,,g5]al ,,sci5ce ,,by ,,b]?a ,m4 ,,cl>k1 ,,ph4,d4 ,,head ,,( ,,! ,,sci5ce ,,dep>tm5t ,,william ,,p5n ,,high ,,s*ool ,,= ,,girls1 ,,philadelphia ,,new ,,york - ,,c9c9nati - ,,*icago ,,am]ican ,,book ,,company #aiab ,,preface ,?is book is n int5d$ to prep>e = college entrance exam9ations2 x w n1 9 fact1 prep>e = any ( ! pres5t-day /ock exam9ations 9 physics1 *emi/ry1 or hygi5e1 b x %\ld prep>e ! ?\ghtful read] to meet wisely & actively "s ( life's important problems1 & %\ld enable him to pass mu/] on ! pr9ciples & !ories und]ly+ sci5tific1 & !re=e economic1 managem5t1 :e!r 9 ! %op or 9 ! home4 ,we he> a great deal ab\t ! cons]vation ( our natural res\rces1 su* z =e/s & wat]ways2 x is hop$ t ?is book w %[ ! vital importance ( ! cons]vation ( human /r5g? & heal?1 & ! irrep>able loss to society ( en]gy uselessly dissipat$1 ei!r 9 idle worry or 9 aimless activity4 ,mo/ ( u w\ld reproa* ourselves = lack ( %rewdness if we sp5t = any article m ?an x 0 wor?1 yet few ( u consid] t we daily exp5d on dome/ic & bus9ess tasks an am\nt ( en]gy f> 9 excess ( t actually requir$4 ,! f>m] :o flails 8 gra9 in/ead ( ?re%+ x wa/es "t & en]gy2 ! h\sewife :o wa%es ) h] h&s alone & does n aid h]self by ! use ( wa%+ ma*9e & prop] blea*+ ag5ts dissipates en]gy sadly ne$$ = o!r duties4 ,! ,*apt] on ma*9es is int5d$ n only z a /imulus to ! inv5tion ( fur!r labor-sav+ devices1 b also z an eye op5] to ^? :o1 9 ! future /ruggle = exi/5ce1 mu/ p]=ce g to ! wall unless !y und]/& h[ to make use ( contrivances :]eby man's limit$ physical /r5g? is made effective = l>g] tasks4 ,! ,*apt] on musical in/rum5ts is m detail$ ?an seems w>rant$ at fir/ sight2 b int]e/ 9 or*e/ral in/rum5ts is real & g5]al1 & !re is a p]si/5t desire = intellig5t in=mation relative to musical in/rum5ts4 ,! *ild ( ! labor] z well z ! *ild ( ! m]*ant f9ds x possible to att5d "s ( ! weekly or*e/ral conc]ts1 ) _! ti]s ( *eap seats1 & no?+ adds m to ! enjoym5t & in/ruction ( su* h\rs ?an an intimate acqua9tance ) ! lead+ in/rum5ts4 ,unless ?is is giv5 9 ! public s*ools1 a l>ge p]c5tage ( mank9d is depriv$ ( x1 & x is = ?is reason t s l>ge a %>e ( ! treatm5t ( s\nd has be5 devot$ to musical in/rum5ts4 ,! treatm5t ( electricity is m !oretical ?an t us$ 9 prec$+ ,*apt]s1 b ! subject does n l5d itself readily to popul> pres5tation2 &1 moreov]1 x is assum$ t ! in=mation & tra9+ acquir$ 9 ! previ\s "w w give ! pupil p[] to und]/& ! m advanc$ ?\ght & me?od4 ,! real value ( a book dep5ds n s mu* ^u ! in=mation giv5 z ^u ! p]man5t int]e/ /imulat$ & ! initiative ar\s$4 ,! y\?ful m9d1 & inde$ ! av]age adult m9d z well1 is s+ul>ly non-logical & incapable ( cont9u$ conc5tration1 & loses int]e/ "u too consecutive ?\ght & su/a9$ /yle4 ,= ?is reason ! au?or has sacrific$ at times detail to g5]al effect1 logical developm5t to pres5t-day int]e/ & facts1 & has made use ( a popul>1 light /yle ( writ+ z well z ( ! m =mal & logical /yle common to books ( sci5ce4 ,no claim is made to orig9ality 9 subject matt]4 ,! actual facts1 !ories1 & pr9ciples us$ are su* z h be5 pres5t$ 9 previ\s textbooks ( sci5ce1 b ! mann] & sequ5ce ( pres5tation are new &1 s f> z ,i "k1 untri$ else:]e4 ,^! are su* z 9 my exp]i5ce h ar\s$ ! greate/ int]e/ & initiative1 & su* z h at ! same "t giv5 ! maximum b5efit f ! in=mational /&po9t4 ,9 no case1 h[ev]1 is m5tal tra9+ sacrific$ to in=mation2 b m5tal developm5t is s\ght ?r\gh ! /ud5t's will+ & int]e/$ p>ticipation 9 ! actual daily happ5+s ( ! home & ! %op & ! field1 r ?an ?r\gh =mal recitations & laboratory exp]im5ts4 ,practical laboratory "w 9 connection ) ! /udy ( ?is book is provid$ = 9 my ,laboratory ,manual 9 ,g5]al ,sci5ce1 :i* conta9s directions = a s]ies ( exp]im5ts design$ to make ! pupil famili> ) ! facts & !ories discuss$ 9 ! textbook4 ,i h s\ght & h ga9$ help f _m ( ! /&>d textbooks1 new & old4 ,! foll[+ firms h k9dly plac$ cuts at my disposal1 & h ?us mat]ially aid$ 9 ! prep>ation ( ! illu/rations3 ,am]ican ,radiator ,company2 ,comm]cial ,museum1 ,philadelphia2 ,g5]al ,electric ,company2 ,h]%ey ,*ocolate ,company2 ,sci5tific ,am]ican2 ,! ,g\lds ,manufactur+ ,company2 ,victor ,talk+ ,ma*9e ,company4 ,ackn[l$gm5t is also due to ,pr(essor ,alv9 ,davison = figures #ai1 #bc1 #bi1 #adb1 & #afa4 ,mr4 ,w4,d4 ,lewis1 ,pr9cipal ( ! ,william ,p5n ,high ,s*ool1 has read ! manuscript & has giv5 me ! b5efit ( 8 exp]i5ce & int]e/4 ,miss4 ,hel5 ,hill1 libr>ian ( ! same s*ool1 has be5 ( invaluable s]vice z reg>ds sugge/ions & pro( read+4 ,miss4 ,droege1 ( ! ,baldw9 ,s*ool1 ,bryn ,mawr1 has also be5 ( v great s]vice4 ,practically all ( my assi/ants h giv5 ( _! "t & skill to ! prep>ation ( ! "w1 b ! li/ is too long = individual m5tion4 ,,b]?a ,m4 ,,cl>k4 ,,william ,,p5n ,,high ,,s*ool4 ,,cont5ts ,,*apt] ,i4 ,,heat ,,ii4 ,,temp]ature ,,& ,,heat ,,iii4 ,,o!r ,,facts ,,ab\t ,,heat ,,iv4 ,,burn+ ,,or ,,oxidation ,v4 ,,food ,,vi4 ,,wat] ,,vii4 ,,air ,,viii4 ,,g5]al ,,prop]ties ,,( ,,gases ,,ix4 ,,invisible ,,objects ,x4 ,,light ,,xi4 ,,refraction ,,xii4 ,,photography ,,xiii4 ,,color ,,xiv4 ,,heat ,,& ,,light ,,z ,,companions ,,xv4 ,,artificial ,,light+ ,,xvi4 ,,man',s ,,way ,,( ,,help+ ,,himself ,,xvii4 ,,! ,,p[] ,,beh9d ,,! ,,eng9e ,,xviii4 ,,pumps ,,& ,,_! ,,value ,,to ,,man ,,xix4 ,,! ,,wat] ,,problem ,,( ,a ,,l>ge ,,city ,,xx4 ,,man',s ,,conque/ ,,( ,,sub/ances ,,xxi4 ,,f]m5tation ,,xxii4 ,,blea*+ ,,xxiii4 ,,dye+ ,,xxiv4 ,,*emicals ,,z ,,dis9fectants ,,& ,,pres]vatives ,,xxv4 ,,drugs ,,& ,,pat5t ,,m$ic9es ,,xxvi4 ,,nitrog5 ,,& ,,its ,,relation ,,to ,,plants ,,xxvii4 ,,s\nd ,,xxviii4 ,,musical ,,in/rum5ts ,,xxix4 ,,speak+ ,,& ,,he>+ ,,xxx4 ,,electricity ,,xxxi4 ,,"s ,,uses ,,( ,,electricity ,,xxxii4 ,,mod]n ,,electrical ,,inv5tions ,,xxxiii4 ,,magnets ,,& ,,curr5ts ,,xxxiv4 ,,h[ ,,electricity ,,may ,,be ,,measur$ ,,xxxv4 ,,h[ ,,electricity ,,is ,,obta9$ ,,on ,a ,,l>ge ,,scale ,,index ,,g5]al ,,sci5ce ,,*apt] ,i ,,heat ,i4 ,value ( ,fire4 ,e day1 uncontroll$ fire wipes out human lives & de/roys va/ am\nts ( prop]ty2 e day1 fire1 controll$ & regulat$ 9 /ove & furnace1 cooks our food & w>ms our h\ses4 ,fire melts ore & all[s ( ! =g+ ( iron1 z 9 ! blacksmi?'s %op1 & ( ! fa%ion+ ( innum]able objects s]viceable to man4 ,heat$ boil]s *ange wat] into ! /eam :i* drives our eng9es on l& & sea4 ,heat causes ra9 & w9d1 fog & cl\d2 heat enables vegetation to gr[ & ?us indirectly provides our food4 ,:e!r heat comes directly f ! sun or f artificial s\rces su* z coal1 wood1 oil1 or electricity1 x is vitally connect$ ) our daily life1 & = ?is reason ! facts & !ories relative to x are among ! mo/ important t c be /udi$4 ,heat1 if prop]ly regulat$ & controll$1 w\ld nev] be injuri\s to man2 h5ce 9 ! foll[+ p>agraphs heat w be consid]$ m]ely 9 its helpful capacity4 #b4 ,g5]al ,effect ( ,heat4 ,expansion & ,contraction4 ,"o ( ! be/-kn[n effects ( heat is ! *ange :i* x causes 9 ! size ( a sub/ance4 ,e h\sewife kn[s t if a kettle is fill$ ) cold wat] to beg9 )1 !re w be an ov]fl[ z soon z ! wat] becomes heat$4 ,heat causes n only wat]1 b all o!r liquids1 to occupy m space1 or to exp&1 & 9 "s cases ! expansion1 or increase 9 size1 is surpris+ly l>ge4 ,= example1 if #ajj p9ts ( ice wat] is heat$ 9 a kettle1 ! #ajj p9ts w /eadily exp& until1 at ! boil+ po9t1 x w occupy z mu* space z #ajd p9ts ( ice wat]4 ,! expansion ( wat] c be easily %[n by heat+ a flask 7,fig4 ,i7 fill$ ) wat] & clos$ by a cork ?r\gh :i* a n>r[ tube passes4 ,z ! wat] is heat$1 x exp&s & =ces its way up ! n>r[ tube4 ,if ! heat is remov$1 ! liquid cools1 contracts1 & sl[ly falls 9 ! tube1 resum+ 9 "t its orig9al size or volume4 ,a simil> obs]vation c be made ) alcohol1 m]cury1 or any o!r conv5i5t liquid4 ,illu/ration3 ,,fig4 #a4--;,z ! wat] becomes w>m] x exp&s & rise 9 ! n>r[ tube4 ,n only liquids are affect$ by heat & cold1 b solids also are subject to simil> *anges4 ,a metal ball :i* :5 cool w j slip ?r\gh a r+ 7,fig4 #b7 w1 :5 heat$1 be too l>ge to slip ?r\gh ! r+4 ,telegraph & telephone wires :i* 9 w9t] are /ret*$ taut f pole to pole1 sag 9 hot wea!r & are mu* too long4 ,9 summ] !y are expos$ to ! fi]ce rays ( ! sun1 become /rongly heat$1 & exp& suffici5tly to sag4 ,if ! wires 7 /ret*$ taut 9 ! summ]1 !re w\ld n be suffici5t leeway = ! contraction :i* accompanies cold wea!r1 & 9 w9t] !y w\ld snap4 ,illu/ration3 ,,fig4 #b--,:5 ! ball is heat$1 x become too l>ge to slip ?r\gh ! r+4 ,air exp&s greatly :5 heat$ 7,fig4 #c71 b s9ce air is practically invisible1 we are n ord9>ily consci\s ( any *ange 9 x4 ,! expansion ( air c be readily %[n by putt+ a drop ( ink 9 a ?9 glass tube1 ins]t+ ! tube 9 ! cork ( a flask1 & apply+ heat to ! flask 7,fig4 #d74 ,! ink is =c$ up ! tube by ! exp&+ air4 ,ev5 ! w>m? ( ! h& is g5]ally suffici5t to cause ! drop to rise /eadily 9 ! tube4 ,! rise ( ! drop ( ink %[s t ! air 9 ! flask occupies m space ?an =m]ly1 & s9ce ! quantity ( air has n *ang$1 ea* cubic in* ( space mu/ hold less w>m air ?an x held ( cold air2 t is1 "o cubic in* ( w>m air weighs less ?an "o cubic in* ( cold air1 or w>m air is less d5se ?an cold air4 ,all gases1 if n conf9$1 exp& :5 heat$ & contract z !y cool4 ,heat1 9 g5]al1 causes sub/ances to exp& or become less d5se4 ,illu/ration3 ,,fig4 #c--;,z ! air 9 ,a is heat$1 x exp&s & escapes 9 ! =m ( bubbles4 #c4 ,am\nt ( ,expansion & ,contraction4 ,:ile mo/ sub/ances exp& :5 heat$ & contract :5 cool$1 !y are n all affect$ equally by ! same *anges 9 temp]ature4 ,alcohol exp&s m ?an wat]1 & wat] m ?an m]cury4 ,/eel wire :i* measures #a_/d mile on a sn[y day w ga9 #be in*es 9 l5g? on a w>m summ] day1 & an alum9um wire "u ! same conditions w\ld ga9 #ej in*es 9 l5g?4 ,illu/ration3 ,,fig4 #d4--;,z ! air 9 ,a is heat$1 x exp&s & =ces ! drop ( ink up ! tube4 #d4 ,advantages & ,disadvantages ( ,expansion & ,contraction4 ,we owe ! snug fit ( metal tires & b&s to ! expansion & contraction result+ f heat+ & cool+4 ,! tire ( a wagon :eel is made slightly small] ?an ! :eel :i* x is to protect2 x is !n put into a v hot fire & heat$ until x has exp&$ suffici5tly to slip on ! :eel4 ,z ! tire cools x contracts & fits ! :eel closely4 ,9 a railroad1 spaces are usually left betwe5 consecutive rails 9 ord] to all[ = expansion dur+ ! summ]4 ,! unsightly cracks & humps 9 cem5t floors are sometimes due to ! expansion result+ f heat 7,fig4 #e74 ,crack+ f ?is cause c frequ5tly be avoid$ by cutt+ ! s(t cem5t into squ>es1 ! spaces betwe5 !m giv+ opportunity = expansion j z d ! spaces betwe5 ! rails ( railroads4 ,illu/ration3 ,,fig4 #e3 ,a cem5t walk brok5 by expansion due to sun heat4 ,9 ! con/ruction ( long wire f5ces provision mu/ be made = tight5+ ! wire 9 summ]1 o!rwise great sagg+ w\ld occur4 ,heat plays an important "p 9 ! splitt+ ( rocks & 9 ! =mation ( dbris4 ,rocks 9 expos$ places are greatly affect$ by *anges 9 temp]ature1 & 9 regions :]e ! *anges 9 temp]ature are sudd51 sev]e1 & frequ5t1 ! rocks are n able to )/& ! /ra9 ( expansion & contraction1 & z a result crack & split4 ,9 ! ,sah>a ,des]t mu* crumbl+ ( ! rock into s& has be5 caus$ by ! int5se heat ( ! day foll[$ by ! %>p fro/ ( night4 ,! heat ( ! day causes ! rocks to exp&1 & ! cold ( night causes !m to contract1 & ^! two =ces con/antly at "w loos5 ! gra9s ( ! rock & =ce !m out ( place1 ?us produc+ crumbl+4 ,illu/ration3 ,,fig4 #f4--,splitt+ & crumbl+ ( rock caus$ by alt]nat+ heat & cold4 ,! surface ( ! rock is ! mo/ expos$ "p1 & dur+ ! day ! surface1 heat$ by ! sun's rays1 exp&s & becomes too l>ge = ! int]ior1 & crumbl+ & splitt+ result f ! /ra94 ,) ! sudd5 fall ( temp]ature 9 ! late aft]noon & night1 ! surface ( ! rock becomes greatly *ill$ & cold] ?an ! rock b5ea?2 ! surface rock !re=e contracts & %r9ks m ?an ! und]ly+ rock1 & aga9 crumbl+ results 7,fig4 #f74 ,illu/ration3 ,,fig4 #g4--;,debris =m$ f crumbl$ rock4 ,on b>e m\nta9s1 ! heat+ & cool+ effects ( ! sun are v /rik+7,fig4 #g72 ! surface ( _m a m\nta9 peak is cov]$ ) crack$ rock s insecure t a t\* or /ep w dislodge ! fragm5ts & />t !m d[n ! m\nta9 slope4 ,! l[] levels ( m\nta9s are frequ5tly buri$ sev]al feet "u dbris :i* has be5 =m$ 9 ?is way f high] peaks1 & :i* has sl[ly accumulat$ at ! l[] levels4 #e4 ,temp]ature4 ,:5 an object feels hot to ! t\*1 we say t x has a high temp]ature2 :5 x feels cold to ! t\*1 t x has a l[ temp]ature2 b we are n accurate judges ( heat4 ,ice wat] seems comp>atively w>m aft] eat+ ice cream1 & yet we "k t ice wat] is by no means w>m4 ,a room may seem w>m to a p]son :o has be5 walk+ 9 ! cold air1 :ile x may feel decid$ly cold to "s "o :o has come f a w>m] room4 ,if ! h& is cold1 lukew>m wat] feels hot1 b if ! h& has be5 9 v hot wat] & is !n transf]r$ to lukew>m wat]1 ! latt] w seem cold4 ,we see t ! s5sation or feel+ ( w>m? is n an accurate guide to ! temp]ature ( a sub/ance2 & yet until #aeib1 "o hundr$ ye>s aft] ! discov]y ( ,am]ica1 p reli$ solely ^u _! s5sations = ! measurem5t ( temp]ature4 ,v hot sub/ances _c be t\*$ )\t injury1 & h5ce inconv5i5ce z well z ! necessity = accuracy l$ to ! inv5tion ( ! !rmomet]1 an in/rum5t ^: op]ation dep5ds ^u ! fact t mo/ sub/ances exp& :5 heat$ & contract :5 cool$4 ,illu/ration3 ,,fig4 #h4--,mak+ a !rmomet]4 #f4 ,! ,!rmomet]4 ,! mod]n !rmomet] consi/s ( a glass tube at ! l[] end ( :i* is a bulb fill$ ) m]cury or color$ alcohol 7,fig4 #h74 ,aft] ! bulb has be5 fill$ ) ! m]cury1 x is plac$ 9 a beak] ( wat] & ! wat] is heat$ by a ,buns5 burn]4 ,z ! wat] becomes w>m] & w>m] ! level ( ! m]cury 9 ! tube /eadily rises until ! wat] boils1 :5 ! level rema9s /ation>y 7,fig4 #i74 ,a scrat* is made on ! tube to indicate ! po9t to :i* ! m]cury rises :5 ! bulb is plac$ 9 boil+ wat]1 & ?is po9t is m>k$ #bab4 ,! tube is !n remov$ f ! boil+ wat]1 & aft] cool+ = a few m9utes1 x is plac$ 9 a vessel conta9+ f9ely *opp$ ice 7,fig4 #aj74 ,! m]cury column falls rapidly1 b f9ally rema9s /ation>y1 & at ?is level ano!r scrat* is made on ! tube & ! po9t is m>k$ #cb4 ,! space betwe5 ^! two po9ts1 :i* repres5t ! temp]atures ( boil+ wat] & ( melt+ ice1 is divid$ into #ahj equal p>ts call$ degrees4 ,! !rmomet] 9 use 9 ! ,unit$ ,/ates is m>k$ 9 ?is way & is call$ ! ,fahr5heit !rmomet] aft] its design]4 ,be=e ! degrees are et*$ on ! !rmomet] ! op5 end ( ! tube is seal$4 ,illu/ration3 ,,fig4 #i4--;,det]m9+ "o ( ! fix$ po9ts ( a !rmomet]4 ,! ,c5tigrade !rmomet]1 9 use 9 =eign c\ntries & 9 all sci5tific "w1 is simil> to ! ,fahr5heit except t ! fix$ po9ts are m>k$ #ajj & #j1 & ! int]val betwe5 ! po9ts is divid$ into #ajj equal p>ts in/ead ( into #ahj4 ,! boil+ po9t ( wat] is #bab ,f4 or #ajj ,c4 ,! melt+ po9t ( ice is #cb ,f4 or #j ,c4 ,glass !rmomet]s ( ! above type are ! ones mo/ g5]ally us$1 b !re are _m diff]5t types = special purposes4 ,illu/ration3 ,,fig4 #aj4--;,det]m9+ ! l[] fix$ po9t ( a !rmomet]4 #g4 ,"s ,uses ( a ,!rmomet]4 ,"o ( ! *ief values ( a !rmomet] is ! s]vice x has r5d]$ to m$ic9e4 ,if a !rmomet] is held = a few m9utes "u ! tongue ( a normal1 heal?y p]son1 ! m]cury w rise to ab\t #ih4d ,f4 ,if ! temp]ature ( ! body regi/]s sev]al degrees above or bel[ ?is po9t1 a physician %\ld be consult$ imm$iately4 ,! temp]ature ( ! body is a tru/wor?y indicator ( g5]al physical condition2 h5ce 9 all hospitals ! temp]ature ( pati5ts is c>efully tak5 at /at$ int]vals4 ,comm]cially1 temp]ature read+s are extremely important4 ,9 sug> ref9]ies ! temp]ature ( ! heat$ liquids is obs]v$ mo/ c>efully1 s9ce a diff]5ce 9 temp]ature1 h[ev] slight1 affects n only ! g5]al appe>ance ( sug>s & sirups1 b ! quality z well4 ,! _m v>ieties ( /eel likewise %[ ! influ5ce :i* heat may h on ! nature ( a sub/ance4 ,by obs]vation & t$i\s exp]im5tation x has be5 f\nd t if h>d5$ /eel is heat$ to ab\t #dej ,f4 & quickly cool$1 x gives ! f9e cutt+ edge ( razors2 if x is heat$ to ab\t #ejj ,f4 & !n cool$1 ! metal is mu* co>s] & is suitable = %e>s & f>m implem5ts2 :ile if x is heat$ b #ej ,f4 high]1 t is1 to #eej ,f41 x gives ! f9e ela/ic /eel ( wat* spr+s4 ,illu/ration3 ,,fig4 #aa4--;,a well-made comm]cial !rmomet]4 ,a !rmomet] c\ld be put to good use 9 e kit*52 ! inexp]i5c$ h\sekeep] :o _c judge ( ! heat ( ! ov5 w\ld be sav$ bad bread1 etc41 if ! !rmomet] 7 a "p ( h] equipm5t4 ,! !rmomet] c also be us$ 9 detect+ adult]ants4 ,butt] %\ld melt at #id ,f42 if x does n1 y may be sure t x is adult]at$ ) suet or o!r *eap fat4 ,olive oil %\ld be a cle> liquid above #ge ,f42 if1 above ?is temp]ature1 x looks cl\dy1 y may be sure t x too is adult]at$ ) fat4 #h4 ,me?ods ( ,heat+ ,build+s4 ,op5 ,fireplaces & ,/oves4 ,be=e ! "t ( /oves & furnaces1 man heat$ 8 mode/ dwell+ by op5 fires alone4 ,! burn+ logs gave w>m? to ! cab9 & s]v$ z a primitive cook+ ag5t2 & ! smoke :i* usually accompanies burn+ bodies 0 c>ri$ away by means ( ! *imney4 ,b 9 an op5 fireplace mu* heat escapes ) ! smoke & is lo/1 & only a small portion /reams into ! room & gives w>m?4 ,:5 fuel is plac$ 9 an op5 fireplace 7,fig4 #ab7 & light$1 ! air imm$iately surr\nd+ ! fire becomes w>m] &1 because ( expansion1 becomes light] ?an ! cold air above4 ,! cold air1 be+ heavi]1 falls & =ces ! w>m] air upw>d1 & along ) ! w>m air goes ! disagreeable smoke4 ,! fall ( ! cold] & heavi] air1 & ! rise ( ! w>m] & h5ce light] air1 is simil> to ! ex*ange :i* takes place :5 wat] is p\r$ on oil2 ! wat]1 be+ heavi] ?an oil1 s9ks to ! bottom & =ces ! oil to ! surface4 ,! w>m] air :i* escapes up ! *imney c>ries ) x ! disagreeable smoke1 & :5 all ! smoke is got rid ( 9 ?is way1 ! *imney is said to draw well4 ,illu/ration3 ,,fig4 #ab4--,! op5 fireplace z an e>ly me?od ( heat+4 ,z ! air is heat$ by ! fire x exp&s1 & is pu%$ up ! *imney by ! cold air :i* is con/antly ent]+ ?r\gh loose w9d[s & doors4 ,op5 fireplaces are v heal?ful because ! air :i* is driv5 out is impure1 :ile ! air :i* ru%es 9 is fre% & br+s oxyg5 to ! human be+4 ,b op5 fireplaces1 :ile pleasant to look at1 are n effici5t = ei!r heat+ or cook+4 ,! possibilities = ! latt] are especially limit$1 & ! inv5tion ( /oves 0 a great advance 9 effici5cy1 economy1 & com=t4 ,a /ove is a receptacle = fire1 provid$ ) a def9ite inlet = air & a def9ite outlet = smoke1 & able to radiate into ! room mo/ ( ! heat produc$ f ! fire :i* burns )94 ,! inlet1 or draft1 admits en\gh air to cause ! fire to burn brightly or sl[ly z ! case may be4 ,if we wi% a hot fire1 ! draft is op5$ wide & en\gh air ent]s to produce a /rong gl[4 ,if we wi% a l[ fire1 ! inlet is only p>tially op5$1 & j en\gh air ent]s to keep ! fuel smold]+4 ,:5 ! fire is />t$1 ! damp] %\ld be op5$ wide 9 ord] to all[ ! escape ( smoke2 b aft] ! fire is well />t$ !re is less smoke1 & ! damp] may be p>tly clos$4 ,if ! damp] is kept op51 coal is rapidly consum$1 & ! additional heat passes out ?r\gh ! *imney1 & is lo/ to use4 #i4 ,furnaces4 ,hot ,air4 ,! labor involv$ 9 ! c>e ( num]\s /oves is consid]able1 & h5ce ! adv5t ( a c5tral heat+ /ove1 or furnace1 0 a great sav+ 9 /r5g? & fuel4 ,a furnace is a /ove arrang$ z 9 ,figure #ac4 ,! /ove ,s1 l all o!r /oves1 has an inlet = air & an outlet ,c = smoke2 b 9 addition1 x has built ar\nd x a *amb] 9 :i* air circulates & is w>m$4 ,! air w>m$ by ! /ove is =c$ upw>d by cold air :i* ent]s f outside4 ,= example1 cold air con/antly ent]+ at ,e drives ! air heat$ by ,s ?r\gh pipes & ducts to ! rooms to be heat$4 ,! metal pipes :i* convey ! heat$ air f ! furnace to ! ducts are sometimes cov]$ ) felt1 asbe/os1 or o!r non-conduct+ mat]ial 9 ord] t heat may n be lo/ dur+ transmission4 ,! ducts :i* receive ! heat$ air f ! pipes are built 9 ! non-conduct+ walls ( ! h\se1 & h5ce lose practically no heat4 ,! air :i* rea*es halls & rooms is !re=e w>m1 9 spite ( its long j\rney f ! cell>4 ,illu/ration3 ,,fig4 #ac4--;,a furnace4 ,pipes conduct hot air to ! rooms4 ,n only h\ses are w>m$ by a c5tral heat+ /ove1 b :ole communities sometimes dep5d ^u a c5tral heat+ plant4 ,9 ! latt] case1 pipes closely wrapp$ ) a non-conduct+ mat]ial c>ry /eam long di/ances und]gr\nd to heat remote build+s4 ,ov]brook & ,radnor1 ,pa41 are t[ns 9 :i* su* a sy/em is us$4 #aj4 ,hot-wat] ,heat+4 ,! heat$ air :i* rises f furnaces is seldom hot en\gh to w>m l>ge build+s well2 h5ce furnace heat+ is be+ l>gely supplant$ by hot-wat] heat+4 ,! pr9ciple ( hot-wat] heat+ is %[n by ! foll[+ simple exp]im5t4 ,two flasks & two tubes are arrang$ z 9 ,figure #ae1 ! upp] flask conta9+ a color$ liquid & ! l[] flask cle> wat]4 ,if heat is appli$ to ,b1 "o c see at ! end ( a few seconds ! d[nw>d circulation ( ! color$ liquid & ! upw>d circulation ( ! cle> wat]4 ,if we repres5t a boil] by ,b1 a radiator by ! coil$ tube1 & a safety tank by ,c1 we %all h a v fair illu/ration ( ! pr9ciple ( a hot-wat] heat+ sy/em4 ,! hot wat] 9 ! radiators cools &1 9 cool+1 gives up its heat to ! rooms & ?us w>ms !m4 ,illu/ration3 ,,fig4 #ad4--;,hot-wat] heat+4 ,9 hot-wat] heat+ sy/ems1 fre% air is n br\ght to ! rooms1 = ! radiators are clos$ pipes conta9+ hot wat]4 ,x is l>gely = ?is reason t ?\ghtful p are c>eful to raise w9d[s at int]vals4 ,"s sy/ems ( hot-wat] heat+ secure v5tilation by conf9+ ! radiators to ! basem5t1 to :i* cold air f outside is con/antly admitt$ 9 su* a way t x circulates ov] ! radiators & becomes /rongly heat$4 ,?is w>m fre% air !n passes ?r\gh ord9>y flues to ! rooms above4 ,illu/ration3 ,,fig4 #ae4--,! pr9ciple ( hot-wat] heat+4 ,9 ,figure #af1 a radiator is %[n 9 a boxlike /ructure 9 ! cell>4 ,fre% air f outside ent]s a flue at ! "r1 passes ! radiator1 :]e x is w>m$1 & !n makes its way to ! room ?r\gh a flue at ! left4 ,! w>m air :i* ?us ent]s ! room is ?or\ghly fre%4 ,! actual labor involv$ 9 furnace heat+ & 9 hot-wat] heat+ is practically ! same1 s9ce coal mu/ be f$ to ! fire1 & a%es mu/ be remov$2 b ! hot-wat] sy/em has ! advantage ( economy & cleanl9ess4 ,illu/ration3 ,,fig4 #af4--;,fre% air f outside circulates ov] ! radiators & !n rises into ! rooms to be heat$4 #aa4 ,fre% ,air4 ,fre% air is ess5tial to normal heal?y liv+1 & #bjjj cubic feet ( air p] h\r is desirable = ea* individual4 ,if a g5tle breeze is bl[+1 a b>ely p]ceptible op5+ ( a w9d[ w give ! ne$$ am\nt1 ev5 if !re are no additional drafts ( fre% air into ! room ?r\gh cracks4 ,mo/ h\ses are s loosely con/ruct$ t fre% air ent]s imp]ceptibly 9 _m ways1 & :e!r we w or no1 we receive "s fre% air4 ,! supply is1 h[ev]1 nev] suffici5t 9 itself & %\ld n be dep5d$ ^u alone4 ,at night1 or at any o!r "t :5 gas lights are requir$1 ! ne$ = v5tilation increases1 because e gas light 9 a room uses up ! same am\nt ( air z f\r p4 ,illu/ration3 ,,fig4 #ag4--,! air :i* goes to ! s*oolrooms is w>m$ by passage ov] ! radiators4 ,9 ! prec$+ ,section1 we le>n$ t _m h\ses heat$ by hot wat] are suppli$ ) fre%-air pipes :i* admit fre% air into sep>ate rooms or into suites ( rooms4 ,9 "s cases ! am\nt :i* ent]s is s great t ! air 9 a room is *ang$ ?ree or f\r times an h\r4 ,! con/ant infl[ ( cold air & exit ( w>m air necessitates l>g] radiators & m hot wat] & h5ce m coal to heat ! l>g] quantity ( wat]1 b ! additional exp5se is m ?an comp5sat$ by ! ga9 9 heal?4 #ab4 ,w9ds & ,curr5ts4 ,! g5tle/ summ] breezes & ! fi]ce/ bla/s ( w9t] are produc$ by ! unequal heat+ ( air4 ,we h se5 t ! air ne>e/ to a /ove or hot object becomes hott] ?an ! adjac5t air1 t x t5ds to exp& & is replac$ & pu%$ upw>d & outw>d by cold]1 heavi] air fall+ d[nw>d4 ,we h le>n$ also t ! mov+ liquid or gas c>ries ) x heat :i* x gradually gives out to surr\nd+ bodies4 ,:5 a liquid or a gas moves away f a hot object1 c>ry+ heat ) x1 ! process is call$ convection4 ,convection is responsible = w9ds & ocean curr5ts1 = l& & sea breezes1 & o!r daily ph5om5a4 ,! ,gulf ,/ream illu/rates ! transf]5ce ( heat by convection4 ,a l>ge body ( wat] is /rongly heat$ at ! equator1 & !n moves away1 c>ry+ heat ) x to di/ant regions1 su* z ,engl& & ,norway4 ,ow+ to ! %ape ( ! e>? & its position ) respect to ! sun1 diff]5t portions ( ! e>? are unequally heat$4 ,9 ^? portions :]e ! e>? is greatly heat$1 ! air likewise w be heat$2 !re w be a t5d5cy = ! air to rise1 & = ! cold air f surr\nd+ regions to ru% 9 to fill its place4 ,9 ?is way w9ds are produc$4 ,!re are _m circum/ances :i* modify w9ds & curr5ts1 & x is n always easy to expla9 _! direction & velocity1 b "o v def9ite cause is ! unequal heat+ ( ! surface ( ! e>?4 #ac4 ,conduction4 ,a pok] us$ 9 /irr+ a fire becomes hot & heats ! h& grasp+ ! pok]1 al?\gh only ! opposite end ( ! pok] has actually be5 9 ! fire4 ,heat f ! fire pass$ into ! pok]1 travel$ along x1 & w>m$ x4 ,:5 heat fl[s 9 ?is way f a w>m "p ( a body to a cold] "p1 ! process is call$ conduction4 ,a flatiron is heat$ by conduction1 ! heat f ! w>m /ove pass+ into ! cold flatiron & gradually heat+ x4 ,9 convection1 air & wat] circulate freely1 c>ry+ heat ) !m2 9 conduction1 heat fl[s f a w>m region t[>d a cold region1 b !re is no app>5t motion ( any k9d4 ,heat travels m readily ?r\gh "s sub/ances ?an ?r\gh o!rs4 ,all metals conduct heat well2 irons plac$ on ! fire become heat$ ?r\gh\t & _c be grasp$ ) ! b>e h&2 iron ut5sils are frequ5tly made ) wood5 h&les1 because wood is a poor conductor & does n all[ heat f ! iron to pass ?r\gh x to ! h&4 ,= ! same reason a burn+ mat* may be held )\t discom=t until ! flame almo/ rea*es ! h&4 ,/oves & radiators are made ( metal1 because metals conduct heat readily1 & z fa/ z heat is g5]at$ )9 ! /ove by ! burn+ ( fuel1 or introduc$ into ! radiator by ! hot wat]1 ! heat is conduct$ ?r\gh ! metal & escapes into ! room4 ,hot-wat] pipes & /eam pipes are usually wrapp$ ) a non-conduct+ sub/ance1 or insulator1 su* z asbe/os1 9 ord] t ! heat may n escape1 b %all be reta9$ )9 ! pipes until x rea*es ! radiators )9 ! rooms4 ,! inv5tion ( ! ,fireless ,cook] dep5d$ 9 "p ^u ! pr9ciple ( non-conduction4 ,two vessels1 "o inside ! o!r1 are sep>at$ by sawdu/1 asbe/os1 or o!r poor conduct+ mat]ial 7,fig4 #ah74 ,foods are heat$ 9 ! usual way to ! boil+ po9t or to a high temp]ature1 & are !n plac$ 9 ! inn] vessel4 ,! heat ( ! food _c escape ?r\gh ! non-conduct+ mat]ial :i* surr\nds x1 & h5ce rema9s 9 ! food & sl[ly cooks x4 ,illu/ration3 ,,fig4 #ah4--;,a fireless cook]4 ,a v int]e/+ exp]im5t = ! te/+ ( ! efficacy ( non-conductors may be easily p]=m$4 ,place hot wat] 9 a metal vessel1 & note by means ( a !rmomet] ! rapidity ) :i* ! wat] cools2 !n place wat] ( ! same temp]ature 9 a second metal vessel simil> to ! fir/1 b surr\nd$ by asbe/os or o!r non-conduct+ mat]ial1 & note ! sl[ness ) :i* ! temp]ature falls4 ,*emical ,*ange1 an ,effect ( ,heat4 ,?is effect ( heat has a vital influ5ce on our lives1 because ! *anges :i* take place :5 food is cook$ are due to x4 ,! d\ghy mass :i* goes into ! ov51 comes out a light spongy loaf2 ! small indige/ible rice gra9 comes out ! swoll51 fluffy1 dige/ible gra94 ,7 x n = ! *emical *anges br\ght ab\t by heat1 _m ( our pres5t foods w\ld be useless to man4 ,hundr$s ( common mat]ials l glass1 rubb]1 iron1 alum9um1 etc41 are manufactur$ by processes :i* involve *emical action caus$ by heat4 ,,*apt] ,,ii ,,temp]ature ,,& ,,heat #ad4 ,temp]ature n a ,measure ( ! ,am\nt ( ,heat ,pres5t4 ,if two simil> bas9s conta9+ unequal quantities ( wat] are plac$ 9 ! sun%9e on a summ] day1 ! small] quantity ( wat] w become q w>m 9 a %ort p]iod ( "t1 :ile ! l>g] quantity w become only lukew>m4 ,bo? vessels receive ! same am\nt ( heat f ! sun1 b 9 "o case ! heat is utiliz$ 9 heat+ to a high temp]ature a small quantity ( wat]1 :ile 9 ! second case ! heat is utiliz$ 9 w>m+ to a l[] degree a l>g] quantity ( wat]4 ,equal am\nts ( heat d n necess>ily produce equival5t temp]atures1 & equal temp]atures d n necess>ily indicate equal am\nts ( heat4 ,x takes m heat to raise a gallon ( wat] to ! boil+ po9t ?an x does to raise a p9t ( wat] to ! boil+ po9t1 b a !rmomet] w\ld regi/] ! same temp]ature 9 ! two cases4 ,! temp]ature ( boil+ wat] is #ajj ,c4 :e!r !re is a p9t ( x or a gallon4 ,temp]ature is indep5d5t ( ! quantity ( matt] pres5t2 b ! am\nt ( heat conta9$ 9 a sub/ance at any temp]ature is n indep5d5t ( quantity1 be+ great] 9 ! l>g] quantity4 #ae4 ,! ,unit ( ,heat4 ,x is necess>y to h a unit ( heat j z we h a unit ( l5g?1 or a unit ( mass1 or a unit ( "t4 ,"o unit ( heat is call$ a calorie1 & is ! am\nt ( heat :i* w *ange ! temp]ature ( #a gram ( wat] #a ,c4 ,x is ! am\nt ( heat giv5 out by #a gram ( wat] :5 its temp]ature falls #a ,c41 or ! am\nt ( heat absorb$ by #a gram ( wat] :5 its temp]ature rises #a ,c4 ,if #djj grams ( wat] are heat$ f #j to #e ,c41 ! am\nt ( heat :i* has ent]$ ! wat] is equival5t to #e #djj or #bjjj calories2 if #bjj grams ( wat] cool f #be to #bj ,c41 ! heat giv5 out by ! wat] is equival5t to #e #bjj or #ajjj calories4 #af4 ,"s ,sub/ances ,heat m readily ?an ,o!rs4 ,if two equal quantities ( wat] at ! same temp]ature are expos$ to ! sun = ! same l5g? ( "t1 _! f9al temp]atures w be ! same4 ,if1 h[ev]1 equal quantities ( diff]5t sub/ances are expos$1 ! temp]atures result+ f ! heat+ w n necess>ily be ! same4 ,if a bas9 conta9+ #a lb4 ( m]cury is put on ! fire1 side by side ) a bas9 conta9+ an equal quantity ( wat]1 ! temp]atures ( ! two sub/ances w v>y greatly at ! end ( a %ort "t4 ,! m]cury w h a f> high] temp]ature ?an ! wat]1 9 spite ( ! fact t ! am\nt ( m]cury is z great z ! am\nt ( wat] & t ! heat receiv$ f ! fire has be5 ! same 9 ea* case4 ,m]cury is n s difficult to heat z wat]2 less heat be+ requir$ to raise its temp]ature #a ?an is requir$ to raise ! temp]ature ( an equal quantity ( wat] #a4 ,9 fact1 m]cury is #cj times z easy to heat z wat]1 & x requires only "o ?irtie? z mu* fire to heat a giv5 quantity ( m]cury #a z to heat ! same quantity ( wat] #a4 #ag4 ,specific ,heat4 ,we "k t diff]5t sub/ances are diff]5tly affect$ by heat4 ,"s sub/ances1 l wat]1 *ange _! temp]ature sl[ly :5 heat$2 o!rs1 l m]cury1 *ange _! temp]ature v rapidly :5 heat$4 ,! numb] ( calories ne$$ by #a gram ( a sub/ance 9 ord] t its temp]ature may be increas$ #a ,c4 is call$ ! specific heat ( a sub/ance2 or1 specific heat is ! numb] ( calories giv5 out by #a gram ( a sub/ance :5 its temp]ature falls #a ,c4 ,= exp]im5ts on ! det]m9ation ( specific heat1 see ,laboratory ,manual4 ,wat] has ! highe/ specific heat ( any kn[n sub/ance except hydrog52 t is1 x requires m heat to raise ! temp]ature ( wat] a def9ite numb] ( degrees ?an x does to raise ! temp]ature ( an equal am\nt ( any o!r sub/ance ! same numb] ( degrees4 ,practically ?is same ?+ c be /at$ 9 ano!r way3 ,wat] 9 cool+ gives out m heat ?an any o!r sub/ance 9 cool+ ?r\gh ! same numb] ( degrees4 ,= ?is reason wat] is us$ 9 foot w>m]s & 9 hot-wat] bags4 ,if a copp] lid 7 us$ z a foot w>m]1 x w\ld give ! feet only 4#jie z mu* heat z an equal weight ( wat]2 a lead weight only 4#jca z mu* heat z wat]4 ,flatirons are made ( iron because ( ! relatively high specific heat ( iron4 ,! flatiron heats sl[ly & cools sl[ly1 &1 because ( its high specific heat1 n only supplies ! laundress ) consid]able heat1 b elim9ates = h] ! frequ5t *ang+ ( ! flatiron4 #ah4 ,wat] & ,wea!r4 ,ab\t f\r times z mu* heat is requir$ to heat a giv5 quantity ( wat] "o degree z to heat an equal quantity ( e>?4 ,9 summ]1 :5 ! rocks & ! s& along ! %ore are burn+ hot1 ! ocean & lakes are pleasantly cool1 al?\gh ! am\nt ( heat pres5t 9 ! wat] is z great z t pres5t 9 ! e>?4 ,9 w9t]1 long aft] ! rocks & s& h giv5 out _! heat & h become cold1 ! wat] cont9ues to give out ! va/ /ore ( heat accumulat$ dur+ ! summ]4 ,?is expla9s :y l&s situat$ on or ne> l>ge bodies ( wat] usually h less v>iation 9 temp]ature ?an inl& regions4 ,9 ! summ] ! wat] cools ! region2 9 ! w9t]1 on ! contr>y1 ! wat] heats ! region1 & h5ce extremes ( temp]ature are practically unkn[n4 #ai4 ,s\rces ( ,heat4 ,mo/ ( ! heat :i* we enjoy & use we owe to ! sun4 ,! wood :i* blazes on ! he>?1 ! coal :i* gl[s 9 ! furnace1 & ! oil :i* burns 9 ! /ove owe _! exi/5ce to ! sun4 ,)\t ! w>m? ( ! sun se$s c\ld n spr\t & develop into ! mighty trees :i* yield firewood4 ,ev5 coal1 :i* lies buri$ ?\s&s ( feet bel[ ! e>?'s surface1 owes its exi/5ce 9 "p to ! sun4 ,coal is simply buri$ vegetation1--vegetation :i* spr\t$ & grew "u ! influ5ce ( ! sun's w>m rays4 ,ages ago trees & bu%es grew ?ick & fa/1 & ! gr\nd 0 always cov]$ ) a deep lay] ( decay+ vegetable matt]4 ,9 "t "s ( ?is va/ supply sank into ! moi/ soil & became cov]$ ) mud4 ,!n rock =m$1 & ! rock press$ d[n ^u ! sunk5 vegetation4 ,! con/ant pressure1 ! moi/ure 9 ! gr\nd1 & heat affect$ ! und]gr\nd vegetable mass1 & sl[ly *ang$ x into coal4 ,! buri$ =e/ & ?ickets 7 n all *ang$ into coal4 ,"s 7 *ang$ into oil & gas4 ,decay+ animal matt] 0 (t5 mix$ ) ! vegetable mass4 ,:5 ! m+l$ animal & vegetable matt] sank into moi/ e>? & came "u ! influ5ce ( pressure1 x 0 sl[ly *ang$ into oil & gas4 ,! heat ( our bodies comes f ! foods :i* we eat4 ,fruits1 gra91 etc41 c\ld n gr[ )\t ! w>m? & ! light ( ! sun4 ,! animals :i* supply our meats likewise dep5d ^u ! sun = light & w>m?4 ,! sun1 !re=e1 is ! great s\rce ( heat2 :e!r x is ! heat :i* comes directly f ! sun & w>ms ! atmosph]e1 or ! heat :i* comes f burn+ coal1 wood1 & oil4 ,,*apt] ,,iii ,,o!r ,,facts ,,ab\t ,,heat #bj4 ,boil+4 ,heat absorb$ 9 ,boil+4 ,if a kettle ( wat] is plac$ above a flame1 ! temp]ature ( ! wat] gradually increases1 & soon small bubbles =m at ! bottom ( ! kettle & beg9 to rise ?r\gh ! wat]4 ,at fir/ ! bubbles d n get f> 9 _! asc5t1 b disappe> be=e !y rea* ! surface2 lat]1 z ! wat] gets hott] & hott]1 ! bubbles become l>g] & m num]\s1 rise high] & high]1 & f9ally rea* ! surface & pass f ! wat] into ! air2 /eam comes f ! vessel1 & ! wat] is said to boil4 ,! temp]ature at :i* a liquid boils is call$ ! boil+ po9t4 ,:ile ! wat] is heat+1 ! temp]ature /eadily rises1 b z soon z ! wat] beg9s to boil ! !rmomet] read+ becomes /ation>y & does n *ange1 no matt] h[ h>d ! wat] boils & 9 spite ( ! fact t heat f ! flame is con/antly pass+ into ! wat]4 ,if ! flame is remov$ f ! boil+ wat] = b a second1 ! boil+ ceases2 if ! flame is replac$1 ! boil+ beg9s aga9 imm$iately4 ,unless heat is con/antly suppli$1 wat] at ! boil+ po9t _c be trans=m$ into /eam4 ,! numb] ( calories :i* mu/ be suppli$ to #a gram ( wat] at ! boil+ po9t 9 ord] to *ange x into /eam at ! same temp]ature is call$ ! heat ( vaporization2 x is ! heat necess>y to *ange #a gram ( wat] at ! boil+ po9t into /eam ( ! same temp]ature4 #ba4 ,! ,am\nt ( ,heat ,absorb$4 ,! am\nt ( heat :i* mu/ be con/antly suppli$ to wat] at ! boil+ po9t 9 ord] to *ange x into /eam is f> great] ?an we realize4 ,if we put a beak] ( ice wat] 7wat] at #j ,c47 ov] a /eady flame1 & note 7#a7 ! "t :i* elapses be=e ! wat] beg9s to boil1 & 7#b7 ! "t :i* elapses be=e ! boil+ wat] completely boils away1 we %all see t x takes ab\t #e-a_/d times z long to *ange wat] into /eam z x does to *ange its temp]ature f #j ,c4 to #ajj ,c4 ,s9ce1 ) a /eady flame1 x takes #e-a_/d times z long to *ange wat] into /eam z x does to *ange its temp]ature f #j ,c4 to ! boil+ po9t1 we conclude t x takes #e-a_/d times z mu* heat to conv]t wat] at ! boil+ po9t into /eam z x does to raise x f ! temp]ature ( ice wat] to t ( boil+ wat]4 ,! am\nt ( heat necess>y to raise ! temp]ature ( #a gram ( wat] #a ,c4 is equal to #a calorie1 & ! am\nt necess>y to raise ! temp]ature #ajj ,c4 is equal to #ajj calories2 h5ce ! am\nt ( heat necess>y to conv]t #a gram ( wat] at ! boil+ po9t into /eam at t same temp]ature is equal to approximately #ebe calories4 ,v c>eful exp]im5ts %[ ! exact heat ( vaporization to be #ecf4a calories4 7,see ,laboratory ,manual47 #bb4 ,g5]al ,tru?s4 ,/atem5ts simil> to ! above hold = o!r liquids & = solutions4 ,if milk is plac$ ^u a /ove1 ! temp]ature rises /eadily until ! boil+ po9t is rea*$2 fur!r heat+ produces1 n a *ange 9 temp]ature1 b a *ange ( ! wat] ( ! milk into /eam4 ,z soon z ! milk1 or any o!r liquid food1 comes to a boil1 ! gas flame %\ld be l[]$ until only an occasional bubble =ms1 because s long z any bubbles =m ! temp]ature is t ( ! boil+ po9t1 & fur!r heat m]ely results 9 wa/e ( fuel4 ,we f9d by exp]im5t t e liquid has its own specific boil+ po9t2 = example1 alcohol boils at #gh ,c4 & br9e at #ajc ,c4 ,bo? specific heat & ! heat ( vaporization v>y ) ! liquid us$4 #bc4 ,cond5sation4 ,if "o holds a cold lid 9 ! /eam ( boil+ wat]1 drops ( wat] ga!r on ! lid2 ! /eam is cool$ by contact ) ! cold lid & cond5ses into wat]4 ,bottles ( wat] br\ght f a cold cell> into a w>m room become cov]$ ) a mi/ ( f9e drops ( wat]1 because ! moi/ure 9 ! air1 *ill$ by contact ) ! cold bottles1 imm$iately cond5ses into drops ( wat]4 ,glasses fill$ ) ice wat] %[ a simil> mi/4 ,9 ,section #ba1 we saw t #ecf calories are requir$ to *ange #a gram ( wat] into /eam2 if1 n[1 ! /eam 9 turn cond5ses into wat]1 x is natural to expect a release ( ! heat us$ 9 trans=m+ wat] into /eam4 ,exp]im5t %[s n only t vapor gives out heat dur+ cond5sation1 b t ! am\nt ( heat ?us set free is exactly equal to ! am\nt absorb$ dur+ vaporization4 7,see ,laboratory ,manual47 ,we le>n t ! heat ( vaporization is ! same :e!r x is consid]$ z ! heat absorb$ by #a gram ( wat] 9 its *ange to /eam1 or z ! heat giv5 out by #a gram ( /eam dur+ its cond5sation into wat]4 #bd4 ,practical ,application4 ,we und]/& n[ ! value ( /eam z a heat+ ag5t4 ,wat] is heat$ 9 a boil] 9 ! cell>1 & ! /eam passes ?r\gh pipes :i* run to ! v>i\s rooms2 !re ! /eam cond5ses into wat] 9 ! radiators1 ea* gram ( /eam sett+ free #ecf calories ( heat4 ,:5 we consid] ! size ( ! radiators & ! l>ge numb] ( grams ( /eam :i* !y conta91 & consid] fur!r t ea* gram 9 cond5s+ sets free #ecf calories1 we und]/& ! ease ) :i* build+s are heat$ by /eam4 ,mo/ ( u h at times pr(it$ by ! heat ( cond5sation4 ,9 cold wea!r1 :5 !re is a ro>+ fire 9 ! range1 ! wat] frequ5tly becomes s hot t x /eams out ( op5 faucets4 ,if1 at su* times1 ! hot wat] is turn$ on 9 a small cold ba?room1 & is all[$ to run until ! tub is well fill$1 vapor cond5ses on w9d[s1 mirrors1 & walls1 & ! cold room becomes p]ceptibly w>m]4 ,! heat giv5 out by ! cond5s+ /eam passes into ! surr\nd+ air & w>ms ! room4 ,!re is1 h[ev]1 ano!r reason = ! rise 9 temp]ature4 ,if a l>ge pail ( hot s\p is plac$ 9 a l>g] pail ( cold wat]1 ! s\p w gradually cool & ! cold wat] w gradually become w>m]4 ,a r$-hot iron plac$ on a /& gradually cools1 b w>ms ! /&4 ,a hot body loses heat s long z a cool] body is ne> x2 ! cold object is heat$ at ! exp5se ( ! w>m] object1 & "o loses heat & ! o!r ga9s heat until ! temp]ature ( bo? is ! same4 ,n[ ! hot wat] 9 ! tub gradually loses heat & ! cold air ( ! room gradually ga9s heat by convection1 b ! am\nt giv5 ! room by convection is relatively small comp>$ ) ! l>ge am\nt set free by ! cond5s+ /eam4 #be4 ,di/illation4 ,if impure1 muddy wat] is boil$1 drops ( wat] w collect on a cold plate held 9 ! pa? ( ! /eam1 b ! drops w be cle> & pure4 ,:5 impure wat] is boil$1 ! /eam f x does n conta9 any ( ! impurities because ^! are left beh9d 9 ! vessel4 ,if all ! wat] 7 all[$ to boil away1 a lay] ( mud or ( o!r impurities w\ld be f\nd at ! bottom ( ! vessel4 ,because ( ?is fact1 x is possible to purify wat] 9 a v simple way4 ,place ov] a fire a l>ge kettle clos$ except = a sp\t :i* is long en\gh to rea* across ! /ove & dip into a bottle4 ,z ! liquid boils1 /eam escapes ?r\gh ! sp\t1 & on rea*+ ! cold bottle cond5ses & drops into ! bottle z pure wat]4 ,! impurities rema9 beh9d 9 ! kettle4 ,wat] fre$ f impurities 9 ?is way is call$ di/ill$ wat]1 & ! process is call$ di/illation 7,fig4 #ai74 ,by ?is me?od1 ! salt wat] ( ! ocean may be sep>at$ into pure dr9k+ wat] & salt1 & _m ( ! l>ge ocean l9]s di/ill f ! br9y deep all ! dr9k+ wat] us$ on _! ocean voyages4 ,illu/ration3 ,,fig4 #ai4--;,9 ord] t ! /eam :i* passes ?r\gh ! coil$ tube may be quickly cool$ & cond5s$1 cold wat] is made to circulate ar\nd ! coil4 ,! cond5s$ /eam escapes at w4 ,comm]cially1 di/illation is a v important process4 ,turp5t9e1 = example1 is made by di/ill+ ! sap ( p9e trees4 ,incisions are cut 9 ! b>k ( ! long-leaf p9e trees1 & ^! s]ve z *annels = ! escape ( crude res94 ,?is crude liquid is collect$ 9 b>rels & tak5 to a di/ill]y1 :]e x is di/ill$ into turp5t9e & ros94 ,! turp5t9e is ! product :i* passes (f z vapor1 & ! ros9 is ! mass left 9 ! boil] aft] ! di/illation ( ! turp5t9e4 #bf4 ,evaporation4 ,if a /opp] is left (f a cologne bottle1 ! cont5ts ( ! bottle w sl[ly evaporate2 if a di% ( wat] is plac$ out ( doors on a hot day1 evaporation occurs v rapidly4 ,! liquids :i* h disappe>$ f ! bottle & ! di% h pass$ into ! surr\nd+ air 9 ! =m ( vapor4 ,9 ,section #bj1 we saw t wat] c\ld n pass into vapor )\t ! addition ( heat2 n[ ! heat necess>y = ! evaporation ( ! cologne & wat] 0 tak5 f ! air1 leav+ x slightly cool]4 ,if wet h&s are n dri$ ) a t[el1 b are left to dry by evaporation1 heat is tak5 f ! h& 9 ! process1 leav+ a s5sation ( coolness4 ,damp clo?+ %\ld nev] be worn1 because ! moi/ure 9 x t5ds to evaporate at ! exp5se ( ! bodily heat1 & ?is undue loss ( heat f ! body produces *ills4 ,aft] a ba? ! body %\ld be well rubb$1 o!rwise evaporation occurs at ! exp5se ( heat :i* ! body _c ord9>ily af=d to lose4 ,evaporation is a sl[ process occurr+ at all times2 x is ha/5$ dur+ ! summ]1 because ( ! l>ge am\nt ( heat pres5t 9 ! atmosph]e4 ,_m l>ge cities make use ( ! cool+ effect ( evaporation to l[] ! temp]ature ( ! air 9 summ]2 /reets are spr9kl$ n only to lay ! du/1 b 9 ord] t ! surr\nd+ air may be cool$ by ! evaporation ( ! wat]4 ,"s ?rifty h\sewives economize by utiliz+ ! cool+ effects ( evaporation4 ,butt]1 *eese1 & o!r foods s5sitive to heat are plac$ 9 por\s vessels wrapp$ 9 wet clo?s4 ,rapid evaporation ( ! wat] f ! wet clo?s keeps ! cont5ts ( ! j>s cool1 & t )\t exp5se o!r ?an ! muscul> en]gy ne$$ = wett+ ! clo?s frequ5tly4 #bg4 ,ra91 ,sn[1 ,fro/1 ,dew4 ,! heat ( ! sun causes con/ant evaporation ( ! wat]s ( oceans1 riv]s1 /reams1 & m>%es1 & ! wat] vapor set free by evaporation passes into ! air1 :i* becomes *>g$ ) vapor or is said to be humid4 ,con/ant1 unceas+ evaporation ( our lakes1 /reams1 & pools w\ld mean a /eady decrease 9 ! supply ( wat] available = daily use1 if ! escap$ wat] 7 all reta9$ by ! atmosph]e & lo/ to ! e>?4 ,b al?\gh ! escap$ vapor m+les ) ! atmosph]e1 hov]+ ne> ! e>?'s surface1 or ris+ f> above ! level ( ! m\nta9s1 x does n rema9 !re p]man5tly4 ,:5 ?is vapor meets a cold w9d or is *ill$ 9 any way1 cond5sation takes place1 & a mass ( t9y drops ( wat] or ( small p>ticles ( sn[ is =m$4 ,:5 ^! drops or p>ticles become l>ge en\gh1 !y fall to ! e>? z ra9 or sn[1 & 9 ?is way ! e>? is comp5sat$ = ! great loss ( moi/ure due to evaporation4 ,fog is =m$ :5 vapor cond5ses ne> ! surface ( ! e>?1 & :5 ! drops are s small t !y d n fall b hov] 9 ! air1 ! fog is said n to lift or n to cle>4 ,if ice wat] is p\r$ into a glass1 a mi/ w =m on ! outside ( ! glass4 ,?is is because ! wat] vapor 9 ! air becomes *ill$ by contact ) ! glass & cond5ses4 ,(t5 leaves & grass & sidewalks are s cold t ! wat] vapor 9 ! atmosph]e cond5ses on !m1 & we say a heavy dew has =m$4 ,if ! temp]ature ( ! air falls to ! freez+ po9t :ile ! dew is =m+1 ! vapor is froz5 & fro/ is se5 in/ead ( dew4 ,! daily evaporation ( moi/ure into ! atmosph]e keeps ! atmosph]e m or less full ( wat] vapor2 b ! atmosph]e c hold only a def9ite am\nt ( vapor at a giv5 temp]ature1 & z soon z x conta9s ! maximum am\nt = t temp]ature1 fur!r evaporation ceases4 ,if clo!s are hung out on a damp1 murky day !y d n dry1 because ! air conta9s all ! moi/ure x c hold1 & ! moi/ure 9 ! clo!s has no *ance to evaporate4 ,:5 ! air conta9s all ! moi/ure x c hold1 x is said to be saturat$1 & if a slight fall 9 temp]ature occurs :5 ! air is saturat$1 cond5sation imm$iately beg9s 9 ! =m ( ra91 sn[1 or fog4 ,if1 h[ev]1 ! air is n saturat$1 a fall 9 temp]ature may occur )\t produc+ precipitation4 ,! temp]ature at :i* air is saturat$ & cond5sation beg9s is call$ ! dew po9t4 #bh4 ,h[ ,*ills are ,caus$4 ,! discom=t we feel 9 an ov]cr[d$ room is p>tly due to an excess ( moi/ure 9 ! air1 result+ f ! brea?+ & p]spiration ( _m p]sons4 ,! air soon becomes saturat$ ) vapor & _c take away ! p]spiration f our bodies1 & our clo?+ becomes moi/ & our sk9 t5d]4 ,:5 we leave ! cr[d$ tea or lecture & pass into ! cold]1 dri]1 outside air1 clo!s & sk9 give up _! load ( moi/ure ?r\gh sudd5 evaporation4 ,b evaporation requires heat1 & ?is heat is tak5 f our bodies1 & a *ill results4 ,prop] v5tilation w\ld elim9ate mu* ( ! physical dang] ( social ev5ts2 fre%1 dry air %\ld be con/antly admitt$ to cr[d$ rooms 9 ord] to replace ! air saturat$ by ! brea? & p]spiration ( ! occupants4 #bi4 ,wea!r ,=eca/s4 ,:5 ! air is ne> ! saturation po9t1 ! wea!r is oppressive & is said to be v humid4 ,= com=t & heal?1 ! air %\ld be ab\t two ?irds saturat$4 ,! pres5ce ( "s wat] vapor 9 ! air is absolutely necess>y to animal & plant life4 ,9 des]t regions :]e vapor is sc>ce ! air is s dry t ?roat tr\ble accompani$ by disagreeable tickl+ is preval5t2 fall5 leaves become s dry t !y crumble to du/2 plants lose _! fre%ness & beauty4 ,! likelihood ( ra9 or fro/ is (t5 det]m9$ by temp]ature & humidity4 ,if ! air is ne> saturation & ! temp]ature is fall+1 x is safe to pr$ict bad wea!r1 because ! fall ( temp]ature w probably cause rapid cond5sation1 & h5ce ra94 ,if1 h[ev]1 ! air is n ne> ! saturation po9t1 a fall 9 temp]ature w n necess>ily produce bad wea!r4 ,! measurem5t ( humidity is ( f> wid] importance ?an ! m]e =eca/+ ( local wea!r conditions4 ,! close relation betwe5 humidity & heal? has l$ _m in/itutions1 su* z hospitals1 s*ools1 & factories1 to regulate ! humidity ( ! atmosph]e z c>efully z !y d ! temp]ature4 ,too great humidity is en]vat+1 & n conducive to ei!r m5tal or physical ex]tion2 on ! o!r h&1 too dry air is equally h>mful4 ,9 summ] ! humidity conditions _c be well regulat$1 b 9 w9t]1 :5 h\ses are artificially heat$1 ! humidity ( a room c be increas$ by plac+ pans ( wat] ne> ! regi/]s or on radiators4 #cj4 ,heat ,ne$$ to ,melt ,sub/ances4 ,if a spoon is plac$ 9 a vessel ( hot wat] = a few seconds & !n remov$1 x w be w>m] ?an be=e x 0 plac$ 9 ! hot wat]4 ,if a lump ( melt+ ice is plac$ 9 ! vessel ( hot wat] & !n remov$1 ! ice w n be w>m] ?an be=e1 b !re w be less ( x4 ,! heat ( ! wat] has be5 us$ 9 melt+ ! ice1 n 9 *ang+ its temp]ature4 ,if1 on a bitt] cold day1 a pail ( sn[ is br\ght into a w>m room & a !rmomet] is plac$ 9 ! sn[1 ! temp]ature rises gradually until #cb ,f4 is rea*$1 :5 x becomes /ation>y1 & ! sn[ beg9s to melt4 ,if ! pail is put on ! fire1 ! temp]ature /ill rema9s #cb;,f41 b ! sn[ melts m rapidly4 ,z soon z all ! sn[ is completely melt$1 h[ev]1 ! temp]ature beg9s to rise & rises /eadily until ! wat] boils1 :5 x aga9 becomes /ation>y & rema9s s dur+ ! passage ( wat] into vapor4 ,we see t heat mu/ be suppli$ to ice at #j ,c4 or #cb ,f4 9 ord] to *ange x into wat]1 & fur!r1 t ! temp]ature ( ! mixture does n rise s long z any ice is pres5t1 no matt] h[ mu* heat is suppli$4 ,! am\nt ( heat necess>y to melt #a gram ( ice is easily calculat$4 7,see ,laboratory ,manual47 ,heat mu/ be suppli$ to ice to melt x4 ,on ! o!r h&1 wat]1 9 freez+1 loses heat1 & ! am\nt ( heat lo/ by freez+ wat] is exactly equal to ! am\nt ( heat absorb$ by melt+ ice4 ,! numb] ( units ( heat requir$ to melt a unit mass ( ice is call$ ! heat ( fusion ( wat]4 #ca4 ,climate4 ,wat]1 9 freez+1 loses heat1 ev5 ?\gh its temp]ature rema9s at #j ,c4 ,because wat] loses heat :5 x freezes1 ! pres5ce ( l>ge /reams ( wat] greatly influ5ces ! climate ( a region4 ,9 w9t] ! heat f ! freez+ wat] keeps ! temp]ature ( ! surr\nd+ high] ?an x w\ld naturally be1 & consequ5tly ! cold wea!r is less sev]e4 ,9 summ] wat] evaporates1 heat is tak5 f ! air1 & consequ5tly ! w>m wea!r is less int5se4 #cb4 ,mold+ ( ,glass & ,=g+ ( ,iron4 ,! fire :i* is hot en\gh to melt a lump ( ice may n be hot en\gh to melt an iron pok]2 on ! o!r h&1 x may be suffici5tly hot to melt a t9 spoon4 ,diff]5t sub/ances melt1 or liquefy1 at diff]5t temp]atures2 = example1 ice melts at #j ,c41 & t9 at #bcc ,c41 :ile iron requires ! relatively high temp]ature ( #abjj ,c4 ,mo/ sub/ances h a def9ite melt+ or freez+ po9t :i* nev] *anges s long z ! surr\nd+ conditions rema9 ! same4 ,b :ile mo/ sub/ances h a def9ite melt+ po9t1 "s sub/ances d n4 ,if a glass rod is held 9 a ,buns5 burn]1 x w gradually gr[ s(t] & s(t]1 & f9ally a drop ( molt5 glass w fall f ! end ( ! rod into ! fire4 ,! glass did n sudd5ly become a liquid at a def9ite temp]ature2 in/ead x s(t5$ gradually1 & !n melt$4 ,:ile glass is 9 ! s(t1 yield+1 pliable /ate1 x is mold$ into di%es1 bottles1 & o!r useful objects1 su* z lamp %ades1 globes1 etc4 7,fig4 #bj74 ,if glass melt$ at a def9ite temp]ature1 x c\ld n be mold$ 9 ?is way4 ,iron acts 9 a simil> mann]1 & because ( ?is prop]ty ! blacksmi? c %ape 8 horse%oes1 & ! workman c make 8 eng9es & o!r articles ( daily s]vice to man4 ,illu/ration3 ,,fig4 #bj4--,molt5 glass be+ roll$ into a =m suitable = w9d[ panes4 #cc4 ,/range ,behavior ( ,wat]4 ,"o has b to rememb] t bottles ( wat] bur/ :5 !y freeze1 & t ice floats on wat] l wood1 to "k t wat] exp&s on freez+ or on solidify+4 ,a quantity ( wat] :i* occupies #ajj cubic feet ( space w1 on becom+ ice1 ne$ #aji cubic feet ( space4 ,on a cold w9t] night ! wat] sometimes freezes 9 ! wat] pipes1 & ! pipes bur/4 ,wat] is v peculi> 9 exp&+ on solidification1 because mo/ sub/ances contract on solidify+2 gelat9 & jelly1 = example1 contract s mu* t !y %r9k f ! sides ( ! di% :i* conta9s !m4 ,if wat] contract$ 9 freez+1 ice w\ld be heavi] ?an wat] & w\ld s9k 9 ponds & lakes z fa/ z x =m$1 & our /reams & ponds w\ld become masses ( solid ice1 kill+ all animal & plant life4 ,b ! ice is light] ?an wat] & floats on top1 & animals 9 ! wat] b5ea? are z free to live & swim z !y 7 9 ! w>m sunny days ( summ]4 ,! mo/ sev]e w9t] _c freeze a deep lake solid1 & 9 ! colde/ wea!r a hole made 9 ! ice w %[ wat] b5ea? ! surface4 ,our ice boats cut & break ! ice ( ! riv]1 & ?r\gh ! wat] b5ea? our boats daily ply _! way to & fro1 indep5d5t ( w9t] & its blight+ bla/s4 ,:ile mo/ ( u are famili> ) ! bur/+ ( wat] pipes on a cold night1 few ( u realize ! influ5ce :i* freez+ wat] ex]ts on ! "* ( ! l& ar\nd u4 ,wat] s9ks into ! gr\nd &1 on ! approa* ( w9t]1 freezes1 exp&+ ab\t "o t5? ( its volume2 ! exp&+ ice pu%es ! e>? aside1 ! =ce 9 "s cases be+ suffici5t to dislodge ev5 huge rocks4 ,9 ! e>ly days 9 ,new ,engl& x 0 said by ! f>m]s t rocks grew1 because fields cle>$ ( /ones 9 ! fall became rock cov]$ ) ! approa* ( spr+2 ! rocks & /ones hidd5 und]gr\nd & unse5 9 ! fall 7 =c$ to ! surface by ! w9t]'s expansion4 ,we h all se5 f5ce po/s & bricks pu%$ out ( place because ( ! heav+ ( ! soil b5ea? !m4 ,(t5 h\sehold]s mu/ relay _! pavem5ts & walks because ( ! damage done by freez+ wat]4 ,! mo/ conspicu\s effect ( ! expansive p[] ( freez+ wat] is se5 9 rocky or m\nta9\s regions 7,fig4 #ba74 ,wat] easily f9ds entrance into ! cracks & crevices ( ! rocks1 :]e x lodges until froz52 !n x exp&s & acts l a w$ge1 wid5+ cracks1 *isel+ (f edges1 & ev5 break+ rocks asund]4 ,9 regions :]e frequ5t fro/s occur1 ! de/ructive action ( wat] works con/ant *anges 9 ! appe>ance ( ! l&2 small cracks & crevices are enl>g$1 massive rocks are pri$ up out ( position1 huge slabs are split (f1 & p>ticles l>ge & small are =c$ f ! p>5t rock4 ,! great] "p ( ! debris & rubbi% br\ght d[n f ! m\nta9 slopes by ! spr+ ra9s owes its orig9 to ! fact t wat] exp&s :5 x freezes4 ,illu/ration3 ,,fig4 #ba4--,! de/ruction caus$ by freez+ wat]4 #cd4 ,heat ,necess>y to ,dissolve a ,sub/ance4 ,x requires heat to dissolve any sub/ance1 j z x requires heat to *ange ice to wat]4 ,if a h&ful ( common salt is plac$ 9 a small cup ( wat] & /irr$ ) a !rmomet]1 ! temp]ature ( ! mixture falls sev]al degrees4 ,?is is j :at "o w\ld expect1 because ! heat ne$$ to liquefy ! salt mu/ come f some:]e1 & naturally x comes f ! wat]1 !reby l[]+ ! temp]ature ( ! wat]4 ,we "k v well t potatoes cease boil+ if a p9* ( salt is put 9 ! wat]2 ?is is because ! temp]ature ( ! wat] has be5 l[]$ by ! am\nt ( heat necess>y to dissolve ! salt4 ,let "s sn[ or *opp$ ice be plac$ 9 a vessel & mix$ ) "o ?ird its weight ( co>se salt2 if !n a small tube ( cold wat] is plac$ 9 ?is mixture1 ! wat] 9 ! te/ tube w soon freeze solid4 ,z soon z ! sn[ & salt are mix$ !y melt4 ,! heat necess>y = ?is comes 9 "p f ! air & 9 "p f ! wat] 9 ! te/ tube1 & ! wat] 9 ! tube becomes 9 consequ5ce cold en\gh to freeze4 ,b ! salt mixture does n freeze because its freez+ po9t is f> bel[ t ( pure wat]4 ,! use ( salt & ice 9 ice-cream freez]s is a practical application ( ?is pr9ciple4 ,! heat necess>y = melt+ ! mixture ( salt & ice is tak5 f ! cream :i* ?us becomes cold en\gh to freeze4 ,,*apt] ,,iv ,,burn+ ,,or ,,oxidation #ce4 ,:y ,?+s ,burn4 ,! heat ( our bodies comes f ! food we eat2 ! heat = cook+ & = w>m+ our h\ses comes f coal4 ,! production ( heat ?r\gh ! burn+ ( coal1 or oil1 or gas1 or wood1 is call$ combu/ion4 ,combu/ion _c occur )\t ! pres5ce ( a sub/ance call$ oxyg51 :i* exi/s r abundantly 9 ! air2 t is1 "o fif? ( our atmosph]e consi/s ( ?is sub/ance :i* we call oxyg54 ,we ?r[ op5 our w9d[s to all[ fre% air to ent]1 & we take walks 9 ord] to brea! ! pure air into our lungs4 ,:at we ne$ = ! en]gy & w>m? ( our bodies is ! oxyg5 9 ! air4 ,:e!r we burn gas or wood or coal1 ! heat :i* is produc$ comes f ! p[] :i* ^! v>i\s sub/ances possess to comb9e ) oxyg54 ,we op5 ! draft ( a /ove t x may draw well3 t x may secure oxyg5 = burn+4 ,we ?r[ a blanket ov] burn+ mat]ial to smo!r ! fire3 to keep oxyg5 away f x4 ,burn+1 or oxidation1 is comb9+ ) oxyg51 & ! m oxyg5 y add to a fire1 ! hott] ! fire w burn1 & ! fa/]4 ,! effect ( oxyg5 on combu/ion may be cle>ly se5 by ?ru/+ a smold]+ spl9t] into a j> conta9+ oxyg52 ! smold]+ spl9t] w in/antly fl>e & blaze1 :ile if x is remov$ f ! j>1 x loses its flame & aga9 burns quietly4 ,oxyg5 = ?is exp]im5t c be produc$ 9 ! foll[+ way4 ,illu/ration3 ,,fig4 #bb4--,prep>+ oxyg5 f potassium *lorate & manganese dioxide4 #cf4 ,h[ to ,prep>e ,oxyg54 ,mix a small quantity ( potassium *lorate ) an equal am\nt ( manganese dioxide & place ! mixture 9 a /rong te/ tube4 ,close ! m\? ( ! tube ) a "o-hole rubb] /opp] 9 :i* is fitt$ a long1 n>r[ tube1 & clamp ! te/ tube to an iron support1 z %[n 9 ,figure #bb4 ,fill ! tr\gh ) wat] until ! %elf is j cov]$ & all[ ! end ( ! deliv]y tube to re/ j b5ea? ! hole 9 ! %elf4 ,fill a m$ium-siz$ bottle ) wat]1 cov] x ) a glass plate1 inv]t ! bottle 9 ! tr\gh1 & !n remove ! glass plate4 ,heat ! te/ tube v g5tly1 & :5 gas bubbles out ( ! tube1 slip ! bottle ov] ! op5+ 9 ! %elf1 s t ! tube runs into ! bottle4 ,! gas w =ce out ! wat] & w f9ally fill ! bottle4 ,:5 all ! wat] has be5 =c$ out1 slip ! glass plate "u ! m\? ( ! bottle & remove ! bottle f ! tr\gh4 ,! gas 9 ! bottle is oxyg54 ,ev]y:]e 9 a l>ge city or 9 a small village1 smoke is se51 indicat+ ! pres5ce ( fire2 h5ce !re mu/ exi/ a l>ge supply ( oxyg5 to keep all ! fires alive4 ,! supply ( oxyg5 ne$$ = ! fires ( ! _w comes l>gely f ! atmosph]e4 #cg4 ,mat*es4 ,! burn+ mat]ial is ord9>ily set on fire by mat*es1 ?9 /rips ( wood tipp$ ) sulphur or phosphorus1 or bo?4 ,phosphorus c unite ) oxyg5 at a fairly l[ temp]ature1 & if phosphorus is rubb$ aga9/ a r\gh surface1 ! friction produc$ w raise ! temp]ature ( ! phosphorus to a po9t :]e x c comb9e ) oxyg54 ,! burn+ phosphorus k9dles ! wood ( ! mat*1 & f ! burn+ mat* ! fire is k9dl$4 ,if y want to conv9ce y\rself t friction produces heat1 rub a c5t vigor\sly aga9/ y\r coat & note t ! c5t becomes w>m4 ,mat*es h be5 9 use less ?an a hundr$ ye>s4 ,primitive man k9dl$ 8 camp fire by rubb+ pieces ( dry wood toge!r until !y took fire1 & ?is me?od is said to be us$ among "s isolat$ di/ant tribes at ! pres5t "t4 ,a lat] & easi] way 0 to /rike fl9t & /eel toge!r & to cat* ! sp>k ?us produc$ on t9d] or dry fungus4 ,)9 ! memory ( "s p]sons n[ liv+1 ! t9d] box 0 a valuable asset to ! home1 p>ticul>ly 9 ! pione] regions ( ! ,we/4 #ch4 ,safety ,mat*es4 ,ord9>y phosphorus1 :ile excell5t z a fire-produc+ mat]ial1 is dang]\sly poison\s1 & ^? to :om ! dipp+ ( wood5 /rips into phosphorus is a daily occupation suff] ) a t]rible disease :i* usually attacks ! tee? & bones ( ! jaw4 ,! tee? rot & fall out1 abscesses =m1 & bones & fle% beg9 to decay2 ! only way to prev5t ! spread ( ! disease is to remove ! affect$ bone1 & 9 "s in/ances x has be5 necess>y to remove ! entire jaw4 ,!n1 too1 mat*es made ( yell[ or :ite phosphorus ignite easily1 &1 :5 rubb$ aga9/ any r\gh surface1 are apt to take fire4 ,_m de/ructive fires h be5 />t$ by ! accid5tal friction ( su* mat*es aga9/ r\gh surfaces4 ,= ^! reasons ! introduction ( ! s-call$ safety mat* 0 an important ev5t4 ,:5 common phosphorus1 9 ! dang]\s & easily ignit$ =m1 is heat$ 9 a clos$ vessel to ab\t #bej ,c41 x gradually *anges to a h>mless r$ mass4 ,! r$ phosphorus is n only h>mless1 b x is difficult to ignite1 &1 9 ord] to be ignit$ by friction1 mu/ be rubb$ on a surface ri* 9 oxyg54 ,! head ( a safety mat* is coat$ ) a mixture ( glue & oxyg5-conta9+ comp\nds2 ! surface on :i* ! mat* is to be rubb$ is coat$ ) a mixture ( r$ phosphorus & glue1 to :i* f9ely p[d]$ glass is sometimes add$ 9 ord] to increase ! friction4 ,unless ! head ( ! mat* is rubb$ on ! prep>$ phosphorus coat+1 ignition does n occur1 & accid5tal fires are avoid$4 ,v>i\s k9ds ( safety mat*es h be5 manufactur$ 9 ! la/ few ye>s1 b !y are some:at m exp5sive ?an ! ord9>y =m1 & h5ce manufactur]s are reluctant to sub/itute !m = ! *eap] mat*es4 ,"s =eign c\ntries1 su* z ,switz]l&1 prohibit ! sale ( ! dang]\s type1 & x is hop$ t ! ,unit$ ,/ates w soon foll[ ! lead ( ^! c\ntries 9 dem&+ ! sale ( safety mat*es only4 #ci4 ,"s ,unfamili> ,=ms ( ,burn+4 ,:ile mo/ ( u ?9k ( burn+ z a process 9 :i* flames & smoke occur1 !re are 9 reality _m modes ( burn+ accompani$ by nei!r flame nor smoke4 ,iron1 = example1 burns :5 x ru/s1 because x sl[ly comb9es ) ! oxyg5 ( ! air & is trans=m$ into new sub/ances4 ,:5 ! air is dry1 iron does n unite ) oxyg51 b :5 moi/ure is pres5t 9 ! air1 ! iron unites ) ! oxyg5 & turns into iron ru/4 ,! burn+ is sl[ & unaccompani$ by ! fire & smoke s famili> to u1 b ! process is none ! less burn+1 or comb9ation ) oxyg54 ,burn+ :i* is n accompani$ by any ( ! appe>ances ( ord9>y burn+ is kn[n z oxidation4 ,! t5d5cy ( iron to ru/ less5s its effici5cy & value1 & _m devices h be5 introduc$ to prev5t ru/+4 ,a coat+ ( pa9t or v>ni% is sometimes appli$ to iron 9 ord] to prev5t contact ) air4 ,! galvaniz+ ( iron is ano!r attempt to secure ! same result2 9 ?is process iron is dipp$ into molt5 z9c1 !reby acquir+ a coat+ ( z9c1 & =m+ :at is kn[n z galvaniz$ iron4 ,z9c does n comb9e ) oxyg5 "u ord9>y circum/ances1 & h5ce galvaniz$ iron is immune f ru/4 ,decay is a process ( oxidation2 ! tree :i* rots sl[ly away is und]go+ oxidation1 & ! result ( ! sl[ burn+ is ! decompos$ matt] :i* we see & ! invisible gases :i* pass into ! atmosph]e4 ,! log :i* blazes on our he>? gives out suffici5t heat to w>m u2 ! log :i* decays 9 ! =e/ gives out an equival5t am\nt ( heat1 b ! heat is evolv$ s sl[ly t we are n consci\s ( x4 ,burn+ accompani$ by a blaze & int5se heat is a rapid process2 burn+ unaccompani$ by fire & appreciable heat is a sl[1 gradual process1 requir+ days1 weeks1 & ev5 long ye>s = its completion4 ,ano!r =m ( oxidation occurs daily 9 ! human body4 ,9 ,section #ce we saw t ! human body is an eng9e ^: fuel is food2 ! burn+ ( t food 9 ! body furni%es ! heat necess>y = bodily w>m? & ! en]gy requir$ = ?\ght & action4 ,oxyg5 is ess5tial to burn+1 & ! food fires )9 ! body are kept alive by ! oxyg5 tak5 into ! body at e brea? by ! lungs4 ,we see n[ "o reason = an abundance ( fre% air 9 daily life4 #dj4 ,h[ to ,brea!4 ,air1 :i* is ess5tial to life & heal?1 %\ld ent] ! body ?r\gh ! nose & n ?r\gh ! m\?4 ,! peculi> nature & arrangem5t ( ! membranes ( ! nose enable ! no/rils to clean1 & w>m1 & moi/5 ! air :i* passes ?r\gh !m to ! lungs4 ,float+ ar\nd 9 ! atmosph]e are du/ p>ticles :i* ought n to get into ! lungs4 ,! nose is provid$ ) small hairs & a moi/ inn] membrane :i* s]ve z filt]s 9 remov+ solid p>ticles f ! air1 & 9 ?us purify+ x be=e its entrance into ! lungs4 ,9 ! imm$iate neighborhood ( ?ree ,philadelphia high s*ools1 hav+ an approximate enrollm5t ( ov] #hjjj pupils1 is a huge manufactur+ plant :i* day & night p\rs =? grimy smoke & soot into ! atmosph]e :i* mu/ supply oxyg5 to ?is va/ gr\p ( "y lives4 ,if ! vital importance ( nose brea?+ is impress$ ^u ^! "y p1 ! h>mful effect ( ! f\l air may be greatly less5$1 ! smoke p>ticles & g]ms be+ held back by ! nose filt]s & nev] rea*+ ! lungs4 ,if1 h[ev]1 ?is pr9ciple ( hygi5e is n br\ght to _! att5tion1 ! dang]\s habit ( brea?+ ?r\gh ! op51 or at lea/ p>tially op51 m\? w cont9ue1 & objectionable matt] w pass ?r\gh ! m\? & f9d a lodg+ place 9 ! lungs4 ,!re is ano!r v important reason :y nose brea?+ is pref]able to m\? brea?+4 ,! temp]ature ( ! human body is approximately #ih ,f41 & ! air :i* ent]s ! lungs %\ld n be f> bel[ ?is temp]ature4 ,if air rea*es ! lungs ?r\gh ! nose1 its j\rney is relatively long & sl[1 & !re is opportunity = x to be w>m$ be=e x rea*es ! lungs4 ,if1 on ! o!r h&1 air passes to ! lungs by way ( ! m\?1 ! w>m+ process is brief & insuffici5t1 & ! lungs suff] 9 consequ5ce4 ,naturally1 ! grave/ dang] is 9 w9t]4 #da4 ,cause ( ,m\? ,brea?+4 ,"s p f9d x difficult to brea! ?r\gh ! no/rils on acc\nt ( gr[?s1 call$ ad5oids1 9 ! nose4 ,if y h a t5d5cy t[>d m\? brea?+1 let a physician exam9e y\r nose & ?roat4 ,ad5oids n only ob/ruct brea?+ & weak5 ! :ole sy/em ?r\gh lack ( adequate air1 b !y also press ^u ! blood vessels & n]ves ( ! head & int]f]e ) normal bra9 developm5t4 ,moreov]1 !y int]f]e 9 _m cases ) ! he>+1 & 9 g5]al h9d] activity & gr[?4 ,! removal ( ad5oids is simple1 & c>ries ) x only tempor>y pa9 & no dang]4 ,"s physicians claim t ! gr[?s disappe> 9 lat] ye>s1 b ev5 if t is true1 ! physical & m5tal developm5t ( e>li] ye>s is lo/1 & ! p]son is backw>d 9 ! /ruggle = life & a*ievem5t4 ,illu/ration3 ,,fig4 #bc4--;,intellig5t expression is (t5 lack+ 9 *ildr5 ) ad5oid gr[?s4 #db4 ,h[ to ,build a ,fire4 ,sub/ances diff] greatly z to ! ease ) :i* !y may be made to burn or1 9 te*nical t]ms1 ) :i* !y may be made to unite ) oxyg54 ,= ?is reason1 we put light mat]ials1 l %av+s1 *ips1 & pap]1 on ! grate1 twi/+ ! latt] & arrang+ x s t air 7oxyg5 9 ! air7 c rea* a l>ge surface2 ^u ?is we place small /icks ( wood1 pil+ !m across ea* o!r s z to all[ entrance = ! oxyg52 & f9ally ^u ?is we place our h>d wood or coal4 ,! coal & ! l>ge /icks _c be k9dl$ ) a mat*1 b ! pap] & %av+s c1 & ^! 9 burn+ w heat ! l>ge /icks until !y take fire & 9 turn k9dle ! coal4 #dc4 ,spontane\s ,combu/ion4 ,we (t5 he> ( fires />t+ !mselves1 & sometimes ! /atem5t is true4 ,if a pile ( oily rags is all[$ to /& = a "t1 ! oily matt] w beg9 to comb9e sl[ly ) oxyg5 & z a result w give (f heat4 ,! heat ?us giv5 (f is at fir/ insuffici5t to k9dle a fire2 b z ! heat is reta9$ & accumulat$1 ! temp]ature rises1 & f9ally ! k9dl+ po9t is rea*$ & ! :ole mass bur/s into flames4 ,= safety's sake1 all oily clo?s %\ld be burn$ or kept 9 metal vessels4 #dd4 ,! ,treatm5t ( ,burns4 ,9 spite ( great caution1 burns f fires1 /eam1 or hot wat] d sometimes occur1 & x is well to "k h[ to relieve ! suff]+ caus$ by !m & h[ to treat ! injury 9 ord] to insure rapid heal+4 ,burns are dang]\s because !y de/roy sk9 & ?us op5 up an entrance into ! body = disease g]ms1 & 9 addition because !y lay b>e n]ve tissue :i* !reby becomes irritat$ & causes a %ock to ! entire sy/em4 ,9 mild burns1 :]e ! sk9 is n brok5 b is m]ely r$d5$1 an application ( moi/ bak+ soda br+s imm$iate relief4 ,if ?is sub/ance is n available1 fl\r pa/e1 l>d1 sweet oil1 or vasel9e may be us$4 ,9 m sev]e burns1 :]e bli/]s are =m$1 ! bli/]s %\ld be punctur$ ) a %>p1 /]iliz$ ne$le & all[$ to dis*>ge _! wat]y cont5ts be=e ! above rem$ies are appli$4 ,9 burns sev]e en\gh to de/roy ! sk91 dis9fection ( ! op5 w\nd ) weak c>bolic acid or hydrog5 p]oxide is v necess>y4 ,aft] ?is has be5 done1 a s(t clo? soak$ 9 a solution ( l9se$ oil & limewat] %\ld be appli$ & ! :ole b&ag$4 ,9 su* a case1 x is important n to use cotton batt+1 s9ce ?is /icks to ! r\gh surface & causes pa9 :5 remov$4 #de4 ,c>bon ,dioxide4 ,a ,product ( ,burn+4 ,:5 any fuel1 su* z coal1 gas1 oil1 or wood1 burns1 x s5ds =? gases into ! surr\nd+ atmosph]e4 ,^! gases1 l air1 are invisible1 & 7 unkn[n to u = a long "t4 ,! *ief gas =m$ by a burn+ sub/ance is call$ c>bon dioxide 7,,co#b7 because x is compos$ ( "o "p ( c>bon & two p>ts ( oxyg54 ,?is gas has ! di/9ction ( be+ ! mo/ widely di/ribut$ gase\s comp\nd ( ! entire _w2 x is f\nd 9 ! ocean dep?s & on ! m\nta9 heights1 9 brilliantly light$ rooms1 & mo/ abundantly 9 manufactur+ t[ns :]e factory *imneys con/antly p\r =? hot gases & smoke4 ,wood & coal1 & 9 fact all animal & vegetable matt]1 conta9 c>bon1 & :5 ^! sub/ances burn or decay1 ! c>bon 9 !m unites ) oxyg5 & =ms c>bon dioxide4 ,! food :i* we eat is ei!r animal or vegetable1 & x is made ready = bodily use by a sl[ process ( burn+ )9 ! body2 c>bon dioxide accompanies ?is bodily burn+ ( food j z x accompanies ! fires ) :i* we are m famili>4 ,! c>bon dioxide ?us produc$ )9 ! body escapes into ! atmosph]e ) ! brea?4 ,we see t ! s\rce ( c>bon dioxide is practically inexhau/ible1 com+ z x does f e /ove1 furnace1 & c&le1 & fur!r ) e brea? ( a liv+ organism4 #df4 ,dang] ( ,c>bon ,dioxide4 ,:5 c>bon dioxide occurs 9 l>ge quantities1 x is dang]\s to heal?1 because x int]f]es ) normal brea?+1 less5+ ! escape ( wa/e matt] ?r\gh ! brea? & prev5t+ ! access to ! lungs ( ! oxyg5 necess>y = life4 ,c>bon dioxide is n poison\s1 b x cuts (f ! supply ( oxyg51 j z wat] cuts x (f f a dr[n+ man4 ,s9ce e man1 woman1 & *ild con/antly brea!s =? c>bon dioxide1 ! dang] 9 ov]cr[d$ rooms is great1 & prop] v5tilation is ( vital importance4 #dg4 ,v5tilation4 ,9 e/imat+ ! quantity ( air necess>y to keep a room well air$1 we mu/ take into acc\nt ! numb] ( lights 7electric lights d n c\nt7 to be us$1 & ! numb] ( p to occupy ! room4 ,! av]age h\se %\ld provide at ! m9imum #fjj cubic feet ( space = ea* p]son1 & 9 addition1 arrangem5ts = all[+ at lea/ #cjj cubic feet ( fre% air p] p]son to ent] e h\r4 ,9 h\ses :i* h n a v5tilat+ sy/em1 ! air %\ld be kept fre% by intellig5t action 9 ! op5+ ( doors & w9d[s2 & s9ce relatively few h\ses are equipp$ ) a satisfactory sy/em1 ! foll[+ sugge/ions relative to intellig5t v5tilation are (f]$4 #a4 ,avoid drafts 9 v5tilation4 #b4 ,v5tilate on ! %elt]$ side ( ! h\se4 ,if ! w9d is bl[+ f ! nor?1 op5 s\? w9d[s4 #dh4 ,:at ,becomes ( ! ,c>bon ,dioxide4 ,:5 we reflect t c>bon dioxide is con/antly be+ suppli$ to ! atmosph]e & t x is injuri\s to heal?1 ! "q naturally arises z to h[ ! air rema9s free en\gh ( ! gas to support life4 ,?is is l>gely because c>bon dioxide is an ess5tial food ( plants4 ,?r\gh _! leaves plants absorb x f ! atmosph]e1 & by a wond]ful process break x up into its compon5t p>ts1 oxyg5 & c>bon4 ,!y reject ! oxyg51 :i* passes back to ! air1 b !y reta9 ! c>bon1 :i* becomes a "p ( ! plant /ructure4 ,plants ?us s]ve to keep ! atmosph]e free f an excess ( c>bon dioxide &1 9 addition1 furni% oxyg5 to ! atmosph]e4 ,illu/ration3 ,,fig4 #bd4--,mak+ c>bon dioxide f m>ble & hydro*loric acid4 #di4 ,h[ to ,obta9 ,c>bon ,dioxide4 ,!re are sev]al ways 9 :i* c>bon dioxide c be produc$ comm]cially1 b = laboratory use ! simple/ is to mix 9 a te/ tube p[d]$ m>ble1 or *alk1 & hydro*loric acid1 & to collect ! eff]vesc+ gas z %[n 9 ,figure #bd4 ,! sub/ance :i* rema9s 9 ! te/ tube aft] ! gas has pass$ (f is a solution ( a salt & wat]4 ,f a mixture ( hydro*loric acid 7,h,cl7 & m>ble are obta9$ a salt1 wat]1 & c>bon dioxide1 ! desir$ gas4 #ej4 ,a ,comm]cial ,use ( ,c>bon ,dioxide4 ,if a light$ spl9t] is ?ru/ into a te/ tube conta9+ c>bon dioxide1 x is promptly ext+ui%$1 because c>bon dioxide _c support combu/ion2 if a /ream ( c>bon dioxide & wat] falls ^u a fire1 x acts l a blanket1 cov]+ ! flames & ext+ui%+ !m4 ,! value ( a fire ext+ui%] dep5ds ^u ! am\nt ( c>bon dioxide & wat] :i* x c furni%4 ,a fire ext+ui%] is a metal case conta9+ a solution ( bic>bonate ( soda1 & a glass vessel full ( /rong sulphuric acid4 ,z long z ! ext+ui%] is 9 an upright position1 ^! sub/ances are kept sep>ate1 b :5 ! ext+ui%] is inv]t$1 ! acid escapes f ! bottle1 & mixes ) ! soda solution4 ,! m+l+ liquids int]act & lib]ate c>bon dioxide4 ,a "p ( ! gas ?us lib]at$ dissolves 9 ! wat] ( ! soda solution & escapes f ! tube ) ! outfl[+ liquid1 :ile a portion rema9s undissolv$ & escapes z a /ream ( gas4 ,! fire ext+ui%] is !re=e ! s\rce ( a liquid conta9+ ! fire-ext+ui%+ sub/ance & fur!r ! s\rce ( a /ream ( c>bon dioxide gas4 ,illu/ration3 ,,fig4 #be4--;,inside view ( a fire ext+ui%]4 #ea4 ,c>bon4 ,al?\gh c>bon dioxide is v injuri\s to heal?1 bo? ( ! sub/ances ( :i* x is compos$ are necess>y to life4 ,we ourselves1 our bones & fle% 9 p>ticul>1 are p>tly c>bon1 & e animal1 no matt] h[ small or insignificant1 conta9s "s c>bon2 :ile ! plants ar\nd u1 ! trees1 ! grass1 ! fl[]s1 conta9 a by no means meag] quantity ( c>bon4 ,c>bon plays an important & v>i$ role 9 our life1 &1 9 "s "o ( its _m =ms1 ent]s into ! composition ( mo/ ( ! sub/ances :i* are ( s]vice & value to man4 ,! food we eat1 ! clo!s we we>1 ! wood & coal we burn1 ! m>ble we employ 9 build+1 ! indisp5sable soap1 & ! ornam5tal diamond1 all conta9 c>bon 9 "s =m4 #eb4 ,*>coal4 ,"o ( ! mo/ valuable =ms ( c>bon is *>coal2 valuable n 9 ! s5se t x co/s hundr$s ( doll>s1 b 9 ! m vital s5se1 t its use adds to ! cleanl9ess1 com=t1 & heal? ( man4 ,! f\l1 bad-smell+ gases :i* arise f sew]s c be prev5t$ f escap+ & pass+ to /reets & build+s by plac+ *>coal filt]s at ! sew] exits4 ,*>coal is por\s & absorbs f\l gases1 & ?us keeps ! region surr\nd+ sew]s sweet & clean & free ( odor4 ,good h\sekeep]s drop small bits ( *>coal into vases ( fl[]s to prev5t discoloration ( ! wat] & ! odor ( decay+ /ems4 ,if impure wat] filt]s ?r\gh *>coal1 x em]ges pure1 hav+ left its impurities 9 ! pores ( ! *>coal4 ,practically all h\sehold filt]s ( dr9k+ wat] are made ( *>coal4 ,b su* a device may be a s\rce ( disease in/ead ( a prev5tion ( disease1 unless ! filt] is regul>ly clean$ or r5ew$4 ,?is is because ! pores soon become clogg$ ) ! impurities1 & unless !y are clean$1 ! wat] :i* fl[s ?r\gh ! filt] passes ?r\gh a b$ ( impurities & becomes contam9at$ r ?an purifi$4 ,frequ5t cleans+ or r5ewal ( ! filt] removes ?is difficulty4 ,comm]cially1 *>coal is us$ on a l>ge scale 9 ! ref9+ ( sug>s1 sirups1 & oils4 ,sug>1 :e!r x comes f ! maple tree1 or ! sug> cane1 or ! beet1 is d>k color$4 ,x is :it5$ by passage ?r\gh filt]s ( f9ely pulv]iz$ *>coal4 ,cid] & v9eg> are likewise cle>$ by passage ?r\gh *>coal4 ,! value ( c>bon1 9 ! =m ( *>coal1 z a purifi] is v great1 :e!r we consid] x a deodoriz]1 z 9 ! case ( ! sewage1 or a decoloriz]1 z 9 ! case ( ! ref9]ies1 or :e!r we consid] ! s]vice x has r5d]$ man 9 ! elim9ation ( dang] f dr9k+ wat]4 #ec4 ,h[ ,*>coal is ,made4 ,*>coal may be made by heat+ wood 9 an ov5 to :i* air does n h free access4 ,! abs5ce ( air prev5ts ord9>y combu/ion1 nev]!less ! int5se heat affects ! wood & *anges x into new sub/ances1 "o ( :i* is *>coal4 ,! wood :i* smold]s on ! he>? & 9 ! /ove is *>coal 9 ! mak+4 ,=m]ly wood 0 pil$ 9 heaps1 cov]$ ) sod or s& to prev5t access ( oxyg51 & !n 0 set fire to2 ! smold]+ wood1 cut (f f an adequate supply ( air1 0 sl[ly trans=m$ into *>coal4 ,scatt]$ ov] ! c\ntry "o /ill f9ds isolat$ *>coal kilns1 crude e>!n receptacles1 9 :i* wood ?us depriv$ ( air 0 all[$ to smold] & =m *>coal4 ,to-day *>coal is made comm]cially by pil+ wood on /eel c>s & !n pu%+ ! c>s into /rong wall$ *amb]s4 ,! *amb]s are clos$ to prev5t access ( air1 & heat$ to a high temp]ature4 ,! int5se heat trans=ms ! wood into *>coal 9 a few h\rs4 ,a /ud5t c make 9 ! laboratory suffici5t *>coal = art lessons by heat+ 9 an e>!n vessel wood buri$ 9 s&4 ,! process w be sl[1 h[ev]1 because ! heat furni%$ by a ,buns5 burn] is n great1 & ! wood is trans=m$ sl[ly4 ,a =m ( *>coal kn[n z animal *>coal1 or bone black1 is obta9$ f ! *>r$ rema9s ( animals r ?an plants1 & may be prep>$ by burn+ bones & animal refuse z 9 ! case ( ! wood4 ,de/ructive ,di/illation4 ,:5 wood is burn$ )\t suffici5t air1 x is *ang$ into s(t brittle *>coal1 :i* is v diff]5t f wood4 ,x weighs only "o f\r? z mu* z ! orig9al wood4 ,x is evid5t t mu* matt] mu/ leave ! wood dur+ ! process ( *>coal mak+4 ,we c prove ?is by putt+ "s dry %av+s 9 a /rong te/ tube fitt$ ) a deliv]y tube4 ,:5 ! wood is heat$ a gas passes (f :i* we may collect & burn4 ,o!r sub/ances also come (f 9 gase\s =m1 b !y cond5se 9 ! wat]4 ,among ^! are wood alcohol1 wood t>1 & acetic acid4 ,9 ! old] me?od ( *>coal mak+ all ^! products 7 lo/4 ,c y give any uses ( ^! sub/ances8 #ed4 ,matt] & ,en]gy4 ,:5 wood is burn$1 a small pile ( a%es is left1 & we ?9k ( ! bulk ( ! wood z de/roy$4 ,x is true we h less matt] t is available = use or t is visible to sight1 b1 nev]!less1 no matt] has be5 de/roy$4 ,! matt] ( :i* ! wood is compos$ has m]ely *ang$ its "*1 "s ( x is 9 ! condition ( a%es1 & "s 9 ! condition ( invisible gases1 su* z c>bon dioxide1 b none ( x has be5 de/roy$4 ,x is a pr9ciple ( sci5ce t matt] c nei!r be de/roy$ nor creat$2 x c only be *ang$1 or trans=m$1 & x is our bus9ess to see t we d n he$lessly trans=m x into sub/ances :i* are valueless to u & our desc5dants2 z1 = example1 :5 our magnific5t =e/s are recklessly wa/$4 ,! smoke1 gases1 & a%es left 9 ! pa? ( a rag+ =e/ fire are no comp5sation to u = ! valuable timb] de/roy$4 ,! sum total ( matt] has n be5 *ang$1 b ! am\nt ( matt] :i* man c use has be5 greatly less5$4 ,! pr9ciple j /at$ embodies "o ( ! fundam5tal laws ( sci5ce1 call$ ! law ( ! cons]vation ( matt]4 ,a simil> law holds = en]gy z well4 ,we c trans=m electric en]gy into ! motion ( trolley c>s1 or we c make use ( ! en]gy ( /reams to turn ! :eels ( our mills1 b 9 all ^! cases we are trans=m+1 n creat+1 en]gy4 ,:5 a ball is fir$ f a rifle1 mo/ ( ! en]gy ( ! gunp[d] is utiliz$ 9 motion1 b "s is dissipat$ 9 produc+ a fla% & a report1 & 9 heat4 ,! en]gy ( ! gunp[d] has be5 scatt]$1 b ! sum ( ! v>i\s =ms ( en]gy is equal to ! en]gy orig9ally /or$ away 9 ! p[d]4 ,! bett] ! gun is1 ! less w be ! en]gy dissipat$ 9 smoke & heat & noise4 ,,*apt] ,v ,,food #ee4 ,! ,body z a ,ma*9e4 ,:olesome food & fre% air are necess>y = a heal?y body4 ,_m h\sewives1 ?r\gh ignorance1 supply to _! h>d-work+ husb&s & _! gr[+ sons & daught]s food :i* satisfies ! appetite1 b :i* does n give to ! body ! elem5ts ne$$ = daily "w & gr[?4 ,"s foods1 su* z lettuce1 cucumb]s1 & wat]melons1 make prop] & satisfactory *anges 9 diet1 b are n /r5g? giv+4 ,o!r foods1 l peas & beans1 n only satisfy ! appetite1 b supply to ! body abundant n\ri%m5t4 ,_m immigrants live *eaply & well ) beans & bread z _! ma9 diet4 ,x is ( vital importance t ! relative value ( diff]5t foods z heat produc]s be kn[n def9itely2 & j z ! y>d measures l5g? & ! p\nd measures weight ! calorie is us$ to measure ! am\nt ( heat :i* a food is capable ( furni%+ to ! body4 ,our bodies are human ma*9es1 &1 l all o!r ma*9es1 require fuel = _! ma9t5ance4 ,! fuel suppli$ to an eng9e is n all available = pull+ ! c>s2 a l>ge portion ( ! fuel is lo/ 9 smoke1 & ano!r portion is wa/$ z a%es4 ,s x is ) ! fuel t runs ! body4 ,! food we eat is n all available = n\ri%m5t1 mu* ( x be+ z useless to u z are smoke & a%es to an eng9e4 ,! be/ foods are ^? :i* d ! mo/ = u ) ! lea/ possible wa/e4 #ef4 ,fuel ,value4 ,by fuel value is meant ! capacity foods h = yield+ heat to ! body4 ,! fuel value ( ! foods we eat daily is s important a factor 9 life t physicians1 dietitians1 nurses1 & ^? hav+ ! c>e ( in/itutional cook+ acqua9t !mselves ) ! relative fuel values ( practically all ( ! important food sub/ances4 ,! life or dea? ( a pati5t may be det]m9$ by ! pati5t's diet1 & ! work+ & e>n+ capacity ( a fa!r dep5ds l>gely ^u 8 prosaic ?ree meals4 ,an ounce ( fat1 :e!r x is ! fat ( meat or ! fat ( olive oil or ! fat ( any o!r food1 produces 9 ! body two & a qu>t] times z mu* heat z an ounce ( />*4 ,( ! vegetables1 beans provide ! greate/ n\ri%m5t at ! lea/ co/1 & to a l>ge ext5t may be sub/itut$ = meat4 ,x is n uncommon to f9d an outdoor labor] consum+ "o p\nd ( beans p] day1 & tak+ meat only on high days & holidays4 ,illu/ration3 ,,fig4 #bf4--,! bomb calorimet] f :i* ! fuel value ( food c be e/imat$4 ,! fuel value ( a food is det]m9$ by means ( ! bomb calorimet] 7,fig4 #bf74 ,! food sub/ance is put into a *amb] ,a & ignit$1 & ! heat ( ! burn+ sub/ance raises ! temp]ature ( ! wat] 9 ! surr\nd+ vessel4 ,if #ajjj grams ( wat] are 9 ! vessel1 & ! temp]ature ( ! wat] is rais$ #b ,c41 ! numb] ( calories produc$ by ! sub/ance w\ld be #bjjj1 & ! fuel value w\ld be #bjjj calories4,a ,f ?is ! fuel value ( "o qu>t or "o p\nd ( ! sub/ance c be det]m9$1 & ! food sub/ance w be said to furni% ! body ) t numb] ( heat units1 provid+ all ( ! p\nd ( food 7 prop]ly dige/$4 ,footnote ,a3 ,z appli$ to food1 ! calorie is great] ?an t us$ 9 ! ord9>y laboratory "w1 be+ ! am\nt ( heat necess>y to raise ! temp]ature ( #ajjj grams ( wat] #a ,c41 r ?an #a gram #a ,c4 ,,table ,,%[+ ,,! ,,numb] ,,( ,,calories ,,furni%$ ,,by ,,"o ,,p\nd ,,( ,,v>i\s ,,foods ---------------------------------------- ------------ ,,food ,,calories,,food ,,calories ---------------------------------------- ------------ ,leg ( lean mutton #gij;,c>rots #baj ---------------------------------------- ------------ ,rib ( beef #aaej,lettuce #ij ---------------------------------------- ------------ ,%ad #chj,onion #bbe ---------------------------------------- ------------ ,*ick5 #eje;,cucumb] #hj ---------------------------------------- ------------ ,apples #bij;,almonds #cjcj ---------------------------------------- ------------ ,bananas #dfj,walnuts #ccjf ---------------------------------------- ------------ ,prunes #cgj,peanuts #befj ---------------------------------------- ------------ ,wat]melons #adj,oatmeal #dfgc ---------------------------------------- ------------ ,lima beans #egj,roll$ :eat #dage ---------------------------------------- ------------ ,beets #bae,mac>oni #affe ---------------------------------------- ------------ #eg4 ,v>i$ ,diet4 ,! human body is a mu* m v>i$ & complex ma*9e ?an any ev] devis$ by man2 p]sonal peculi>ities1 z well z fuel values1 influ5ce v l>gely ! diet ( an individual4 ,/rawb]ries are exclud$ f "s diets because ( a ra% :i* is produc$ on ! sk91 pork is exclud$ f o!r diets = a l reason2 caulifl[] is absolutely indige/ible to "s & is readily dige/$ by o!rs4 ,f practically e diet "s foods mu/ be exclud$1 no matt] :at ! fuel value ( ! sub/ance may be4 ,!n1 too1 !re are m uses = food ?an ! production ( heat4 ,tee? & bones & nails ne$ a con/ant supply ( m9]al matt]1 & m9]al matt] is frequ5tly f\nd 9 greate/ abundance 9 foods ( l[ fuel value1 su* z lettuce1 wat]cress1 etc41 ?\gh practically all foods yield at lea/ a small m9]al con/itu5t4 ,:5 fuel values alone are consid]$1 fruits h a l[ value1 b because ( ! flavor !y imp>t to o!r foods1 & because ( ! heal?ful influ5ce !y ex]cise 9 dige/ion1 !y _c be exclud$ f ! diet4 ,c>e %\ld be con/antly ex]cis$ to provide sub/antial foods ( high fuel value4 ,b ! nutritive foods %\ld be wisely supplem5t$ by su* foods z fruits1 ^: real value is "o ( indirect r !n direct s]vice4 #eh4 ,our ,bodies4 ,some:at z a h\se is compos$ ( a gr\p ( bricks1 or a s& heap ( gra9s ( s&1 ! human body is compos$ ( small divisions call$ cells4 ,ord9>ily we _c see ^! cells because ( _! m9ut5ess1 b if we exam9e a piece ( sk91 or a hair ( ! head1 or a t9y sliv] ( bone "u ! microscope1 we see t ea* ( ^! is compos$ ( a gr\p ( diff]5t cells4 ,a m]*ant1 wat*ful ab\t ! f95ess ( ! wool :i* he is pur*as+1 c\nts ) 8 l5s ! numb] ( ?reads to ! in*2 a physician1 :5 he wi%es1 c1 ) ! aid ( ! microscope1 exam9e ! cells 9 a muscle1 or 9 a piece ( fat1 or 9 a n]ve fib]4 ,n only is ! human body compos$ ( cells1 b s also are ! bodies ( all animals f ! t9y gnat :i* annoys u1 & ! fly :i* buzzes ar\nd u1 to ! mammo? creatures ( ! tropics4 ,^! cells d ! "w ( ! body1 ! bone cells build up ! skeleton1 ! nail cells =m ! f+] & toe nails1 ! lung cells take c>e ( brea?+1 ! muscle cells control motion1 & ! bra9 cells are responsible = ?\ght4 #ei4 ,:y we eat s ,mu*4 ,! cells ( ! body are con/antly1 day by day1 m9ute by m9ute1 break+ d[n & ne$+ repair1 are con/antly requir+ replacem5t by new cells1 &1 9 ! case ( ! *ild1 are cont9ually increas+ 9 numb]4 ,! repair ( an ord9>y ma*9e1 an eng9e1 = example1 is made at ! exp5se ( money1 b ! repair & replacem5t ( our human cell ma*9]y are accompli%$ at ! exp5se ( food4 ,m ?an "o ?ird ( all ! food we eat goes to ma9ta9 ! body cells1 & to keep !m 9 good ord]4 ,x is = ?is reason t we consume a l>ge quantity ( food4 ,if all ! food we eat 7 utiliz$ = en]gy1 ! h\sewife c\ld cook less1 & ! h\sefa!r c\ld save money on groc]'s & but*]'s bills4 ,if y put a ton ( coal 9 an eng9e1 its available en]gy is us$ to run ! eng9e1 b if ! eng9e 7 l ! human body1 "o ?ird ( ! ton w\ld be us$ up by ! eng9e 9 keep+ walls1 %afts1 :eels1 belts1 etc41 9 ord]1 & only two ?irds w\ld g t[>ds runn+ ! eng9e4 ,:5 an eng9e is n work+1 fuel is n consum$1 b ! body requires food = m]e exi/5ce1 reg>dless ( :e!r x does active "w or n4 ,:5 we "w1 ! cells break d[n m quickly1 & ! repair is great] ?an :5 we are at re/1 & h5ce !re is ne$ ( a l>g] am\nt ( food2 b :e!r we "w or n1 food is necess>y4 #fj4 ,! ,diff]5t ,foods4 ,! body is v exact+ 9 its dem&s1 requir+ c]ta9 def9ite foods = ! =mation & ma9t5ance ( its cells1 & o!r foods1 equally def9ite1 b ( diff]5t "*1 = heat2 our diet !re=e mu/ conta9 foods ( high fuel value1 & likewise foods ( cell-=m+ p[]4 ,al?\gh ! foods :i* we eat are ( widely diff]5t "*1 su* z fruits1 vegetables1 c]eals1 oils1 meats1 eggs1 milk1 *eese1 etc41 !y c be put into ?ree great classes3 ! c>bohydrates1 ! fats1 & ! proteids4 #fa4 ,! ,c>bohydrates4 ,corn1 :eat1 rye1 9 fact all c]eals & gra9s1 potatoes1 & mo/ vegetables are ri* 9 c>bohydrates2 z are also sug>1 molasses1 honey1 & maple sirup4 ,! foods ( ! fir/ gr\p are valuable because ( ! />* !y conta92 = example1 corn />*1 :eat />*1 potato />*4 ,! sub/ances ( ! second gr\p are valuable because ( ! sug> !y conta92 sug> conta9s ! maximum am\nt ( c>bohydrate4 ,9 ! sirups !re is a consid]able quantity ( sug>1 :ile 9 "s fruits x is pres5t 9 m or less dilute =m4 ,sweet pea*es1 apples1 grapes1 conta9 a mod]ate am\nt ( sug>2 wat]melons1 pe>s1 etc41 conta9 less4 ,mo/ ( our c>bohydrates are ( plant orig91 be+ f\nd 9 vegetables1 fruits1 c]eals1 & sirups4 ,c>bohydrates1 :e!r ( ! />* gr\p or ! sug> gr\p1 are compos$ *iefly ( ?ree elem5ts3 c>bon1 hydrog51 & oxyg52 !y are !re=e combu/ible1 & are great en]gy produc]s4 ,on ! o!r h&1 !y are wor?less = cell gr[? & repair1 & if we limit$ our diet to c>bohydrates1 we %\ld be l a man :o _h fuel b no eng9e capable ( us+ x4 #fb4 ,! ,fats4 ,! be/-kn[n fats are butt]1 l>d1 olive oil1 & ! fats ( meats1 *eese1 & *ocolate4 ,:5 we te/ fats = fuel values by means ( a calorimet] 7,fig4 #bf71 we f9d t !y yield twice z mu* heat z ! c>bohydrates1 b t !y burn out m quickly4 ,dwell]s 9 cold climates mu/ con/antly eat l>ge quantities ( fatty foods if !y are to keep _! bodies w>m & survive ! extreme cold4 ,cod liv] oil is an excell5t food m$ic9e1 & if tak5 9 w9t] s]ves to w>m ! body & to protect x aga9/ ! rigors ( cold wea!r4 ,! av]age p]son avoids fatty foods 9 summ]1 kn[+ f exp]i5ce t ri* foods make him w>m & uncom=table4 ,! h>d] we "w & ! cold] ! wea!r1 ! m food ( t k9d d we require2 x is said t a lumb]man do+ heavy out-(-door "w 9 cold climates ne$s ?ree times z mu* food z a city cl]k4 ,mo/ ( our fats1 l l>d & butt]1 are ( animal orig92 "s ( !m1 h[ev]1 l olive oil1 peanut butt]1 & coconut oil1 are ( plant orig94 ,illu/ration3 ,,fig4 #bg4--;a is ! am\nt ( fat necess>y to make "o calorie2 b is ! am\nt ( sug> or proteid necess>y to make "o calorie4 #fc4 ,! ,proteids4 ,! proteids are ! build+ foods1 furni%+ muscle1 bone1 sk9 cells1 etc41 & supply+ blood & o!r bodily fluids4 ,! be/-kn[n proteids are :ite ( egg1 curd ( milk1 & lean ( fi% & meat2 peas & beans h an abundant supply ( ?is sub/ance1 & nuts are ri* 9 x4 ,mo/ ( our proteids are ( animal orig91 b "s prote9 mat]ial is also f\nd 9 ! vegetable _w4 ,?is class ( foods conta9s c>bon1 oxyg51 & hydrog51 & 9 addition1 two sub/ances n f\nd 9 c>bohydrates or fats--namely1 sulphur & nitrog54 ,proteids always conta9 nitrog51 & h5ce !y are frequ5tly spok5 ( z nitrog5\s foods4 ,s9ce ! proteids conta9 all ! elem5ts f\nd 9 ! two o!r classes ( foods1 !y are able to contribute1 if necess>y1 to ! /ore ( bodily en]gy2 b _! ma9 function is upbuild+1 & ! diet %\ld be *os5 s t ! proteids d n h a d\ble task4 ,= an av]age man f\r ounces ( dry proteid matt] daily w suffice to keep ! body cells 9 normal condition4 ,x has be5 e/imat$ t #cjj1jjj1jjj blood cells alone ne$ daily repair or r5ewal4 ,:5 we consid] t ! blood is b "o "p ( ! body1 & t all organs & fluids h correspond+ requirem5ts1 we realize h[ va/ is ! "w to be done by ! food :i* we eat4 #fd4 ,mi/akes 9 ,buy+4 ,! body dem&s a daily ration ( ! ?ree classes ( food /uffs1 b x is = u to det]m9e f :at meats1 vegetables1 fruits1 c]eals1 etc41 ?is supply %all be obta9$ 7,figs4 #bh & #bi74 ,illu/ration3 ,,fig4 #bh4--,table ( food values4 ,illu/ration3 ,,fig4 #bi4--;,diagram %[+ ! diff]5ce 9 ! co/ ( ?ree foods :i* give ab\t ! same am\nt ( nutrition ea*4 ,g5]ally speak+1 meats are ! mo/ exp5sive foods we c pur*ase1 & h5ce %\ld be b\ght seldom & 9 small quantities4 ,_! place c be tak5 by beans1 peas1 potatoes1 etc41 & at less ?an a qu>t] ( ! co/4 ,! av]age ,am]ican family eats meat ?ree times a day1 :ile ! av]age family ( ! m cons]vative & old] c\ntries r>ely eats meat m ?an once a day4 ,! foll[+ tables indicate ! f9ancial loss aris+ f an unwise selection ( foods3-- ,,food ,,consum$--,,"o ,,week ,,family ,no4 #a ,,family ,no4 #b ---------------------------------------- -------------------------- #bj loaves ( bread #a4jj #ae lb4 fl\r1 bread #aj to #ab lb4 lo9 /eak home made 7skim milk us$7 4#de or meat ( simil> co/ #b4jj ,yea/1 %ort5+1 & #bj to #be lb4 rib roa/ skim milk 4#aj or simil> meat #d4dj #aj lb4 /eak 7r\nd1 ,hamburg] #d lb4 high-pric$ c]eal & "s lo97 #a4ej breakfa/ food1 #bj 4#hj #aj lb4 o!r meats1 boil+ ,cake & pa/ry pur*as$ #c4jj pieces1 rump roa/1 etc4 #a4jj #h lb4 butt]1 #cj #b4dj #e lb4 *eese1 #af 4#hj ,tea1 c(fee1 spices1 etc4 4#ge #e lb4 oatmeal 7bulk7 4#ae ,mu%rooms 4#ge #e lb4 beans 4#be ,cel]y #a4jj ,home-made cake & pa/ry #a4jj ,oranges #b4jj #f lb4 butt]1 #cj #a4hj ,potatoes 4#be #c lb4 home-made %ort5+ 4#be ,miscellane\s cann$ goods #b4jj ,tea1 c(fee1 & spices 4#dj ,milk 4#ej ,apples 4#ej ,miscellane\s foods #b4jj ,prunes 4#be #c doz4 eggs 4#fj ,potatoes 4#be -------,milk #a4jj #bc4de ,miscellane\s foods #a4jj #c doz4 eggs 4#fj ------ #aa4cj ---------------------------------------- --------------------------- ---------------------------------------- --------------------------- ,! tables %[ t "o family sp5ds ov] twice z mu* 9 ! pur*ase ( foods z ! o!r family1 & yet ! "o ^: food co/s ! less actually secures ! l>g] am\nt ( nutritive mat]ial & is bett] f$ ?an ! family :]e m money is exp5d$4--,f ,human ,foods1 ,snyd]4 ,! ,s\rce ( ! ,diff]5t ,foods4 ,all ( our food comes f ei!r ! plant _w or ! animal _w4 ,broadly speak+1 plants furni% ! c>bohydrates1 t is1 />* & sug>2 animals furni% ! fats & proteids4 ,b al?\gh vegetable foods yield c>bohydrates ma9ly1 "s ( !m1 l beans & peas1 conta9 l>ge quantities ( prote9 & c be sub/itut$ = meat )\t disadvantage to ! body4 ,o!r plant products1 su* z nuts1 h fat z _! mo/ abundant food con/itu5t4 ,! peanut1 = example1 conta9s #dc ( fat1 #cj ( proteids1 & only #ag ( c>bohydrates2 ! ,brazil nut has #fe ( fat1 #ag ( proteids1 & only #i ( c>bohydrates4 ,nuts make a good meat sub/itute1 & s9ce !y conta9 a fair am\nt ( c>bohydrates besides ! fats & prote9s1 !y supply all ( ! ess5tial food con/itu5ts & =m a well-balanc$ food4 ,,*apt] ,,vi ,,wat] #fe4 ,de/ructive ,action ( ,wat]4 ,! action ( wat] 9 /ream & sea1 9 spr+s & wells1 is evid5t to all2 b ! activity ( gr\nd wat]--t is1 ra9 wat] :i* s9ks into ! soil & rema9s !re--is little kn[n 9 g5]al4 ,! real activity ( gr\nd wat] is due to its great solv5t p[]2 e "t we put sug> into tea or soap into wat] we are us+ wat] z a solv5t4 ,:5 ra9 falls1 x dissolves sub/ances float+ 9 ! atmosph]e1 & :5 x s9ks into ! gr\nd & becomes gr\nd wat]1 x dissolves mat]ial out ( ! rock :i* x enc\nt]s 7,fig4 #cj74 ,we "k t wat] conta9s "s m9]al matt]1 because kettles 9 :i* wat] is boil$ acquire 9 a %ort "t a cru/ or coat+ on ! inside4 ,?is cru/ is due to ! accumulation 9 ! kettle ( m9]al matt] :i* 0 9 solution 9 ! wat]1 b :i* 0 left beh9d :5 ! wat] evaporat$4 7,see ,section #be47 ,illu/ration3 ,,fig4 #cj4--,%[+ h[ caves & holes are =m$ by ! solv5t action ( wat]4 ,! am\nt ( dissolv$ m9]al matt] pres5t 9 "s wells & spr+s is surpris+ly great2 ! fam\s spr+s ( ,ba?1 ,engl&1 conta9 s mu* m9]al matt] 9 solution1 t a column #i feet 9 diamet] & #adj feet high c\ld be built out ( ! m9]al matt] conta9$ 9 ! wat] consum$ ye>ly by ! t[nspeople4 ,illu/ration3 ,,fig4 #ca4--,! "w ( wat] z a solv5t4 ,rocks & m9]als are n all equally soluble 9 wat]2 "s are s little soluble t x is ye>s be=e any *ange becomes app>5t1 & ! sub/ances are said to be insoluble1 yet 9 reality !y are sl[ly dissolv+4 ,o!r rocks1 l lime/one1 are s readily soluble 9 wat] t f ! small pores & cavities eat5 out by ! wat]1 !re may develop 9 long c5turies1 caves & cav]ns 7,fig4 #cj74 ,mo/ rock1 l granite1 conta9s sev]al sub/ances1 "s ( :i* are readily soluble & o!rs ( :i* are n readily soluble2 9 su* rocks a peculi> appe>ance is pres5t$1 due to ! rapid disappe>ance ( ! soluble sub/ance1 & ! p]si/5ce ( ! m resi/ant sub/ance 7,fig4 #ca74 ,we see t ! solv5t p[] ( wat] is con/antly caus+ *anges1 dissolv+ "s m9]al sub/ances1 & leav+ o!rs practically unt\*$2 eat+ out crevices ( v>i\s %apes & sizes1 & by gradual solution ?r\gh unnumb]$ ye>s enl>g+ ^! crevices into wond]ful caves1 su* z ! ,mammo? ,cave ( ,k5tucky4 #ff4 ,con/ructive ,action ( ,wat]4 ,wat] does n always act z a de/ructive ag5t2 :at x breaks d[n 9 "o place x builds up 9 ano!r4 ,x does ?is by means ( precipitation4 ,wat] dissolves salt1 & also dissolves lead nitrate1 b if a salt solution is mix$ ) a lead nitrate solution1 a solid :ite sub/ance is =m$ 9 ! wat] 7,fig4 #cb74 ,?is =mation ( a solid sub/ance f ! m+l+ ( two liquids is call$ precipitation2 su* a process occurs daily 9 ! rocks b5ea? ! surface ( ! e>?4 7,see ,laboratory ,manual47 ,illu/ration3 ,,fig4 #cb4--;,f ! m+l+ ( two liquids a solid is sometimes =m$4 ,suppose wat] f diff]5t s\rces ent]s a crack 9 a rock1 br++ diff]5t sub/ances 9 solution2 !n ! m+l+ ( ! wat]s may cause precipitation1 & ! solid ?us =m$ w be deposit$ 9 ! crack & fill x up4 ,h5ce1 :ile gr\nd wat] t5ds to make rock por\s & weak by dissolv+ out ( x l>ge quantities ( m9]al matt]1 x also t5ds "u o!r conditions to make x m compact because x deposits 9 cracks1 crevices1 & pores ! m9]al matt] precipitat$ f solution4 ,^! two =ces are con/antly at "w2 9 "s places ! de/ructive action is m prom95t1 9 o!r places ! con/ructive action2 b always ! result is to *ange ! "* ( ! orig9al sub/ance4 ,:5 ! m9]al matt] precipitat$ f ! solutions is deposit$ 9 cracks1 ve9s are =m$ 7,fig4 #cc71 :i* may consi/ ( ! ore ( diff]5t metals1 su* z gold1 silv]1 copp]1 lead1 etc4 ,man is almo/ entirely dep5d5t ^u ^! ve9s = ! supply ( metal ne$$ 9 ! v>i\s indu/ries1 because 9 ! orig9al condition ( ! rocks1 ! metallic sub/ances are s scatt]$ t !y _c be pr(itably extract$4 ,illu/ration3 ,,fig4 #cc4--,m9]al matt] precipitat$ f solution is deposit$ 9 crevices & =ms ve9s4 ,naturally1 ! ve9s !mselves are n compos$ ( "o sub/ance alone1 because sev]al diff]5t precipitates may be =m$4 ,b !re is a decid$ gr\p+ ( valuable metals1 & ^! c !n be readily sep>at$ by means ( electricity4 #fg4 ,/reams4 ,/reams usually c>ry mud & s& along ) !m2 ?is is p>ticul>ly well se5 aft] a /orm :5 riv]s & brooks are muddy4 ,! puddles :i* collect at ! foot ( a hill aft] a /orm are muddy because ( ! p>ticles ( soil ga!r$ by ! wat] z x runs d[n ! hill4 ,! p>ticles are n dissolv$ 9 ! wat]1 b are held !re 9 susp5sion1 z we call x te*nically4 ,! riv] made muddy aft] a /orm by susp5d$ p>ticles usually becomes cle> & transp>5t aft] x has travel$ onw>d = miles1 because1 z x travels1 ! p>ticles drop to ! bottom & are deposit$ !re4 ,h5ce1 mat]ials susp5d$ 9 ! wat] are borne along & deposit$ at v>i\s places 7,fig4 #cd74 ,! am\nt ( deposition by l>ge riv]s is s great t 9 "s places *annels fill up & mu/ be dr$g$ annually1 & vessels are sometimes caught 9 ! deposit & h to be t[$ away4 ,runn+ wat] 9 ! =m ( /reams & riv]s1 by c>ry+ s& p>ticles1 /ones1 & rocks f high slopes & deposit+ !m at l[] levels1 we>s away l& at "o place & builds x up at ano!r1 & nev] ceases 9 its "w ( *ang+ ! nature ( ! e>?'s surface 7,fig4 #ce74 ,illu/ration3 ,,fig4 #cd4--;,deposit left by runn+ wat]4 ,illu/ration3 ,,fig4 #ce4--,wat] by its action con/antly *anges ! "* ( ! l&4 #fh4 ,relation ( ,wat] to ,human ,life4 ,wat] is "o ( ! mo/ ess5tial ( food mat]ials1 & :e!r we dr9k mu* or little wat]1 we nev]!less get a great deal ( x4 ,! l>g] "p ( _m ( our foods is compos$ ( wat]2 m ?an half ( ! weight ( ! meat we eat is made up ( wat]2 & vegetables are (t5 m ?an n9e t5?s wat]4 7,see ,laboratory ,manual47 ,asp>agus & tomatoes h ov] #ij p] c5t4 ( wat]1 & mo/ fruits are m ?an ?ree f\r?s wat]2 ev5 bread1 :i* conta9s z little wat] z any ( our common foods1 is ab\t "o ?ird wat] 7,fig4 #cf74 ,illu/ration3 ,,fig4 #cf4--;,diagram ( ! composition ( a loaf ( bread & ( a potato3 #a4 a%2 #b1 food2 #c1 wat]4 ,)\t wat]1 solid food mat]ial1 al?\gh pres5t 9 ! body1 w\ld n be 9 a condition suitable = bodily use4 ,an abundant supply ( wat] enables ! food to be dissolv$ or susp5d$ 9 x1 & 9 solution ! food mat]ial is easily di/ribut$ to all p>ts ( ! body4 ,fur!r1 wat] assi/s 9 ! removal ( ! daily bodily wa/es1 & ?us rids ! sy/em ( f\l & poison\s sub/ances4 ,! human body itself consi/s l>gely ( wat]2 inde$1 ab\t two ?irds ( our own weight is wat]4 ,! con/ant repl5i%+ ( ?is l>ge quantity is necess>y to life1 & a consid]able am\nt ( ! necess>y supply is furni%$ by foods1 p>ticul>ly ! fruits & vegetables4 ,b :ile ! supply furni%$ by ! daily food is consid]able1 x is by no means suffici5t1 & %\ld be supplem5t$ by good dr9k+ wat]4 #fi4 ,wat] & its ,dang]s4 ,our dr9k+ wat] comes f f> & ne>1 & z x moves f place to place1 x c>ries ) x 9 solution or susp5sion any?+ :i* x c f9d1 :e!r x be animal1 vegetable1 or m9]al matt]4 ,! p[] ( wat] to ga!r up matt] is s great t ! av]age dr9k+ wat] conta9s #bj to #ij gra9s ( solid matt] p] gallon2 t is1 if a gallon ( ord9>y dr9k+ wat] is left to evaporate1 a residue ( #bj to #ij gra9s w be left4 7,see ,laboratory ,manual47 ,z wat] runs d[n a hill slope 7,fig4 #cg71 x c>ries ) x ! fil? ga!r$ f acres ( l&2 c>ries ) x ! refuse ( /able1 b>n1 & kit*52 & too (t5 ?is impure surface wat] jo9s ! /reams :i* supply our cities4 ,lakes & riv]s :i* furni% dr9k+ wat] %\ld be c>efully protect$ f surface dra9+2 t is1 f wat] :i* has fl[$ ov] ! l& & has ?us accumulat$ ! wa/e ( pa/ure & /able &1 x may be1 ( dump+ gr\nd4 ,illu/ration3 ,,fig4 #cg4--;,z wat] fl[s ov] ! l&1 x ga!rs fil? & disease g]ms4 ,x is n necess>y t wat] %\ld be absolutely free f all =eign sub/ances 9 ord] to be safe = daily use 9 dr9k+2 a limit$ am\nt ( m9]al matt] is n injuri\s & may sometimes be really b5eficial4 ,x is ! pres5ce ( animal & vegetable matt] t causes real dang]1 & x is kn[n t typhoid fev] is due l>gely to su* impurities pres5t 9 ! dr9k+ wat]4 #gj4 ,me?ods ( ,purification4 ,wat] is improv$ by any ( ! foll[+ me?ods3-- 7a7 ,boil+4 ,! heat ( boil+ de/roys animal & vegetable g]ms4 ,h5ce wat] t has be5 boil$ a few m9utes is safe to use4 ,?is is ! mo/ practical me?od ( purification 9 ! home1 & is v effici5t4 ,! boil$ wat] %\ld be kept 9 clean1 cork$ bottles2 o!rwise =eign sub/ances f ! atmosph]e rent] ! wat]1 & ! advantage ga9$ f boil+ is lo/4 7b7 ,di/illation4 ,by ?is me?od pure wat] is obta9$1 b ?is me?od ( purification _c be us$ conv5i5tly 9 ! home 7,section #be74 7c7 ,filtration4 ,9 filtration1 ! wat] is =c$ ?r\gh porcela9 or o!r por\s sub/ances :i* all[ ! passage ( wat]1 b :i* hold back ! m9ute =eign p>ticles susp5d$ 9 ! wat]4 7,see ,laboratory ,manual47 ,! filt]s us$ 9 ord9>y dwell+s are ( /one1 asbe/os1 or *>coal4 ,!y are (t5 valueless1 because !y soon become *ok$ & _c be prop]ly clean$4 ,! filtration plants own$ & op]at$ by l>ge cities are usually safe2 !re is c>eful sup]vision ( ! filt]s1 & frequ5t & effective clean+s are made4 ,9 _m cities ! filtration sy/em is s good t private c>e ( ! wat] supply is unnecess>y4 #ga4 ,! ,s\rce ( ,wat]4 ,9 ! beg9n+1 ! e>? 0 /or$ ) wat] j z x 0 ) metal1 rock1 etc4 ,"s ( ! wat] gradually took ! =m ( riv]s1 lakes1 /reams1 & wells1 z n[1 & x is ?is orig9al supply ( wat] :i* furni%es u all t we h to-day4 ,we qu>ry to obta9 /one & m>ble = build+1 & we fa%ion ! e>?'s treasures into =ms ( our own1 b we _c create ^! ?+s4 ,we bore into ! gr\nd & drill wells 9 ord] to obta9 wat] f hidd5 s\rces2 we utilize rapidly fl[+ /reams to drive ! :eels ( comm]ce1 b ! total am\nt ( wat] rema9s practically un*ang$4 ,! wat] :i* fl[s on ! e>? is con/antly *ang+ its =m2 ! heat ( ! sun causes x to evaporate1 or to become vapor1 & to m+le ) ! atmosph]e4 ,9 "t1 ! vapor cools1 cond5ses1 & falls z sn[ or ra92 ! wat] :i* is ?us return$ to ! e>? fe$s our riv]s1 lakes1 spr+s1 & wells1 & ^! 9 turn supply wat] to man4 ,:5 wat] falls ^u a field1 x soaks into ! gr\nd1 or collects 9 puddles :i* sl[ly evaporate1 or x runs (f & dra9s into small /reams or into riv]s4 ,t :i* soaks into ! gr\nd is ! mo/ valuable because x rema9s on ! e>? longe/ & is ! pure/4 ,illu/ration3 ,,fig4 #ch4--;,h[ spr+s are =m$4 ,a1 por\s lay]2 ,b1 non-por\s lay]2 ,c1 spr+4 ,wat] :i* soaks into ! gr\nd moves sl[ly d[nw>d & aft] a long] or %ort] j\rney1 meets ) a non-por\s lay] ( rock ?r\gh :i* x _c pass1 & :i* effectually h9d]s its d[nw>d passage4 ,9 su* regions1 !re is an accumulation ( wat]1 & a well dug !re w\ld h an abundant supply ( wat]4 ,! non-por\s lay] is r>ely level1 & h5ce ! wat] ^: v]tical pa? is ob/ruct$ does n back up on ! soil1 b fl[s d[n hill p>allel ) ! ob/ruct+ non-por\s lay]1 & 9 "s di/ant region makes an outlet = itself1 =m+ a spr+ 7,fig4 #ch74 ,! /reams orig9at+ 9 ! spr+s fl[ ?r\gh ! l& & ev5tually jo9 l>g] /reams or riv]s2 f ! surface ( /reams & riv]s evaporation occurs1 ! wat] once m becomes vapor & passes into ! atmosph]e1 :]e x is cond5s$ & aga9 falls to ! e>?4 ,wat] :i* has filt]$ ?r\gh _m feet ( e>? is f> pur] & saf] ?an t :i* fell directly into ! riv]s1 or :i* ran (f f ! l& & jo9$ ! surface /reams )\t pass+ ?r\gh ! soil4 #gb4 ,! ,composition ( ,wat]4 ,wat] 0 long ?\ght to be a simple sub/ance1 b t[>d ! end ( ! eighte5? c5tury x 0 f\nd to consi/ ( two q diff]5t sub/ances1 oxyg5 7,o7 & hydrog5 7,h47 ,illu/ration3 ,,fig4 #ci4--,! decomposition ( wat]4 ,if we s5d an electric curr5t ?r\gh wat] 7acidulat$ to make x a good conductor71 z %[n 9 ,figure #ci1 we see bubbles ( gas ris+ f ! end ( ! wire by :i* ! curr5t ent]s ! wat]1 & o!r bubbles ( gas ris+ f ! end ( ! wire by :i* ! curr5t leaves ! wat]4 ,^! gases h evid5tly come f ! wat] & are ! sub/ances ( :i* x is compos$1 because ! wat] beg9s to disappe> z ! gases are =m$4 ,if we place ov] ea* end ( ! wire an inv]t$ j> fill$ ) wat]1 ! gases are easily collect$4 ,! fir/ ?+ we notice is t !re is always twice z mu* ( "o gas z ( ! o!r2 t is1 wat] is compos$ ( two sub/ances1 "o ( :i* is always pres5t 9 twice z l>ge quantities z ! o!r4 #gc4 ,! ,composition ( ,wat]4 ,on te/+ ! gases into :i* wat] is brok5 up by an electric curr5t1 we f9d !m to be q diff]5t4 ,"o proves to be oxyg51 a sub/ance ) :i* we are already famili>4 ,! o!r gas1 hydrog51 is new to u & is int]e/+ z be+ ! lighte/ kn[n sub/ance1 be+ ev5 light] ?an a fea!r4 ,an important fact ab\t hydrog5 is t 9 burn+ x gives z mu* heat z five times its weight ( coal4 ,its flame is blue & almo/ invisible by daylight1 b int5sely hot4 ,if f9e plat9um wire is plac$ 9 an ord9>y gas flame1 x does n melt1 b if plac$ 9 a flame ( burn+ hydrog51 x melts v quickly4 #gd4 ,h[ to prep>e ,hydrog54 ,!re are _m diff]5t me?ods ( prep>+ hydrog51 b ! easie/ laboratory me?od is to p\r sulphuric acid1 or hydro*loric acid1 on z9c %av+s & to collect 9 a bottle ! gas :i* is giv5 (f4 ,?is gas proves to be colorless1 ta/eless1 & odorless4 7,see ,laboratory ,manual47 ,,*apt] ,,vii ,,air #ge4 ,! ,in/ability ( ! ,air4 ,we are usually n consci\s ( ! air ar\nd u1 b sometimes we realize t ! air is heavy1 :ile at o!r times we feel ! brac+ effect ( ! atmosph]e4 ,we live 9 an ocean ( air z truly z fi% inhabit an ocean ( wat]4 ,if y h ev] be5 at ! sea%ore y "k t ! ocean is nev] /ill = a second2 sometimes ! waves surge back & =? 9 angry fury1 at o!r times ! waves glide g5tly 9 to ! %ore & ! surface is z smoo? z glass2 b we "k t !re is p]petual motion ( ! wat] ev5 :5 ! ocean is 9 its g5tle/ moods4 ,g5]ally our atmosph]e is quiet1 & we are utt]ly unconsci\s ( x2 at o!r times we are pa9fully aw>e ( x1 because ( its furi\s w9ds4 ,!n aga9 we are oppress$ by x because ( ! va/ quantity ( vapor :i* x holds 9 ! =m ( fog1 or mi/4 ,! atmosph]e ar\nd u is z re/less & v>y+ z is ! wat] ( ! sea4 ,! air at ! top ( a high t[] is v diff]5t f ! air at ! base ( ! t[]4 ,n only does ! atmosph]e v>y greatly at diff]5t altitudes1 b x v>ies at ! same place f "t to "t1 at "o p]iod be+ heavy & raw1 at ano!r be+ fre% & invigorat+4 ,w9ds1 temp]ature1 & humidity all h a %>e 9 det]m9+ atmosph]ic conditions1 & no "o ( ^! plays a small "p4 #gf4 ,! ,"* ( ! ,air4 ,! atmosph]e :i* envelops u at all times ext5ds m ?an fifty miles above u1 its height be+ f> great] ?an ! greate/ dep?s ( ! sea4 ,?is atmosph]e v>ies f place to place2 at ! sea level x is heavy1 on ! m\nta9 top less heavy1 & f> above ! e>? x is s light t x does n conta9 en\gh oxyg5 to p]mit man to live4 ,figure #dj illu/rates by a pile ( pill[s h[ ! pressure ( ! air v>ies f level to level4 ,illu/ration3 ,,fig4 #dj4--,to illu/rate ! decrease 9 pressure ) height4 ,sea level is a l[ portion ( ! e>?'s surface1 h5ce at sea level !re is a high column ( air1 & a heavy air pressure4 ,z "o passes f sea level to m\nta9 top a gradual b /eady decrease 9 ! height ( ! air column occurs1 & h5ce a gradual b def9ite less5+ ( ! air pressure4 ,illu/ration3 ,,fig4 #da4--,! wat] 9 ! tube is at ! same level z t 9 ! glass4 #gg4 ,air ,pressure4 ,if an empty tube 7,fig4 #da7 is plac$ upright 9 wat]1 ! wat] w n rise 9 ! tube1 b if ! tube is put 9 wat] & ! air is !n drawn out ( ! tube by ! m\?1 ! wat] w rise 9 ! tube 7,fig4 #db74 ,?is is :at happ5s :5 we take lemonade ?r\gh a /raw4 ,:5 ! air is )drawn f ! /raw by ! m\?1 ! pressure )9 ! /raw is r$uc$1 & ! liquid is =c$ up ! /raw by ! air pressure on ! surface ( ! liquid 9 ! glass4 ,ev5 ! anci5t ,greeks & ,romans knew t wat] w\ld rise 9 a tube :5 ! pressure )9 ! tube 0 r$uc$1 & h5ce !y tri$ to obta9 wat] f wells 9 ?is fa%ion1 b ! wat] c\ld nev] be rais$ high] ?an #cd feet4 ,let u see :y wat] c\ld rise #cd feet & no m4 ,if an empty pipe is plac$ 9 a ci/]n ( wat]1 ! wat] 9 ! pipe does n rise above ! level ( ! wat] 9 ! ci/]n4 ,if1 h[ev]1 ! pressure 9 ! tube is remov$1 ! wat] 9 ! tube w rise to a height ( #cd feet approximately4 ,if n[ ! air pressure 9 ! tube is re/or$1 ! wat] 9 ! tube s9ks aga9 to ! level ( t 9 ! ci/]n4 ,! air press+ on ! liquid 9 ! ci/]n t5ds to pu% "s liquid up ! tube1 b ! air press+ on ! wat] 9 ! tube pu%es d[nw>ds1 & t5ds to keep ! liquid f ris+1 & ^! two pressures balance ea* o!r4 ,:51 h[ev]1 ! pressure )9 ! tube is r$uc$1 ! liquid rises because ( ! unbalanc$ pressure :i* acts on ! wat] 9 ! ci/]n4 ,illu/ration3 ,,fig4 #db4--,wat] rises 9 ! tube :5 ! air is )drawn4 ,illu/ration3 ,,fig4 #dc4--,! air supports a column ( m]cury #cj in*es high4 ,! column ( wat] :i* c be rais$ ?is way is approximately #cd feet1 sometimes a trifle m1 sometimes a trifle less4 ,if wat] 7 twice z heavy1 j half z high a column c\ld be support$ by ! atmosph]e4 ,m]cury is ab\t ?irte5 times z heavy z wat] &1 !re=e1 ! column ( m]cury support$ by ! atmosph]e is ab\t "o ?irte5? z high z ! column ( wat] support$ by ! atmosph]e4 ,?is c easily be demon/rat$4 ,fill a glass tube ab\t a y>d long ) m]cury1 close ! op5 end ) a f+]1 & quickly ins]t ! end ( ! inv]t$ tube 9 a di% ( m]cury 7,fig4 #dc74 ,:5 ! f+] is remov$1 ! m]cury falls some:at1 leav+ an empty space 9 ! top ( ! tube4 ,if we measure ! column 9 ! tube1 we f9d its height is ab\t "o ?irte5? ( #cd feet or #cj in*es1 exactly :at we %\ld expect4 ,s9ce !re is no air pressure )9 ! tube1 ! atmosph]ic pressure on ! m]cury 9 ! di% is balanc$ solely by ! m]cury )9 ! tube1 t is1 by a column ( m]cury #cj in*es high4 ,! %ortness ( ! m]cury column z comp>$ ) t ( wat] makes ! m]cury m conv5i5t = bo? exp]im5tal & practical purposes4 7,see ,laboratory ,manual47 #gh4 ,! ,b>omet]4 ,s9ce ! pressure ( ! air *anges f "t to "t1 ! height ( ! m]cury w *ange f day to day1 & h\r to h\r4 ,:5 ! air pressure is heavy1 ! m]cury w t5d to be high2 :5 ! air pressure is l[1 ! m]cury w %[ a %ort] column2 & by read+ ! level ( ! m]cury "o c le>n ! pressure ( ! atmosph]e4 ,if a glass tube & di% ( m]cury are atta*$ to a bo>d & ! di% ( m]cury is inclos$ 9 a case = protection f moi/ure & dirt1 & fur!r if a scale ( in*es or c5timet]s is made on ! upp] portion ( ! bo>d1 we h a m]curial b>omet] 7,fig4 #dd74 ,illu/ration3 ,,fig4 #dd4--;,a simple b>omet]4 ,if ! b>omet] is tak5 to ! m\nta9 top1 ! column ( m]cury falls gradually dur+ ! asc5t1 %[+ t z "o asc5ds1 ! pressure decreases 9 agreem5t ) ! /atem5t 9 ,section #gf4 ,obs]vations simil> to ^! 7 made by ,torricelli z e>ly z ! sixte5? c5tury4 ,tak+ a b>ometric read+ consi/s 9 measur+ ! height ( ! m]cury column4 #gi4 ,a ,portable ,b>omet]4 ,! m]cury b>omet] is l>ge & inconv5i5t to c>ry f place to place1 & a m portable =m has be5 devis$1 kn[n z ! an]oid b>omet] 7,fig4 #de74 ,?is =m ( b>omet] is extremely s5sitive2 inde$1 x is s delicate t x %[s ! slight diff]5ce betwe5 ! pressure at ! table top & ! pressure at ! floor level1 :]eas ! m]cury b>omet] w\ld indicate only a mu* great] v>iation 9 atmosph]ic pressure4 ,! an]oid b>omet]s are frequ5tly made no l>g] ?an a wat* & c be c>ri$ conv5i5tly 9 ! pocket1 b !y get out ( ord] easily & mu/ be frequ5tly readju/$4 ,! an]oid b>omet] is an air-tight box ^: top is made ( a ?9 metallic disk :i* b5ds inw>d or outw>d accord+ to ! pressure ( ! atmosph]e4 ,if ! atmosph]ic pressure increases1 ! ?9 disk is pu%$ slightly inw>d2 if1 on ! o!r h&1 ! atmosph]ic pressure decreases1 ! pressure on ! metallic disk decreases & ! disk is n press$ s f> inw>d4 ,! motion ( ! disk is small1 & x w\ld be impossible to calculate *anges 9 atmosph]ic pressure f ! motion ( ! disk1 )\t "s me*anical device to make ! slight *anges 9 motion p]ceptible4 ,illu/ration3 ,,fig4 #de4--;,an]oid b>omet]4 ,9 ord] to magnify ! slight *anges 9 ! position ( ! disk1 ! ?9 face is connect$ ) a sy/em ( lev]s1 or :eels1 :i* multiplies ! *anges 9 motion & communicates !m to a po9t] :i* moves ar\nd a graduat$ circul> face4 ,9 ,figure #de ! real b>omet] is sc>cely visible1 be+ securely inclos$ 9 a metal case = protection2 ! pr9ciple1 h[ev]1 c be und]/ood by ref]5ce to ,figure #df4 ,illu/ration3 ,,fig4 #df4--,pr9ciple ( ! an]oid b>omet]4 #hj4 ,! ,weight ( ! ,air4 ,we h se5 t ! pressure ( ! atmosph]e at any po9t is due to ! weight ( ! air column :i* /ret*es f t po9t f> up into ! sky above4 ,?is weight v>ies slightly f "t to "t & f place to place1 b x is equal to ab\t #ae p\nds to ! squ>e in* z %[n by actual measurem5t4 ,x comes to u z a surprise sometimes t air actually has weight2 = example1 a mass ( #ab cubic feet ( air at av]age pressure weighs #a p\nd1 & ! air 9 a l>ge assembly hall weighs m ?an #a ton4 ,we are practically nev] consci\s ( ?is really enorm\s pressure ( ! atmosph]e1 :i* is ex]t$ ov] e in* ( our bodies1 because ! pressure is ex]t$ equally ov] ! outside & ! inside ( our bodies2 ! cells & tissues ( our bodies conta9+ gases "u atmosph]ic pressure4 ,if1 h[ev]1 ! f+] is plac$ ov] ! op5 end ( a tube & ! air is suck$ out ( ! tube by ! m\?1 ! fle% ( ! f+] bulges into ! tube because ! pressure )9 ! f+] is no long] equaliz$ by ! usual atmosph]ic pressure 7,fig4 #dg74 ,illu/ration3 ,,fig4 #dg4--,! fle% bulges out4 ,aronauts h nev] asc5d$ mu* high] ?an #g miles2 at t height ! b>omet] /&s at #g in*es in/ead ( at #cj in*es1 & ! int]nal pressure 9 cells & tissues is n balanc$ by an equal ext]nal pressure4 ,! unequaliz$ int]nal pressure =ces ! blood to ! surface ( ! body & causes rupture ( blood vessels & o!r physical difficulties4 #ha4 ,use ( ! ,b>omet]4 ,*anges 9 air pressure are v closely connect$ ) *anges 9 ! wea!r4 ,! b>omet] does n directly =etell ! wea!r1 b a l[ or fall+ pressure1 accompani$ by a simultane\s fall ( ! m]cury1 usually prec$es f\l wea!r1 :ile a ris+ pressure1 accompani$ by a simultane\s rise 9 ! m]cury1 usually prec$es fair wea!r4 ,! b>omet] is n an infallible prophet1 b x is ( great assi/ance 9 pr$ict+ ! g5]al tr5d ( ! wea!r4 ,!re are c]ta9 *anges 9 ! b>omet] :i* foll[ no kn[n laws1 & :i* all[ ( no safe pr$ictions1 b on ! o!r h&1 g5]al future conditions = a few days ahead c be fairly accurately det]m9$4 ,figure #dh %[s a b>ograph or self-regi/]+ b>omet] :i* automatically regi/]s air pressure4 ,illu/ration3 ,,fig4 #dh4--;,b>ograph4 ,seaport t[ns 9 p>ticul>1 b all cities1 l>ge or small1 & villages too1 are on reque/ notifi$ by ! ,unit$ ,/ates ,wea!r ,bureau t5 h\rs or m 9 advance1 ( probable wea!r conditions1 & 9 ?is way precautions are tak5 :i* annually save millions ( doll>s & hundr$s ( lives4 ,i recollect a summ] sp5t on a ,new ,hamp%ire f>m1 & "k t an old f>m] />t$ 8 f>m h&s hay+ by moonlight at two o'clock 9 ! morn+1 because ! ,special ,f>m]'s ,wea!r ,=eca/ ( ! prec$+ ev5+ _h pr$ict$ ra9 = ! foll[+ day4 ,8 reliance on ! wea!r report 0 n misplac$1 s9ce ! /orm came ) full =ce at noon4 ,sail+ vessels1 ya*ts1 & fi%+ dories rema9 )9 rea* ( port if ! b>omet] =etells /orms4 ,illu/ration3 ,,fig4 #di4--;,iso!rms4 #hb4 ,isob>ic & ,iso!rmal ,l9es4 ,if a l9e 7 drawn ?r\gh all po9ts on ! surface ( ! e>? hav+ an equal b>ometric pressure at ! same "t1 su* a l9e w\ld be call$ an isob>4 ,= example1 if ! height ( b>omet]s 9 diff]5t localities is obs]v$ at exactly ! same "t1 & if all ! cities & t[ns :i* h ! same pressure are connect$ by a l9e1 ! curv$ l9es w be call$ isob>s4 ,by ! aid ( ^! l9es ! b>ometric conditions ov] a l>ge area c be /udi$4 ,! ,wea!r ,bureau at ,wa%+ton relies greatly on ^! isob>s = /atem5ts conc]n+ local & di/ant wea!r =eca/s1 any %ift 9 isob>ic l9es %[+ *ange 9 atmosph]ic pressure4 ,if a l9e is drawn ?r\gh all po9ts on ! surface ( ! e>? hav+ ! same temp]ature at ! same in/ant1 su* a l9e is call$ an iso!rm 7,fig4 #di74 #hc4 ,wea!r ,maps4 ,scatt]$ ov] ! ,unit$ ,/ates are ab\t #abe ,gov]nm5t ,wea!r ,/ations1 at ea* ( :i* ?ree times a day1 at ! same in/ant1 accurate obs]vations ( ! wea!r are made4 ,^! obs]vations1 :i* consi/ ( ! read+ ( b>omet] & !rmomet]1 ! det]m9ation ( ! velocity & direction ( ! w9d1 ! det]m9ation ( ! humidity & ( ! am\nt ( ra9 or sn[1 are telegraph$ to ! *ief wea!r (ficial at ,wa%+ton4 ,f ! reports ( w9d /orms1 excessive ra9fall1 hot waves1 cle>+ wea!r1 etc41 & _! rate ( travel1 ! *ief (ficials pr$ict :]e ! /orms1 etc41 w be at a def9ite future "t4 ,9 ! ,unit$ ,/ates1 ! g5]al movem5t ( wea!r conditions1 z indicat$ by ! b>omet]1 is f we/ to ea/1 & if a c]ta9 wea!r condition prevails 9 ! we/1 x is probable t x w advance ea/w>d1 al?\gh ) decid$ modifications4 ,s _m influ5ces modify atmosph]ic conditions t unfail+ pr$ictions are impossible1 b ! ,wea!r ,bureau pr$ictions prove true 9 ab\t eight cases out ( t54 ,! reports made out at ,wa%+ton are telegraph$ on reque/ to cities 9 ?is c\ntry1 & are frequ5tly publi%$ 9 ! daily pap]s1 along ) ! =eca/ ( ! local (fice4 ,a c>eful /udy ( ^! reports enables "o to =eca/ to "s ext5t ! probable wea!r conditions ( ! day4 ,! fir/ impression ( a wea!r map 7,fig4 #ej7 ) its v>i\s l9es & signals is apt to be "o ( confusion1 & ! temptation comes to ab&on ! task ( f9d+ an und]ly+ plan ( ! wea!r4 ,if "o w be> 9 m9d a few simple rules1 ! complexity ( ! wea!r map w disappe> & a glance at ! map w give "o in=mation conc]n+ g5]al wea!r conditions j z a glance at ! !rmomet] 9 ! morn+ w give "s indication ( ! probable temp]ature ( ! day4 7,see ,laboratory ,manual47 ,illu/ration3 ,,fig4 #ej4 wea!r ,map ,on ! wea!r map solid l9es repres5t isob>s & dott$ l9es repres5t iso!rms4 ,! direction ( ! w9d at any po9t is indicat$ by an arr[ :i* flies ) ! w9d2 & ! /ate ( ! wea!r--cle>1 p>tly cl\dy1 cl\dy1 ra91 sn[1 etc4--is indicat$ by symbols4 #hd4 ,compon5ts ( ! ,air4 ,! be/ kn[n con/itu5t ( ! air is oxyg51 already famili> to u z ! fe$] ( ! fire )\t & )9 ! body4 ,almo/ "o fif? ( ! air :i* envelops u is made up ( ! life-giv+ oxyg54 ,?is supply ( oxyg5 9 ! air is con/antly be+ us$ up by brea?+ animals & gl[+ fires1 & unless !re 7 "s con/ant s\rce ( additional supply1 ! quantity ( oxyg5 9 ! air w\ld soon become insuffici5t to support animal life4 ,! unfail+ con/ant s\rce ( atmosph]ic oxyg5 is plant life 7,section #dh74 ,! leaves ( plants absorb c>bon dioxide f ! air1 & break x up into oxyg5 & c>bon4 ,! plant makes use ( ! c>bon b x rejects ! oxyg51 :i* passes back into ! atmosph]e ?r\gh ! pores ( ! leaves4 ,al?\gh oxyg5 con/itutes only "o fif? ( ! atmosph]e1 x is "o ( ! mo/ abundant & widely scatt]$ ( all sub/ances4 ,almo/ ! :ole e>?1 :e!r x be ri* loam1 b>r5 clay1 or granite b\ld]1 conta9s oxyg5 9 "s =m or o!r2 t is1 9 comb9ation ) o!r sub/ances4 ,b n[h]e1 except 9 ! air ar\nd u1 d we f9d oxyg5 free & uncomb9$ ) o!r sub/ances4 ,a less famili> b m abundant con/itu5t ( ! atmosph]e is ! nitrog54 ,almo/ f\r fif?s ( ! air ar\nd u is made up ( nitrog54 ,if ! atmosph]e 7 compos$ ( oxyg5 alone1 ! m]e/ flick] ( a mat* w\ld set ! :ole _w ablaze4 ,! fact t ! oxyg5 ( ! air is dilut$ z x 7 ) s l>ge a proportion ( nitrog51 prev5ts fires f sweep+ ov] ! _w & de/roy+ ev]y?+ 9 _! pa?4 ,nitrog5 does n support combu/ion1 & a burn+ mat* plac$ 9 a cork$ bottle goes out z soon z x has us$ up ! oxyg5 9 ! bottle4 ,! nitrog5 9 ! bottle1 n only does n assi/ ! burn+ ( ! mat*1 b x acts z a damp] to ! burn+4 ,free nitrog51 l oxyg51 is a colorless1 odorless gas4 ,x is n poison\s2 b "o w\ld die if surr\nd$ by nitrog5 alone1 j z "o w\ld die if surr\nd$ by wat]4 ,! va/ supply ( nitrog5 9 ! atmosph]e w\ld be useless if ! small] am\nt ( oxyg5 7 n pres5t to keep ! body alive4 ,nitrog5 is s important a factor 9 daily life t an entire *apt] w be devot$ to x lat]4 ,ano!r con/itu5t ( ! air ) :i* we are famili> is c>bon dioxide4 ,9 pure air1 c>bon dioxide is pres5t 9 v small proportion1 be+ cont9ually tak5 f ! air by plants 9 ! manufacture ( _! food4 ,v>i\s o!r sub/ances are pres5t 9 ! air 9 v m9ute proportions1 b ( all ! sub/ances 9 ! air1 oxyg51 nitrog51 & c>bon dioxide are ! mo/ important4 ,,*apt] ,,viii ,,g5]al ,,prop]ties ,,( ,,gases #he4 ,bicycle ,tires4 ,we "k v well t we _c put m ?an a c]ta9 am\nt ( wat] 9 a tube1 b we "k equally well t ! am\nt ( air :i* c be pump$ into a bicycle or automobile tire dep5ds l>gely ^u our muscul> en]gy4 ,a gallon ( wat] rema9s a gallon ( wat] & requires a p]fectly def9ite am\nt ( space1 b air c be compress$ & compress$1 & made to occupy less & less space4 ,:ile x is true t air is easily compress$1 x is also true t air is ela/ic & capable ( v rapid & easy expansion4 ,if a puncture occurs 9 a tire1 ! compress$ air escapes v quickly2 t is1 ! compress$ air )9 ! tube has tak5 ! fir/ opportunity (f]$ = expansion4 ,illu/ration3 ,,fig4 #ea4--;,by squeez+ ! bulb1 air is =c$ out ( ! nozzle4 ,! fact t air is ela/ic has add$ mat]ially to ! com=t ( ! _w4 ,transportation by bicycles & automobiles has be5 greatly facilitat$ by ! use ( air tires4 ,9 _m hospitals1 air mattresses are us$ 9 place ( hair1 fea!r1 or cotton mattresses1 & 9 ?is way ! b$ is kept fre%] & clean]1 & c be mov$ ) less dang] ( discom=t to ! pati5t4 ,e "t we squeeze ! bulb ( an atomiz]1 we =ce compress$ or cond5s$ air ?r\gh ! atomiz]1 & ! cond5s$ air pu%es ! liquid out ( ! nozzle 7,fig4 #ea74 ,?us we see t 9 ! necessities & conv5i5ces ( life compress$ air plays an important "p4 #hf4 ,! ,dang] ( ,compression4 ,air "u ord9>y atmosph]ic conditions ex]ts a pressure ( #ae p\nds to ! squ>e in*4 ,if1 n[1 l>ge quantities ( air are compress$ into a small space1 ! pressure ex]t$ becomes correspond+ly great]4 ,if too mu* air is bl[n into a toy balloon1 ! balloon bur/s because x _c support ! great pressure ex]t$ by ! compress$ air )94 ,:at is true ( air is true ( all gases4 ,dang]\s boil] explosions h occurr$ because ! boil] walls 7 n /rong en\gh to )/& ! pressure ( ! /eam 7:i* is wat] 9 ! =m ( gas74 ,! pressure )9 ! boil]s ( eng9es is frequ5tly sev]al hundr$ p\nds to ! squ>e in*1 & su* a pressure ne$s a /rong boil]4 #hg4 ,h[ ,pressure is ,measur$ 9 ,build+s4 ,9 ! prec$+ ,section we saw t undue pressure ( a gas may cause explosion4 ,x is important1 !re=e1 t au?orities keep /rict wat* on gases conf9$ )9 pipes & res]voirs1 nev] all[+ ! pressure to exce$ t :i* ! walls ( ! res]voir w safely be>4 ,illu/ration3 ,,fig4 #eb4--;,a pressure gauge4 ,pressure 9 a gas pipe may be measur$ by a simple in/rum5t call$ ! pressure gauge3 ,! gauge consi/s ( a b5t glass tube conta9+ m]cury1 & s made t "o end c be fitt$ to a gas jet 7,fig4 #eb74 ,:5 ! gas cock is clos$1 ! m]cury /&s at ! same level 9 bo? arms1 b :5 ! cock is op5$1 ! gas ^: pressure is be+ measur$ =ces ! m]cury up ! opposite arm4 ,if ! pressure ( ! gas is small1 ! m]cury *anges its level b v little4 ,x is cle> t ! height ( a column ( m]cury is a measure ( ! gas pressure4 ,n[ x is kn[n t "o cubic in* ( m]cury weighs ab\t half a p\nd4 ,h5ce a column ( m]cury "o in* high indicates a pressure ( ab\t "o half p\nd to ! squ>e in*2 a column two in*es high indicates a pressure ( ab\t "o p\nd to ! squ>e in*1 & s on4 ,?is is a v conv5i5t way to measure ! pressure ( ! illum9at+ gas 9 our homes & (fices4 ,! gauge is atta*$ to ! gas burn] & ! pressure is read by means ( a scale atta*$ to ! gauge4 7,see ,laboratory ,manual47 ,9 ord] to h satisfactory illum9ation1 ! pressure mu/ be /rong en\gh to give a /eady1 broad flame4 ,if ! flame f any gas jet is flick]+ & weak1 x is usually an indication ( insuffici5t pressure & ! gas company %\ld inve/igate conditions & see to x t ! consum] receives 8 prop] value4 #hg4 ,! ,gas ,met]4 ,mo/ h\sehold]s are deeply int]e/$ 9 ! actual am\nt ( gas :i* !y consume 7gas is *>g$ = accord+ to ! numb] ( cubic feet us$71 & !re=e !y %\ld be able to read ! gas met] :i* indicates _! consumption ( gas4 ,su* gas met]s are furni%$ by ! companies1 & c be read easily4 ,illu/ration3 ,,fig4 #ec4--,! gas met] indicates ! numb] ( cubic feet ( gas consum$4 ,! in/rum5t itself is some:at complex4 ,x w suffice to say t )9 ! met] box are ?9 disks :i* are mov$ by ! /ream ( gas t passes !m4 ,?is movem5t ( ! disks is record$ by clockwork devices on a dial face4 ,9 ?is way1 ! numb] ( cubic feet ( gas :i* pass ?r\gh ! met] is automatically regi/]$4 #hi4 ,! ,relation betwe5 ,pressure & ,volume4 ,x 0 long kn[n t z ! pressure ( a gas increases1 t is1 z x becomes compress$1 its volume decreases1 b ,rob]t ,boyle 0 ! fir/ to det]m9e ! exact relation betwe5 ! volume & ! pressure ( a gas4 ,he did ?is 9 a v simple mann]4 ,p\r m]cury into a ,u-%ap$ tube until ! level ( ! m]cury 9 ! clos$ end ( ! tube is ! same z ! level 9 ! op5 end4 ,! air 9 ! long arm is press+ ^u ! m]cury 9 t arm1 & is t5d+ to =ce x up ! %ort arm4 ,! air 9 ! %ort clos$ arm is press+ d[n ^u ! m]cury 9 t arm & t5d+ to s5d x up ! long arm4 ,s9ce ! m]cury is at ! same level 9 ! two arms1 ! pressure 9 ! long arm mu/ be equal to ! pressure 9 ! %ort arm4 ,b ! long arm is op51 & ! pressure 9 t arm is ! pressure ( ! atmosph]e4 ,!re=e ! pressure 9 ! %ort arm mu/ be "o atmosph]e4 ,measure ! di/ance bc betwe5 ! top ( ! m]cury & ! clos$ end ( ! tube4 ,illu/ration3 ,,figs4 #ed1 #ee4--;,z ! pressure on ! gas increases1 its volume decreases4 ,p\r m m]cury into ! op5 end ( ! tube1 & z ! m]cury rises high] & high] 9 ! long arm1 note c>efully ! decrease 9 ! volume ( ! air 9 ! %ort arm4 ,p\r m]cury into ! tube until ! diff]5ce 9 level bd is j equal to ! b>ometric height1 approximately #cb in*es4 ,! pressure ( ! air 9 ! clos$ end n[ supports ! pressure ( "o atmosph]e1 & 9 addition1 a column ( m]cury equal to ano!r atmosph]e4 ,if n[ ! air column 9 ! clos$ end is measur$1 its volume w be only "o half ( its =m] volume4 ,by d\bl+ ! pressure we h r$uc$ ! volume "o half4 ,simil>ly1 if ! pressure is increas$ ?reefold1 ! volume w be r$uc$ to "o ?ird ( ! orig9al volume4 #ij4 ,heat due to ,compression4 ,we saw 9 ,section #hi t :5ev] ! pressure ex]t$ ^u a gas is increas$1 ! volume ( ! gas is decreas$2 & t :5ev] ! pressure ^u a gas is decreas$1 ! volume ( ! gas is increas$4 ,if ! pressure is *ang$ v sl[ly1 ! *ange 9 ! temp]ature ( ! gas is imp]ceptible2 if1 h[ev]1 ! pressure is remov$ sudd5ly1 ! temp]ature falls rapidly1 or if ! pressure is appli$ sudd5ly1 ! temp]ature rises rapidly4 ,:5 bicycle tires are be+ inflat$1 ! pump becomes hot because ( ! compression ( ! air4 ,! am\nt ( heat result+ f compression is surpris+ly l>ge2 = example1 if a mass ( gas at #j ,c4 is sudd5ly compress$ to "o half its orig9al volume1 its temp]ature rises #hg ,c4 #ia4 ,cool+ by ,expansion4 ,if a gas exp&s sudd5ly1 its temp]ature falls2 = example1 if a mass ( gas at #hg ,c4 is all[$ to exp& rapidly to twice its orig9al volume1 its temp]ature falls to #j ,c4 ,if ! compress$ air ( a bicycle tire is all[$ to exp& & a s5sitive !rmomet] is held 9 ! pa? ( ! escap+ air1 ! !rmomet] w %[ a decid$ drop 9 temp]ature4 ,! l[ temp]ature obta9$ by ! expansion ( air or o!r gases is utiliz$ comm]cially on a l>ge scale4 ,by means ( p[]ful pi/ons air is compress$ to "o ?ird or "o f\r? its orig9al volume1 is pass$ ?r\gh a coil ( pipe surr\nd$ ) cold wat]1 & is !n all[$ to escape into l>ge refrig]at+ vaults1 :i* !reby h _! temp]atures noticeably l[]$1 & c be us$ = ! p]man5t /orage ( meats1 fruits1 & o!r p]i%able mat]ial4 ,9 summ]1 :5 ! atmosph]ic temp]ature is high1 ! /orage & pres]vation ( foods is ( vital importance to factories & cold /orage h\ses1 & b = ! l[ temp]ature obta9able by ! expansion ( compress$ gases1 mu* ( our food supply w\ld be lo/ to use4 #ib4 ,unexpect$ ,trans=mations4 ,if ! pressure on a gas is greatly increas$1 a sudd5 trans=mation sometimes occurs & ! gas becomes a liquid4 ,!n1 if ! pressure is r$uc$1 a second trans=mation occurs1 & ! liquid evaporates or returns to its orig9al =m z a gas4 ,9 ,section #bc we saw t a fall ( temp]ature caus$ wat] vapor to cond5se or liquefy4 ,if temp]ature alone 7 consid]$1 mo/ gases c\ld n be liquefi$1 because ! temp]ature at :i* ! av]age gas liquefies is s l[ z to be out ( ! range ( possibility2 x has be5 calculat$1 = example1 t a temp]ature ( #beb ,c4 bel[ z]o w\ld h to be obta9$ 9 ord] to liquefy hydrog54 ,"s gases c be easily trans=m$ into liquids by pressure alone1 "s gases c be easily trans=m$ into liquids by cool+ alone2 on ! o!r h&1 _m gases are s difficult to liquefy t bo? pressure & l[ temp]ature are ne$$ to produce ! desir$ result4 ,if a gas is cool$ & compress$ at ! same "t1 liquefaction occurs mu* m surely & easily ?an ?\gh ei!r factor alone 7 dep5d$ ^u4 ,! air :i* surr\nds u1 & ( ^: exi/5ce we are sc>cely aw>e1 c be r$uc$ to ! =m ( a liquid1 b ! pressure ex]t$ ^u ! portion to be liquefi$ mu/ be ?irty-n9e times z great z ! atmosph]ic pressure1 & ! temp]ature mu/ h be5 r$uc$ to a v l[ po9t4 #ic4 ,artificial ,ice4 ,ammonia gas is liquefi$ by /rong pressure & l[ temp]ature & is !n all[$ to fl[ into pipes :i* run ?r\gh tanks conta9+ salt wat]4 ,! r$uction ( pressure causes ! liquid to evaporate or turn to a gas1 & ! fall ( temp]ature :i* always accompanies evaporation means a l[]+ ( ! temp]ature ( ! salt wat] to #af or #ah bel[ z]o4 ,b imm]s$ 9 ! salt wat] are molds conta9+ pure wat]1 & s9ce ! freez+ po9t ( wat] is #j ,c1 ! wat] 9 ! molds freezes & c be drawn f ! mold z solid cakes ( ice4 ,illu/ration3 ,,fig4 #ef4--;,app>atus = mak+ artificial ice4 ,ammonia gas is driv5 by ! pump ,c into ! coil ,d 7,fig4 #ef7 "u a pressure /rong en\gh to liquefy x1 ! heat g5]at$ by ?is compression be+ c>ri$ (f by cold wat] :i* con/antly circulates ?r\gh ,b4 ,! liquid ammonia fl[s ?r\gh ! regulat+ valve ,v into ! coil ,e1 9 :i* ! pressure is kept l[ by ! pump ,c4 ,! accompany+ expansion r$uces ! temp]ature to a v l[ degree1 & ! br9e :i* circulates ar\nd ! coil ,e acquires a temp]ature bel[ ! freez+ po9t ( pure wat]4 ,! cold br9e passes f ,a to a tank 9 :i* are imm]s$ cans fill$ ) wat]1 & )9 a %ort "t ! wat] 9 ! cans is froz5 into solid cakes ( ice4 ,,*apt] ,,ix ,,invisible ,,objects #id4 ,v ,small ,objects4 ,we saw 9 ,section #hd t gases h a t5d5cy to exp&1 b t !y c be compress$ by ! application ( =ce4 ,?is obs]vation has l$ sci5ti/s to suppose t sub/ances are compos$ ( v m9ute p>ticles call$ molecules1 sep>at$ by small spaces call$ pores2 & t :5 a gas is cond5s$1 ! pores become small]1 & t :5 a gas exp&s1 ! pores become l>g]4 ,! fact t c]ta9 sub/ances are soluble1 l sug> 9 wat]1 %[s t ! molecules ( sug> f9d a lodg+ place 9 ! spaces or pores betwe5 ! molecules ( wat]1 9 mu* ! same way t pebbles f9d lodgm5t 9 ! *9ks ( ! coal 9 a coal scuttle4 ,an indef9ite quantity ( sug> _c be dissolv$ 9 a giv5 quantity ( liquid1 because aft] a c]ta9 am\nt ( sug> has be5 dissolv$ all ! pores become fill$1 & !re is no available molecul> space4 ,! rema9d] ( ! sug> settles at ! bottom ( ! vessel1 & _c be dissolv$ by any am\nt ( /irr+4 ,if a piece ( potassium p]manganate ab\t ! size ( a gra9 ( s& is put into a qu>t ( wat]1 ! solid disappe>s & ! wat] becomes a deep ri* r$4 ,! solid evid5tly has dissolv$ & has brok5 up into m9ute p>ticles :i* are too small to be se51 b :i* h scatt]$ !mselves & lodg$ 9 ! pores ( ! wat]1 ?us giv+ ! wat] its ri* color4 ,!re is no visible pro( ( ! exi/5ce ( molecules & molecul> spaces1 because n only are our eyes unable to see !m directly1 b ev5 ! mo/ p[]ful microscope _c make !m visible to u4 ,!y are s small t if "o ?\s& ( !m 7 laid side by side1 !y w\ld make a speck too small to be se5 by ! eye & too small to be visible "u ! mo/ p[]ful microscope4 ,we _c see molecules or molecul> pores1 b ! ph5om5a ( compression & expansion1 solubility & o!r equally conv9c+ facts1 h l$ u to conclude t all sub/ances are compos$ ( v m9ute p>ticles or molecules sep>at$ by spaces call$ pores4 #ie4 ,j\rneys ,made by ,molecules4 ,if a gas jet is turn$ on & n light$1 an odor ( gas soon becomes p]ceptible1 n only ?r\gh\t ! room1 b 9 adjac5t halls & ev5 9 di/ant rooms4 ,an uncork$ bottle ( cologne sc5ts an entire room1 ! odor ( a rose or violet p]meates ! atmosph]e ne> & f>4 ,^! simple ev]yday occurr5ces seem to %[ t ! molecules ( a gas mu/ be 9 a /ate ( cont9ual & rapid motion4 ,9 ! case ( ! cologne1 "s molecules mu/ h escap$ f ! liquid by ! process ( evaporation & travel$ ?r\gh ! air to ! nose4 ,we "k t ! molecules ( a liquid are 9 motion & are cont9ually pass+ into ! air because 9 "t ! vessel becomes empty4 ,! only way 9 :i* ?is c\ld happ5 w\ld be = ! molecules ( ! liquid to pass f ! liquid into ! surr\nd+ m$ium2 b ?is is really say+ t ! molecules are 9 motion4 ,f ^! ph5om5a & o!rs x is reasonably cle> t sub/ances are compos$ ( molecules1 & t molecules are n in]t1 quiet p>ticles1 b t !y are 9 incessant motion1 mov+ rapidly hi!r & ?i!r1 sometimes travel+ f>1 sometimes ne>4 ,ev5 ! log ( wood :i* lies heavy & motionless on our woodpile is made up ( c\ntless billions ( molecules ea* 9 rapid incessant motion4 ,! molecules ( solid bodies _c escape s readily z ^? ( liquids & gases1 & d n travel f>4 ,! log lies ye> aft] ye> 9 an app>5tly motionless condition1 b if "o's eyes 7 ke5 en\gh1 ! molecules w\ld be se5 mov+ among !mselves1 ev5 ?\gh !y _c escape into ! surr\nd+ m$ium & make long j\rneys z d ! molecules ( liquids & gases4 #if4 ,! ,companions ( ,molecules4 ,common s5se tells u t a molecule ( wat] is n ! same z a molecule ( v9eg>2 ! molecules ( ea* are extremely small & 9 rapid motion1 b !y diff] ess5tially1 o!rwise "o sub/ance w\ld be l e o!r sub/ance4 ,:at is x t makes a molecule ( wat] diff] f a molecule ( v9eg>1 & ea* diff] f all o!r molecules8 ,/range to say1 a molecule is n a simple object1 b is q complex1 be+ compos$ ( "o or m small] p>ticles1 call$ atoms1 & ! numb] & k9d ( atoms 9 a molecule det]m9e ! type ( ! molecule1 & ! type ( ! molecule det]m9es ! sub/ance4 ,= example1 a glass ( wat] is compos$ ( untold millions ( molecules1 & ea* molecule is a company ( ?ree /ill small] p>ticles1 "o ( :i* is call$ ! oxyg5 atom & two ( :i* are alike 9 e p>ticul> & are call$ hydrog5 atoms4 #ig4 ,simple ,molecules4 ,g5]ally molecules are compos$ ( atoms :i* are diff]5t 9 k9d4 ,= example1 ! molecule ( wat] has two diff]5t atoms1 ! oxyg5 atom & ! hydrog5 atoms2 alcohol has ?ree diff]5t k9ds ( atoms1 oxyg51 hydrog51 & c>bon4 ,sometimes1 h[ev]1 molecules are compos$ ( a gr\p ( atoms all ( :i* are alike4 ,n[ !re are b sev5ty or eighty diff]5t k9ds ( atoms1 & h5ce !re c be b sev5ty or eighty diff]5t sub/ances ^: molecules are compos$ ( atoms :i* are alike4 ,:5 ! atoms compris+ a molecule are all alike1 ! sub/ance is call$ an elem5t1 & is said to be a simple sub/ance4 ,?r\gh\t ! l5g? & bread? ( ?is va/ _w ( ours !re are only ab\t eighty kn[n elem5ts4 ,an elem5t is ! simple/ sub/ance conceivable1 because x has n be5 sep>at$ into any?+ simpl]4 ,wat] is a comp\nd sub/ance4 ,x c be sep>at$ into oxyg5 & hydrog54 ,gold1 silv]1 & lead are examples ( elem5ts1 & wat]1 alcohol1 cid]1 s&1 & m>ble are complex sub/ances1 or comp\nds1 z we are apt to call !m4 ,ev]y?+1 no matt] :at its size or %ape or "*1 is =m$ f ! v>i\s comb9ations into molecules ( a few simple atoms1 ( :i* !re exi/ ab\t eighty kn[n diff]5t k9ds4 ,b few ( ! eighty kn[n elem5ts play an important "p 9 our ev]yday life4 ,! elem5ts 9 :i* we are mo/ int]e/$ are giv5 9 ! foll[+ table1 & ! symbols by :i* !y are kn[n are plac$ 9 columns to ! "r3 ,oxyg5 ,o ,copp] ,cu ,phosphorus ,p ,hydrog5 ,h ,iod9e ,i ,potassium ,k ,c>bon ,c ,iron ,fe ,silv] ,ag ,alum9ium ,al ,lead ,pb ,sodium ,na ,calcium ,ca ,nickel ,ni ,sulphur ,s ,*lor9e ,cl ,nitrog5 ,n ,t9 ,sn ,we h se5 9 an e>li] exp]im5t t twice z mu* hydrog5 z oxyg5 c be obta9$ f wat]4 ,two atoms ( ! elem5t hydrog5 unite ) "o atom ( ! elem5t oxyg5 to make "o molecule ( wat]4 ,9 symbols we express ?is ,h#b,o4 ,a gr\p ( symbols1 su* z ?is1 express+ a molecule ( a comp\nd is call$ a =mula4 ,na,cl is ! =mula = sodium *loride1 :i* is ! *emical "n ( common salt4 ,,*apt] ,x ,,light #ih4 ,:at ,light ,does = ,u4 ,heat keeps u w>m1 cooks our food1 drives our eng9es1 & 9 a ?\s& ways makes life com=table & pleasant1 b :at %\ld we d )\t light8 ,h[ _m ( u c\ld be happy ev5 ?\gh w>m & well f$ if we 7 =c$ to live 9 ! d>k :]e ! sunbeams nev] flick]$1 :]e ! %ad[s nev] /ole across ! floor1 & :]e ! s(t twilight c\ld n tell u t ! day 0 done8 ,heat & light are ! two mo/ important physical factors 9 life2 we _c say :i* is ! m necess>y1 because 9 ! extreme cold or arctic regions man _c live1 & 9 ! d>k places :]e ! light nev] p5etrates man sick5s & dies4 ,bo? heat & light are ess5tial to life1 & ea* has its own "p to play 9 ! v>i$ exi/5ce ( man & plant & animal4 ,light enables u to see ! _w ar\nd u1 makes ! beautiful colors ( ! trees & fl[]s1 enables u to read1 is ess5tial to ! tak+ ( photographs1 gives u our mov+ pictures & our magic lant]ns1 produces ! exquisite t9ts ( /a9$-glass w9d[s1 & br+s u ! joy ( ! ra9b[4 ,we d n always realize t light is b5eficial1 because sometimes x fades our clo?+ & our c>pets1 & burns our sk9 & makes x sore4 ,b we %all see t ev5 ^! app>5tly h>mful effects ( light are 9 reality ( great value 9 man's con/ant battle aga9/ disease4 #ii4 ,! ,c&le4 ,natural heat & light are furni%$ by ! sun1 b ! abs5ce ( ! sun dur+ ! ev5+ makes artificial light necess>y1 & ev5 dur+ ! day artificial light is ne$$ 9 build+s ^: /ructure excludes ! natural light ( ! sun4 ,artificial light is furni%$ by electricity1 by gas1 by oil 9 lamps1 & 9 num]\s o!r ways4 ,until mod]n times c&les 7 ! ma9 s\rce ( light1 & inde$ to-day ! int5sity1 or p[]1 ( any light is measur$ 9 c&le p[] units1 j z l5g? is measur$ 9 y>ds2 = example1 an av]age gas jet gives a #aj c&le p[] light1 or is t5 times z bright z a c&le2 an ord9>y inc&esc5t electric light gives a #af c&le p[] light1 or furni%es sixte5 times z mu* light z a c&le4 ,v /rong l>ge oil lamps c at times yield a light ( #fj c&le p[]1 :ile ! l>ge arc lamps :i* fla% out on ! /reet corn]s are said to furni% #abjj times z mu* light z a s+le c&le4 ,naturally all c&les d n give ! same am\nt ( light1 nor are all c&les alike 9 size4 ,! c&les :i* decorate our tea tables are ( wax1 :ile ^? :i* s]ve = g5]al use are ( p>aff9 & tall[4 ,illu/ration3 ,,fig4 #eg4--;,a photograph at a receives f\r times z mu* light z :5 held at b4 #ajj4 ,fad+ ,illum9ation4 ,! f>!r we move f a light1 ! less /rong1 or int5se1 is ! illum9ation :i* rea*es u2 ! light ( ! /reet lamp on ! corn] fades & becomes dim be=e ! middle ( ! block is rea*$1 s t we look eag]ly = ! next lamp4 ,! light dim9i%es 9 brightness mu* m rapidly ?an we realize1 z ! foll[+ simple exp]im5t w %[4 ,let a s+le c&le 7,fig4 #eg7 s]ve z our light1 & at a di/ance ( "o foot f ! c&le place a photograph4 ,9 ?is position ! photograph receives a def9ite am\nt ( light f ! c&le & has a c]ta9 brightness4 ,if n[ we place a simil> photograph directly beh9d ! fir/ photograph & at a di/ance ( two feet f ! c&le1 ! second photograph receives no light because ! fir/ "o cuts (f all ! light4 ,if1 h[ev]1 ! fir/ photograph is remov$1 ! light :i* fell on x passes outw>d & spreads itself ov] a l>g] area1 until at ! di/ance ( ! second photograph ! light spreads itself ov] f\r times z l>ge an area z =m]ly4 ,at ?is di/ance1 !n1 ! illum9ation on ! second photograph is only "o f\r? z /rong z x 0 on a simil> photograph held at a di/ance ( "o foot f ! c&le4 ,! photograph or object plac$ at a di/ance ( "o foot f a light is well illum9at$2 if x is plac$ at a di/ance ( two feet1 ! illum9ation is only "o f\r? z /rong1 & if ! object is plac$ ?ree feet away1 ! illum9ation is only "o n9? z /rong4 ,?is fact %\ld make u h ?\ght & c>e 9 ! use ( our eyes4 ,we ?9k we are sixte5 times z well (f ) our inc&esc5t lights z our ance/ors 7 ) simple c&les1 b we mu/ reflect t our ance/ors kept ! c&le ne> !m1 at _! elb[1 s to speak1 :ile we sit at "s di/ance f ! light & unconc]n$ly read & sew4 ,z an object rec$es f a light ! illum9ation :i* x receives dim9i%es rapidly1 = ! /r5g? ( ! illum9ation is inv]sely proportional to ! squ>e ( di/ance ( ! object f ! light4 ,our ance/ors ) a c&le at a di/ance ( "o foot f a book 7 z well (f z we are ) an inc&esc5t light f\r feet away4 #aja4 ,money ,value ( ,light4 ,light is b\ght & sold almo/ z readily z are ! products ( f>m & dairy2 _m factories1 *ur*es1 & ap>tm5ts pay a def9ite sum = electric light ( a /&>d /r5g?1 & naturally full value is desir$4 ,an in/rum5t = measur+ ! /r5g? ( a light is call$ a photomet]1 & !re are _m diff]5t v>ieties1 j z !re are v>ieties ( scales :i* measure h\sehold articles4 ,"o light-measur+ scale dep5ds ^u ! law t ! int5sity ( illum9ation decreases ) ! squ>e ( ! di/ance ( ! object f ! light4 ,suppose we wi% to measure ! /r5g? ( ! electric light bulbs 9 our homes1 9 ord] to see :e!r we are gett+ ! specifi$ illum9ation4 ,9 front ( a scre5 place a black rod 7,fig4 #eh7 :i* is illum9at$ by two diff]5t lights2 namely1 a /&>d c&le & an inc&esc5t bulb ^: /r5g? is to be measur$4 ,two %ad[s ( ! rod w fall on ! scre51 "o caus$ by ! c&le & ! o!r caus$ by ! inc&esc5t light4 ,! %ad[ due to ! latt] s\rce is n s d>k z t due to ! c&le4 ,n[ let ! inc&esc5t light be mov$ away f ! scre5 until ! two %ad[s are ( equal d>kness4 ,if ! inc&esc5t light is f\r times z f> away f ! scre5 z ! c&le1 & ! %ad[s are equal1 we "k1 by ,section #ajj1 t its /r5g? is sixte5 c&le p[]4 ,if ! inc&esc5t light is f\r times z f> away f ! scre5 z ! c&le is1 its p[] mu/ be sixte5 times z great1 & we "k ! company is furni%+ ! /&>d am\nt ( light = a sixte5 c&le p[] electric bulb4 ,if1 h[ev]1 ! bulb mu/ be mov$ ne>] to ! rod 9 ord] t ! two %ad[s may be simil> !n ! light giv5 by ! bulb is less ?an sixte5 c&le p[]1 & less ?an t due ! consum]4 ,illu/ration3 ,,fig4 #eh4--,! two %ad[s are equally d>k4 #ajb4 ,h[ ,light ,travels4 ,we nev] expect to see ar\nd a corn]1 & if we wi% to see ?r\gh p9holes 9 ?ree sep>ate pieces ( c>dbo>d1 we place ! c>dbo>ds s t ! ?ree holes are 9 a /raight l9e4 ,:5 sunlight ent]s a d>k room ?r\gh a small op5+1 ! du/ p>ticles danc+ 9 ! sun %[ a /raight ray4 ,if a hole is made 9 a c>d1 & ! c>d is held 9 front ( a light1 ! c>d ca/s a %ad[1 9 ! c5t] ( :i* is a bright spot4 ,! light1 ! hole1 & ! bright spot are all 9 ! same /raight l9e4 ,^! simple obs]vations lead u to ?9k t light travels 9 a /raight l9e4 ,illu/ration3 ,,fig4 #ei4--,! c&le _c be se5 unless ! ?ree p9holes are 9 a /rait l9e4 ,we c always tell ! direction f :i* light comes1 ei!r by ! %ad[ ca/ or by ! bright spot =m$ :5 an op5+ occurs 9 ! opaque object ca/+ ! %ad[4 ,if ! %ad[ ( a tree falls t[>ds ! we/1 we "k ! sun mu/ be 9 ! ca/2 if a bright spot is on ! floor1 we c easily locate ! light ^: rays /ream ?r\gh an op5+ & =m ! bright spot4 ,we "k t light travels 9 a /raight l9e1 & foll[+ ! pa? ( ! beam :i* comes to our eyes1 we are sure to locate ! light4 #ajc4 ,good & ,bad ,mirrors4 ,z we walk along ! /reet1 we frequ5tly see ourselves reflect$ 9 ! %op w9d[s1 9 poli%$ metal signbo>ds1 9 ! metal trimm+s ( wagons & automobiles2 b 9 mirrors we get ! be/ image ( ourselves4 ,we res5t ! image giv5 by a piece ( t91 because ! reflection is di/ort$ & does n picture u z we really are2 a r\gh surface does n give a fair repres5tation2 if we want a true image ( ourselves1 we mu/ use a smoo? surface l a mirror z a reflector4 ,if ! wat] 9 a pond is absolutely /ill1 we get a cle>1 true image ( ! trees1 b if !re are ripples on ! surface1 ! reflection is blurr$ & di/ort$4 ,a metal ro( reflects s mu* light t ! eyes are dazzl$ by x1 & a :itewa%$ f5ce injures ! eyes because ( ! gl>e :i* comes f ! reflect$ light4 ,nei!r ( ^! c\ld be call$ mirrors1 h[ev]1 because al?\gh !y reflect light1 !y reflect x s irregul>ly t n ev5 a sugge/ion ( an image c be obta9$4 ,mo/ ( u are suffici5tly famili> ) mirrors to "k t ! image is a duplicate ( ourselves ) reg>d to size1 %ape1 color1 & expression1 b t x appe>s to be back ( ! mirror1 :ile we are actually 9 front ( ! mirror4 ,! image appe>s n only beh9d ! mirror1 b x is also exactly z f> back ( ! mirror z we are 9 front ( x2 if we approa* ! mirror1 ! image also draws ne>]2 if we )draw1 x likewise rec$es4 #ajd4 ,! ,pa? ( ,light4 ,if a mirror or any o!r poli%$ surface is held 9 ! pa? ( a sunbeam1 "s ( ! light is reflect$1 & by rotat+ ! mirror ! reflect$ sunbeam may be made to take any pa?4 ,s*ool *ildr5 amuse !mselves by reflect+ sunbeams f a mirror into _! companions' faces4 ,if ! companion moves 8 head 9 ord] to avoid ! reflect$ beam1 8 torm5tor moves or incl9es ! mirror & fla%es ! beam back to 8 victim's face4 ,if a mirror is held s t a ray ( light /rikes x 9 a p]p5dicul> direction1 ! light is reflect$ backw>d along ! pa? by :i* x came4 ,if1 h[ev]1 ! light makes an angle ) ! mirror1 its direction is *ang$1 & x leaves ! mirror along a new pa?4 ,by obs]vation we le>n t :5 a beam /rikes ! mirror & makes an angle ( #cj ) ! p]p5dicul>1 ! beam is reflect$ 9 su* a way t its new pa? also makes an angle ( #cj ) ! p]p5dicul>4 ,if ! sunbeam /rikes ! mirror at an angle ( #cb ) ! p]p5dicul>1 ! pa? ( ! reflect$ ray also makes an angle ( #cb ) ! p]p5dicul>4 ,! ray 7,,ac1 ,fig4 #fj7 :i* falls ^u ! mirror is call$ ! incid5t ray1 & ! angle :i* ! incid5t ray 7,,ac7 makes ) ! p]p5dicul> 7,,bc7 to ! mirror1 at ! po9t :]e ! ray /rikes ! mirror1 is call$ ! angle ( incid5ce4 ,! angle =m$ by ! reflect$ ray 7,,cd7 & ?is same p]p5dicul> is call$ ! angle ( reflection4 ,obs]vation & exp]im5t h taught u t light is always reflect$ 9 su* a way t ! angle ( reflection equals ! angle ( incid5ce4 ,light is n ! only illu/ration we h ( ! law ( reflection4 ,e *ild :o b\nces a ball makes use ( ?is law1 b he uses x unconsci\sly4 ,if an ela/ic ball is ?r[n p]p5dicul>ly aga9/ ! floor1 x returns to ! s5d]2 if x is ?r[n aga9/ ! floor at an angle 7,fig4 #fa71 x reb\nds 9 ! opposite direction1 b always 9 su* a way t ! angle ( reflection equals ! angle ( incid5ce4 ,illu/ration3 ,,fig4 #fj4--,! ray ,,ac is reflect$ z ,,cd4 ,illu/ration3 ,,fig4 #fa4--;,a b\nc+ ball illu/rates ! law ( reflection4 #aje4 ,:y ! ,image seems to be beh9d ! ,mirror4 ,if a c&le is plac$ 9 front ( a mirror1 z 9 ,figure #fb1 "o ( ! rays ( light :i* leaves ! c&le w fall ^u ! mirror z ,,ab & w be reflect$ z ,,bc 79 su* a way t ! angle ( reflection equals ! angle ( incid5ce74 ,if an obs]v] /&s at ,c1 he w ?9k t ! po9t ,a ( ! c&le is some:]e along ! l9e ,,cb ext5d$4 ,su* a supposition w\ld be ju/ifi$ f ,section #ajb4 ,b ! c&le s5ds out light 9 all directions2 "o ray !re=e w /rike ! mirror z ,,ad & w be reflect$ z ,,de1 & an obs]v] at ,e w ?9k t ! po9t ,a ( ! c&le is some:]e along ! l9e ,,ed4 ,9 ord] t bo? obs]v]s may be correct1 t is1 9 ord] t ! light may seem to be 9 bo? ^! directions1 ! image ( ! po9t ,a mu/ seem to be at ! int]section ( ! two l9es4 ,9 a simil> mann] x c be %[n t e po9t ( ! image ( ! c&le seems to be beh9d ! mirror4 ,illu/ration3 ,,fig4 #fb4--,! image is a duplicate ( ! object1 b appe>s to be beh9d ! mirror4 ,x c be %[n by exp]im5t t ! di/ance ( ! image beh9d ! mirror is equal to ! di/ance ( ! object 9 front ( ! mirror4 #ajf4 ,:y ,objects are ,visible4 ,if ! beam ( light falls ^u a %eet ( pap]1 or ^u a photograph1 in/ead ( ^u a smoo? poli%$ surface1 no def9ite reflect$ ray w be se51 b a gl>e w be produc$ by ! scatt]+ ( ! beam ( light4 ,! surface ( ! pap] or photograph is r\gh1 & z a result1 x scatt]s ! beam 9 e direction4 ,x is h>d = u to realize t a smoo? %eet ( pap] is by no means s smoo? z x looks4 ,x is r\gh comp>$ ) a poli%$ mirror4 ,! law ( reflection always holds1 h[ev]1 no matt] :at ! reflect+ surface is1--! angle ( reflection always equals ! angle ( incid5ce4 ,9 a smoo? body ! reflect$ beams are all p>allel2 9 a r\gh body1 ! reflect$ beams are incl9$ to ea* o!r 9 all sorts ( ways1 & no two beams leave ! pap] 9 exactly ! same direction4 ,illu/ration3 ,,fig4 #fc4--,! surface ( ! pap]1 al?\gh smoo? 9 appe>ance1 is 9 reality r\gh1 & scatt]s ! light 9 e direction4 ,hot coals1 r$-hot /oves1 gas flames1 & c&les %9e by _! own light1 & are self-lum9\s4 ,objects l *airs1 tables1 c>pets1 h no light )9 !mselves & are visible only :5 !y receive light f a lum9\s s\rce & reflect t light4 ,we "k t ^! objects are n self-lum9\s1 because !y are n visible at night unless a lamp or gas is burn+4 ,:5 light f any lum9\s object falls ^u books1 desks1 or di%es1 x meets r\gh surfaces1 & h5ce und]goes diffuse reflection1 & is scatt]$ irregul>ly 9 all directions4 ,no matt] :]e ! eye is1 "s reflect$ rays ent] x1 & ! v>i\s objects are cle>ly se54 ,,*apt] ,,xi ,,refraction #ajg4 ,b5t ,rays ( ,light4 ,a /raw 9 a glass ( lemonade seems to be brok5 at ! surface ( ! liquid1 ! h&le ( a teaspoon 9 a cup ( wat] appe>s brok51 & objects se5 ?r\gh a glass ( wat] may seem di/ort$ & *ang$ 9 size4 ,:5 light passes f air into wat]1 or f any transp>5t sub/ance into ano!r ( diff]5t d5sity1 its direction is *ang$1 & x em]ges along an entirely new pa? 7,fig4 #fd74 ,we "k t light rays pass ?r\gh glass1 because we c see ?r\gh ! w9d[ panes & ?r\gh our spectacles2 we "k t light rays pass ?r\gh wat]1 because we c see ?r\gh a glass ( cle> wat]2 on ! o!r h&1 light rays _c pass ?r\gh wood1 lea!r1 metal1 etc4 ,illu/ration3 ,,fig4 #fd4--;,a /raw or /ick 9 wat] seems brok54 ,:5ev] light meets a transp>5t sub/ance obliquely1 "s ( x is reflect$1 und]go+ a *ange 9 its direction2 & "s ( x passes onw>d ?r\gh ! m$ium1 b ! latt] portion passes onw>d along a new pa?4 ,! ray ,,ro 7,fig4 #fe7 passes obliquely ?r\gh ! air to ! surface ( ! wat]1 b1 on ent]+ ! wat]1 x is b5t or refract$ & takes ! new pa? ,,os4 ,! angle ,,aor is call$ ! angle ( incid5ce4 ,! angle ,,pos is call$ ! angle ( refraction4 ,illu/ration3 ,,fig4 #fe4--,:5 ! ray ,,ro ent]s ! wat]1 its pa? *anges to ,,os4 ,! angle ( refraction is ! angle =m$ by ! refract$ ray & ! p]p5dicul> to ! surface at ! po9t :]e ! light /rikes x4 ,:5 light passes f air into wat] or glass1 ! refract$ ray is b5t t[>d ! p]p5dicul>1 s t ! angle ( refraction is small] ?an ! angle ( incid5ce4 ,:5 a ray ( light passes f wat] or glass into air1 ! refract$ ray is b5t away f ! p]p5dicul> s t ! angle ( refraction is great] ?an ! angle ( incid5ce4 ,! b5d+ or deviation ( light 9 its passage f "o sub/ance to ano!r is call$ refraction4 #ajh4 ,h[ ,refraction ,deceives u4 ,refraction is ! s\rce ( _m illusions2 b5t rays ( light make objects appe> :]e !y really are n4 ,a fi% at ,a 7,fig4 #ff7 seems to be at ,b4 ,! end ( ! /ick 9 ,figure #fd seems to be ne>] ! surface ( ! wat] ?an x really is4 ,illu/ration3 ,,fig4 #ff4--;,a fi% at ,a seems to be at ,b4 ,! light f ! sun1 moon1 & />s c rea* u only by pass+ ?r\gh ! atmosph]e1 b 9 ,section #gf1 we le>n$ t ! atmosph]e v>ies 9 d5sity f level to level2 h5ce all ! light :i* travels ?r\gh ! atmosph]e is con/antly deviat$ f its orig9al pa?1 & be=e ! light rea*es ! eye x has und]gone _m *anges 9 direction4 ,n[ we le>n$ 9 ,section #ajb1 t ! direction ( ! rays ( light z !y ent] ! eye det]m9es ! direction 9 :i* an object is se52 h5ce ! sun1 moon1 & />s seem to be along ! l9es :i* ent] ! eye1 al?\gh 9 reality !y are n4 #aji4 ,uses ( ,refraction4 ,if x 7 n = refraction1 or ! deviation ( light 9 its passage f m$ium to m$ium1 ! wond]s & beauties ( ! magic lant]n & ! cam]a w\ld be unkn[n to u2 sun1 moon1 & />s c\ld n be made to yield up _! di/ant secrets to u 9 photographs2 ! com=t & help ( spectacles w\ld be lack+1 spectacles :i* h help$ unfold to _m ! r>e beauties ( nature1 su* z a cle> view ( cl\ds & sunset1 ( humm+ bee & fly+ bird4 ,books ) _! weal? ( ent]ta9m5t & in=mation w\ld be seal$ to a l>ge "p ( mank9d1 if glasses did n assi/ weak eyes4 ,by refraction ! magnify+ glass reveals objects hidd5 because ( _! m9ut5ess1 & enl>ges = our c>eful contemplation objects o!rwise b>ely visible4 ,! wat*mak]1 unassi/$ by ! magnify+ glass1 c\ld n detect ! t9y gra9s ( du/ or s& :i* clog ! delicate :eels ( our wat*es4 ,! m]*ant1 ) 8 l5s1 exam9es ! sep>ate ?reads ( wool5 & silk fabrics to det]m9e ! /r5g? & value ( ! mat]ial4 ,! physician1 ) 8 invaluable microscope1 c\nts ! numb] ( inf9itesimal corpuscles 9 ! blood & bases 8 prescription on t c\nt2 he exam9es ! sputum ( a pati5t to det]m9e :e!r tub]culosis wa/es ! sy/em4 ,! bact]iologi/ ) ! same in/rum5t scrut9izes ! dr9k+ wat] & le>ns :e!r ! dang]\s typhoid g]ms are pres5t4 ,! future ( m$ic9e w dep5d some:at ^u ! additional secrets :i* man is able to =ce f nature ?r\gh ! use ( p[]ful l5ses1 because z l5ses h1 9 ! pa/1 be5 ! means ( reveal+ disease g]ms1 s 9 ! future m p[]ful l5ses may s]ve to br+ to light g]ms yet unkn[n4 ,h[ refraction accompli%es ^! results w be expla9$ 9 ! foll[+ ,sections4 #aaj4 ,! ,w9d[ ,pane4 ,we h se5 t light is b5t :5 x passes f "o m$ium to ano!r ( diff]5t d5sity1 & t objects view$ by refract$ light d n appe> 9 _! prop] positions4 ,:5 a ray ( light passes ?r\gh a piece ( plane glass1 su* z a w9d[ pane 7,fig4 #fg71 x is refract$ at ! po9t ,b t[>d ! p]p5dicul>1 & cont9ues its c\rse ?r\gh ! glass 9 ! new direction ,,bc4 ,on em]g+ f ! glass1 ! light is refract$ away f ! p]p5dicul> & takes ! direction ,,cd1 :i* is cle>ly p>allel to its orig9al direction4 ,h5ce1 :5 we view objects ?r\gh ! w9d[1 we see !m slightly displac$ 9 position1 b o!rwise un*ang$4 ,! deviation or displacem5t caus$ by glass z ?9 z w9d[ panes is too slight to be notic$1 & we are n consci\s t objects are out ( position4 ,illu/ration3 ,,fig4 #fg4--,objects look$ at ?r\gh a w9d[ pane seem to be 9 _! natural place4 #aaa4 ,*&eli] ,cry/als & ,prisms4 ,:5 a ray ( light passes ?r\gh plane glass1 l a w9d[ pane1 x is %ift$ some:at1 b its direction does n *ange2 t is1 ! em]g5t ray is p>allel to ! incid5t ray4 ,b :5 a beam ( light passes ?r\gh a triangul> glass prism1 su* z a *&eli] cry/al1 its direction is greatly *ang$1 & an object view$ ?r\gh a prism is se5 q out ( its true position4 ,:5ev] light passes ?r\gh a prism1 x is b5t t[>d ! base ( ! prism1 or t[>d ! ?ick portion ( ! prism1 & em]ges f ! prism 9 q a diff]5t direction f t 9 :i* x ent]$ 7,fig4 #fh74 ,h5ce1 :5 an object is look$ at ?r\gh a prism1 x is se5 q out ( place4 ,9 ,figure #fh1 ! c&le seems to be at ,s1 :ile 9 reality x is at ,a4 ,illu/ration3 ,,fig4 #fh4--,:5 look$ at ?r\gh ! prism1 ,a seems to be at ,s4 #aab4 ,l5ses4 ,if two prisms are arrang$ z 9 ,figure #fi1 & two p>allel rays ( light fall ^u ! prisms1 ! beam ,a w be b5t d[nw>d t[>d ! ?ick5$ portion ( ! prism1 & ! beam ,b w be b5t upw>d t[>d ! ?ick portion ( ! prism1 & aft] pass+ ?r\gh ! prism ! two rays w int]sect at "s po9t ,f1 call$ a focus4 ,illu/ration3 ,,fig4 #fi4--,rays ( light are conv]g$ & focus$ at ,f4 ,if two prisms are arrang$ z 9 ,figure #gj1 ! ray ,a w be refract$ upw>d t[>d ! ?ick end1 & ! ray ,b w be refract$ d[nw>d t[>d ! ?ick end2 ! two rays1 on em]g+1 w !re=e be widely sep>at$ & w n int]sect4 ,illu/ration3 ,,fig4 #gj4--,rays ( light are div]g$ & d n come to any real focus4 ,l5ses are v simil> to prisms2 inde$1 two prisms plac$ z 9 ,figure #fi1 & r\nd$ (f1 w\ld make a v good convex l5s4 ,a l5s is any transp>5t mat]ial1 b usually glass1 ) "o or bo? sides curv$4 ,! v>i\s types ( l5ses are %[n 9 ,figure #ga4 ,illu/ration3 ,,fig4 #ga4--,! diff]5t types ( l5ses4 ,! fir/ ?ree types focus p>allel rays at "s common po9t ,f1 z 9 ,figure #fi4 ,su* l5ses are call$ convex or conv]g+ l5ses4 ,! la/ ?ree types1 call$ concave l5ses1 scatt] p>allel rays s t !y d n come to a focus1 b div]ge widely aft] passage ?r\gh ! l5s4 #aac4 ,! ,%ape & ,mat]ial ( a ,l5s4 ,! ma9 or pr9cipal focus ( a l5s1 t is1 ! po9t at :i* rays p>allel to ! base l9e ,,ab meet 7,fig4 #ga71 dep5ds ^u ! %ape ( ! l5s4 ,= example1 a ?ick l5s1 su* z ,a 7,fig4 #gb71 focuses ! rays v ne> to ! l5s2 ,b1 :i* is n s ?ick1 focuses ! rays at a great] di/ance f ! l5s2 & ,c1 :i* is a v ?9 l5s1 focuses ! rays at a consid]able di/ance f ! l5s4 ,! di/ance ( ! pr9cipal focus f ! l5s is call$ ! focal l5g? ( ! l5s1 & f ! diagrams we see t ! m convex ! l5s1 ! %ort] ! focal l5g?4 ,illu/ration3 ,,fig4 #gb4--,! m curv$ ! l5s1 ! %ort] ! focal l5g?1 & ! ne>] ! focus is to ! l5s4 ,! position ( ! pr9cipal focus dep5ds n only on ! %ape ( ! l5s1 b also on ! refractive p[] ( ! mat]ial compos+ ! l5s4 ,a l5s made ( ice w\ld n deviate ! rays ( light s mu* z a l5s ( simil> %ape compos$ ( glass4 ,! great] ! refractive p[] ( ! l5s1 ! great] ! b5d+1 & ! ne>] ! pr9cipal focus to ! l5s4 ,!re are _m diff]5t k9ds ( glass1 & ea* k9d ( glass refracts ! light diff]5tly4 ,fl9t glass conta9s lead2 ! lead makes ! glass d5se1 & gives x great refractive p[]1 enabl+ x to b5d & sep>ate light 9 all directions4 ,cut glass & toilet articles are made ( fl9t glass because ( ! brilliant effects caus$ by its great refractive p[]1 & imitation gems are commonly no?+ m ?an poli%$ fl9t glass4 #aad4 ,h[ ,l5ses ,=m ,images4 ,suppose we place an arr[1 ,a1 9 front ( a convex l5s 7,fig4 #gc74 ,! ray ,,ac1 p>allel to ! pr9cipal axis1 w pass ?r\gh ! l5s & em]ge z ,,de4 ,! ray is always b5t t[>d ! ?ick portion ( ! l5s1 bo? at its entrance into ! l5s & its em]g5ce f ! l5s4 ,illu/ration3 ,,fig4 #gc4--,! image is l>g] ?an ! object4 ,by means ( a l5s1 a wat*mak] gets an enl>g$ image ( ! du/ :i* clogs ! :eels ( 8 wat*4 ,9 ,section #aje1 we saw t two rays det]m9e ! position ( any po9t ( our image2 h5ce 9 ord] to locate ! image ( ! top ( ! arr[1 we ne$ to consid] b "o m ray f ! top ( ! object4 ,! mo/ conv5i5t ray to *oose w\ld be "o pass+ ?r\gh ,o1 ! optical c5t] ( ! l5s1 because su* a ray passes ?r\gh ! l5s un*ang$ 9 direction1 z is cle> f ,figure #gd4 ,! po9t :]e ,,ac & ,,ao meet aft] refraction w be ! position ( ! top ( ! arr[4 ,simil>ly x c be %[n t ! c5t] ( ! arr[ w be at ! po9t ,t1 & we see t ! image is l>g] ?an ! object4 ,?is c be easily prov$ exp]im5tally4 ,let a convex l5s be plac$ ne> a c&le 7,fig4 #ge72 move a pap] scre5 back & =? beh9d ! l5s2 = "s position ( ! scre5 a cle>1 enl>g$ image ( ! c&le w be made4 ,illu/ration3 ,,fig4 #gd4--,rays above ,o are b5t d[nw>d1 ^? bel[ ,o are b5t upw>d1 & rays ?r\gh ,o em]ge f ! l5s un*ang$ 9 direction4 ,if ! c&le or arr[ is plac$ 9 a new position1 say at ,,ma 7,fig4 #gf71 ! image =m$ is small] ?an ! object1 & is ne>] to ! l5s ?an x 0 be=e4 ,move ! l5s s t its di/ance f ! c&le is increas$1 & !n f9d ! image on a piece ( pap]4 ,! size & position ( ! image dep5d ^u ! di/ance ( ! object f ! l5s 7,fig4 #gg74 ,by means ( a l5s "o c easily get on a visit+ c>d a picture ( a di/ant *ur* /eeple4 ,illu/ration3 ,,fig4 #ge4--,! l5s is held 9 su* a position t ! image ( ! c&le is l>g] ?an ! object4 ,illu/ration3 ,,fig4 #gf4--,! image is small] ?an ! object4 #aae4 ,! ,value ( ,l5ses4 ,if x 7 n = ! fact t a l5s c be held at su* a di/ance f an object z to make ! image l>g] ?an ! object1 x w\ld be impossible = ! l5s to assi/ ! wat*mak] 9 locat+ ! small p>ticles ( du/ :i* clog ! :eels ( ! wat*4 ,if x 7 n = ! opposite fact--t a l5s c be held at su* a di/ance f ! object z to make an image small] ?an ! object1 x w\ld be impossible to h a photograph ( a tall tree or build+ unless ! photograph 7 z l>ge z ! tree itself4 ,:5 a photograph] takes a photograph ( a p]son or a tree1 he moves 8 cam]a until ! image =m$ by ! l5s is ( ! desir$ size4 ,by br++ ! cam]a 7really ! l5s ( ! cam]a7 ne>1 we obta9 a l>ge-siz$ photograph2 by increas+ ! di/ance betwe5 ! cam]a & ! object1 a small] photograph is obta9$4 ,! m\nta9 top may be s f> di/ant t 9 ! photograph x w n appe> to be great] ?an a small /one4 ,illu/ration3 ,,fig4 #gg4--,! l5s is plac$ 9 su* a position t ! image is ab\t ! same size z ! object4 ,_m famili> illu/rations ( l5ses1 or curv$ refract+ surfaces1 & _! "w1 are kn[n to all ( u4 ,fi% globes magnify ! fi% t swim )94 ,bottles c be s %ap$ t !y make ! olives1 pickles1 & pea*es t !y conta9 appe> l>g] ?an !y really are4 ,! fruit 9 bottles frequ5tly seems too l>ge to h gone ?r\gh ! neck ( ! bottle4 ,! deception is due to refraction1 & ! mat]ial & %ape ( ! bottle furni% a suffici5t explanation4 ,by us+ comb9ations ( two or m l5ses ( v>i\s k9ds1 x is possible to h an image ( almo/ any desir$ size1 & 9 practically any desir$ position4 #aaf4 ,! ,human ,eye4 ,9 ,section #aad1 we obta9$ on a movable scre51 by means ( a simple l5s1 an image ( a c&le4 ,! human eye possesses a mo/ wond]ful l5s & scre5 7,fig4 #gh72 ! l5s is call$ ! cry/all9e l5s1 & ! scre5 is call$ ! ret9a4 ,rays ( light pass f ! object ?r\gh ! pupil ,p1 g ?r\gh ! cry/all9e l5s ,l1 :]e !y are refract$1 & !n pass onw>d to ! ret9a ,r1 :]e !y =m a di/9ct image ( ! object4 ,illu/ration3 ,,fig4 #gh4--,! eye4 ,we le>n$ 9 ,section #aad t a *ange 9 ! position ( ! object necessitat$ a *ange 9 ! position ( ! scre51 & t e "t ! object 0 mov$ ! position ( ! scre5 _h to be alt]$ be=e a cle> image ( ! object c\ld be obta9$4 ,! ret9a ( ! eye _c be mov$ backw>d & =w>d1 z ! scre5 01 & ! cry/all9e l5s is p]man5tly locat$ directly back ( ! iris4 ,h[1 !n1 does x happ5 t we c see cle>ly bo? ne> & di/ant objects2 t ! pr9t$ page :i* is held 9 ! h& is visible at "o second1 & t ! *ur* spire on ! di/ant horizon is visible ! in/ant ! eyes are rais$ f ! book8 ,h[ is x possible to obta9 on an immovable scre5 by means ( a simple l5s two di/9ct images ( objects at widely v>y+ di/ances8 ,! answ] to ^! que/ions is t ! cry/all9e l5s *anges %ape accord+ to ne$4 ,! l5s is atta*$ to ! eye by means ( small muscles1 m1 & x is by ! action ( ^! muscles t ! l5s is able to become small & ?ick1 or l>ge & ?92 t is1 to become m or less curv$4 ,:5 we look at ne> objects1 ! muscles act 9 su* a way t ! l5s bulges out1 & becomes ?ick 9 ! middle & ( ! "r curvature to focus ! ne> object ^u ! scre54 ,:5 we look at an object sev]al hundr$ feet away1 ! muscles *ange _! pull on ! l5s & flatt5 x until x is ( ! prop] curvature = ! new di/ance4 ,! adju/m5t ( ! muscles is s quick & unconsci\s t we normally d n exp]i5ce any difficulty 9 *ang+ our range ( view4 ,! ability ( ! eye to adju/ itself to v>y+ di/ances is call$ accommodation4 ,! p[] ( adju/m5t 9 g5]al decreases ) age4 #aag4 ,f>sight$ness & ,ne>sight$ness4 ,a f>sight$ p]son is "o :o _c see ne> objects s di/9ctly z f> objects1 & :o 9 _m cases _c see ne> objects at all4 ,! eyeball ( a f>sight$ p]son is v %ort1 & ! ret9a is too close to ! cry/all9e l5s4 ,ne> objects are br\ght to a focus beh9d ! ret9a in/ead ( on x1 & h5ce are n visible4 ,ev5 ?\gh ! muscles ( accommodation d _! be/ to bulge & ?ick5 ! l5s1 ! rays ( light are n b5t suffici5tly to focus %>ply on ! ret9a4 ,9 consequ5ce objects look blurr$4 ,f>sight$ness c be rem$i$ by convex glasses1 s9ce !y b5d ! light & br+ x to a clos] focus4 ,convex glasses1 by b5d+ ! rays & br++ !m to a ne>] focus1 ov]balance a %ort eyeball ) its t5d5cy to focus objects beh9d ! ret9a4 ,illu/ration3 ,,fig4 #gi4--,! f>sight$ eye4 ,illu/ration3 ,,fig4 #hj4--,! defect is rem$i$ by convex glasses4 ,a ne>sight$ p]son is "o :o _c see objects unless !y are close to ! eye4 ,! eyeball ( a ne>sight$ p]son is v wide1 & ! ret9a is too f> away f ! cry/all9e l5s4 ,f> objects are br\ght to a focus 9 front ( ! ret9a in/ead ( on x1 & h5ce are n visible4 ,ev5 ?\gh ! muscles ( accommodation d _! be/ to pull out & flatt5 ! l5s1 ! rays are n sep>at$ suffici5tly to focus z f> back z ! ret9a4 ,9 consequ5ce objects look blurr$4 ,ne>sight$ness c be rem$i$ by we>+ concave glasses1 s9ce !y sep>ate ! light & move ! focus f>!r away4 ,concave glasses1 by sep>at+ ! rays & mak+ ! focus m di/ant1 ov]balance a wide eyeball ) its t5d5cy to focus objects 9 front ( ! ret9a4 ,illu/ration3 ,,fig4 #ha4--,! ne>sight$ eye4 ,! defect is rem$i$ by concave glasses4 #aah4 ,heada*e & ,eyes4 ,ord9>ily ! muscles ( accommodation adju/ !mselves easily & quickly2 if1 h[ev]1 !y d n1 frequ5t & sev]e heada*es occur z a result ( too great muscul> ef=t t[>d accommodation4 ,among "y p heada*es are frequ5tly caus$ by ov]-ex]tion ( ! cry/all9e muscles4 ,glasses relieve ! muscles ( ! extra adju/m5t1 & h5ce are effective 9 elim9at+ ?is cause ( heada*e4 ,an exact balance is requir$ betwe5 glasses1 cry/all9e l5s1 & muscul> activity1 & only ^? :o h /udi$ ! subject c>efully are compet5t to treat s s5sitive & necess>y a "p ( ! body z ! eye4 ,! lea/ mi/ake 9 ! curvature ( ! glasses1 ! lea/ flaw 9 ! type ( glass 7= example1 ! k9d ( glass us$71 means an improp] focus1 increas$ duty = ! muscles1 & gradual weak5+ ( ! entire eye1 foll[$ by heada*e & g5]al physical discom=t4 #aai4 ,eye ,/ra94 ,! extra "w :i* is ?r[n ^u ! n]v\s sy/em ?r\gh see+1 read+1 writ+1 & sew+ ) defective eyes is recogniz$ by all physicians z an important cause ( disease4 ,! tax made ^u ! n]v\s sy/em by ! defective eye less5s ! supply ( en]gy available = o!r bodily use1 & ! g5]al heal? suff]s4 ,! heal? is improv$ :5 prop] glasses are prescrib$4 ,possibly ! greate/ dang] ( eye /ra9 is among s*ool *ildr51 :o are n exp]i5c$ en\gh to recognize defects 9 sight4 ,= ?is reason1 _m s*ools employ a physician :o exam9es ! pupils' eyes at regul> int]vals4 ,! foll[+ g5]al precautions are wor? obs]v+3-- #a4 ,re/ ! eyes :5 !y hurt1 & z f> z possible d close "w1 su* z writ+1 read+1 sew+1 wood c>v+1 etc41 by daylight4 #b4 ,nev] read 9 a v bright or a v dim light4 #c4 ,if ! light is ne>1 h x %ad$4 #d4 ,d n rub ! eyes ) ! f+]s4 #e4 ,if eyes are weak1 ba! !m 9 lukew>m wat] 9 :i* a p9* ( borax has be5 dissolv$4 ,,*apt] ,,xii ,,photography #abj4 ,! ,magic ( ! ,sun4 ,ribbons & dresses wa%$ & hung 9 ! sun fade2 :5 wa%$ & hung 9 ! %ade1 !y are n s apt to lose _! color4 ,clo!s are laid away 9 draw]s & hung 9 closets n only = protection aga9/ du/1 b also aga9/ ! well-kn[n p[] ( light to weak5 color4 ,_m h\sewives l[] ! w9d[ %ades t ! wall pap] may n lose its brilliancy1 t ! beautiful hues ( velvet1 sat91 & plu% tape/ry may n be m>r$ by loss 9 brilliancy & %e54 ,bright c>pets & rugs are sometimes b\ght 9 pref]5ce to m delicately t9t$ ones1 because ! pur*as] kn[s t ! latt] w fade quickly if us$ 9 a sunny room1 & w soon acquire a dull mell[ tone4 ,! bright & gay colors & ! dull & somb] colors are all affect$ by ! sun1 b :y "o %\ld be affect$ m ?an ano!r we d n "k4 ,?\s&s ( brilliant & da9ty hues cat* our eye 9 ! %op & on ! /reet1 b n "o ( !m is absolutely p]man5t2 "s may la/ = ye>s1 b !re is always m or less fad+ 9 "t4 ,sunlight causes _m /range1 unexpla9$ effects4 ,if ! two sub/ances1 *lor9e & hydrog51 are mix$ 9 a d>k room1 no?+ rem>kable occurs any m ?an ?\gh wat] & milk 7 mix$1 b if a mixture ( ^! sub/ances is expos$ to sunlight1 a viol5t explosion occurs & an entirely new sub/ance is =m$1 a comp\nd entirely diff]5t 9 "* f ei!r ( its compon5ts4 ,by "s p[] n und]/ood by man1 ! sun is able to =m new sub/ances4 ,9 ! d>k1 *lor9e & hydrog5 are simply *lor9e & hydrog52 9 ! sunlight !y comb9e z if by magic into a totally diff]5t sub/ance4 ,by ! same unexpla9$ p[]1 ! sun frequ5tly does j ! opposite "w2 in/ead ( comb9+ two sub/ances to make "o new product1 ! sun may sep>ate or break d[n "s p>ticul> sub/ance into its v>i\s elem5ts4 ,= example1 if ! sun's rays fall ^u silv] *loride1 a *emical action imm$iately beg9s1 & z a result we h two sep>ate sub/ances1 *lor9e & silv]4 ,! sunlight sep>ates silv] *loride into its con/itu5ts1 silv] & *lor9e4 #aba4 ,! ,magic ,w& 9 ,photography4 ,suppose we coat "o side ( a glass plate ) silv] *loride1 j z we might put a coat ( v>ni% on a *air4 ,we mu/ be v c>eful to coat ! plate 9 ! d>k room1,b o!rwise ! sunlight w sep>ate ! silv] *loride & spoil our plan4 ,!n lay a horse%oe on ! plate = good luck1 & c>ry ! plate out into ! light = a second4 ,! light w sep>ate ! silv] *loride into *lor9e & silv]1 ! latt] ( :i* w rema9 on ! plate z a ?9 film4 ,all ( ! plate 0 affect$ by ! sun except ! portion protect$ by ! horse%oe :i*1 because x is opaque1 w\ld n all[ light to pass ?r\gh & rea* ! plate4 ,if n[ ! plate is c>ri$ back to ! d>k room & ! horse%oe is remov$1 "o w\ld expect to see on ! plate an impression ( ! horse%oe1 because ! portion protect$ by ! horse%oe w\ld be cov]$ by silv] *loride & ! expos$ unprotect$ portion w\ld be cov]$ by metallic silv]4 ,b we are mu* disappo9t$ because ! plate1 :5 exam9$ ev] s c>efully1 %[s n ! slighte/ *ange 9 appe>ance4 ,! *ange is !re1 b ! unaid$ eye _c detect ! *ange4 ,"s *emical1 ! s-call$ develop]1 mu/ be us$ to br+ out ! hidd5 *ange & to reveal ! image to our unsee+ eyes4 ,!re are _m diff]5t develop]s 9 use1 any "o ( :i* w effect ! necess>y trans=mation4 ,:5 ! plate has be5 9 ! develop] = a few seconds1 ! silv] coat+ gradually d>k5s1 & sl[ly b surely ! image pr9t$ by ! sun's rays appe>s4 ,b we mu/ n take ?is picture into ! light1 because ! silv] *loride :i* 0 protect$ by ! horse%oe is /ill pres5t1 & w\ld be /rongly affect$ by ! fir/ glimm] ( light1 &1 z a result1 our entire plate w\ld become simil> 9 "* & !re w\ld be no contra/ to give an image ( ! horse%oe on ! plate4 ,footnote ,b3 ,t is1 a room f :i* ord9>y daylight is exclud$4 ,b a photograph on glass1 :i* mu/ be c>efully %ield$ f ! light & admir$ only 9 ! d>k room1 w\ld be nei!r pleasurable nor practical4 ,if !re 7 "s way by :i* ! hi!rto unaffect$ silv] *loride c\ld be totally remov$1 x w\ld be possible to take ! plate into any light )\t fe>4 ,to accompli% ?is1 ! un*ang$ silv] *loride is got rid ( by ! process te*nically call$ fix+2 t is1 by wa%+ (f ! unr$uc$ silv] *loride ) a solution su* z sodium ?iosulphite1 commonly kn[n z hypo4 ,aft] a ba? 9 ! hypo ! plate is cleans$ 9 cle> runn+ wat] & left to dry4 ,su* a process gives a cle> & p]man5t picture on ! plate4 ,illu/ration3 ,,fig4 #hb4--;,a cam]a4 #abb4 ,! ,cam]a4 ,a cam]a 7,fig4 #hb7 is a light-tight box conta9+ a movable convex l5s at "o end & a scre5 at ! opposite end4 ,light f ! object to be photograph$ passes ?r\gh ! l5s1 falls ^u ! scre51 & =ms an image !re4 ,if we sub/itute = ! ord9>y scre5 a plate or film coat$ ) silv] *loride or any o!r silv] salt1 ! light :i* falls ^u ! s5sitive plate & =ms an image !re w *ange ! silv] *loride & produce a hidd5 image4 ,if ! plate is !n remov$ f ! cam]a 9 ! d>k1 & is treat$ z describ$ 9 ! prec$+ ,section1 ! image becomes visible & p]man5t4 ,9 practice "s gelat9 is mix$ ) ! silv] salt1 & ! mixture is !n p\r$ ov] ! plate or film 9 su* a way t a ?91 ev5 coat+ is made4 ,x is ! pres5ce ( ! gelat9 t gives plates a yell[i% hue4 ,! s5sitive plates are left to dry 9 d>k rooms1 & :5 ! coat+ has become absolutely firm & dry1 ! plates are pack$ 9 boxes & s5t =? = sale4 ,glass plates are heavy & inconv5i5t to c>ry1 s t celluloid films h almo/ entirely tak5 _! place1 at lea/ = outdoor "w4 #abc4 ,light & ,%ade4 ,let u apply ! above process to a real photograph4 ,suppose we wi% to take ! photograph ( a man sitt+ 9 a *air 9 8 libr>y4 ,if ! man wore a gray coat1 a black tie1 & a :ite coll>1 ^! details mu/ be fai?fully repres5t$ 9 ! photograph4 ,h[ c ! almo/ innum]able lights & %ades be produc$ on ! plate8 ,! :ite coll> w\ld s5d ?r\gh ! l5s ! mo/ light to ! s5sitive plate2 h5ce ! silv] *loride on ! plate w\ld be mo/ *ang$ at ! place :]e ! l5s =m$ an image ( ! coll>4 ,! gray coat w\ld n s5d to ! l5s s mu* light z ! :ite coll>1 h5ce ! silv] *loride w\ld be less affect$ by ! light f ! coat ?an by t f ! coll>1 & at ! place :]e ! l5s produc$ an image ( ! coat ! silv] *loride w\ld n be *ang$ s mu* z :]e ! coll> image is4 ,! light f ! face w\ld produce a /ill diff]5t effect1 s9ce ! light f ! face is /rong] ?an ! light f ! gray coat1 b less ?an t f a :ite coll>4 ,! face 9 ! image w\ld %[ less *ang$ silv] *loride ?an ! coll>1 b m ?an ! coat1 because ! face is light] ?an ! coat1 b n s light z ! coll>4 ,f9ally1 ! silv] *loride w\ld be lea/ affect$ by ! d>k tie4 ,! wall pap] 9 ! backgr\nd w\ld affect ! plate accord+ to ! brightness ( ! light :i* fell directly ^u x & :i* reflect$ to ! cam]a4 ,:5 su* a plate has be5 develop$ & fix$1 z describ$ 9 ,section #aba1 we h ! s-call$ negative 7,fig4 #hc74 ,! coll> is v d>k1 ! black tie & gray coat :ite1 & ! :ite tidy v d>k4 ,illu/ration3 ,,fig4 #hc4--;,a negative4 ,! light] ! object1 su* z tidy or coll>1 ! m salt is *ang$1 or1 9 o!r words1 ! great] ! portion ( ! silv] salt t is affect$1 & h5ce ! d>k] ! /a9 on ! plate at t p>ticul> spot4 ,! plate %[s all gradations ( int5sity--! tidy is d>k1 ! black tie is light4 ,! photograph is true z f> z position1 =m1 & expression are conc]n$1 b ! actual int5sities are j rev]s$4 ,h[ ?is plate c be trans=m$ into a photograph true 9 e detail w be se5 9 ! foll[+ ,section4 #abd4 ,! ,p]fect ,photograph4 ,bright objects1 su* z ! sky or a :ite wai/1 *ange mu* ( ! silv] *loride1 & h5ce appe> d>k on ! negative4 ,d>k objects1 su* z furniture or a black coat1 *ange little ( ! *loride1 & h5ce appe> light on ! negative4 ,to obta9 a true photograph1 ! negative is plac$ on a piece ( s5sitive photographic pap]1 or pap] coat$ ) a silv] salt 9 ! same mann] z ! plate & films4 ,! comb9ation is expos$ to ! light4 ,! d>k portions ( ! negative w act z ob/ructions to ! passage ( light1 & b little light w pass ?r\gh t "p ( ! negative to ! photographic pap]1 & consequ5tly b little ( ! silv] salt on ! pap] w be *ang$4 ,on ! o!r h&1 ! light portion ( ! negative w all[ free & easy passage ( ! light rays1 :i* w fall ^u ! photographic pap] & w *ange mu* m ( ! silv]4 ,?us x is t d>k places 9 ! negative produce light places 9 ! positive or real photograph 7,fig4 #hd71 & t light places 9 ! negative produce d>k places 9 ! positive2 all int]m$iate grades are likewise repres5t$ ) _! prop] gradations ( int5sity4 ,illu/ration3 ,,fig4 #hd4--;,a positive or true photograph4 ,if prop]ly treat$1 a negative rema9s good = ye>s1 & w s]ve = an indef9ite numb] ( positives or true photographs4 #abe4 ,light & ,disease4 ,! f>-rea*+ effect :i* light has ^u "s inanimate objects1 su* z photographic films & clo!s1 leads u to inquire into ! relation :i* exi/s betwe5 light & liv+ ?+s4 ,we "k f daily obs]vation t plants mu/ h light 9 ord] to ?rive & gr[4 ,a heal?y plant br\ght into a d>k room soon loses its vigor & fre%ness1 & becomes yell[ & droop+4 ,plants d n all agree z to ! am\nt ( light !y require1 = "s1 l ! violet & ! arbutus1 gr[ be/ 9 mod]ate light1 :ile o!rs1 l ! will[s1 ne$ ! /rong1 full beams ( ! sun4 ,b ne>ly all common plants1 :atev] !y are1 sick5 & die if depriv$ ( sunlight = a long "t4 ,?is is likewise true 9 ! animal _w4 ,dur+ long transportation1 animals are sometimes necess>ily conf9$ 9 d>k c>s1 ) ! result t _m dea?s occur1 ev5 ?\gh ! c> is well air$ & v5tilat$ & ! food supply good4 ,light & fre% air put color into pale *eeks1 j z light & air trans=m sickly1 yell[i% plants into h>dy gre5 ones4 ,pl5ty ( fre% air1 light1 & pure wat] are ! wat*words aga9/ disease4 ,illu/ration3 ,,fig4 #he--,/ems & leaves ( oxalis gr[+ t[>d ! light4 ,9 addition to ! plants & animals :i* we see1 !re are _m /range unse5 ones float+ 9 ! atmosph]e ar\nd u1 ly+ 9 ! du/ ( corn] & closet1 gr[+ 9 ! wat] we dr9k1 & ?rong+ decay$ vegetable & animal matt]4 ,ev]yone kn[s t mildew & v]m9 d damage 9 ! home & 9 ! field1 b v few und]/& t1 9 addition to ^! visible enemies ( man1 !re are sw>ms ( invisible plants & animals "s ( :i* d f> m damage1 bo? directly & indirectly1 ?an ! se5 & famili> enemies4 ,all su* v small plants & animals are kn[n z microorganisms4 ,n all microrganisms are h>mful2 "s are our fri5ds & are z helpful to u z are cultivat$ plants & dome/icat$ animals4 ,among ! mo/ important ( ! microrganisms are bact]ia1 :i* include among _! numb] bo? fri5d & foe4 ,9 ! h\sehold1 bact]ia are a fruitful s\rce ( tr\ble1 b "s ( !m are di/9ctly fri5ds4 ,! delicate flavor ( butt] & ! %>p b pleas+ ta/e ( *eese are produc$ by bact]ia4 ,on ! o!r h&1 bact]ia are ! cause ( _m ( ! mo/ dang]\s diseases1 su* z typhoid fev]1 tub]culosis1 influ5za1 & la grippe4 ,by c>eful obs]vation & exp]im5tation x has be5 %[n conclusively t sunlight rapidly kills bact]ia1 & t x is only 9 dampness & d>kness t bact]ia ?rive & multiply4 ,al?\gh sunlight is ess5tial to ! gr[? ( mo/ plants & animals1 x ret>ds & prev5ts ! gr[? ( bact]ia4 ,dirt & du/ expos$ to ! sunlight lose _! liv+ bact]ia1 :ile 9 damp cell>s & d>k corn]s ! bact]ia ?rive1 increas+ /eadily 9 numb]4 ,= ?is reason our h\ses %\ld be kept light & airy2 bl9ds %\ld be rais$1 ev5 if c>pets d fade2 x is bett] t c>pets & furniture %\ld fade ?an t disease-produc+ bact]ia %\ld f9d a p]man5t abode )9 our dwell+s4 ,kit*5s & pantries 9 p>ticul> %\ld be ?or\ghly light$4 ,b$clo!s1 rugs1 & clo?+ %\ld be expos$ to ! sunlight z frequ5tly z possible2 !re is no bett] safegu>d aga9/ bact]ial disease ?an light4 ,9 a sick room sunlight is especially valuable1 because x n only kills bact]ia1 b keeps ! air dry1 & new bact]ia _c get a />t 9 a dry atmosph]e4 ,,*apt] ,,xiii ,,color #abf4 ,! ,ra9b[4 ,"o ( ! mo/ beautiful & well-kn[n ph5om5a 9 nature is ! ra9b[1 & f "t immemorial x has be5 consid]$ ,jehovah's signal to mank9d t ! /orm is ov] & t ! sun%9e w rema94 ,practically ev]yone kn[s t a ra9b[ c be se5 only :5 ! sun's rays %9e ^u a mi/ ( t9y drops ( wat]4 ,x is ^! t9y drops :i* by _! refraction & _! scatt]+ ( light produce ! ra9b[ 9 ! heav5s4 ,! exquisite t9ts ( ! ra9b[ c be se5 if we look at an object ?r\gh a prism or *&eli] cry/al1 & a v simple exp]im5t enables u to produce on ! wall ( a room ! exact colors ( ! ra9b[ 9 all _! beauty4 ,illu/ration3 ,,fig4 #hf4--,:ite light is a mixture ( lights ( ra9b[ colors4 #abg4 ,h[ to produce ,ra9b[ ,colors4 ,! ,spectrum4 ,if a beam ( sunlight is admitt$ into a d>k room ?r\gh a n>r[ op5+ 9 ! %ade1 & is all[$ to fall ^u a prism1 z %[n 9 ,figure #hf1 a beautiful b& ( colors w appe> on ! opposite wall ( ! room4 ,! ray ( light :i* ent]$ ! room z ord9>y sunlight has n only be5 refract$ & b5t f its /raight pa?1 b x has be5 spread out into a b& ( colors simil> to ^? ( ! ra9b[4 ,:5ev] light passes ?r\gh a prism or l5s1 x is disp]s$ or sep>at$ into all ! colors :i* x conta9s1 & a b& ( colors produc$ 9 ?is way is call$ a spectrum4 ,if we exam9e su* a spectrum we f9d ! foll[+ colors 9 ord]1 ea* color imp]ceptibly fad+ into ! next3 violet1 indigo1 blue1 gre51 yell[1 orange1 r$4 #abh4 ,sunlight or ,:ite ,light4 ,:ite light or sunlight c be disp]s$ or sep>at$ into ! prim>y colors or ra9b[ hues1 z %[n 9 ! prec$+ ,section4 ,:at seems ev5 m wond]ful is t ^! spectral colors c be recomb9$ s z to make :ite light4 ,if a prism ,b 7,fig4 #hg7 exactly simil> to ,a 9 e way is plac$ beh9d ,a 9 a rev]s$ position1 x w undo ! disp]sion ( ,a1 b5d+ upw>d ! sev5 diff]5t beams 9 su* a way t !y em]ge toge!r & produce a :ite spot on ! scre54 ,?us we see1 f two simple exp]im5ts1 t all ! colors ( ! ra9b[ may be obta9$ f :ite light1 & t ^! colors may be 9 turn recomb9$ to produce :ite light4 ,illu/ration3 ,,fig4 #hg4--,ra9b[ colors recomb9$ to =m :ite light4 ,:ite light is n a simple light1 b is compos$ ( all ! colors :i* appe> 9 ! ra9b[4 #abi4 ,color4 ,if a piece ( r$ glass is held 9 ! pa? ( ! color$ beam ( light =m$ z 9 ,section #abg1 all ! colors on ! wall w disappe> except ! r$1 & in/ead ( a beautiful spectrum ( all colors !re w be se5 ! r$ color alone4 ,! r$ glass does n all[ ! passage ?r\gh x ( any light except r$ light2 all o!r colors are absorb$ by ! r$ glass & d n rea* ! eye4 ,only ! r$ ray passes ?r\gh ! r$ glass1 rea*es ! eye1 & produces a s5sation ( color4 ,if a piece ( blue glass is sub/itut$ = ! r$ glass1 ! blue b& rema9s on ! wall1 :ile all ! o!r colors disappe>4 ,if bo? blue & r$ pieces ( glass are held 9 ! pa? ( ! beam1 s t ! light mu/ pass ?r\gh fir/ "o & !n ! o!r1 ! entire spectrum disappe>s & no color rema9s4 ,! blue glass absorbs ! v>i\s rays ) ! exception ( ! blue ones1 & ! r$ glass w n all[ ^! blue rays to pass ?r\gh x2 h5ce no light is all[$ passage to ! eye4 ,an em]ald looks gre5 because x freely transmits gre51 b absorbs ! o!r colors ( :i* ord9>y daylight is compos$4 ,a diamond appe>s :ite because x all[s ! passage ?r\gh x ( all ! v>i\s rays2 ?is is likewise true ( wat] & w9d[ panes4 ,/a9$-glass w9d[s owe _! *>m & beauty to ! pres5ce 9 ! glass ( v>i\s dyes & pigm5ts :i* absorb 9 diff]5t am\nts "s colors f :ite light & transmit o!rs4 ,^! pigm5ts or dyes are add$ to ! glass :ile x is 9 ! molt5 /ate1 & ! beauty ( a /a9$-glass w9d[ dep5ds l>gely ^u ! ri*ness & ! delicacy ( ! pigm5ts us$4 #acj4 ,reflect$ ,light4 ,opaque ,objects4 ,9 ,section #ajf we le>n$ t mo/ objects are visible to u because ( ! light diffusely reflect$ f !m4 ,a :ite object1 su* z a %eet ( pap]1 a :itewa%$ f5ce1 or a table clo?1 absorbs little ( ! light :i* falls ^u x1 b reflects ne>ly all1 ?us produc+ ! s5sation ( :ite4 ,a r$ c>pet absorbs ! light rays incid5t ^u x except ! r$ rays1 & ^! x reflects to ! eye4 ,any sub/ance or object :i* reflects none ( ! rays :i* fall ^u x1 b absorbs all1 appe>s black2 no rays rea* ! eye1 & !re is an abs5ce ( any color s5sation4 ,coal & t> & soot are good illu/rations ( objects :i* absorb all ! light :i* falls ^u !m4 #aca4 ,h[ & ,:y ,colors ,*ange4 ,mat*+ ,colors4 ,mo/ wom5 pref] to %op 9 ! morn+ & e>ly aft]noon :5 ! sunlight illum9ates %ops & factories1 & :5 gas & electricity d n ?r[ _! spell ov] colors4 ,practically all p "k t ribbons & ties1 trimm+s & dresses1 frequ5tly look diff]5t at night f :at !y d 9 ! daytime4 ,x is n safe to mat* colors by artificial light2 clo? :i* looks r$ by night may be almo/ purple by day4 ,inde$1 ! color ( an object dep5ds ^u ! color ( ! light :i* falls ^u x4 ,/range sights are se5 on ! ,f\r? ( ,july :5 v>i\sly color$ fireworks are blaz+4 ,! *ild ) a :ite bl\se appe>s fir/ r$1 !n blue1 !n gre51 accord+ z 8 p[d]s burn r$1 blue1 or gre54 ,! face ( ! *ild *anges f its normal heal?y hue to a brilliant r$ & !n to gha/ly %ades4 ,suppose1 = example1 t a :ite hat is held at ! r$ end ( ! spectrum or 9 any r$ light4 ,! *>act]i/ics ( :ite objects is _! ability to reflect all ! v>i\s rays t fall ^u !m4 ,"h1 h[ev]1 ! only light :i* falls ^u ! :ite hat is r$ light1 h5ce ! only light :i* ! hat has to reflect is r$ light & ! hat consequ5tly appe>s r$4 ,simil>ly1 if a :ite hat is plac$ 9 a blue light1 x w reflect all ! light :i* falls ^u x1 namely1 blue light1 & w appe> blue4 ,if a r$ hat is held 9 a r$ light1 x is se5 9 its prop] color4 ,if a r$ hat is held 9 a blue light1 x appe>s black2 x _c reflect any ( ! blue light because t is all absorb$ & !re is no r$ light to reflect4 ,a *ild we>+ a gre5 frock on ,indep5d5ce ,day seems at night to be we>+ a black frock1 if /&+ ne> p[d]s burn+ ) r$1 blue1 or violet light4 #acb4 ,pure1 ,simple ,colors--,?+s z !y ,seem4 ,to ! eye :ite light appe>s a simple1 s+le color4 ,x reveals its comp\nd nature to u only :5 pass$ ?r\gh a prism1 :5 x %[s itself to be comp\nd$ ( an inf9ite numb] ( colors :i* ,sir ,isaac ,newton gr\p$ 9 sev5 divisions3 violet1 indigo1 blue1 gre51 yell[1 orange1 & r$4 ,we naturally ask ourselves :e!r ^! colors :i* compose :ite light are !mselves 9 turn comp\nd8 ,to answ] t "q1 let u v c>efully ins]t a second prism 9 ! pa? ( ! rays :i* issue f ! fir/ prism1 c>efully b>r+ out ! rema9+ six k9ds ( rays4 ,if ! r$ light is comp\nd1 x w be brok5 up into its con/itu5t p>ts & w =m a typical spectrum ( its own1 j z :ite light did aft] its passage ?r\gh a prism4 ,b ! r$ rays pass ?r\gh ! second prism1 are refract$1 & b5t f ?is c\rse1 & no new colors appe>1 no new spectrum is =m$4 ,evid5tly a ray ( spectrum r$ is a simple color1 n a comp\nd color4 ,if a simil> exp]im5t is made ) ! rema9+ spectrum rays1 ! result is always ! same3 ! individual spectrum colors rema9 simple1 pure colors4 ,! individual spectrum colors are gr\ps ( simple1 pure colors4 ,illu/ration3 ,,fig4 #hh4--,violet & gre5 give blue4 ,gre51 blue1 & r$ give :ite4 #acc4 ,colors n z !y ,seem--,comp\nd ,colors4 ,if "o half ( a c>dbo>d disk 7,fig4 #hh7 is pa9t$ gre51 & ! o!r half violet1 & ! disk is slipp$ ^u a toy top1 & spun rapidly1 ! rotat+ disk w appe> blue2 if r$ & gre5 are us$ 9 ! same way in/ead ( gre5 & violet1 ! rotat+ disk w appe> yell[4 ,a comb9ation ( r$ & yell[ w give orange4 ,! colors =m$ 9 ?is way d n appe> to ! eye diff]5t f ! spectrum colors1 b !y are actually v diff]5t4 ,! spectrum colors1 z we saw 9 ! prec$+ ,section1 are pure1 simple colors1 :ile ! colors =m$ f ! rotat+ disk are 9 reality comp\nd$ ( sev]al totally diff]5t rays1 al?\gh 9 appe>ance ! result+ colors are pure & simple4 ,if x 7 n t colors c be comp\nd$1 we %\ld be limit$ 9 hue & %ade to ! sev5 spectral colors2 ! weal? & beauty ( color 9 nature1 art1 & comm]ce w\ld be unkn[n2 ! fl[]s ) _! ?\s&s ( hues w\ld h a pov]ty ( color undream$ (2 art w\ld lose its mag5ta1 its lilac1 its olive1 its lav5d]1 & w\ld h to "w its wond]s ) ! spectral colors alone4 ,by comp\nd+ v>i\s colors 9 diff]5t proportions1 new colors c be =m$ to give fre%ness & v>iety4 ,if "o ?ird ( ! rotat+ disk is pa9t$ blue1 & ! rema9d] :ite1 ! result is lav5d]2 if fifte5 p>ts ( :ite1 f\r p>ts ( r$1 & "o "p ( blue are arrang$ on ! disk1 ! result is lilac4 ,olive is obta9$ f a comb9ation ( two p>ts gre51 "o "p r$1 & "o "p black2 & ! s(t ri* %ades ( br[n are all due to diff]5t mixtures ( black1 r$1 orange1 or yell[4 #acd4 ,! ,ess5tial ,colors4 ,/range & unexpect$ facts await u at e turn 9 sci5ce6 ,if ! rotat+ c>dbo>d disk 7,fig4 #hh7 is pa9t$ "o ?ird r$1 "o ?ird gre51 & "o ?ird blue1 ! result+ color is :ite4 ,:ile ! mixture ( ! spectral colors produces :ite1 x is n necess>y to h all ( ! spectral colors 9 ord] to obta9 :ite2 because a mixture ( ! foll[+ colors alone1 r$1 gre51 & blue1 w give :ite4 ,moreov]1 by ! mixture ( ^! ?ree colors 9 prop] proportions1 any color ( ! spectrum1 su* z yell[ or indigo or orange1 may be obta9$4 ,! ?ree spectral colors1 r$1 gre51 & blue1 are call$ prim>y or ess5tial hues1 because all kn[n t9ts ( color may be produc$ by ! c>eful bl5d+ ( blue1 gre51 & r$ 9 ! prop] proportions2 = example1 purple is obta9$ by ! bl5d+ ( r$ & blue1 & orange by ! bl5d+ ( r$ & yell[4 #ace4 ,color ,bl9dness4 ,! n]ve fib]s ( ! eye :i* c>ry ! s5sation ( color to ! bra9 are p>ticul>ly s5sitive to ! prim>y colors--r$1 gre51 blue4 ,inde$1 all color s5sations are produc$ by ! /imulation ( ?ree sets ( n]ves :i* are s5sitive to ! prim>y colors4 ,if "o sees purple1 x is because ! optic n]ves s5sitive to r$ & blue 7purple equals r$ plus blue7 h c>ri$ _! sep>ate messages to ! bra91 & ! bl5d+ ( ! two di/9ct messages 9 ! bra9 has giv5 ! s5sation ( purple4 ,if a r$ rose is se51 x is because ! optic n]ves s5sitive to r$ h be5 /imulat$ & h c>ri$ ! message to ! bra94 ,a sn[y field /imulates equally all ?ree sets ( optic n]ves--! r$1 ! gre51 & ! blue4 ,lav5d]1 :i* is "o "p blue & ?ree p>ts :ite1 w\ld /imulate all ?ree sets ( n]ves1 b ) a maximum ( /imulation = ! blue4 ,equal /imulation ( ! ?ree sets w\ld give ! impression ( :ite4 ,a color-bl9d p]son has "s defect 9 "o or m ( ! ?ree sets ( n]ves :i* c>ry ! color message to ! bra94 ,suppose ! n]ve fib]s responsible = c>ry+ ! r$ are totally defective4 ,if su* a p]son views a yell[ fl[]1 he w see x z a gre5 fl[]4 ,yell[ conta9s bo? r$ & gre51 & h5ce bo? ! r$ & gre5 n]ve fib]s %\ld be /imulat$1 b ! r$ n]ve fib]s are defective & d n respond1 ! gre5 n]ve fib]s alone be+ /imulat$1 & ! bra9 !re=e int]prets gre54 ,a well-kn[n au?or gives an amus+ incid5t ( a d9n] p>ty1 at :i* ! ho/ (f]$ /ew$ tomato = apple sauce4 ,:at color n]ves 7 defective 9 ! case ( ! ho/8 ,9 "s employm5ts color bl9dness 9 an employee w\ld be fatal to _m lives4 ,eng9e]s & pilots gov]n ! direction & spe$ ( tra9s & boats l>gely by ! color$ signals :i* fla% out 9 ! night's d>kness or move 9 ! day's bright light1 & any mi/ake 9 ! read+ ( color signals w\ld imp]il ! lives ( travel]s4 ,= ?is reason a rigid te/ 9 color is giv5 to all p]sons seek+ su* employm5t1 & ! ability to mat* ribbons & y>ns ( all ord9>y hues is an unv>y+ requirem5t = effici5cy4 ,,*apt] ,,xiv ,,heat ,,& ,,light ,,z ,,companions ,! night has a ?\s& eyes1 ,& ! day b "o2 ,yet ! light ( ! bright _w dies ,) ! dy+ sun4 #acf4 ,mo/ bodies :i* gl[ & give out light are hot2 ! /ove :i* gl[s ) a w>m r$ is hot & fi]y2 smold]+ wood is black & lifeless2 gl[+ coals are f> hott] ?an black ones4 ,! /a9$-glass w9d[ s(t5s & mell[s ! bright light ( ! sun1 b x also %uts out "s ( ! w>m? ( ! sun's rays2 ! %ady side ( ! /reet sp>es our eyes ! int5se gl>e ( ! sun1 b may *ill u by ! abs5ce ( heat4 ,our illum9ation1 :e!r x be oil lamp or gas jet or electric light1 c>ries ) x heat2 inde$1 s mu* heat t we refra9 f mak+ a light on a w>m summ]'s night because ( ! heat :i* x unavoidably furni%es4 #acg4 ,r$ a ,w>m ,color4 ,we h se5 t heat & light usually g h& 9 h&4 ,9 summ] we l[] ! %ades & close ! bl9ds 9 ord] to keep ! h\se cool1 because ! exclusion ( light means ! exclusion ( "s heat2 9 w9t] we op5 ! bl9ds & raise ! %ades 9 ord] t ! sun may /ream into ! room & flood x ) light & w>m?4 ,! heat ( ! sun & ! light ( ! sun seem boon companions4 ,we c %[ t :5 light passes ?r\gh a prism & is refract$1 =m+ a spectrum1 z 9 ,section #abg1 x is accompani$ by heat4 ,if we hold a s5sitive !rmomet] 9 ! violet end ( ! spectrum s t ! violet rays fall ^u ! bulb1 ! read+ ( ! m]cury w be practically ! same z :5 ! !rmomet] is held 9 any d>k "p ( ! room2 if1 h[ev]1 ! !rmomet] is sl[ly mov$ t[>d ! r$ end ( ! spectrum1 a *ange occurs & ! m]cury rises sl[ly b /eadily1 %[+ t heat rays are pres5t at ! r$ end ( ! spectrum4 ,?is agrees ) ! popul> notion1 =m$ indep5d5tly ( sci5ce1 :i* calls ! r$s ! w>m colors4 ,e "o ( u associates r$ ) w>m?2 9 ! summ] r$ is r>ely worn1 x looks hot2 b 9 w9t] r$ is "o ( ! mo/ pleas+ colors because ( ! s5se ( w>m? & *e] x br+s4 ,all light rays are accompani$ by a small am\nt ( heat1 b ! r$ rays c>ry ! mo/4 ,:at seems p]haps ! mo/ unexpect$ ?+1 is t ! temp]ature1 z indicat$ by a s5sitive !rmomet]1 cont9ues to rise if ! !rmomet] is mov$ j beyond ! r$ light ( ! spectrum4 ,!re actually seems to be m heat beyond ! r$ ?an 9 ! r$1 b if ! !rmomet] is mov$ too f> away1 ! temp]ature aga9 falls4 ,lat] we %all see :at ?is means4 #ach4 ,! ,en]gy ( ! ,sun4 ,x is difficult to tell h[ mu* ( ! en]gy ( ! sun is light & h[ mu* is heat1 b x is easy to det]m9e ! comb9$ effect ( heat & light4 ,illu/ration3 ,,fig4 #hi4--,! en]gy ( ! sun c be measur$ 9 heat units4 ,suppose we all[ ! sun's rays to fall p]p5dicul>ly ^u a metal cyl9d] coat$ ) lampblack & fill$ ) a kn[n quantity ( wat] 7,fig4 #hi72 at ! expiration ( a few h\rs ! temp]ature ( ! wat] w be consid]ably high]4 ,lampblack is a good absorb] ( heat1 & x is us$ z a coat+ 9 ord] t all ! light rays :i* fall ^u ! cyl9d] may be absorb$ & none lo/ by reflection4 ,light & heat rays fall ^u ! lampblack1 pass ?r\gh ! cyl9d]1 & heat ! wat]4 ,we "k t ! r$ light rays h ! l>ge/ %>e t[>d heat+ ! wat]1 because if ! cyl9d] is surr\nd$ by blue glass :i* absorbs ! r$ rays & prev5ts _! passage into ! wat]1 ! temp]ature ( ! wat] beg9s to fall4 ,t ! o!r light rays h a small %>e w\ld h be5 cle> f ! prec$+ ,section4 ,all ! en]gy ( ! sun%9e :i* falls ^u ! cyl9d]1 bo? z heat & z light1 is absorb$ 9 ! =m ( heat1 & ! total am\nt ( ?is en]gy c be calculat$ f ! increase 9 ! temp]ature ( ! wat]4 ,! en]gy :i* heat$ ! wat] w\ld h pass$ onw>d to ! surface ( ! e>? if its pa? _h n be5 ob/ruct$ by ! cyl9d] ( wat]2 & we c be sure t ! en]gy :i* ent]$ ! wat] & *ang$ its temp]ature w\ld ord9>ily h heat$ an equal area ( ! e>?'s surface2 & f ?is1 we c calculate ! en]gy fall+ ^u ! entire surface ( ! e>? dur+ any "o day4 ,computations bas$ ^u ?is exp]im5t %[ t ! e>? receives daily f ! sun ! equival5t ( #cda1jjj1jjj1jjj horse p[]--an am\nt inconceivable to ! human m9d4 ,pr(essor ,"y gives a /rik+ picture ( :at ?is en]gy ( ! sun c\ld d4 ,a solid column ( ice #ic1jjj1jjj miles long & #b-a_/d miles 9 diamet] c\ld be melt$ 9 a s+le second if ! sun c\ld conc5trate its entire p[] on ! ice4 ,:ile ! am\nt ( en]gy receiv$ daily f ! sun by ! e>? is actually enorm\s1 x is small 9 comp>ison ) ! :ole am\nt giv5 out by ! sun to ! num]\s heav5ly bodies :i* make up ! univ]se4 ,9 fact1 ( ! entire outfl[ ( heat & light1 ! e>? receives only "o "p 9 two ?\s& million1 & ?is is a v small portion inde$4 #aci4 ,h[ ,light & ,heat ,travel f ! ,sun to ,u4 ,a/ronom]s tell u t ! sun--! *ief s\rce ( heat & light--is #ic1jjj1jjj miles away f u2 t is1 s f> di/ant t ! fa/e/ express tra9 w\ld require ab\t #agf ye>s to rea* ! sun4 ,h[ d heat & light travel ?r\gh ?is va/ abyss ( space8 ,illu/ration3 ,,fig4 #ij4--,waves =m$ by a pebble4 ,a quiet pool & a pebble w help to make x cle> to u4 ,if we ?r[ a pebble into a quiet pool 7,fig4 #ij71 waves or ripples =m & spread out 9 all directions1 gradually dy+ out z !y become m & m di/ant f ! pebble4 ,x is a /range fact t :ile we see ! ripple mov+ f>!r & f>!r away1 ! p>ticles ( wat] are !mselves n mov+ outw>d & away1 b are m]ely bobb+ up & d[n1 or are vibrat+4 ,if y wi% to be sure ( ?is1 ?r[ ! pebble ne> a spot :]e a *ip lies quiet on ! smoo? pond4 ,aft] ! waves =m1 ! *ip rides up & d[n ) ! wat]1 b does n move outw>d2 if ! wat] itself 7 mov+ outw>d1 x w\ld c>ry ! *ip ) x1 b ! wat] has no =w>d motion1 & h5ce ! *ip assumes ! only motion possess$ by ! wat]1 t is1 an up-&-d[n motion4 ,p]haps a m simple illu/ration is ! appe>ance ( a :eat field or a lawn on a w9dy day2 ! w9d sweeps ov] ! grass1 produc+ 9 ! grass a wave l ! wat] waves ( ! ocean1 b ! blades ( grass d n move f _! accu/om$ place 9 ! gr\nd1 held fa/ z !y are by _! roots4 ,if a pebble is ?r[n into a quiet pool1 x creates ripples or waves :i* spread outw>d 9 all directions1 b :i* soon die out1 leav+ ! pool aga9 placid & undi/urb$4 ,if n[ we c\ld quickly )draw ! pebble f ! pool1 ! wat] w\ld aga9 be di/urb$ & waves w\ld =m4 ,if ! pebble 7 atta*$ to a /r+ s t x c\ld be dropp$ into ! wat] & )drawn at regul> int]vals1 ! waves w\ld nev] h a *ance to disappe>1 because !re w\ld always be a regul>ly tim$ def9ite di/urbance ( ! wat]4 ,le>n$ m5 tell u t all hot bodies & all lum9\s bodies are compos$ ( t9y p>ticles1 call$ molecules1 :i* move unceas+ly back & =? ) great spe$4 ,9 ,section #ie we saw t ! molecules ( all sub/ances move unceas+ly2 _! spe$1 h[ev]1 is n s great1 nor are _! motions s regul>ly tim$ z are ^? ( ! heat-giv+ & ! light-giv+ p>ticles4 ,z ! p>ticles ( ! hot & lum9\s bodies vibrate ) great spe$ & =ce !y viol5tly di/urb ! m$ium ar\nd !m1 & produce a s]ies ( waves simil> to ^? produc$ 9 ! wat] by ! pebble4 ,if1 h[ev]1 a pebble is ?r[n into ! wat] v g5tly1 ! di/urbance is slight1 sometimes too slight to ?r[ ! wat] into waves2 9 ! same way objects ^: molecules are 9 a /ate ( g5tle motion d n produce light4 ,! p>ticles ( heat-giv+ & light-giv+ bodies are 9 a /ate ( rapid vibration1 & !reby di/urb ! surr\nd+ m$ium1 :i* transmits or conveys ! di/urbance to ! e>? or to o!r objects by a tra9 ( waves4 ,:5 ^! waves rea* _! de/9ation1 ! s5sation ( light or heat is produc$4 ,we see ! wat] waves1 b we c nev] see ) ! eye ! heat & light waves :i* roll 9 to u f t f>-di/ant s\rce1 ! sun4 ,we c be sure ( !m only ?r\gh _! effect on our bodies1 & by ! visible "w !y d4 #adj4 ,h[ ,heat & ,light ,diff]4 ,if heat & light are alike due to ! regul>1 rapid motion ( ! p>ticles ( a body1 & are simil>ly convey$ by waves1 h[ is x1 !n1 t heat & light are app>5tly s diff]5t8 ,light & heat diff] z mu* z ! %ort1 *oppy waves ( ! ocean & ! sl[1 long swell ( ! ocean1 b n m s4 ,! sailor h&les 8 boat 9 "o way 9 a *oppy sea & 9 a diff]5t way 9 a roll+ sea1 = he kn[s t ^! two k9ds ( waves act dissimil>ly4 ,! long1 sl[ swell ( ! ocean w\ld correspond ) ! long]1 sl[] waves :i* travel out f ! sun1 & :i* on rea*+ u are int]pret$ z heat4 ,! %ort]1 m frequ5t waves ( ! ocean w\ld typify ! %ort1 rapid waves :i* leave ! sun1 & :i* on rea*+ u are int]pret$ z light4 ,,*apt] ,,xv ,,artificial ,,light+ #ada4 ,we seldom consid] :at life w\ld be )\t our wond]ful me?ods ( illum9ation :i* turn night into day1 & prolong ! h\rs ( "w & pleasure4 ,yet x 0 n until ! n9ete5? c5tury t ! m>vel\s *ange 0 made f ! %ort-liv$ c&le to ! m endur+ oil lamp4 ,be=e ! com+ ( ! lamp1 ev5 9 l>ge cities l ,p>is1 ! only artificial light to guide ! belat$ travel] at night 0 ! c&le requir$ to be kept burn+ 9 an occasional w9d[4 ,) ! inv5tion ( ! k]os5e lamp came m effici5t light+ ( home & /reet1 & ) ! adv5t ( gas & electricity came a light s effective t ! h\rs ( bus9ess1 manufacture1 & pleasure c\ld be ext5d$ f> beyond ! sett+ ( ! sun4 ,! production ( light by c&le1 oil1 & gas w be consid]$ 9 ! foll[+ p>agraphs1 :ile illum9ation by electricity w be res]v$ = a lat] ,*apt]4 #adb4 ,! ,c&le4 ,c&les 7 orig9ally made by dipp+ a wick into melt+ tall[1 )draw+ x1 all[+ ! adh]$ tall[ to h>d51 & repeat+ ! dipp+ until a satisfactory ?ickness 0 obta9$4 ,! m mod]n me?od consi/s 9 p\r+ a fatty prep>ation into a mold1 at ! c5t] ( :i* a wick has be5 plac$4 ,! wick1 :5 light$1 burns = a brief int]val ) a fa9t1 unc]ta9 light2 almo/ imm$iately1 h[ev]1 ! int5sity ( ! light increases & ! illum9ation rema9s good z long z ! c&le la/s4 ,! heat ( ! burn+ tall[ melts m ( ! tall[ ne> x1 & ?is liquid fat is quickly suck$ up into ! burn+ wick4 ,! heat ( ! flame is suffici5t to *ange mo/ ( ?is liquid into a gas1 t is1 to vaporize ! liquid1 & fur!rmore to set fire to ! gas ?us =m$4 ,^! heat$ gases burn ) a bright yell[ flame4 #adc4 ,! ,oil ,lamp4 ,! simple c&le ( our ance/ors 0 n[ replac$ by ! oil lamp1 :i* gave a bright]1 /eadi]1 & m p]man5t illum9ation4 ,! pr9ciple ( ! lamp is simil> to t ( ! c&le1 except t ! wick is saturat$ ) k]os5e or oil r ?an ) fat4 ,! heat f ! burn+ wick is suffici5t to *ange ! oil into a gas & !n to set fire to ! gas4 ,by plac+ a *imney ov] ! burn+ wick1 a con/ant & uni=m draught ( air is ma9ta9$ ar\nd ! blaz+ gases1 & h5ce a /eady1 unflick]+ light is obta9$4 ,gases & c>bon p>ticles are set free by ! burn+ wick4 ,9 ord] t ! gases may burn & ! solid p>ticle gl[1 a pl5tiful supply ( oxyg5 is necess>y4 ,if ! quantity ( air is insuffici5t1 ! c>bon p>ticles rema9 unburn$ & =m soot4 ,a lamp smokes :5 ! air :i* rea*es ! wick is insuffici5t to burn ! rapidly =m$ c>bon p>ticles2 ?is expla9s ! dang] ( turn+ a lamp wick too high & produc+ m c>bon p>ticles ?an c be oxidiz$ by ! air admitt$ ?r\gh ! lamp *imney4 ,"o great disadvantage ( oil lamps & oil /oves is t !y _c be c>ri$ safely f place to place4 ,x is almo/ impossible to c>ry a lamp )\t spill+ ! oil4 ,! flame soon spreads f ! wick to ! ov]fl[+ oil & 9 consequ5ce ! lamp blazes & an explosion may result4 ,c&les1 on ! o!r h&1 are safe f explosion2 ! dripp+ grease is unpleasant b n dang]\s4 ,! illum9ation f a %ad$ oil lamp is s(t & agreeable1 b ! trimm+ ( ! wicks1 ! refill+ ( b[ls1 & ! clean+ ( *imneys require "t & labor4 ,= ?is reason1 ! introduction ( gas met ) widespread success4 ,! illum9ation f an ord9>y gas jet is /rong] ?an t f an ord9>y lamp1 & ! /rong] illum9ation add$ to ! great] conv5i5ce has made gas a v popul> s\rce ( light4 #add4 ,gas ,burn]s & ,gas ,mantles4 ,= a long "t1 ! only gas flame us$ 0 t 9 :i* ! lum9osity result$ 9 heat+ p>ticles ( c>bon to inc&esc5ce4 ,rec5tly1 h[ev]1 t has be5 widely replac$ by use ( a ,buns5 flame ^u an inc&esc5t mantle1 su* z ! ,welsba*4 ,! pr9ciple ( ! inc&esc5t mantle is v simple4 ,:5 c]ta9 sub/ances1 su* z ?orium & c]ium1 are heat$1 !y d n melt or vaporize1 b gl[ ) an int5se bright light4 ,welsba* made use ( ?is fact to secure a burn] 9 :i* ! illum9ation dep5ds ^u ! gl[+ ( an inc&esc5t1 solid mantle1 r ?an ^u ! blaz+ ( a burn+ gas4 ,he made a cyl9drical mantle ( ?9 fabric1 & !n soak$ x 9 a solution ( ?orium & c]ium until x became saturat$ ) ! *emical4 ,! mantle ?us impregnat$ ) ?orium & c]ium is plac$ on ! gas jet1 b be=e ! gas is turn$ on1 a light$ mat* is held to ! mantle 9 ord] to burn away ! ?9 fabric4 ,aft] ! fabric has be5 burn$ away1 !re rema9s a co>se gauze mantle ( ! desir$ *emicals4 ,if n[ ! gas cock is op5$1 ! escap+ gas is ignit$1 ! heat ( ! flame w raise ! mantle to inc&esc5ce & w produce a brilliant light4 ,a v small am\nt ( burn+ gas is suffici5t to raise ! mantle to inc&esc5ce1 & h5ce1 by ! use ( a mantle1 int5se light is secur$ at little co/4 ,! mantle saves u gas1 because ! cock is usually turn$ on full :e!r we use a pla9 burn] or a mantle burn]4 ,b1 nev]!less1 gas is sav$1 because :5 ! mantle is adju/$ to ! gas jet1 ! pressure ( ! gas is less5$ by a me*anical device & h5ce less gas escapes & burns4 ,by actual exp]im5t1 x has be5 f\nd t an ord9>y burn] consumes ab\t five times z mu* gas p] c&le p[] z ! be/ inc&esc5t burn]1 & h5ce is ab\t five times z exp5sive4 ,"o objection to ! mantles is _! t5d5cy to break4 ,b if ! mantles are c>efully adju/$ on ! burn] & are n r\ghly j>r$ 9 use1 !y la/ _m mon?s2 & s9ce ! be/ quality co/ only tw5ty-five c5ts1 ! exp5se ( r5ew+ ! mantles is slight4 #ade4 ,gas = ,cook+4 ,if a cold object is held 9 ! bright flame ( an ord9>y gas jet1 x becomes cov]$ ) soot1 or p>ticles ( unburn$ c>bon4 ,al?\gh ! flame is surr\nd$ by air1 ! c5tral portion ( x does n receive suffici5t oxyg5 to burn up ! num]\s c>bon p>ticles con/antly ?r[n (f by ! burn+ gas1 & h5ce _m c>bon p>ticles rema9 9 ! flame z gl[+1 inc&esc5t masses4 ,t "s unburn$ c>bon is pres5t 9 a flame is %[n by ! fact t :5ev] a cold object is held 9 ! flame1 x becomes smok$ or cov]$ ) soot4 ,if en\gh air 7 suppli$ to ! flame to burn up ! c>bon z fa/ z x 0 set free1 !re w\ld be no deposition ( soot on objects held ov] ! flame or 9 x1 because ! c>bon w\ld be trans=m$ into gase\s matt]4 ,unburn$ c>bon w\ld be objectionable 9 cook+ /oves :]e ut5sils are con/antly 9 contact ) ! flame1 & = ?is reason cook+ /oves are provid$ ) an arrangem5t by means ( :i* additional air is suppli$ to ! burn+ gas 9 quantities adequate to insure complete combu/ion ( ! rapidly =m$ c>bon p>ticles4 ,an op5+ is made 9 ! tube ?r\gh :i* gas passes to ! burn]1 & z ! gas moves pa/ ?is op5+1 x c>ries ) x a draft ( air4 ,^! op5+s are visible on all gas /oves1 & %\ld be kept clean & free ( clogg+1 9 ord] to insure complete combu/ion4 ,s long z ! supply ( air is suffici5t1 ! flame burns ) a dull blue color1 b :5 ! supply falls bel[ t ne$$ = complete burn+ ( ! c>bon1 ! blue color disappe>s1 & a yell[ flame takes its place1 & ) ! yell[ flame ! deposition ( soot is inevitable4 #adf4 ,by-products ( ,coal ,gas4 ,_m important products besides illum9at+ gas are obta9$ f ! di/illation ( s(t coal4 ,ammonia is made f ! liquids :i* collect 9 ! cond5s]s2 anil91 ! s\rce ( exquisite dyes1 is made f ! ?ick1 t>ry di/illate1 & coke is ! residue left 9 ! clay retorts4 ,! coal t> yields n only anil91 b also c>bolic acid & naph?al5e1 bo? ( :i* are comm]cially valuable1 ! =m] z a widely us$ dis9fectant1 & ! latt] z a popul> mo? prev5tive4 ,f a ton ( good gas-produc+ coal c be obta9$ ab\t #aj1jjj cubic feet ( illum9at+ gas1 & z by-products #f p\nds ( ammonia1 #ab gallons ( coal t>1 & #acjj p\nds ( coke4 #adg4 ,natural ,gas4 ,animal & vegetable matt] buri$ 9 ! dep? ( ! e>? sometimes und]goes natural di/illation1 & z a result gas is =m$4 ,! gas produc$ 9 ?is way is call$ natural gas4 ,x is a *eap s\rce ( illum9ation1 b is f\nd 9 relatively few localities & only 9 limit$ quantity4 #adh4 ,acetyl5e4 ,9 #ahib x 0 discov]$ t lime & coal fus$ toge!r 9 ! int5se heat ( ! electric furnace =m$ a cry/all9e1 metallic-look+ sub/ance call$ calcium c>bide4 ,z a result ( t discov]y1 ?is sub/ance 0 soon made on a l>ge scale & sold at a mod]ate price4 ,! *eapness ( calcium c>bide has made x possible = ! isolat$ f>mh\se to disc>d oil lamps & to h a private gas sy/em4 ,:5 ! h>d1 gray cry/als ( calcium c>bide are put 9 wat]1 !y give (f acetyl5e1 a colorless gas :i* burns ) a brilliant :ite flame4 ,if bits ( calcium c>bide are dropp$ into a te/ tube conta9+ wat]1 bubbles ( gas w be se5 to =m & escape into ! air1 & ! escap+ gas may be ignit$ by a burn+ mat* held ne> ! m\? ( ! te/ tube4 ,:5 *emical action betwe5 ! wat] & c>bide has ceas$1 & gas bubbles h /opp$ =m+1 slak$ lime is all t is left ( ! d>k gray cry/als :i* 7 put into ! wat]4 ,:5 calcium c>bide is us$ z a s\rce ( illum9ation1 ! cry/als are me*anically dropp$ into a tank conta9+ wat]1 & ! gas g5]at$ is automatically collect$ 9 a small slid+ tank1 :5ce x passes ?r\gh pipes to ! v>i\s rooms4 ,! slak$ lime1 =m$ :ile ! gas 0 g5]at$1 collects at ! bottom ( ! tanks & is remov$ f "t to "t4 ,! co/ ( an acetyl5e g5]ator is ab\t #ej = a small h\se1 & ! co/ ( ma9t5ance is n m ?an t ( lamps4 ,! g5]ator does n require fill+ (t5] ?an once a week1 & ! labor is less ?an t requir$ = oil lamps4 ,9 a h\se 9 :i* !re 7 tw5ty burn]s1 ! tanks 7 fill$ ) wat] & c>bide b once a =tnight4 ,acetyl5e is seldom us$ 9 l>ge cities1 b x is v widely us$ 9 small communities & is p>ticul>ly conv5i5t 9 m or less remote summ] resid5ces4 ,electric ,lights4 ,! mo/ rec5t & ! mo/ conv5i5t light+ is t obta9$ by electricity4 ,a f9e1 hairlike filam5t )9 a glass bulb is rais$ to inc&esc5ce by ! heat ( an electric curr5t4 ,?is =m ( illum9ation w be consid]$ 9 connection ) electricity4 ,,*apt] ,,xvi ,,man',s ,,way ,,( ,,help+ ,,himself #adi4 ,labor-sav+ ,devices4 ,to primitive man belong$ m especially ! ardu\s tasks ( ! out-(-door life3 ! cle>+ ( pa?s ?r\gh ! wild]ness2 ! haul+ ( mat]ial2 ! break+ up ( ! h>d soil ( b>r5 fields into s(t loam ready to receive ! se$2 ! h>ve/+ ( ! ripe gra91 etc4 ,illu/ration3 ,,fig4 #ia4--,pry+ a /one out ( ! gr\nd4 ,! m intellig5t races among m5 soon le>n$ to help !mselves 9 ^! tasks4 ,= example1 our ance/ors 9 ! field soon le>n$ to pry /ones out ( ! gr\nd 7,fig4 #ia7 r ?an to und]take ! almo/ impossible task ( lift+ !m out ( ! e>? 9 :i* !y 7 emb$d$2 to sw+ fall5 trees away f a pa? by means ( rope atta*$ to "o end r ?an to attempt to remove !m s+le-h&$2 to pit* hay r ?an to lift x2 to cle> a field ) a rake r ?an ) ! h&s2 to c>ry heavy loads 9 :eelb>r[s 7,fig4 #ib7 r ?an on ! %\ld]s2 to roll b>rels up a plank 7,fig4 #ic7 & to raise weights by ropes4 ,9 e case1 :e!r 9 ! lift+ ( /ones1 or ! fell+ ( trees1 or ! transportation ( heavy weights1 or ! digg+ ( ! gr\nd1 man us$ 8 bra9 9 ! inv5tion ( me*anical devices :i* w\ld relieve muscul> /ra9 & light5 physical labor4 ,if all mank9d _h dep5d$ ^u physical /r5g? only1 ! _w to-day w\ld be 9 ! condition preval5t 9 p>ts ( ,africa1 ,asia1 & ,s\? ,am]ica1 :]e ! natives loos5 ! soil ) _! h&s or ) crude implem5ts 7,fig4 #id71 & transport huge weights on _! %\ld]s & heads4 ,illu/ration3 ,,fig4 #ib4--,! :eelb>r[ light5s labor4 ,any me*anical device 7,figs4 #ie & #if71 :]eby man's "w c be m conv5i5tly done1 is call$ a ma*9e2 ! ma*9e itself nev] does any "w--x m]ely enables man to use 8 own ef=ts to bett] advantage4 ,illu/ration3 ,,fig4 #ic4--,roll+ b>rels up a plank4 #aej4 ,:5 d we ,"w8 ,:5ev]1 z a result ( ef=t or =ce1 an object is mov$1 "w is done4 ,if y lift a knapsack f ! floor to ! table1 y d "w because y use =ce & move ! knapsack ?r\gh a di/ance equal to ! height ( ! table4 ,if ! knapsack 7 twice z heavy1 y w\ld ex]t twice z mu* =ce to raise x to ! same height1 & h5ce y w\ld d d\ble ! "w4 ,if y rais$ ! knapsack twice ! di/ance1--say to y\r %\ld]s in/ead ( to ! level ( ! table1--y w\ld d twice ! "w1 because :ile y w\ld ex]t ! same =ce y w\ld cont9ue x ?r\gh d\ble ! di/ance4 ,illu/ration3 ,,fig4 #id4--;,crude me?od ( f>m+4 ,lift+ heavy weights ?r\gh great di/ances is n ! only way 9 :i* "w is done4 ,pa9t+1 *opp+ wood1 hamm]+1 pl[+1 wa%+1 scrubb+1 sew+1 are all =ms ( "w4 ,9 pa9t+1 ! mov+ bru% spreads pa9t ov] a surface2 9 *opp+ wood1 ! desc5d+ ax cleaves ! wood asund]2 9 scrubb+1 ! wet mop rubb$ ov] ! floor c>ries dirt away2 9 e conceivable =m ( "w1 =ce & motion occur4 ,a man does "w :5 he walks1 a woman does "w :5 %e rocks 9 a *air--al?\gh "h ! "w is less ?an 9 walk+4 ,on a w9dy day ! "w done 9 walk+ is great] ?an normal4 ,! w9d resi/s our progress1 & we mu/ ex]t m =ce 9 ord] to cov] ! same di/ance4 ,walk+ ?r\gh a pl[$ or r\gh field is mu* m tir+ ?an to walk on a smoo? road1 because1 :ile ! di/ance cov]$ may be ! same1 ! ef=t put =? is great]1 & h5ce m "w is done4 ,always ! great] ! resi/ance enc\nt]$1 ! great] ! =ce requir$1 & h5ce ! great] ! "w done4 ,! "w done by a boy :o raises a #e-p\nd knapsack to 8 %\ld] w\ld be #ex#d1 or #bj1 provid+ 8 %\ld]s 7 #d feet f ! gr\nd4 ,! am\nt ( "w done dep5ds ^u ! =ce us$ & ! di/ance cov]$ 7sometimes call$ displacem5t71 & h5ce we c say t ,"w =ce multipli$ by di/ance1 or ,w f d4 #aea4 ,ma*9es4 ,a glance into our ma*9e %ops1 our factories1 & ev5 our homes %[s h[ widespread is ! use ( complex ma*9]y4 ,b all ma*9es1 h[ev] complicat$ 9 appe>ance1 are 9 reality b modifications & comb9ations ( "o or m ( f\r simple ma*9es devis$ long ago by our remote ance/ors4 ,^! simple devices are kn[n to-day1 z 7#a7 ! lev]1 repres5t$ by a cr[b>1 a pit*=k2 7#b7 ! incl9$ plane1 repres5t$ by ! plank ^u :i* b>rels are roll$ into a wagon2 7#c7 ! pulley1 repres5t$ by almo/ any contrivance = ! rais+ ( furniture to upp] /ories2 7#d7 ! :eel & axle1 repres5t$ by cog:eels & c(fee gr9d]s4 ,illu/ration3 ,,fig4 #ie4--,primitive me?od ( gr9d+ corn4 ,suppose a #fjj-p\nd b[ld] :i* is emb$d$ 9 ! gr\nd is ne$$ = ! t[] ( a build+4 ,! problem ( ! build] is to get ! heavy b[ld] out ( ! gr\nd1 to load x on a wagon = transportation1 & f9ally to raise x to ! t[]4 ,obvi\sly1 he _c d ?is alone2 ! greate/ am\nt ( =ce ( :i* he is capable w\ld n suffice to accompli% any "o ( ^! tasks4 ,h[ !n does he help himself & p]=m ! impossible8 ,simply1 by ! use ( "s ( ! ma*9e types m5tion$ above1 illu/rations ( :i* are kn[n 9 a g5]al way to e s*oolboy4 ,! v knife ) :i* a /ick is :ittl$ is a ma*9e4 ,illu/ration3 ,,fig4 #if4--,sep>at+ rice gra9s by flail+4 ,illu/ration3 ,,fig4 #ig4--,! pr9ciple ( ! lev]4 #aeb4 ,! ,lev]4 ,balance a foot rule1 conta9+ a hole at its middle po9t ,f1 z %[n 9 ,figure #ig4 ,if n[ a weight ( #a p\nd is susp5d$ f ! b> at "s po9t1 say #ab1 ! balance is di/urb$1 & ! b> sw+s ab\t ! po9t ,f z a c5t]4 ,! balance c be rega9$ by susp5d+ an equival5t weight at ! opposite end ( ! b>1 or by apply+ a #b-p\nd weight at a po9t #c in*es to ! left ( ,f4 ,9 ! latt] case a =ce ( #a p\nd actually balances a =ce ( #b p\nds1 b ! #a-p\nd weight is twice z f> f ! po9t ( susp5sion z is ! #b-p\nd weight4 ,! small weight makes up 9 di/ance :at x lacks 9 magnitude4 ,su* an arrangem5t ( a rod or b> is call$ a lev]4 ,9 any =m ( lev] !re are only ?ree ?+s to be consid]$3 ! po9t :]e ! weight re/s1 ! po9t :]e ! =ce acts1 & ! po9t call$ ! fulcrum ab\t :i* ! rod rotates4 ,! di/ance f ! =ce to ! fulcrum is call$ ! =ce arm4 ,! di/ance f ! weight to ! fulcrum is call$ ! weight arm2 & x is a law ( lev]s1 z well z ( all o!r ma*9es1 t ! =ce multipli$ by ! l5g? ( ! =ce arm mu/ equal ! weight multipli$ by ! l5g? ( ! weight arm4 ,=ce =ce arm weight weight arm4 ,a =ce ( #a p\nd at a di/ance ( #f1 or ) a =ce arm #f1 w balance a weight ( #b p\nds ) a weight arm #c2 t is1 #a #f #b #c4 ,simil>ly a =ce ( #aj p\nds may be made to su/a9 a weight ( #ajj p\nds1 provid+ ! =ce arm is #aj times long] ?an ! weight arm2 & a =ce arm ( #hjj p\nds1 at a di/ance ( #aj feet f ! fulcrum1 may be made to su/a9 a weight ( #hjjj p\nds1 provid+ ! weight is #a foot f ! fulcrum4 #aec4 ,applications ( ! ,lev]4 ,by means ( a lev]1 a #fjj-p\nd b[ld] c be easily pri$ out ( ! gr\nd4 ,let ! lev]1 any /rong metal b>1 be support$ on a /one :i* s]ves z fulcrum2 !n if a man ex]ts 8 =ce at ! end ( ! rod some:at z 9 ,figure #ia 7p4 #aed71 ! =ce arm w be ! di/ance f ! /one or fulcrum to ! end ( ! b>1 & ! weight arm w be ! di/ance f ! fulcrum to ! b[ld] itself4 ,! man pu%es d[n ) a =ce ( #ajj p\nds1 b ) t am\nt succe$s 9 pry+ up ! #fjj-p\nd b[ld]4 ,if1 h[ev]1 y look c>efully1 y w see t ! =ce arm is #f times z long z ! weight arm1 s t ! small] =ce is comp5sat$ = by ! great] di/ance ?r\gh :i* x acts4 ,at fir/ sight x seems z ?\gh ! man's "w 7 done = him by ! ma*9e4 ,b ?is is n s4 ,! man mu/ l[] 8 end ( ! lev] #c feet 9 ord] to raise ! b[ld] #f in*es out ( ! gr\nd4 ,he does n at any "t ex]t a l>ge =ce1 b he accompli%es 8 purpose by ex]t+ a small =ce cont9u\sly ?r\gh a correspond+ly great] di/ance4 ,he f9ds x easi] to ex]t a =ce ( #ajj p\nds cont9u\sly until 8 end has mov$ #c feet r ?an to ex]t a =ce ( #fjj p\nds on ! b[ld] & move x #f in*es4 ,by ! "t ! /one has be5 rais$ ! man has done z mu* "w z ?\gh ! /one _h be5 rais$ directly1 b 8 inability to put =? suffici5t muscul> =ce to raise ! b[ld] directly w\ld h r5d]$ impossible a result :i* 0 easily accompli%$ :5 ?r\gh ! m$ium ( ! lev] he c\ld ext5d 8 small =ce ?r\gh great] di/ance4 #aed4 ,! ,:eelb>r[ z a ,lev]4 ,! pr9ciple ( ! lev] is always ! same2 b ! relative position ( ! important po9ts may v>y4 ,= example1 ! fulcrum is sometimes at "o end1 ! =ce at ! opposite end1 & ! weight to be lift$ betwe5 !m4 ,illu/ration3 ,,fig4 #ih4--;,a slightly diff]5t =m ( lev]4 ,susp5d a /ick ) a hole at its c5t] z 9 ,figure #ih1 & hang a #d-p\nd weight at a di/ance ( #a foot f ! fulcrum1 support+ ! load by means ( a spr+ balance #b feet f ! fulcrum4 ,! po9t] on ! spr+ balance %[s t ! =ce requir$ to balance ! #d-p\nd load is b #b p\nds4 ,! =ce is #b feet f ! fulcrum1 & ! weight 7#d7 is #a foot f ! fulcrum1 s t ,=ce di/ance ,weight di/ance1 or #b #b #d #a4 ,move ! #d-p\nd weight s t x is v ne> ! fulcrum1 say b #f in*es f x2 !n ! spr+ balance regi/]s a =ce only "o f\r? z great z ! weight :i* x susp5ds4 ,9 o!r words a =ce ( #a at a di/ance ( #bd in*es 7#b feet7 is equival5t to a =ce ( #d at a di/ance ( #f in*es4 ,illu/ration3 ,,fig4 #ii4--,! :eelb>r[ light5$ labor4 ,"o ( ! mo/ useful lev]s ( ?is type is ! :eelb>r[ 7,fig4 #ii74 ,! fulcrum is at ! :eel1 ! =ce is at ! h&les1 ! weight is on ! :eelb>r[4 ,if ! load is halfway f ! fulcrum to ! man's h&s1 ! man w h to lift ) a =ce equal to "o half ! load4 ,if ! load is "o f\r? z f> f ! fulcrum z ! man's h&s1 he w ne$ to lift ) a =ce only "o f\r? z great z t ( ! load4 ,illu/ration3 ,,fig4 #ajj4--;,a modifi$ :eelb>r[4 ,?is %[s t 9 load+ a :eelb>r[1 x is important to arrange ! load z ne> to ! :eel z possible4 ,illu/ration3 ,,fig4 #aja4--,! nutcrack] is a lev]4 ,! nutcrack] 7,fig4 #aja7 is an illu/ration ( a d\ble lev] ( ! :eelb>r[ k9d2 ! ne>] ! nut is to ! fulcrum1 ! easi] ! crack+4 ,illu/ration3 ,,fig4 #ajb4--,! h& ex]ts a small =ce ov] a long di/ance & draws out a nail4 ,hamm]s 7,fig4 #ajb71 tack-lift]s1 scissors1 =ceps1 are important lev]s1 & if y w notice h[ _m diff]5t lev]s 7fig4 #ajc7 are us$ by all classes ( m51 y w und]/& h[ valuable a ma*9e ?is simple device is4 #aee4 ,! ,incl9$ ,plane4 ,a man wi%es to load ! #fjj-p\nd b[ld] on a wagon1 & proce$s to d x by means ( a plank1 z 9 ,figure #ic4 ,su* an arrangem5t is call$ an incl9$ plane4 ,! advantage ( an incl9$ plane c be se5 by ! foll[+ exp]im5t4 ,select a smoo? bo>d #d feet long & prop x s t ! end ,a 7,fig4 #ajd7 is #a foot above ! level ( ! table2 ! l5g? ( ! incl9e is !n #d times z great z its height4 ,fa/5 a metal roll] to a spr+ balance & obs]ve its weight4 ,!n pull ! roll] uni=mly upw>d along ! plank & notice :at ! pull is on ! balance1 be+ c>eful always to hold ! balance p>allel to ! incl9e4 ,:5 ! roll] is rais$ along ! incl9e1 ! balance regi/]s a pull only "o f\r? z great z ! actual weight ( ! roll]4 ,t is1 :5 ! roll] weighs #ab1 a =ce ( #c suffices to raise x to ! height ,a along ! incl9e2 b ! small] =ce mu/ be appli$ ?r\gh\t ! entire l5g? ( ! incl9e4 ,9 _m cases1 x is pref]able to ex]t a =ce ( #cj p\nds1 = example1 ov] ! di/ance ,,ca ?an a =ce ( #abj p\nds ov] ! %ort] di/ance ,,ba4 ,illu/ration3 ,,fig4 #ajc4--,primitive man tri$ to light5 8 task by balanc+ 8 burd54 ,prop ! bo>d s t ! end ,a is #b feet above ! table level2 t is1 arrange ! incl9$ plane 9 su* a way t its l5g? is twice z great z its height4 ,9 t case ! /eady pull on ! balance w be "o half ! weight ( ! roll]2 or a =ce ( #f p\nds w suffice to raise ! #ab-p\nd roll]4 ,illu/ration3 ,,fig4 #ajd4--,less =ce is requir$ to raise ! roll] along ! incl9e ?an to raise x to ,a directly4 ,! /eep] ! incl9e1 ! m =ce necess>y to raise a weight2 :]eas if ! incl9e is small1 ! necess>y lift+ =ce is greatly r$uc$4 ,on an incl9$ plane ^: l5g? is t5 times its height1 ! lift+ =ce is r$uc$ to "o t5? ! weight ( ! load4 ,! advantage ( an incl9e dep5ds ^u ! relative l5g? & height1 or is equal to ! ratio ( ! l5g? to ! height4 #aef4 ,application4 ,by ! use ( an incl9$ plank a /rong man c load ! #fjj-p\nd b[ld] on a wagon4 ,suppose ! floor ( ! wagon is #b feet above ! gr\nd1 !n if a #f-;foot plank is us$1 #bjj p\nds ( =ce w suffice to raise ! b[ld]2 b ! man w h to pu% ) ?is =ce aga9/ ! b[ld] :ile x moves ov] ! entire l5g? ( ! plank4 ,s9ce "w is equal to =ce multipli$ by di/ance1 ! man has done "w repres5t$ by #bjj #f1 or #abjj4 ,?is is exactly ! am\nt ( "w :i* w\ld h be5 necess>y to raise ! b[ld] directly4 ,a man ( ev5 enorm\s /r5g? c\ld n lift su* a weight 7#fjj lb47 ev5 an in* directly1 b a /rong man c furni% ! small] =ce 7#bjj7 ov] a di/ance ( #f feet2 h5ce1 :ile ! ma*9e does n less5 ! total am\nt ( "w requir$ ( a man1 x creates a new di/ribution ( "w & makes possible1 & ev5 easy1 results :i* o!rwise w\ld be impossible by human ag5cy4 #aeg4 ,railroads & ,highways4 ,! problem ( ! incl9e is an important "o to eng9e]s :o h "u _! direction ! con/ruction ( our highways & ! lay+ ( our railroad tracks4 ,x requires trem5d\s =ce to pull a load up grade1 & mo/ ( u are famili> ) ! /ruggl+ horse & ! puff+ locomotive4 ,= ?is reason eng9e]s1 :]ev] possible1 level d[n ! /eep places1 & r$uce ! /ra9 z f> z possible4 ,illu/ration3 ,,fig4 #aje4--;,a well-grad$ railroad b$4 ,! slope ( ! road is call$ its grade1 & ! grade itself is simply ! numb] ( feet ! hill rises p] mile4 ,a road a mile long 7#ebhj feet7 has a grade ( #acb if ! cre/ ( ! hill is #acb feet above ! level at :i* ! road />t$4 ,illu/ration3 ,,fig4 #ajf4--;,a long1 gradual asc5t is bett] ?an a %ort]1 /eep] "o4 ,9 su* an incl9e1 ! ratio ( l5g? to height is #ebhj #acb1 or #dj2 & h5ce 9 ord] to pull a tra9 ( c>s to ! summit1 ! eng9e w\ld ne$ to ex]t a cont9u\s pull equal to "o =tie? ( ! comb9$ weight ( ! tra94 ,if1 on ! o!r h&1 ! asc5t _h be5 gradual1 s t ! grade 0 #ff feet p] mile1 a pull f ! eng9e ( "o eightie? ( ! comb9$ weight w\ld h suffic$ to l& ! tra9 ( c>s at ! cre/ ( ! grade4 ,because ( ^! facts1 eng9e]s sp5d great sums 9 grad+ d[n railroad b$s1 mak+ !m z ne>ly level z possible4 ,9 m\nta9\s regions1 ! topography ( ! l& prev5ts ! elim9ation ( all /eep grades1 b nev]!less ! attempt is always made to foll[ ! easie/ grades4 #aeh4 ,! ,w$ge4 ,if an incl9$ plane is pu%$ und]nea? or )9 an object1 x s]ves z a w$ge4 ,usually a w$ge consi/s ( two incl9$ planes 7,fig4 #ajg74 ,illu/ration3 ,,fig4 #ajg4--;,by means ( a w$ge1 ! /ump is split4 ,a *isel & an ax are illu/rations ( w$ges4 ,p]haps ! mo/ univ]sal =m ( a w$ge is our common p94 ,c y expla9 h[ ?is is a w$ge8 #aei4 ,! ,screw4 ,ano!r valuable & indisp5sable =m ( ! incl9$ plane is ! screw4 ,?is consi/s ( a metal rod ar\nd :i* passes a ridge1 & ,figure #ajh %[s cle>ly t a screw is simply a rod ar\nd :i* 79 effect7 an incl9$ plane has be5 wrapp$4 ,illu/ration3 ,,fig4 #ajh--;,a screw z a simple ma*9e4 ,! ridge encircl+ ! screw is call$ ! ?read1 & ! di/ance betwe5 two successive ?reads is call$ ! pit*4 ,x is easy to see t ! clos] ! ?reads & ! small] ! pit*1 ! great] ! advantage ( ! screw1 & h5ce ! less =ce ne$$ 9 ov]com+ resi/ance4 ,a corkscrew is a famili> illu/ration ( ! screw4 #afj4 ,pulleys4 ,! pulley1 ano!r ( ! ma*9es1 is m]ely a groov$ :eel ar\nd :i* a cord passes4 ,x is sometimes m conv5i5t to move a load 9 "o direction r ?an 9 ano!r1 & ! pulley 9 its simple/ =m enables u to d ?is4 ,9 ord] to raise a flag to ! top ( a ma/1 x is n necess>y to climb ! ma/1 & s pull up ! flag2 ! same result is accompli%$ mu* m easily by atta*+ ! flag to a movable /r+1 some:at z 9 ,figure #aji1 & pull+ f bel[4 ,z ! /r+ is pull$ d[n1 ! flag rises & ultimately rea*es ! desir$ position4 ,if we employ a /ation>y pulley1 z 9 ,figure #aji1 we d n *ange ! =ce1 because ! =ce requir$ to balance ! load is z l>ge z ! load itself4 ,! only advantage is t a =ce 9 "o direction may be us$ to produce motion 9 ano!r direction4 ,su* a pulley is kn[n z a fix$ pulley4 ,illu/ration3 ,,fig4 #aji4--;,by means ( a pulley1 a =ce 9 "o direction produces motion 9 ! opposite direction4 #afa4 ,movable ,pulleys4 ,by ! use ( a movable pulley1 we are able to support a weight by a =ce equal to only "o half ! load4 ,9 ,figure #aji1 ! d[nw>d pull ( ! weight & ! d[nw>d pull ( ! h& are equal2 9 ,figure #aaj1 ! spr+ balance supports only "o half ! entire load1 ! rema9+ half be+ borne by ! hook to :i* ! /r+ is atta*$4 ,! weight is divid$ equally betwe5 ! two p>ts ( ! /r+ :i* passes ar\nd ! pulley1 s t ea* /r& be>s only "o half ( ! burd54 ,we h se5 9 our /udy ( ! lev] & ! incl9$ plane t an increase 9 =ce is always accompani$ by a decrease 9 di/ance1 & 9 ! case ( ! pulley we naturally look = a simil> result4 ,if y raise ! balance 7,fig4 #aaj7 #ab feet1 y w f9d t ! weight rises only #f feet2 if y raise ! balance #bd in*es1 y w f9d t ! weight rises #ab in*es4 ,y mu/ ex]cise a =ce ( #ajj p\nds ov] #ab feet ( space 9 ord] to raise a weight ( #bjj p\nds a di/ance ( #f feet4 ,:5 we raise #ajj p\nds ?r\gh #ab feet or #bjj p\nds ?r\gh #f feet ! total "w done is ! same2 b ! pulley enables ^? :o _c furni% a =ce ( #bjj p\nds = ! space ( #f feet to accompli% ! task by furni%+ #ajj p\nds = ! space ( #ab feet4 ,illu/ration3 ,,fig4 #aaj4--;,a movable pulley light5s labor4 #afb4 ,comb9ation ( ,pulleys4 ,a comb9ation ( pulleys call$ block & tackle is us$ :]e v heavy loads are to be mov$4 ,9 ,figure #aaa ! upp] block ( pulleys is fix$1 ! l[] block is movable1 & "o cont9u\s rope passes ar\nd ! v>i\s pulleys4 ,! load is support$ by #f /r&s1 & ea* /r& be>s "o six? ( ! load4 ,if ! h& pulls ) a =ce ( #a p\nd at ,p1 x c raise a load ( #f p\nds at ,w1 b ! h& w h to pull d[nw>d #f feet at ,p 9 ord] to raise ! load at ,w #a foot4 ,if #h pulleys 7 us$1 a =ce equival5t to "o eigh? ( ! load w\ld suffice to move ,w1 b ?is =ce w\ld h to be ex]t$ ov] a di/ance #h times z great z t ?r\gh :i* ,w 0 rais$4 ,illu/ration3 ,,fig4 #aaa4--;,an effective arrangem5t ( pulleys kn[n z block & tackle4 #afc4 ,practical ,application4 ,9 our *ildhood _m ( u saw ) wond] ! appe>ance & disappe>ance ( flags fly+ at ! tops ( high ma/s1 b obs]vation soon taught u t ! flags 7 rais$ by pulleys4 ,9 t5em5ts1 :]e !re is no y>d = ! family wa%+1 clo!s (t5 appe> flapp+ 9 mid-air4 ,?is seems mo/ m>vel\s until we le>n t ! l9es are pull$ back & =? by pulleys at ! w9d[ & at a di/ant support4 ,by means ( pulleys1 awn+s are rais$ & l[]$1 & ! use ( pulleys by furniture mov]s1 etc41 is famili> to e wide-awake obs]v] on ! /reets4 #afd4 ,:eel & ,axle4 ,! :eel & axle consi/s ( a l>ge :eel & a small axle s fa/5$ t !y rotate toge!r4 ,illu/ration3 ,,fig4 #aab4--,! :eel & axle4 ,:5 ! l>ge :eel makes "o revolution1 ,p falls a di/ance equal to ! circumf]5ce ( ! :eel4 ,:ile ,p moves d[nw>d1 ,w likewise moves1 b its motion is upw>d1 & ! di/ance x moves is small1 be+ equal only to ! circumf]5ce ( ! small axle4 ,b a small =ce at ,p w su/a9 a l>g] =ce at ,w2 if ! circumf]5ce ( ! l>ge :eel is #dj in*es1 & t ( ! small :eel #aj in*es1 a load ( #ajj at ,w c be su/a9$ by a =ce ( #be at ,p4 ,! increase 9 =ce ( ! :eel & axle dep5ds ^u ! relative size ( ! two p>ts1 t is1 ^u ! circumf]5ce ( :eel z comp>$ ) circumf]5ce ( axle1 & s9ce ! ratio betwe5 circumf]5ce & radius is con/ant1 ! ratio ( ! :eel & axle comb9ation is ! ratio ( ! long radius to ! %ort radius4 ,= example1 9 a :eel & axle ( radii #bj & #d1 respectively1 a giv5 weight at ,p w\ld balance #e times z great a load at ,w4 #afe4 ,application4 ,w9dlass1 ,cog:eels4 ,9 ! old-fa%ion$ w9dlass us$ 9 f>m+ di/ricts1 ! l>ge :eel is replac$ by a h&le :i*1 :5 turn$1 describes a circle4 ,su* an arrangem5t is equival5t to :eel & axle 7,fig4 #aab72 ! cap/an us$ on %ipbo>d = rais+ ! an*or has ! same pr9ciple4 ,! kit*5 c(fee gr9d] & ! meat *opp] are o!r famili> illu/rations4 ,cog:eels are modifications ( ! :eel & axle4 ,tee? cut 9 ,a fit into simil> tee? cut 9 ,b1 & h5ce rotation ( ,a causes rotation ( ,b4 ,sev]al revolutions ( ! small] :eel1 h[ev]1 are necess>y 9 ord] to turn ! l>g] :eel ?r\gh "o complete revolution2 if ! radius ( ,a is "o half t ( ,b1 two revolutions ( ,a w correspond to "o ( ,b2 if ! radius ( ,a is "o ?ird t ( ,b1 ?ree revolutions ( ,a w correspond to "o ( ,b4 ,illu/ration3 ,,fig4 #aac4--;,cog:eels4 ,exp]im5t demon/rates t a weight ,w atta*$ to a cog:eel ( radius #c c be rais$ by a =ce ,p1 equal to "o ?ird ( ,w appli$ to a cog:eel ( radius #a4 ,!re is ?us a great increase 9 =ce4 ,b ! spe$ ) :i* ,w is rais$ is only "o ?ird ! spe$ ) :i* ! small :eel rotates1 or increase 9 p[] has be5 at ! decrease ( spe$4 ,?is is a v common me?od = rais+ heavy weights by small =ce4 ,cog:eels c be made to give spe$ at ! decrease ( =ce4 ,a heavy weight ,w atta*$ to ,b w 9 its sl[ fall cause rapid rotation ( ,a1 & h5ce rapid rise ( ,p4 ,x is true t ,p1 ! load rais$1 w be less ?an ,w1 ! =ce ex]t$1 b if spe$ is our aim1 ?is ma*9e s]ves our purpose admirably4 ,an extremely important =m ( :eel & axle is t 9 :i* ! two :eels are connect$ by belts z 9 ,figure #aad4 ,rotation ( ,w induces rotation ( w1 & a small =ce at ,w is able to ov]come a l>ge =ce at w4 ,an advantage ( ! belt connection is t p[] at "o place c be transmitt$ ov] a consid]able di/ance & utiliz$ 9 ano!r place4 ,illu/ration3 ,,fig4 #aad4--;,by means ( a belt1 motion c be transf]r$ f place to place4 #aff4 ,comp\nd ,ma*9es4 ,out ( ! few simple ma*9es m5tion$ 9 ! prec$+ ,sections has develop$ ! complex ma*9]y ( to-day4 ,by a comb9ation ( screw & lev]1 = example1 we obta9 ! advantage due to ea* device1 & "s comp\nd ma*9es h be5 made :i* comb9e all ! v>i\s k9ds ( simple ma*9es1 & 9 ?is way multiply _! me*anical advantage _m fold4 ,a relatively simple complex ma*9e call$ ! crane 7,fig4 #aaf7 maybe se5 almo/ any day on ! /reet1 or :]ev] heavy weights are be+ lift$4 ,x is cle> t a =ce appli$ to turn :eel #a causes a sl[] rotation ( :eel #c1 & a /ill sl[] rotation ( :eel #d1 b z #d rotates x w9ds up a *a9 & sl[ly raises ,q4 ,a v complex ma*9e is t se5 9 ,figure #aag4 ,illu/ration3 ,,fig4 #aae4--;,a simple d]rick = rais+ weights4 ,illu/ration3 ,,fig4 #aaf4--;,a travel+ crane4 #afg4 ,measurem5t ( ,"w4 ,9 ,section #aej1 we le>n$ t ! am\nt ( "w done dep5ds ^u ! =ce ex]t$1 & ! di/ance cov]$1 or t ,w =ce di/ance4 ,a man :o raises #e p\nds a height ( #e feet does f> m "w ?an a man :o raises #e ounces a height ( #e in*es1 b ! product ( =ce by di/ance is #be 9 ea* case4 ,!re is difficulty because we h n select$ an arbitr>y unit ( "w4 ,! unit ( "w *os5 & 9 use 9 practical affairs is ! foot p\nd1 & is def9$ z ! "w done :5 a =ce ( #a p\nd acts ?r\gh a di/ance ( #a foot4 ,a man :o moves #h p\nds ?r\gh #f feet does #dh foot p\nds ( "w1 :ile a man :o moves #h ounces 7#a_/b p\nd7 ?r\gh #f in*es 7#a_/b foot7 does only "o f\r? ( a foot p\nd ( "w4 ,illu/ration3 ,,fig4 #aag4--;,a f>m eng9e putt+ 9 a crop4 #afh4 ,! ,p[] or ! ,spe$ ) :i* ,"w is ,done4 ,a man c load a wagon m quickly ?an a gr[+ boy4 ,! "w done by ! "o is equal to ! "w done by ! o!r1 b ! man is m p[]ful1 because ! "t requir$ = a giv5 task is v important4 ,an eng9e :i* hoi/s a #ej-p\nd weight 9 #a second is mu* m p[]ful ?an a man :o requires #ej seconds = ! same task2 h5ce 9 e/imat+ ! value ( a work+ ag5t1 :e!r animal or me*anical1 we mu/ consid] n only ! "w done1 b ! spe$ ) :i* x is done4 ,! rate at :i* a ma*9e is able to accompli% a unit ( "w is call$ p[]1 & ! unit ( p[] cu/om>ily us$ is ! horse p[]4 ,any p[] :i* c d #eej foot p\nds ( "w p] second is said to be "o horse p[] 7,h4,p474 ,?is unit 0 *os5 by ,james ,watt1 ! inv5tor ( a /eam eng9e1 :5 he 0 9 ne$ ( a unit ) :i* to comp>e ! new s\rce ( p[]1 ! eng9e1 ) 8 old s\rce ( p[]1 ! horse4 ,al?\gh call$ a horse p[] x is great] ?an ! p[] ( an av]age horse4 ,an ord9>y man c d "o six? ( a horse p[]4 ,! av]age locomotive ( a railroad has m ?an #ejj ,h4,p41 :ile ! eng9es ( an ocean l9] may h z high z #gj1jjj ,h4,p4 #afi4 ,wa/e ,"w & ,effici5t ,"w4 ,9 our /udy ( ma*9es we omitt$ a factor :i* 9 practical cases _c be ignor$1 namely1 friction4 ,no surface c be made p]fectly smoo?1 & :5 a b>rel rolls ov] an incl9e1 or a rope passes ov] a pulley1 or a cog:eel turns its neighbor1 !re is rubb+ & slipp+ & slid+4 ,motion is ?us h9d]$1 & ! effective value ( ! act+ =ce is less5$4 ,9 ord] to secure ! desir$ result x is necess>y to apply a =ce 9 excess ( t calculat$4 ,?is extra =ce1 :i* mu/ be suppli$ if friction is to be c\nt]act$1 is 9 reality wa/e "w4 ,if ! =ce requir$ by a ma*9e is #aej p\nds1 :ile t calculat$ z necess>y is #ajj p\nds1 ! loss due to friction is #ej p\nds1 & ! ma*9e1 in/ead ( be+ ?or\ghly effici5t1 is only two ?irds effici5t4 ,ma*9i/s make e ef=t to elim9ate f a ma*9e ! wa/e due to friction1 level+ & gr9d+ to ! mo/ p]fect smoo?ness & adju/m5t e "p ( ! ma*9e4 ,:5 ! ma*9e is 9 use1 friction may be fur!r r$uc$ by ! use ( lubricat+ oil4 ,friction c nev] be totally elim9at$1 h[ev]1 & ma*9es ( ev5 ! f9e/ con/ruction lose by friction "s ( _! effici5cy1 :ile poorly con/ruct$ ones lose by friction z mu* z "o half ( _! effici5cy4 #agj4 ,man's ,/r5g? n ,suffici5t = ,ma*9es4 ,a ma*9e1 an in]t mass ( metal & wood1 _c ( itself d any "w1 b c only di/ribute ! en]gy :i* is br\ght to x4 ,=tunately x is n necess>y t ?is en]gy %\ld be contribut$ by man alone1 because ! /ore ( en]gy possess$ by him is v small 9 comp>ison ) ! en]gy requir$ to run locomotives1 automobiles1 sawmills1 etc4 ,p]haps ! greate/ value ( ma*9es lies 9 ! fact t !y enable man to p]=m "w by ! use ( en]gy o!r ?an 8 own4 ,illu/ration3 ,,fig4 #aah4--,man's /r5g? is n suffici5t = heavy "w4 ,figure #aah %[s "o way 9 :i* a horse's en]gy c be utiliz$ 9 lift+ heavy loads4 ,ev5 ! fleet+ w9d has be5 h>ness$ by man1 &1 z 9 ! w9dmill1 made to "w = him 7,fig4 #aai74 ,"o sees dott$ ov] ! c\ntry w9dmills l>ge & small1 & 9 ,holl&1 ! c\ntry ( w9dmills1 ! l&[n] :o does n possess a w9dmill is poor inde$4 ,= g5]ations runn+ wat] f riv]s1 /reams1 & falls has s]v$ man by c>ry+ 8 logs d[n/ream1 by turn+ ! :eels ( 8 mill1 etc42 & 9 our own day runn+ wat] is us$ z an indirect s\rce ( electric lights = /reet & h\se1 ! en]gy ( ! fall+ wat] s]v+ to rotate ! armature ( a dynamo 7,section #caj74 ,illu/ration3 ,,fig4 #aai4--,! w9dmill pumps wat] into ! tr\ghs :]e cattle dr9k4 ,a m con/ant s\rce ( en]gy is t available f ! burn+ ( fuel1 su* z coal & oil4 ,! =m] is ! s\rce ( en]gy 9 locomotives1 ! latt] 9 mo/ automobiles4 ,9 ! foll[+ ,*apt] w be giv5 an acc\nt ( wat]1 w9d1 & fuel z ma*9e fe$]s4 ,,*apt] ,,xvii ,,! ,,p[] ,,beh9d ,,! ,,eng9e #aga4 ,small boys soon le>n ! p[] ( runn+ wat]2 swimm+ or r[+ d[n/ream is easy1 :ile swimm+ or r[+ aga9/ ! curr5t is difficult1 & ! swift] ! wat]1 ! easi] ! "o & ! m difficult ! o!r2 ! riv] assi/s or opposes u z we g ) x or aga9/ x4 ,! wat] ( a quiet pool or ( a g5tle /ream _c d "w1 b wat] :i* is plung+ ov] a precipice or dam1 or is fl[+ d[n /eep slopes1 may be made to saw wood1 gr9d our corn1 light our /reets1 run our electric c>s1 etc4 ,a wat]fall1 or a rapid /ream1 is a great asset to any community1 & = ?is reason %\ld be c>efully gu>d$4 ,wat] p[] is z great a s\rce ( weal? z a coal b$ or a gold m9e4 ,! mo/ trem5d\s wat]fall 9 our c\ntry is ,niag>a ,falls1 :i* e m9ute hurls millions ( gallons ( wat] d[n a #afc-;foot precipice4 ,! en]gy possess$ by su* an enorm\s quantity ( wat] fl[+ at su* a trem5d\s spe$ is almo/ beyond ev]yday compreh5sion1 & w\ld suffice to run ! eng9es ( _m cities f> & ne>4 ,num]\s attempts to buy f ! ,unit$ ,/ates ! "r to utilize "s ( ?is app>5tly wa/$ en]gy h be5 made by v>i\s comm]cial companies4 ,x is =tunate t ^! negotiations h be5 l>gely fruitless1 because mu* deviation ( ! wat] = comm]cial uses & ! in/allation ( ma*9]y 9 ! vic9ity ( ! fam\s falls w\ld greatly detract f ! beauty ( ?is _w-kn[n sc5e1 & w\ld rob our c\ntry ( a natural beauty unequal$ else:]e4 ,illu/ration3 ,,fig4 #abj4--;,a m\nta9 /ream turns ! :eels ( ! mill4 #agb4 ,wat] ,:eels4 ,9 ,figure #abj ! wat] ( a small b rapid m\nta9 /ream is made to rotate a l>ge :eel1 :i* 9 turn communicates its motion ?r\gh belts to a di/ant sawmill or gr9d]4 ,9 m level regions huge dams are built :i* hold back ! wat] & keep x at a high] level ?an ! :eel2 f ! dam ! wat] is convey$ 9 pipes 7flumes7 to ! paddle :eel :i* x turns4 ,cog:eels or belts connect ! paddle :eel ) ! factory ma*9]y1 s t motion ( ! paddle :eel insures ! runn+ ( ! ma*9]y4 ,illu/ration3 ,,fig4 #aba4--,! ,pelton wat] :eel4 ,"o ( ! mo/ effici5t =ms ( wat] :eels is t %[n 9 ,figure #aba1 & call$ ! ,pelton :eel4 ,wat] issues 9 a n>r[ jet simil> to t ( ! ord9>y g>d5 hose & /rikes ) great =ce aga9/ ! l[] "p ( ! :eel1 !reby caus+ rotation ( ! :eel4 ,belts transf] ?is motion to ! ma*9]y ( factory or mill4 #agc4 ,turb9es4 ,! mo/ effici5t =m ( wat] motor is ! turb9e1 a /rong metal :eel %ap$ some:at l a p9 :eel1 inclos$ 9 a heavy metal case4 ,illu/ration3 ,,fig4 #abb--;,a turb9e at ,niag>a ,falls4 ,wat] is convey$ f a res]voir or dam ?r\gh a pipe 7p5/ock7 to ! turb9e case1 9 :i* is plac$ ! heavy metal turb9e :eel 7,fig4 #abb74 ,! =ce ( ! wat] causes rotation ( ! turb9e & ( ! %aft :i* is rigidly fa/5$ to x4 ,! wat] :i* fl[s into ! turb9e case causes rotation ( ! :eel1 escapes f ! case ?r\gh op5+s1 & fl[s into ! tail wat]4 ,! p[] :i* a turb9e c furni% dep5ds ^u ! quantity ( wat] & ! height ( ! fall1 & also ^u ! turb9e :eel itself4 ,"o ( ! l>ge/ turb9es kn[n has a horse p[] ( ab\t #bj1jjj2 t is1 x is equival5t1 approximately1 to #bj1jjj horses4 #agd4 ,h[ mu* is a ,/ream ,wor?8 ,! "w :i* a /ream c p]=m may be easily calculat$4 ,suppose1 = example1 t #ej1jjj p\nds ( wat] fall ov] a #bb-;foot dam e second2 ! p[] ( su* a /ream w\ld be #a1ajj1jjj foot p\nds p] second or #bjjj ,h4,p4 ,naturally1 a "p ( ?is p[] w\ld be lo/ to use by friction )9 ! ma*9]y & by leakage1 s t ! p[] ( a turb9e run by a #bjjj ,h4,p4 /ream w\ld be less ?an t value4 ,( c\rse1 ! horse p[] to be obta9$ f a /ream det]m9es ! size ( ! paddle :eel or turb9e :i* c be run by x4 ,x w\ld be possible to con/ruct a turb9e s l>ge t ! /ream w\ld n suffice to turn ! :eel2 = ?is reason1 ! p[] ( a /ream is c>efully det]m9$ be=e ma*9e con/ruction is begun1 & ! size ( ! ma*9]y dep5ds ^u ! e/imates ( ! wat] p[] furni%$ by exp]t eng9e]s4 ,a r\gh e/imate ( ! volume ( a /ream may be made by ! me?od describ$ bel[3-- ,suppose we all[ a /ream ( wat] to fl[ ?r\gh a rectangul> tr\gh2 ! spe$ ) :i* ! wat] fl[s ?r\gh ! tr\gh c be det]m9$ by not+ ! "t requir$ = a *ip to float ! l5g? ( ! tr\gh2 if ! tr\gh is #aj feet long & ! "t requir$ is #e seconds1 ! wat] has a velocity ( #b feet p] second4 ,illu/ration3 ,,fig4 #abc4--;,e/imat+ ! quantity ( wat] :i* fl[s ?r\gh ! tr\gh ea* second4 ,! quantity ( wat] :i* fl[s ?r\gh ! tr\gh ea* second dep5ds ^u ! dim5sions ( ! tr\gh & ! velocity ( ! wat]4 ,suppose ! tr\gh is #e feet wide & #c feet high1 or has a cross section ( #ae squ>e feet4 ,if ! velocity ( ! wat] 7 #a foot p] second1 !n #ae cubic feet ( wat] w\ld pass any giv5 po9t ea* second1 b s9ce ! velocity ( ! wat] is #b feet p] second1 #cj cubic feet w repres5t ! am\nt ( wat] :i* w fl[ by a giv5 po9t 9 "o second4 #age4 ,quantity ( ,wat] ,furni%$ by a ,riv]4 ,drive /akes 9 ! riv] at v>i\s places & note ! "t requir$ = a *ip to float f "o /ake to ano!r4 ,if we "k ! di/ance betwe5 ! /akes & ! "t requir$ = ! *ip to float f "o /ake to ano!r1 ! velocity ( ! wat] c be readily det]m9$4 ,! wid? ( ! /ream f bank to bank is easily measur$1 & ! dep? is obta9$ 9 ! ord9>y way by s\nd+2 x is necess>y to take a numb] ( s\nd+s because ! b$ ( ! riv] is by no means level1 & s\nd+s tak5 at only "o level w\ld n give an accurate e/imate4 ,if ! s\nd+s %[ ! foll[+ dep?s3 #cj1 #be1 #bj1 #cb1 #bh1 ! av]age dep? c\ld be tak5 z #cj #be #bj #cb #bh #e1 or #bg feet4 ,if1 z a result ( measur+1 ! riv] at a giv5 po9t 9 its c\rse is f\nd to be #bg feet deep & #fj feet wide1 ! area ( a cross section at t spot w\ld be #afbj squ>e feet1 & if ! velocity prov$ to be #f feet p] second1 !n ! quantity ( wat] pass+ 9 any "o second w\ld be #afbj #f1 or #igbj cubic feet4 ,by exp]im5t x has be5 f\nd t #a cu4 ft4 ( wat] weighs ab\t #fb4e lb4 ,! weight ( ! wat] pass+ ea* second w\ld !re=e be #fb4e #igbj1 or #fjg1ejj lb4 ,if ?is quantity ( wat] plunges ov] a #aj-;ft4 dam1 x does #fjg1ejj #aj1 or #f1jge1jjj foot p\nds ( "w p] second1 or #aa1jde ,h4,p4 ,su* a /ream w\ld be v valuable = ! runn+ ( ma*9]y4 #agf4 ,w9dmills4 ,^? ( u :o h sp5t our vacation days 9 ! c\ntry "k t !re is no ready-made wat] supply !re z 9 ! cities1 b t z a rule ! f>mh\ses obta9 _! dr9k+ wat] f spr+s & wells4 ,9 poor] h\ses1 wat] is labori\sly c>ri$ 9 buckets f ! spr+ or is lift$ f ! well by ! w9dlass4 ,9 m prosp]\s h\ses1 pumps are in/all$2 ?is is an improvem5t ov] ! orig9al me?ods1 b ! quantity ( wat] consum$ by ! av]age family is s great z to make ! task ( pump+ an ardu\s "o4 ,! av]age am\nt ( wat] us$ p] day by "o p]son is #be gallons4 ,?is includes wat] = dr9k+1 cook+1 di% wa%+1 ba?+1 laundry4 ,= a family ( five1 !re=e1 ! daily consumption w\ld be #abe gallons2 if to ?is be add$ ! wat] = a s+le horse1 c[1 & pig1 ! total am\nt ne$$ w be approximately #aej gallons p] day4 ,a /rong man c pump t am\nt f an ord9>y well 9 ab\t "o h\r1 b if ! well is deep1 m "t & /r5g? are requir$4 ,! inv5tion ( ! w9dmill 0 a great boon to c\ntry folks because x elim9at$ f _! always busy life "o task 9 :i* labor & "t 7 consum$4 #agg4 ,! ,pr9ciple ( ! ,w9dmill4 ,! toy p9 :eel is a w9dmill 9 m9iature4 ,! w9d /rikes ! sails1 & causes rotation2 & ! /rong] ! w9d bl[s1 ! fa/] w ! :eel rotate4 ,9 w9dmills1 ! sails are ( wood or /eel1 in/ead ( pap]1 b ! pr9ciple is id5tical4 ,illu/ration3 ,,fig4 #abd4--,! toy p9 :eel is a m9iature w9dmill4 ,z ! :eel rotates1 its motion is communicat$ to a me*anical device :i* makes use ( x to raise & l[] a plung]1 & h5ce z long z ! w9d turns ! w9dmill1 wat] is rais$4 ,! wat] ?us rais$ empties into a l>ge tank1 built ei!r 9 ! w9dmill t[] or 9 ! g>ret ( ! h\se1 & f ! tank ! wat] fl[s ?r\gh pipes to ! diff]5t p>ts ( ! h\se4 ,on v w9dy days ! :eel rotates rapidly1 & ! tank fills quickly2 9 ord] to gu>d aga9/ an ov]fl[ f ! tank a me*anical device is in/all$ :i* /ops rotation ( ! :eel :5 ! tank is ne>ly full4 ,! supply tank is usually l>ge en\gh to hold a supply ( wat] suffici5t = sev]al days1 & h5ce a cont9u\s calm ( a day or two does n mat]ially affect ! h\se fl[4 ,:5 once built1 a w9dmill practically takes c>e ( itself1 except = oil+1 & is an effici5t & *eap dome/ic possession4 ,illu/ration3 ,,fig4 #abe4--,! w9dmill pumps wat] into ! tank4 #agh4 ,/eam z a ,work+ ,p[]4 ,if a delicate vane is held at an op5+ f :i* /eam issues1 ! pressure ( ! /eam w cause rotation ( ! vane 7,fig4 #abf71 & if ! vane is connect$ ) a ma*9e1 "w c be obta9$ f ! /eam4 ,:5 wat] is heat$ 9 an op5 vessel1 ! pressure ( its /eam is too l[ to be ( practical value1 b if on ! contr>y wat] is heat$ 9 an almo/ clos$ vessel1 its /eam pressure is consid]able4 ,if /eam at high pressure is direct$ by nozzles aga9/ ! blades ( a :eel1 rapid rotation ( ! :eel ensues j z x did 9 ,figure #aba1 al?\gh 9 ?is case /eam pressure replaces wat] pressure4 ,aft] ! /eam has sp5t itself 9 turn+ ! turb9e1 x cond5ses into wat] & makes its escape ?r\gh op5+s 9 an inclos+ case4 ,9 ,figure #abg ! protect+ case is remov$1 9 ord] t ! =m ( ! turb9e & ! positions ( ! nozzles may be visible4 ,illu/ration3 ,,fig4 #abf4--,/eam z a s\rce ( p[]4 ,illu/ration3 ,,fig4 #abg4--,/eam turb9e ) _m blades & #d nozzles4 ,a s+le l>ge turb9e :eel may h z _m z #hjj1jjj sails or blades1 & /eam may p\r out ^u ^! f _m nozzles4 ,! /eam turb9e is v mu* m effici5t ?an its =]unn]1 ! /eam eng9e4 ,! in/allation ( turb9es on ocean l9]s has be5 accompani$ by great increase 9 spe$1 & by an almo/ correspond+ decrease 9 ! co/ ( ma9t5ance4 #agi4 ,/eam ,eng9es4 ,a v simple illu/ration ( ! work+ ( a /eam eng9e is giv5 9 ,figure #abh4 ,/eam "u pressure ent]s ?r\gh ! op5+ ,f1 passes ?r\gh ,n1 & presses ^u ! pi/on ,m4 ,z a result ,m moves d[nw>d1 & !reby induces rotation 9 ! l>ge :eel ,l4 ,illu/ration3 ,,fig4 #abh4--,! pr9ciple ( ! /eam eng9e4 ,z ,m falls x drives ! air 9 ,d out ?r\gh ,o & ,p 7! op5+ ,p is n visible 9 ! diagram74 ,z soon z ?is is accompli%$1 a me*anical device draws up ! rod ,e1 :i* 9 turn closes ! op5+ ,n1 & ?us prev5ts ! /eam f pass+ into ! "p ( ,d above ,m4 ,b :5 ! rod ,e is 9 su* a position t ,n is clos$1 ,o on ! o!r h& is op51 & /eam ru%es ?r\gh x into ,d & =ces up ! pi/on4 ,?is up-&-d[n motion ( ! pi/on causes cont9u\s rotation ( ! :eel ,l4 ,if ! fire is hot1 /eam is =m$ quickly1 & ! pi/on moves rapidly2 if ! fire is l[1 /eam is =m$ sl[ly1 & ! pi/on moves less rapidly4 ,! /eam eng9e z se5 on our railroad tra9s is v complex1 & _c be discuss$ "h2 9 pr9ciple1 h[ev]1 x is id5tical ) t j describ$4 ,figure #abi %[s a /eam h>ve/] at "w on a mod]n f>m4 ,illu/ration3 ,,fig4 #abi4--,/eam h>ve/] at "w4 ,9 bo? eng9e & turb9e ! real s\rce ( p[] is n ! /eam b ! fuel1 su* z coal or oil1 :i* conv]ts ! wat] into /eam4 #ahj4 ,gas ,eng9es4 ,automobiles h be5 l>gely responsible = ! gas eng9e4 ,to c>ry coal = fuel & wat] = /eam w\ld be impracticable = mo/ motor c>s4 ,electricity is us$ 9 "s c>s1 b ! batt]ies are heavy1 exp5sive1 & %ort-liv$1 & are n always easily replaceable4 ,= ?is reason gasol9e is ext5sively us$1 & 9 ! av]age automobile ! s\rce ( p[] is ! =ce g5]at$ by explod+ gases4 ,x 0 discov]$ "s ye>s ago t if ! vapor ( gasol9e or naph?a 0 mix$ ) a def9ite quantity ( air1 & a light 0 appli$ to ! mixture1 an explosion w\ld result4 ,mod]n sci5ce uses ! =ce ( su* explod+ gases = ! accompli%m5t ( "w1 su* z runn+ ( automobiles & laun*es4 ,9 connection ) ! gasol9e supply is a c>buretor or spray]1 f :i* ! cyl9d] ,c 7,fig4 #acj7 receives a f9e mi/ ( gasol9e vapor & air4 ,?is mixture is ignit$ by an automatic1 electric sp>k+ device1 & ! explosion ( ! gases drives ! pi/on ,p to ! "r4 ,9 ! #d-;cycle type ( gas eng9es 7,fig4 #acj7--! k9d us$ 9 automobiles--! f\r /rokes are z foll[s3 #a4 ,! mixture ( gasol9e & air ent]s ! cyl9d] z ! pi/on moves to ! "r4 #b4 ,! valves be+ clos$1 ! mixture is compress$ z ! pi/on moves to ! left4 #c4 ,! electric sp>k ignites ! compress$ mixture & drives ! pi/on to ! "r4 #d4 ,! wa/e gas is expell$ z ! pi/on moves to ! left4 ,! exhau/ valve is !n clos$1 ! inlet valve op5$1 & ano!r cycle ( f\r /rokes beg9s4 ,illu/ration3 ,,fig4 #acj4--,! gas eng9e4 ,! use ( gasol9e 9 laun*es & automobiles is famili> to _m4 ,n only are laun*es & automobiles mak+ use ( gas p[]1 b ! gasol9e eng9e has made x possible to propel aroplanes ?r\gh ! air4 ,,*apt] ,,xviii ,,pumps ,,& ,,_! ,,value ,,to ,,man #aha4 ,z difficult z = wat] to run up a hill6 ,is !re any "o :o has n he>d ?is say+8 ,& yet mo/ ( u accept z a matt] ( c\rse ! /ream :i* gu%es f our faucet1 or give no ?\ght to ! +5uity :i* devis$ a means ( =c+ wat] upw>d ?r\gh pipes4 ,despite ! fact t wat] fl[s naturally d[n hill1 & n up1 we f9d x available 9 our homes & (fice build+s1 9 "s ( :i* x asc5ds to ! fiftie? floor2 & we see great /reams ( x direct$ ^u ! tops ( burn+ build+s by firem5 9 ! /reets bel[4 ,9 ! c\ntry1 :]e !re are no great c5tral pump+ /ations1 wat] = ! daily ne$ mu/ be rais$ f wells1 & ! supply ( ea* h\sehold is dep5d5t ^u ! labor & =esight ( its memb]s4 ,! wat] may be br\ght to ! surface ei!r by labori\sly rais+ x1 bucket by bucket1 or by ! less ardu\s me?od ( pump+4 ,^! are ! only means possible2 ev5 ! w9dmill does n elim9ate ! necessity = ! pump1 b m]ely replaces ! en]gy us$ by man 9 work+ x4 ,9 "s p>ts ( our c\ntry we h oil b$s or wells4 ,b if ?is und]gr\nd oil is to be ( s]vice to man1 x mu/ be br\ght to ! surface1 & ?is is accompli%$1 z 9 ! case ( wat]1 by ! use ( pumps4 ,an old t9 c or a sponge may s]ve to bale out wat] f a leak+ r[boat1 b su* a crude device w\ld be absurd if employ$ on our huge vessels ( w> & comm]ce4 ,"h a r5t 9 ! %ip's side w\ld mean inevitable loss 7 x n possible to rid ! %ip ( ! infl[+ wat] by ! action ( /rong pumps4 ,ano!r & v diff]5t use to :i* pumps are put is se5 9 ! compression ( gases4 ,air is =c$ into ! tires ( bicycles & automobiles until !y become suffici5tly inflat$ to insure com=t 9 rid+4 ,"s pres5t-day sy/ems ( artificial refrig]ation 7,section #ic7 c\ld n exi/ )\t ! aid ( compress$ gases4 ,compress$ air has play$ a v important role 9 m9+1 be+ s5t into poorly v5tilat$ m9es to improve ! condition ( ! air1 & to supply to ! m9]s ! oxyg5 necess>y = respiration4 ,div]s & m5 :o "w "u wat] c>ry on _! backs a tank ( compress$ air1 & take f x1 at w1 ! am\nt requir$4 ,!re are _m =ms ( pumps1 & !y s]ve widely diff]5t purposes1 be+ ess5tial to ! op]ation ( _m indu/rial und]tak+s4 ,9 ! foll[+ ,sections "s ( ^! =ms w be /udi$4 ,illu/ration3 ,,fig4 #aca4--;,c>ry+ wat] home f ! spr+4 #ahb4 ,! ,air z ,man's ,s]vant4 ,long be=e man h>ness$ wat] = turb9es1 or /eam = eng9es1 he made ! air s]ve 8 purpose1 & by means ( x rais$ wat] f hidd5 und]gr\nd dep?s to ! surface ( ! e>?2 likewise1 by means ( x1 he rais$ to 8 dwell+ on ! hillside wat] f ! /ream 9 ! valley bel[4 ,^? :o live 9 cities :]e runn+ wat] is always pres5t 9 ! home _c realize ! h>d%ip ( ! days :5 ?is ready-made supply did n exi/1 b :5 man labori\sly c>ri$ to 8 dwell+1 f di/ant spr+ & /ream1 ! wat] necess>y = ! daily ne$4 ,:at are ! *>act]i/ics ( ! air :i* h enabl$ man to accompli% ^! feats8 ,!y are well kn[n to u & may be briefly /at$ z foll[s3-- 7#a7 ,air has weight1 & #a cubic foot ( air1 at atmosph]ic pressure1 weighs #a-a_/d ounces4 7#b7 ,! air ar\nd u presses ) a =ce ( ab\t #ae p\nds ^u e squ>e in* ( surface t x t\*es4 7#c7 ,air is ela/ic2 x c be compress$1 z 9 ! balloon or bicycle tire1 b x exp&s imm$iately :5 pressure is r$uc$4 ,z x exp&s & occupies m space1 its pressure falls & x ex]ts less =ce aga9/ ! matt] ) :i* x comes 9 contact4 ,if1 = example1 #a cubic foot ( air is all[$ to exp& & occupy #b cubic feet ( space1 ! pressure :i* x ex]ts is r$uc$ "o half4 ,:5 air is compress$1 its pressure increases1 & x ex]ts a great] =ce aga9/ ! matt] ) :i* x comes 9 contact4 ,if #b cubic feet ( air are compress$ to #a cubic foot1 ! pressure ( ! compress$ air is d\bl$4 7,see ,section #hi47 ,illu/ration3 ,,fig4 #acb4--,! atmosph]e press+ d[nw>d on a pu%es wat] aft] ! ris+ pi/on b4 #ahc4 ,! ,common ,pump or ,lift+ ,pump4 ,place a tube conta9+ a close-fitt+ pi/on 9 a vessel ( wat]1 z %[n 9 ,figure #acb4 ,!n raise ! pi/on ) ! h& & notice t ! wat] rises 9 ! pi/on tube4 ,! rise ( wat] 9 ! pi/on tube is simil> to ! rais+ ( lemonade ?r\gh a /raw 7,section #gg74 ,! atmosph]e presses ) a =ce ( #ae p\nds ^u e squ>e in* ( wat] 9 ! l>ge vessel1 & =ces "s ( x into ! space left vacant by ! retreat+ pi/on4 ,! common pump works 9 a simil> mann]4 ,x consi/s ( a pi/on or plung] :i* moves back & =? 9 an air-tight cyl9d]1 & conta9s an outw>d op5+ valve ?r\gh :i* wat] & air c pass4 ,f ! bottom ( ! cyl9d] a tube runs d[n into ! well or res]voir1 & wat] f ! well has access to ! cyl9d] ?r\gh ano!r outw>d-mov+ valve4 ,9 practice ! tube is kn[n z ! suction pipe1 & its valve z ! suction valve4 ,9 ord] to und]/& ! action ( a pump1 we w suppose t no wat] is 9 ! pump1 & we w pump until a /ream issues f ! sp\t4 ,! v>i\s /ages are repres5t$ diagrammatically by ,figure #acc4 ,9 7#a7 ! entire pump is empty ( wat] b full ( air at atmosph]ic pressure1 & bo? valves are clos$4 ,9 7#b7 ! plung] is be+ rais$ & is lift+ ! column ( air t re/s on x4 ,! air & wat] 9 ! inlet pipe1 be+ ?us p>tially reliev$ ( d[nw>d pressure1 are pu%$ up by ! atmosph]ic pressure on ! surface ( ! wat] 9 ! well4 ,:5 ! pi/on moves d[nw>d z 9 7#c71 ! valve 9 ! pipe closes by its own weight1 & ! air 9 ! cyl9d] escapes ?r\gh ! valve 9 ! plung]4 ,9 7#d7 ! pi/on is aga9 ris+1 repeat+ ! process ( 7#b74 ,9 7#e7 ! process ( 7#c7 is be+ repeat$1 b wat] in/ead ( air is escap+ ?r\gh ! valve 9 ! plung]4 ,9 7#f7 ! process ( 7#b7 is be+ repeat$1 b ! wat] has rea*$ ! sp\t & is fl[+ out4 ,illu/ration3 ,,fig4 #acc4 ,diagram ( ! process ( pump+4 ,aft] ! pump is 9 condition 7#f71 motion ( ! plung] is foll[$ by a m or less regul> dis*>ge ( wat] ?r\gh ! sp\t1 & ! quantity ( wat] :i* gu%es =? dep5ds ^u ! spe$ ) :i* ! pi/on is mov$4 ,a /rong man giv+ quick /rokes c produce a l>ge fl[2 a *ild1 on ! o!r h&1 is able to produce only a ?9 /ream4 ,:oev] pumps mu/ ex]t suffici5t =ce to lift ! wat] f ! surface ( ! well to ! sp\t exit4 ,= ?is reason ! pump has receiv$ ! "n ( lift+ pump4 ,illu/ration3 ,,fig4 #acd4--;,=ce pump4 #ahd4 ,! ,=ce ,pump4 ,9 ! common pump1 wat] _c n be rais$ high] ?an ! sp\t4 ,9 _m cases x is desirable to =ce wat] consid]ably above ! pump itself1 z1 = in/ance1 9 ! fire hose2 "u su* circum/ances a type ( pump is employ$ :i* has receiv$ ! "n ( =ce pump4 ,?is diff]s b little f ! ord9>y lift pump1 z a ref]5ce to ,figure #acd w %[4 ,"h bo? valves are plac$ 9 ! cyl9d]1 & ! pi/on is solid1 b ! pr9ciple is ! same z 9 ! lift+ pump4 ,an upw>d motion ( ! plung] all[s wat] to ent] ! cyl9d]1 & ! d[nw>d motion ( ! plung] drives wat] ?r\gh ,e4 7,is ?is true = ! lift pump z well87 ,s9ce only ! d[nw>d motion ( ! plung] =ces wat] ?r\gh ,e1 ! dis*>ge is int]mitt5t & is !re=e n practical = comm]cial purposes4 ,9 ord] to conv]t ?is int]mitt5t dis*>ge into a /eady /ream1 an air *amb] is in/all$ ne> ! dis*>ge tube1 z 9 ,figure #ace4 ,! wat] =c$ into ! air *amb] by ! d[nw>d-mov+ pi/on compresses ! air & increases its pressure4 ,! pressure ( ! conf9$ air reacts aga9/ ! wat] & t5ds to drive x out ( ! *amb]4 ,h5ce1 ev5 :5 ! plung] is mov+ upw>d1 wat] is =c$ ?r\gh ! pipe because ( ! pressure ( ! compress$ air4 ,9 ?is way a cont9u\s fl[ is secur$4 ,illu/ration3 ,,fig #ace4--,! air *amb] ,a insures a cont9u\s fl[ ( wat]4 ,! height to :i* ! wat] c be =c$ 9 ! pipe dep5ds ^u ! size & con/ruction ( ! pump & ^u ! =ce ) :i* ! plung] c be mov$4 ,! l>g] ! /ream desir$ & ! great] ! height to be rea*$1 ! /rong] ! =ce ne$$ & ! m p[]ful ! con/ruction necess>y4 ,! =ce pump gets its "n f ! fact t ! mov+ pi/on drives or =ces ! wat] ?r\gh ! dis*>ge tube4 #ahe4 ,irrigation & ,dra9age4 ,hi/ory %[s t ! lift+ pump has be5 us$ by man s9ce ! f\r? c5tury be=e ,*ri/2 = _m pres5t-day ent]prises ?is anci5t =m ( pump is inconv5i5t & impracticable1 & h5ce x has be5 replac$ 9 _m cases by m mod]n types1 su* z rot>y & c5trifugal pumps 7,fig4 #acf74 ,9 ^! =ms1 rapidly rotat+ :eels lift ! wat] & drive x onw>d into a dis*>ge pipe1 f :i* x issues ) great =ce4 ,!re is nei!r pi/on nor valve 9 ^! pumps1 & ! quantity ( wat] rais$ & ! =ce ) :i* x is driv5 ?r\gh ! pipes dep5ds solely ^u ! size ( ! :eels & ! spe$ ) :i* !y rotate4 ,irrigation1 or ! artificial wat]+ ( l&1 is ( ! greate/ importance 9 ^? p>ts ( ! _w :]e ! l& is naturally too dry = f>m+4 ,9 ! ,unit$ ,/ates1 approximately two fif?s ( ! l& area is s dry z to be wor?less = agricultural purposes unless artificially wat]$4 ,9 ! ,we/1 sev]al l>ge irrigat+ sy/ems h be5 built by ! f$]al gov]nm5t1 & at pres5t ab\t t5 million acres ( l& h be5 conv]t$ f wor?less f>ms into fields ri* 9 crops4 ,_m irrigat+ sy/ems use c5trifugal pumps to =ce wat] ov] long di/ances & to supply x 9 quantities suffici5t = va/ agricultural ne$s4 ,9 _m regions1 ! success ( a f>m or ran* dep5ds ^u ! irrigation furni%$ 9 dry seasons1 or ^u man's ability to drive wat] f a region ( abundance to a remote region ( sc>city4 ,illu/ration3 ,,fig4 #acf4--;,c5trifugal pump ) "p ( ! cas+ cut away to %[ ! :eel4 ,illu/ration3 ,,fig4 #acg4--;,agriculture made possible by irrigation4 ,! dra9+ ( l& is also a matt] ( consid]able importance2 swamps & m>%es :i* 7 at "o "t consid]$ useless h be5 dra9$ & !n reclaim$ & conv]t$ into good f>m+ l&4 ,! surplus wat] is be/ remov$ by c5trifugal pumps1 s9ce s& & /icks :i* w\ld clog ! valves ( an ord9>y pump are pass$ along )\t difficulty by ! rotat+ :eel4 ,illu/ration3 ,,fig4 #ach4--,rice = its gr[? ne$s p]iodical flood+1 & irrigation (t5 supplies ! necess>y wat]4 #ahf4 ,camp+4--,its ,pleasures & its ,dang]s4 ,! allurem5t ( a vacation camp 9 ! he>t ( ! woods is s great z to make _m camp]s ignore ! vital importance ( secur+ a safe wat] supply4 ,a riv] bank may be beautiful & teem+ ) div]sions1 b if ! riv] is us$ z a s\rce ( dr9k+ wat]1 ! results w almo/ always be fatal to "s4 ,! wat] c be boil$1 x is true1 b few camp]s are will+ to =age = ! additional wood ne$$ = ?is app>5tly unnecess>y requirem5t2 !n1 too1 boil$ wat] does n cool readily 9 summ]1 & h5ce is disagreeable = dr9k+ purposes4 ,! only safe c\rse is to ab&on ! riv] z a s\rce ( dr9k+ wat]1 & if a spr+ _c be f\nd1 to drive a well4 ,9 _m regions1 especially 9 ! neighborhood ( /reams1 wat] c be f\nd t5 or fifte5 feet bel[ ! surface4 ,wat] tak5 f su* a dep? has filt]$ ?r\gh a b$ ( soil1 & is fairly safe = any purpose4 ,( c\rse ! deep] ! well1 ! saf] w be ! wat]4 ,) ! use ( su* a pump z w be describ$1 camp]s c1 )\t grave dang]1 ?r[ di% wat]1 etc41 on ! gr\nd some:at remote f ! camp2 ?is may n injure _! dr9k+ wat] because ! liquids w sl[ly seep ?r\gh ! gr\nd1 & z !y filt] d[nw>d w lose _! dang]\s matt]4 ,all ! wat] :i* rea*es ! well pipes w h filt]$ ?r\gh ! soil b$ & !re=e w probably be safe4 ,b :ile ! c>eless disposal ( wa/es may n spoil ! dr9k+ wat] 79 ! well to be describ$71 o!r laws ( heal? dem& a ?\ghtful disposal ( wa/es4 ,! mal>ial mosquito & ! typhoid fly fl\ri% 9 unhygi5ic qu>t]s1 & ! only way to gu>d aga9/ _! dang]s is to all[ !m nei!r food nor bre$+ place4 ,! burn+ ( g>bage1 ! dis*>ge ( wat]s into cesspools1 or1 9 tempor>y camps1 ! dis*>ge ( wa/es to di/ant po9ts ?r\gh ! ag5cy ( a *eap sewage pipe w insure safety to camp]s1 w less5 ! trials ( flies & mosquitoes1 & w add b little to ! exp5se4 #ahg4 ,a ,*eap ,well = ,camp]s4 ,a two-in* galvaniz$ iron pipe ) a /rong1 po9t$ end conta9+ small p]=ations is driv5 into ! gr\nd ) a sl$ge hamm]4 ,aft] x has p5etrat$ = a few feet1 ano!r l5g? is add$ & ! :ole is driv5 d[n1 & ?is is repeat$ until wat] is rea*$4 ,a *eap pump is !n atta*$ to ! upp] end ( ! drill pipe & s]ves to raise ! wat]4 ,dur+ ! drill+1 "s soil p>ticles get into ! pipe ?r\gh ! p]=ations1 & ^! cl\d ! wat] at fir/2 b aft] ! pipe has once be5 clean$ by ! upw>d-mov+ wat]1 ! supply rema9s cle>4 ,! fl[ f su* a well is naturally small2 fir/1 because wat] is n abundant ne> ! surface ( ! e>?1 & second1 because *eap pumps are poorly con/ruct$ & _c raise a l>ge am\nt4 ,b ! supply w usually be suffici5t = ! ne$s ( simple camp life1 & _m a small f>m uses ?is =m ( well1 n only = h\sehold purposes1 b = wat]+ ! cattle 9 w9t]4 ,if ! *eapness ( su* pumps 7 kn[n1 _! use w\ld be m g5]al = tempor>y purposes4 ,! co/ ( mat]ial ne$ n exce$ #e = a #aj-;foot well1 & ! driv+ ( ! pipe c\ld be made z mu* a "p ( ! camp+ z ! pit*+ ( ! t5t itself4 ,if ! camp+ site is ab&on$ at ! close ( ! vacation1 ! pump c be remov$ & kept ov] w9t] = use ! foll[+ summ] 9 ano!r place4 ,9 ?is way ! actual co/ ( ! wat] supply c be r$uc$ to sc>cely m ?an #c1 ! removable pump be+ a p]man5t possession4 ,9 rocky or m\nta9 regions ! driv5 well is n practicable1 because ! driv+ po9t is blunt$ & brok5 by ! rock & _c pi]ce ! rocky b$s ( l&4 ,illu/ration3 ,,fig4 #aci--;,a driv5 well4 ,illu/ration3 ,,fig4 #adj4--;,diagram %[+ h[ supply+ a city ) good wat] less5s sickness & dea?4 ,! l9es b %[ ! relative numb] ( p :o di$ ( typhoid fev] be=e ! wat] 0 filt]$2 ! l9es a %[ ! numb]s :o di$ aft] ! wat] 0 filt]$4 ,! figures are ! numb] ( typhoid dea?s occurr+ ye>ly out ( #ajj1jjj inhabitants4 #ahh4 ,our ,summ] ,vacation4 ,x has be5 ass]t$ by "s city heal? (ficials t _m cases ( typhoid fev] 9 cities c be trac$ to ! unsanit>y conditions exi/+ 9 summ] resorts4 ,! dr9k+ wat] ( mo/ cities is n[ "u /rict sup]vision1 :ile t ( isolat$ f>ms1 ( small seaside resorts1 & ( scatt]$ m\nta9 hotels is left to ! c>e ( individual proprietors1 & 9 only too _m in/ances receives no att5tion :atev]4 ,! sewage disposal is (t5 inadequate & badly plann$1 & ! wat] becomes dang]\sly contam9at$4 ,a /rong1 heal?y p]son1 ) pl5ty ( outdoor ex]cise & ) hygi5ic habits1 may be able to resi/ ! disease g]ms pres5t 9 ! poor wat] supply2 m (t5 ! summ] gue/s c>ry back ) !m to _! w9t] homes ! g]ms ( disease1 & ^! ga9 ! upp] h& "u ! alt]$ conditions ( city & bus9ess life4 ,x is n too mu* to say t e man & woman %\ld "k ! s\rce ( 8 summ] table wat] & ! me?od ( sewage disposal4 ,if ! conditions are unsanit>y1 !y _c be rem$i$ at once1 b ano!r resort c be f\nd & p]sonal dang] c be avoid$4 ,public s5tim5t & ! loss ( trade w g f> 9 fur!r+ an ef=t t[>d bett] sanitation4 ,9 ! driv5 well1 wat] _c rea* ! sp\t unless x has fir/ filt]$ ?r\gh ! soil to ! dep? ( ! driv5 pipe2 aft] su* a j\rney x is fairly safe1 unless v l>ge quantities ( sewage are pres5t2 g5]ally speak+1 su* a dep? ( soil is able to filt] satisfactorily ! dra9age ( ! limit$ numb] ( p :i* a driv5 well suffices to supply4 ,illu/ration3 ,,fig4 #ada4--;,a deep well ) ! pi/on 9 ! wat]4 ,abundant wat] is r>ely rea*$ at less ?an #ge feet1 & x w\ld usually be impossible to drive a pipe to su* a dep?4 ,:5 a l>ge quantity ( wat] is desir$1 /rong ma*9es drill into ! gr\nd & excavate an op5+ into :i* a wide pipe c be l[]$4 ,i rec5tly sp5t a summ] 9 ! ,pocono ,m\nta9s & saw su* a well complet$4 ,! ma*9e drill$ to a dep? ( #bej feet be=e mu* wat] 0 rea*$ & to ov] #cjj feet be=e a fl[ 0 obta9$ suffici5t to satisfy ! own]4 ,! wat] ?us obta9$ 0 to be ! sole wat] supply ( a hotel accommodat+ #aej p]sons2 ! proprietor calculat$ t ! requirem5ts ( 8 gue/s1 = ba?1 toilet1 laundry1 kit*51 etc41 & ! dome/ics employ$ to s]ve !m1 toge!r ) ! liv]y at _! disposal1 dem&$ a fl[ ( #aj gallons p] m9ute4 ,! gr\nd 0 full ( rock & difficult to p5etrate1 & x requir$ #f weeks ( con/ant "w = two skill$ m5 to drill ! op5+1 l[] ! suction pipe1 & in/all ! pump1 ! co/ be+ approximately #gjj4 ,illu/ration3 ,,fig4 #adb4--,%[+ h[ dr9k+ wat] c be contam9at$ f cesspool 7c7 & wa% wat] 7w74 ,! wat] f su* a well is safe & pure except "u ! conditions repres5t$ 9 ,figure #adb4 ,if sewage or slops be p\r$ ^u ! gr\nd 9 ! neighborhood ( ! well1 ! liquid w seep ?r\gh ! gr\nd & "s may make its way into ! pump be=e x has be5 purifi$ by ! e>?4 ,! impure liquid w ?us contam9ate ! o!rwise pure wat] & w r5d] x decid$ly h>mful4 ,= absolute safety ! sewage dis*>ge %\ld be at lea/ #ge feet f ! well1 & 9 l>ge hotels1 :]e !re is necess>ily a l>ge quantity ( sewage1 ! di/ance %\ld be mu* great]4 ,z ! sewage seeps ?r\gh ! gr\nd x loses its impurities1 b ! quantity ( e>? requir$ to purify x dep5ds ^u its abundance2 a small dep? ( soil _c take c>e ( an indef9ite am\nt ( sewage4 ,h5ce1 ! great] ! numb] ( p 9 a hotel1 or ! m abundant ! sewage1 ! great] %\ld be ! di/ance betwe5 well & sew]4 ,by f> ! be/ way to avoid contam9ation is to see to x t ! sewage dis*>ges into ! gr\nd bel[ ! well2 t is1 to dig ! well 9 su* a location t ! sewage dra9age w be away f ! well4 ,9 cities & t[ns & l>ge summ] communities1 ! sewage ( individual build+s dra9s into common tanks erect$ at public exp5se2 ! cont5ts ( ^! are dis*>g$ 9 turn into h>bors & /reams1 or are o!rwise dispos$ ( at great exp5se1 al?\gh !y conta9 valuable sub/ances4 ,x has be5 e/imat$ t ! dra9age or sewage ( ,engl& alone w\ld be wor? #hj1jjj1jjj a ye> if us$ z f]tiliz]4 ,a few cities1 su* z ,columbus & ,clevel&1 ,ohio1 realize ! ne$ ( utiliz+ ?is s\rce ( weal?1 & by *emical means deodorize _! sewage & *ange x into sub/ances useful = agricultural & indu/rial purposes4 ,!re is /ill a great deal to be le>n$ on ?is subject1 & x is possible t *emically treat$ sewage may be made a s\rce ( income to a community r ?an an exp5se4 #ahi4 ,pumps :i* ,compress ,air4 ,! pumps consid]$ 9 ! prec$+ ,sections h _! wide/ application 9 agricultural di/ricts1 :]e by means ( !m wat] is rais$ to ! surface ( ! e>? or is pump$ into elevat$ tanks4 ,f a comm]cial & indu/rial /&po9t a mo/ important class ( pump is t kn[n z ! compression type2 9 ^!1 air or any o!r gas is compress$ r ?an r>efi$4 ,air brakes & self-op5+ & self-clos+ doors on c>s are op]at$ by means ( compression pumps4 ,! lay+ ( bridge & pi] f\ndations1 9 fact all "w :i* mu/ be done "u wat]1 is possible only ?r\gh ! ag5cy ( compression pumps4 ,^? :o h visit$ m9es1 & h gone into ! he>t ( ! und]gr\nd labyr9?1 "k h[ difficult x is = fre% air to make its way to ! m9]s4 ,compression pumps h elim9at$ ?is difficulty1 & to-day fre% air is con/antly pump$ into ! m9es to supply ! labor]s !re4 ,agricultural me?ods also h be5 modifi$ by ! compression pump4 ,! spray+ ( trees 7,fig4 #adc71 =m]ly done sl[ly & labori\sly1 is n[ a relatively simple matt]4 ,illu/ration3 ,,fig4 #adc4--,spray+ trees by means ( a compression pump4 #aij4 ,! ,bicycle ,pump4 ,! bicycle pump is ! be/ kn[n ( all compression pumps4 ,"h1 z 9 o!r pumps ( its type1 ! valves op5 inw>d r ?an outw>d4 ,:5 ! pi/on is l[]$1 compress$ air is driv5 ?r\gh ! rubb] tub+1 pu%es op5 an inw>d-op5+ valve 9 ! tire1 & ?us ent]s ! tire4 ,:5 ! pi/on is rais$1 ! l[] valve closes1 ! upp] valve is op5$ by atmosph]ic pressure1 & air f outside ent]s ! cyl9d]2 ! next /roke ( ! pi/on drives a fre% supply ( air into ! tire1 :i* ?us 9 "t becomes inflat$4 ,9 mo/ *eap bicycle pumps1 ! pi/on valve is replac$ by a s(t piece ( lea!r s atta*$ to ! pi/on t x all[s air to slip ar\nd x & into ! cyl9d]1 b prev5ts its escape f ! cyl9d] 7,fig4 #add74 ,illu/ration3 ,,fig4 #add4--,! bicycle foot pump4 #aia4 ,h[ a ,man works "u ,wat]4 ,place "o end ( a piece ( glass tube 9 a vessel ( wat] & notice t ! wat] rises 9 ! tube 7,fig4 #ade74 ,bl[ into ! tube & see :e!r y c =ce ! wat] :olly or p>tially d[n ! tube4 ,if ! tube is connect$ to a small compression pump1 suffici5t air c be s5t into ! tube to cause ! wat] to s9k & to keep ! tube p]man5tly cle> ( wat]4 ,?is is1 9 brief1 ! pr9ciple employ$ = "w "u wat]4 ,a compression pump =ces air ?r\gh a tube into ! *amb] 9 :i* m5 are to "w 7,fig4 #adf74 ,! air ?us furni%$ f above supplies ! workm5 ) oxyg51 & by its pressure prev5ts wat] f ent]+ ! *amb]4 ,:5 ! task has be5 complet$1 ! *amb] is rais$ & lat] l[]$ to a new position4 ,illu/ration3 ,,fig4 #ade4--,wat] does n ent] ! tube z long z we bl[ into x4 ,figure #adg %[s m5 at "w on a bridge f\ndation4 ,workm51 tools1 & supplies are l[]$ 9 baskets ?r\gh a c5tral tube ,,bc provid$ ) an air *amb] ,l1 hav+ air-tight gates at ,a & ,a'4 ,! gate ,a is op5$ & workm5 ent] ! air *amb]4 ,! gate ,a is !n clos$ & ! gate ,a' is op5$ sl[ly to give ! m5 "t to get accu/om$ to ! high pressure 9 ,b1 & !n ! m5 are l[]$ to ! bottom4 ,excavat$ e>? is remov$ 9 a simil> mann]4 ,air is suppli$ ?r\gh a tube ,,dd4 ,su* an arrangem5t = "w "u wat] is call$ a caisson4 ,x is held 9 position by a mass ( concrete ,,ee4 ,illu/ration3 ,,fig4 #adf--,! pr9ciple ( "w "u wat]4 ,illu/ration3 ,,fig4 #adg--,%[+ h[ m5 c "w "u wat]4 ,9 _m cases m5 "w 9 div+ suits r ?an 9 caissons2 ^! suits are made ( rubb] except = ! head piece1 :i* is ( metal provid$ ) transp>5t eyepieces4 ,air is suppli$ ?r\gh a flexible tube by a compression pump4 ,! div] sometimes c>ries on 8 back a tank ( compress$ air1 f :i* ! air escapes ?r\gh a tube to ! space betwe5 ! body & ! suit4 ,:5 ! air has become f\l1 ! div] op5s a valve 9 8 suit & all[s x to pass into ! wat]1 at ! same "t admitt+ a fre% supply f ! tank4 ,! valve op5s outw>d f ! body1 & h5ce w all[ ( ! exit ( air b n ( ! entrance ( wat]4 ,:5 ! div] ceases "w & desires to rise to ! surface1 he signals & is drawn up by a rope atta*$ to ! suit4 #aib4 ,comb9ation ( ,pumps4 ,9 _m cases ! comb9$ use ( bo? exhau/ & compression pumps is necess>y to secure ! desir$ result2 z1 = example1 9 pneumatic dispat* tubes4 ,^! are employ$ 9 ! transportation ( lett]s & small packages f build+ to build+ or betwe5 p>ts ( ! same build+4 ,a pump removes air f ! "p ( ! tube ahead ( ! package1 & ?us r$uces ! resi/ance1 :ile a compression pump =ces air into ! tube beh9d ! package & ?us drives x =w>d ) great spe$4 ,,*apt] ,,xix ,,! ,,wat] ,,problem ,,( ,a ,,l>ge ,,city #aic4 ,x is by no means unusual = ! resid5ts ( a l>ge city or t[n to receive ?r\gh ! newspap]s a notification t ! city wat] supply is runn+ l[ & t economy %\ld be ex]cis$ 9 its use4 ,! problem ( supply+ a l>ge city ) an abundance ( pure wat] is among ! mo/ difficult tasks :i* city (ficials h to p]=m1 & is "o little und]/ood & appreciat$ by ! av]age citiz54 ,int5se int]e/ 9 p]sonal & dome/ic affairs is natural1 b e citiz51 ri* or poor1 %\ld h an int]e/ 9 civic affairs z well1 & !re is no bett] or m important place to beg9 ?an ) ! wat] supply4 ,"o ( ! mo/ /irr+ que/ions 9 ,new ,york to-day has to d ) ! con/ruction ( huge aqu$ucts design$ to convey to ! resid5ts ( ! city1 wat] f ! di/ant ,catskill ,m\nta9s4 ,! gr[? ( ! population has be5 s ph5om5ally rapid t ! comb9$ output ( all available ne>-by s\rces does n suffice to meet ! increas+ consumption4 ,:]e does y\r city obta9 its wat]8 ,does x br+ x to its res]voirs 9 ! mo/ economic way possible1 & is !re any legitimate excuse = ! sc>city ( wat] :i* _m communities face 9 dry seasons8 #aid4 ,two ,possibilities4 ,sometimes a city is =tunate en\gh to be situat$ ne> hills & m\nta9s ?r\gh :i* /reams fl[1 & 9 t case ! wat] problem is simple4 ,9 su* a case all t is necess>y is to run pipes1 usually und]gr\nd1 f ! elevat$ lakes or /reams to ! individual h\ses1 or to common res]voirs f :i* x is di/ribut$ to ! v>i\s build+s4 ,illu/ration3 ,,fig4 #adh4--,! elevat$ m\nta9 lake s]ves z a s\rce ( wat]4 ,figure #adh illu/rates 9 a simple way ! mann] 9 :i* a m\nta9 lake may s]ve to supply ! inhabitants ( a valley4 ,! city ( ,d5v]1 = example1 is surr\nd$ by m\nta9s ab\nd+ 9 /reams ( pure1 cle> wat]2 pipes convey ! wat] f ^! heights to ! city1 & ?us a *eap & adequate fl[ is obta9$4 ,su* a sy/em is kn[n z ! gravity sy/em4 ,! ne>] & /eep] ! elevation1 ! great] ! =ce ) :i* ! wat] fl[s ?r\gh ! valley pipes1 & h5ce ! /rong] ! dis*>ge f ! faucets4 ,relatively few cities & t[ns are s favorably situat$ z reg>ds wat]2 m (t5 ! m\nta9s are too di/ant1 or ! elevation is too slight1 to be ( practical value4 ,cities situat$ 9 pla9s & remote f m\nta9s are oblig$ to utilize ! wat] ( su* /reams z fl[ ?r\gh ! l&1 =c+ x to ! necess>y height by means ( pumps4 ,/reams :i* fl[ ?r\gh populat$ regions are apt to be contam9at$1 & h5ce wat] f !m requires public filtration4 ,cities us+ su* a wat] supply ?us h ! d\ble exp5se ( pump+ & filtration4 #aie4 ,! ,pressure ( ,wat]4 ,no practical bus9ess man w\ld erect a turb9e or paddle :eel )\t calculat+ 9 advance ! value ( 8 wat] p[]4 ,! paddle :eel might be s heavy t ! /ream c\ld n turn x1 or s frail 9 comp>ison ) ! wat] =ce t ! /ream w\ld de/roy x4 ,9 j z c>eful a mann]1 ! size & ! /r5g? ( municipal res]voirs & pumps mu/ be calculat$4 ,! great] ! quantity ( wat] to be held 9 ! res]voir1 ! heavi] are ! walls requir$2 ! great] ! elevation ( ! h\ses1 ! /rong] mu/ be ! pumps & ! eng9es :i* run !m4 ,9 ord] to und]/& h[ ^! calculations are made1 we mu/ /udy ! physical *>act]i/ics ( wat] j z we /udi$ ! physical *>act]i/ics ( air4 ,:5 we measure wat]1 we f9d t #a cubic foot ( x weighs ab\t #fb4e p\nds2 ?is is equival5t to say+ t wat] #a foot deep presses on ! bottom ( ! conta9+ vessel ) a =ce ( #fb4e p\nds to ! squ>e foot4 ,if ! wat] is #b feet deep1 ! load support$ by ! vessel is d\bl$1 & ! pressure on ea* squ>e foot ( ! bottom ( ! vessel w be #abe p\nds1 & if ! wat] is #aj feet deep1 ! load borne by ea* squ>e foot w be #fbe p\nds4 ,! deep] ! wat]1 ! great] w be ! weight su/a9$ by ! conf9+ vessel & ! great] ! pressure ex]t$ by ! wat]4 ,illu/ration3 ,,fig4 #adi4--,wat] #a foot deep ex]ts a pressure ( #fb4e p\nds a squ>e foot4 ,s9ce ! pressure borne by #a squ>e foot ( surface is #fb4e p\nds1 ! pressure support$ by #a squ>e in* ( surface is #a_/add ( #fb4e p\nds1 or 4#dc p\nd1 ne>ly #a_/b p\nd4 ,suppose a vessel held wat] to ! dep? ( #aj feet1 !n ^u e squ>e in* ( ! bottom ( t vessel !re w\ld be a pressure ( #d4cd p\nds4 ,if a "o-in* tap 7 ins]t$ 9 ! bottom ( ! vessel s t ! wat] fl[$ out1 x w\ld gu% =? ) a =ce ( #d4cd p\nds4 ,if ! wat] 7 #bj feet deep1 ! =ce ( ! outfl[+ wat] w\ld be twice z /rong1 because ! pressure w\ld be d\bl$4 ,b ! fl[ w\ld n rema9 con/ant1 because z ! wat] leaves ! outlet1 less & less ( x rema9s 9 ! vessel1 & h5ce ! pressure gradually s9ks & ! fl[ drops correspond+ly4 ,9 seasons ( prolong$ dr\ght1 ! /reams :i* fe$ a city res]voir are apt to conta9 less ?an ! usual am\nt ( wat]1 h5ce ! level ( ! wat] supply s9ks1 ! pressure at ! outlet falls1 & ! =ce ( ! outfl[+ wat] is less5$ 7,fig4 #aej74 ,illu/ration3 ,,fig4 #aej4--,! pressure at an outlet decreases z ! level ( ! wat] supply s9ks4 #aif4 ,:y ! ,wat] ,supply is n uni=m 9 ,all ,p>ts ( ! ,city4 ,9 ! prec$+ ,section1 we saw t ! fl[ f a faucet dep5ds ^u ! height ( ! res]ve wat] above ! tap4 ,h\ses on a level ) ! ma9 supply pipes 7,figs4 #adh & #aea7 h a /rong fl[ because ! wat] is "u ! pressure ( a column ,a2 h\ses situat$ on elevation ,b h less fl[1 because ! wat] is "u ! pressure ( a %ort] column ,b2 & h\ses at a consid]able elevation ,c h a less rapid fl[ correspond+ to ! dim9i%$ dep? 7,c74 ,n only does ! fl[ v>y ) ! elevation ( ! h\se1 b x v>ies ) ! location ( ! faucet )9 ! h\se4 ,unless ! res]voir is v high1 or ! pumps v p[]ful1 ! fl[ on ! upp] floors is noticeably less ?an t 9 ! cell>1 & 9 ! upp] /ories ( "s high build+ ! fl[ is sc>cely m ?an a feeble trickle4 ,illu/ration3 ,,fig4 #aea4--,wat] pressure v>ies 9 diff]5t p>ts ( a wat] sy/em4 ,:5 ! respective fl[s at ,a1 ,b1 & ,c 7,fig4 #aea7 are measur$1 !y are f\nd to be f> l[] ?an ! pressures :i* columns ( wat] ( ! heights ,a1 ,b1 & ,c h be5 %[n by actual demon/ration to ex]t4 ,?is is because wat]1 9 fl[+ f place to place1 exp5ds =ce 9 ov]com+ ! friction ( ! pipes & ! resi/ance ( ! air4 ,! great] ! di/ance trav]s$ by ! wat] 9 its j\rney f res]voir to faucet1 ! great] ! wa/e =ce & ! less ! f9al fl[4 ,9 practice1 l>ge ma9s lead f ! res]voir to ! city1 small] ma9s convey ! wat] to ! v>i\s sections ( ! city1 & s]vice pipes lead to ! individual h\se taps4 ,dur+ ?is long j\rney1 consid]able =ce is exp5d$ aga9/ friction1 & h5ce ! fl[ at a di/ance f ! res]voir falls to b a fraction ( its orig9al /r5g?4 ,= ?is reason1 build+s situat$ ne> ! ma9 supply h a mu* /rong] fl[ 7,fig4 #aeb7 ?an ^? on ! same level b remote f ! supply4 ,artificial res]voirs are usually con/ruct$ on ! ne> outskirts ( a t[n 9 ord] t ! frictional =ce lo/ 9 transmission may be r$uc$ to a m9imum4 ,illu/ration3 ,,fig4 #aeb4--,! m di/ant ! f\nta91 ! weak] ! fl[4 ,9 ! case ( a natural res]voir1 su* z an elevat$ lake or /ream1 ! di/ance _c be plann$ or controll$4 ,new ,york1 = example1 w secure an abundance ( pure wat] f ! ,catskill ,m\nta9s1 b x w lose =ce 9 transmission4 ,los ,angeles is und]tak+ "o ( ! greate/ municipal projects ( ! day4 ,huge aqu$ucts are be+ built :i* w convey pure m\nta9 wat] a di/ance ( #bej miles1 & 9 quantities suffici5t to supply two million p4 ,accord+ to calculations1 ! =ce ( ! wat] w be s great t pumps w n be ne$$4 #aig4 ,:y ,wat] does n always fl[ f a ,faucet4 ,mo/ ( u h at times be5 annoy$ by ! inability to secure wat] on an upp] /ory1 because ( ! draw+ (f ( a supply on a l[] floor4 ,dur+ ! work+ h\rs ( ! day1 imm5se quantities ( wat] are drawn (f f innum]able faucets1 & h5ce ! quantity 9 ! pipes decreases consid]ably unless ! supply /ation is able to drive wat] ?r\gh ! va/ network ( pipes z fa/ z x is drawn (f4 ,build+s at a di/ance f ! res]voir suff] "u su* circum/ances1 because :ile ! dim9i%$ pressure is ord9>ily p[]ful en\gh to supply ! l[] floors1 x is frequ5tly too weak to =ce a cont9u\s /ream to high levels4 ,at night1 h[ev]1 & out ( work+ h\rs1 few faucets are op51 less wat] is drawn (f at any "o "t1 & ! intricate pipes are con/antly full ( wat] "u high pressure4 ,at su* times1 a good fl[ is obta9able ev5 on ! upp]mo/ floors4 ,9 ord] to ov]come ! disadvantage ( a decrease 9 fl[ dur+ ! day1 /&pipes 7,fig4 #aec7 are sometimes plac$ 9 v>i\s sections4 ,^! are practically small /eel res]voirs full ( wat] & connect+ ) ! city pipes4 ,dur+ ru% h\rs1 wat] passes f ^! into ! communicat+ pipes & increases ! available supply1 :ile dur+ ! night1 :5 ! faucets are turn$ (f1 wat] accumulates 9 ! /&pipe aga9/ ! next em]g5cy 7,figs4 #aea & #aed74 ,! s]vice r5d]$ by ! /&pipe is simil> to t ( ! air cu%ion discuss$ 9 ,section #ahd4 ,illu/ration3 ,,fig4 #aec4--;,a /&pipe4 #aih4 ,! ,co/ ( ,wat]4 ,9 ! gravity sy/em1 :]e an elevat$ lake or /ream s]ves z a natural res]voir1 ! co/ ( ! city's wat]works is practically limit$ to ! lay+ ( pipes4 ,b :5 ! s\rce ( ! supply is m or less on a level ) ! surr\nd+ l&1 ! co/ is great1 because ! supply = ! entire city mu/ ei!r be pump$ into an artificial res]voir1 f :i* x c be di/ribut$1 or else mu/ be driv5 directly ?r\gh ! ma9s 7,fig4 #aed74 ,illu/ration3 ,,fig4 #aed4--,wat] mu/ be got to ! h\ses by means ( pumps4 ,a gallon ( wat] weighs approximately #h4c p\nds1 & h5ce ! "w done by a pump 9 rais+ a gallon ( wat] to ! top ( an av]age h\se1 an elevation ( #ej feet1 is #h4c #ej1 or #dae foot p\nds4 ,a small manufactur+ t[n uses at lea/ #a1jjj1jjj gallons daily1 & ! "w done by a pump 9 rais+ t am\nt to an elevation ( #ej feet w\ld be #h4c #a1jjj1jjj #ej1 or #dae1jjj1jjj foot p\nds4 ,! total "w done dur+ ! day by ! pump1 or ! eng9e driv+ ! pump1 is #dae1jjj1jjj foot p\nds1 & h5ce ! "w done dur+ "o h\r w\ld be #a_/bd ( #dae1jjj1jjj1 or #ag1bia1fff foot p\nds2 ! "w done 9 "o m9ute w\ld be #a_/fj ( #ag1bia1fff1 or #bhh1aid foot p\nds1 & ! "w done ea* second w\ld be #a_/fj ( #bhh1aid1 or #dhjc foot p\nds4 ,a #a-;,h4,p4 eng9e does #eej foot p\nds ( "w ea* second1 & !re=e if ! pump is to be op]at$ by an eng9e1 ! /r5g? ( ! latt] w\ld h to be #h4g ,h4,p4 ,an #h4g-;,h4,p4 pump+ eng9e work+ at full spe$ e second ( ! day & night w\ld be able to supply ! t[n ) ! necess>y am\nt ( wat]4 ,:51 h[ev]1 we consid] ! actual height to :i* ! wat] is rais$ above ! pump+ /ation1 & ! extra pump+ :i* mu/ be done 9 ord] to balance ! frictional loss1 x is easy to und]/& t 9 actual practice a mu* m p[]ful eng9e w\ld be ne$$4 ,! l>g] ! pi/on & ! fa/] x works1 ! great] is ! quantity ( wat] rais$ at ea* /roke1 & ! /rong] mu/ be ! eng9e :i* op]ates ! pump4 ,9 _m l>ge cities !re is no "o s+le pump+ /ation f :i* supplies run to all p>ts ( ! city1 b sev]al pump+ /ations are scatt]$ ?r\gh\t ! city1 & ea* ( !m supplies a re/rict$ t]ritory4 #aii4 ,! ,bur/+ ( ,dams & ,res]voirs4 ,! con/ruction ( a safe res]voir is "o ( ! mo/ important problems ( eng9e]s4 ,9 ,octob]1 #aiaa1 a t[n 9 ,p5nsylvania 0 virtually wip$ out ( exi/5ce because ( ! bur/+ ( a dam ^: /ructure 0 ( insuffici5t /r5g? to resi/ ! /ra9 ( ! va/ quantity ( wat] held by x4 ,a simil> breakage 0 ! cause ( ! fatal ,john/[n flood 9 #ahhi1 :i* de/roy$ no less ?an sev5 t[ns1 & 9 :i* approximately #bjjj p]sons are said to h lo/ _! lives4 ,wat] presses n only on ! bottom ( a vessel1 b ^u ! sides z well2 a bucket leaks :e!r ! hole is 9 its side or its bottom1 %[+ t wat] presses n only d[nw>d b outw>d4 ,usually a leak 9 a dam or res]voir occurs ne> ! bottom4 ,weak spots at ! top are r>e & easily repair$1 b a leak ne> ! bottom is usually fatal1 & 9 ! case ( a l>ge res]voir ! outfl[+ wat] c>ries dea? & de/ruction to ev]y?+ 9 its pa?4 ,if ! leak is ne> ! surface1 z at a 7,fig4 #aee71 ! wat] issues z a feeble /ream1 because ! pressure aga9/ ! sides at t level is due solely to ! relatively small height ( wat] above a 7,section #aie74 ,if ! leak is l[]1 z at b1 ! issu+ /ream is /rong] & swift]1 because at t level ! outw>d pressure is mu* great] ?an at a1 ! increase be+ due to ! fact t ! height ( ! wat] above b is great] ?an t above a4 ,if ! leak is q l[1 z at c1 ! issu+ /ream has a /ill great] spe$ & /r5g?1 & gu%es =? ) a =ce det]m9$ by ! height ( ! wat] above c4 ,illu/ration3 ,,fig4 #aee4--,! fl[ f an op5+ dep5ds ^u ! height ( wat] above ! op5+4 ,! dam at ,john/[n 0 ne>ly #a_/b mile wide1 & #dj feet high1 & s great 0 ! =ce & spe$ ( ! escap+ /ream t )9 an h\r aft] ! break _h occurr$1 ! wat] _h travel$ a di/ance ( #ah miles1 & _h de/roy$ prop]ty to ! value ( millions ( doll>s4 ,if a res]voir has a dep? ( #ajj feet1 ! pressure ex]t$ ^u ea* squ>e foot ( its floor is #fb4e #ajj1 or #fbej p\nds2 ! weight !re=e to be su/a9$ by e squ>e foot ( ! res]voir floor is some:at m ?an #c tons1 & h5ce /rong f\ndations are ess5tial4 ,! outw>d lat]al pressure at a dep? ( #be feet w\ld be only "o f\r? z great z t on ! bottom--h5ce ! /ra9 on ! sides at t dep? w\ld be relatively slight1 & a less p[]ful con/ruction w\ld suffice4 ,b at a dep? ( #ej feet ! pressure on ! sides w\ld be "o half t ( ! floor pressure1 or #a-a_/b tons4 ,at a dep? ( #ge feet1 ! pressure on ! sides w\ld be ?ree qu>t]s t on ! bottom1 or #b-a_/d tons4 ,z ! bottom ( ! res]voir is approa*$1 ! pressure aga9/ ! sides increases1 & m p[]ful con/ruction becomes necess>y4 ,small elevat$ tanks1 l ^? ( ! w9dmill1 frequ5tly h heavy iron b&s ar\nd _! l[] portion z a protection aga9/ ! extra /ra94 ,be=e erect+ a dam or res]voir1 ! maximum pressure to be ex]t$ ^u e squ>e in* ( surface %\ld be accurately calculat$1 & ! /ructure %\ld !n be built 9 su* a way t ! v>y+ pressure ( ! wat] c be su/a9$4 ,x is n suffici5t t ! bottom be /rong2 ! sides likewise mu/ support _! /ra91 & h5ce mu/ be increas$ 9 /r5g? ) dep?4 ,?is /r5g!n+ ( ! walls is se5 cle>ly 9 ! res]voir %[n 9 ,figure #aeb4 ,! bur/+ ( dams & res]voirs has occasion$ ! loss ( s _m lives1 & ! de/ruction ( s mu* prop]ty1 t "s /ates are consid]+ ! advisability ( f$]al inspection ( all su* /ructures4 ,illu/ration3 ,,fig4 #aef4--,! lock gates mu/ be /rong 9 ord] to )/& ! great pressure ( ! wat] aga9/ !m4 #bjj4 ,! ,relation ( ,=e/s to ! ,wat] ,supply4 ,:5 heavy ra9s fall on a b>e slope1 or :5 sn[ melts on a b>r5 hillside1 a small am\nt ( ! wat] s9ks into ! gr\nd1 b by f> ! great] "p ( x runs (f quickly & swells brooks & /reams1 ?us caus+ floods & fre%ets4 ,:51 h[ev]1 ra9 falls on a wood$ slope1 ! action is rev]s$2 a small portion runs (f1 :ile ! great] portion s9ks into ! s(t e>?4 ,?is is due p>tly to ! fact t ! roots ( trees by _! con/ant gr[? keep ! soil loose & op51 & =m *annels1 z x 71 along :i* ! wat] c easily run4 ,x is due also to ! pres5ce on ! gr\nd ( decay+ leaves & twigs1 or humus4 ,! decay+ vegetable matt] :i* cov]s ! =e/ floor acts m or less z a sponge1 & quickly absorbs fall+ ra9 & melt+ sn[4 ,! wat] :i* ?us passes into ! humus & ! soil b5ea? does n rema9 !re1 b sl[ly seeps d[nw>d1 & f9ally aft] weeks & mon?s em]ges at a l[] level z a /ream4 ,brooks & spr+s =m$ 9 ?is way are con/ant fe$]s ( riv]s & lakes4 ,9 regions :]e ! l& has be5 de=e/$1 ! riv]s run l[ 9 season ( prolong$ dr\ght1 because ! wat] :i* %\ld h sl[ly seep$ ?r\gh ! soil1 & !n suppli$ ! riv]s = weeks & mon?s1 ran (f f ! b>r5 slopes 9 a few days4 ,=e/s n only less5 ! dang] ( floods1 b !y cons]ve our wat]ways1 prev5t+ a dang]\s high-wat] m>k 9 ! season ( heavy ra9s & melt+ sn[s1 & !n prev5t+ a %r9kage 9 dry seasons :5 ! only fe$]s ( ! riv]s are ! und]gr\nd s\rces4 ,9 ! summ] ( #aiaa1 prolong$ dr\ght 9 ,nor? ,c>ol9a l[]$ ! riv]s to su* an ext5t t t[ns dep5d5t ^u !m suff]$ greatly4 ,! city ( ,*>lotte 0 r$uc$ = a "t to a practically empty res]voir2 wa%+ & ba?+ 7 elim9at$1 ma*9]y dep5d5t ^u wat]-p[] & /eam /ood idle1 & e glass ( wat] drunk 0 c>efully reckon$4 ,?\s&s ( gallons ( wat] 7 br\ght 9 tanks f neighbor+ cities1 & 7 empti$ into ! empty res]voir f :5ce x trickl$ sl[ly ?r\gh ! city ma9s4 ,! lack ( wat] caus$ n only p]sonal inconv5i5ce & bus9ess p>alysis1 b x occasion$ real dang] ( disease ?r\gh unflu%$ sew]s & insuffici5tly dra9$ pipes4 ,! cons]vation ( ! =e/ means ! cons]vation ( our wat]ways1 :e!r ^! be us$ = transportation or z s\rces ( dr9k+ wat]4 ,,*apt] ,,xx ,,man',s ,,conque/ ,,( ,,sub/ances #bja4 ,*emi/ry4 ,man's me*anical inv5tions h be5 equal$ by 8 *emical rese>*es & discov]ies1 & by ! application he has made ( 8 new k4 ,! pla9 cotton frock ( our gr&mo!rs _h its dea? knell s\nd$ a few ye>s ago1 :5 ,john ,m]c] %[$ t cotton fabrics soak$ 9 cau/ic soda assum$ "u c]ta9 conditions a silky %e51 & :5 dy$ took on beautiful & v>i$ hues4 ,! demon/ration ( ?is simple fact laid ! f\ndation = ! manufacture ( a va/ v>iety ( attractive dress mat]ials kn[n z m]c]iz$ cotton4 ,possibly no indu/ry has be5 m affect$ by *emical discov]y ?an t ( dye+4 ,^? ( u :o h se5 ! old ma/]pieces 9 pa9t+1 or reproductions ( !m1 "k ! s(tness1 ! mell[ness1 ! ri*ness ( t9ts employ$ by ! old ma/]s4 ,b if we look = ! brilliancy & v>iety ( color se5 9 our own day1 ! se>* w be fruitless1 because ^! 7 unkn[n until a half c5tury ago4 ,up to t "t1 dyes 7 few 9 numb] & 7 extract$ solely f plants1 pr9cipally f ! indigo & madd] plants4 ,b ab\t ! ye> #ahef x 0 discov]$ t dyes 9 mu* great] v>iety & 9 pur] =m c\ld be obta9$ f coal t>4 ,?is *emical production ( dyes has n[ l>gely supplant$ ! orig9al me?od1 & ! indu/ry has gr[n s rapidly t a s+le firm produc$ 9 "o ye> f coal t> a quantity ( indigo dye :i* "u ! natural process ( plant extraction w\ld h requir$ a qu>t] million acres ( indigo plant4 ,! abundance & *eapness ( newspap]s1 co>se wrapp+ pap]s1 etc41 is due to ! fact t man has le>n$ to sub/itute wood = rags 9 ! manufacture ( pap]4 ,inve/igation br\ght out ! fact t wood conta9$ ! sub/ance :i* made rags valuable = pap] mak+4 ,s9ce ! supply ( rags 0 f> less ?an ! dem&1 ! problem ( ! extraction f wood ( ! pap]-=m+ sub/ance 0 a vital "o4 ,f repeat$ trials1 x 0 f\nd t cau/ic soda :5 heat$ ) wood *ips de/roy$ ev]y?+ 9 ! wood except ! desir$ sub/ance1 cellulose2 ?is c\ld be remov$1 blea*$1 dri$1 & press$ into pap]4 ,! sub/itution ( wood = rags has made possible ! daily issue ( newspap]s1 = ! mak+ ( :i* suffici5t mat]ial w\ld n o!rwise h be5 available4 ,:5 we reflect t a daily pap] ( wide circulation consumes t5 acres ( wood lot p] day1 we see t all ! rags 9 ! _w w\ld be inadequate to meet ?is dem& alone1 to say no?+ ( p]iodicals1 books1 tissue pap]1 etc4 ,*emi/ry plays a "p 9 e phase ( life2 9 ! arts1 ! indu/ries1 ! h\sehold1 & 9 ! body itself1 :]e dige/ion1 excretion1 etc41 result f ! action ( ! bodily fluids ^u food4 ,! *emical sub/ances ( mo/ int]e/ to u are ^? :i* affect u p]sonally r ?an indu/rially2 = example1 soap1 :i* cleanses our bodies1 our clo?+1 our h\sehold possessions2 wa%+ soda1 :i* light5s laundry "w2 lye1 :i* cle>s out ! dra9 pipe clogg$ ) grease2 b5z9e1 :i* removes /a9s f clo?+2 turp5t9e1 :i* rids u ( pa9t spots left by c>eless workm52 & hydrog5 p]oxide1 :i* dis9fects w\nds & sores4 ,9 ord] to und]/& ! action ( sev]al ( ^! sub/ances we mu/ /udy ! prop]ties ( two gr\ps ( *emicals--kn[n respectively z acids & bases2 ! fir/ ( ^! may be repres5t$ by v9eg>1 sulphuric acid1 & oxalic acid2 & ! second1 by ammonia1 lye1 & limewat]4 #bjb4 ,acids4 ,all ( u "k t v9eg> & lemon juice h a s\r ta/e1 & x is easy to %[ t mo/ acids are *>act]iz$ by a s\r ta/e4 ,if a clean glass rod is dipp$ into v dilute acid1 su* z acetic1 sulphuric1 or nitric acid1 & !n lightly t\*$ to ! tongue1 x w ta/e s\r4 ,b ! be/ te/ ( an acid is by sight r ?an by ta/e1 because x has be5 f\nd t an acid is able to discolor a plant sub/ance call$ litmus4 ,if pap] is soak$ 9 a litmus solution until x acquires ! *>act]i/ic blue hue ( ! plant sub/ance1 & is !n dri$ ?or\ghly1 x c be us$ to detect acids1 because if x comes 9 contact ) ev5 ! m9ute/ trace ( acid1 x loses its blue color & assumes a r$ t9t4 ,h5ce1 9 ord] to detect ! pres5ce ( acid 9 a sub/ance1 "o has m]ely to put "s ( ! sub/ance on blue litmus pap]1 & note :e!r or n ! latt] *anges color4 ,?is te/ %[s t _m ( our common foods conta9 "s acid2 = example1 fruit1 butt]milk1 s\r bread1 & v9eg>4 ,! damage :i* c be done by /rong acids is well kn[n2 if a j> ( sulphuric acid is ov]turn$1 & "s ( x falls on ! sk91 x eats its way into ! fle% & leaves an ugly sore2 if x falls on c>pet or coat1 x eats its way into ! mat]ial & leaves an unsightly hole4 ,! evil results ( an accid5t ) acid c be less5$ if we "k j :at to d & d x quickly1 b = ?is we mu/ h a k ( bases1 ! second gr\p ( *emicals4 #bjc4 ,bases4 ,sub/ances belong+ to ?is gr\p usually h a bitt] ta/e & a slimy1 soapy feel+4 ,= our pres5t purposes1 ! mo/ important *>act]i/ic ( a base is t x w neutralize an acid & 9 "s measure h9d] ! damage effect$ by ! =m]4 ,if1 z soon z an acid has be5 spill$ on clo?1 a base1 su* z ammonia1 is appli$ to ! affect$ region1 b little h>m w be done4 ,9 y\r laboratory exp]im5ts y may be un=tunate en\gh to spill acid on y\r body or clo?+2 if s1 quickly apply ammonia4 ,if y delay1 ! acid does its "w1 & !re is no rem$y4 ,if soda 7a base7 t\*es black mat]ial1 x discolors x & leaves an ugly br[n spot2 b ! application ( a little acid1 su* z v9eg> or lemon juice1 w (t5 re/ore ! orig9al color & c\nt]act ! bad effects ( ! base4 ,limewat] prescrib$ by physicians 9 cases ( illness is a well-kn[n base4 ,?is liquid neutralizes ! too abundant acids pres5t 9 a weak sy/em & s quiets & tones ! /oma*4 ,! int]action ( acids & bases may be obs]v$ 9 ano!r way4 ,if blue litmus pap] is put into an acid solution1 its color *anges to r$2 if n[ ! r$ litmus pap] is dipp$ into a base solution1 cau/ic soda1 = example1 its orig9al color is p>tially re/or$4 ,:at ! acid does1 ! base undoes1 ei!r :olly or 9 "p4 ,bases always turn r$ litmus pap] blue4 ,bases1 l acids1 are good or bad accord+ to _! use2 if !y come 9 contact ) clo?1 !y eat or discolor x1 unless neutraliz$ by an acid4 ,b ?is prop]ty ( bases1 h>mful 9 "o way1 is put to advantage 9 ! home1 :]e grease is remov$ f dra9pipe & s9k by ! application ( lye1 a /rong base4 ,if ! lye is too conc5trat$1 x w n only eat ! grease1 b w corrode ! metal pip+2 x is easy1 h[ev]1 to dilute base solutions to su* a degree t !y w n affect pip+1 b w remove grease4 ,dilute ammonia is us$ 9 almo/ e home & is an indisp5sable dome/ic s]vant2 dilut$ suffici5tly1 x is invaluable 9 ! wa%+ ( delicate fabrics & 9 ! remov+ ( /a9s1 & 9 a m conc5trat$ =m x is helpful z a smell+ salt 9 cases ( fa9t+4 ,"s conc5trat$ bases are s p[]ful 9 _! action on grease1 clo?1 & metal t !y h receiv$ ! designation cau/ic1 & are ord9>ily kn[n z cau/ic soda1 cau/ic pota% 7lye71 & cau/ic lime4 ,^! m active bases are g5]ally call$ alkalies 9 di/9ction f ! less active ones4 #bjd4 ,neutral ,sub/ances4 ,to any acid solution add gradually a small quantity ( a base1 & te/ ! mixture f "t to "t ) blue litmus pap]2 at fir/ ! pap] w turn r$ quickly1 b z m & m ( ! base is add$ to ! solution1 x has less & less effect on ! blue litmus pap]1 & f9ally a po9t is rea*$ :5 a fre% /rip ( blue pap] w n be affect$4 ,su* a result indicates infallibly ! abs5ce ( any acid qualities 9 ! solution4 ,if n[ r$ litmus pap] is te/$ 9 ! same solution1 its color also w rema9 un*ang$2 su* a result indicates infallibly ! abs5ce ( any basic quality4 ,! solution has ! *>act]i/ic prop]ty ( nei!r acid nor base & is said to be neutral4 ,if to ! neutral solution an extra portion ( base is add$1 s t !re is an excess ( base ov] acid1 ! neutralization is ov]balanc$ & ! r$ pap] turns blue4 ,if to ! neutral solution an extra portion ( acid is add$1 s t !re is an excess ( acid ov] base1 ! neutralization is ov]balanc$ 9 ! opposite direction1 & ! solution acquires acid *>act]i/ics4 ,mo/ acids & bases w eat & corrode & discolor1 :ile neutral sub/ances w n2 x is = ?is reason t soap1 a slightly alkal9e sub/ance1 is ! safe/ cleans+ ag5t = laundry1 ba?1 & g5]al "w4 ,good soaps1 be+ c>efully made1 are s ne>ly neutral t !y w n fade ! color out ( clo?+2 ! *eap soaps are less c>efully prep>$ & are apt to h a /rong excess ( ! base +r$i5t2 su* soaps are n safe = delicate "w4 #bje4 ,soap4 ,if we ga!r toge!r scrap+s ( l>d1 butt]1 bits ( tall[ f burn$-out c&les1 scraps ( wa/e fat1 or any o!r sort ( grease1 & p\r a /rong solution ( lye ov] ! mass1 a s(t soapy sub/ance is =m$4 ,9 colonial times1 e family made its own supply ( soap1 utiliz+1 = t purpose1 h\sehold scraps (t5 reg>d$ by ! h\sekeep] ( to-day z wor?less4 ,grease & fat 7 boil$ ) wat] & h>dwood a%es1 :i* are ri* 9 lye1 & f ! mixture came ! s(t soap us$ by our ance/ors4 ,9 practice1 ! wood a%es 7 boil$ 9 wat]1 :i* 0 !n /ra9$ (f1 & ! result+ filtrate1 or lye1 0 mix$ ) ! fats = soap mak+4 ,mo/ fats conta9 a sub/ance ( an acid nature1 & are decompos$ by ! action ( bases su* z cau/ic soda & cau/ic pota%4 ,! acid compon5t ( ! grease p>tially neutralizes ! base1 & a new sub/ance is =m$1 namely1 soap4 ,) ! advance ( civilization ! labor ( soap mak+ pass$ f ! home to ! factory1 v mu* z bread mak+ has done 9 our own day4 ,diff]5t v>ieties ( soaps appe>$1 ( :i* ! h>d soap 0 ! mo/ popul>1 ow+ to ! ease ) :i* x c\ld be transport$4 ,)9 ! la/ few ye>s liquid soaps h come into favor1 especially 9 s*ools1 railroad /ations1 & o!r public places1 :]e a cake ( soap w\ld be h&l$ by _m p]sons4 ,by means ( a simple device 7,fig4 #aeg71 ! soap escapes f a receptacle :5 ne$$4 ,! mass ( ! soap does n come 9 contact ) ! sk91 & h5ce ! spread ( contagi\s sk9 diseases is less5$4 ,illu/ration3 ,,fig4 #aeg4--,liquid soap conta9]4 ,comm]cial soaps are made f a great v>iety ( sub/ances1 su* z tall[1 l>d1 ca/or oil1 coconut oil1 olive oil1 etc42 or 9 *eap] soaps1 f ros91 cottonse$ oil1 & wa/e grease4 ,! fats :i* g to wa/e 9 our g>bage c\ld be made a s\rce ( income1 n only to ! h\sewife1 b to ! city4 ,9 ,columbus1 ,ohio1 g>bage is us$ z a s\rce ( rev5ue2 ! grease f ! g>bage be+ sold = soap mak+1 & ! tankage 7,section #ahh7 = f]tiliz]4 #bjf4 ,:y ,soap ,cleans4 ,! natural oil ( ! sk9 cat*es & reta9s du/ & dirt1 & makes a greasy film ov] ! body4 ,?is _c be remov$ by wat] alone1 b if soap is us$ & a g5]\s la!r is appli$ to ! sk91 ! dirt is cut & passes f ! body into ! wat]4 ,soap affects a grease film & wat] v mu* z ! :ite ( an egg affects oil & wat]4 ,^! two liquids alone d n mix1 ! oil rema9+ sep>ate on ! surface ( ! wat]2 b if a small quantity ( :ite ( egg is add$1 an emulsion is =m$1 ! oil sep>at+ into m9ute droplets :i* spread ?r\gh ! wat]4 ,9 ! same way1 soap acts on a grease film1 sep>at+ x into m9ute droplets :i* leave ! sk9 & spread ?r\gh ! wat]1 c>ry+ ) !m ! du/ & dirt p>ticles4 ,! w>m] ! wat]1 ! bett] w be ! emulsion1 & h5ce ! m effective ! removal ( dirt & grease4 ,?is explanation holds true = ! removal ( grease f any surface1 :e!r ( ! body1 clo?+1 furniture1 or di%es4 #bjg4 ,wa%+ ,p[d]s4 ,sometimes soap refuses to =m a la!r & in/ead cakes & floats z a scum on ! top ( ! wat]2 ?is is n ! fault ( ! soap b ( ! wat]4 ,z wat] seeps ?r\gh ! soil or fl[s ov] ! l&1 x absorbs & reta9s v>i\s soil con/itu5ts :i* modify its "* &1 9 "s cases1 r5d] x almo/ useless = h\sehold purposes4 ,mo/ ( u are famili> ) ! ra9 b>rel ( ! c\ntry h\se1 & "k t ! h\sewife pref]s ra9 wat] = laundry & g5]al "w4 ,ra9 wat]1 com+ z x does f ! cl\ds1 is free f ! *emicals ga!r$ by gr\nd wat]1 & is h5ce practically pure4 ,:ile =eign sub/ances d n necess>ily injure wat] = dr9k+ purposes 7,section #fi71 !y are (t5 ( su* a nature z to prev5t soap f =m+ an emulsion1 & h5ce f do+ its "w4 ,"u su* circum/ances ! wat] is said to be h>d1 & soap us$ ) x is wa/$4 ,ev5 if wat] is only mod]ately h>d1 mu* soap is lo/4 ,! sub/ances :i* make wat] h>d are calcium & magnesium salts4 ,:5 soap is put into wat] conta9+ "o or bo? ( ^!1 x comb9es ) ! salts to =m /icky insoluble scum4 ,x is !re=e n free to =m an emulsion & to remove grease4 ,z a cleans+ ag5t x is valueless4 ,! av]age city supply conta9s s little h>dness t x is satisfactory = toilet purposes2 b 9 ! laundry1 :]e !re is ne$ = ! full effect ( ! soap1 & :]e ! slighte/ loss w\ld aggregate a great deal 9 ! c\rse ( "t1 some?+ mu/ be done to c\nt]act ! h>dness4 ,! addition ( soda1 or sodium c>bonate to ! wat] w usually produce ! desir$ effect4 ,wa%+ soda comb9es ) calcium & magnesium & prev5ts !m f unit+ ) soap4 ,! soap is ?us free to =m an emulsion1 j z 9 ord9>y wat]4 ,wa%+ p[d]s are sometimes us$ in/ead ( wa%+ soda4 ,mo/ wa%+ p[d]s conta91 9 addition to a s(t5+ ag5t1 "s alkali1 & h5ce a d\ble good is obta9$ f _! use2 !y n only s(t5 ! wat] & all[ ! soap to =m an emulsion1 b !y also1 ?r\gh _! alkali cont5t1 cut ! grease & !mselves act z cleans]s4 ,9 "s cities :]e ! wat] is v h>d1 z 9 ,columbus1 ,ohio1 x is s(t5$ & filt]$ at public exp5se1 be=e x leaves ! res]voirs4 ,b ev5 "u ^! circum/ances1 a mod]ate use ( wa%+ p[d] is g5]al 9 laundry "w4 ,if wa%+ p[d] is put on clo!s dry1 or is ?r[n into a cr[d$ tub1 x w eat ! clo!s be=e x has a *ance to dissolve 9 ! wat]4 ,! only safe me?od is to dissolve ! p[d] be=e ! clo!s are put into ! tub4 ,! tr\ble ) our public laundries is t _m ( !m are c>eless ab\t ?is v fact1 & d n take "t to dissolve ! p[d] be=e mix+ x ) ! clo!s4 ,! /ronge/ wa%+ p[d] is soda1 & ?is *eap =m is z good z any ( ! m exp5sive prep>ations sold "u fancy names4 ,borax is a mild] p[d] & is desirable = f9] "w4 ,"o ( ! mo/ disagreeable consequ5ces ( ! use ( h>d wat] = ba?+ is ! unavoidable scum :i* =ms on ! sides ( ba?tub & wa%b[l4 ,! removal ( ! cak$ grease is difficult1 & if soap alone is us$1 ! clean+ ( ! tub requires bo? pati5ce & h>d scrubb+4 ,! labor c be greatly less5$ by moi/5+ ! scrubb+ clo? ) turp5t9e & apply+ x to ! greasy film1 :i* imm$iately dissolves & ?us c be easily remov$4 ,! pres5ce ( ! scum c be l>gely avoid$ by add+ a small am\nt ( liquid ammonia to ! ba? wat]4 ,b _m p]sons object to ?is2 h5ce x is well to h "s o!r easy me?od ( remov+ ! objectionable matt]4 #bjh4 ,to remove ,/a9s f ,clo?4 ,:ile soap is1 g5]ally speak+1 ! be/ cleans+ ag5t1 !re are occasions :5 o!r sub/ances c be us$ to bett] advantage4 ,= example1 grease spots on c>pet & non-wa%able dress goods are be/ remov$ by ! application ( gasol9e or b5z9e4 ,^! sub/ances dissolve ! grease1 b d n remove x f ! clo?+2 = t purpose a wool5 clo? %\ld be laid "u ! /a9 9 read9ess to absorb ! b5z9e & ! grease dissolv$ 9 x4 ,if ! grease is n absorb$ :ile 9 solution1 x rema9s 9 ! clo?+ & aft] ! evaporation ( ! b5z9e reappe>s 9 full =ce4 ,clean]s frequ5tly clean suits by lay+ a blott] ov] a grease spot & apply+ a hot iron2 ! grease1 :5 melt$ by ! heat1 takes ! easie/ way ( spread+ itself & passes f clo? to blott]4 #bji4 ,salts4 ,a neutral liquid =m$ z 9 ,section #bjd1 by ! action ( hydro*loric acid & ! alkali solution ( cau/ic soda1 has a bracki%1 salty ta/e1 & is1 9 fact1 a solution ( salt4 ,?is c be demon/rat$ by evaporat+ ! neutral liquid to dryness & exam9+ ! residue ( solid matt]1 :i* proves to be common salt4 ,:5 an acid is mix$ ) a base1 ! result is a sub/ance m or less simil> 9 its prop]ties to common salt2 = ?is reason all comp\nds =m$ by ! neutralization ( an acid ) a base are call$ salts4 ,if1 in/ead ( hydro*loric acid 7,h,cl71 we use an acid solution ( potassium t>trate1 & if in/ead ( cau/ic soda we use bic>bonate ( soda 7bak+ soda71 ! result is a bracki% liquid z be=e1 b ! salt 9 ! liquid is n common salt1 b ,ro*elle salt4 ,diff]5t comb9ations ( acids & bases produce diff]5t salts4 ,( all ! va/ gr\p ( salts1 ! mo/ abundant z well z ! mo/ important is common salt1 kn[n te*nically z sodium *loride because ( its two con/itu5ts1 sodium & *lor9e4 ,we are n dep5d5t ^u neutralization = ! enorm\s quantities ( salt us$ 9 ! home & 9 comm]ce4 ,x is f ! active1 re/less seas ( ! pres5t1 & f ! dead seas ( ! prehi/oric pa/ t our va/ /ores ( salt come4 ,! wat]s ( ! ,m$it]ranean & ( our own ,great ,salt ,lake are l$ into %all[ bas9s1 :]e1 aft] evaporation by ! heat ( ! sun1 !y leave a residue ( salt4 ,by f> ! l>ge/ quantity ( salt1 h[ev]1 comes f ! seas :i* no long] exi/1 b :i* 9 f> remote ages dri$ up & left beh9d !m _! burd5 ( salt4 ,deposits ( salt =m$ 9 ?is way are f\nd scatt]$ ?r\gh\t ! _w1 & 9 our own c\ntry are f\nd 9 greate/ abundance 9 ,new ,york4 ,! l>ge/ salt deposit kn[n has a dep? ( "o mile & exi/s 9 ,g]many4 ,salt is indisp5sable on our table & 9 our kit*51 b ! am\nt ( salt us$ 9 ?is way is f> too small to acc\nt = a ye>ly consumption ( #d1jjj1jjj tons 9 ! ,unit$ ,/ates alone4 ,! manufacture ( soap1 glass1 blea*+ p[d]s1 bak+ p[d]s1 wa%+ soda1 & o!r *emicals dep5ds on salt1 & x is = ^! t ! salt b$s are m9$4 #baj4 ,bak+ ,soda4 ,salt is by all odds ! mo/ important sodium comp\nd4 ,next to x come ! s-call$ c>bonates3 fir/1 sodium c>bonate1 :i* is already famili> to u z wa%+ soda2 & second1 sodium bic>bonate1 :i* is an +r$i5t ( bak+ p[d]s4 ,^! are bo? obta9$ f sodium *loride by relatively simple means2 t is1 by treat+ salt ) ! base1 ammonia1 & ) c>bon dioxide4 ,wa%+ soda has already be5 discuss$4 ,s9ce bak+ p[d]s 9 "s =m are us$ 9 almo/ all homes = ! rais+ ( cake & pa/ry d\gh1 x is ess5tial t _! helpful & h>mful qualities be cle>ly und]/ood4 ,! rais+ ( d\gh by means ( bak+ soda--bic>bonate ( soda--is a v simple process4 ,:5 soda is heat$1 x gives (f c>bon dioxide gas2 y c easily prove ?is = y\rself by burn+ a little soda 9 a te/ tube1 & te/+ ! escap+ gas 9 a te/ tube ( limewat]4 ,:5 fl\r & wat] alone are knead$ & bak$ 9 loaves1 ! result is a mass s compact & h>d t human tee? are almo/ p[]less to cru% & *ew x4 ,! problem is to sep>ate ! mass ( d\gh or1 9 o!r words1 to cause x to rise & light54 ,?is c be done by mix+ a little soda 9 ! fl\r1 because ! heat ( ! ov5 causes ! soda to give (f bubbles ( gas1 & ^! 9 exp&+ make ! heavy mass slightly por\s4 ,bread is nev] light5$ ) soda because ! am\nt ( gas ?us giv5 (f is too small to conv]t heavy compact bread d\gh into a spongy mass2 b biscuit & cake1 be+ by nature less compact & heavy1 are suffici5tly light5$ by ! gas giv5 (f f soda4 ,b !re is "o great objection to ! use ( soda alone z a leav5+ ag5t4 ,aft] bak+ soda has lo/ its c>bon dioxide gas1 x is no long] bak+ soda1 b is trans=m$ into its relative1 wa%+ soda1 :i* has a disagreeable ta/e & is by no means desirable = ! /oma*4 ,man's k ( *emicals & _! effect on ea* o!r has enabl$ him to ov]come ?is difficulty &1 at ! same "t1 to reta9 ! leav5+ effect ( ! bak+ soda4 #baa4 ,bak+ ,p[d]s4 ,if "s cook+ soda is put into lemon juice or v9eg>1 or any acid1 bubbles ( gas imm$iately =m & escape f ! liquid4 ,aft] ! eff]vesc5ce has ceas$1 a ta/e ( ! liquid w %[ y t ! lemon juice has lo/ its acid nature1 & has acquir$ 9 ex*ange a salty ta/e4 ,bak+ soda1 :5 treat$ ) an acid1 is trans=m$ into c>bon dioxide & a salt4 ,! v>i\s bak+ p[d]s on ! m>ket to-day consi/ ( bak+ soda & "s acid sub/ance1 :i* acts ^u ! soda1 =ces x to give up its gas1 & at ! same "t unites ) ! residue to =m a h>mless salt4 ,cream ( t>t> conta9s suffici5t acid to act on bak+ soda1 & is a conv5i5t & safe +r$i5t = bak+ p[d]4 ,:5 soda & cream ( t>t> are mix$ dry1 !y d n react on ea* o!r1 nei!r d !y comb9e rapidly 9 cold moi/ d\gh1 b z soon z ! heat ( ! ov5 p5etrates ! d\ghy mass1 ! cream ( t>t> comb9es ) ! soda & sets free ! gas ne$$ to raise ! d\gh4 ,! gas exp&s ) ! heat ( ! ov51 rais+ ! d\gh /ill m4 ,mean:ile1 ! d\gh itself is influ5c$ by ! heat & is /iff5$ to su* an ext5t t x reta9s its inflat$ %ape & spongy nature4 ,_m h\sewives look askance at ready-made bak+ p[d]s & pref] to bake ) soda & s\r milk1 soda & butt]milk1 or soda & cream ( t>t>4 ,s\r milk & butt]milk are q z good z cream ( t>t>1 because ! lactic acid :i* !y conta9 comb9es ) ! soda & lib]ates c>bon dioxide1 & =ms a h>mless residue 9 ! d\gh4 ,! desire ( manufactur]s to produce *eap bak+ p[d]s l$ to ! use ( *eap acids & alkalies1 reg>dless ( ! "* ( ! result+ salt4 ,alum & soda 7 popul> = "s "t2 b c>eful exam9ation prov$ t ! p>ticul> salt produc$ by ?is comb9ation 0 n readily absorb$ by ! /oma*1 & t its ret5tion !re 0 injuri\s to heal?4 ,= ?is reason1 _m /ates h prohibit$ ! use ( alum 9 bak+ p[d]s4 ,x is n only important to *oose ! +r$i5ts c>efully2 x is also necess>y to calculate ! respective quantities ( ea*1 o!rwise !re w be an excess ( acid or alkali = ! /oma* to take c>e (4 ,a /&>d p[d] conta9s twice z mu* cream ( t>t> z ( bic>bonate ( soda1 & ! ?rifty h\sewife :o wi%es to economize1 c make = h]self1 at small co/1 z good a bak+ p[d] z any on ! m>ket1 by mix+ t>t> & soda 9 ! above proportions & add+ a little corn />* to keep ! mixture dry4 ,! self-rais+ fl\r1 s widely adv]tis$ by groc]s1 is fl\r 9 :i* ^! +r$i5ts or _! equival5t h be5 mix$ by ! manufactur]4 #bab4 ,soda ,m9ts4 ,bic>bonate ( soda is practically ! sole +r$i5t ( ! soda m9ts popul>ly sold = indige/ion4 ,^! correct a t5d5cy to s\r /oma* because !y c\nt]act ! surplus acid 9 ! /oma*1 & =m ) x a safe neutral sub/ance4 ,seidlitz p[d] is a simple rem$y consi/+ ( two p[d]s1 "o conta9+ bic>bonate ( soda1 & ! o!r1 "s acid su* z cream ( t>t>4 ,:5 ^! sub/ances are dissolv$ 9 wat] & mix$1 eff]vesc5ce occurs1 c>bon dioxide escapes1 & a solution ( ,ro*elle salt rema9s4 #bab;a4 ,s\rce ( ,soda4 ,an enorm\s quantity ( sodium c>bonate1 or soda1 z x is usually call$1 is ne$$ 9 ! manufacture ( glass1 soap1 blea*+ p[d]s1 & o!r comm]cial products4 ,=m]ly1 ! supply ( soda 0 v limit$ because man 0 dep5d5t ^u natural deposits & ^u a%es ( sea plants = x4 ,common salt1 sodium *loride1 is abundant1 & 9 #agge a prize 0 (f]$ to any "o :o w\ld f9d a way to obta9 soda f salt4 ,z a result ( ?is1 soda 0 soon manufactur$ f common salt4 ,9 ! mo/ rec5t me?ods ( manufacture1 salt1 wat]1 ammonia1 & c>bon dioxide are made to react4 ,bak+ soda is =m$ f ! reaction4 ,! bak+ soda is !n heat$ & decompos$ into wa%+ soda or ! soda ( comm]ce4 ,,*apt] ,,xxi ,,f]m5tation #bac4 ,:ile bak+ p[d] is univ]sally us$ = biscuits & cake1 x is seldom1 if ev]1 us$ = bread1 because x does n furni% suffici5t gas to light5 ! t\gh heavy mass ( bread d\gh4 ,!n1 too1 mo/ p pref] ! ta/e ( yea/-rais$ bread4 ,!re is a reason = ?is widespread pref]5ce1 b to und]/& x1 we mu/ g some:at f> afield1 & mu/ /udy n only ! bread ( to-day1 b ! bread ( antiquity1 & ! w9es z well4 ,if grapes are cru%$1 !y yield a liquid :i* ta/es l ! grapes2 b if ! liquid is all[$ to /& 9 a w>m place1 x loses its orig9al "*1 & beg9s to f]m5t1 becom+1 9 ! c\rse ( a few weeks1 a /rongly intoxicat+ dr9k4 ,?is is true n only ( grape juice b also ( ! juice ( all o!r sweet fruits2 apple juice f]m5ts to cid]1 currant juice to currant w9e1 etc4 ,?is ph5om5on ( f]m5tation is kn[n to practically all races ( m51 & !re is sc>cely a savage tribe )\t "s k9d ( f]m5t$ dr9k2 9 ! tropics ! f]m5t$ juice ( ! palm tree s]ves = w9e2 9 ! des]t regions1 ! f]m5t$ juice ( ! c5tury plant2 & 9 /ill o!r regions1 ! root ( ! g+] plant is press$ into s]vice4 ,! f]m5tation :i* occurs 9 bread mak+ is simil> to t :i* is responsible = ! trans=mation ( plant juices into intoxicat+ dr9ks4 ,! =m] process is n s old1 h[ev]1 s9ce ! use ( alcoholic bev]ages dates back to ! v dawn ( hi/ory1 & ! au!ntic record ( rais$ or leav5$ bread is b little m ?an #cjjj ye>s old4 #bad4 ,! ,bread ( ,antiquity4 ,! orig9al me?od ( bread mak+ & ! me?od employ$ by savage tribes ( to-day is to mix cru%$ gra9 & wat] until a pa/e is =m$1 & !n to bake ?is ov] a camp fire4 ,! result is a h>d compact sub/ance kn[n z unleav5$ bread4 ,a consid]able improvem5t ov] ?is ta/eless mass is self-rais$ bread4 ,if d\gh is left /&+ 9 a w>m place a numb] ( h\rs1 x swells up ) gas & becomes por\s1 & :5 bak$1 is less compact & h>d ?an ! savage bread4 ,exposure to air & w>m? br+s ab\t *anges 9 d\gh z well z 9 fruit juices1 & alt]s ! "* ( ! d\gh & ! bread made f x4 ,bread made 9 ?is way w\ld n seem palatable to civiliz$ man ( ! pres5t day1 accu/om$1 z he is1 to delici\s bread made light & por\s by yea/2 b to ! anci5ts1 ! lea/ s(t5+ & light5+ 0 welcome1 & self-f]m5t$ bread1 !re=e1 supplant$ ! orig9al unleav5$ bread4 ,soon x 0 discov]$ t a p9* ( ?is f]m5t$ d\gh act$ z a />t] on a fre% bat* ( d\gh4 ,h5ce1 a little ( ! f]m5t$ d\gh 0 c>efully sav$ f a bat*1 & :5 ! next bread 0 made1 ! f]m5t$ d\gh1 or leav51 0 work$ into ! fre% d\gh & s]v$ to raise ! mass m quickly & effectively ?an m]e exposure to air & w>m? c\ld d 9 ! same l5g? ( "t4 ,?is use ( leav5 = rais+ bread has be5 practic$ = ages4 ,grape juice mix$ ) millet f]m5ts quickly & /rongly1 & ! ,romans le>n$ to use ?is mixture = bread rais+1 knead+ a v small am\nt ( x ?r\gh ! d\gh4 #bae4 ,! ,cause ( ,f]m5tation4 ,al?\gh alcoholic f]m5tation1 & ! f]m5tation :i* goes on 9 rais+ d\gh1 7 kn[n & utiliz$ = _m ye>s1 ! cause ( ! ph5om5on 0 a seal$ book until ! n9ete5? c5tury4 ,ab\t t "t x 0 discov]$1 ?r\gh ! use ( ! microscope1 t f]m5t+ liquids conta9 an army ( m9ute plant organisms :i* n only live !re1 b :i* actually gr[ & multiply )9 ! liquid4 ,= gr[? & multiplication1 food is necess>y1 & ?is ! t9y plants get 9 abundance f ! fruit juices2 !y fe$ ^u ! sug>y matt] & z !y fe$1 !y f]m5t x1 *ang+ x into c>bon dioxide & alcohol4 ,! c>bon dioxide1 9 ! =m ( small bubbles1 passes (f f ! f]m5t+ mass1 :ile ! alcohol rema9s 9 ! liquid1 giv+ ! /imulat+ effect desir$ by imbib]s ( alcoholic dr9ks4 ,! unkn[n /range organisms 7 call$ yea/1 & !y 7 ! />t+ po9t ( ! yea/ cakes & yea/ brews manufactur$ to-day on a l>ge scale1 n only = bread mak+ b = ! comm]cial production ( be]1 ale1 port]1 & o!r intoxicat+ dr9ks4 ,! gra9s1 rye1 corn1 rice1 :eat1 f :i* meal is made1 conta9 only a small quantity ( sug>1 b1 on ! o!r h&1 !y conta9 a l>ge quantity ( />* :i* is easily conv]tible into sug>4 ,^u ?is ! t9y yea/ plants 9 ! d\gh fe$1 &1 z 9 ! case ( ! w9es1 f]m5t ! sug>1 produc+ c>bon dioxide & alcohol4 ,! d\gh is ?ick & /icky & ! gas bubbles exp& x into a spongy mass4 ,! t9y yea/ plants multiply & cont9ue to make alcohol & gas1 & 9 consequ5ce1 ! d\gh becomes light] & light]4 ,:5 x has ris5 suffici5tly1 x is knead$ & plac$ 9 an ov52 ! heat ( ! ov5 soon kills ! yea/ plants & drives ! alcohol out ( ! bread2 at ! same "t x exp&s ! imprison$ gas bubbles & causes !m to light5 & swell ! bread /ill m4 ,mean:ile1 ! d\gh has become /iff en\gh to support itself4 ,! result ( ! f]m5tation is a light1 spongy loaf4 #baf4 ,:]e does ,yea/ come ,f8 ,! microscopic plants :i* we call yea/ are widely di/ribut$ 9 ! air1 & float ar\nd !re until *ance br+s !m 9 contact ) a sub/ance favorable to _! gr[?1 su* z fruit juices & moi/ w>m batt]4 ,"u ! favorable conditions ( abundant moi/ure1 heat1 & food1 !y gr[ & multiply rapidly1 & cause ! ph5om5on ( f]m5tation4 ,wild yea/ settles on ! sk9 ( grapes & apples1 b s9ce x does n h access to ! fruit juices )91 x rema9s inactive v mu* z a se$ does be=e x is plant$4 ,b :5 ! fruit is cru%$1 ! yea/ plants get into ! juice1 & fe$+ on x1 gr[ & multiply4 ,! /ray yea/ plants :i* get into ! sirup are relatively few1 & h5ce f]m5tation is sl[2 x requires sev]al weeks = currant w9e to f]m5t1 & sev]al mon?s = ! juice ( grapes to be conv]t$ into w9e4 ,/ray yea/ f9ds a favorable soil = gr[? 9 ! w>m? & moi/ure ( a batt]2 b al?\gh ! numb] ( ^! /ray plants is v l>ge1 x is insuffici5t to cause rapid f]m5tation1 & if we dep5d$ ^u wild yea/ = bread rais+1 ! result w\ld n be to our lik+4 ,:5 our remote ance/ors sav$ a p9* ( d\gh z leav5 = ! next bak+1 !y 7 actually cultivat+ yea/1 al?\gh !y did n "k x4 ,! res]v$ portion s]v$ z a favorable bre$+ place to ! yea/ plants )9 x2 !y grew & reproduc$ amaz+ly1 & became s num]\s1 t ! small mass ( old d\gh 9 :i* !y 7 ga!r$ s]v$ to leav5 ! entire bat* at ! next bak+4 ,z soon z man le>n$ t yea/ plants caus$ f]m5tation 9 liquors & bread1 he realiz$ t x w\ld be to 8 advantage to cultivate yea/ & to add x to bread & to plant juices r ?an to dep5d ^u accid5tal & sl[ f]m5tation f wild yea/4 ,%ortly aft] ! discov]y ( yea/ 9 ! n9ete5? c5tury1 man comm5c$ 8 attempt to cultivate ! t9y organisms4 ,_! microscopic size add$ greatly to 8 tr\ble1 & x 0 only aft] ye>s ( c>eful & t$i\s inve/igation t he 0 able to p]fect ! comm]cial yea/ cakes & yea/ brews univ]sally us$ by bak]s & brew]s4 ,! well-kn[n compress$ yea/ cake is simply a mass ( live & vigor\s yea/ plants1 emb$d$ 9 a s(t1 soggy mat]ial1 & ready to gr[ & multiply z soon z !y are plac$ "u prop] conditions ( heat1 moi/ure1 & food4 ,se$s :i* rema9 on our %elves d n g]m9ate1 b ^? :i* are plant$ 9 ! soil d2 s x is ) ! yea/ plants4 ,:ile 9 ! cake !y are z lifeless z ! se$2 :5 plac$ 9 d\gh1 or fruit juice1 or gra9 wat]1 !y gr[ & multiply & cause f]m5tation4 ,,*apt] ,,xxii ,,blea*+ #bag4 ,! beauty & ! comm]cial value ( uncolor$ fabrics dep5d ^u ! purity & p]fection ( _! :it5ess2 a man's :ite coll> & a woman's :ite wai/ mu/ be pure :ite1 )\t ! slighte/ t+e ( color4 ,b all natural fabrics1 :e!r !y come f plants1 l cotton & l951 or f animals1 l wool & silk1 conta9 m or less color+ matt]1 :i* impairs ! :it5ess4 ,?is color+ n only detracts f ! appe>ance ( fabrics :i* are to be worn uncolor$1 b x s]i\sly int]f]es ) ! action ( dyes1 & at times plays ! dy] /range tricks4 ,natural fib]s1 moreov]1 are difficult to sp9 & weave unless "s s(t5+ mat]ial su* z wax or res9 is rubb$ lightly ov] !m4 ,! matt] add$ to facilitate sp9n+ & weav+ g5]ally detracts f ! appe>ance ( ! uncolor$ fabric1 & also int]f]es ) successful dye+4 ,?us x is easy to see t ! natural color+ matt] & ! add$ =eign matt] mu/ be entirely remov$ f fabrics de/9$ = comm]cial use4 ,exceptions to ?is g5]al fact are sometimes made1 because unblea*$ mat]ial is *eap] & m durable ?an ! blea*$ product1 & = "s purposes is entirely satisfactory2 unblea*$ *eeseclo? & %eet+ are frequ5tly pur*as$ 9 place ( ! m exp5sive blea*$ mat]ial4 ,=m]ly1 ! only blea*+ ag5t kn[n 0 ! sun's rays1 & l95 & cotton 7 put out to sun = a week2 t is1 ! unblea*$ fabrics 7 spread on ! grass & expos$ to ! blea*+ action ( sun & dew4 ,illu/ration3 ,,fig4 #aeh4--,prep>+ *lor9e f hydro*loric acid & manganese dioxide4 #bah4 ,an ,artificial ,blea*+ ,ag5t4 ,:ile ! sun's rays are effective z a blea*+ ag5t1 ! process is sl[2 moreov]1 x w\ld be impossible to expose to ! sun's rays ! va/ quantity ( fabrics us$ 9 ! civiliz$ _w ( to-day1 & ! huge & num]\s bolts ( mat]ial :i* daily come f our looms & factories mu/ !re=e be :it5$ by artificial means4 ,! sub/ance almo/ univ]sally us$ z a rapid artificial blea*+ ag5t is *lor9e1 be/ kn[n to u z a con/itu5t ( common salt4 ,*lor9e is nev] free 9 nature1 b is f\nd 9 comb9ation ) o!r sub/ances1 z1 = example1 9 comb9ation ) sodium 9 salt1 or ) hydrog5 9 hydro*loric acid4 ,! be/ laboratory me?od ( secur+ free *lor9e is to heat 9 a wat] ba? a mixture ( hydro*loric acid & manganese dioxide1 a comp\nd conta9+ "o "p ( manganese & two p>ts ( oxyg54 ,! heat causes ! manganese dioxide to give up its oxyg51 :i* imm$iately comb9es ) ! hydrog5 ( ! hydro*loric acid & =ms wat]4 ,! manganese itself comb9es ) "p ( ! *lor9e orig9ally 9 ! acid1 b n ) all4 ,!re is ?us "s free *lor9e left ov] f ! acid1 & ?is passes (f z a gas & c be collect$1 z 9 ,figure #aeh4 ,free *lor9e is heavi] ?an air1 & h5ce :5 x leaves ! exit tube x settles at ! bottom ( ! j>1 displac+ ! air1 & f9ally fill+ ! bottle4 ,*lor9e is a v active sub/ance & comb9es readily ) mo/ sub/ances1 b especially ) hydrog52 if *lor9e comes 9 contact ) /eam1 x ab/racts ! hydrog5 & unites ) x to =m hydro*loric acid1 b x leaves ! oxyg5 free & uncomb9$4 ,?is t5d5cy ( *lor9e to comb9e ) hydrog5 makes x valuable z a blea*+ ag5t4 ,9 ord] to te/ ! effici5cy ( *lor9e z a blea*+ ag5t1 drop a wet piece ( color$ g+ham or calico into ! bottle ( *lor9e1 & notice ! rapid disappe>ance ( color f ! sample4 ,if unblea*$ musl9 is us$1 ! moi/ /rip loses its natural yell[i% hue & becomes a cle>1 pure :ite4 ,! explanation ( ! blea*+ p[] ( *lor9e is t ! *lor9e comb9es ) ! hydrog5 ( ! wat] & sets oxyg5 free2 ! uncomb9$ free oxyg5 oxidizes ! color+ matt] 9 ! clo? & de/roys x4 ,*lor9e has no effect on dry mat]ial1 z may be se5 if we put dry g+ham into ! j>2 9 ?is case !re is no wat] to furni% hydrog5 = comb9ation ) ! *lor9e1 & no oxyg5 to be set free4 #bai4 ,blea*+ ,p[d]4 ,*lor9e gas has a v injuri\s effect on ! human body1 & h5ce _c be us$ directly z a blea*+ ag5t4 ,x attacks ! muc\s membrane ( ! nose & lungs1 & produces ! effect ( a sev]e cold or cat>rh1 & :5 inhal$1 causes dea?4 ,b c]ta9 comp\nds ( *lor9e are h>mless1 & c be us$ in/ead ( *lor9e = de/roy+ ei!r natural or artificial dyes4 ,"o ( ^! comp\nds1 namely1 *loride ( lime1 is ! almo/ univ]sal blea*+ ag5t ( comm]ce4 ,x comes 9 ! =m ( p[d]1 :i* c be dissolv$ 9 wat] to =m ! blea*+ solution 9 :i* ! color$ fabrics are imm]s$4 ,b fabrics imm]s$ 9 a blea*+ p[d] solution d n lose _! color z w\ld naturally be expect$4 ,! reason = ?is is t ! *lor9e gas is n free to d its "w1 b is re/rict$ by its comb9ation ) ! o!r sub/ances4 ,by exp]im5t x has be5 f\nd t ! addition to ! blea*+ solution ( an acid1 su* z v9eg> or lemon juice or sulphuric acid1 causes ! lib]ation ( ! *lor9e4 ,! *lor9e ?us set free reacts ) ! wat] & lib]ates oxyg52 ?is 9 turn de/roys ! color+ matt] 9 ! fib]s1 & trans=ms ! mat]ial into a blea*$ product4 ,! acid us$ to lib]ate ! *lor9e f ! blea*+ p[d]1 & ! *lor9e also1 rot mat]ials ) :i* !y rema9 9 contact = any l5g? ( "t4 ,= ?is reason1 fabrics %\ld be remov$ f ! blea*+ solution z soon z possible1 & %\ld !n be r9s$ 9 "s solution1 su* z ammonia1 :i* is capable ( neutraliz+ ! h>mful sub/ances2 f9ally ! fabric %\ld be ?or\ghly r9s$ 9 wat] 9 ord] t all =eign matt] may be remov$4 ,! reason home blea*+ is s seldom satisfactory is t mo/ amateurs fail to realize ! necessity ( imm$iate neutralization & r9s+1 & all[ ! fabric to rema9 too long 9 ! blea*+ solution1 & all[ x to dry ) traces ( ! blea*+ sub/ances pres5t 9 ! fib]s4 ,mat]ial treat$ 9 ?is way is ?or\ghly blea*$1 b is at ! same "t rott5 & wor?less4 ,*loride ( lime is frequ5tly us$ 9 laundry "w2 ! clo!s are :it] ?an :5 clean$ ) soap & simple wa%+ p[d]s1 b !y soon we> out unless ! precaution has be5 tak5 to add an anti*lor or neutraliz] to ! blea*+ solution4 #bbj4 ,comm]cial ,blea*+4 ,9 comm]cial blea*+ ! mat]ial to be blea*$ is fir/ moi/5$ ) a v weak solution ( sulphuric acid or hydro*loric acid1 & is !n imm]s$ 9 ! blea*+ p[d] solution4 ,z ! moi/ mat]ial is drawn ?r\gh ! blea*+ solution1 ! acid on ! fabric acts ^u ! solution & releases *lor9e4 ,! *lor9e lib]ates oxyg5 f ! wat]4 ,! oxyg5 9 turn attacks ! color+ matt] & de/roys x4 ,illu/ration3 ,,fig4 #aei4--,! mat]ial to be blea*$ is drawn ?r\gh an acid a1 !n ?r\gh a blea*+ solution b1 & f9ally ?r\gh a neutraliz+ solution c4 ,! blea*$ mat]ial is !n imm]s$ 9 a neutraliz+ ba? & is f9ally r9s$ ?or\ghly 9 wat]4 ,/rips ( cotton or l95 _m miles long are drawn by ma*9]y into & out ( ! v>i\s solutions 7,fig4 #aei71 are !n pass$ ov] press+ roll]s1 & em]ge sn[ :ite1 ready to be dy$ or to be us$ z :ite fabric4 #bba4 ,wool & ,silk ,blea*+4 ,animal fib]s l silk1 wool1 & fea!rs1 & "s vegetable fib]s l /raw1 _c be blea*$ by means ( *lor9e1 because x attacks n only ! color+ matt] b ! fib] itself1 & leaves x %runk5 & inf]ior4 ,cotton & l95 fib]s1 ap>t f ! small am\nt ( color+ matt] pres5t 9 !m1 conta9 no?+ b c>bon1 oxyg51 & hydrog51 :ile animal fib]s conta9 9 addition to ^! elem5ts "s comp\nds ( nitrog54 ,! pres5ce ( ^! nitrog5 comp\nds influ5ces ! action ( ! *lor9e & produces unsatisfactory results4 ,= animal fib]s x is !re=e necess>y to disc>d *lor9e z a blea*+ ag5t1 & to sub/itute a sub/ance :i* w h a less disa/r\s action ^u ! fib]s4 ,su* a sub/ance is to be _h 9 sulphur\s acid4 ,:5 sulphur burns1 z 9 a mat*1 x gives (f disagreeable fumes1 & if ^! are made to bubble into a vessel conta9+ wat]1 !y dissolve & =m ) ! wat] a sub/ance kn[n z sulphur\s acid4 ,t ?is solution has blea*+ prop]ties is %[n by ! fact t a color$ clo? dipp$ into x loses its color1 & unblea*$ fabrics imm]s$ 9 x are :it5$4 ,! h>mless nature ( sulphur\s acid makes x v desirable z a blea*+ ag5t1 especially 9 ! home4 ,silk1 lace1 & wool :5 blea*$ ) *lor9e become h>d & brittle1 b :5 :it5$ ) sulphur\s acid1 !y reta9 _! natural *>act]i/ics4 ,?is mild =m ( a blea*+ sub/ance has be5 put to uses :i* are n[ prohibit$ by ! pure food laws4 ,9 "s cann]ies common corn is :it5$ ) sulphur\s acid1 & is !n sold "u false repres5tations4 ,*]ries are sometimes blea*$ & !n color$ ) ! bright %ades :i* "u natural conditions indicate fre%ness4 ,blea*+ ) *lor9e is p]man5t1 ! dye/uff be+ de/roy$ by ! *lor9e2 b blea*+ ) sulphur\s acid is tempor>y1 because ! mild] blea* does n actually de/roy ! dye/uff1 b m]ely modifies x1 & 9 "t ! natural yell[ color ( /raw1 cotton1 & l95 reappe>s4 ,! yell[+ ( /raw hats dur+ ! summ] is famili> to ev]yone2 ! /raw is m]ely resum+ its natural color :i* _h be5 modifi$ by ! sulphur\s acid solution appli$ to ! /raw :5 wov54 #bbb4 ,:y ! ,color ,returns4 ,"s ( ! comp\nds =m$ by ! sulphur\s acid blea*+ process are gradually decompos$ by sunlight1 & 9 consequ5ce ! orig9al color is 9 "t p>tially re/or$4 ,! portion ( a hat protect$ by ! b& reta9s its fre% appe>ance because ! light has n _h access to x4 ,silks & o!r f9e fabrics blea*$ 9 ?is way fade ) age1 & assume an unnatural color4 ,"o reason = ?is is t ! dye us$ to color ! fabric requires a cle> :ite backgr\nd1 & loses its *>act]i/ic hues :5 its f\ndation is yell[ in/ead ( :ite4 ,!n1 too1 dye/uffs are !mselves m or less affect$ by light1 & fade sl[ly "u a /rong illum9ation4 ,mat]ials :i* are n expos$ directly to an int5se & prolong$ illum9ation reta9 _! :it5ess = a long "t1 & h5ce dress mat]ials & hats :i* h be5 blea*$ ) sulphur\s acid %\ld be protect$ f ! sun's gl>e :5 n 9 use4 #bbc4 ,! ,removal ( ,/a9s4 ,blea*+ p[d] is v useful 9 ! removal ( /a9s f :ite fabrics4 ,ink spots rubb$ ) lemon juice & dipp$ 9 blea*+ solution fade away & leave on ! clo? no trace ( discoloration4 ,sometimes ^! /a9s c be remov$ by soak+ 9 milk1 & :]e ?is is possible1 x is ! bett] me?od4 ,blea*+ solution1 h[ev]1 :ile valuable 9 ! removal ( "s /a9s1 is unable to remove pa9t /a9s1 because pa9ts owe _! color to m9]al matt]1 & on ?is *lor9e is p[]less to act4 ,pa9t /a9s are be/ remov$ by ! application ( gasol9e foll[$ by soap & wat]4 ,,*apt] ,,xxiii ,,dye+ #bbd4 ,dyes4 ,"o ( ! mo/ important & lucrative indu/rial processes ( ! _w to-day is t ( /a9+ & dye+4 ,:e!r we consid] ! innum]able %ades ( lea!r us$ 9 %oes & h>nesses & uphol/]y2 ! multitude ( colors 9 ! pap] :i* cov]s our walls & reflects light rang+ f ! somb] to ! gay1 & f ! delicate to ! gorge\s2 ! artificial sc5]y :i* adorns ! /age & by its imitation ( trees & fl[]s & sky translates u to ! ,=e/ ( ,ard52 or :e!r we consid] ! unc\nt$ v>ieties ( color 9 dress mat]ials1 9 c>pets1 & 9 hang+s1 we are deal+ ) sub/ances :i* owe _! beauty to dyes & dye/uffs4 ,! color+ ( textile fabrics1 su* z cotton1 wool1 & silk1 f> outranks 9 am\nt & importance t ( lea!r1 pap]1 etc41 & h5ce ! =m] only w be consid]$ "h2 b ! !ories & facts relative to textile dye+ are applicable 9 a g5]al way to all o!r =ms z well4 #bbe4 ,plants z a ,s\rce ( ,dyes4 ,among ! mo/ beautiful examples ( man's h&iwork are ! baskets & blankets ( ! ,nor? ,am]ican ,indians1 wov5 ) a skill :i* _c be equal$ by manufactur]s1 & dy$ 9 mell[ colors ) a few simple dyes extract$ f local plants4 ,! magnific5t rugs & tape/ries ( ,p]sia & ,turkey1 & ! silks ( ,india & ,japan1 give evid5ce t a k ( dyes is widespread & anci5t4 ,until rec5tly1 ! vegetable _w 0 ! s\rce ( practically all color+ matt]1 ! pulv]iz$ root ( ! madd] plant yield+ ! r$s1 ! leaves & /ems ( ! indigo plant ! blues1 ! he>twood ( ! tropical logwood tree ! blacks & grays1 & ! fruit ( c]ta9 palm & locu/ trees yield+ ! s(t br[ns4 ,s great 0 ! comm]cial dem& = dye/uffs t l>ge areas ( l& 7 giv5 ov] to ! exclusive cultivation ( ! m important dye plants4 ,vegetable dyes are n[1 h[ev]1 r>ely us$ because ab\t ! ye> #ahef x 0 discov]$ t dyes c\ld be obta9$ f coal t>1 ! ?ick /icky liquid =m$ z a by-product 9 ! manufacture ( coal gas4 ,^! artificial coal-t>1 or anil9e1 dyes h practically undisput$ sway to-day1 & ! va/ areas ( l& =m]ly us$ = ! cultivation ( vegetable dyes are n[ free = o!r purposes4 #bbf4 ,wool & ,cotton ,dye+4 ,if a piece ( wool is soak$ 9 a solution ( a coal-t> dye1 su* z mag5ta1 ! fib] ( ! clo? draws "s ( ! dye out ( ! solution & absorbs x1 becom+ 9 consequ5ce beautifully color$4 ,! color+ matt] becomes "p & p>cel1 z x 71 ( ! wool fib]1 because repeat$ wa%+ ( ! fabric fails to remove ! newly acquir$ color2 ! mag5ta color+ matt] unites *emically ) ! fib] ( ! wool1 & =ms ) x a comp\nd insoluble 9 wat]1 & h5ce fa/ to wa%+4 ,b if cotton is us$ in/ead ( wool1 ! acquir$ color is v fa9t1 & wa%es (f readily4 ,?is is because cotton fib]s possess no *emical sub/ance capable ( unit+ ) ! color+ matt] to =m a comp\nd insoluble 9 wat]4 ,if mag5ta is replac$ by o!r artificial dyes1--= example1 sc>lets1--! result is simil>2 9 g5]al1 wool mat]ial absorbs dye readily1 & unit+ ) x is p]man5tly dy$4 ,cotton mat]ial1 on ! o!r h&1 does n comb9e *emically ) color+ matt] & !re=e is only fa9tly t+$ ) color1 & loses ?is :5 wa%$4 ,:5 silk & l95 are te/$1 x is f\nd t ! =m] behaves 9 a g5]al way z did wool1 :ile ! l95 has m simil>ity to ! cotton4 ,t vegetable fib]s1 su* z cotton & l951 %\ld act diff]5tly t[>d color+ matt] f animal fib]s1 su* z silk & wool1 is n surpris+ :5 we consid] t ! *emical nature ( ! two gr\ps is v diff]5t2 vegetable fib]s conta9 only oxyg51 c>bon1 & hydrog51 :ile animal fib]s always conta9 nitrog5 9 addition1 & 9 _m cases sulphur z well4 #bbg4 ,! ,selection ( ,dyes4 ,:5 silk & wool1 cotton & l951 are te/$ 9 v>i\s dye solutions1 x is f\nd t ! =m] h1 9 g5]al1 a great aff9ity = color+ matt] & acquire a p]man5t color1 b t cotton & l951 on ! o!r h&1 h little aff9ity = dye/uffs4 ,! color acquir$ by vegetable fib]s is1 !re=e1 usually fa9t4 ,!re are1 ( c\rse1 _m exceptions to ! g5]al /atem5t t animal fib]s dye readily & vegetable fib]s poorly1 because c]ta9 dyes fail utt]ly ) wool5 & silk mat]ial & yet are fairly satisfactory :5 appli$ to cotton & l95 fabrics4 ,!n1 too1 a dye :i* w color silk may n h any effect on wool 9 spite ( ! fact t wool1 l silk1 is an animal fib]2 & c]ta9 dye/uffs to :i* cotton responds mo/ beautifully are absolutely )\t effect on l954 ,! nature ( ! mat]ial to be dy$ det]m9es ! color+ matt] to be us$2 9 dye+ e/abli%m5ts a c>eful exam9ation is made ( all textiles receiv$ = dye+1 & ! p>ticul> dye/uffs are !n appli$ :i* long exp]i5ce has %[n to be be/ suit$ to ! mat]ial 9 "q4 ,:]e mix$ goods1 su* z silk & wool1 or cotton & wool1 are conc]n$1 ! problem is a difficult "o1 & ! c\ntless v>ieties ( gorge\sly color$ mix$ mat]ials give evid5ce ( high p]fection 9 ! art ( dye+ & weav+4 ,h\sewives :o wi% to d successful home dye+ %\ld !re=e n pur*ase dyes indiscrim9ately1 b %\ld select ! k9d be/ suit$ to ! mat]ial1 because ! color+ pr9ciple :i* w remake a silk wai/ may utt]ly ru9 a wool5 skirt or a l95 suit4 ,p[d]s design$ = special purposes may be pur*as$ f druggi/s4 #bbh4 ,indirect ,dye+4 ,we h se5 t x is practically impossible to color cotton & l95 9 a simple mann] ) any degree ( p]man5cy1 because ( ! lack ( *emical action betwe5 vegetable fib]s & color+ matt]4 ,b ! v>i$ uses to :i* dy$ articles are put make fa/ness ( color absolutely necess>y4 ,a %irt1 = example1 mu/ n be discolor$ by p]spiration1 nor a wai/ fad$ by wa%+1 nor a c>pet dull$ by sweep+ ) a damp5$ broom4 ,9 ord] to insure p]man5cy ( dyes1 an indirect me?od 0 orig9at$ :i* consi/$ ( add+ to ! fib]s a *emical capable ( act+ ^u ! dye & =m+ ) x a color$ comp\nd insoluble 9 wat]1 & h5ce safe4 ,= example1 cotton mat]ial dy$ directly 9 logwood solution has almo/ no value1 b if x is soak$ 9 a solution ( oxalic acid & alum until x becomes saturat$ ) ! *emicals1 & is !n transf]r$ to a logwood ba?1 ! color acquir$ is fa/ & beautiful4 ,?is me?od ( indirect dye+ is kn[n z ! mordant+ process2 x consi/s ( saturat+ ! fabric to be dy$ ) *emicals :i* w unite ) ! color+ matt] to =m comp\nds unaffect$ by wat]4 ,! *emicals are call$ mordants4 #bbi4 ,h[ ,v>iety ( ,color is ,secur$4 ,! color :i* is fix$ on ! fabric z a result ( *emical action betwe5 mordant & dye is frequ5tly v diff]5t f t ( ! dye itself4 ,logwood dye :5 us$ alone produces a r$di% br[n color ( no value ei!r = beauty or p]man5ce2 b if ! fabric to be dy$ is fir/ mordant$ ) a solution ( alum & oxalic acid & is !n imm]s$ 9 a logwood ba?1 x acquires a beautiful blue color4 ,moreov]1 s9ce ! color acquir$ dep5ds ^u ! mordant z well z ^u ! dye1 x is (t5 possible to obta9 a wide range ( colors by v>y+ ! mordant us$1 ! dye rema9+ ! same4 ,= example1 ) alum & oxalic acid z a mordant & logwood z a dye1 blue is obta9$2 b ) a mordant ( f]ric sulphate & a dye ( logwood1 blacks & grays result4 ,fabrics imm]s$ directly 9 aliz>9 acquire a r$di% yell[ t9t2 :51 h[ev]1 !y are mordant$ ) c]ta9 alum9ium comp\nds !y acquire a brilliant ,turkey r$1 :5 mordant$ ) *romium comp\nds1 a m>oon1 & :5 mordant$ ) iron comp\nds1 ! v>i\s %ades ( purple1 lilac1 & violet result4 #bcj4 ,color ,designs 9 ,clo?4 ,x is ?\ght t ! e>lie/ attempts at mak+ fancy mat]ials consi/$ 9 pa9t+ designs on a fabric by means ( a bru%4 ,9 m rec5t times ! design 0 cut 9 relief on h>d wood1 ! relief be+ !n daub$ ) color+ matt] & appli$ by h& to successive portions ( ! clo?4 ,! mo/ mod]n me?od ( design-mak+ is t ( ma*9e or roll] pr9t+4 ,9 ?is1 ! relief blocks are replac$ by engrav$ copp] rolls :i* rotate cont9u\sly & 9 ! c\rse ( _! rotation automatically receive color+ matt] on ! engrav$ portion4 ,! clo? is to be pr9t$ is !n drawn uni=mly ov] ! rotat+ roll1 receiv+ color f ! engrav$ design2 9 ?is way1 ! color patt]n is automatically pr9t$ on ! clo? ) p]fect regul>ity4 ,9 cases :]e ! fabrics d n unite directly ) ! color+ matt]1 ! design is suppli$ ) a mordant & ! impression made on ! fabric is t ( ! mordant2 :5 ! fabric is lat] transf]r$ to a dye ba?1 ! mordant$ portions1 repres5t$ by ! design1 unite ) ! color+ matt] & ?us =m ! desir$ color patt]ns4 ,unless ! pr9t+ is well done1 ! color+ matt] does n ?or\ghly p5etrate ! mat]ial1 & only a fa9t blurr$ design appe>s on ! back ( ! clo?2 ! gaudy designs ( *eap calicoes & g+hams (t5 d n %[ at all on ! "u side4 ,su* c>elessly made pr9ts are n fa/ to wa%+ or light1 & soon fade4 ,b 9 ! bett] grades ( mat]ial ! pr9t+ is well done1 & ! color designs are fairly fa/1 & a little c>e 9 ! laundry suffices to elim9ate any dang] ( fad+4 ,color designs ( ! greate/ durability are produc$ by ! weav+ toge!r ( color$ y>ns4 ,:5 y>n is dy$1 ! color+ matt] p5etrates to e "p ( ! fib]1 & h5ce ! patt]ns =m$ by ! weav+ toge!r ( well-dy$ y>ns are v fa/ to light & wat]4 ,if ! color designs to be wov5 9 ! clo? are intricate1 complex ma*9]y is necess>y & skillful h&work2 h5ce1 patt]ns =m$ by ! weav+ ( color$ y>ns are exp5sive & less common ?an pr9t$ fabrics4 ,,*apt] ,,xxiv ,,*emicals ,,z ,,dis9fectants ,,& ,,pres]vatives #bca4 ,! prev5tion ( disease epidemics is "o ( ! mo/ /rik+ a*ievem5ts ( mod]n sci5ce4 ,food1 clo?+1 furniture1 & o!r objects contam9at$ 9 any way by disease g]ms may be dis9fect$ by *emicals or by heat1 & widespread infection f p]sons suff]+ ) a contagi\s disease may be prev5t$4 ,illu/ration3 ,,fig4 #afj4--,pa/euriz+ app>atus1 an arrangem5t by :i* milk is conv5i5tly heat$ to de/roy disease g]ms4 ,:5 disease g]ms are )9 ! body1 ! problem is f> f simple1 because *emicals :i* w\ld effectively de/roy ! g]ms w\ld be fatal to life itself4 ,b :5 g]ms are outside ! body1 z 9 wat] or milk1 or on clo?+1 di%es1 or furniture1 !y c be easily kill$4 ,"o ( ! be/ me?ods ( de/roy+ g]ms is to subject !m to int5se heat4 ,contam9at$ wat] is made safe by boil+ = a few m9utes1 because ! /rong heat de/roys ! disease-produc+ g]ms4 ,scald$ or ,pa/euriz$ milk saves ! lives ( scores ( babies1 because ! g]ms ( summ] compla9t :i* lurk 9 poor milk are kill$ & r5d]$ h>mless 9 ! process ( scald+4 ,di%es us$ by consumptives1 & p]sons suff]+ f contagi\s diseases1 c be made h>mless by ?or\gh wa%+ 9 ?ick suds ( almo/ boil+ wat]4 ,! b$d+ & clo?+ ( p]sons suff]+ ) diph!ria1 tub]culosis1 & o!r g]m diseases %\ld always be boil$ & hung to dry 9 ! bright sunlight4 ,heat & sun%9e are two ( ! be/ dis9fectants4 #bcb4 ,*emicals4 ,objects1 su* z furniture1 :i* _c be boil$1 are dis9fect$ by ! use ( any "o ( sev]al *emicals1 su* z sulphur1 c>bolic acid1 *loride ( lime1 corrosive sublimate1 etc4 ,"o ( ! simple/ me?ods ( dis9fect+ consi/s 9 burn+ sulphur 9 a room ^: doors1 w9d[s1 & keyholes h be5 clos$1 s t ! burn+ fumes _c escape1 b rema9 9 ! room long en\gh to de/roy disease g]ms4 ,?is is probably ! mo/ common means ( fumigation4 ,= g5]al purposes1 c>bolic acid is "o ( ! v be/ dis9fectants1 b mu/ be us$ ) caution1 z x is a deadly poison except :5 v dilute4 ,*loride ( lime :5 expos$ to ! air & moi/ure sl[ly gives (f *lor9e1 & c be us$ z a dis9fectant because ! gas ?us set free attacks g]ms & de/roys !m4 ,= ?is reason *loride ( lime is an excell5t dis9fectant ( dra9pipes4 ,c]ta9 b[el tr\bles1 su* z di>rhoea1 are due to microbes1 & if ! wa/e matt] ( a p]son suff]+ f ?is or simil> diseases is all[$ passage ?r\gh ! dra9age sy/em1 mu* damage may be done4 ,b a small am\nt ( *loride ( lime 9 ! closet b[l w insure dis9fection4 #bcc4 ,p]sonal ,dis9fection4 ,! h&s may ga!r g]ms f any sub/ances or objects ) :i* !y come 9 contact2 h5ce ! h&s %\ld be wa%$ ) soap & wat]1 & especially be=e eat+4 ,physicians :o p]=m op]ations wa% n only _! h&s1 b _! in/rum5ts1 /]iliz+ ! latt] by plac+ !m 9 boil+ wat] = sev]al m9utes4 ,cuts & w\nds all[ easy access to ! body2 a small cut has be5 kn[n to cause dea? because ( ! bact]ia :i* f\nd _! way into ! op5 w\nd & produc$ disease4 ,9 ord] to de/roy any g]ms :i* may h ent]$ into ! cut f ! in/rum5t1 x is well to wa% out ! w\nd ) "s mild dis9fectant1 su* z v dilute c>bolic acid or hydrog5 p]oxide1 & !n to b9d ! w\nd ) a clean clo?1 to prev5t lat] entrance ( g]ms4 #bcd4 ,*emicals z ,food ,pres]vatives4 ,! spoil+ ( meats & s\ps1 & ! s\r+ ( milk & pres]ves1 are due to g]ms :i*1 l ^? produc+ disease1 c be de/roy$ by heat & by *emicals4 ,milk heat$ to ! boil+ po9t does n s\r readily1 & successful cann+ consi/s 9 cook+ fruits & vegetables until all ! g]ms are kill$1 & !n seal+ ! cans s t g]ms f outside _c f9d entrance & undo ! "w ( ! cann]4 ,"s deal]s & manufactur]s h le>n$ t c]ta9 *emicals w act z food pres]vatives1 & h5ce !y h replac$ ! safe me?od ( c>eful cann+ by ! quick] & simpl] plan ( add+ *emicals to food4 ,cat*up1 sauces1 & jellies are n[ frequ5tly pres]v$ 9 ?is way4 ,b ! *emicals :i* de/roy bact]ia frequ5tly injure ! consum] z well4 ,& s mu* h>m has be5 done by food pres]vatives t ! pure food laws require t cans & bottles conta9 a label$ /atem5t ( ! k9d & quantity ( *emicals us$4 ,ev5 milk is n exempt1 b is doctor$ to prev5t s\r+1 ! pres]vative mo/ g5]ally us$ by milk deal]s be+ =maldehyde4 ,! va/ quantity ( milk consum$ by "y & old1 sick & well1 makes ! use ( =maldehyde a s]i\s m5ace to heal?1 because no con/itution c endure ! injury done by ! con/ant use ( pres]vatives4 ,! mo/ popul> & widely us$ pres]vatives ( meats are borax & boric acid4 ,^! *emicals n only arre/ decay1 b p>tially re/ore to old & bad meat ! appe>ance ( fre%ness2 9 ?is way unscrupul\s deal]s are able to sell to ! public 9 "o =m or o!r meats :i* may h und]gone p>tial decomposition2 sausage frequ5tly conta9s p>tially decompos$ meat1 re/or$ z x 7 by *emicals4 ,9 jams & cat*ups !re is abundant opportunity = pres]vatives2 badly or p>tially decay$ fruits are sometimes dis9fect$ & us$ z ! basis ( foods sold by s-call$ good deal]s4 ,b5zoate ( soda1 & salicylic acid are ! *emicals mo/ widely employ$ = ?is purpose1 ) coal-t> dyes to simulate ! natural color ( ! fruit4 ,_m ( ! *eap c&ies sold by /reet v5d]s are n fit = consumption1 s9ce !y are n only made ( bad mat]ial1 b are frequ5tly 9 addition giv5 a light dipp+ 9 v>ni% z a protection aga9/ ! decay+ influ5ces ( ! atmosph]e4 ,! only wise pres]vatives are ^? long kn[n & employ$ by our ance/ors2 salt1 v9eg>1 & spices are all food pres]vatives1 b !y are at ! same "t sub/ances :i* 9 small am\nts are n injuri\s to ! body4 ,smok$ h]r+ & salt$ mack]el are *emically pres]v$ foods1 b !y are none ! less safe & dige/ible4 #bce4 ,! ,pres]vation ( ,wood & ,metal4 ,! decay+ ( wood & ! ru/+ ( metal are due to ! action ( air & moi/ure4 ,:5 wood & metal are surr\nd$ ) a cov]+ :i* nei!r air nor moi/ure c p5etrate1 decay & ru/ are prev5t$4 ,pa9t af=ds su* a protective cov]+4 ,! ma9 con/itu5t ( pa9t is a comp\nd ( :ite lead or o!r metallic sub/ance2 ?is is mix$ ) l9se$ oil or its equival5t 9 ord] t x may be spread ov] wood & metal 9 a ?91 ev5 coat+4 ,aft] ! mixture has be5 appli$1 x h>d5s & =ms a t\gh sk9 fairly imp]vi\s to wea!r+4 ,= ! sake ( ornam5tation1 v>i\s color$ pigm5ts are add$ to ! pa9t & give v>iety ( effect4 ,railroad ties & /reet pav+ blocks are ord9>ily protect$ by oil r ?an pa9t4 ,wood is soak$ 9 creosote oil until x becomes ?or\ghly saturat$ ) ! oily sub/ance4 ,! pores ( ! wood are ?us clos$ to ! entrance ( air & moi/ure1 & decay is avoid$4 ,wood treat$ 9 ?is way is v durable4 ,creosote is poison\s to insects & _m small animals1 & ?us acts z a pres]vation n only aga9/ ! elem5ts b aga9/ animal life z well4 ,,*apt] ,,xxv ,,drugs ,,& ,,pat5t ,,m$ic9es #bcf4 ,/imulants & ,n>cotics4 ,man has le>n$ n only ! action ( sub/ances ^u ea* o!r1 su* z blea*+ solution ^u color+ matt]1 wa%+ soda ^u grease1 acids ^u bases1 b also ! effect :i* c]ta9 *emicals h ^u ! human body4 ,drugs & _! v>y+ effects ^u ! human sy/em h be5 kn[n to mank9d f remote ages2 9 ! e>ly days1 famili> leaves1 roots1 & twigs 7 /eep$ 9 wat] to =m m$ic9es :i* s]v$ = ! treatm5t ( all ailm5ts4 ,9 m rec5t times1 h[ev]1 ^! simple h]b teas h be5 supplant$ by complex drugs1 & n[ m$ic9es are comp\nd$ n only f innum]able plant products1 b f animal & m9]al matt] z well4 ,qu99e1 rhub>b1 & arnica are examples ( purely vegetable products2 iron1 m]cury1 & ars5ic are equally well kn[n z di/9ctly m9]al products1 :ile cod-liv] oil is ! mo/ famili> illu/ration ( an animal rem$y4 ,ord9>ily a comb9ation ( products be/ s]ves ! ends ( ! physician4 ,sub/ances :i*1 l cod-liv] oil1 s]ve z food to a worn-out body1 or1 l iron1 t5d to enri* ! blood1 or1 l qu99e1 aid 9 br++ an abnormal sy/em to a heal?y condition1 are valuable s]vants & _c be entirely disp5s$ ) s long z man is subject to disease4 ,b sub/ances :i*1 l opium1 laudanum1 & alcohol1 are n requir$ by ! body z food1 or z a sy/ematic1 intellig5t aid to recov]y1 b are tak5 solely = ! /imulus ar\s$ or = ! ins5sibility induc$1 are h>mful to man1 & _c be indulg$ 9 by him )\t ultimate m5tal1 moral1 & physical loss4 ,sub/ances ( ! latt] class are kn[n z n>cotics & /imulants4 #bcg4 ,! ,co/ ( ,heal?4 ,9 ! physical z 9 ! f9ancial _w1 no?+ is to be _h )\t a price4 ,vigor1 endurance1 & m5tal al]tness are b\ght by hygi5ic liv+2 t is1 by prop] food1 fre% air1 ex]cise1 cleanl9ess1 & reasonable h\rs4 ,"s p wi% vigor1 endurance1 etc41 b are unwill+ to live ! life :i* w develop ^! qualities4 ,pl5ty ( sleep1 ex]cise1 & simple food all t5d to lay ! f\ndations ( heal?4 ,_m1 h[ev]1 are n will+ to take ! c>e necess>y = heal?ful liv+1 because x w\ld =ce !m to sacrifice "s ( ! h\rs ( pleasure4 ,soon] or lat]1 ^! pleasure-seek]s beg9 to feel tir$ & worn1 & "s ( !m turn to drugs & n>cotics = artificial /r5g?4 ,at fir/ ! drugs seem to re/ore ! lo/ en]gy1 & )\t h>m2 h[ev]1 ! co/ soon proves to be "o ( ! highe/ ,nature ev] dem&s4 #bch4 ,! ,unc\nt$ ,co/4 ,! fir/ & mo/ obvi\s effect ( opium1 = example1 is to dead5 pa9 & to ar\se pleasure2 b :ile ! drug is produc+ ^! soo?+ s5sations1 x int]f]es ) bodily functions4 ,secretion1 dige/ion1 absorption ( food1 & ! removal ( wa/e matt]s are h9d]$4 ,cont9u$ use ( ! drug leads to heada*e1 exhau/ion1 n]v\s depression1 & he>t weakness4 ,!re is ?us a heavy toll reckon$ aga9/ ! us]1 & ! cr$itor is rel5tless 9 dem&+ paym5t4 ,moreov]1 ! respite all[$ by a n>cotic is exce$+ly brief1 & a depression :i* is long & deep inevitably foll[s4 ,9 ord] to ov]come ?is depression1 rec\rse is usually _h to a fur!r dose1 & z "t goes on1 ! int]vals ( depression become m frequ5t & la/+1 & ! necessity to ov]come !m increases4 ,?us )\t int5tion "o f9ds "o's self b\nd to ! drug1 its fa/ victim4 ,! sanatoria ( our c\ntry are cr[d$ ) p :o are try+ to free !mselves ( a drug habit into :i* !y h drift$ un9t5tionally if n altoge!r unkn[+ly4 ,:at is true ( opium is equally applicable to o!r n>cotics4 #bci4 ,! ,"r ,use ( ,n>cotics4 ,9 ! h&s ( ! physician1 n>cotics are a great bless+4 ,9 "s cases1 by reliev+ pa91 !y give ! sy/em ! re/ necess>y = ov]com+ ! cause ( ! pa94 ,only ^? :o "k ( ! suff]+ endur$ 9 =m] times c fully appreciate ! decrease 9 pa9 br\ght ab\t by ! prop] use ( n>cotics4 #bdj4 ,pat5t ,m$ic9es1 ,c\gh ,sirups4 ,a reputable physician is solicit\s reg>d+ ! p]man5t welf>e ( 8 pati5t & adm9i/]s c>efully *os5 & h>mless drugs4 ,m]e m$ic9e v5d]s1 h[ev]1 ignore ! good ( mank9d1 & flood ! m>ket ) *eap pat5t prep>ations :i* delude & injure ^? :o pur*ase1 b br+ millions ( doll>s to ^? :o manufacture4 ,practically all ( ^! pat5t1 or propriet>y1 prep>ations conta9 a l>ge proportion ( n>cotics or /imulants1 & h5ce ! b5efit :i* !y seem to af=d ! us] is by no means g5u9e2 exam9ation %[s t ! relief br\ght by !m is due ei!r to a tempor>y dead5+ ( s5sibilities by n>cotics or to a fleet+ /imulation by alcohol & k9dr$ sub/ances4 ,among ! mo/ common ailm5ts ( bo? "y & old are c\ghs & colds2 h5ce _m pat5t c\gh mixtures h be5 manufactur$ & plac$ on ! m>ket = ! consumption ( a cr$ul\s public4 ,su* quick cures almo/ inv>iably conta9 "o or m n>cotic drugs1 & n only d n relieve ! cold p]man5tly1 b occasion subsequ5t disord]s4 ,ev5 loz5ges & pa/illes are n free f fraud1 b h a goodly proportion ( n>cotics1 conta9+ 9 "s cases *lor(orm1 morph9e1 & e!r4 ,! widespread use ( pat5t c\gh m$ic9es is due l>gely to ! fact t _m p]sons avoid consult+ a physician ab\t s trivial an ailm5t z an ord9>y cold1 or are reluctant to pay a m$ical fee = :at seems a slight indisposition & h5ce attempt to doctor !mselves4 ,cat>rh is a v preval5t disease 9 ,am]ica1 & consequ5tly num]\s cat>rh rem$ies h be5 devis$1 mo/ ( :i* conta9 9 a disguis$ =m ! p]nici\s drug1 coca9e4 ,laws h be5 enact$ :i* require on ! labels a decl>ation ( ! cont5ts ( ! prep>ation1 bo? z to ! k9d ( drug us$ & ! am\nt1 & ! *oice ( accept+ or refus+ su* mixtures is left to ! individual4 ,b ! great mass ( p are ignorant ( ! h>mful nature ( drugs 9 g5]al1 & h5ce d n ev5 read ! self-accus+ label1 or if !y d glance at x1 fail to compreh5d ! dang]\s nature ( ! drugs specifi$ !re4 ,9 ord] to safegu>d ! un9=m$ pur*as] & to re/rict ! manufacture ( h>mful pat5t rem$ies1 "s /ates limit ! sale ( all prep>ations conta9+ n>cotics & ?us give free re9 to nei!r consum] nor produc]4 #bda4 ,soo?+ ,sirups2 ,s(t ,dr9ks4 ,! developm5t ( a race is limit$ by ! m5tal & physical gr[? ( its *ildr51 & yet ?\s&s ( its *ildr5 are annually /unt$ & weak5$ by drugs1 because mo/ colic cures1 tee?+ concoctions1 & soo?+ syrups are m]ely agreeably flavor$ drug mixtures4 ,^? :o h us$ su* prep>ations freely1 "k t a *ild usually becomes fretful & irritable betwe5 doses1 & c be quiet$ only by l>g] & m frequ5t supplies4 ,a habit =m$ 9 ?is way is difficult to ov]come1 & _m a *ild :5 sc>cely ov] its babyhood _h a crav+ :i* 9 lat] ye>s may lead to sy/ematic drug tak+4 ,& ev5 ?\gh ! p]nici\s drug crav+ is n creat$1 consid]able h>m is done to ! *ild1 because its body is left weak & non-resi/ant to diseases ( infancy & *ildhood4 ,_m ( our s(t dr9ks conta9 n>cotics4 ,! use ( ! coca leaf & ! kola nut = su* prep>ations has increas$ v greatly )9 ! la/ few ye>s1 & d\btless legislation w soon be in/itut$ aga9/ ! indiscrim9ate sale ( s(t dr9ks4 #bdb4 ,heada*e ,p[d]s4 ,! /ress & /ra9 ( mod]n life has op5$ wide ! door to a multitude ( bodily ills1 among :i* may be m5tion$ heada*e4 ,"w mu/ be done & bus9ess att5d$ to1 & ! av]age suff]] does n take "t f 8 vocation to inve/igate ! cause ( ! heada*e1 b un?9k+ly grasps at any rem$y :i* w remove ! imm$iate pa91 & utt]ly disreg>ds lat] injury4 ,! relief af=d$ by mo/ heada*e mixtures is due to ! pres5ce ( antipyr9 or acetanilid1 & x has be5 %[n conclusively t ^! drugs weak5 he>t action1 dim9i% circulation1 r$uce ! numb] ( r$ corpuscles 9 ! blood1 & br+ on a condition ( *ronic anemia4 ,pallid *eeks & blue lips are visible evid5ce ( ! too frequ5t use ( heada*e p[d]s4 ,! labels requir$ by law are (t5 deceptive & convey no adequate idea ( ! am\nt ( drug consum$2 = example1 #bdj gra9s ( acetanilid to an ounce seems a small quantity ( drug = a p[d]1 b :5 "o consid]s t !re are only #dhj gra9s 9 an ounce1 x w be se5 t ea* p[d] is "o half acetanilid4 ,p[d]s tak5 9 small quantities & at r>e int]vals are app>5tly h>mless2 b !y nev] remove ! cause ( ! tr\ble1 & h5ce ! discom=t soon returns ) r5ew$ =ce4 ,ord9>ily1 hygi5ic liv+ w elim9ate ! s\rce ( ! tr\ble1 b if x does n1 a physician %\ld be consult$ & m$ic9e %\ld be procur$ f him :i* w re/ore ! d]ang$ sy/em to its normal heal?y condition4 #bdc4 ,o!r ,deceptions4 ,ne>ly all pat5t m$ic9es conta9 "s alcohol1 & 9 _m1 ! quantity ( alcohol is f> 9 excess ( t f\nd 9 ! /ronge/ w9es4 ,tonics & bitt]s adv]tis$ z a cure = spr+ fev] & a worn-out sy/em are sc>cely m ?an *eap cocktails1 z "o writ] has d]isively call$ !m1 & ! am\nt ( alcohol 9 "s widely adv]tis$ pat5t rem$ies is al>m+ly l>ge & almo/ equal to t ( /rong :isky4 ,illu/ration3 ,,fig4 #afa4--;,diagram %[+ ! am\nt ( alcohol 9 "s alcoholic dr9ks & 9 "o mu* us$ pat5t m$ic9e4 ,"s consci5ti\s p]sons :o w\ld n t\* be]1 w9e1 :isky1 or any o!r intoxicat+ dr9k consume pat5t rem$ies conta9+ l>ge quantities ( alcohol & ?us un9t5tionally expose !mselves to m5tal & physical dang]4 ,9 all cases ( bodily disord]1 ! only safe c\rse is to consult a physician :o has devot$ himself to ! /udy ( ! body & ! me?ods by :i* a disord]$ sy/em may be re/or$ to heal?4 ,,*apt] ,,xxvi ,,nitrog5 ,,& ,,its ,,relation ,,to ,,plants #bdd4 ,nitrog54 ,a sub/ance :i* plays an important "p 9 animal & plant life is nitrog54 ,soil & ! f]tiliz]s :i* enri* x1 ! plants :i* gr[ on x1 & ! animals :i* fe$ on ^!1 all conta9 nitrog5 or nitrog5\s comp\nds4 ,! atmosph]e1 :i* we ord9>ily ?9k ( z a /oreh\se ( oxyg51 conta9s f> m nitrog5 ?an oxyg51 s9ce f\r fif?s ( its :ole weight is made up ( ?is elem5t4 ,nitrog5 is colorless1 odorless1 & ta/eless4 ,air is compos$ *iefly ( oxyg5 & nitrog52 if1 !re=e1 ! oxyg5 9 a vessel fill$ ) air c be made to unite ) "s o!r sub/ance or c be remov$1 !re w be a residue ( nitrog54 ,?is c be done by float+ on wat] a light di% conta9+ phosphorus1 !n ignit+ ! phosphorus1 & plac+ an inv]t$ j> ov] ! burn+ sub/ance4 ,! phosphorus 9 burn+ unites ) ! oxyg5 ( ! air & h5ce ! gas t rema9s 9 ! j> is *iefly nitrog54 ,x has ! *>act]i/ics m5tion$ above &1 9 addition1 does n comb9e readily ) o!r sub/ances4 #bde4 ,plant ,food4 ,food is ! c\rse ( en]gy 9 e liv+ ?+ & is ess5tial to bo? animal & plant life4 ,plants get _! food f ! lifeless matt] :i* exi/s 9 ! air & 9 ! soil2 :ile animals get _! food f plants4 ,x is true t man & _m o!r animals eat fle%y foods & dep5d ^u !m = p>tial su/5ance1 b ! ultimate s\rce ( all animal food is plant life1 s9ce meat-produc+ animals live ^u plant gr[?4 ,plants get _! food f ! air1 ! soil1 & moi/ure4 ,f ! air1 ! leaves take c>bon dioxide & wat] & trans=m !m into />*y food2 f ! soil1 ! roots take wat] ri* 9 m9]al matt]s dissolv$ f ! soil4 ,f ! sub/ances ?us ga!r$1 ! plant lives & builds up its /ructure4 ,a food sub/ance necess>y to plant life & gr[? is nitrog54 ,s9ce a va/ /ore ( nitrog5 exi/s 9 ! air1 x w\ld seem t plants %\ld nev] lack = ?is food1 b mo/ plants are unable to make use ( ! b\ndless /ore ( atmosph]ic nitrog51 because !y d n possess ! p[] ( ab/ract+ nitrog5 f ! air4 ,= ?is reason1 !y h to dep5d solely ^u nitrog5\s comp\nds :i* are pres5t 9 ! soil & are soluble 9 wat]4 ,! soluble nitrog5\s soil comp\nds are absorb$ by roots & are utiliz$ by plants = food4 #bdf4 ,! ,pov]ty ( ! ,soil4 ,plant roots are con/antly tak+ nitrog5 & its comp\nds f ! soil4 ,if crops :i* gr[ f ! soil are remov$ ye> aft] ye>1 ! soil becomes poor] 9 nitrog51 & f9ally possesses too little ( x to support vigor\s & heal?y plant life4 ,! nitrog5 ( ! soil c be re/or$ if we add to x a f]tiliz] conta9+ nitrog5 comp\nds :i* are soluble 9 wat]4 ,decay$ vegetable matt] conta9s l>ge quantities ( nitrog5 comp\nds1 & h5ce if decay$ vegetation is plac$ ^u soil or is pl[$ into soil1 x acts z a f]tiliz]1 return+ to ! soil :at 0 tak5 f x4 ,s9ce man & all o!r animals subsi/ ^u plants1 _! bodies likewise conta9 nitrog5\s sub/ances1 & h5ce manure & wa/e animal matt] is valuable z a f]tiliz] or soil re/or]4 #bdg4 ,bact]ia z ,nitrog5 ,ga!r]s4 ,soil f :i* crops are remov$ ye> aft] ye> usually becomes less f]tile1 b ! soil f :i* crops ( clov]1 peas1 beans1 or alfalfa h be5 remov$ is ri*] 9 nitrog5 r ?an poor]4 ,?is is because ! roots ( ^! plants (t5 h on !m t9y swell+s1 or tub]cles1 9 :i* millions ( c]ta9 bact]ia live & multiply4 ,^! bact]ia h ! rem>kable p[] ( tak+ free nitrog5 f ! air 9 ! soil & ( comb9+ x ) o!r sub/ances to =m comp\nds :i* plants c use4 ,! bact]ia-made comp\nds dissolve 9 ! soil wat] & are absorb$ into ! plant by ! roots4 ,s mu* nitrog5-conta9+ mat]ial is made by ! root bact]ia ( plants ( ! pea family t ! soil 9 :i* !y gr[ becomes some:at ri*] 9 nitrog51 & if plants :i* _c make nitrog5 are subsequ5tly plant$ 9 su* a soil1 !y f9d !re a /ore ( nitrog54 ,a crop ( peas1 beans1 or clov] is equival5t to nitrog5\s f]tiliz] & helps to make ready ! soil = o!r crops4 ,illu/ration3 ,,fig4 #afb4--,roots ( soy bean hav+ tub]cle-be>+ bact]ia4 #bdh4 ,artificial ,f]tiliz]s4 ,plants ne$ o!r foods besides nitrog51 & !y exhau/ ! soil n only ( nitrog51 b also ( phosphorus & pota%1 s9ce l>ge quantities ( ^! are necess>y = plant life4 ,!re are _m o!r sub/ances absorb$ f ! soil by ! plant1 namely1 iron1 sodium1 calcium1 magnesium1 b ^! are us$ 9 small] quantities & ! supply 9 ! soil does n readily become exhau/$4 ,comm]cial f]tiliz]s g5]ally conta9 nitrog51 phosphorus1 & pota% 9 am\nts v>y+ ) ! requirem5ts ( ! soil4 ,:eat requires a l>ge am\nt ( phosphorus & quickly exhau/s ! gr\nd ( t food /uff2 a field :i* has support$ a crop ( :eat is p>ticul>ly poor 9 phosphorus1 & a satisfactory f]tiliz] = t l& w\ld necess>ily conta9 a l>ge p]c5tage ( phosphorus4 ,! f]tiliz] to be us$ 9 a soil dep5ds ^u ! "* ( ! soil & ^u ! crops previ\sly gr[n on x4 ,illu/ration3 ,,fig4 #afc4--,wat] cultures ( buck:eat3 #a1 ) all ! food elem5ts2 #b1 )\t pota%2 #c1 )\t nitrates4 ,! quantity ( f]tiliz] ne$$ by ! f>m]s ( ! _w is enorm\s1 & ! problem ( secur+ ! necess>y sub/ances 9 quantities suffici5t to satisfy ! dem& bids fair to be s]i\s4 ,b mod]n *emi/ry is at "w on ! problem1 & already x is possible to make "s nitrog5 comp\nds on a comm]cial scale4 ,:5 nitrog5 gas is 9 contact ) heat$ calcium c>bide1 a reaction takes place :i* results 9 ! =mation ( calcium nitride1 a comp\nd suitable = enri*+ ! soil4 ,!re are o!r comm]cial me?ods = obta9+ nitrog5 comp\nds :i* are suitable = absorption by plant roots4 ,phosphorus is obta9$ f bone a% & f phosphate rock :i* is widely di/ribut$ ov] ! surface ( ! e>?4 ,bone a% & ?\s&s ( tons ( phosphate rock are treat$ ) sulphuric acid to =m a phosphorus comp\nd :i* is soluble 9 soil wat] & :i*1 :5 add$ to soil1 w be usable by ! plants gr[+ !re4 ,! o!r important +r$i5t ( mo/ f]tiliz]s is pota%4 ,wood a%es are ri* 9 pota% & are a valuable addition to ! soil4 ,b ! am\nt ( pota% ?us obta9$ is f> too limit$ to supply ! ne$s ( agriculture2 & to-day ! ma9 s\rces ( pota% are ! va/ deposits ( potassium salts f\nd 9 ,prussia4 ,al?\gh ,g]many n[ furni%es ! ,am]ican f>m] ) ! bulk ( 8 pota%1 %e may n d s mu* long]4 ,9 #aiaa an indirect pota% tax 0 levi$ by ,g]many on h] be/ cu/om]1 ! ,unit$ ,/ates1 to :om #ae million doll>s' wor? ( pota% _h be5 sold ! prec$+ ye>4 ,?is l$ ,am]icans to inquire :e!r pota% c\ld n be obta9$ at home4 ,geologi/s say t long ages ago ,g]many 0 subm]g$1 t ! wat]s sl[ly evaporat$ & t ! v>i\s sub/ances 9 ! sea wat] 7 deposit$ 9 ?ick lay]s4 ,! deposits ?us left by ! evaporation ( ! sea wat] gradually became hidd5 by s$im5t & soil1 & lo/ to sight4 ,f su* deposits1 pota% is obta9$4 ,geologi/s tell u t our own ,we/]n ,/ates 7 once subm]g$1 & t ! wat]s evaporat$ & disappe>$ f our l& v mu* z !y did f ,g]many4 ,! ,great ,salt ,lake ( ,utah is a relic ( a great body ( wat]4 ,if x be true t wat]s once cov]$ our ,we/]n ,/ates1 !re may be buri$ deposits ( pota% !re1 & to-day ! se>* = ! hidd5 treasure is go+ on ) ! en]gy & en?usiasm *>act]i/ic ( ,am]ica4 ,ano!r probable s\rce ( pota% is seawe$4 ,! sea is a va/ res]voir ( pota%1 & seawe$1 especially ! giant kelp1 absorbs l>ge quantities ( ?is pota%4 ,a ton ( dri$ kelp 7dri$ by sun & w9d7 conta9s ab\t #ejj p\nds ( pure pota%4 ,! kelps are abundant1 cov]+ ?\s&s ( squ>e miles 9 ! ,pacific ,ocean1 f ,mexico to ! ,arctic ,ocean4 ,,*apt] ,,xxvii ,,s\nd #bdi4 ,! ,s5ses4 ,all ! in=mation :i* we possess ( ! _w ar\nd u comes to u ?r\gh ! use ( ! s5ses ( sight1 he>+1 ta/e1 t\*1 & smell4 ,( ! five s5ses1 sight & he>+ are g5]ally consid]$ ! mo/ valuable4 ,9 prec$+ ,*apt]s we /udi$ ! important facts relative to light & ! p[] ( vision2 x rema9s = u to /udy ,s\nd z we /udi$ ,light1 & to le>n :at we c ( s\nd & ! p[] to he>4 #bej4 ,h[ ,s\nd is ,produc$4 ,if "o inve/igates ! s\rce ( any s\nd1 he w always f9d t x is due to motion ( "s k9d4 ,a sudd5 noise is trac$ to ! fall ( an object1 or to an explosion1 or to a collision2 9 fact1 is due to ! motion ( matt]4 ,a piano gives out s\nd :5ev] a play] /rikes ! keys & sets 9 motion ! v>i\s wires )9 ! piano2 spee* & song are caus$ by ! motion ( *e/1 vocal cords1 & lips4 ,illu/ration3 ,,fig4 #afd4--,sprays ( wat] %[ t ! =k is 9 motion4 ,if a l>ge d9n] bell is rung1 its motion or vibration may be felt on t\*+ x ) ! f+]4 ,if a tun+ =k is made to give =? s\nd by /rik+ x aga9/ ! knee1 or hitt+ x ) a rubb] hamm]1 & is !n t\*$ to ! surface ( wat]1 small sprays ( wat] w be ?r[n out1 %[+ t ! prongs ( ! =k are 9 rapid motion4 7,a rubb] hamm] is made by putt+ a piece ( glass tub+ ?r\gh a rubb] cork47 ,if a light cork ball on ! end ( a ?read is br\ght 9 contact ) a s\nd+ =k1 ! ball does n rema9 at re/1 b vibrates back & =?1 be+ driv5 by ! mov+ prongs4 ,illu/ration3 ,,fig4 #afe4--,! ball does n rema9 at re/ ,^! simple facts lead u to conclude t all s\nd is due to ! motion ( matt]1 & t a s\nd+ body ( any k9d is 9 rapid motion4 #bea4 ,s\nd is c>ri$ by ,matt]4 ,9 mo/ cases s\nd rea*es ! e> ?r\gh ! air2 b air is n ! only m$ium ?r\gh :i* s\nd is c>ri$4 ,a l\d noise w />tle fi%1 & cause !m to d>t away1 s we conclude t ! s\nd mu/ h rea*$ !m ?r\gh ! wat]4 ,an ,indian puts 8 e> to ! gr\nd 9 ord] to detect di/ant foot/eps1 because s\nds too fa9t to be he>d ?r\gh ! air are comp>atively cle> :5 transmitt$ ?r\gh ! e>?4 ,a g5tle tapp+ at "o end ( a long table c be di/9ctly he>d at ! opposite end if ! e> is press$ aga9/ ! table2 if ! e> is remov$ f ! wood1 ! s\nd ( tapp+ is mu* fa9t]1 %[+ t wood transmits s\nd m readily ?an air4 ,we see !re=e t s\nd c be transmitt$ to ! e> by solids1 liquids1 or gases4 ,matt] ( any k9d c transmit s\nd to ! e>4 ,! foll[+ exp]im5ts w %[ t matt] is necess>y = transmission4 ,atta* a small toy bell to a glass rod 7,fig4 #aff7 by means ( a rubb] tube & pass ! rod ?r\gh "o ( two op5+s 9 a rubb] cork4 ,ins]t ! cork 9 a /rong flask conta9+ a small quantity ( wat] & %ake ! bell1 not+ ! s\nd produc$4 ,!n heat ! flask1 all[+ ! wat] to boil briskly1 & aft] ! boil+ has cont9u$ = a few m9utes remove ! flame & in/antly close up ! second op5+ by ins]t+ a glass /opp]4 ,n[ %ake ! flask & note t ! s\nd is v mu* fa9t] ?an at fir/4 ,z ! flask 0 w>m$1 air 0 rapidly expell$2 s t :5 ! flask 0 %ak5 ! second "t1 less air 0 pres5t to transmit ! s\nd4 ,if ! glass /opp] is remov$ & ! air is all[$ to re5t] ! flask1 ! l\dness ( ! s\nd imm$iately increases4 ,illu/ration3 ,,fig4 #aff4--,s\nd is c>ri$ by ! air4 ,s9ce ! s\nd ( ! bell gr[s fa9t] z air is remov$1 we inf] t !re w\ld be no s\nd if all ! air 7 remov$ f ! flask2 t is to say1 s\nd _c be transmitt$ ?r\gh empty space or a vacuum4 ,if s\nd is to rea* our e>s1 x mu/ be ?r\gh ! ag5cy ( matt]1 su* z wood1 wat]1 or air1 etc4 #beb4 ,h[ ,s\nd is transmitt$ ?r\gh ,air4 ,we saw 9 ,section #bej t s\nd c always be trac$ to ! motion or vibration ( matt]4 ,x is impossible to conceive ( an object be+ set into sudd5 & cont9u$ motion )\t di/urb+ ! air imm$iately surr\nd+ x4 ,a s\nd+ body always di/urbs & ?r[s into vibration ! air ar\nd x1 & ! air p>ticles :i* receive motion f a s\nd+ body transmit _! motion to neighbor+ p>ticles1 ^! 9 turn to ! next adjac5t p>ticles1 & s on until ! motion has travel$ to v great di/ances4 ,! mann] 9 :i* vibratory motion is transmitt$ by ! atmosph]e mu/ be unusual 9 "*1 s9ce no motion ( ! air is app>5t1 & s9ce 9 ! /illness ( night :5 n a brea? ( air is /irr+1 ! %riek ( a railroad :i/le miles di/ant may be he>d ) p]fect cle>ness4 ,moreov]1 ! mo/ delicate notes ( a viol9 c be he>d 9 ! remote/ corn]s ( a conc]t hall1 :5 n ! slighte/ motion ( ! air c be se5 or felt4 ,9 our /udy ( ! atmosph]e we saw t air c be compress$ & r>efi$2 9 o!r words1 we saw t air is v ela/ic4 ,x c be %[n exp]im5tally t :5ev] an ela/ic body 9 motion comes 9 contact ) a body at re/1 ! mov+ body transf]s its motion to ! second body & !n comes to re/ itself4 ,let two billi>d balls be susp5d$ 9 ! mann] indicat$ 9 ,figure #afg4 ,if "o ( ! balls is drawn aside & is !n all[$ to fall aga9/ ! o!r1 ! second ball is driv5 outw>d to practically ! height f :i* ! fir/ ball fell & ! fir/ ball comes to re/4 ,illu/ration3 ,,fig4 #afg4--;,ela/ic balls4 ,illu/ration3 ,,fig4 #afh4--,susp5d$ billi>d balls4 ,if a numb] ( balls are arrang$ 9 l9e z 9 ,figure #afh or ,figure #afi1 & ! end ball is rais$ & !n all[$ to fall1 or if ,a is pu%$ aga9/ ,c1 ! la/ ball ,b w move outw>d alone1 ) a =ce ne>ly equal to t orig9ally possess$ by ,a & to a di/ance ne>ly equal to t ?r\gh :i* ,a mov$4 ,b !re w be no visible motion ( ! int]v5+ balls4 ,! =ce ( ! mov+ ball ,a is giv5 to ! second ball1 & ! second ball 9 turn gives ! motion to ! ?ird1 & s on ?r\gh\t ! entire numb]1 until ,b is rea*$4 ,b ,b has no ball to give its motion to1 h5ce ,b itself moves outw>d1 & moves ) a =ce ne>ly equal to t orig9ally imp>t$ by ,a & to a di/ance ne>ly equal to t ?r\gh :i* ,a fell4 ,motion at ,a is transmitt$ to ,b )\t any p]ceptible motion ( ! balls ly+ betwe5 ^! po9ts4 ,simil>ly ! p>ticles ( air set into motion by a s\nd+ body imp>t _! motion to ea* o!r1 ! motion be+ transmitt$ onw>d )\t any p]ceptible motion ( ! air itself4 ,:5 ?is motion rea*es ! e>1 x sets ! drum ( ! e> into vibration1 & ^! vibrations are 9 turn transmitt$ to ! auditory n]ves1 :i* int]pret ! motion z s\nd4 ,illu/ration3 ,,fig4 #afi4--;,ela/ic balls transmit motion4 ,illu/ration3 ,,fig4 #agj4--,:5 a ball meets m ?an "o ball1 x divides its motion4 #bec4 ,:y ,s\nd dies away ) ,di/ance4 ,s9ce ! la/ ball ,b is driv5 outw>d ) a =ce ne>ly equal to t possess$ by ,a1 x w\ld seem t ! effect on ! e> drum %\ld be indep5d5t ( di/ance & t a s\nd %\ld be he>d z di/9ctly :5 remote z :5 ne>4 ,b we "k f exp]i5ce t ?is is n true1 because ! m di/ant ! s\rce ( s\nd1 ! fa9t] ! impression2 & f9ally1 if ! di/ance betwe5 ! s\rce ( s\nd & ! he>] becomes too great1 ! s\nd disappe>s entirely & no?+ is he>d4 ,! explanation ( ?is well-kn[n fact is f\nd 9 a fur!r /udy ( ! ela/ic balls 7,fig4 #agj74 ,if ,a hits two balls in/ead ( "o1 ! en]gy possess$ by ,a is giv5 9 "p to "o ball1 & 9 "p to ! o!r1 s t nei!r obta9s ! full am\nt4 ,^! balls1 hav+ ea* receiv$ less ?an ! orig9al en]gy1 h less to transmit2 ea* ( ^! balls 9 turn meets ) o!rs1 & h5ce ! motion becomes m & m di/ribut$1 & di/ant balls receive less & less impetus4 ,! en]gy f9ally giv5 becomes too slight to affect neighbor+ balls1 & ! sy/em comes to re/4 ,?is is :at occurs 9 ! atmosph]e2 a mov+ air p>ticle meets n "o b _m adjac5t air p>ticles1 & ea* ( ^! receives a portion ( ! orig9al en]gy & transmits a portion4 ,:5 ! orig9al di/urbance becomes scatt]$ ov] a l>ge numb] ( air p>ticles1 ! en]gy giv5 to any "o air p>ticle becomes correspond+ly small1 & f9ally ! en]gy becomes s small t fur!r p>ticles are n affect$2 beyond ?is limit ! s\nd _c be he>d4 ,if an air p>ticle transmitt$ motion only to ^? air p>ticles directly 9 l9e ) x1 we %\ld n be able to detect s\nd unless ! e> 7 9 direct l9e ) ! s\rce4 ,! fact t an air p>ticle divides its motion among all p>ticles :i* x t\*es1 t is1 among ^? on ! sides z well z ^? 9 front1 makes x possible to he> s\nd 9 all directions4 ,a good speak] is he>d n only by ^? directly 9 front ( him1 b by ^? on ! side1 & ev5 beh9d him4 #bed4 ,velocity ( ,s\nd4 ,! transmission ( motion f p>ticle to p>ticle does n occur in/antane\sly1 b requires "t4 ,if ! di/ance is %ort1 s t few air p>ticles are involv$1 ! "t requir$ = transmission is v brief1 & ! s\nd is he>d at practically ! in/ant x is made4 ,ord9>ily we are n consci\s t x requires "t = s\nd to travel f its s\rce to our e>s1 because ! di/ance involv$ is too %ort4 ,at o!r times we recognize t !re is a delay2 = example1 ?und] rea*es our e>s aft] ! lightn+ :i* caus$ ! ?und] has completely disappe>$4 ,if ! /orm is ne>1 ! int]val ( "t betwe5 ! lightn+ & ! ?und] is brief1 because ! s\nd does n h f> to travel2 if ! /orm is di/ant1 ! int]val is mu* long]1 correspond+ to ! great] di/ance ?r\gh :i* ! s\nd travels4 ,s\nd does n move in/antane\sly1 b requires "t = its transmission4 ,! report ( a di/ant cannon is he>d aft] ! fla% & smoke are se52 ! report ( a ne> cannon is he>d ! in/ant ! fla% is se54 ,! spe$ ) :i* s\nds travels ?r\gh ! air1 or its velocity1 0 fir/ measur$ by not+ ! int]val 7#ed4f seconds7 :i* elaps$ betwe5 ! fla% ( a cannon & ! s\nd ( ! report4 ,! di/ance ( ! cannon f ! obs]v] 0 measur$ & f\nd to be #fa1jde feet1 & by divid+ ?is di/ance by ! numb] ( seconds1 we f9d t ! di/ance travel$ by s\nd 9 "o second is approximately #aaah feet4 ,high notes & l[ notes1 s(t notes & %rill notes1 all travel at ! same rate4 ,if bass notes travel$ fa/] or sl[] ?an soprano notes1 or if ! delicate tones ( ! viol9 travel$ fa/] or sl[] ?an ! tones ( a drum1 music w\ld be practically impossible1 because at a di/ance f ! s\rce ( s\nd ! v>i\s tones :i* %\ld be 9 unison w\ld be out ( "t--"s arriv+ late1 "s e>ly4 #bee4 ,s\nd ,waves4 ,practically ev]yone kn[s t a hammock hung ) long ropes sw+s or vibrates m sl[ly ?an "o hung ) %ort ropes1 & t a /one susp5d$ by a long /r+ sw+s m sl[ly ?an "o susp5d$ by a %ort /r+4 ,no two rock+ *airs vibrate 9 ! same way unless !y are exactly alike 9 %ape1 size1 & mat]ial4 ,an object :5 di/urb$ vibrates 9 a mann] peculi> to itself1 ! vibration be+ sl[1 z 9 ! case ( ! long-rop$ sw+1 or quick1 z 9 ! case ( ! %ort-rop$ sw+4 ,! "t requir$ = a s+le sw+ or vibration is call$ ! p]iod ( ! body1 & ev]y?+ t c vibrate has a *>act]i/ic p]iod4 ,size & %ape det]m9e to a l>ge degree ! p]iod ( a body2 = example1 a %ort1 ?ick tun+ =k vibrates m rapidly ?an a tall sl5d] =k4 ,illu/ration3 ,,fig4 #aga4--,! two hammocks sw+ diff]5tly4 ,"s tun+ =ks :5 /ruck vibrate s rapidly t ! prongs move back & =? m ?an #ejjj times p] second1 :ile o!r tun+ =ks vibrate s sl[ly t ! vibrations d n exce$ #ej p] second4 ,9 ei!r case ! di/ance ?r\gh :i* ! prongs move is v small & ! p]iod is v %ort1 s t ! eye c seldom detect ! movem5t itself4 ,t ! prongs are 9 motion1 h[ev]1 is se5 by ! action ( a pi? ball :5 br\ght 9 contact ) ! prongs 7see ,section #bej74 ,illu/ration3 ,,fig4 #agb4--,! pit* giv5 out by a =k dep5ds ^u its %ape4 ,! di/urbance creat$ by a vibrat+ body is call$ a wave4 #bef4 ,waves4 ,:ile ! di/urbance :i* travels out f a s\nd+ body is commonly call$ a wave1 x is by no means l ! type ( wave be/ kn[n to u1 namely1 ! wat] wave4 ,if a closely coil$ heavy wire is susp5d$ z 9 ,figure #agc & ! weight is drawn d[n & !n releas$1 ! coil w assume ! appe>ance %[n2 !re is cle>ly an ov]cr[d+ or cond5sation 9 "s places1 & a spread+ out or r>efaction 9 o!r places4 ,! pulse ( cond5sation & r>efaction :i* travels ! l5g? ( ! wire is call$ a wave1 al?\gh x be>s little or no resemblance to ! famili> wat] wave4 ,s\nd waves are simil> to ! waves =m$ 9 ! /ret*$ coil4 ,illu/ration3 ,,fig4 #agc4--,waves 9 a coil$ wire4 ,s\nd waves may be said to consi/ ( a s]ies ( cond5sations & r>efactions1 & ! di/ance betwe5 two consecutive cond5sations & r>efactions may be def9$ z ! wave l5g?4 #beg4 ,h[ ,"o ,s\nd+ ,body produces ,s\nd 9 ,ano!r ,body4 ,9 ,section #bee we saw t any object :5 di/urb$ vibrates 9 a mann] peculi> to itself1--its natural p]iod1--a long-rop$ hammock vibrat+ sl[ly & a %ort-rop$ hammock vibrat+ rapidly4 ,f obs]vation we le>n t x requires b little =ce to cause a body to vibrate 9 its natural p]iod4 ,if a s\nd+ body is ne> a body :i* has ! same p]iod z itself1 ! pulses ( air produc$ by ! s\nd+ body w1 al?\gh v small1 set ! second body into motion & cause x to make a fa9t s\nd4 ,:5 a piano is be+ play$1 we are (t5 />tl$ to f9d t a w9d[ pane or an ornam5t responds to "s note ( ! piano4 ,if two tun+ =ks ( exactly id5tical p]iods 7t is1 ( ! same frequ5cy7 are plac$ on a table z 9 ,figure #agd1 & "o is /ruck s z to give =? a cle> s\nd1 ! second =k w likewise vibrate1 ev5 ?\gh ! two =ks may be sep>at$ by sev]al feet ( air4 ,we c readily see t ! second =k is 9 motion1 al?\gh x has n be5 /ruck1 because x w set 9 motion a pi? ball susp5d$ beside x2 at fir/ ! pi? ball does n move1 !n x moves slightly1 & f9ally b\nces rapidly back & =?4 ,if ! p]iods ( ! two =ks are n id5tical1 b diff] 9 ! slighte/ degree1 ! second =k w n respond to ! fir/ =k1 no matt] h[ long or h[ l\d ! s\nd ( ! fir/ =k4 ,if we suppose t ! =k vibrates #bef times ea* second1 !n #bef g5tle pulses ( air are produc$ ea* second1 & ^!1 travel+ outw>d ?r\gh ! air1 rea* ! sil5t =k & t5d to set x 9 motion4 ,a s+le pulse ( air c\ld n move ! solid1 heavy prongs1 b ! accumulat$ action ( #bef vibrations p] second soon makes itself felt1 & ! second =k beg9s to vibrate1 at fir/ g5tly1 !n gradually /rong]1 & f9ally an audible tone is giv5 =?4 ,illu/ration3 ,,fig4 #agd4--,:5 ! fir/ =k vibrates1 ! second responds4 ,! cumulative p[] ( feeble =ces act+ frequ5tly at def9ite int]vals is se5 9 _m ways 9 ev]yday life4 ,a small boy c easily sw+ a mu* l>g] boy1 provid$ he gives ! sw+ a g5tle pu% 9 ! "r direction e "t x passes him4 ,b he mu/ be c>eful to pu% at ! prop] in/ant1 s9ce o!rwise 8 ef=t does n c\nt = mu*2 if he pu%es =w>d :5 ! sw+ is mov+ backw>d1 he really h9d]s ! motion2 if he waits until ! sw+ has mov$ consid]ably =w>d1 8 pu% c\nts = little4 ,he mu/ pu% at ! prop] in/ant2 t is1 ! way 9 :i* 8 h& moves 9 giv+ ! pu% mu/ correspond exactly ) ! way 9 :i* ! sw+ w\ld naturally vibrate4 ,a v /rik+ exp]im5t c be made by susp5d+ f ! ceil+ a heavy weight & /rik+ ?is weight g5tly at regul>1 prop]ly tim$ int]vals ) a small cork hamm]4 ,soon ! p5dulum1 or weight1 w be set sw++4 ,illu/ration3 ,,fig4 #age4--,! holl[ wood5 box ren=ces ! s\nd4 #beh4 ,borr[$ ,s\nd4 ,picture frames & ornam5ts sometimes buzz & give =? fa9t murmurs :5 a piano or organ is play$4 ,! waves s5t out by a s\nd+ body fall ^u all surr\nd+ objects & by _! repeat$ action t5d to ?r[ ^! bodies into vibration4 ,if ! p]iod ( any "o ( ! objects corresponds ) ! p]iod ( ! s\nd+ body1 ! g5tle b frequ5t impulses affect ! object1 :i* responds by emitt+ a s\nd4 ,if1 h[ev]1 ! p]iods d n correspond1 ! action ( ! s\nd waves is n suffici5tly p[]ful to ?r[ ! object into vibration1 & no s\nd is he>d4 ,bodies :i* respond 9 ?is way are said to be sympa!tic & ! response produc$ is call$ resonance4 ,sea%ells :5 held to ! e> seem to conta9 ! ro> ( ! sea2 ?is is because ! air )9 ! %ell is set into sympa!tic vibrations by "s ext]nal tone4 ,if ! sea%ell 7 held to ! e> 9 an absolutely quiet room1 no s\nd w\ld be he>d1 because !re w\ld be no ext]nal =ces to set into vibration ! air )9 ! %ell4 ,tun+ =ks d n produce /rong tones unless m\nt$ on holl[ wood5 boxes 7,fig4 #age71 ^: size & %ape are s adju/$ t resonance occurs & /r5g!ns ! s\nd4 ,:5 a human be+ talks or s+s1 ! air )9 ! m\? cavity is ?r[n into sympa!tic vibration & /r5g!ns ! o!rwise feeble tone ( ! speak]4 #bei4 ,e*o4 ,if "o %\ts 9 a =e/1 ! s\nd is sometimes he>d a second "t a second or two lat]4 ,?is is because s\nd is reflect$ :5 x /rikes a l>ge ob/ruct+ surface4 ,if ! s\nd waves result+ f ! %\t meet a cliff or a m\nta91 !y are reflect$ back1 & on rea*+ ! e> produce a lat] s5sation ( s\nd4 ,by obs]vation x has be5 f\nd t ! e> _c di/+ui% s\nds :i* are less ?an "o t5? ( a second ap>t2 t is1 if two s\nds foll[ ea* o!r at an int]val less ?an "o t5? ( a second1 ! e> recognizes n two s\nds1 b "o4 ,?is expla9s :y a speak] c be he>d bett] indoors ?an 9 ! op5 air4 ,9 ! av]age build+1 ! walls are s close t ! reflect$ waves h b a %ort di/ance to travel1 & h5ce rea* ! e> at practically ! same "t z ^? :i* come directly f ! speak]4 ,9 ! op51 !re are no reflect+ walls or surfaces1 & ! orig9al s\nd has no ren=cem5t f reflection4 ,if ! reflect$ waves rea* ! e> too late to bl5d ) ! orig9al s\nd1 t is1 come lat] ?an "o t5? ( a second aft] ! fir/ impression1 an e*o is he>d4 ,:at we call ! roll+ ( ?und] is really ! reflection & re-reflection ( ! orig9al ?und] f cl\d & cliff4 ,"s halls are s l>ge t ! reflect$ s\nds cause a confusion ( e*oes1 b ?is difficulty c be less5$ by hang+ drap]ies1 :i* break ! reflection4 #bfj4 ,motion does n always produce ,s\nd4 ,:ile we "k t all s\nd c be trac$ to motion1 we "k equally well t motion does n always produce s\nd4 ,! hammock sw++ 9 ! breeze does n give =? a s\nd2 ! flag float+ 9 ! air does n give =? a s\nd unless bl[n viol5tly by ! w9d2 a c>d mov$ sl[ly ?r\gh ! air does n produce s\nd1 b if ! c>d is mov$ rapidly back & =?1 a s\nd becomes audible4 ,motion1 9 ord] to produce s\nd1 mu/ be rapid2 a ball atta*$ to a /r+ & mov$ sl[ly ?r\gh ! air produces no s\nd1 b ! same ball1 :irl$ rapidly1 produces a di/9ct buzz1 :i* becomes /rong] & /rong] ! fa/] ! ball is :irl$4 #bfa4 ,noise & ,music4 ,:5 ! rapid motions :i* produce s\nd are irregul>1 we he> noise2 :5 ! motions are regul> & def9ite1 we h a musical tone2 ! rattl+ ( c>riage :eels on /ones1 ! ro> ( waves1 ! ru/l+ ( leaves are noise1 n music4 ,9 all ^! illu/rations we h rapid b irregul> motion2 no two /ones /rike ! :eel 9 exactly ! same way1 no two waves produce pulses 9 ! air ( exactly ! same "*1 no two leaves ru/le 9 precisely ! same way4 ,! di/urbances :i* rea* ! e> f c>riage1 waves1 & leaves are irregul> bo? 9 "t & /r5g?1 & irritate ! e>1 caus+ ! s5sation :i* we call noise4 ,! tun+ =k is musical4 ,"h we h rapid1 regul> motion2 vibrations foll[ ea* o!r at p]fectly def9ite int]vals1 & ! air di/urbance produc$ by "o vibration is exactly l ! di/urbance produc$ by a lat] vibration4 ,! s\nd waves :i* rea* ! e> are regul> 9 "t & k9d & /r5g?1 & we call ! s5sation music4 ,to produce noise a body mu/ vibrate 9 su* a way z to give %ort1 quick %ocks to ! air2 to produce music a body mu/ n only imp>t %ort1 quick %ocks to ! air1 b mu/ imp>t ^! %ocks ) un]r+ regul>ity & /r5g?4 ,a flick]+ light irritates ! eye2 a flick]+ s\nd or noise irritates ! e>2 bo? are pa9ful because ( ! sudd5 & abrupt *anges 9 effect :i* !y cause1 ! =m] on ! eye1 ! latt] on ! e>4 ,! only ?+ ess5tial = ! production ( a musical s\nd is t ! waves :i* rea* ! e> %all be rapid & regul>2 x is immat]ial h[ ^! waves are produc$4 ,if a too!d :eel is m\nt$ & sl[ly rotat$1 & a /iff c>d is held aga9/ ! tee? ( ! :eel1 a di/9ct tap is he>d e "t ! c>d /rikes ! :eel4 ,b if ! :eel is rotat$ rapidly1 ! e> ceases to he> ! v>i\s taps & recognizes a deep cont9u\s musical tone4 ,! bl5d+ ( ! individual taps1 occurr+ at regul> int]vals1 has produc$ a su/a9$ musical tone4 ,a simil> result is obta9$ if a c>d is drawn sl[ly & !n rapidly ov] ! tee? ( a comb4 ,illu/ration3 ,,fig4 #agf4--;,a rotat+ disk4 ,t musical tones are due to a succession ( regul>ly tim$ impulses is %[n mo/ cle>ly by means ( a rotat+ disk on :i* are cut two sets ( holes1 ! out] set equally spac$1 & ! inn] set unequally spac$ 7,fig4 #agf74 ,if1 :ile ! disk is rotat+ rapidly1 a tube is held ov] ! outside r[ & air is bl[n ?r\gh ! tube1 a su/a9$ musical tone w be he>d4 ,if1 h[ev]1 ! tube is held1 dur+ ! rotation ( ! disk1 ov] ! inn] r[ ( unequally spac$ holes1 ! musical tone disappe>s1 & a s]ies ( noises take its place4 ,9 ! fir/ case1 ! sep>ate puffs ( air foll[$ ea* o!r regul>ly & bl5d$ into "o tone2 9 ! second case1 ! sep>ate puffs ( air foll[$ ea* o!r at unc]ta9 & irregul> int]vals & ! result 0 noise4 ,s\nd possesses a musical quality only :5 ! waves or pulses foll[ ea* o!r at absolutely regul> int]vals4 #bfb4 ,! ,effect ( ! ,rapidity ( ,motion on ! ,musical ,tone ,produc$4 ,if ! disk is rotat$ s sl[ly t less ?an ab\t #af puffs are produc$ 9 "o second1 only sep>ate puffs are he>d1 & a musical tone is lack+2 if1 on ! o!r h&1 ! disk is rotat$ 9 su* a way t #af puffs or m are produc$ 9 "o second1 ! sep>ate puffs w bl5d toge!r to produce a cont9u\s musical note ( v l[ pit*4 ,if ! spe$ ( ! disk is increas$ s t ! puffs become m frequ5t1 ! pit* ( ! result+ note rises2 & at v high spe$s ! notes produc$ become s %rill & pi]c+ z to be disagreeable to ! e>4 ,if ! spe$ ( ! disk is less5$1 ! pit* falls correspond+ly2 & if ! spe$ aga9 becomes s l[ t less ?an #af puffs are =m$ p] second1 ! su/a9$ s\nd disappe>s & a s]ies ( int]mitt5t noises is produc$4 #bfc4 ,! ,pit* ( a ,note4 ,by means ( an app>atus call$ ! sir51 x is possible to calculate ! numb] ( vibrations produc+ any giv5 musical note1 su*1 = example1 z middle ,c on ! piano4 ,if air is =c$ cont9u\sly aga9/ ! disk z x rotates1 a s]ies ( puffs w be he>d 7,fig4 #agg74 ,if ! disk turns fa/ en\gh1 ! puffs bl5d into a musical s\nd1 ^: pit* rises high] & high] z ! disk moves fa/] & fa/]1 & produces m & m puffs ea* second4 ,! in/rum5t is s con/ruct$ t clockwork at ! top regi/]s ! numb] ( revolutions made by ! disk 9 "o second4 ,! numb] ( holes 9 ! disk multipli$ by ! numb] ( revolutions a second gives ! numb] ( puffs ( air produc$ 9 "o second4 ,if we wi% to f9d ! numb] ( vibrations :i* correspond to middle ,c on ! piano1 we increase ! spe$ ( ! disk until ! note giv5 =? by ! sir5 agrees ) middle ,c z s\nd$ on ! piano1 z ne>ly z ! e> c judge2 we !n calculate ! numb] ( puffs ( air :i* took place ea* second at t p>ticul> spe$ ( ! disk4 ,9 ?is way we f9d t middle ,c is due to ab\t #bef vibrations p] second2 t is1 a piano /r+ mu/ vibrate #bef times p] second 9 ord] = ! resultant note to be ( pit* middle ,c4 ,9 a simil> mann] we det]m9e ! foll[+ frequ5cies3-- d re mi fa sol la si d ,c ,d ,e ,f ,g ,a ,b ,c' #bef #bhh #cbj #cda #chd #dbg #dhj #eab ,illu/ration3 ,,fig4 #agg4--;,a sir54 ,! pit* ( pianos1 f ! l[e/ bass note to ! v highe/ treble1 v>ies f #bg to ab\t #cejj vibrations p] second4 ,no human voice1 h[ev]1 has s great a range ( tone2 ! highe/ soprano notes ( wom5 correspond to b #ajjj vibrations a second1 & ! deepe/ bass ( m5 falls b to #hj vibrations a second4 ,:ile ! human voice is limit$ 9 its production ( s\nd1--r>ely fall+ bel[ #hj vibrations a second & r>ely exce$+ #ajjj vibrations a second1--! e> is by no means limit$ to t range 9 he>+4 ,! *irrup ( a sp>r[1 ! %rill s\nd ( a cricket1 & ! pi]c+ %rieks ( a locomotive are due to f> great] frequ5cies1 ! numb] ( vibrations at times equal+ #ch1jjj p] second or m4 #bfd4 ,! ,musical ,scale4 ,:5 we talk1 ! pit* ( ! voice *anges con/antly & adds v>iety & beauty to conv]sation2 a speak] ^: tone1 or pit*1 rema9s too con/ant is monoton\s & dull1 no matt] h[ brilliant 8 ?\ghts may be4 ,:ile ! pit* ( ! voice *anges con/antly1 ! *anges are normally gradual & slight1 & ! diff]5t tones m]ge into ea* o!r imp]ceptibly4 ,9 music1 h[ev]1 !re is a well-def9$ int]val betwe5 ev5 consecutive notes2 = example1 9 ! musical scale1 middle ,c 7d7 ) #bef vibrations is foll[$ by ,d 7re7 ) #bhh vibrations1 & ! int]val betwe5 ^! notes is %>p & well m>k$1 ev5 to an untra9$ e>4 ,! int]val betwe5 two notes is def9$ z ! ratio ( ! frequ5cies2 h5ce1 ! int]val betwe5 ,c & ,d 7d & re7 is #bhh_/bef1 or #i_/h4 ,ref]r+ to ,section #bfc1 we see t ! int]val betwe5 ,c & ,e is #cbj_/bef1 or #e_/d1 & ! int]val betwe5 ,c & ,c' is #eab_/bef1 or #b2 ! int]val betwe5 any note & its octave is #b4 ,! successive notes 9 "o octave ( ! musical scale are relat$ z foll[s3-- ,key ( ,c ,c ,d ,e ,f ,g ,a ,b ,c' ,no4 ( vibrations p] sec4 #bef #bhh #cbj #cda #chd #dbg #dhj #eab ,int]val #i_/h #e_/d #d_/c #c_/b #e_/c #ae_/h #b ,! int]vals ( ,f & ,a are n /rictly #d_/c & #e_/c1 b are ne>ly s2 if ,f made #cda4c vibrations p] second in/ead ( #cda2 & if ,a made #dbf4f in/ead ( #dbg1 !n ! int]vals w\ld be exactly #d_/c & #e_/c4 ,s9ce ! real diff]5ce is s slight1 we c assume ! simpl] ratios )\t appreciable error4 ,any eight notes ^: frequ5cies are 9 ! ratio ( #i_/h1 #e_/d1 etc41 w :5 play$ 9 succession give ! famili> musical scale2 = example1 ! deepe/ bass voice />ts a musical scale ^: notes h ! frequ5cies #hj1 #ij1 #ajj1 #ajg1 #abj1 #acc1 #aej1 #afj1 b ! int]vals "h are id5tical ) ^? ( a high] scale2 ! int]val betwe5 ,c & ,d1 #hj & #ij1 is #i_/h1 j z x 0 be=e :5 ! frequ5cies 7 mu* great]2 t is1 #bef & #bhh4 ,9 s++ ,home1 ,sweet ,home1 = example1 a bass voice may />t ) a note vibrat+ only #acb times a second2 :ile a t5or may />t at a high] pit*1 ) a note vibrat+ #aih times p] second1 & a soprano w\ld probably take a mu* high] range /ill1 ) an initial frequ5cy ( #ebh vibrations p] second4 ,b no matt] :]e ! voices />t1 ! int]vals are always id5tical4 ,! air z sung by ! bass voice w\ld be repres5t$ by ,a4 ,! air z sung by ! t5or voice w\ld be repres5t$ by ,b4 ,! air z sung by ! soprano voice w\ld be repres5t$ by ,c4 ,illu/ration3 ,,fig4 #agh4--;,a song z sung by ?ree voices ( diff]5t pit*4 ,,*apt] ,,xxviii ,,musical ,,in/rum5ts #bfe4 ,musical in/rum5ts maybe divid$ into ?ree gr\ps accord+ to ! diff]5t ways 9 :i* _! tones are produc$3-- ,fir/4 ,! /r+$ in/rum5ts 9 :i* s\nd is produc$ by ! vibration ( /ret*$ /r+s1 z 9 ! piano1 viol91 guit>1 m&ol94 ,second4 ,! w9d in/rum5ts 9 :i* s\nd is produc$ by ! vibrations ( def9ite columns ( air1 z 9 ! organ1 flute1 cornet1 trombone4 ,?ird4 ,! p]cussion in/rum5ts1 9 :i* s\nd is produc$ by ! motion ( /ret*$ membranes1 z 9 ! drum1 or by ! motion ( metal disks1 z 9 ! tamb\r9es & cymbals4 #bff4 ,/r+$ ,in/rum5ts4 ,if ! lid ( a piano is op5$1 num]\s wires are se5 )92 "s long1 "s %ort1 "s co>se1 "s f9e4 ,b5ea? ea* wire is a small felt hamm] connect$ ) ! keys 9 su* a way t :5 a key is press$1 a /r+ is /ruck by a hamm] & is ?r[n into vibration1 !reby produc+ a tone4 ,if we press ! l[e/ key1 t is1 ! key giv+ =? ! l[e/ pit*1 we see t ! longe/ wire is /ruck & set into vibration2 if we press ! highe/ key1 t is1 ! key giv+ ! highe/ pit*1 we see t ! %orte/ wire is /ruck4 ,9 addition1 x is se5 t ! %ort wires :i* produce ! high tones are f9e1 :ile ! long wires :i* produce ! l[ tones are co>se4 ,! %ort] & f9] ! wire1 ! high] ! pit* ( ! tone produc$4 ,! long] & co>s] ! wire1 ! l[] ! pit* ( ! tone produc$4 ,illu/ration3 ,,fig4 #agi4--,piano wires se5 f ! back4 ,! con/ant /rik+ ( ! hamm]s aga9/ ! /r+s /ret*es & loos5s !m & alt]s _! pit*2 = ?is reason ea* /r+ is fa/5$ to a screw :i* c be turn$ s z to tight5 ! /r+ or to loos5 x if necess>y4 ,! tun+ ( ! piano is ! adju/m5t ( ! /r+s s t ea* %all produce a tone ( ! "r pit*4 ,:5 ! /r+s are tight5$1 ! pit* rises2 :5 ! /r+s are loos5$1 ! pit* falls4 ,:at has be5 said ( ! piano applies z well to ! viol91 guit>1 & m&ol94 ,9 ! latt] in/rum5ts ! /r+s are few 9 numb]1 g5]ally f\r1 z aga9/ eighty-eight 9 ! piano2 ! hamm] ( ! piano is replac$ 9 ! viol9 by ! b[1 & 9 ! guit> by ! f+]s2 v>y+ pit*es on any "o /r+ are obta9$ by slid+ a f+] ( ! left h& along ! wire1 & ?us alt]+ its l5g?4 ,frequ5t tun+ is necess>y1 because ! f9e adju/m5ts are easily di/urb$4 ,! piano is ! be/ protect$ ( all ! /r+$ in/rum5ts1 be+ inclos$ by a heavy framework1 ev5 :5 9 use4 ,illu/ration3 ,,fig4 #ahj4--;,front view ( an op5 piano4 #bfg4 ,/r+s & _! ,tones4 ,fa/5 a viol9 /r+ to a wood5 frame or box1 z %[n 9 ,figure #aha1 /ret*+ x by means ( "s conv5i5t weight2 !n lay a y>d/ick along ! box 9 ord] t ! l5g?s may be det]m9$ accurately4 ,if ! /ret*$ /r+ is pluck$ ) ! f+]s or b[$ ) ! viol9 b[1 a cle> musical s\nd ( def9ite pit* w be produc$4 ,n[ divide ! /r+ into two equal p>ts by ins]t+ ! bridge midway betwe5 ! two ends2 & pluck ei!r half z be=e4 ,! note giv5 =? is ( a decid$ly high] pit*1 & if by means ( ! sir5 we comp>e ! pit*es 9 ! two cases1 we f9d t ! note s\nd$ by ! half wire is ! octave ( ! note s\nd$ by ! entire wire2 ! frequ5cy has be5 d\bl$ by halv+ ! l5g?4 ,if n[ ! bridge is plac$ s t ! /r+ is divid$ into two unequal portions su* z #a3c & #b3c1 & ! %ort] portion is pluck$1 ! pit* w be /ill high]2 ! %ort] ! l5g? pluck$1 ! high] ! pit* produc$4 ,?is movable bridge corresponds to ! f+] ( ! viol9i/2 ! f+] slides back & =? along ! /r+1 ?us *ang+ ! l5g? ( ! b[$ portion & produc+ v>iations 9 pit*4 ,illu/ration3 ,,fig4 #aha4--,! l5g? ( a /r+ influ5ces ! pit*4 ,illu/ration3 ,,fig4 #ahb4--,only "o half ( ! /r+ is b[$1 b bo? halves vibrate4 ,if !re 7 b "o /r+1 only "o pit* c\ld be s\nd$ at any "o "t2 ! additional /r+s ( ! viol9 all[ ( ! simultane\s production ( sev]al tones4 #bfh4 ,! ,fre$om ( a ,/r+4 ,"s /r+$ in/rum5ts give =? tones :i* are cle> & sweet1 b )al ?9 & lack+ 9 ri*ness & fullness4 ,! tones s\nd$ by two diff]5t /r+s may agree 9 pit* & l\dness & yet produce q diff]5t effects on ! e>1 because 9 "o case ! tone may be mu* m pleas+ ?an 9 ! o!r4 ,! explanation ( ?is is1 t a /r+ may vibrate 9 a numb] ( diff]5t ways4 ,t\* ! middle ( a wire ) ! f+] or a p5cil 7,fig4 #ahb71 ?us sep>at+ x into two portions & draw a viol9 b[ across ! c5t] ( ei!r half4 ,only "o half ( ! entire /r+ is /ruck1 b ! motion ( ?is half is imp>t$ to ! o!r half & ?r[s x into simil> motion1 & if a t9y ,a-%ap$ piece ( pap] or rid] is plac$ ^u ! unb[$ half1 x is hurl$ (f4 ,illu/ration3 ,,fig4 #ahc4--,! /r+ vibrates 9 ?ree portions4 ,if ! wire is t\*$ at a di/ance ( "o ?ird its l5g? & a b[ is drawn across ! middle ( ! small] portion1 ! /r+ w vibrate 9 ?ree p>ts2 we _c always see ^! v>i\s motions 9 diff]5t p>ts ( ! /r+1 b we "k ( _! exi/5ce ?r\gh ! action ( ! rid]s4 ,simil>ly1 t\*+ ! wire "o f\r? ( its l5g? f an end makes x vibrate 9 f\r segm5ts2 t\*+ x "o fif? ( its l5g? makes x vibrate 9 five segm5ts4 ,9 ! fir/ case1 ! /r+ vibrat$ z a :ole /r+ & also z two /r+s ( half ! l5g?2 h5ce1 ?ree tones mu/ h be5 giv5 out1 "o tone due to ! entire /r+ & two tones due to ! segm5ts4 ,b we saw 9 ,section #bfg t halv+ ! l5g? ( a /r+ d\bles ! pit* ( ! result+ tone1 & produces ! octave ( ! orig9al tone2 h5ce a /r+ vibrat+ z 9 ,figure #ahc gives =? ?ree tones1 "o ( :i* is ! fundam5tal tone ( ! /r+1 & two ( :i* are ! octave ( ! fundam5tal tone4 ,h5ce1 ! vibrat+ /r+ produces two s5sations1 t ( ! fundam5tal note & ( its octave4 ,illu/ration3 ,,fig4 #ahd4--,:5 a /r+ vibrates z a :ole1 x gives out ! fundam5tal note4 ,:5 a /r+ is pluck$ 9 ! middle )\t be+ held1 x vibrates simply z a :ole 7,fig4 #ahd71 & gives =? b "o note2 ?is is call$ ! fundam5tal4 ,if ! /r+ is made to vibrate 9 two p>ts1 x gives =? two notes1 ! fundam5tal1 & a note "o octave high] ?an ! fundam5tal2 ?is is call$ ! fir/ ov]tone4 ,:5 ! /r+ is made to move z 9 ,figure #ahc1 ?ree di/9ct motions are call$ =?1 ! motion ( ! entire /r+1 ! motion ( ! portion pluck$1 & ! motion ( ! rema9+ unpluck$ portion ( ! /r+4 ,"h1 naturally1 diff]5t tones arise1 correspond+ to ! diff]5t modes ( vibration4 ,! note produc$ by ! vibration ( "o ?ird ( ! orig9al /r+ is call$ ! second ov]tone4 ,! above exp]im5ts %[ t a /r+ is able to vibrate 9 a numb] ( diff]5t ways at ! same "t1 & to emit simultane\sly a numb] ( diff]5t tones2 also t ! result+ complex s\nd consi/s ( ! fundam5tal & "o or m ov]tones1 & t ! numb] ( ov]tones pres5t dep5ds ^u h[ & :]e ! /r+ is pluck$4 ,illu/ration3 ,,fig4 #ahe4--;,a /r+ c vibrate 9 a numb] ( diff]5t ways simultane\sly1 & c produce diff]5t notes simultane\sly4 #bfi4 ,! ,value ( ,ov]tones4 ,! pres5ce ( ov]tones det]m9es ! quality ( ! s\nd produc$4 ,if ! /r+ vibrates z a :ole m]ely1 ! tone giv5 out is simple1 & seems dull & *>act]less4 ,if1 on ! o!r h&1 x vibrates 9 su* a way t ov]tones are pres5t1 ! tone giv5 =? is full & ri* & ! s5sation is pleas+4 ,a tun+ =k _c vibrate 9 m ?an "o way1 & h5ce has no ov]tones1 & its tone1 :ile cle> & sweet1 is f> less pleas+ ?an ! same note produc$ by a viol9 or piano4 ,! untra9$ e> is n consci\s ( ov]tones & recognizes only ! /rong dom9ant fundam5tal4 ,! ov]tones bl5d 9 ) ! fundam5tal & are s inconspicu\sly pres5t t we d n realize _! exi/5ce2 x is only :5 !y are abs5t t we become aw>e ( ! beauty :i* !y add to ! music4 ,a song play$ on tun+ =ks in/ead ( on /r+s w\ld be lifeless & unsatisfy+ because ( ! abs5ce ( ov]tones4 ,x is n necess>y to hold f+] or p5cil at ! po9ts #a3c1 #a3d1 etc41 9 ord] to cause ! /r+ to vibrate 9 v>i\s ways2 if a /r+ is m]ely pluck$ or b[$ at ^? places1 ! result w be ! same4 ,x is important to rememb] t no matt] :]e a /r+ ( def9ite l5g? is b[$1 ! note mo/ di/9ctly he>d w be ! fundam5tal2 b ! quality ( ! emitt$ tone w v>y ) ! b[+4 ,= example1 if a /r+ is b[$ 9 ! middle1 ! effect w be f> less pleas+ ?an ?\gh x 7 b[$ ne> ! end4 ,9 ! piano1 ! hamm]s are arrang$ s z to /rike ne> "o end ( ! /r+1 at a di/ance ( ab\t #a3g to #a3i2 & h5ce a l>ge numb] ( ov]tones comb9e to ren=ce & enri* ! fundam5tal tone4 #bgj4 ,! ,individuality ( ,in/rum5ts4 ,x has be5 %[n t a piano /r+ :5 /ruck by a hamm]1 or a viol9 /r+ :5 b[$1 or a m&ol9 /r+ :5 pluck$1 vibrates n only z a :ole1 b also 9 segm5ts1 & z a result gives =? n a simple tone1 z we are accu/om$ to ?9k1 b a v complex tone consi/+ ( ! fundam5tal & "o or m ov]tones4 ,if ! /r+ ^: fundam5tal note is l[] ,c 7#abh vibrations p] second7 is ?r[n into vibration1 ! tone produc$ may conta91 9 addition to ! prom95t fundam5tal1 any "o or m ( ! foll[+ ov]tones3 ,c'1 ,g''1 ,c''1 ,e''1 ,c'''1 etc4 ,! numb] ( ov]tones actually pres5t dep5ds ^u a v>iety ( circum/ances3 9 ! piano1 x dep5ds l>gely ^u ! location ( ! hamm]2 9 ! viol91 ^u ! place & mann] ( b[+4 ,me*anical diff]5ces 9 con/ruction acc\nt = prom95t & num]\s ov]tones 9 "s in/rum5ts & = feeble & few ov]tones 9 o!rs4 ,! oboe1 = example1 is s con/ruct$ t only ! high ov]tones are pres5t1 & h5ce ! s\nd gives a pung5t effect2 ! cl>9et is s con/ruct$ t ! ev5-numb]$ ov]tones are kill$1 & ! pres5ce ( only odd-numb]$ ov]tones gives individuality to ! in/rum5t4 ,9 ^! two in/rum5ts we h vibrat+ air columns in/ead ( vibrat+ /r+s1 b ! laws :i* gov]n vibrat+ /r+s are applicable to vibrat+ columns ( air1 z we %all see lat]4 ,x is really ! pres5ce or abs5ce ( ov]tones :i* enables u to di/+ui% ! note ( ! piano f t ( ! viol91 flute1 or cl>9et4 ,if ov]tones c\ld be elim9at$1 !n middle ,c1 or any o!r note on ! piano1 w\ld be indi/+ui%able f t same note s\nd$ on any o!r in/rum5t4 ,! fundam5tal note 9 e in/rum5t is ! same1 b ! ov]tones v>y ) ! in/rum5t & l5d individuality to ea*4 ,! pres5ce ( high ov]tones 9 ! oboe & ! pres5ce ( odd-numb]$ ov]tones 9 ! cl>9et enable u to di/+ui% )\t fail ! s\nds giv5 out by ^! in/rum5ts4 ,! ri*ness & individuality ( an in/rum5t are due1 n only to ! ov]tones :i* accompany ! fundam5tal1 b also to ! =c$ vibrations ( ! inclos+ case1 or ( ! s\nd+ bo>d4 ,if a vibrat+ tun+ =k is held 9 ! h&1 ! s\nd w be inaudible except to ^? q ne>2 if1 h[ev]1 ! base ( ! =k is held aga9/ ! table1 ! s\nd is greatly int5sifi$ & becomes pla9ly audible ?r\gh\t ! room4 ,! vibrations ( ! =k are transmitt$ to ! table top & ?r[ x into vibrations simil> to its own1 & ^! additional vibrations int5sify ! orig9al s\nd4 ,any =k1 no matt] :at its frequ5cy1 c =ce ! surface ( ! table into vibration1 & h5ce ! s\nd ( any =k w be int5sifi$ by contact ) a table or box4 ,?is is equally true ( /r+s2 if /ret*$ betwe5 two po/s & b[$1 ! s\nd giv5 out by a /r+ is feeble1 b if /ret*$ ov] a s\nd+ bo>d1 z 9 ! piano1 or ov] a wood5 %ell1 z 9 ! viol91 ! s\nd is int5sifi$4 ,any note ( ! in/rum5t w =ce ! s\nd+ body to vibrate1 ?us ren=c+ ! volume ( s\nd1 b "s tones1 or modes ( vibration1 d ?is m easily ?an o!rs1 & :ile ! s\nd+ bo>d or %ell always responds1 x responds 9 v>y+ degree4 ,"h aga9 we h n only enri*m5t ( s\nd b also individuality ( in/rum5ts4 #bga4 ,! ,k9ds ( ,/r+$ ,in/rum5ts4 ,/r+$ in/rum5ts may be gr\p$ 9 ! foll[+ ?ree classes3-- a4 ,in/rum5ts 9 :i* ! /r+s are set into motion by hamm]s--piano4 b4 ,in/rum5ts 9 :i* ! /r+s are set into motion by b[+--viol91 viola1 violoncello1 d\ble bass4 c4 ,in/rum5ts 9 :i* ! /r+s are set into motion by pluck+--h>p1 guit>1 m&ol94 ,illu/ration3 ,,fig4 #ahf4--a1 viol92 #b1 viola2 #c1 violoncello2 #d1 d\ble bass4 a4 ,! piano is too well kn[n to ne$ comm5t4 ,9 pass+1 x may be m5tion$ t 9 ! con/ruction ( ! mod]n conc]t piano approximately #dj1jjj sep>ate pieces ( mat]ial are us$4 ,! l>ge numb] ( pieces is due1 p>tly1 to ! fact t ! s+le /r+ correspond+ to any "o key is usually replac$ by no less ?an ?ree or f\r simil> /r+s 9 ord] t great] volume ( s\nd may be obta9$4 ,! hamm] connect$ to a key /rikes f\r or m /r+s in/ead ( "o1 & h5ce produces a great] volume ( tone4 b4 ,! viola is l>g] ?an ! viol91 has heavi] & ?ick] /r+s1 & is pit*$ to a l[] key2 9 all o!r respects ! two are simil>4 ,! violoncello1 because ( ! l5g? & ?ickness ( its /r+s1 is pit*$ a :ole octave l[] ?an ! viol92 o!rwise x is simil>4 ,! unusual l5g? & ?ickness ( ! /r+s ( ! d\ble bass make x produce v l[ notes1 s t x is ord9>ily look$ ^u z ! bass voice ( ! or*e/ra4 c4 ,! h>p has always be5 consid]$ "o ( ! mo/ pleas+ & p]fect ( musical in/rum5ts4 ,"h ! skill$ p]=m] has absolutely free scope = 8 g5ius1 because 8 f+]s c pluck ! /r+s at w & h5ce regulate ! ov]tones1 & 8 feet c regulate at w ! t5sion1 & h5ce ! pit* ( ! /r+s4 ,guit> & m&ol9 are agreeable in/rum5ts = amateurs1 b are nev] us$ 9 or*e/ral music4 ,illu/ration3 ,,fig4 #ahg4--;,a h>p4 #bgb4 ,w9d ,in/rum5ts4 ,9 ! s-call$ w9d in/rum5ts1 s\nd is produc$ by vibrat+ columns ( air inclos$ 9 tubes or pipes ( diff]5t l5g?s4 ,! air column is ?r[n into vibration ei!r directly1 by bl[+ across a n>r[ op5+ at "o end ( a pipe z 9 ! case ( ! :i/le1 or indirectly1 by excit+ vibrations 9 a ?9 /rip ( wood or metal1 call$ a re$1 :i* 9 turn communicates its vibrations to ! air column )94 ,! %ort] ! air column1 ! high] ! pit*4 ,?is agrees ) ! law ( vibrat+ /r+s :i* gives high pit*es = %ort l5g?s4 ,illu/ration3 ,,fig4 #ahh4--,op5 organ pipes ( diff]5t pit*4 ,! pit* ( ! s\nd emitt$ by a column ( air vibrat+ )9 a pipe v>ies accord+ to ! foll[+ laws3 #a4 ,! %ort] ! pipe1 ! high] ! pit*4 #b4 ,! pit* ( a note emitt$ by an op5 pipe is "o octave high] ?an t ( a clos$ pipe ( equal l5g?4 #c4 ,air columns vibrate 9 segm5ts j z d /r+s1 & ! tone emitt$ by a pipe ( giv5 l5g? is complex1 consi/+ ( ! fundam5tal & "o or m ov]tones4 ,! great] ! numb] ( ov]tones pres5t1 ! ri*] ! tone produc$4 #bgc4 ,h[ ! ,v>i\s ,pit*es are ,produc$4 ,) a pipe ( fix$ l5g?1 = example1 ! cl>9et 7,fig4 #ahi1 #a71 diff]5t pit*es are obta9$ by press+ keys :i* op5 holes 9 ! tube & ?us %ort5 or l5g!n ! vibrat+ air column & produce a rise or fall 9 pit*4 ,*anges 9 pit* are also produc$ by v>iation 9 ! play]'s brea?+4 ,by bl[+ h>d or g5tly1 ! numb] ( vibrations ( ! re$ is increas$ or decreas$ & h5ce ! pit* is alt]$4 ,illu/ration3 ,,fig4 #ahi--a1 cl>9et2 #b1 oboe2 #c1 flute4 ,9 ! oboe 7,fig4 #ahi1 #b7 ! vibrat+ air column is set into motion by means ( two ?9 pieces ( wood or metal plac$ 9 ! m\?piece ( ! tube4 ,v>iations 9 pit* are produc$ z 9 ! cl>9et by means ( /ops & v>i$ brea?+4 ,9 ! flute1 ! air is set into motion by direct bl[+ f ! m\?1 z is done1 = in/ance1 :5 we bl[ into a bottle or key4 ,! s\nd giv5 out by organ pipes is due to air bl[n across a %>p edge at ! op5+ ( a n>r[ tube4 ,! air =c$ across ! %>p edge is ?r[n into vibration & communicates its vibration to ! air )9 ! organ pipe4 ,= diff]5t pit*es1 pipes ( diff]5t l5g?s are us$3 = v l[ pit*es long1 clos$ pipes are us$2 = v high pit*es %ort1 op5 pipes are us$4 ,! me*anism ( ! organ is su* t press+ a key all[s ! air to ru% into ! communicat+ pipe & a s\nd is produc$ *>act]i/ic ( ! l5g? ( ! pipe4 ,illu/ration3 ,,fig4 #aij4--a1 horn2 #b1 trumpet2 #c1 trombone4 ,illu/ration3 ,,fig4 #aia4--a1 kettl$rum2 #b1 bass drum2 #c1 cymbals4 ,illu/ration3 ,,fig4 #aib4--,! seat+ arrangem5t ( ! ,philadelphia or*e/ra4 ,9 ! brass w9d in/rum5ts su* z horn1 trombone1 & trumpet1 ! lips ( ! play] vibrate & excite ! air )94 ,v>y+ pit*es are obta9$ p>tly by ! v>y+ w9d pressure ( ! musician2 if he brea!s fa/1 ! pit* rises2 if he brea!s sl[ly1 ! pit* falls4 ,all ( ^! in/rum5ts1 h[ev]1 except ! trombone possess "s valves :i*1 on be+ press$1 v>y ! l5g? ( ! tube & alt] ! pit* accord+ly4 ,9 ! trombone1 valves are replac$ by a section :i* slides 9 & out & %ort5s or l5g!ns ! tube4 #bgd4 ,! ,p]cussion ,in/rum5ts4 ,! p]cussion in/rum5ts1 includ+ kettl$rums1 bass drums1 & cymbals1 are ! lea/ important ( all ! musical in/rum5ts2 & are usually ( s]vice m]ely 9 add+ to ! excitem5t & g5]al effect ( an or*e/ra4 ,9 or*e/ral music ! v>i\s in/rum5ts are gr\p$ some:at z %[n 9 ,figure #aib4 ,,*apt] ,,xxix ,,speak+ ,,& ,,he>+ ,illu/ration3 ,,fig4 #aic4--,! vibration ( ! vocal cords produces ! s\nd ( ! human voice4 #bge4 ,spee*4 ,! human voice is ! mo/ p]fect ( musical in/rum5ts4 ,)9 ! ?roat1 two ela/ic b&s are atta*$ to ! w9dpipe at ! place commonly call$ ,adam's apple2 ^! flexible b&s h receiv$ ! "n ( vocal cords1 s9ce by _! vibration all spee* is produc$4 ,9 ord9>y brea?+1 ! cords are loose & are sep>at$ by a wide op5+ ?r\gh :i* air ent]s & leaves ! lungs4 ,:5 we wi% to speak1 muscul> ef=t /ret*es ! cords1 draws !m clos] toge!r1 & r$uces ! op5+ betwe5 !m to a n>r[ slit1 z 9 ! case ( ! organ pipe4 ,if air f ! lungs is s5t ?r\gh ! n>r[ slit1 ! vocal cords or b&s are ?r[n into rapid vibration & produce s\nd4 ,! pit* ( ! s\nd dep5ds ^u ! t5sion ( ! /ret*$ membranes1 & s9ce ?is c be alt]$ by muscul> action1 ! voice c be modulat$ at w4 ,9 times ( excitem5t1 :5 ! muscles ( ! body 9 g5]al are 9 a /ate ( great t5sion1 ! pit* is likely to be uncommonly high4 ,wom5's voices are high] ?an m5's because ! vocal cords are %ort] & f9]2 ev5 ?\gh muscul> t5sion is relax$ & ! cords are made loos]1 ! pit* ( a woman's voice does n fall s l[ z t ( a man's voice s9ce 8 cords are naturally mu* long] & co>s]4 ,! diff]5ce betwe5 a soprano & an alto voice is m]ely "o ( l5g? & t5sion ( ! vocal cords4 ,successful s++ is possible only :5 ! vocal cords are readily flexible & :5 ! s+] c supply a /eady1 cont9u\s bla/ ( air ?r\gh ! slit betwe5 ! cords4 ,! ho>s5ess :i* frequ5tly accompanies cold 9 ! head is due to ! ?ick5+ ( ! muc\s membrane & to ! fill+ up ( ! slit ) mucus1 because :5 ?is happ5s1 ! vocal cords _c vibrate prop]ly4 ,! s\nds produc$ by ! vocal cords are trans=m$ into spee* by ! help ( ! tongue & lips1 :i* modify ! %ape ( ! m\? cavity4 ,"s ( ! l[] animals h a speak+ app>atus simil> to our own1 b !y _c p]fectly trans=m s\nd into spee*4 ,! birds use _! vocal cords to beautiful advantage 9 s++1 f> surpass+ u 9 _m ways1 b ! p[] ( spee* is lack+4 #bgf4 ,! ,e>4 ,! pulses creat$ 9 ! air by a s\nd+ body are receiv$ by ! e> & ! impulses :i* !y imp>t to ! auditory n]ve pass to ! bra9 & we become consci\s ( a s\nd4 ,! e> is capable ( m>vel\s discrim9ation & accuracy4 ,9 ord] to =m an idea ( ! ext5t ( ?is p[] imag9e an auditor 9 a l>ge music hall :]e a full b& & *orus are p]=m+4 ,"h1 !re are s\nds m+l$ toge!r ( all v>ieties ( pit*1 l\dness1 & quality2 /r+$ in/rum5ts1 wood in/rum5ts1 brass in/rum5ts1 & voices1 ( _m diff]5t k9ds4 ,& 9 addition to ^! !re may be all sorts ( accid5tal & irregul> s\nds & noises1 su* z ! trampl+ & %uffl+ ( feet1 ! hum ( voices1 ! ru/le ( dress1 ! creak+ ( doors1 & _m o!rs4 ,n[ x mu/ be rememb]$ t ! only means ! e> has ( becom+ aw>e ( ^! simultane\s s\nds is by ! cond5sations & r>efactions :i* rea* x2 & yet :5 ! s\nd wave meets ! n]ves1 ! n]ves s+le out ea* individual elem5t1 & convey to ! m9d ( ! he>]1 n only ! tones & notes ( e in/rum5t 9 ! or*e/ra1 b ! "* ( e accid5tal noise2 & almo/ z di/9ctly z if ea* s+le tone or noise 7 he>d alone4--,,pole4 ,illu/ration3 ,,fig4 #aid4--,! e>4 #bgg4 ,! ,/ructure ( ! ,e>4 ,! ext]nal portion ( ! e> acts z a funnel = cat*+ s\nd waves & lead+ !m into ! canal1 :]e !y /rike ^u ! e> drum1 or tympanic membrane1 & ?r[ x into vibration4 ,unless ! e> drum is v flexible !re _c be p]fect response to ! s\nd waves :i* fall ^u x2 = ?is reason1 ! gl&s ( ! canal secrete a wax :i* moi/5s ! membrane & keeps x flexible4 ,ly+ directly back ( ! tympanic membrane is a cavity fill$ ) air :i* ent]s by ! ,eu/a*ian tube2 f ! ?roat air ent]s ! ,eu/a*ian tube1 moves along x1 & passes into ! e> cavity4 ,! dull crackl+ noise notic$ 9 ! e> :5 "o swall[s is due to ! entrance & exit ( air 9 ! tube4 ,sev]al small bones /ret* across ! upp] portion ( ! cavity & make a bridge1 s to speak1 f ! e> drum to ! f> wall ( ! cavity4 ,x is by means ( ^! ?ree bones t ! vibrations ( ! e> drum are transmitt$ to ! inn] wall ( ! cavity4 ,beh9d ! fir/ cavity is a second cavity s complex & irregul> t x is call$ ! labyr9? ( ! e>4 ,?is labyr9? is fill$ ) a fluid 9 :i* are spread out ! delicate s5sitive fib]s ( ! auditory n]ves2 & x is to ^! t ! vibrations mu/ be transmitt$4 ,suppose a note ( #hjj vibrations p] second is sung4 ,!n #hjj pulses ( air w rea* ! e> ea* second1 & ! e> drum1 be+ flexible1 w respond & w vibrate at ! same rate4 ,! vibration ( ! e> drum w be transmitt$ by ! ?ree bones & ! fluid to ! fib]s ( ! auditory n]ves4 ,! impulses imp>t$ to ! auditory n]ve rea* ! bra9 & 9 "s unkn[n way are translat$ into s\nd4 #bgh4 ,c>e ( ! ,e>4 ,mo/ cat>rhal tr\bles are accompani$ by an ov]supply ( mucus :i* frequ5tly clogs up ! ,eu/a*ian tube & produces deafness4 ,= ! same reason1 colds & sore ?roat sometimes induce tempor>y deafness4 ,! wax ( ! e> is ess5tial = flexibility ( ! e> drum2 if an extra am\nt accumulates1 x c be got rid ( by ba?+ ! e> 9 hot wat]1 s9ce ! heat w melt ! wax4 ,! wax %\ld nev] be pick$ out ) p9 or %>p object except by a physician1 le/ injury be done to ! tympanic membrane4 #bgi4 ,! ,phonograph4 ,! inv5tion ( ! phonograph by ,edison 9 #ahgh m>k$ a new era 9 ! popul>ity & dissem9ation ( music4 ,up to t "t1 h\sehold music 0 limit$ to ^? :o 7 ri* en\gh to possess a real musical in/rum5t1 & :o 9 addition _h ! und]/&+ & ! skill to use ! in/rum5t4 ,! inv5tion ( ! phonograph has br\ght music to ?\s&s ( homes possess$ ( nei!r weal? nor skill4 ,t ! music reproduc$ by a phonograph is n always ( ! highe/ ord] does n1 9 ! lea/1 detract f ! int]e/ & wond] ( ! in/rum5t4 ,x c reproduce :at x is call$ ^u to reproduce1 & if human nature dem&s ! commonplace1 ! in/rum5t w be made to satisfy ! dem&4 ,on ! o!r h&1 spee*es ( fam\s m51 national songs1 magnific5t op]a selections1 & o!r pleas+ & in/ructive productions c be reproduc$ fairly accurately4 ,9 ?is way ! phonograph1 p]haps m ?an any o!r rec5t inv5tion1 c c>ry to ! %ut-ins a lively glimpse ( ! outside _w & its do+s4 ,illu/ration3 ,,fig4 #aie4--;,a vibrat+ tun+ =k traces a curv$ l9e on smok$ glass4 ,! phonograph consi/s ( a cyl9d] or disk ( wax ^u :i* ! vibrations ( a s5sitive diaphragm are record$ by means ( a f9e metal po9t4 ,! action ( ! po9t] 9 report+ ! vibrations ( a diaphragm is easily und]/ood by ref]5ce to a tun+ =k4 ,fa/5 a /iff bri/le to a tun+ =k by means ( wax1 all[+ ! end ( ! po9t to re/ lightly ^u a piece ( smok$ glass4 ,if ! glass is drawn "u ! bri/le a /raight l9e w be scrat*$ on ! glass1 b if ! tun+ =k is /ruck s t ! prongs vibrate back & =?1 !n ! /raight l9e *anges to a wavy l9e & ! type ( wavy l9e dep5ds ^u ! =k us$4 ,9 ! phonograph1 a diaphragm replaces ! tun+ =k & a cyl9d] 7or a disk7 coat$ ) wax replaces ! glass plate4 ,:5 ! speak] talks or ! s+] s+s1 8 voice /rikes aga9/ a delicate diaphragm & ?r[s x into vibration1 & ! metal po9t atta*$ to x traces on ! wax ( a mov+ cyl9d] a groove ( v>y+ %ape & appe>ance call$ ! record4 ,e v>iation 9 ! speak]'s voice is repeat$ 9 ! vibrations ( ! metal disk & h5ce 9 ! m9ute motion ( ! po9t] & 9 ! consequ5t record on ! cyl9d]4 ,! record ?us made c be plac$ 9 any o!r phonograph & if ! metal po9t] ( ?is new phonograph is made to pass ov] ! trac+1 ! process is rev]s$ & ! speak]'s voice is reproduc$4 ,! s\nd giv5 out 9 ! ?is way is fa9t & weak1 b c be /r5g!n$ by means ( a trumpet atta*$ to ! phonograph4 ,illu/ration3 ,,fig4 #aif4--;,a phonograph4 ,9 ?is ma*9e ! cyl9d] is replac$ by a revolv+ disk4 ,,*apt] ,,xxx ,,electricity #bhj4 ,_m animals possess ! five s5ses1 b only man possesses con/ructive1 creative p[]1 & is able to build on ! in=mation ga9$ ?r\gh ! s5ses4 ,x is ! con/ructive1 creative p[] :i* raises man above ! level ( ! bea/ & enables him to devise & fa%ion wond]ful inv5tions4 ,among ! mo/ important ( 8 inv5tions are ^? :i* relate to electricity2 inv5tions su* z trolley c>1 elevator1 automobile1 electric light1 ! telephone1 ! telegraph4 ,bell1 by 8 sup]ior con/ructive ability1 made possible ! practical use ( ! telephone1 & ,m>coni t ( wireless telegraphy4 ,to ^! inv5tions might be add$ _m o!rs :i* h increas$ ! effici5cy & production ( ! bus9ess _w & h decreas$ ! labor & /ra9 ( dome/ic life4 ,illu/ration3 ,,fig4 #aig4--;,a simple electric cell4 #bha4 ,electricity z fir/ ,obta9$ by ,man4 ,until mod]n times ! only electricity kn[n to u 0 t ( ! lightn+ fla%1 :i* man c\ld nei!r h9d] nor make4 ,b 9 ! ye> #ahjj1 electricity 9 ! =m ( a weak curr5t 0 obta9$ by ,volta ( ,italy 9 a v simple way2 & ev5 n[ our v>i\s electric batt]ies & cells are b a modification ( t us$ by ,volta & call$ a voltaic cell4 ,a /rip ( copp] & a /rip ( z9c are plac$ 9 a glass conta9+ dilute sulphuric acid1 a solution compos$ ( oxyg51 hydrog51 sulphur1 & wat]4 ,z soon z ! plates are imm]s$ 9 ! acid solution1 m9ute bubbles ( gas rise f ! z9c /rip & x beg9s to wa/e away sl[ly4 ,! solution gradually dissolves ! z9c & at ! same "t gives up "s ( ! hydrog5 :i* x conta9s2 b x has little or no effect on ! copp]1 s9ce !re is no visible *ange 9 ! copp] /rip4 ,if1 n[1 ! /rips are connect$ by means ( metal wires1 ! z9c wa/es away rapidly1 num]\s bubbles ( hydrog5 pass ov] to ! copp] /rip & collect on x1 & a curr5t ( electricity fl[s ?r\gh ! connect+ wires4 ,evid5tly1 ! s\rce ( ! curr5t is ! *emical action betwe5 ! z9c & ! liquid4 ,m]e inspection ( ! connect+ wire w n enable u to detect t a curr5t is fl[+1 b !re are v>i\s ways 9 :i* ! curr5t makes itself evid5t4 ,if ! ends ( ! wires atta*$ to ! /rips are br\ght 9 contact ) ea* o!r & !n sep>at$1 a fa9t sp>k passes1 & if ! ends are plac$ on ! tongue1 a tw+e is felt4 #bhb4 ,exp]im5ts :i* grew out ( ! ,voltaic ,cell4 ,s9ce *emical action on ! z9c is ! s\rce ( ! curr5t1 x w\ld seem reasonable to expect a curr5t if ! cell consi/$ ( two z9c plates in/ead ( "o z9c plate & "o copp] plate4 ,b :5 ! copp] /rip is replac$ by a z9c /rip s t ! cell consi/s ( two simil> plates1 no curr5t fl[s betwe5 !m4 ,9 ?is case1 *emical action is exp5d$ 9 heat r ?an 9 ! production ( electricity & ! liquid becomes hot4 ,b if c>bon & z9c are us$1 a curr5t is aga9 produc$1 ! z9c dissolv+ away z be=e1 & bubbles collect+ on ! c>bon plate4 ,by exp]im5t x has be5 f\nd t _m diff]5t metals may be employ$ 9 ! con/ruction ( an electric cell2 = example1 curr5t may be obta9$ f a cell made ) a z9c plate & a plat9um plate1 or f a cell made ) a lead plate & a copp] plate4 ,!n1 too1 "s o!r *emical1 su* z bi*romate ( potassium1 or ammonium *loride1 may be us$ in/ead ( dilute sulphuric acid4 ,almo/ any two diff]5t sub/ances w1 "u prop] conditions1 give a curr5t1 b ! /r5g? ( ! curr5t is 9 "s cases s weak z to be wor?less = practical use1 su* z telephon+1 or r++ a door bell4 ,:at is want$ is a /rong1 /eady curr5t1 & our *oice ( mat]ial is limit$ to ! sub/ances :i* w give ?is result4 ,z9c & lead c be us$1 b ! curr5t result+ is weak & feeble1 & = g5]al use z9c & c>bon are ! mo/ satisfactory4 #bhc4 ,electrical ,t]ms4 ,! plates or /rips us$ 9 mak+ an electric cell are call$ electrodes2 ! z9c is call$ ! negative electrode 7-71 & ! c>bon ! positive electrode 772 ! curr5t is consid]$ to fl[ ?r\gh ! wire f ! to !-electrode4 ,z a rule1 ea* electrode has atta*$ to x a b9d+ po/ to :i* wires c be quickly fa/5$4 ,! p[] t causes ! curr5t is call$ ! electromotive =ce1 & ! value ( ! electromotive =ce1 g5]ally writt5 ,e4,m4,f41 ( a cell dep5ds ^u ! mat]ials us$4 ,:5 ! cell consi/s ( copp]1 z9c1 & dilute sulphuric acid1 ! electromotive =ce has a def9ite value :i* is always ! same no matt] :at ! size or %ape ( ! cell4 ,b ! ,e4,m4,f4 has a decid$ly diff]5t value 9 a cell compos$ ( iron1 copp]1 & *romic acid4 ,ea* comb9ation ( mat]ial has its own specific electromotive =ce4 #bhd4 ,! ,disadvantage ( a ,simple ,cell4 ,:5 ! poles ( a simple voltaic cell are connect$ by a wire1 ! curr5t ?us produc$ sl[ly dim9i%es 9 /r5g? &1 aft] a %ort "t1 becomes feeble4 ,exam9ation ( ! cell %[s t ! copp] plate is cov]$ ) hydrog5 bubbles4 ,if1 h[ev]1 ^! bubbles are completely bru%$ away by means ( a rod or /ick1 ! curr5t /r5g? increases1 b z ! bubbles aga9 ga!r on ! electrode ! curr5t /r5g? dim9i%es1 & :5 ! bubbles =m a ?ick film on ! copp] plate1 ! curr5t is too weak to be ( any practical value4 ,! film ( bubbles weak5s ! curr5t because x practically sub/itutes a hydrog5 plate = a copp] plate1 & we saw 9 ,section #bhb t a *ange 9 any "o ( ! mat]ials ( :i* a cell is compos$ *anges ! curr5t4 ,?is weak5+ ( ! curr5t c be r$uc$ me*anically by bru%+ away ! bubbles z soon z !y are =m$2 or *emically1 by surr\nd+ ! copp] plate ) a sub/ance :i* w comb9e ) ! free hydrog5 & prev5t x f pass+ onw>d to ! copp] plate4 ,illu/ration3 ,,fig #aih4 ,! gravity cell4 ,9 practically all cells1 ! *emical me?od is us$ 9 pref]5ce to ! me*anical "o4 ,! num]\s types ( cells 9 daily use diff] *iefly 9 ! devices employ$ = prev5t+ ! =mation ( hydrog5 bubbles1 or = dispos+ ( !m :5 =m$4 ,"o ( ! be/-kn[n cells 9 :i* weak5+ ( ! curr5t is prev5t$ by *emical means is ! s-call$ gravity cell4 #bhe4 ,! ,gravity ,cell4 ,a l>ge1 irregul> copp] electrode is plac$ 9 ! bottom ( a j> 7,fig4 #aih71 & completely cov]$ ) a saturat$ solution ( copp] sulphate4 ,!n a l>ge1 irregul> z9c electrode is susp5d$ f ! top ( ! j>1 & is completely cov]$ ) dilute sulphuric acid :i* does n mix ) ! copp] sulphate1 b floats on ! top ( x l oil on wat]4 ,! hydrog5 =m$ by ! *emical action ( ! dilute sulphuric acid on ! z9c moves t[>d ! copp] electrode1 z 9 ! simple voltaic cell4 ,x does n rea* ! electrode1 h[ev]1 because1 :5 x comes 9 contact ) ! copp] sulphate1 x *anges places ) ! copp] !re1 sett+ x free1 b itself ent]+ into ! solution4 ,! copp] fre$ f ! copp] sulphate solution travels to ! copp] electrode1 & is deposit$ on x 9 a clean1 bright lay]4 ,in/ead ( a deposit ( hydrog5 !re is a deposit ( copp]1 & fall+ (f 9 curr5t is prev5t$4 ,! gravity cell is *eap1 easy to con/ruct1 & ( con/ant /r5g?1 & is 9 almo/ univ]sal use 9 telegraphic "w4 ,practically all small railroad /ations & local telegraph (fices use ^! cells4 ,illu/ration3 ,,fig4 #aii4--;,a dry cell4 #bhf4 ,dry ,cells4 ,! gravity cell1 :ile *eap & effective1 is inconv5i5t = g5]al use1 ow+ to ! fact t x _c be easily transport$1 & ! dry cell has l>gely supplant$ all o!rs1 because ( ! ease ) :i* x c be tak5 f place to place4 ,?is cell consi/s ( a z9c cup1 )9 :i* is a c>bon rod2 ! space betwe5 ! cup & rod is pack$ ) a moi/ pa/e conta9+ c]ta9 *emicals4 ,! moi/ pa/e takes ! place ( ! liquids us$ 9 o!r cells4 ,illu/ration3 ,,fig4 #bjj4--;,a batt]y ( ?ree cells4 #bhg4 ,a ,batt]y ( ,cells4 ,! electromotive =ce ( "o cell may n give a curr5t /rong en\gh to r+ a door bell or to op]ate a telephone4 ,b by us+ a numb] ( cells1 call$ a batt]y1 ! curr5t may be increas$ to almo/ any desir$ /r5g?4 ,if ?ree cells are arrang$ z 9 ,figure #bjj1 s t ! copp] ( "o cell is connect$ ) ! z9c ( ano!r cell1 ! electromotive =ce ( ! batt]y w be ?ree times z great z ! ,e4,m4,f4 ( a s+le cell4 ,if f\r cells are arrang$ 9 ! same way1 ! ,e4,m4,f4 ( ! batt]y is f\r times z great z ! ,e4,m4,f4 ( a s+le cell2 :5 five cells are comb9$1 ! result+ ,e4,m4,f4 is five times z great4 ,,*apt] ,,xxxi ,,"s ,,uses ,,( ,,electricity #bhh4 ,heat4 ,any "o :o h&les electric wires kn[s t !y are m or less heat$ by ! curr5ts :i* fl[ ?r\gh !m4 ,if ?ree cells are arrang$ z 9 ,figure #bjj & ! connect+ wire is co>se1 ! heat+ ( ! wire is sc>cely noticeable2 b if a %ort] wire ( ! same k9d is us$1 ! heat produc$ is slightly great]2 & if ! co>se wire is replac$ by a %ort1 f9e wire1 ! heat+ ( ! wire becomes v m>k$4 ,we are accu/om$ to say t a wire (f]s resi/ance to ! fl[ ( a curr5t2 t is1 :5ev] a curr5t meets resi/ance1 heat is produc$ 9 mu* ! same way z :5 me*anical motion meets an ob/acle & sp5ds its en]gy 9 friction4 ,! fl[ ( electricity along a wire c be comp>$ to ! fl[ ( wat] ?r\gh pipes3 a small pipe (f]s a great] resi/ance to ! fl[ ( wat] ?an a l>ge pipe2 less wat] c be =c$ ?r\gh a small pipe ?an ?r\gh a l>ge pipe1 b ! friction ( ! wat] aga9/ ! sides ( ! small pipe is mu* great] ?an 9 ! l>ge "o4 ,s x is ) ! electric curr5t4 ,9 f9e wires ! resi/ance to ! curr5t is l>ge & ! en]gy ( ! batt]y is exp5d$ 9 heat r ?an 9 curr5t4 ,if ! heat ?us produc$ is v great1 s]i\s consequ5ces may arise2 = example1 ! contact ( a hot wire ) wall pap] or dry beams may cause fire4 ,insurance companies dem& t ! wires us$ 9 wir+ a build+ = electric lights be ( a size suitable to ! curr5t to be c>ri$1 o!rwise !y w n take ! risk ( insurance4 ,! great] ! curr5t to be c>ri$1 ! co>s] is ! wire requir$ = safety4 #bhi4 ,electric ,/oves4 ,x is (t5 desirable to utilize ! electric curr5t = ! production ( heat4 ,= example1 trolley c>s are heat$ by coils ( wire "u ! seats4 ,! coils (f] s mu* resi/ance to ! passage ( a /rong curr5t ?r\gh !m t !y become heat$ & w>m ! c>s4 ,illu/ration3 ,,fig4 #bja4--;,an electric iron on a metal /&4 ,"s mod]n h\ses are s built t electricity is receiv$ into !m f ! great plants :]e x is g5]at$1 & by m]ely turn+ a swit* or ins]t+ a plug1 electricity is con/antly available4 ,9 consequ5ce1 _m practical applications ( electricity are possible1 among :i* are flatiron & toa/]4 ,illu/ration3 ,,fig4 #bjb4--,! f9e wires are /rongly heat$ by ! curr5t :i* fl[s ?r\gh !m4 ,)9 ! flatiron 7,fig4 #bja71 is a mass ( f9e wire coil$ z %[n 9 ,figure #bjb2 z soon z ! iron is connect$ ) ! h\se supply ( electricity1 curr5t fl[s ?r\gh ! f9e wire :i* ?us becomes /rongly heat$ & gives (f heat to ! iron4 ,! iron1 :5 once heat$1 reta9s an ev5 temp]ature z long z ! curr5t fl[s1 & ! laundress is1 9 consequ5ce1 free f ! disadvantages ( a sl[ly cool+ iron1 & ( frequ5t sub/itution ( a w>m iron = a cold "o4 ,electric irons are p>ticul>ly valuable 9 summ]1 because !y elim9ate ! necessity = a /rong fire1 & sp>e ! h\sewife int5se heat4 ,9 addition1 ! us] is n conf9$ to ! laundry1 b is free to seek ! coole/ "p ( ! h\se1 ! only requisite be+ an electrical connection4 ,illu/ration3 ,,fig4 #bjc4--;,bread c be toa/$ by electricity4 ,! toa/] 7,fig4 #bjc7 is ano!r useful electrical device1 s9ce by means ( x toa/ may be made on a d9+ table or at a b$side4 ,! small electrical /ove1 %[n 9 ,figure #bjd1 is simil> 9 pr9ciple to ! flatiron1 b 9 x ! heat+ coil is arrang$ z %[n 9 ,figure #bje4 ,to ! physician electric /oves are valuable1 s9ce 8 in/rum5ts c be /]iliz$ 9 wat] heat$ by ! /ove2 & t )\t fuel or odor ( gas4 ,a conv5i5t device is se5 9 ! heat+ pad 7,fig4 #bjf71 a sub/itute = a hot wat] bag4 ,emb$d$ 9 "s s(t ?ick sub/ance are ! insulat$ wires 9 :i* heat is to be develop$1 & ov] ?is is plac$ a cov]+ ( felt4 ,illu/ration3 ,,fig4 #bjd4--;,an electric /ove4 #bij4 ,electric ,lights4 ,! inc&esc5t bulbs :i* illum9ate our build+s consi/ ( a f9e1 hairlike ?read inclos$ 9 a glass bulb f :i* ! air has be5 remov$4 ,:5 an electric curr5t is s5t ?r\gh ! delicate filam5t1 x meets a /rong resi/ance4 ,! heat develop$ 9 ov]com+ ! resi/ance is s great t x makes ! filam5t a gl[+ mass4 ,! abs5ce ( air prev5ts ! filam5t f burn+1 & x m]ely gl[s & radiates ! light4 ,illu/ration3 ,,fig4 #bje4--,! heat+ elem5t 9 ! electric /ove4 #bia4 ,bla/+4 ,until rec5tly1 dynamit+ 0 att5d$ ) s]i\s dang]1 ow+ to ! fact t ! p]son :o appli$ ! tor* to ! fuse c\ld n make a safe retreat be=e ! explosion4 ,n[ a f9e wire is ins]t$ 9 ! fuse1 & :5 ev]y?+ is 9 read9ess1 ! ends ( ! wire are atta*$ to ! poles ( a di/ant batt]y & ! heat develop$ 9 ! wire ignites ! fuse4 ,illu/ration3 ,,fig4 #bjf4--;,an electric pad s]ves ! same purpose z a hot wat] bag4 #bib4 ,weld+ ( ,metals4 ,metals are fus$ & weld$ by ! use ( ! electric curr5t4 ,! metal pieces :i* are to be weld$ are press$ toge!r & a p[]ful curr5t is pass$ ?r\gh _! junction4 ,s great is ! heat develop$ t ! metals melt & fuse1 & on cool+ %[ p]fect union4 #bic4 ,*emical ,effects4 ,! ,plat+ ( ,gold1 ,silv]1 & ,o!r ,metals4 ,if /rips ( lead or rods ( c>bon are connect$ to ! t]m9als ( an electric cell1 z 9 ,figure #bjh1 & are !n dipp$ into a solution ( copp] sulphate1 ! /rip 9 connection ) ! negative t]m9al ( ! cell soon becomes ?9ly plat$ ) a coat+ ( copp]4 ,if a solution ( silv] nitrate is us$ 9 place ( ! copp] sulphate1 ! coat+ =m$ w be ( silv] in/ead ( copp]4 ,s long z ! curr5t fl[s & !re is any metal pres5t 9 ! solution1 ! coat+ cont9ues to =m on ! negative electrode1 & becomes ?ick] & ?ick]4 ,illu/ration3 ,,fig4 #bjg4--;,an inc&esc5t electric bulb4 ,! process by :i* metal is tak5 out ( solution1 z silv] out ( silv] nitrate & copp] out ( copp] sulphate1 & is 9 turn deposit$ z a coat+ on ano!r sub/ance1 is call$ electroplat+4 ,an electric curr5t c sep>ate a liquid into "s ( its v>i\s con/itu5ts & to deposit "o ( ! metal con/itu5ts on ! negative electrode4 ,illu/ration3 ,,fig4 #bjh4--;,c>bon rods 9 a solution ( copp] sulphate4 ,s9ce copp] is con/antly tak5 out ( ! solution ( copp] sulphate = deposit ^u ! negative electrode1 ! am\nt ( copp] rema9+ 9 ! solution /eadily decreases1 & f9ally !re is none ( x left = deposit4 ,9 ord] to ov]come ?is1 ! positive electrode %\ld be made ( ! same metal z t :i* is to be deposit$4 ,! positive metal electrode gradually dissolves & replaces ! metal lo/ f ! solution by deposit & electroplat+ c cont9ue z long z any positive electrode rema9s4 ,illu/ration3 ,,fig4 #bji4--,plat+ spoons by electricity4 ,practically all silv]1 gold1 & nickel plat+ is done 9 ?is way2 ma*9e1 bicycle1 & motor atta*m5ts are n solid1 b are ( *eap] mat]ial electrically plat$ ) nickel4 ,:5 spoons are to be plat$1 !y are hung 9 a ba? ( silv] nitrate side by side ) a ?ick slab ( pure silv]1 z 9 ,figure #bji4 ,! spoons are connect$ ) ! negative t]m9al ( ! batt]y1 :ile ! slab ( pure silv] is connect$ ) ! positive t]m9al ( ! same batt]y4 ,! l5g? ( "t t ! curr5t fl[s det]m9es ! ?ickness ( ! plat+4 #bid4 ,h[ ,pure ,metal is obta9$ f ,ore4 ,:5 ore is m9$1 x conta9s 9 addition to ! desir$ metal _m o!r sub/ances4 ,9 ord] to sep>ate out ! desir$ metal1 ! ore is plac$ 9 "s suitable acid ba?1 & is connect$ ) ! positive t]m9al ( a batt]y1 ?us tak+ ! place ( ! silv] slab 9 ! la/ ,section4 ,:5 curr5t fl[s1 any pure metal :i* is pres5t is dissolv$ out ( ! ore & is deposit$ on a conv5i5t negative electrode1 :ile ! impurities rema9 9 ! ore or drop z s$im5t to ! bottom ( ! vessel4 ,metals sep>at$ f ! ore by electricity are call$ electrolytic metals & are ! pure/ obta9able4 #bie4 ,pr9t+4 ,! ability ( ! electric curr5t to decompose a liquid & to deposit a metal con/itu5t has practically revolutioniz$ ! process ( pr9t+4 ,=m]ly1 type 0 arrang$ & reta9$ 9 position until ! requir$ numb] ( impressions _h be5 made1 ! type mean:ile be+ unavailable = o!r uses4 ,moreov]1 ! pr9t+ ( a second edition necessitat$ practically z great labor z did ! fir/ edition1 ! type be+ necess>ily set afre%4 ,n[1 h[ev]1 ! type is set up & a mold ( x is tak5 9 wax4 ,?is mold is coat$ ) graphite to make x a conductor & is !n susp5d$ 9 a ba? ( copp] sulphate1 side by side ) a slab ( pure copp]4 ,curr5t is s5t ?r\gh ! solution z describ$ 9 ,section #bic1 until a ?9 coat+ ( copp] has be5 deposit$ on ! mold4 ,! mold is !n tak5 f ! ba?1 & ! wax is replac$ by "s metal :i* gives /r5g? & support to ! ?9 copp] plate4 ,f ?is copp] plate1 :i* is an exact reproduction ( ! orig9al type1 _m ?\s& copies c be pr9t$4 ,! plate c be pres]v$ & us$ f "t to "t = lat] editions1 & ! orig9al type c be put back into ! cases & us$ aga94 ,,*apt] ,,xxxii ,,mod]n ,,electrical ,,inv5tions #bif4 ,an ,electric ,curr5t acts l a ,magnet4 ,9 ord] to und]/& ! action ( ! electric bell1 we mu/ consid] a ?ird effect :i* an electric curr5t c cause4 ,connect "s cells z %[n 9 ,figure #bjj & close ! circuit ?r\gh a /\t heavy copp] wire1 dipp+ a portion ( ! wire into f9e iron fil+s4 ,a ?ick clu/] ( fil+s w adh]e to ! wire 7,fig4 #baj71 & w cont9ue to cl+ to x s long z ! curr5t fl[s4 ,if ! curr5t is brok51 ! fil+s fall f ! wire1 & only s long z ! curr5t fl[s ?r\gh ! wire does ! wire h p[] to attract iron fil+s4 ,an electric curr5t makes a wire equival5t to a magnet1 giv+ x ! p[] to attract iron fil+s4 ,illu/ration3 ,,fig4 #baj4--;,a wire c>ry+ curr5t attracts iron fil+s4 ,illu/ration3 ,,fig4 #baa4--;,a loosely w\nd coil ( wire4 ,al?\gh su* a /raight curr5t be>+ wire attracts iron fil+s1 its p[] ( attraction is v small2 b its magnetic /r5g? c be increas$ by coil+ z 9 ,figure #baa4 ,su* an arrangem5t ( wire is kn[n z a helix or sol5oid1 & is capable ( lift+ or pull+ l>g] & m num]\s fil+s & ev5 good-siz$ pieces ( iron1 su* z tacks4 ,fil+s d n adh]e to ! sides ( ! helix1 b !y cl+ 9 clu/]s to ! ends ( ! coil4 ,?is %[s t ! ends ( ! helix h magnetic p[] b n ! sides4 ,if a s(t iron nail 7,fig4 #bab7 or its equival5t is slipp$ )9 ! coil1 ! lift+ & attractive p[] ( ! coil is increas$1 & comp>atively heavy weights c be lift$4 ,illu/ration3 ,,fig4 #bab4--;,coil & s(t iron rod4 ,a coil ( wire trav]s$ by an electric curr5t & conta9+ a core ( s(t iron has ! p[] ( attract+ & mov+ heavy iron objects2 t is1 x acts l a magnet4 ,su* an arrangem5t is call$ an electromagnet4 ,z soon z ! curr5t ceases to fl[1 ! electromagnet loses its magnetic p[] & becomes m]ely iron & wire )\t magnetic attraction4 ,if _m cells are us$1 ! /r5g? ( ! electromagnet is increas$1 & if ! coil is w\nd closely1 z 9 ,figure #bac1 in/ead ( loosely1 z 9 ,figure #baa1 ! magnetic /r5g? is /ill fur!r increas$4 ,! /r5g? ( any electromagnet dep5ds ^u ! numb] ( coils w\nd on ! iron core & ^u ! /r5g? ( ! curr5t :i* is s5t ?r\gh ! coils4 ,illu/ration3 ,,fig4 #bac4--;,an electromagnet4 ,illu/ration3 ,,fig4 #bad4--;,a horse%oe electromagnet is p[]ful en\gh to support heavy weights4 ,to increase ! /r5g? ( ! electromagnet /ill fur!r1 ! s-call$ horse%oe %ape is us$ 7,fig4 #bad74 ,9 su* an arrangem5t !re is practically ! /r5g? ( two sep>ate electromagnets4 #big4 ,! ,electric ,bell4 ,! r++ ( ! electric bell is due to ! attractive p[] ( an electromagnet4 ,by ! pu%+ ( a button 7,fig4 #bae7 connection is made ) a batt]y1 & curr5t fl[s ?r\gh ! wire w\nd on ! iron spools1 & fur!r to ! screw ,p :i* presses aga9/ ! s(t iron /rip or armature ,s2 & f ,s ! curr5t fl[s back to ! batt]y4 ,z soon z ! curr5t fl[s1 ! coils become magnetic & attract ! s(t iron armature1 draw+ x =w>d & caus+ ! clapp] to /rike ! bell4 ,9 ?is position1 ,s no long] t\*es ! screw ,p1 & h5ce !re is no complete pa? = ! electricity1 & ! curr5t ceases4 ,b ! attractive1 magnetic p[] ( ! coils /ops z soon z ! curr5t ceases2 h5ce !re is no?+ to hold ! armature d[n1 & x flies back to its =m] position4 ,9 do+ ?is1 h[ev]1 ! armature makes contact at ,p ?r\gh ! spr+1 & ! curr5t fl[s once m2 z a result ! coils aga9 become magnets1 ! armature is aga9 drawn =w>d1 & ! clapp] aga9 /rikes ! bell4 ,b imm$iately aft]w>ds ! armature spr+s backw>d & makes contact at ,p & ! entire op]ation is repeat$4 ,s long z we press ! button ?is process cont9ues produc+ :at s\nds l a cont9u\s j+le2 9 reality ! clapp] /rikes ! bell e "t a curr5t passes ?r\gh ! electromagnet4 ,illu/ration3 ,,fig4 #bae4--,! electric bell4 #bih4 ,! ,pu% ,button4 ,! pu% button is an ess5tial "p ( e electric bell1 because )\t x ! bell ei!r w\ld n r+ at all1 or w\ld r+ incessantly until ! cell 0 exhau/$4 ,:5 ! pu% button is free1 z 9 ,figure #baf1 ! cell t]m9als are n connect$ 9 an unbrok5 pa?1 & h5ce ! curr5t does n fl[4 ,:51 h[ev]1 ! button is press$1 ! curr5t has a complete pa?1 provid$ !re is ! prop] connection at ,s4 ,t is1 ! pressure on ! pu% button p]mits curr5t to fl[ to ! bell4 ,! fl[ ( ?is curr5t !n dep5ds solely ^u ! connection at ,s1 :i* is alt]nately made & brok51 & 9 ?is way produces s\nd4 ,illu/ration3 ,,fig4 #baf4--,pu% button4 ,! sign ,bell out ( ord] is usually due to ! fact t ! batt]y is ei!r tempor>ily or p]man5tly exhau/$4 ,9 w>m wea!r ! liquid 9 ! cell may dry up & cause /oppage ( ! curr5t4 ,if fre% liquid is p\r$ into ! vessel s t ! *emical action ( ! acid on ! z9c is r5ew$1 ! curr5t aga9 fl[s4 ,ano!r explanation ( an out-(-ord] bell is t ! liquid may h eat5 up all ! z9c2 if ?is is ! case1 ! ins]tion ( a fre% /rip ( z9c w remove ! difficulty & ! curr5t w fl[4 ,if dry cells are us$1 !re is no rem$y except 9 ! pur*ase ( new cells4 #bii4 ,h[ ,electricity may be lo/ to ,use4 ,9 ! electric bell1 we saw t an air gap at ! pu% button /opp$ ! fl[ ( electricity4 ,if we cut ! wire connect+ ! poles ( a batt]y1 ! curr5t ceases because an air gap int]v5es & electricity does n readily pass ?r\gh air4 ,_m sub/ances besides air /op ! fl[ ( electricity4 ,if a /rip ( glass1 rubb]1 mica1 or p>aff9 is introduc$ any:]e 9 a circuit1 ! curr5t ceases4 ,if a metal is ins]t$ 9 ! gap1 ! curr5t aga9 fl[s4 ,sub/ances :i*1 l an air gap1 int]f]e ) ! fl[ ( electricity are call$ non-conductors1 or1 m commonly1 insulators4 ,sub/ances :i*1 l ! e>?1 ! human body1 & all o!r moi/ objects1 conduct electricity are conductors4 ,if ! telephone & electric light wires 9 our h\ses 7 n insulat$ by a cov]+ ( ?read1 or clo?1 or o!r non conduct+ mat]ial1 ! electricity w\ld escape into surr\nd+ objects in/ead ( fl[+ ?r\gh ! wire & produc+ s\nd & light4 ,9 our city /reets1 ! ov]head wires are support$ on glass knobs or are closely wrapp$1 9 ord] to prev5t ! escape ( electricity ?r\gh ! poles to ! gr\nd4 ,9 ord] to h a /eady1 dep5dable curr5t1 ! wire c>ry+ ! curr5t mu/ be insulat$4 ,lack ( insulation means n only ! loss ( curr5t = practical uses1 b also s]i\s consequ5ces 9 ! ev5t ( ! cross+ ( curr5t-be>+ wires4 ,if two wires prop]ly insulat$ t\* ea* o!r1 ! curr5ts fl[ along _! respective wires unalt]$2 if1 h[ev]1 two un9sulat$ wires t\*1 "s ( ! electricity fl[s f "o to ! o!r4 ,heat is develop$ z a result ( ?is transf]5ce1 & ! heat ?us develop$ is sometimes s great t fire occurs4 ,= ?is reason1 wires are heavily insulat$ & extra protection is provid$ at po9ts :]e num]\s wires t\* or cross4 ,conductors & insulators are necess>y to ! effici5t & economic fl[ ( a curr5t1 ! insulator prev5t+ ! escape ( electricity & less5+ ! dang] ( fire1 & ! conductor c>ry+ ! curr5t4 #cjj4 ,! ,telegraph4 ,telegraphy is ! process ( transmitt+ messages f place to place by means ( an electric curr5t4 ,! pr9ciple und]ly+ ! action ( ! telegraph is ! pr9ciple ^u :i* ! electric bell op]ates2 namely1 t a piece ( s(t iron becomes a magnet :ile a curr5t fl[s ar\nd x1 b loses its magnetism z soon z ! curr5t ceases4 ,9 ! electric bell1 ! electromagnet1 clapp]1 pu% button1 & batt]y are relatively ne>1--usually all are locat$ 9 ! same build+2 :ile 9 ! telegraph ! curr5t may travel miles be=e x rea*es ! electromagnet & produces motion ( ! armature4 ,illu/ration3 ,,fig4 #bag4--;,diagram ( ! electric telegraph4 ,! fundam5tal connections ( ! telegraph are %[n 9 ,figure #bag4 ,if ! key ,k is press$ d[n by an op]ator 9 ,philadelphia1 ! curr5t f ! batt]y 7only "o cell is %[n = simplicity7 fl[s ?r\gh ! l9e to ,new ,york1 passes ?r\gh ! electromagnet ,m1 & !nce back to ,philadelphia4 ,z long z ! key ,k is press$ d[n1 ! coil ,m acts z a magnet & attracts & holds fa/ ! armature ,a2 b z soon z ,k is releas$1 ! curr5t is brok51 ,m loses its magnetism1 & ! armature is pull$ back by ! spr+ ,d4 ,by a me*anical device1 tape is drawn uni=mly "u ! light m>k] ,p atta*$ to ! armature4 ,if ,k is clos$ = b a %ort "t1 ! armature is drawn d[n = b a %ort int]val1 & ! m>k] regi/]s a dot on ! tape4 ,if ,k is clos$ = a long] "t1 a %ort da% is made by ! m>k]1 &1 9 g5]al1 ! l5g? ( "t t ,k is clos$ det]m9es ! l5g? ( ! m>ks record$ on ! tape4 ,! telegraphic alphabet consi/s ( dots & da%es & _! v>i\s comb9ations1 & h5ce an int]pretation ( ! dot & da% symbols record$ on ! tape is all t is necess>y = ! receiv+ ( a telegraphic message4 ,! ,morse telegraphic code1 consi/+ ( dots1 da%es1 & spaces1 is giv5 9 ,figure #bah4 ,illu/ration3 ,a 4- ,h 4444 ,o 4 4 ,u 44- ,b -444 ,i 44 ,p 44444 ,v 444- ,c 44 4 ,j -4-4 ,q 44-4 ,w 4-- ,d -44 ,k -4- ,r 4 44 ,x 4-44 ,e 4 ,l --- ,s 444 ,y 44 44 ,f 4-4 ,m - - ,t - ,z 444 4 ,g --4 ,n -4 ,,fig4 #bah4--,! ,morse telegraphic code4 ,! telegraph is n[ su* a univ]sal means ( communication betwe5 di/ant po9ts t "o wond]s h[ bus9ess 0 conduct$ be=e its inv5tion 9 #ahcb by ,s4,f4,b4 ,morse4 ,illu/ration3 ,,fig4 #bai4--,! s\nd]4 #cja4 ,improvem5ts4 ,! ,s\nd]4 ,%ortly aft] ! inv5tion ( telegraphy1 op]ators le>n$ t !y c\ld read ! message by ! click ( ! m>k] aga9/ a metal rod :i* took ! place ( ! tape4 ,9 practically all telegraph (fices ( ! pres5t day ! old-fa%ion$ tape is replac$ by ! s\nd]1 %[n 9 ,figure #bai4 ,:5 curr5t fl[s1 a lev]1 ,l1 is drawn d[n by ! electromagnet & /rikes aga9/ a solid metal piece ) a click2 :5 ! curr5t is brok51 ! lev] spr+s upw>d1 /rikes ano!r metal piece & makes a diff]5t click4 ,x is cle> t ! work+ ( ! key :i* />ts & /ops ! curr5t 9 ?is l9e w be imitat$ by ! motion & ! result+ clicks ( ! s\nd]4 ,by means ( ^! v>y+ clicks ( ! s\nd]1 ! op]ator int]prets ! message4 ,illu/ration3 ,,fig4 #bbj4--;,diagram ( a mod]n telegraph sy/em4 ,! ,relay4 ,:5 a telegraph l9e is v long1 ! resi/ance ( ! wire is great1 & ! curr5t :i* passes ?r\gh ! electromagnet is correspond+ly weak1 s feeble inde$ t ! armature mu/ be made v ?9 & light 9 ord] to be affect$ by ! makes & breaks 9 ! curr5t4 ,! clicks ( an armature light en\gh to respond to ! weak curr5t ( a long wire are too fa9t to be recogniz$ by ! e>1 & h5ce 9 su* long circuits "s device mu/ be introduc$ :]eby ! effect is increas$4 ,?is is usually done by in/all+ at ea* /ation a local batt]y & a v delicate & s5sitive electromagnet call$ ! relay4 ,"u ^! conditions ! curr5t ( ! ma9 l9e is n s5t ?r\gh ! s\nd]1 b ?r\gh ! relay :i* op5s & closes a local batt]y 9 connection ) ! /rong s\nd]4 ,= example1 ! relay is s arrang$ t curr5t f ! ma9 l9e runs ?r\gh x exactly z x runs ?r\gh ,m 9 ,figure #bag4 ,:5 curr5t is made1 ! relay attracts an armature1 :i* !reby closes a circuit 9 a local batt]y & ?us causes a click ( ! s\nd]4 ,:5 ! curr5t 9 ! ma9 l9e is brok51 ! relay loses its magnetic attraction1 its armature spr+s back1 connection is brok5 9 ! local circuit1 & ! s\nd] responds by all[+ its armature to spr+ back ) a %>p s\nd4 #cjb4 ,! ,e>? an ,important ,"p ( a ,telegraphic ,sy/em4 ,we le>n$ 9 ,section #bii t electricity c\ld fl[ ?r\gh _m diff]5t sub/ances1 "o ( :i* 0 ! e>?4 ,9 all ord9>y telegraph l9es1 advantage is tak5 ( ?is fact to utilize ! e>? z a conductor & to disp5se ) "o wire4 ,orig9ally two wires 7 us$1 z 9 ,figure #bag2 !n x 0 f\nd t a railroad track c\ld be sub/itut$ = "o wire1 & lat] t ! e>? itself s]v$ equally well = a return wire4 ,! pres5t arrangem5t is %[n 9 ,figure #bbj1 :]e !re is b "o wire1 ! circuit be+ complet$ by ! e>?4 ,no fact 9 electricity seems m m>vel\s ?an t ! ?\s&s ( messages fla%+ along ! wires ov]head are likewise travel+ ?r\gh ! gr\nd b5ea?4 ,if x 7 n = ?is use ( ! e>? z an unfail+ conductor1 ! network ( ov]head wires 9 our city /reets w\ld be ev5 m complex ?an x n[ is4 #cjc4 ,advances 9 ,telegraphy4 ,! me*anical improvem5ts 9 telegraphy h be5 s rapid t at pres5t a s+le op]ator c easily s5d or receive =ty words a m9ute4 ,he c telegraph m quickly ?an ! av]age p]son c write2 & ) a comb9ation ( ! late/ improvem5ts ! spe$ c be enorm\sly increas$4 ,rec5tly1 #aejj words 7 fla%$ f ,new ,york to ,bo/on ov] a s+le wire 9 "o second4 ,9 actual practice messages are n ord9>ily s5t long di/ances ov] a direct l9e1 b are automatically transf]r$ to new l9es at def9ite po9ts4 ,= example1 a message f ,new ,york to ,*icago does n travel along an un9t]rupt$ pa?1 b is automatically transf]r$ at "s po9t1 su* z ,lanca/]1 to a second l9e :i* c>ries x on to ,pittsburgh1 :]e x is aga9 transf]r$ to a ?ird l9e :i* takes x f>!r on to its de/9ation4 ,,*apt] ,,xxxiii ,,magnets ,,& ,,curr5ts #cjd4 ,9 ! twelf? c5tury1 !re 0 introduc$ into ,europe f ,*9a a simple in/rum5t :i* *ang$ j\rney+ on ! sea f unc]ta9 w&]+ to a def9ite1 safe voyage4 ,?is in/rum5t 0 ! compass 7,fig4 #bba71 & because ( ! prop]ty ( ! compass ne$le 7a magnet7 to po9t un]r+ly nor? & s\?1 sailors 7 able to det]m9e directions on ! sea & to /e] = ! desir$ po9t4 ,illu/ration3 ,,fig4 #bba4--,! compass4 ,s9ce an electric curr5t is practically equival5t to a magnet 7,section #bif71 x becomes necess>y to "k ! mo/ important facts relative to magnets1 facts simple 9 !mselves b ( f>-rea*+ value & consequ5ces 9 electricity4 ,)\t a k ( ! magnetic *>act]i/ics ( curr5ts1 ! con/ruction ( ! motor w\ld h be5 impossible1 & trolley c>s1 electric fans1 motor boats1 & o!r equally well-kn[n electrical contrivances w\ld be unkn[n4 #cje4 ,! ,attractive ,p[] ( a ,magnet4 ,! magnet be/ kn[n to u all is ! compass ne$le1 b = conv5i5ce we w use a magnetic ne$le 9 ! %ape ( a b> l>g] & /rong] ?an t employ$ 9 ! compass4 ,if we lay su* a magnet on a pile ( iron fil+s1 x w be f\nd on lift+ ! magnet t ! fil+s cl+ to ! ends 9 tufts1 b leave x almo/ b>e 9 ! c5t] 7,fig4 #bbb74 ,! po9ts ( attraction at ! two ends are call$ ! poles ( ! magnet4 ,illu/ration3 ,,fig4 #bbb4--;,a magnet4 ,if a delicately made magnet is susp5d$ z 9 ,figure #bbc1 & is all[$ to sw+ freely1 x w always assume a def9ite nor? & s\? position4 ,! pole :i* po9ts nor? :5 ! ne$le is susp5d$ is call$ ! nor? pole & is m>k$ ,n1 :ile ! pole :i* po9ts s\? :5 ! ne$le is susp5d$ is call$ ! s\? pole & is m>k$ ,s4 ,a freely susp5d$ magnet po9ts ne>ly nor? & s\?4 ,a magnet has two ma9 po9ts ( attraction call$ respectively ! nor? & s\? poles4 ,illu/ration3 ,,fig4 #bbc4--,! magnetic ne$le4 #cjf4 ,! ,ext5t ( ,magnetic ,attraction4 ,if a ?9 %eet ( pap] or c>dbo>d is laid ov] a /rong1 b>-%ap$ magnet & iron fil+s are !n g5tly /rewn on ! pap]1 ! fil+s cle>ly indicate ! position ( ! magnet b5ea?1 & if ! c>dbo>d is g5tly tapp$1 ! fil+s arrange !mselves z %[n 9 ,figure #bbd4 ,if ! pap] is held "s di/ance above ! magnet1 ! influ5ce on ! fil+s is less def9ite1 & f9ally1 if ! pap] is held v f> away1 ! fil+s d n respond at all1 b lie on ! c>dbo>d z dropp$4 ,! magnetic p[] ( a magnet1 :ile n conf9$ to ! magnet itself1 does n ext5d indef9itely into ! surr\nd+ region2 ! influ5ce is /rong ne> ! magnet1 b at a di/ance becomes s weak z to be inappreciable4 ,! region ar\nd a magnet ?r\gh :i* its magnetic =ce is felt is call$ ! field ( =ce1 or simply ! magnetic field1 & ! def9ite l9es 9 :i* ! fil+s arrange !mselves are call$ l9es ( =ce4 ,illu/ration3 ,,fig4 #bbd4--;,iron fil+s scatt]$ ov] a magnet arrange !mselves 9 def9ite l9es4 ,! magnetic p[] ( a magnet is n limit$ to ! magnet1 b ext5ds to a consid]able di/ance 9 all directions4 #cjg4 ,! ,influ5ce ( ,magnets ^u ,ea* ,o!r4 ,if :ile our susp5d$ magnetic ne$le is at re/ 9 its *>act]i/ic nor?-&-s\? direction ano!r magnet is br\ght ne>1 ! susp5d$ magnet is turn$2 t is1 motion is produc$ 7,fig4 #bbe74 ,if ! nor? pole ( ! free magnet is br\ght t[>d ! s\? pole ( ! susp5d$ magnet1 ! latt] moves 9 su* a way t ! two poles ,n & ,s are z close toge!r z possible4 ,if ! nor? pole ( ! free magnet is br\ght t[>d ! nor? pole ( ! susp5d$ magnet1 ! latt] moves 9 su* a way t ! two poles ,n & ,n are z f> ap>t z possible4 ,9 e case t c be te/$1 x is f\nd t a nor? pole repels a nor? pole1 & a s\? pole repels a s\? pole2 b t a nor? & a s\? pole always attract ea* o!r4 ,illu/ration3 ,,fig4 #bbe4--;,a s\? pole attracts a nor? pole4 ,! ma9 facts relative to magnets may be summ$ up z foll[s3-- a4 ,a magnet po9ts ne>ly nor? & s\? if x is all[$ to sw+ freely4 b4 ,a magnet conta9s two unlike poles1 "o ( :i* p]si/5tly po9ts nor?1 & ! o!r ( :i* z p]si/5tly po9ts s\?1 if all[$ to sw+ freely4 c4 ,poles ( ! same "n repel ea* o!r2 poles ( unlike "n attract ea* o!r4 d4 ,a magnet possesses ! p[] ( attract+ c]ta9 sub/ances1 l iron1 & ?is p[] ( attraction is n limit$ to ! magnet itself b ext5ds into ! region ar\nd ! magnet4 #cjh4 ,magnetic ,prop]ties ( an ,electric ,curr5t4 ,if a curr5t-be>+ wire is really equival5t 9 its magnetic p[]s to a magnet1 x mu/ possess all ( ! *>act]i/ics m5tion$ 9 ! prec$+ ,section4 ,we saw 9 ,section #bif t a coil$ wire ?r\gh :i* curr5t 0 fl[+ w\ld attract iron fil+s at ! two ends ( ! helix4 ,t a coil ?r\gh :i* curr5t fl[s possesses ! *>act]i/ics a1 b1 c1 & d ( a magnet is %[n z foll[s3-- a1 b4 ,if a helix m>k$ at "o end ) a r$ /r+ is arrang$ s t x is free to rotate & a /rong curr5t is s5t ?r\gh x1 ! helix w imm$iately turn & face ab\t until x po9ts nor? & s\?4 ,if x is di/urb$ f ?is position1 x w sl[ly sw+ back until x occupies its *>act]i/ic nor? & s\? position4 ,! end to :i* ! /r+ is atta*$ w p]si/5tly po9t ei!r nor? or s\?4 ,if ! curr5t is s5t ?r\gh ! coil 9 ! opposite direction1 ! two poles ex*ange positions & ! helix turns until ! new nor? pole po9ts nor?4 ,illu/ration3 ,,fig4 #bbf4--;,a helix ?r\gh :i* curr5t fl[s always po9ts nor? & s\?1 if x is free to rotate4 c4 ,if a coil conduct+ a curr5t is held ne> a susp5d$ magnet1 "o end ( ! helix w be f\nd to attract ! nor? pole ( ! magnet1 :ile ! opposite end w be f\nd to repel ! nor? pole ( ! magnet4 ,9 fact1 ! helix w be f\nd to behave 9 e way z a magnet1 ) a nor? pole at "o end & a s\? pole at ! o!r4 ,if ! curr5t is s5t ?r\gh ! helix 9 ! opposite direction1 ! nor? & s\? poles ex*ange places4 ,illu/ration3 ,,fig4 #bbg4--;,a wire ?r\gh :i* curr5t fl[s is surr\nd$ by a field ( magnetic =ce4 ,if ! numb] ( turns 9 ! helix is r$uc$ until b a s+le loop rema9s1 ! result is ! same2 ! s+le loop acts l a flat magnet1 "o side ( ! loop always fac+ nor?w>d & "o s\?w>d1 & "o face attract+ ! nor? pole ( ! susp5d$ magnet & "o repell+ x4 d4 ,if a wire is pass$ ?r\gh a c>d & a /rong curr5t is s5t ?r\gh ! wire1 iron fil+s w1 :5 spr9kl$ ^u ! c>d1 arrange !mselves 9 def9ite directions 7,fig4 #bbg74 ,a wire c>ry+ a curr5t is surr\nd$ by a magnetic field ( =ce4 ,a magnetic ne$le held "u a curr5t-be>+ wire turns on its pivot & f9ally comes to re/ at an angle ) ! curr5t4 ,! fact t ! ne$le is deflect$ by ! wire %[s t ! magnetic p[] ( ! wire ext5ds into ! surr\nd+ m$ium4 ,! magnetic prop]ties ( curr5t electricity 7 discov]$ by ,o]/$ ( ,d5m>k less ?an a hundr$ ye>s ago2 b s9ce t "t practically all important electrical ma*9]y has be5 bas$ ^u "o or m ( ! magnetic prop]ties ( electricity4 ,! motors :i* drive our electric fans1 our mills1 & our trolley c>s owe _! exi/5ce entirely to ! magnetic action ( curr5t electricity4 ,illu/ration3 ,,fig4 #bbh4--,! coil turns 9 su* a way t its nor? pole is opposite ! s\? pole ( ! magnet4 #cji4 ,! ,pr9ciple ( ! ,motor4 ,if a close coil ( wire is susp5d$ betwe5 ! poles ( a /rong horse%oe magnet1 x w n assume any *>act]i/ic position b w rema9 :]ev] plac$4 ,if1 h[ev]1 a curr5t is s5t ?r\gh ! wire1 ! coil faces ab\t & assumes a def9ite position4 ,?is is because a coil1 c>ry+ a curr5t1 is equival5t to a magnet ) a nor? & s\? face2 &1 9 accordance ) ! magnetic laws1 t5ds to move until its nor? face is opposite ! s\? pole ( ! horse%oe magnet1 & its s\? face opposite ! nor? pole ( ! magnet4 ,if1 :5 ! coil is at re/ 9 ?is position1 ! curr5t is rev]s$1 s t ! nor? pole ( ! coil becomes a s\? pole & ! =m] s\? pole becomes a nor? pole1 ! result is t l poles ( coil & magnet face ea* o!r4 ,b s9ce l poles repel ea* o!r1 ! coil w move1 & w rotate until its new nor? pole is opposite to ! s\? pole ( ! magnet & its new s\? pole is opposite ! nor? pole4 ,by s5d+ a /rong curr5t ?r\gh ! coil1 ! helix is made to rotate ?r\gh a half turn2 by rev]s+ ! curr5t :5 ! coil is at ! half turn1 ! helix is made to cont9ue its rotation & to sw+ ?r\gh a :ole turn4 ,if ! curr5t c\ld be repeat$ly rev]s$ j z ! helix complet$ its half turn1 ! motion c\ld be prolong$2 p]iodic curr5t rev]sal w\ld produce cont9u\s rotation4 ,?is is ! pr9ciple ( ! motor4 ,illu/ration3 ,,fig4 #bbi4--,pr9ciple ( ! motor4 ,x is easy to see t long-cont9u$ rotation w\ld be impossible 9 ! arrangem5t ( ,figure #bbh1 s9ce ! twi/+ ( ! susp5d+ wire w\ld int]f]e ) free motion4 ,if ! motor is to be us$ = cont9u\s motion1 "s device mu/ be employ$ by means ( :i* ! helix is capable ( cont9u$ rotation ar\nd its support4 ,9 practice1 ! rotat+ coil ( a motor is arrang$ z %[n 9 ,figure #bbi4 ,wires f ! coil t]m9ate on metal disks & are securely sold]$ !re4 ,! coil & disks are support$ by ! /rong & well-insulat$ rod ,r1 :i* re/s ^u braces1 b :i* nev]!less rotates freely ) disks & coil4 ,! curr5t fl[s to ! coil ?r\gh ! ?9 metal /rips call$ bru%es1 :i* re/ lightly ^u ! disks4 ,:5 ! curr5t :i* ent]s at ,b fl[s ?r\gh ! wire1 ! coil rotates1 t5d+ to set itself s t its nor? face is opposite ! s\? face ( ! magnet4 ,if1 :5 ! helix has j rea*$ ?is position1 ! curr5t is rev]s$--ent]+ at ,b' in/ead ( ,b--! poles ( ! coil are ex*ang$2 ! rotation1 !re=e1 does n cease1 b cont9ues = ano!r half turn4 ,prop] rev]sals ( ! curr5t are accompani$ by cont9u\s motion1 & s9ce ! disk & %aft rotate ) ! coil1 !re is cont9u\s rotation4 ,if a :eel is atta*$ to ! rotat+ %aft1 weights c be lift$1 & if a belt is atta*$ to ! :eel1 ! motion ( ! rotat+ helix c be transf]r$ to ma*9]y = practical use4 ,! rotat+ coil is usually spok5 ( z ! armature1 & ! l>ge magnet z ! field magnet4 #caj4 ,me*anical ,rev]sal ( ! ,curr5t4 ,! ,commutator4 ,x is n possible by h& to rev]se ! curr5t ) suffici5t rapidity & precision to insure un9t]rupt$ rotation2 moreov]1 ! physical ex]tion ( su* frequ5t rev]sals is consid]able4 ,h5ce1 "s me*anical device = p]iodically rev]s+ ! curr5t is necess>y1 if ! motor is to be ( comm]cial value4 ,illu/ration3 ,,fig4 #bcj4--,! commutator4 ,! me*anical rev]sal ( ! curr5t is accompli%$ by ! use ( ! commutator1 :i* is a metal r+ split into halves1 well insulat$ f ea* o!r & f ! %aft4 ,to ea* half ( ?is r+ is atta*$ "o ( ! ends ( ! armature wire4 ,! bru%es :i* c>ry ! curr5t are set on opposite sides ( ! r+ & d n rotate4 ,z armature1 commutator1 & %aft rotate1 ! bru%es connect fir/ ) "o segm5t ( ! commutator & !n ) ! o!r4 ,s9ce ! circuit is arrang$ s t ! curr5t always ent]s ! commutator ?r\gh ! bru% ,b1 ! fl[ ( ! curr5t into ! coil is always ?r\gh ! segm5t 9 contact ) ,b2 b ! segm5t 9 contact ) ,b *anges at e half turn ( ! coil1 & h5ce ! direction ( ! curr5t ?r\gh ! coil *anges p]iodically4 ,z a result ! coil rotates cont9u\sly1 & produces motion s long z curr5t is suppli$ f )\t4 #caa4 ,! ,practical ,motor4 ,a motor con/ruct$ 9 accordance ) ,section #cji w\ld be ( little value 9 practical ev]yday affairs2 its armature rotates too sl[ly & ) too little =ce4 ,if a motor is to be ( real s]vice1 its armature mu/ rotate ) suffici5t /r5g? to imp>t motion to ! :eels ( trolley c>s & mills1 to drive electric fans1 & to set into activity _m o!r =ms ( ma*9]y4 ,! /r5g? ( a motor may be increas$ by replac+ ! s+ly coil$ armature by "o closely w\nd on an iron core2 9 "s armatures !re are ?\s&s ( turns ( wire4 ,! pres5ce ( s(t iron )9 ! armature 7,section #bif7 causes great] attraction betwe5 ! armature & ! outside magnet1 & h5ce great] =ce ( motion4 ,! magnetic /r5g? ( ! field magnet influ5ces greatly ! spe$ ( ! armature2 ! /rong] ! field magnet ! great] ! motion1 s electricians make e ef=t to /r5g!n _! field magnets4 ,! /ronge/ kn[n magnets are electromagnets1 :i*1 z we h se51 are m]ely coils ( wire w\nd on an iron core4 ,= ?is reason1 ! field magnet is usually an electromagnet4 ,:5 v p[]ful motors are necess>y1 ! field magnet is s arrang$ t x has f\r or m poles in/ead ( two2 ! armature likewise consi/s ( sev]al portions1 & ev5 ! commutator may be v complex4 ,b no matt] h[ complex ^! v>i\s p>ts may seem to be1 ! pr9ciple is always t /at$ 9 ,section #cji1 & ! p>ts are limit$ to field magnet1 commutator1 & armature4 ,illu/ration3 ,,fig4 #bca4--;,a mod]n p[] plant4 ,illu/ration3 ,,fig4 #bcb4--,! electric /reet c>4 ,! motor is ( value because by means ( x motion1 or me*anical en]gy1 is obta9$ f an electric curr5t4 ,ne>ly all electric /reet c>s 7,fig4 #bcb71 are set 9 motion by p[]ful motors plac$ "u ! c>s4 ,z ! armature rotates1 its motion is communicat$ by ge>s to ! :eels1 ! necess>y curr5t rea*+ ! motor ?r\gh ! ov]head wires4 ,small motors may be us$ to great advantage 9 ! home1 :]e !y s]ve to turn ! :eels ( sew+ ma*9es1 & to op]ate wa%+ ma*9es4 ,vacuum clean]s are frequ5tly run by motors4 ,,*apt] ,,xxxiv ,,h[ ,,electricity ,,may ,,be ,,measur$ #cab4 ,dang] ( an ,ov]supply ( ,curr5t4 ,if a small toy motor is connect$ ) "o cell1 x rotates sl[ly2 if connect$ ) two cells1 x rotates m rapidly1 & 9 g5]al1 ! great] ! numb] ( cells us$1 ! /rong] w be ! action ( ! motor4 ,b x is possible to s5d too /rong a curr5t ?r\gh our wire1 !reby int]f]+ ) all motion & de/roy+ ! motor4 ,we h se5 9 ,section #bhh t ! am\nt ( curr5t :i* c safely fl[ ?r\gh a wire dep5ds ^u ! ?ickness ( ! wire4 ,a /rong curr5t s5t ?r\gh a f9e wire has its electrical en]gy trans=m$ l>gely into heat2 & if ! curr5t is v /rong1 ! heat develop$ may be suffici5t to burn (f ! insulation & melt ! wire itself4 ,?is is true n only ( motors1 b ( all electric ma*9]y 9 :i* !re are curr5t-be>+ wires4 ,! curr5t %\ld n be great] ?an ! wires c c>ry1 o!rwise too mu* heat w be develop$ & damage w be done to in/rum5ts & surr\nd+s4 ,! curr5t s5t ?r\gh our electric /oves & irons %\ld be /rong en\gh to heat ! coils1 b n /rong en\gh to melt !m4 ,if ! curr5t s5t ?r\gh our electric light wires is too great = ! capacity ( ! wires1 ! heat develop$ w injure ! wires & may cause disa/r\s results4 ,! ov]load+ ( wires is responsible = _m disa/r\s fires4 ,! dang] ( ov]load+ may be elim9at$ by ins]t+ 9 ! circuit a fuse or o!r safety device4 ,a fuse is made by comb9+ a numb] ( metals 9 su* a way t ! result+ sub/ance has a l[ melt+ po9t & a high electrical resi/ance4 ,a fuse is ins]t$ 9 ! circuit1 & ! in/ant ! curr5t increases beyond its normal am\nt ! fuse melts1 breaks ! circuit1 & ?us protects ! rema9+ "p ( ! circuit f ! dang] ( an ov]load4 ,9 ?is way1 a circuit design$ to c>ry a c]ta9 curr5t is protect$ f ! dang] ( an accid5tal ov]load4 ,! noise made by ! burn+ out ( a fuse 9 a trolley c> frequ5tly al>ms pass5g]s1 b x is really a sign t ! sy/em is 9 good work+ ord] & t !re is no dang] ( accid5t f too /rong a curr5t4 #cac4 ,h[ ,curr5t is ,measur$4 ,! prec$+ ,section has %[n cle>ly ! dang] ( too /rong a curr5t1 & ! necessity = limit+ ! curr5t to t :i* ! wire c safely c>ry4 ,!re are times :5 x is desirable to "k accurately ! /r5g? ( a curr5t1 n only 9 ord] to gu>d aga9/ an ov]load1 b also 9 ord] to det]m9e 9 advance ! me*anical & *emical effects :i* w be produc$ by ! curr5t4 ,= example1 ! /r5g? ( ! curr5t det]m9es ! ?ickness ( ! coat+ ( silv] :i* =ms 9 a giv5 "t on a spoon plac$ 9 an electrolytic ba?2 if ! curr5t is weak1 a ?9 plat+ is made on ! spoon2 if ! curr5t is /rong1 a ?ick plat+ is made4 ,if1 !re=e1 ! exact value ( ! curr5t is kn[n1 ! exact am\nt ( silv] :i* w be deposit$ on ! spoon 9 a giv5 "t c be def9itely calculat$4 ,illu/ration3 ,,fig4 #bcc4--,! pr9ciple ( ! galvanomet]4 ,curr5t-measur+ in/rum5ts1 or galvanomet]s1 dep5d = _! action on ! magnetic prop]ties ( curr5t electricity4 ,! pr9ciple ( practically all galvanomet]s is z foll[s3-- ,a closely w\nd coil ( f9e wire free to rotate is susp5d$ z 9 ,figure #bcc betwe5 ! poles ( a /rong magnet4 ,:5 a curr5t is s5t ?r\gh ! coil1 ! coil becomes a magnet & turns s t its faces w be t[>ds ! poles ( ! p]man5t magnet4 ,b z ! coil turns1 ! susp5d+ wire becomes twi/$ & h9d]s ! turn+4 ,= ?is reason1 ! coil c turn only until ! motion caus$ by ! curr5t is balanc$ by ! twi/ ( ! susp5d+ wire4 ,b ! /rong] ! curr5t ?r\gh ! coil1 ! /rong] w be ! =ce t5d+ to rotate ! coil1 & h5ce ! less effective w be ! h9drance ( ! twi/+ /r+4 ,z a consequ5ce1 ! coil sw+s f>!r ?an be=e2 t is1 ! great] ! curr5t1 ! f>!r ! sw+4 ,usually a delicate po9t] is atta*$ to ! movable coil & rotates freely ) x1 s t ! sw+ ( ! po9t] indicates ! relative values ( ! curr5t4 ,if ! s\rce ( ! curr5t is a gravity cell1 ! sw+ is only two ?irds z great z :5 a dry cell is us$1 indicat+ t ! dry cell furni%es ab\t #a-a_/b times z mu* curr5t z a gravity cell4 #cad4 ,ammet]s4 ,a galvanomet] does n measure ! curr5t1 b m]ely indicates ! relative /r5g? ( diff]5t curr5ts4 ,b x is desirable at times to measure a curr5t 9 units4 ,in/rum5ts = measur+ ! /r5g? ( curr5ts 9 units are call$ ammet]s1 & ! common =m makes use ( a galvanomet]4 ,a curr5t is s5t ?r\gh a movable coil 7! field magnet & coil are inclos$ 9 ! case7 7,fig4 #bcd71 & ! magnetic field ?us develop$ causes ! coil to turn1 & ! po9t] atta*$ to x to move ov] a scale graduat$ s t x reads curr5t /r5g?s4 ,?is scale is c>efully graduat$ by ! foll[+ me?od4 ,if two silv] rods 7,fig4 #bjh7 are weigh$ & plac$ 9 a solution ( silv] nitrate1 & curr5t f a s+le cell is pass$ ?r\gh ! liquid = a def9ite "t1 we f9d1 on weigh+ ! two rods1 t "o has ga9$ 9 weight & ! o!r has lo/4 ,if ! curr5t is all[$ to fl[ twice z long1 ! am\nt ( silv] lo/ & ga9$ by ! electrodes is d\bl$2 & if twice ! curr5t is us$1 ! result is aga9 d\bl$4 ,z a result ( num]\s exp]im5ts1 x 0 f\nd t a def9ite curr5t ( electricity w deposit a def9ite am\nt ( silv] 9 a def9ite "t1 & t ! am\nt ( silv] deposit$ on an electrode 9 "o second might be us$ to measure ! curr5t ( electricity :i* has fl[$ ?r\gh ! circuit 9 "o second4 ,a curr5t is said to be "o amp]e /rong if x w deposit silv] on an electrode at ! rate ( #j4jjaaah gram p] second4 ,illu/ration3 ,,fig4 #bcd4--;,an ammet]4 ,9 m>k+ ! scale1 an ammet] is plac$ 9 ! circuit ( an electrolytic cell & ! position ( ! po9t] is m>k$ on ! blank c>d :i* lies b5ea? & :i* is to s]ve z a scale 7,fig4 #bce74 ,aft] ! curr5t has fl[$ = ab\t an h\r1 ! am\nt ( silv] :i* has be5 deposit$ is measur$4 ,kn[+ ! "t dur+ :i* ! curr5t has run1 & ! am\nt ( deposit1 ! /r5g? ( ! curr5t 9 amp]es c be calculat$4 ,?is numb] is writt5 opposite ! place at :i* ! po9t] /ood dur+ ! exp]im5t4 ,! scale may be complet$ by m>k+ ! positions ( ! po9t] :5 o!r curr5ts ( kn[n /r5g? fl[ ?r\gh ! ammet]4 ,illu/ration3 ,,fig4 #bce4--,m>k+ ! scale ( an ammet]4 ,all electric plants1 :e!r = heat+1 light+1 or = ma*9]y1 are provid$ ) ammet]s1 su* in/rum5ts be+ z important to an electric plant z ! /eam gauge is to ! boil]4 #cae4 ,voltage & ,voltmet]s4 ,s9ce electromotive =ce1 or voltage1 is ! cause ( curr5t1 x %\ld be possible to comp>e diff]5t electromotive =ces by comp>+ ! curr5ts :i* !y produce 9 a giv5 circuit4 ,b two voltages ( equal value d n give equal curr5ts unless ! resi/ances met by ! curr5ts are equal4 ,= example1 ! simple voltaic cell & ! gravity cell h approximately equal voltages1 b ! curr5t produc$ by ! voltaic cell is /rong] ?an t produc$ by ! gravity cell4 ,?is is because ! curr5t meets m resi/ance )9 ! gravity cell ?an )9 ! voltaic cell4 ,e cell1 no matt] :at its nature1 (f]s resi/ance to ! fl[ ( electricity ?r\gh x & is said to h int]nal resi/ance4 ,if we are det]m9+ ! voltages ( v>i\s cells by a comp>ison ( ! respective curr5ts produc$1 ! result w be true only on condition t ! resi/ances 9 ! v>i\s circuits are equal4 ,if a v l>ge ext]nal resi/ance ( f9e wire is plac$ 9 circuit ) a gravity cell1 ! total resi/ance ( ! circuit 7made up ( ! relatively small resi/ance 9 ! cell & ! l>g] resi/ance 9 ! re/ ( ! circuit7 w diff] b little f t ( ano!r circuit 9 :i* ! gravity cell is replac$ by a voltaic cell1 or any o!r type ( cell4 ,) a high resi/ance 9 ! outside circuit1 ! deflections ( ! ammet] w be small1 b su* z !y are1 !y w fairly accurately repres5t ! electromotive =ces :i* produce !m4 ,voltmet]s 7,fig4 #bcf71 or in/rum5ts = measur+ voltage1 are l ammet]s except t a wire ( v high resi/ance is 9 circuit ) ! movable coil4 ,9 ext]nal appe>ance !y are n di/+ui%able f ammet]s4 ,illu/ration3 ,,fig4 #bcf4--;,a voltmet]4 ,! unit ( electromotive =ce is call$ ! volt4 ,! voltage ( a dry cell is approximately #a4e volts1 & ! voltage ( a voltaic cell & ( a gravity cell is approximately #a volt4 #caf4 ,curr5t1 ,voltage1 ,resi/ance4 ,we le>n$ 9 ,section #bhg t ! /r5g? ( a curr5t increases :5 ! electromotive =ce increases1 & dim9i%es :5 ! electromotive =ce dim9i%es4 ,lat]1 9 ,section #bhh1 we le>n$ t ! /r5g? ( ! curr5t decreases z ! resi/ance 9 circuit increases4 ,! /r5g? ( a /eady curr5t dep5ds ^u ^! two factors only1 ! electromotive =ce :i* causes x & ! resi/ance :i* x has to ov]come4 #cag4 ,resi/ance4 ,s9ce resi/ance plays s important a rle 9 electricity1 x becomes necess>y to h a unit ( resi/ance4 ,! practical unit ( resi/ance is call$ an ohm1 & "s idea ( ! value ( an ohm c be obta9$ if we rememb] t a #cjj-;foot l5g? ( common iron telegraph wire has a resi/ance ( #a ohm4 ,an approximate ohm = r\gh "w 9 ! laboratory may be made by w9d+ #i feet #e in*es ( numb] #cj copp] wire on a spool or arrang+ x 9 any o!r conv5i5t =m4 ,9 ,section #bii we le>n$ t sub/ances diff] v greatly 9 ! resi/ance :i* !y (f] to electricity1 & s x w n surprise u to le>n t :ile x takes #cjj feet ( iron telegraph wire to give #a ohm ( resi/ance1 x takes b #ci feet ( numb] #bd copp] wire1 & b #b4b feet ( numb] #bd ,g]man silv] wire1 to give ! same resi/ance4 ,,note4 ,! numb] ( a wire indicates its diamet]2 numb] #cj1 = example1 be+ always ( a def9ite fix$ diamet]1 no matt] :at ! mat]ial ( ! wire4 ,if we wi% to avoid loss ( curr5t by heat+1 we use a wire ( l[ resi/ance2 :ile if we wi% to trans=m electricity into heat1 z 9 ! electric /ove1 we *oose wire ( high resi/ance1 z ,g]man silv] wire4 ,,*apt] ,,xxxv ,,h[ ,,electricity ,,is ,,obta9$ ,,on ,a ,,l>ge ,,scale #cah4 ,! ,dynamo4 ,we h le>n$ t cells furni% curr5t z a result ( *emical action1 & t ! sub/ance usually consum$ )9 ! cell is z9c4 ,j z coal )9 ! furnace furni%es heat1 s z9c )9 ! cell furni%es electricity4 ,b z9c is a mu* m exp5sive fuel ?an coal or oil or gas1 & to run a l>ge motor by electricity produc$ 9 ?is way w\ld be v mu* m exp5sive ?an to run ! motor by wat] or /eam4 ,= weak & infrequ5t curr5ts su* z are us$ 9 ! electric bell1 only small quantities ( z9c are ne$$1 & ! exp5se is small4 ,b = ! production ( su* p[]ful curr5ts z are ne$$ to drive trolley c>s1 elevators1 & huge ma*9]y1 enorm\s quantities ( z9c w\ld be necess>y & ! co/ w\ld be prohibitive4 ,x is safe to say t electricity w\ld nev] h be5 us$ on a l>ge scale if "s less exp5sive & m conv5i5t s\rce ?an z9c _h n be5 f\nd4 #cai4 ,a ,new ,s\rce ( ,electricity4 ,x came to mo/ ( u z a surprise t an electric curr5t has magnetic prop]ties & trans=ms a coil into a v]itable magnet4 ,p]haps x w n surprise u n[ to le>n t a magnet 9 motion has electric prop]ties & is1 9 fact1 able to produce a curr5t )9 a wire4 ,?is c be prov$ z foll[s3-- ,illu/ration3 ,,fig4 #bcg4--,! motion ( a magnet )9 a coil ( wire produces a curr5t ( electricity4 ,atta* a closely w\nd coil to a s5sitive galvanomet] 7,fig4 #bcg72 naturally !re is no deflection ( ! galvanomet] ne$le1 because !re is no curr5t 9 ! wire4 ,n[ ?ru/ a magnet into ! coil4 ,imm$iately !re is a deflection ( ! ne$le1 :i* indicates t a curr5t is fl[+ ?r\gh ! circuit4 ,if ! magnet is all[$ to rema9 at re/ )9 ! coil1 ! ne$le returns to its z]o position1 %[+ t ! curr5t has ceas$4 ,n[ let ! magnet be )drawn f ! coil2 ! ne$le is deflect$ z be=e1 b ! deflection is 9 ! opposite direction1 %[+ t a curr5t exi/s1 b t x fl[s 9 ! opposite direction4 ,we le>n1 !re=e1 t a curr5t may be induc$ 9 a coil by mov+ a magnet back & =? )9 ! coil1 b t a magnet at re/ )9 ! coil has no su* influ5ce4 ,an electric curr5t trans=ms a coil into a magnet4 ,a magnet 9 motion induces electricity )9 a coil2 t is1 causes a curr5t to fl[ ?r\gh ! coil4 ,a magnet possesses l9es ( =ce1 & z ! magnet moves t[>d ! coil x c>ries l9es ( =ce ) x1 & ! coil is cut1 s to speak1 by ^! l9es ( =ce4 ,z ! magnet rec$es f ! coil1 x c>ries l9es ( =ce away ) x1 ?is "t r$uc+ ! numb] ( ! l9es :i* cut ! coil4 ,illu/ration3 ,,fig4 #bch4--;,z long z ! coil rotates betwe5 ! poles ( ! magnet1 curr5t fl[s4 #cbj4 ,a ,te/ ( ! ,prec$+ ,/atem5t4 ,we w te/ ! /atem5t t a magnet has electric prop]ties by ano!r exp]im5t4 ,betwe5 ! poles ( a /rong magnet susp5d a movable coil :i* is connect$ ) a s5sitive galvanomet] 7,fig4 #bcg74 ,/>t+ ) ! coil 9 ! position ( ,figure #bbh1 :5 _m l9es ( =ce pass ?r\gh x1 let ! coil be rotat$ quickly until x rea*es ! position indicat$ 9 ,figure #bch1 :5 no l9es ( =ce pass ?r\gh x4 ,dur+ ! motion ( ! coil1 a /rong deflection ( ! galvanomet] is obs]v$2 b ! deflection ceases z soon z ! coil ceases to rotate4 ,if1 n[1 />t+ ) ! position ( ,figure #bch1 ! coil is rotat$ =w>d to its />t+ po9t1 a deflection occurs 9 ! opposite direction1 %[+ t a curr5t is pres5t1 b t x fl[s 9 ! opposite direction4 ,s long z ! coil is 9 motion1 x is cut by a v>y+ numb] ( l9es ( =ce1 & curr5t is induc$ 9 ! coil4 ,! above arrangem5t is a dynamo 9 m9iature4 ,by rotation ( a coil 7armature7 )9 a magnetic field1 t is1 betwe5 ! poles ( a magnet1 curr5t is obta9$4 ,9 ! motor1 curr5t produces motion4 ,9 ! dynamo1 motion produces curr5t4 #cba4 ,! ,dynamo4 ,z has be5 said1 ! arrangem5t ( ! prec$+ ,section is a dynamo 9 m9iature4 ,e dynamo1 no matt] h[ complex its /ructure & appe>ance1 consi/s ( a coil ( wire :i* c rotate cont9u\sly betwe5 ! poles ( a /rong magnet4 ,! me*anical devices to insure easy rotation are simil> 9 all respects to ^? previ\sly describ$ = ! motor4 ,illu/ration3 ,,fig4 #bci4--;,a mod]n electrical ma*9e4 ,! curr5t obta9$ f su* a dynamo alt]nates 9 direction1 fl[+ fir/ 9 "o direction & !n 9 ! opposite direction4 ,su* alt]nat+ curr5ts are unsatisfactory = _m purposes1 & to be ( s]vice are 9 _m cases trans=m$ into direct curr5ts2 t is1 curr5t :i* fl[s /eadily 9 "o direction4 ,?is is accompli%$ by ! use ( a commutator4 ,9 ! con/ruction ( ! motor1 cont9u\s motion 9 "o direction is obta9$ by ! use ( a commutator 7,section #caj72 9 ! con/ruction ( a dynamo1 cont9u\s curr5t 9 "o direction is obta9$ by ! use ( a simil> device4 #cbb4 ,p[]ful ,dynamos4 ,! p[] & effici5cy ( a dynamo are increas$ by employ+ ! devices previ\sly m5tion$ 9 connection ) ! motor4 ,electromagnets are us$ 9 place ( simple magnets1 & ! armature1 in/ead ( be+ a simple coil1 may be made up ( _m coils w\nd on s(t iron4 ,! spe$ ) :i* ! armature is rotat$ influ5ces ! /r5g? ( ! induc$ curr5t1 & h5ce ! armature is run at high spe$4 ,illu/ration3 ,,fig4 #bdj4--,?omas ,edison1 "o ( ! =emo/ electrical inv5tors ( ! pres5t day4 ,a small dynamo1 su* z is us$ = light+ fifty inc&esc5t lamps1 has a horse p[] ( ab\t #cc4e1 & l>ge dynamos are frequ5tly z p[]ful z #gejj horse p[]4 #cbc4 ,! ,telephone4 ,:5 a magnet is at re/ )9 a clos$ coil ( wire1 z 9 ,section #cai1 curr5t does n fl[ ?r\gh ! wire4 ,b if a piece ( iron is br\ght ne> ! magnet1 curr5t is induc$ & fl[s ?r\gh ! wire2 if ! iron is )drawn1 curr5t is aga9 induc$ 9 ! wire b fl[s 9 ! opposite direction4 ,z iron approa*es & rec$es f ! magnet1 curr5t is induc$ 9 ! wire surr\nd+ ! magnet4 ,?is is 9 brief ! pr9ciple ( ! telephone4 ,:5 "o talks into a receiv]1 ,l1 ! voice ?r[s into vibration a s5sitive iron plate /&+ be=e an electromagnet4 ,! back & =? motion ( ! iron plate induces curr5t 9 ! electromagnet c4 ,! curr5t ?us induc$ makes itself evid5t at ! opposite end ( ! l9e ,m1 :]e by its magnetic attraction1 x ?r[s a second iron plate into vibrations4 ,! vibrations ( ! second plate are simil> to ^? produc$ 9 ! fir/ plate by ! voice4 ,! vibrations ( ! f> plate ?us reproduce ! s\nds utt]$ at ! opposite end4 ,illu/ration3 ,,fig4 #bda4--;,diagram ( a simple telephone circuit4 #cbd4 ,co/ ( ,electric ,p[]4 ,! wat] p[] ( a /ream dep5ds ^u ! quantity ( wat] & ! =ce ) :i* x fl[s4 ,! electric p[] ( a curr5t dep5ds ^u ! quantity ( electricity & ! =ce "u :i* x fl[s4 ,! unit ( electric p[] is call$ ! watt2 x is ! p[] furni%$ by a curr5t ( "o amp]e ) a voltage ( "o volt4 ,"o watt repres5ts a v small am\nt ( electric p[]1 & = practical purposes a unit #ajjj times z l>ge is us$1 namely1 ! kil[att4 ,by exp]im5t x has be5 f\nd t "o kil[att is equival5t to ab\t #a-a_/c horse p[]4 ,electric curr5t is *>g$ = by ! watt h\r4 ,a curr5t ( "o amp]e1 hav+ a voltage ( "o volt1 w furni% 9 ! c\rse ( "o h\r "o watt h\r ( en]gy4 ,en]gy = electric light+ is sold at ! rate ( ab\t t5 c5ts p] kil[att h\r4 ,= o!r purposes x is less exp5sive4 ,! met]s commonly us$ measure ! amp]es1 volts1 & "t automatically1 & regi/] ! electric p[] suppli$ 9 watt h\rs4 ,,index ,absorption1 ( heat by lampblack1 #adc-add4 ( gases by *>coal1 #eg4 ( light waves1 #ace-ach4 ,accommodation ( ! eye1 #abc4 ,acetanilid1 #bei4 ,acetyl5e1 z illum9ant1 #aeb-aec4 manufacture (1 #aeb-aec4 prop]ties (1 #bbj4 ,acid1 boric1 #bec4 c>bolic1 #aeb1 #bea1 #beb4 hydro*loric1 #ee1 #hj1 #bbg1 #bch1 #bda4 lactic1 #bcj4 oxalic1 #bdg1 #bdh4 salicylic1 #bec4 sulphuric1 #ee1 #hj1 #bdj1 #bda1 #cjg4 sulphur\s1 #bdb4 ,acids1 action on litmus1 #bbj4 ,ad5oids1 #ea4 ,adult]ants1 detection (1 #af4 ,air1 *>act]i/ics (1 #ha-hc1 #hf1 #ahi4 compressibility (1 #ia4 expansion (1 #aj-aa4 humidity1 #ch1 #ci4 pumps1 #bja-bje4 transmits s\nd1 #bfi4 weight (1 #hf4 ,see ,atmosph]e4 ,alcohol1 #bcd4 9 pat5t m$ic9es1 #bfj4 ,aliz>91 #bdh4 ,alkali1 #bbb4 ,alt]nat+ curr5t1 #cea4 ,alum1 #bdg4 9 bak+ p[d]1 #bcj4 ,ammet]1 #cda1 #cdc4 ,ammonia1 #aeb4 a base1 #bba-bbb4 9 ba?1 #bbf4 9 manufacture ( ice1 #ih4 neutraliz+ *lor9e1 #bdj4 ,amp]e1 #cdb4 ,anemia1 #bei4 ,angle1 ( incid5ce1 #aaj4 ( reflection1 #aaj4 ( refraction1 #aad4 ,anil9e1 #aeb1 #bde4 ,animal *>coal1 #eh4 ,animal transportation1 #acb4 ,anti*lor1 #bdj4 ,antipyr91 #bei4 ,armature1 #cai1 #cbj4 dynamo1 #cej4 motor1 #cce4 ,artificial light+1 #adh-aec4 ,atmosph]e1 #ha4 c>bon dioxide 91 #ed-ee4 height (1 #ha4 nitrog5 & oxyg5 91 #bfb4 pressure (1 #hb-hf4 wat] vapor 91 #cf-ch4 weight1 #hf4 ,see ,air4 ,atmosph]ic pressure1 #hb-hf4 ,atomiz]1 #ib4 ,atoms1 #ajb4 ,automobiles1 gas eng9es1 #ahe4 ,axis ( a l5s1 #aai4 ,bact]ia1 #acc4 z nitrog5 mak]s1 #bfc4 de/roy$ by sunlight1 etc41 #acc1 #bej1 #bea4 diseases caus$ by1 #acc4 9 butt] & *eese1 #acc4 ,bak+ p[d]1 #bbi-bcj4 ,bak+ soda1 #bbg-bbi4 ,b>ograph1 #hg4 ,b>omet]1 an]oid1 #hd-he4 m]cury1 #hd4 use 9 wea!r pr$ictions1 #hf-hg4 ,bases1 action on litmus1 #bba-bbb4 prop]ties1 #bbj-bbb4 ,batt]y1 electric1 #caa4 ,beans1 z food1 #ff4 roots take 9 nitrog51 #bfc4 ,bell1 electric1 #cai-cba4 ,b5z9e1 #aej4 z a clean+ ag5t1 #bbg4 ,b5zoate ( soda1 #bec4 ,bic>bonate ( soda1 9 fire ext+ui%]1 #ee1 #ef4 9 ,ro*elle salt1 #bbg4 9 soda m9ts1 #bca4 9 seidlitz p[d]1 #bca4 ,bicycle pumps1 #bjb4 ,bla/+1 by electricity1 #cad4 ,blea*+1 #bcg-bdc4 by *lor9e1 #bch-bdj4 ,blea*+ p[d]1 #bci-bdj4 ,body1 human1 #fc-fd4 a conductor ( electricity1 #bib4 ,boil+1 #ca4 am\nt ( heat absorb$1 #ca-cb4 ( milk1 #cb4 ( wat]1 #gg4 po9t1 #ae4 ,bomb calorimet]1 #fa4 ,borax1 z meat pres]vative1 #bec4 z wa%+ p[d]1 #bbf4 ,boric acid1 z meat pres]vative1 #bec4 ,boyle's law1 #ie-if4 ,bread1 #bcb-bcc4 unleav5$1 #bcc4 ,bread mak+1 #bcb-bce4 ,brea?+1 hygi5ic habits (1 #ej4 by m\?1 #ej-ea4 ,burns1 treatm5t (1 #eb-ec4 ,butt]1 adult]ation te/1 #af4 bact]ia 91 #acc4 ,butt]milk1 #bcj4 ,caisson1 #bjc-bjd4 ,calcium c>bide1 #aeb-aec4 9 mak+ nitrog5\s f]tiliz]1 #bfd4 ,calico pr9t+1 #bdi4 ,calorie1 #bg-bh1 #fa-fb4 ,calorimet]1 #fa4 ,cam]a1 #abh-abi4 films1 #abi4 l5s1 #abi4 plates1 #abi4 ,camp+1 wat] supply1 #aie-aig4 ,c&le1 #adh-adi4 z /&>d = light-measure1 #ajd-aje4 ,c&le-p[]1 #aje-ajg4 ,c>bide1 calcium1 #aeb-aec1 #bfd4 ,c>bohydrates1 #fd-fe1 #adi4 ,c>bolic acid1 #aeb4 z dis9fectant1 #bea4 ,c>bon1 #ef1 #ff4 9 voltaic cells1 #cjh4 ,c>bon dioxide1 #ec4 z fire ext+ui%]1 #ee-ef4 comm]cial use1 #ee-ef4 9 bak+ soda1 #bbh4 9 f]m5tation1 #bcd4 9 heal?1 #ed4 9 plants1 #ee4 prep>ation (1 #ee4 s\rce (1 #ec4 te/ =1 #bbh4 ,cat>rh1 #bei4 ,cau/ic lime1 #bbb44 ,cau/ic pota%1 #bbb4 ,cau/ic soda1 #bah1 #bbb4 to make a salt1 #bbg4 ,caves & cav]ns1 #ga4 ,cell1 dry1 #caj4 gravity1 #cji-caj4 voltaic1 #cjf-cjh1 #caj4 ,cells ( human body1 #fc1 #fd1 #ff4 ,c5tigrade !rmomet]1 #ae4 ,c5tral heat+ plant1 #ai4 ,*alk1 9 mak+ c>bon dioxide1 #ee4 ,*>coal z a filt]1 #eg4 comm]cially1 #eg4 prep>ation1 #eg-eh4 ,*emical action1 & electricity1 #cjg1 #cae-cag4 & light1 #abf1 #abg4 ,*emi/ry1 9 daily life1 #bah1 #bai4 ,*ills1 #ch4 ,*loride ( lime1 9 blea*+1 #bdj4 dis9fectant1 #bea4 ,*lor9e1 & hydrog51 #bci4 effect ^u human body1 #bci4 9 blea*+1 #bch-bdj4 influ5ce ( light ^u1 #abf4 pres5ce 9 salt1 #bbg4 ,circuit1 electric1 #cba4 local1 9 telegraph1 #cbe-cbf4 ,city wat] supply1 #bjf-bab4 ,cl>9et1 #big4 ,clean+ ( mat]ial1 #bbf1 #bdc4 ,climate1 influ5c$ by pres5ce ( wat]1 #bi1 #dj4 ,clov]1 nitrog5 produc]s1 #bfc4 ,coal1 #cj4 ,coal gas1 #aej1 #aea4 by-products1 #aeb4 ,coal oil1 #adi1 #aej4 ,coal t> dyes1 #aeb1 #bah1 #bde4 ,cog:eels1 #agj4 ,coil1 curr5t-be>+1 #cbj4 magnetic field ab\t1 #cca-ccc4 ,coke1 #aeb4 ,cold /orage1 #ig4 ,color1 #acd-ada4 & heat1 #adb1 #adc4 influ5c$ by light1 #acg4 ( opaque bodies1 #acf1 #acg4 ( transp>5t bodies1 #ace1 #acf4 ,color bl9dness1 #adj1 #ada4 designs 9 clo?1 #bdh1 #bdi4 ,colors1 comp\nd1 #ach1 #aci4 ess5tial1 #aci-adj4 prim>y1 #ace4 simple1 #ach4 spectrum1 #acd-ace4 v>iety 9 dye+1 #bdg1 #bdh4 ,combu/ion1 heat (1 #de4 spontane\s1 #eb4 ,commutator1 #cce4 ,compass1 #cbh4 ,comp\nd colors1 #ach1 #aci4 ,comp\nd ma*9e1 #aga4 ,comp\nd sub/ances1 #ajc4 ,compression ( air1 #ia1 #ib4 cause ( heat1 #if4 ,compression pumps1 #bja1 #bje4 ,concave l5s1 #aah4 ,cond5sation1 #cc4 heat set free1 #dj4 ,conduction ( heat1 #be4 ,conductivity metals1 #cba4 ,conductors1 electric1 #cba1 #cbb4 ,cons]vation1 ( en]gy1 #eh1 #ei4 ( matt]1 #eh1 #ei4 ,convection1 #bd1 #be4 ,convex l5s1 #aah4 ,cool+1 by evaporation1 #ce-cf4 by expansion1 #ig4 ,copp]1 9 electric cell1 #cjg4 ,core1 iron1 #cai4 ,corn1 blea*$ ) sulphur\s acid1 #bdb4 ,cotton1 m]c]iz$1 #bah4 blea*+1 #bda4 dye+1 #bde-bdg4 ,c\gh sirup1 #beh4 ,crane1 comp\nd ma*9e1 #agb4 ,cream ( t>t>1 #bbi4 ,creosote oil1 #bed4 ,crude petroleum1 #adi1 #aej4 ,curr5t1 electric1 #cjf1 #cab4 alt]nat+1 #cdi4 induc$1 #cdf-cdg4 measurem5t (1 #cdj4 resi/ance1 #cab1 #cdc1 #cde4 /r5g?1 #cci1 #cdj1 #cdd4 ,dams1 #bad-baf4 ,decay1 #di4 ,decomposition ( soil by wat]1 #gj-gd4 ,degrees ,fahr5heit & ,c5tigrade1 #ae4 ,d5sity1 #aa4 ,designs 9 clo?1 pr9t$1 #bdh1 #bdi4 wov51 #bdi4 ,develop] 9 photography1 #abh4 ,dew1 #cf1 #cg4 ,dew po9t1 #ch4 ,di>rhea1 #bea4 ,diet1 #fb1 #ff4 economy on table1 #ff-fi4 ,discord1 reason =1 #bga4 ,disease1 & surface wat]1 #gf4 relation ( light to1 #aca-acb4 ,disease dis9fectants1 #bej1 #bea1 #beb4 ,di/illation1 #cd-ce4 9 comm]ce1 #ce4 ( petroleum1 #adi-aej4 ( s(t coal1 #aej4 ( wat]1 #cd1 #ce1 #gg4 ,div+ suits1 #bjd4 ,door bells1 #cai-cba4 ,dra9age1 ( l&1 #aid1 #aie4 sewage1 #aif1 #aih1 #aii1 #bja4 ,drill$ well1 #aii4 ,dr9k+ wat]1 #ge-gg4 9 camp+1 #aie-aif4 & rural supplies1 #aih1 #bja4 ,driv5 well1 #aif-aig4 ,dr\ght1 #bag4 ,drugs1 #bee1 #bfj4 ,dry cell1 #cab4 ,dye+1 #bdd-bdi4 color designs1 #bdh4 ,dye+1 direct1 #bde4 home1 #bdg4 indirect1 #bdg4 v>iety ( color1 #bdg4 ,dyes1 #bah1 #bdd1 #bde4 ,dynamo1 #cdf4 alt]nat+ curr5t1 #cdi4 s\rce ( en]gy1 #cdf-cdg4 ,e>1 9 man1 #cja-cjc4 c>e (1 #cjc4 ,e>?1 conductor ( electricity1 #cbf4 ,e*o1 #bgg4 ,economy 9 buy+ food1 #ff-fi4 ,ef=t1 muscul>1 #aee1 #afj4 ,electric1 batt]y1 #caa4 bell1 #cai-cba4 bread toa/]s1 #cad4 conductors & non-conductors1 #cba-cbb4 co/ (1 en]gy1 #ceb4 curr5t1 #cjf1 #cab4 flatiron1 #cac4 heat+ pad1 #cad4 lights1 #cad4 /reet c>s1 #ccg4 ,electricity1 heat1 #cab-cae1 #cci4 z a magnet1 #cai1 #cca-ccc4 practical uses (1 #cab-cag4 ,electrodes1 ( cell1 #cjh4 ,electrolytic metals1 #cag4 ,electromagnets1 #cai4 ,electromotive =ce1 #cjh4 unit (1 #cdd4 ,electroplat+1 #cae4 ,electrotyp+1 #cag4 ,elem5ts1 #ajb-ajc4 ,emulsion1 #bbd4 ,en]gy1 cons]vation (1 #eh1 #ei4 trans=mations (1 #eh1 #ei4 ,eng9e1 /eam1 #ahc-ahe4 gas1 #ahe-ahf4 horse p[]1 #agc4 ,erosion1 #gc-gd4 ,ess5tial colors1 #aci-adj4 ,evaporation1 #ce-ci4 cool+ effect1 #ce-cf4 effect ( temp]ature on1 #ce1 #cf4 effect ( air on1 #ch4 freez+ by1 #ih4 heat absorb$1 #cf4 ( p]spiration1 #ch4 ,expansion1 ( air1 #aj1 #aa4 cool+ effect (1 #ig4 disadvantage & advantage (1 #aa-ac4 ( liquids1 #i-aa4 ( solids1 #aj1 #aa4 ( wat]1 #i1 #aj1 #aa1 #ab4 ,eye1 #abb-abe4 heada*e1 #abd1 #abe4 h[ focus$1 #abb1 #abc4 ne>sight$ & f>sight$1 #abc4 /ra91 #abe4 ,fahr5heit !rmomet]1 #ae4 ,fats1 #fe4 9 soap mak+1 #bbc4 ,f]m5tation1 #bcb-bcf4 by yea/1 #bcd-bcf4 ,f]ric comp\nds1 #bdh4 ,f]tiliz]s1 #bfb-bfe4 nitrog51 #bfb4 phosphorus1 #bfc1 #bfd4 pota%1 #bfc-bfe4 ,field magnet1 #ccf4 ,fil+s1 iron1 #cbi4 ,film1 photographic1 #abi4 ,filt]1 *>coal1 #eg4 ,filt]+ wat]1 #gg4 ,fire1 #i4 & oxyg51 #de1 #dg4 & t9d] box1 #dg4 mak+ (1 #ea4 primitive production (1 #dg4 produc$ by friction1 #dg4 spontane\s combu/ion1 #eb4 sores & burns1 #eb-ec4 ext+ui%]1 #ee1 #ef4 ,fireless cook]1 #be1 #bf4 ,fireplaces1 #ag1 #ah4 ,fix+1 9 photography1 #abh4 ,flame1 hydrog51 #hj4 ,flood1 ,john/[n1 #bad1 #bae4 relation to =e/s1 #bag4 ,fl\r1 self-rais+1 #bca4 ,flume1 #agg4 ,flute1 #big4 ,focal l5g?1 #aah4 ,focus1 ( l5s1 #aah4 ,fog1 #cg4 ,food1 #fj-fi4 c>bohydrates1 #fd1 #fe4 economy 9 buy+1 #ff-fi4 fats1 #fe4 fuel value (1 #fj-fb4 ne$ (1 #fc1 #fd4 pres]vatives1 #beb4 proteids1 #ff4 value1 #fg4 wa/e1 #fj4 wat] 91 #ge4 ,foot p\nd1 #agb4 ,=ce & motion1 #aef1 #aeg4 & "w1 #aef1 #aeg4 magnetic l9es (1 #cbi-cca1 #ccd4 muscul>1 #aee1 #afj4 ,=ce pumps1 #aib1 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#aej4 z clean+ ag5t1 #bbg1 #bdc4 9 gas eng9e1 #ahe1 #ahf4 ,gauge1 pressure1 #ib-id4 ,gelat91 plate & film1 #abi4 ,glass1 k9ds (1 #aai4 mold+ (1 #dj4 non-conductor1 #cba4 ,grape juice1 f]m5t$ ) millet1 #bcc4 ,gravity cell1 #cji1 #caj4 ,grease1 & lye1 #bba4 & soap mak+1 #bbc4 ,gulf ,/ream1 #bd4 ,h>d wat]1 & soap1 #bbe4 ,h>p1 #bie4 ,heada*e1 #abd1 #abe4 p[d]s1 #bei4 ,heal?1 effect ( diet1 #fb1 #fd4 ,heat1 #i4 absorb$ 9 boil+1 #ca-cb4 & disease g]ms1 #bej4 & food1 #beb4 & friction1 #dg4 & light1 #adb1 #adg4 & oxidation1 #de1 #dh1 #di4 & wave motion1 #ade-adg4 conduction1 #be4 convection1 #bd1 #be4 f burn+ hydrog51 #hj4 f electricity1 #cab-cae1 #cci4 ne$$ to melt sub/ances1 #ci4 ( fusion1 #dj4 ( vaporization1 #cb4 produc$ by compression1 #if4 relation ( wat] to wea!r1 #bi1 #dj4 set free by freez+ wat]1 #dj4 s\rces (1 #bi-cj4 specific1 #bh-bi4 temp]ature1 #bg4 unit (1 #bg1 #bh4 ,heat+ effect ( electric curr5t1 #cab-cae4 ,heat+ ( build+s3 c5tral heat+ plant1 #ai4 fireplaces1 #ag-ah4 ,heat+1 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#bdj1 #bea4 ,limewat]1 #bbj4 & c>bon dioxide1 #bbh4 ,l951 blea*+1 #bda4 dye+1 #bde-bdg4 ,l9es1 ( =ce1 #cbi-cca1 #ccd4 isob>ic1 #hh1 #ia4 iso!rmal1 #hi1 #ia4 ,liquefaction ( gases1 #ig1 #ih4 ,liquid air1 #ih4 ,liquid soap1 #bbc1 #bbd4 ,litmus1 action ( acids1 #bbj4 action ( bases1 #bba1 #bbb4 action ( neutral sub/ance1 #bbb4 ,logwood dyes1 #bde1 #bdg1 #bdh4 ,los ,angeles aqu$uct1 #baa4 ,lye1 #bba1 #bbb4 ,ma*9es1 comp\nd1 #aga4 incl9$ plane1 #afb-aff4 lev]1 #aeh-afb4 pulley1 #aff-afi4 :eel & axle1 #afi-aga4 ,madd]1 = dyes1 #bde4 ,magnet1 #cbh4 electro-1 #cai4 field (1 #cbi-cca4 l9es ( =ce ab\t1 #cbi-cca4 poles (1 #ccj-ccb4 prop]ties ( electricity1 #cah4 ,magnetic1 ne$le1 #cbh4 poles1 #cbi-cca4 ,magnify+ p[]1 ( a l5s1 #aae4 ( a microscope1 #aae4 ( a telescope1 #aae4 ,mammo? ,cave ( ,k5tucky1 #ga4 ,manganese dioxide1 #df4 *lor9e made f1 #bch4 oxyg5 made f1 #df4 ,m>ble1 = c>bon dioxide1 #ee4 ,mat*es1 #dg4 safety1 #dg-dh4 ,mat*+ colors1 #acg4 ,matt]1 cons]vation (1 #eh1 #ei4 ,meat1 #ff4 pres]vation (1 #bec4 ,me*anical devices1 #aed1 #aee4 ,melt+1 #ci1 #dj4 ,melt+ po9t1 #dj4 ,melt+ sub/ances )\t a def9ite melt+ po9t1 #dj4 ,m]c]iz$ cotton1 #bah4 ,m]cury1 b>omet]1 #hd4 !rmomet]1 #ad-ag4 ,metals1 electroplat+1 #cag4 pres]vation by pa9t1 #bec-bed4 ve9s deposit$ by precipitation1 #gb1 #gc4 weld+1 #cae4 ,met]1 gas1 #ic1 #id4 ,microrganisms1 #acb1 #acc4 ,microscope1 #aae4 ,milk1 boil+ po9t1 #cb4 ,pa/euriz$1 #bej4 ,m9]als1 9 foods1 #fb1 #fc4 9 wat]1 #gj1 #ga4 ,mirrors1 #ajh-aab4 di/ance ( image beh9d mirror1 #aaa4 di/ance ( object 9 front ( mirror1 #aaa4 image a duplicate ( object4 #aaa4 ,mold+ ( glass1 #dj4 ,molecule1 #ajj-ajc4 ,mordants1 #bdg1 #bdh1 #bdi4 ,morph9e1 #beg4 ,morse1 telegraphic code1 #cbd4 ,motion1 9 s\nd1 #bff1 #bgh1 #bhj4 9 "w1 #aef4 ,motor1 electric1 #ccf4 pr9ciple (1 #ccc4 /reet c>1 #ccg4 ,m\? brea?+1 #ej4 cause (1 #ea4 ,movable pulley1 #afg1 #afh4 ,music1 #bgh4 ,musical in/rum5ts1 p]cussion1 #bii4 /r+$1 #bhd-bie4 w9d1 #bie1 #bii4 ,musical scale1 #bhb4 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wood & metal pres]vatives1 #bec1 #bed4 removal ( /a9s1 #bdc4 ,pap] mak+1 #bai4 ,p>aff91 #aej1 #cba4 ,pa/euriz$ milk1 #bej4 ,pat5t m$ic9es1 #beg-bfj4 ,peas1 s\rces ( nitrog51 #bfc4 ,pelton :eel1 #agg4 ,p]cussion in/rum5ts1 #bii4 ,p]iod ( a body1 #bgc4 ,p]oxide ( hydrog51 #ec1 #beb ,petrolatum1 #aej4 ,petroleum1 #adi1 #aej4 ,phonograph1 #cjc-cje4 ,phosphorus1 9 f]tiliz]1 #bfc1 #bfd4 9 mak+ nitrog51 #bfa4 9 mat*es1 #dg1 #dh4 poison+ by1 #dg4 ,photography1 #abg-aca4 ,photomet]1 #ajg4 ,pianos1 #bhd-bib4 ,p9 :eel1 #aha4 ,pit* ( s\nd1 #bhj1 #bha4 cause (1 #bhb4 9 w9d in/rum5ts1 #bif-bii4 ,plane1 incl9$1 #afb-aff4 ,plants1 & atmosph]e1 #ee4 & light1 #aca-acb4 & nitrog51 #bfa4 ,plate develop+1 photographic1 #abh4 ,pneumatic dispat* tube1 #bje4 ,poles1 magnetic1 #ccj-ccb4 ( cell1 #cjh4 ,positive electrode1 #cjh4 ,pota%1 9 f]tiliz]1 #bfc-bfe4 ,potassium *lorate & oxyg51 #df4 p]manganate1 #ajj4 t>trate & ,ro*elle salt1 #bbg4 ,p[]1 c&le1 #aje-ajg4 electric1 #cea4 horse1 #agc1 #cea4 s\rces (1 #agd1 #age1 #ahe4 transmission by belts1 #aga4 wat]1 #agf-ahj4 ,precipitation1 #gb1 #gc4 ,pres]vatives1 food1 #beb4 wood & metal1 #bec-bed4 ,pressure1 atmosph]ic1 #hb-hf4 calculation ( atmosph]ic1 #hc1 #hd4 calculation ( gas1 #ib1 #ic4 calculation ( wat]1 #id4 gauge1 #ib-id4 ( illum9at+ gas1 #ic4 relation ( pressure ( gas to volume1 #ie1 #if4 wat] pressure1 #bjh-baa1 #bad-baf4 )9 ! body1 #hf4 ,prim>y colors1 #ace4 ,pr9t1 photographic1 #aca4 ,pr9t+1 color designs 9 clo?1 #bdh1 #bdi4 electrotype1 #cag4 ,prisms1 #ace4 refraction ?r\gh1 #aag4 ,proteids1 #ff4 ,pulleys1 #aff-afi4 applications (1 #afi4 ,pump1 #ahg-bje4 air1 #bja-bje4 =ce1 #aib1 #aic4 lift+1 #ahi-aib4 ,pupil ( ! eye1 #abb4 ,pure food laws1 blea*+1 #bdb4 pres]vatives1 #beb4 ,purification ( wat]1 #gg1 #aif4 ,pu% button1 #cba4 ,radiator1 #ai-ba4 ,railroads1 grad+ (1 #afe-aff4 ,ra91 #cf1 #cg4 ,ra9b[1 #acd4 ,ra9 wat]1 #bbe4 ,reflection1 angle (1 #aaj4 ( light1 #aji-aab4 ( s\nd1 #bgh1 #bgi4 ,refraction1 angle (1 #aad4 by atmosph]e1 #aad4 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dis9fectant1 #bea4 9 mak+ sulphur\s acid1 #bdb4 ,sulphuric acid1 9 blea*+1 #bdj1bda4 9 fire ext+ui%]1 #ee4 9 mak+ ( hydrog51 #hj4 9 voltaic cell1 #cjg4 ,sulphur\s acid1 9 blea*+1 #bdb4 prep>ation1 #bdb4 ,sun1 en]gy d]iv$ f1 #adc-add4 s\rce ( heat1 #bi-cj4 ,sunlight1 #ace4 & bact]ia1 #acc4 & *emical action1 #abf-abg4 ,sympa!tic vibrations1 #bgd-bgg4 ,tall[1 #aje1 #adh4 ,t>t>1 cream (1 #bbi4 ,telegraph1 #cbb4 long di/ance1 #cbg4 relay1 #cbe4 s\nd]1 #cbd4 ,telephone1 #cej-cea4 ,temp]ature1 #ac-ad4 z measurem5t ( heat pres5t1 #bg4 9 detect+ adult]ants1 #ag4 9 =g+ /eel1 #af4 9 mak+ sirups1 #af4 measurem5t (1 #ad-ae4 ,!rmomet]1 #ad-ag4 ,c5tigrade1 #ae4 ,fahr5heit1 #ae4 ,t9d] box1 #dg4 ,transmission1 ( light1 #ade-adg4 ( s\nd1 #bfg-bga4 ,tun+ =k1 #bff1 #bgc1 #bgh1 #bij4 ,turb9e1 /eam1 #ahc4 wat]1 #agh4 ,turp5t9e1 & grease1 #bbf4 by di/illation1 #ce4 ,unleav5$ bread1 #bcc4 ,vacuum1 s\nd 91 #bfh4 ,vapor1 9 atmosph]e1 #cf-ch4 ,vaporization1 heat (1 #cb4 ,v>ni%1 on c&ies1 #bec4 ,vegetable matt]1 & coal1 #cj4 & gas1 #cj4 & oil1 #cj4 ,ve9s1 =mation 9 rock1 #gb-gc4 ,velocity1 ( s\nd1 #bga-bgb4 ,v5tilation1 #ba-bd1 #ed4 ne$ (1 #ch4 ,vibration1 ( /r+s1 #bhf-bij4 sympa!tic1 #bgd-bgg4 ,viola1 #bie4 ,viol91 #bie4 ,violoncello1 #bie4 ,vocal cords1 #cjj4 ,voice1 #cjj4 ,volt1 #cdd4 ,voltage1 #cde4 ,voltaic cell1 #cjf-cjh1 #caj4 ,voltmet]1 #cdd4 ,volume1 ( a /ream1 #agi-ahj4 relation ( pressure ( a gas1 #ie-if4 ,wa%+ p[d]s1 #bbd-bbf4 soda1 #bbi4 ,wat]1 action 9 nature1 #gj-gd4 am\nt us$ daily p] p]son1 #aha4 & hydrog51 #gi4 & oxyg51 #gi1 #hj4 z solv5t1 #gj-ga4 boil+1 #gg4 boil+ po9t1 #ae4 composition1 #gi-hj4 cond5sation1 #cc4 dams & res]voirs1 #bad-baf4 d5sity1 #aa4 di/ill$1 #cd1 #gg4 dr9k+1 #ge-gg1 #aie-bja4 electrolysis1 #gi-hj4 evaporation1 #cc-cd4 expansion1 #i-aj1 #da-db4 filtration1 #gg4 freez+1 #dj-da4 h>d1 #bbe4 heat ( fusion1 #dj4 impurities1 #gf-gg4 9 atmosph]e1 #cf-ch4 9 food1 #ge4 9 human body1 #ge4 9 vegetables1 #ge4 influ5ce on climate1 #bi1 #dj4 irrigation1 #aic-aid4 m9]als 91 #gj-ga4 ocean1 #bfe4 p[]1 #agf-ahj4 precipitates1 #gb1 #gc4 pressure1 #bjh-baa1 #bad-baf4 purification1 #gg4 ra91 #bbe4 runn+1 value (1 #agh-ahj4 s\rce (1 #gh4 /eam1 #cb4 waves1 #ade-adg4 weight1 #bjh-bji1 #bae4 wells1 #aie-bja4 :eels1 #agf-ahj4 "w "u1 #bjc-bje4 ,wat] supply1 & =e/s1 #baf-bag4 co/1 #bab-bad4 ( city1 #bjf-bab1 #bag4 ,watt1 #cea4 ,waves1 heat1 #ade-adg4 light1 #ade-adg4 s\nd1 #bfh1 #bgb-bgd4 wat]1 #ade-adg4 ,wea!r1 bureau1 #hg-ia4 =eca/s1 #ch-ci1 #hf-hh4 relation ( wat] to1 #bi1 #dj4 ,wea!r maps1 #hi-ia4 ,w$ge1 & incl9$ plane1 #aff4 ,weight1 ( air1 #hf4 ( wat]1 #bjh-bji1 #bae4 ,weld+1 by electricity1 #cae4 ,wells1 #aie-bja4 drill$1 #aii4 driv51 #aif-aig4 ,:eel & axle1 #afi-aga4 cog:eels1 #agj4 w9dlass1 #afi4 ,:eelb>r[ z lev]1 #afj-afa4 ,:ite light1 nature (1 #ace4 ,w9d in/rum5ts1 #big-cja4 ,w9dlass1 #afi4 ,w9dmill1 #agd-age1 #ahj-ahb4 ,w9ds1 #bd4 ,w9e1 #bcb1 #bcd4 ,wood1 z s\rce ( *>coal1 #eh4 a%es 9 soap mak+1 #bbc4 9 pap] mak+1 #bai4 pres]vation1 #bec-bed4 ,wool1 blea*+1 #bda4 dye+1 #bde-bdg4 ,"w1 #aef-ahf4 & /eam1 #ahc-ahd4 & wat]1 #agf-ahj4 cons]vation1 #agd-age4 =mula1 #aeg4 ma*9es1 #aeg-age4 unit (1 #agb-agc4 wa/e1 #agc4 ,wov5 designs 9 clo?1 #bdi4 ,yea/1 #bcd-bcf4 wild1 #bce-bcf4 ,z9c1 9 galvaniz+ iron1 #di4 9 mak+ hydrog51 #hj4 9 voltaic cell1 #cjg-cjh4 ,,plant ,,life ,,& ,,plant ,,uses ,by ,,john ,,gaylord ,,c\lt]1 ,ph4 ,d4 #a4bj ,an elem5t>y textbook provid+ a f\ndation = ! /udy ( agriculture1 dome/ic sci5ce1 or college botany4 ,b x is m ?an a textbook on botany--x is a book ab\t ! fundam5tals ( plant life & ab\t ! relations betwe5 plants & man4 ,x pres5ts z fully z is desirable = requir$ c\rses 9 high s*ools ^? l>ge facts ab\t plants :i* =m ! pres5t basis ( ! sci5ce ( botany4 ,yet ! treatm5t has 9 view prep>ation = life 9 g5]al1 & n prep>ation = any p>ticul> k9d ( call+4 ,! subject is dealt ) f ! viewpo9t ( ! pupil r ?an f t ( ! tea*] or ! sci5ti/4 ,! /yle is simple1 cle>1 & conv]sational1 yet ! me?od is di/9ctly sci5tific1 & ! book has a cultural z well z a practical object4 ,! text has a unity ( organization4 ,s f> z practicable ! famili> always prec$es ! unfamili> 9 ! sequ5ce ( topics1 & ! facts are made to hang toge!r 9 ord] t ! pupil may see relation%ips4 ,su* topics z =e/ry1 plant bre$+1 we$s1 plant enemies & diseases1 plant culture1 decorative plants1 & economic bact]ia are discuss$ :]e mo/ p]t95t to ! g5]al !me r ?an 9 sep>ate *apt]s :i* de/roy ! cont9uity4 ,! que/ions & sugge/ions :i* foll[ ! *apt]s are ( two k9ds2 "s are design$ m]ely to s]ve z an aid 9 ! /udy ( ! text1 :ile o!rs sugge/ outside /udy & inquiry4 ,! classifi$ tables ( t]ms :i* prec$e ! index are int5d$ to s]ve ! /ud5t 9 review1 & to be a g5]al guide to ! relative values ( ! facts pres5t$4 ,m ?an #bjj attractive illu/rations1 _m ( !m orig9al1 are includ$ 9 ! book4 ,,am]ican ,,book ,,company ,a ,,new ,,a/ronomy1 #a4cj ,by ,,david ,,todd1 ,m4 ,a41 ,ph4 ,d41 ,pr(essor ( ,a/ronomy & ,navigation & ,director ( ! ,obs]vatory1 ,amh]/ ,college4 ,a/ronomy is "h pres5t$ z preem95tly a sci5ce ( obs]vation4 ,m ( ?9k+ ?an ( memoriz+ is requir$ 9 its /udy1 & great] emphasis is laid on ! physical ?an on ! ma!matical aspects ( ! sci5ce4 ,z 9 physics & *emi/ry1 ! fundam5tal pr9ciples are connect$ ) tangible1 famili> objects1 & ! /ud5t is %[n h[ he c readily make app>atus to illu/rate !m4 ,9 ord] to secure ! fulle/ educational value1 a/ronomy is reg>d$ z an int]-relat$ s]ies ( philosophic pr9ciples4 99 99 99 99 99 ,,ma!matical ,,geography1 #a4jj ,by ,,willis ,e4 ,,johnson1 ,ph4 ,d41 ,vice-,presid5t & ,pr(essor ( ,geography & ,social ,sci5ces1 ,nor!rn ,normal & ,indu/rial ,s*ool1 ,ab]de51 ,s\? ,dakota4 ,?is "w expla9s ) great cle>ness & ?or\ghness t portion ( ! subject :i* n only is mo/ difficult to und]/&1 b also und]lies & gives mean+ to all geographical k4 ,a va/ numb] ( facts :i* are mu* inquir$ ab\t1 b little kn[n1 are tak5 up & expla9$4 ,simple =mulas are giv5 s t a /ud5t unacqua9t$ ) geometry or trigonometry may calculate ! heights & di/ances ( objects1 ! latitude & longitude ( a place1 ! am\nt any body is light5$ by ! c5trifugal =ce due to rotation1 ! deviation ( a plumb-l9e f a true v]tical1 etc4 ,,am]ican ,,book ,,company ,,elem5ts ,,( ,,geology ,by ,,eliot ,,blackweld]1 ,associate ,pr(essor ( ,geology1 ,univ]sity ( ,wiscons91 & ,,h>lan ,h4 ,,b>r[s1 ,associate ,pr(essor ( ,g5]al ,geology & ,geography1 ,univ]sity ( ,*icago4 #a4dj ,an introductory c\rse 9 geology1 complete en\gh = college classes1 yet simple en\gh = high s*ool pupils4 ,! text is explanatory1 seldom m]ely descriptive1 & ! /ud5t ga9s a k n only ( ! sali5t facts 9 ! hi/ory ( ! e>?1 b also ( ! me?ods by :i* ^? facts h be5 det]m9$4 ,! /yle is simple & direct4 ,few te*nical t]ms are us$4 ,! book is exce$+ly tea*able4 ,! volume is divid$ into two p>ts1 physical geology & hi/orical geology4 ,x diff]s m or less f its pr$ecessors 9 ! emphasis on diff]5t topics & 9 ! arrangem5t ( its mat]ial4 ,factors ( m9or importance 9 ! developm5t ( ! e>?1 su* z e>?quakes1 volcanoes1 & geys]s1 are treat$ mu* m briefly ?an is cu/om>y4 ,?is has giv5 space = ! ext5d$ discussion ( matt]s ( great] significance4 ,= ! fir/ "t an adequate discussion ( ! lead+ mod]n conceptions conc]n+ ! orig9 & e>ly developm5t ( ! e>? is pres5t$ 9 an elem5t>y textbook4 ,! illu/rations & maps1 :i* are unusually num]\s1 really illu/rate ! text & are ref]r$ to def9itely 9 ! discussion4 ,!y are admirably adapt$ to s]ve z ! basis = classroom discussion & quizzes1 & z su* con/itute "o ( ! mo/ important features ( ! book4 ,! que/ions at ! end ( ! *apt]s are di/9ctive 9 t ! answ]s are 9 g5]al n to be f\nd 9 ! text4 ,!y may1 h[ev]1 be reason$ out by ! /ud5t1 provid$ he has read ! text ) und]/&+4 ,,am]ican ,,book ,,company ,,ess5tials ,,( ,,biology ,by ,,george ,,william ,,hunt]1 ,a4 ,m41 ,head ( ,dep>tm5t ( ,biology1 ,de ,witt ,cl9ton ,high ,s*ool1 ,new ,york ,city4 #a4be ,?is new fir/-ye> c\rse treats ! subject ( biology z a :ole1 & meets ! requirem5ts ( ! lead+ colleges & associations ( sci5ce tea*]s4 ,in/ead ( discuss+ plants1 animals1 & man z sep>ate =ms ( liv+ organisms1 x treats ( fife 9 a compreh5sive mann]1 & p>ticul>ly 9 its relations to ! progress ( humanity4 ,ea* ma9 topic is introduc$ by a problem1 :i* ! pupil is to solve by actual laboratory "w4 ,! text t foll[s expla9s & illu/rates ! mean+ ( ea* problem4 ,! "w ?r\gh\t aims to h a human int]e/ & a practical value1 & to provide ! simple/ & mo/ easily compreh5d$ me?od ( demon/ration4 ,at ! end ( ea* *apt] are li/s ( ref]5ces to bo? elem5t>y & advanc$ books = collat]al read+4 99 99 99 99 99 ,,%>pe',s ,,laboratory ,,manual ,,9 ,,biology #j4ge ,9 ?is ,manual ! #ef important problems ( ,hunt]'s ,ess5tials ( ,biology are solv$2 t is1 ! pr9ciples ( biology are develop$ f ! laboratory /&po9t4 ,x is a tea*]'s detail$ directions put into pr9t4 ,x /ates ! problems1 & !n tells :at mat]ials & app>atus are necess>y & h[ !y are to be us$1 h[ to avoid mi/akes1 & h[ to get at ! facts :5 !y are f\nd4 ,foll[+ ea* problem & its solution is a full li/ ( ref]5ces to o!r books4 ,,am]ican ,,book ,,company ,,ess5tials ,,( ,,physics ,by ,,george ,a4 ,,hoadley1 ,c4,e41 ,sc4 ,d41 ,pr(essor ( ,physics1 ,sw>?more ,college4 #a4be ,?is is ! au?or's popul> & successful ,elem5ts ( ,physics enri*$ & br\ght up to date4 ,despite ! _m *anges & modifications made 9 ?is new edition1 x reta9s ! qualities :i* h secur$ s great a success = ! previ\s book4 ,x tells only :at ev]yone %\ld "k1 & x does ?is 9 a /raight=w>d1 concise1 & int]e/+ mann]4 ,x takes into consid]ation ! "* ( high s*ool ne$s & conditions1 &1 ?r\gh\t1 lays p>ticul> emphasis ^u ! intimate relation betwe5 physics & ev]yday life4 ,:ile ! subject matt]1 z a :ole1 is un*ang$1 ! ord] ( topics 9 _m cases has be5 alt]$ to adapt ! developm5t ( ! subject to ! habits ( ?\ght ( high s*ool pupils4 ,in/ead ( beg9n+ ! treatm5t ( a subject ) ! def9ition & proce$+ to a discussion ( ! sub-topics1 ! au?or />ts ) a discussion ( well-kn[n ph5om5a & leads up to ! def9ition ( ! subject discuss$4 ,! text1 :]ev] possible1 has be5 simplifi$1 m ?an fifty topics hav+ be5 amplifi$1 exp&$1 or reword$4 ,m famili> illu/rations ( ! topics treat$ are giv51 & ! demon/rations ( _m ( ! exp]im5ts are simplifi$ by ! use ( mat]ials t are readily obta9able 9 ! classroom4 ,!re h be5 add$ a numb] ( new topics1 mo/ly 9 connection ) ! rec5t advances 9 appli$ sci5ce4 ,! numb] bo? ( que/ions & problems has be5 greatly increas$ & ! data 9 ^! all relate to actual1 practical1 physical ph5om5a4 ,m ?an "o-fif? ( ! illu/rations 9 ! book are new1 _m ( ! pictures ( app>atus hav+ be5 r$rawn to %[ mod]n =ms4 ,,am]ican ,,book ,,company