nature ( ! object1 & ! means us$ by ! m9d itself to produce ! illusion4 ,9 ! normal case1 :]e ! cavity or convexity is %ad[less1 & ^u an ext5d$ surface1 & :]e inv]t$ vision is us$1 ! conv]sion dep5ds solely on ! illusion1 :i* x is impossible to resi/1 t ! side ( ! cavity or elevation next ! eye is actually f>!/ f x1 an illusion n produc$ by inv]sion1 b by a false judgm5t respect+ ! position ( ! surface 9 :i* ! cavity is made1 or ^u :i* x re/s4 ,,*apt] ,,xvii4 ,,on ,,c]ta9 ,,difficulties ,,exp]i5c$ ,,9 ,,! ,,use ,,( ,,! ,,/]eoscope4 ,!re are _m p]sons :o exp]i5ce great difficulty 9 unit+ ! two pictures 9 ! /]eoscope1 & consequ5tly 9 see+ ! relief produc$ by _! union4 ,if ! eyes are n equal 9 focal l5g?1 t is1 9 ! di/ance at :i* !y see objects mo/ di/9ctly2 or if1 f "s defect 9 /ructure1 !y are n equally good1 !y w /ill see ! /]eoscopic relief1 ?\gh ! picture w be less vivid & di/9ct ?an if ! eyes 7 9 e respect equal & good4 ,!re are _m p]sons1 h[ev]1 ^: eyes are equal & p]fect1 b :o are n able to unite ! pictures 9 ! /]eoscope4 ,?is is ! m rem>kable1 z *ildr5 ( f\r or five ye>s ( age see ! /]eoscopic effect :5 ! eye-tubes are accommodat$ to ! di/ance betwe5 _! eyes4 ,! difficulty exp]i5c$ 9 unit+ ! b9ocul> pictures is sometimes only tempor>y4 ,on fir/ look+ into ! in/rum5t1 two pictures are se5 9 place ( "o2 b by a little p]sev]ance1 & by draw+ ! eyes away f ! eye-tubes1 & /ill look+ ?r\gh !m1 ! object is se5 s+le & 9 p]fect relief4 ,aft] hav+ ceas$ to use ! in/rum5t = "s "t1 ! difficulty ( unit+ ! pictures recurs1 b1 g5]ally speak+1 x w gradually disappe>4 ,illu/ration3 ,,fig4 #eb4 ,9 ^? cases :]e x _c be ov]come by repeat$ trials1 x mu/ arise ei!r f ! di/ance betwe5 ! l5ses be+ great] or less ?an ! di/ance betwe5 ! eyes1 or f "s peculi>ity 9 ! p[] ( conv]g+ ! optical axes1 :i* x is n easy to expla94 ,if ! di/ance betwe5 ! pupils ( ! two eyes1 ,e1 ,e1 ,fig4 #eb1 :i* has be5 already expla9$ on ,fig4 #ah1 is less ?an ! di/ance betwe5 ! semi-l5ses ,l1 ,l1 !n1 in/ead ( look+ ?r\gh ! middle portions no1 no1 ( ! l5ses1 ! obs]v] w look ?r\gh portions betwe5 o & ,l1 & o & ,l1 :i* h a great] p[] ( refract+ or displac+ ! pictures ?an ! portions no1 no1 & !re=e ! pictures w be too mu* displac$1 & w h s f> ov]pass$ "o ano!r t ! obs]v] is n able to br+ !m back to _! place ( union1 half-way betwe5 ! two pictures 9 ! slide4 ,if1 on ! o!r h&1 ! di/ance betwe5 ! pupils ( ! obs]v]'s eyes is great] ?an ! di/ance betwe5 ! semi-l5ses ,l1 ,l1 !n1 in/ead ( look+ ?r\gh ! portions no1 no ( ! l5ses1 ! obs]v] w look ?r\gh portions betwe5 n & ,l1 & n & ,l1 :i* h a less p[] ( refract+ or displac+ ! pictures ?an ! portions no1 no1 & !re=e ! pictures w be s little displac$ z n to rea* _! place ( union1 & w /& at su* a di/ance t ! obs]v] is n able to br+ !m up to _! prop] place1 half-way betwe5 ! two pictures 9 ! slide4 ,n[1 9 bo? ^! cases ( ov] & "u displacem5t1 _m p]sons h su* a p[] ov] _! optical axes1 t by conv]g+ !m to a po9t ne>] ?an ! picture1 !y w\ld1 9 ! fir/ case1 br+ !m back to _! place ( union1 & by conv]g+ !m to a po9t m remote ?an ! picture1 w\ld1 9 ! second case1 br+ !m up to _! place ( union2 b o!rs are v defective 9 ?is p[] ( conv]g5ce1 "s hav+ a facility ( conv]g+ !m beyond ! pictures1 & o!rs betwe5 ! pictures & ! eye4 ,?is la/1 h[ev]1 namely1 t ( ne> conv]g5ce1 is by f> ! mo/ common1 especially among m52 b x is ( no avail1 & ! ex]cise ( x is injuri\s :5 ! "u refract$ pictures h n come up to _! place ( union4 ,! p[] ( remote conv]g5ce1 :i* is v r>e1 & :i* w\ld assi/ 9 br++ back ! ov] refract$ pictures to _! place ( union1 is ( no avail1 & ! ex]cise ( x is injuri\s :5 ! pictures h be5 too mu* displac$1 & made to pass beyond _! place ( union4 ,:5 ! /]eoscope is p]fectly adapt$ to ! eyes ( ! obs]v]1 & ! g5]al union ( ! pictures effect$1 ! remote p>ts ( ! picture1 t is1 ! objects se5 9 ! di/ance1 may be "u refract$1 :ile ^? 9 ! =egr\nd are ov] refract$1 s t :ile eyes :i* h ! p[] ( conv]g5ce beyond ! picture1 unite ! m di/ant objects :i* are "u refract$1 !y exp]i5ce mu* difficulty 9 unit+ ^? 9 ! =egr\nd :i* are ov] refract$4 ,9 l mann]1 eyes :i* h ! p[] ( ne> conv]g5ce w readily unite objects 9 ! =egr\nd :i* are ov] refract$1 :ile !y exp]i5ce mu* difficulty 9 unit+ objects 9 ! di/ance :i* are "u refract$4 ,if ! requisite p[] ov] ! optical axes is n acquir$ by exp]i5ce & p]sev]ance1 :5 ! /]eoscope is suit$ to ! eyes ( ! obs]v]1 ! only sugge/ion :i* we c make is to op5 ! eyes wide1 & exp& ! eyebr[s1 :i* we d 9 />+ at an object1 or 9 look+ at a di/ant "o1 :5 we wi% to conv]ge ! axes1 z 9 ,fig4 #bb1 to a po9t beyond ! pictures1 & to contract ! eyes & ! eyebr[s1 :i* we d 9 too mu* light1 9 look+ at a ne> object1 :5 we wi% to conv]ge ! optic axes1 z 9 ,fig4 #ba1 to a po9t betwe5 ! pictures & ! eye4 ,:5 ! b9ocul> pictures are tak5 at too great an angle1 s z to produce a />tl+ am\nt ( relief1 ! di/ance betwe5 simil> po9ts 9 ea* picture1 bo? 9 ! di/ance & 9 ! =egr\nd1 is mu* great] ?an x ought to be1 & h5ce ! difficulty ( unit+ ! pictures is greatly increas$1 s t p]sons :o w\ld h exp]i5c$ no difficulty 9 unit+ !m1 _h !y be5 tak5 at ! prop] angle1 w fail altoge!r 9 br++ !m into /]eoscopic relief4 ,9 ^! obs]vations1 x is und]/ood t ! obs]v] obta9s di/9ct vision ( ! pictures 9 ! /]eoscope1 ei!r by ! adju/m5t ( ! moveable eye-tubes1 if !y are moveable1 z !y ought to be1 or by ! aid ( convex or concave glasses = bo? eyes1 ei!r 9 ! =m ( spectacles1 or sep>ate l5ses plac$ imm$iately above1 or imm$iately bel[ ! semi-l5ses 9 ! eye-tubes4 ,if ! eyes h diff]5t focal l5g?s1 :i* is n unfrequ5tly ! case1 l5ses diff]+ 9 convexity or concavity %\ld be employ$ to equalize !m4 ,,ed9burgh3 ,t4 ,,con/able1 ,,pr9t] ,,to ,,h] ,,maje/y4