,?is e,book includes #e pap]s or spee*es
 by ,james ,cl]k ,maxwell4  ,! cont5ts  
are3     ,=am5 ,c5trale    ,!ory (      
,comp\nd ,col\rs    ,po9sot's ,!ory     
,address to ! ,ma!matical               
,introductory ,lecture     ,on !        
,unequal ,s5sibility ( ! ,=am5 ,c5trale 
to ,light ( diff]5t ,col\rs4  ,james    
,cl]k ,maxwell   ,f ! ,report ( !       
,briti% ,association1 #ahef4   ,:5      
obs]v+ ! spectrum =m$ by look+ at a long
 ve rtical slit ?r\gh a simple prism1 ,i
 notic$ an elongat$ d>k spot runn+ up & 
d[n 9 ! blue1 & foll[+ ! motion ( ! eye 
z x mov$ up & d[n ! spectrum1 b refus+  
to pass out ( ! blue into ! o!r col\rs4 
,x 0 pla9 t ! spot belong$ bo? to ! eye 
& to ! blue "p ( ! spectrum4  ,! result 
to :i* ,i h come is1 t ! appe>ance is   
due to ! yell[ spot on ! ret9a1 commonly
 call$ ! ,=am5 ,c5trale ( ,soemm]+4  ,! 
mo/ conv5i5t me?od ( obs]v+ ! spot is by
 pres5t+ to ! eye 9 n too rapid         
succession1 blue & yell[ glasses1 or1   
/ill bett]1 all[+ blue & yell[ pap]s to 

revolve sl[ly be=e ! eye4  ,9 ?is way ! 
spot is se5 9 ! blue4  ,x fades rapidly1
 b is r5ew$ e "t ! yell[ comes 9 to     
relieve ! effect ( ! blue4  ,by us+ a   
,nicol's prism along ) ?is app>atus1 !  
bru%es ( ,haid+] are well se5 9         
connexion ) ! spot1 & ! fact ( ! bru%es 
be+ ! spot analys$ by pol>iz$ light     
becomes evid5t4  ,if we look /eadily at 
an object beh9d a s]ies ( bright b>s :i*
 move 9 front ( x1 we %all see a curi\s 
b5d+ ( ! b>s z !y come up to ! place ( !
 yell[ spot4  ,! "p :i* comes ov] ! spot
 seems to />t 9 advance ( ! re/ ( ! b>1 
& ?is w\ld seem to indicate a great]    
rapidity ( s5sation at ! yell[ spot ?an 
9 ! surr\nd+ ret9a4  ,b ,i f9d !        
exp]im5t difficult1 & ,i hope = bett]   
results f m accurate obs]v]s4     ,on ! 
,!ory ( ,comp\nd ,col\rs ) ref]5ce to   
,mixtures ( ,blue & ,yell[ ,light4      
,james ,cl]k ,maxwell   ,f ! ,report ( !
 ,briti% ,association1 #ahef4   ,:5 we  
mix toge!r blue & yell[ pa9t1 we obta9  
gre5 pa9t4 ,?is fact is well kn[n to all

 :o h h&l$ col\rs2 & x is univ]sally    
admitt$ t blue & yell[ make gre54  ,r$1 
yell[1 & blue1 be+ ! prim>y col\rs among
 pa9t]s1 gre5 is reg>d$ z a second>y    
col\r1 aris+ f ! mixture ( blue & yell[4
 ,newton1 h[ev]1 f\nd t ! gre5 ( !      
spectrum 0 n ! same ?+ z ! mixture ( two
 col\rs ( ! spectrum1 = su* a mixture   
c\ld be sep>at$ by ! prism1 :ile ! gre5 
( ! spectrum resi/$ fur!r decomposition4
  ,b /ill x 0 believ$ t yell[ & blue    
w\ld make a gre51 ?\gh n t ( ! spectrum4
  ,z f> z ,i am aw>e1 ! fir/ exp]im5t on
 ! subject is t ( ,m4 ,plateau1 :o1 be=e
 #ahai1 made a disc ) alt]nate sectors (
 prussian blue & gamboge1 & obs]v$ t1 :5
 sp9n+1 ! resultant t9t 0 n gre51 b a   
neutral gray1 incl9+ sometimes to yell[ 
or blue1 b nev] to gre54 ,pr(4 ,j4 ,d4  
,=bes ( ,ed9burgh made simil> exp]im5ts 
9 #ahdi1 ) ! same result4  ,pr(4        
,helmholtz ( ,konigsb]g1 to :om we owe !
 mo/ complete inve/igation on visible   
col\r1 has giv5 ! true explanation ( ?is
 ph5om5on4  ,! result ( mix+ two col\r$ 

p[d]s is n by any means ! same z mix+ ! 
beams ( light :i* fl[ f ea* sep>ately4  
,9 ! latt] case we receive all ! light  
:i* comes ei!r f ! "o p[d] or ! o!r4  ,9
 ! =m]1 mu* ( ! light com+ f "o p[d]    
falls on p>ticles ( ! o!r1 & we receive 
only t portion :i* has escap$ absorption
 by "o or o!r4  ,?us ! light com+ f a   
mixture ( blue & yell[ p[d]1 consi/s    
p>tly ( light com+ directly f blue      
p>ticles or yell[ p>ticles1 & p>tly (   
light act$ on by bo? blue & yell[       
p>ticles4  ,?is latt] light is gre51    
s9ce ! blue /ops ! r$1 yell[1 & orange1 
& ! yell[ /ops ! blue & violet4  ,i h   
made exp]im5ts on ! mixture ( blue &    
yell[ light--by rapid rotation1 by      
comb9$ reflexion & transmission1 by     
view+ !m out ( focus1 9 /ripes1 at a    
great di/ance1 by ?r[+ ! col\rs ( !     
spectrum on a scre51 & by receiv+ !m    
into ! eye directly2 & ,i h arrang$ a   
portable app>atus by :i* any "o may see 
! result ( ?is or any o!r mixture ( !   
col\rs ( ! spectrum4  ,9 all ^! cases   

blue & yell[ d n make gre54  ,i h also  
made exp]im5ts on ! mixture ( col\r$    
p[d]s4  ,^? :i* ,i us$ pr9cipally 7     
m9]al blue 7f copp]7 & *rome-yell[4     
,o!r blue & yell[ pigm5ts gave curi\s   
results1 b x 0 m difficult to make !    
mixtures1 & ! gre5s 7 less uni=m 9 t9t4 
,! mixtures ( ^! col\rs 7 made by       
weight1 & 7 pa9t$ on discs ( pap]1 :i* 7
 aft]w>ds treat$ 9 ! mann] describ$ 9 my
 pap] ,on ,col\r z p]ceiv$ by ! ,eye1 9 
! ,transactions ( ! ,royal ,society (   
,ed9burgh1 ,vol4 ,,xxi4 ,"p #b4  ,!     
visible effect ( ! col\r is e/imat$ 9   
t]ms ( ! /&>d-col\r$ pap]s3--v]milion   
7,v71 ultram>9e 7,u71 & em]ald-gre5     
7,e74  ,! accuracy ( ! results1 & _!    
significance1 c be be/ und]/ood by      
ref]r+ to ! pap] be=e m5tion$4  ,i %all 
d5ote m9]al blue by ,b1 & *rome-yell[ by
 ,y2 & ,b#c ,y#e means a mixture ( ?ree 
p>ts blue & five p>ts yell[4            
,giv5 ,col\r4     ,/&>d ,col\rs4        
,coeffici5t                             
,v4    ,u4    ,e4           (           

brightness4           ,b#h    1 #ajj    
#b    #cf     #g   444444444444   #de   
,b#g  ,y#a1 #ajj     #a    #ah    #ag   
444444444444   #cg              ,b#f    
,y#b1 #ajj     #d    #aa    #cd         
444444444444   #di              ,b#e    
,y#c1 #ajj     #i     #e    #dj         
444444444444   #ed              ,b#d    
,y#d1 #ajj    #ae     #a    #dj         
444444444444   #ef              ,b#c    
,y#e1 #ajj    #bb   - #b    #dd         
444444444444   #fd              ,b#b    
,y#f1 #ajj    #ce   -#aj    #ea         
444444444444   #gf              ,b#a    
,y#g1 #ajj    #fd   -#ai    #fd         
444444444444  #aji                      
,y#h1 #ajj   #ahj   -#bg   #abd         
444444444444  #bgg  ,! columns ,v1 ,u1  
,e give ! proportions ( ! /&>d col\rs   
:i* are equival5t to #ajj ( ! giv5      
col\r2 & ! sum ( ,v1 ,u1 ,e gives a     
coeffici5t1 :i* gives a g5]al idea ( !  
brightness4  ,x w be se5 t ! fir/       
admixture ( yell[ dim9i%es ! brightness 
( ! blue4  ,! negative values ( ,u      

indicate t a mixture ( ,v1 ,u1 & ,e _c  
be made equival5t to ! giv5 col\r4 ,!   
exp]im5ts f :i* ^! results 7 tak5 _h !  
negative values transf]r$ to ! o!r side 
( ! equation4  ,!y 7 all made by means (
 ! col\r-top1 & 7 v]ifi$ by repetition  
at diff]5t times4  ,x may be necess>y to
 rem>k1 9 conclusion1 ) ref]5ce to !    
mode ( regi/]+ visible col\rs 9 t]ms (  
?ree arbitr>y /&>d col\rs1 t x proce$s  
^u t !ory ( ?ree prim>y elem5ts 9 !     
s5sation ( col\r1 :i* treats !          
inve/igation ( ! laws ( visible col\r z 
a bran* ( human physiology1 incapable ( 
be+ d$uc$ f ! laws ( light itself1 z set
 =? 9 physical optics4  ,x takes        
advantage ( ! me?ods ( optics to /udy   
vision itself2 & its appeal is n to     
physical pr9ciples1 b to our            
consci\sness ( our own s5sations4       
,on an ,in/rum5t to illu/rate ,po9sot's 
,!ory ( ,rotation4  ,james ,cl]k        
,maxwell   ,f ! ,report ( ! ,briti%     
,association1 #ahef4   ,9 /udy+ !       
rotation ( a solid body accord+ to      

,po9sot's me?od1 we h to consid] !      
successive positions ( ! in/antane\s    
axis ( rotation ) ref]5ce bo? to        
directions fix$ 9 space & axes assum$ 9 
! mov+ body4  ,! pa?s trac$ out by !    
pole ( ?is axis on ! inv>iable plane &  
on ! c5tral ellipsoid =m int]e/+        
subjects ( ma!matical inve/igation4 ,b  
:5 we attempt to foll[ ) our eye !      
motion ( a rotat+ body1 we f9d x        
difficult to det]m9e ?r\gh :at po9t ( ! 
body ! in/antane\s axis passes at any   
"t1--& to det]m9e its pa? mu/ be /ill m 
difficult4  ,i h endeav\r$ to r5d]      
visible ! pa? ( ! in/antane\s axis1 & to
 v>y ! circum/ances ( motion1 by means (
 a top ( ! same k9d z t us$ by ,mr      
,elliot1 to illu/rate precession994  ,! 
body ( ! in/rum5t is a holl[ cone (     
wood1 ris+ f a r+1 #g in*es 9 diamet] & 
#a in* ?ick4  ,an iron axis1 #h in*es   
long1 screws into ! v]tex ( ! cone4  ,! 
l[] extremity has a po9t ( h>d /eel1 :i*
 re/s 9 an agate cup1 & =ms ! support ( 
! in/rum5t4  ,an iron nut1 ?ree ounces 9

 weight1 is made to screw on ! axis1 &  
to be fix$ at any po9t2 & 9 ! wood5 r+  
are screw$ f\r bolts1 ( ?ree ounces1    
work+ horizontally1 & f\r bolts1 ( "o   
ounce1 work+ v]tically4  ,on ! upp] "p (
 ! axis is plac$ a disc ( c>d1 on :i*   
are drawn f\r conc5tric r+s4  ,ea* r+ is
 divid$ into f\r quadrants1 :i* are     
col\r$ r$1 yell[1 gre51 & blue4  ,!     
spaces betwe5 ! r+s are :ite4 ,:5 ! top 
is 9 motion1 x is easy to see 9 :i*     
quadrant ! in/antane\s axis is at any   
mom5t & ! di/ance betwe5 x & ! axis ( ! 
in/rum5t2 & we obs]ve1--#a/4 ,t !       
in/antane\s axis travels 9 a clos$      
curve1 & returns to its orig9al position
 9 ! body4  #bndly4 ,t by work+ !       
v]tical bolts1 we c make ! axis ( !     
in/rum5t ! c5tre ( ?is clos$ curve4  ,x 
w !n be "o ( ! pr9cipal axes ( in]tia4  
#crdly4 ,t1 by work+ ! nut on ! axis1 we
 c make ! ord] ( col\rs ei!r r$1 yell[1 
gre51 blue1 or ! rev]se4  ,:5 ! ord] (  
col\rs is 9 ! same direction z !        
rotation1 x indicates t ! axis ( !      

in/rum5t is t ( greate/ mom5t ( in]tia4 
#d?ly4 ,t if we screw ! two pairs (     
opposite horizontal bolts to diff]5t    
di/ances f ! axis1 ! pa? ( ! in/antane\s
 pole w no long] be equidi/ant f ! axis1
 b w describe an ellipse1 ^: long] axis 
is 9 ! direction ( ! mean axis ( !      
in/rum5t4  #e?ly4 ,t if we n[ make "o ( 
! two horizontal axes less & ! o!r      
great] ?an ! v]tical axis1 ! in/antane\s
 pole w sep>ate f ! axis ( ! in/rum5t1 &
 ! axis w incl9e m & m till ! sp9n+ c no
 long] g on1 on acc\nt ( ! obliquity4   
,x is easy to see t1 by att5d+ to ! laws
 ( motion1 we may produce any ( ! above 
effects at pleasure1 & illu/rate _m     
diff]5t propositions by means ( ! same  
in/rum5t4  99 ,transactions ( ! ,royal  
,scotti% ,society ( ,arts1 #ahee4       
,address to ! ,ma!matical & ,physical   
,sections ( ! ,briti% ,association4     
,james ,cl]k ,maxwell   ,f ! ,briti%    
,association ,report1 ,vol4 ,,xl4       
,liv]pool1 ,septemb] #ae1 #ahgj4   ,at  
sev]al ( ! rec5t ,meet+s ( ! ,briti%    

,association ! v>i$ & important bus9ess 
( ! ,ma!matical & ,physical ,section has
 be5 introduc$ by an ,address1 ! subject
 ( :i* has be5 left to ! selection ( !  
,presid5t = ! "t be+4  ,! p]plex+ duty (
 *oos+ a subject has n1 h[ev]1 fall5 to 
me4  ,pr(essor ,sylve/]1 ! ,presid5t (  
,section ,a at ! ,exet] ,meet+1 gave u a
 noble v9dication ( pure ma!matics by   
lay+ b>e1 z x 71 ! v work+ ( !          
ma!matical m9d1 & sett+ be=e u1 n !     
array ( symbols & brackets :i* =m !     
arm\ry ( ! ma!matician1 or ! dry results
 :i* are only ! monum5ts ( 8 conque/s1 b
 ! ma!matician himself1 ) all 8 human   
faculties direct$ by 8 pr(essional      
sagacity to ! pursuit1 appreh5sion1 &   
exhibition ( t ideal h>mony :i* he feels
 to be ! root ( all k1 ! f\nta9 ( all   
pleasure1 & ! condition ( all action4   
,! ma!matician has1 above all ?+s1 an   
eye = symmetry2 & ,pr(essor ,sylve/] has
 n only recogniz$ ! symmetry =m$ by !   
comb9ation ( 8 own subject ) ^? ( ! =m] 
,presid5ts1 b has po9t$ out ! duties ( 8

 successor 9 ! foll[+ *>act]i/ic note3--
  ,mr ,spottiswoode fav\r$ ! ,section1 9
 8 op5+ ,address1 ) a comb9$ hi/ory ( ! 
progress ( ,ma!matics & ,physics2 ,dr4  
,tyndall's address 0 virtually on !     
limits ( ,physical ,philosophy2 ! "o "h 
9 pr9t1 says ,pr(4 ,sylve/]1 is an      
attempt$ fa9t adumbration ( ! nature (  
,ma!matical ,sci5ce 9 ! ab/ract4 ,:at is
 want+ 7l a f\r? sph]e re/+ on ?ree o!rs
 9 contact7 to build up ! ,ideal        
,pyramid is a disc\rse on ! ,relation ( 
! two bran*es 7,ma!matics & ,physics7   
to1 _! action & reaction ^u1 "o ano!r1 a
 magnific5t !me1 ) :i* x is to be hop$ t
 "s future ,presid5t ( ,section ,a w    
cr[n ! edifice & make ! ,tetralogy      
7symbolizable by ,a,a'1 ,a1 ,a'1 ,,aa'7 
complete4  ,! !me ?us di/9ctly laid d[n 
= 8 successor by our late ,presid5t is  
inde$ a magnific5t "o1 f> too magnific5t
 = any ef=ts ( m9e to realize4  ,i h    
endeav\r$ to foll[ ,mr ,spottiswoode1 z 
) f>-rea*+ vision he di/+ui%es ! sy/ems 
( sci5ce into :i* ph5om5a1 our k ( :i*  

is /ill 9 ! nebul\s /age1 are gr[+4  ,i 
h be5 c>ri$ by ! p5etrat+ insight &     
=cible expression ( ,dr ,tyndall into t 
sanctu>y ( m9ut5ess & ( p[] :]e         
molecules obey ! laws ( _! exi/5ce1 cla%
 toge!r 9 fi]ce collision1 or grapple 9 
yet m fi]ce embrace1 build+ up 9 secret 
! =ms ( visible ?+s4  ,i h be5 guid$ by 
,pr(4 ,sylve/] t[>ds ^? s]5e heights    
,:]e nev] creeps a cl\d1 or moves a w9d1
      ,nor ev] falls ! lea/ :ite /> (   
sn[1      ,nor ev] l[e/ roll ( ?und]    
moans1      ,nor s\nd ( human sorr[     
m\nts to m>      ,_! sacr$ ev]la/+ calm4
  ,b :o w lead me into t /ill m hidd5 & 
dimm] region :]e ,?\ght w$s ,fact1 :]e !
 m5tal op]ation ( ! ma!matician & !     
physical action ( ! molecules are se5 9 
_! true relation8  ,does n ! way to x   
pass ?r\gh ! v d5 ( ! metaphysician1    
/rew$ ) ! rema9s ( =m] explor]s1 &      
abhorr$ by e man ( sci5ce8  ,x w\ld     
inde$ be a foolh>dy adv5ture = me to    
take up ! valuable "t ( ! ,section by   
lead+ y into ^? speculations :i*        

require1 z we "k1 ?\s&s ( ye>s ev5 to   
%ape !mselves intelligibly4  ,b we are  
met z cultivators ( ma!matics & physics4
  ,9 our daily "w we are l$ up to       
que/ions ! same 9 k9d ) ^? (            
metaphysics2 & we approa* !m1 n tru/+ to
 ! native p5etrat+ p[] ( our own m9ds1 b
 tra9$ by a long-cont9u$ adju/m5t ( our 
modes ( ?\ght to ! facts ( ext]nal      
nature4  ,z ma!maticians1 we p]=m c]ta9 
m5tal op]ations on ! symbols ( numb] or 
( quantity1 &1 by proce$+ /ep by /ep f m
 simple to m complex op]ations1 we are  
enabl$ to express ! same ?+ 9 _m diff]5t
 =ms4  ,! equival5ce ( ^! diff]5t =ms1  
?\gh a necess>y consequ5ce ( self-evid5t
 axioms1 is n always1 to our m9ds1      
self-evid5t2 b ! ma!matician1 :o by long
 practice has acquir$ a famili>ity ) _m 
( ^! =ms1 & has become exp]t 9 !        
processes :i* lead f "o to ano!r1 c (t5 
trans=m a p]plex+ expression into ano!r 
:i* expla9s its mean+ 9 m intelligible  
language4  ,z /ud5ts ( ,physics we      
obs]ve ph5om5a "u v>i$ circum/ances1 &  

endeav\r to d$uce ! laws ( _! relations4
 ,e natural ph5om5on is1 to our m9ds1 ! 
result ( an inf9itely complex sy/em (   
conditions4  ,:at we set ourselves to d 
is to unravel ^! conditions1 & by view+ 
! ph5om5on 9 a way :i* is 9 itself      
p>tial & imp]fect1 to piece out its     
features "o by "o1 beg9n+ ) t :i* /rikes
 u fir/1 & ?us gradually le>n+ h[ to    
look at ! :ole ph5om5on s z to obta9 a  
cont9ually great] degree ( cle>ness &   
di/9ctness4  ,9 ?is process1 ! feature  
:i* pres5ts itself mo/ =cibly to !      
untra9$ inquir] may n be t :i* is       
consid]$ mo/ fundam5tal by ! exp]i5c$   
man ( sci5ce2 = ! success ( any physical
 inve/igation dep5ds on ! judici\s      
selection ( :at is to be obs]v$ z (     
prim>y importance1 comb9$ ) a volunt>y  
ab/raction ( ! m9d f ^? features :i*1   
h[ev] attractive !y appe>1 we are n yet 
suffici5tly advanc$ 9 sci5ce to         
inve/igate ) pr(it4  ,intellectual      
processes ( ?is k9d h be5 go+ on s9ce ! 
fir/ =mation ( language1 & are go+ on   

/ill4  ,no d\bt ! feature :i* /rikes u  
fir/ & mo/ =cibly 9 any ph5om5on1 is !  
pleasure or ! pa9 :i* accompanies x1 & !
 agreeable or disagreeable results :i*  
foll[ aft] x4  ,a !ory ( nature f ?is   
po9t ( view is embodi$ 9 _m ( our words 
& phrases1 & is by no means ext9ct ev5 9
 our delib]ate op9ions4  ,x 0 a great   
/ep 9 sci5ce :5 m5 became conv9c$ t1 9  
ord] to und]/& ! nature ( ?+s1 !y mu/   
beg9 by ask+1 n :e!r a ?+ is good or    
bad1 noxi\s or b5eficial1 b ( :at k9d is
 x8 & h[ mu* is !re ( x8  ,quality &    
,quantity 7 !n fir/ recogniz$ z ! prim>y
 features to be obs]v$ 9 sci5tific      
inquiry4  ,z sci5ce has be5 develop$1 ! 
doma9 ( quantity has ev]y:]e encroa*$ on
 t ( quality1 till ! process ( sci5tific
 inquiry seems to h become simply !     
measurem5t & regi/ration ( quantities1  
comb9$ ) a ma!matical discussion ( !    
numb]s ?us obta9$4  ,x is ?is sci5tific 
me?od ( direct+ our att5tion to ^?      
features ( ph5om5a :i* may be reg>d$ z  
quantities :i* br+s physical rese>* "u !

 influ5ce ( ma!matical reason+4  ,9 ! "w
 ( ! ,section we %all h abundant        
examples ( ! successful application (   
?is me?od to ! mo/ rec5t conque/s (     
sci5ce2 b ,i wi% at pres5t to direct y\r
 att5tion to "s ( ! reciprocal effects (
 ! progress ( sci5ce on ^? elem5t>y     
conceptions :i* are sometimes ?\ght to  
be beyond ! rea* ( *ange4  ,if ! skill (
 ! ma!matician has enabl$ ! exp]im5tali/
 to see t ! quantities :i* he has       
measur$ are connect$ by necess>y        
relations1 ! discov]ies ( physics h     
reveal$ to ! ma!matician new =ms (      
quantities :i* he c\ld nev] h imag9$ =  
himself4  ,( ! me?ods by :i* !          
ma!matician may make 8 lab\rs mo/ useful
 to ! /ud5t ( nature1 t :i* ,i ?9k is at
 pres5t mo/ important is ! sy/ematic    
classification ( quantities4  ,!        
quantities :i* we /udy 9 ma!matics &    
physics may be classifi$ 9 two diff]5t  
ways4  ,! /ud5t :o wi%es to ma/] any    
p>ticul> sci5ce mu/ make himself famili>
 ) ! v>i\s k9ds ( quantities :i* belong 

to t sci5ce4  ,:5 he und]/&s all !      
relations betwe5 ^! quantities1 he      
reg>ds !m z =m+ a connect$ sy/em1 & he  
classes ! :ole sy/em ( quantities toge!r
 z belong+ to t p>ticul> sci5ce4  ,?is  
classification is ! mo/ natural f a     
physical po9t ( view1 & x is g5]ally !  
fir/ 9 ord] ( "t4  ,b :5 ! /ud5t has    
become acqua9t$ ) sev]al diff]5t        
sci5ces1 he f9ds t ! ma!matical         
processes & tra9s ( reason+ 9 "o sci5ce 
resemble ^? 9 ano!r s mu* t 8 k ( ! "o  
sci5ce may be made a mo/ useful help 9 !
 /udy ( ! o!r4  ,:5 he exam9es into !   
reason ( ?is1 he f9ds t 9 ! two sci5ces 
he has be5 deal+ ) sy/ems ( quantities1 
9 :i* ! ma!matical =ms ( ! relations ( !
 quantities are ! same 9 bo? sy/ems1    
?\gh ! physical nature ( ! quantities   
may be utt]ly diff]5t4  ,he is ?us l$ to
 recognize a classification ( quantities
 on a new pr9ciple1 accord+ to :i* !    
physical nature ( ! quantity is         
subord9at$ to its ma!matical =m4  ,?is  
is ! po9t ( view :i* is *>act]i/ic ( !  

ma!matician2 b x /&s second to !        
physical aspect 9 ord] ( "t1 because !  
human m9d1 9 ord] to conceive ( diff]5t 
k9ds ( quantities1 mu/ h !m pres5t$ to x
 by nature4  ,i d n "h ref] to ! fact t 
all quantities1 z su*1 are subject to ! 
rules ( ari?metic & algebra1 & are !re=e
 capable ( be+ submitt$ to ^? dry       
calculations :i* repres5t1 to s _m m9ds1
 _! only idea ( ma!matics4  ,! human m9d
 is seldom satisfi$1 & is c]ta9ly nev]  
ex]cis+ its highe/ functions1 :5 x is   
do+ ! "w ( a calculat+ ma*9e4  ,:at !   
man ( sci5ce1 :e!r he is a ma!matician  
or a physical inquir]1 aims at is1 to   
acquire & develope cle> ideas ( ! ?+s he
 deals )4  ,= ?is purpose he is will+ to
 ent] on long calculations1 & to be = a 
season a calculat+ ma*9e1 if he c only  
at la/ make 8 ideas cle>]4  ,b if he    
f9ds t cle> ideas are n to be obta9$ by 
means ( processes ! /eps ( :i* he is    
sure to =get be=e he has rea*$ !        
conclusion1 x is mu* bett] t he %\ld    
turn to ano!r me?od1 & try to und]/& !  

subject by means ( well-*os5            
illu/rations d]iv$ f subjects ) :i* he  
is m famili>4  ,we all "k h[ mu* m      
popul> ! illu/rative me?od ( exposition 
is f\nd1 ?an t 9 :i* b>e processes (    
reason+ & calculation =m ! pr9cipal     
subject ( disc\rse4  ,n[ a truly        
sci5tific illu/ration is a me?od to     
enable ! m9d to grasp "s conception or  
law 9 "o bran* ( sci5ce1 by plac+ be=e x
 a conception or a law 9 a diff]5t bran*
 ( sci5ce1 & direct+ ! m9d to lay hold (
 t ma!matical =m :i* is common to !     
correspond+ ideas 9 ! two sci5ces1 leav+
 out ( acc\nt = ! pres5t ! diff]5ce     
betwe5 ! physical nature ( ! real       
ph5om5a4  ,! correctness ( su* an       
illu/ration dep5ds on :e!r ! two sy/ems 
( ideas :i* are comp>$ toge!r are really
 analog\s 9 =m1 or :e!r1 9 o!r words1 ! 
correspond+ physical quantities really  
belong to ! same ma!matical class4  ,:5 
?is condition is fulfill$1 ! illu/ration
 is n only conv5i5t = tea*+ sci5ce 9 a  
pleasant & easy mann]1 b ! recognition (

 ! =mal analogy betwe5 ! two sy/ems (   
ideas leads to a k ( bo?1 m pr(\nd ?an  
c\ld be obta9$ by /udy+ ea* sy/em       
sep>ately4  ,!re are m5 :o1 :5 any      
relation or law1 h[ev] complex1 is put  
be=e !m 9 a symbolical =m1 c grasp its  
full mean+ z a relation among ab/ract   
quantities4  ,su* m5 sometimes treat )  
indiff]5ce ! fur!r /atem5t t quantities 
actually exi/ 9 nature :i* fulfil ?is   
relation4  ,! m5tal image ( ! concrete  
reality seems r to di/urb ?an to assi/  
_! contemplations4 ,b ! great majority (
 mank9d are utt]ly unable1 )\t long     
tra9+1 to reta9 9 _! m9ds ! unembodi$   
symbols ( ! pure ma!matician1 s t1 if   
sci5ce is ev] to become popul>1 & yet   
rema9 sci5tific1 x mu/ be by a pr(\nd   
/udy & a copi\s application ( ^?        
pr9ciples ( ! ma!matical classification 
( quantities :i*1 z we h se51 lie at !  
root ( e truly sci5tific illu/ration4   
,!re are1 z ,i h said1 "s m9ds :i* c g  
on contemplat+ ) satisfaction pure      
quantities pres5t$ to ! eye by symbols1 

& to ! m9d 9 a =m :i* none b            
ma!maticians c conceive4  ,!re are o!rs 
:o feel m enjoym5t 9 foll[+ geometrical 
=ms1 :i* !y draw on pap]1 or build up 9 
! empty space be=e !m4  ,o!rs1 aga91 are
 n cont5t unless !y c project _! :ole   
physical en]gies into ! sc5e :i* !y     
conjure up4  ,!y le>n at :at a rate !   
planets ru% ?r\gh space1 & !y exp]i5ce a
 delightful feel+ ( exhil>ation4  ,!y   
calculate ! =ces ) :i* ! heav5ly bodies 
pull at "o ano!r1 & !y feel _! own      
muscles /ra9+ ) ! ef=t4  ,to su* m5     
mom5tum1 en]gy1 mass are n m]e ab/ract  
expressions ( ! results ( sci5tific     
inquiry4  ,!y are words ( p[]1 :i* /ir  
_! s\ls l ! memories ( *ildhood4  ,= !  
sake ( p]sons ( ^! diff]5t types1       
sci5tific tru? %\ld be pres5t$ 9 diff]5t
 =ms1 & %\ld be reg>d$ z equally        
sci5tific :e!r x appe>s 9 ! robu/ =m & !
 vivid col\r+ ( a physical illu/ration1 
or 9 ! t5uity & pal5ess ( a symbolical  
expression4  ,"t w\ld fail me if ,i 7 to
 attempt to illu/rate by examples !     

sci5tific value ( ! classification (    
quantities4  ,i %all only m5tion ! "n ( 
t important class ( magnitudes hav+     
direction 9 space :i* ,hamilton has     
call$ vectors1 & :i* =m ! subject-matt] 
( ! ,calculus ( ,quat]nions1 a bran* (  
ma!matics :i*1 :5 x %all h be5 ?or\ghly 
und]/ood by m5 ( ! illu/rative type1 &  
clo!d by !m ) physical imag]y1 w become1
 p]haps "u "s new "n1 a mo/ p[]ful me?od
 ( communicat+ truly sci5tific k to     
p]sons app>5tly devoid ( ! calculat+ _s4
  ,! mutual action & reaction betwe5 !  
diff]5t dep>tm5ts ( human ?\ght is s    
int]e/+ to ! /ud5t ( sci5tific progress1
 t1 at ! risk ( /ill fur!r encroa*+ on !
 valuable "t ( ! ,section1 ,i %all say a
 few words on a bran* ( physics :i* n v 
long ago w\ld h be5 consid]$ r a bran* (
 metaphysics4  ,i mean ! atomic !ory1   
or1 z x is n[ call$1 ! molecul> !ory ( !
 con/itution ( bodies4  ,n _m ye>s ago  
if we _h be5 ask$ 9 :at regions (       
physical sci5ce ! advance ( discov]y 0  
lea/ app>5t1 we %\ld h po9t$ to !       

hopelessly di/ant fix$ />s on ! "o h&1 &
 to ! inscrutable delicacy ( ! texture (
 mat]ial bodies on ! o!r4  ,inde$1 if we
 are to reg>d ,comte z 9 any degree     
repres5t+ ! sci5tific op9ion ( 8 "t1 !  
rese>* into :at takes place beyond our  
own sol> sy/em seem$ !n to be exce$+ly  
unpromis+1 if n altoge!r illusory4  ,!  
op9ion t ! bodies :i* we see & h&le1 :i*
 we c set 9 motion or leave at re/1 :i* 
we c break 9 pieces & de/roy1 are       
compos$ ( small] bodies :i* we _c see or
 h&le1 :i* are always 9 motion1 & :i* c 
nei!r be /opp$ nor brok5 9 pieces1 nor 9
 any way de/roy$ or depriv$ ( ! lea/ (  
_! prop]ties1 0 kn[n by ! "n ( ! ,atomic
 !ory4  ,x 0 associat$ ) ! names (      
,democritus1 ,epicurus1 & ,lucretius1 & 
0 commonly suppos$ to admit ! exi/5ce   
only ( atoms & void1 to ! exclusion (   
any o!r basis ( ?+s f ! univ]se4  ,9 _m 
physical reason+s & ma!matical          
calculations we are accu/om$ to argue z 
if su* sub/ances z air1 wat]1 or metal1 
:i* appe> to our s5ses uni=m & cont9u\s1

 7 /rictly & ma!matically uni=m &       
cont9u\s4  ,we "k t we c divide a p9t ( 
wat] into _m millions ( portions1 ea* ( 
:i* is z fully end[$ ) all ! prop]ties (
 wat] z ! :ole p9t 02 & x seems only    
natural to conclude t we might g on     
subdivid+ ! wat] = ev]1 j z we c nev]   
come to a limit 9 subdivid+ ! space 9   
:i* x is conta9$4  ,we h he>d h[ ,f>aday
 divid$ a gra9 ( gold into an           
inconceivable numb] ( sep>ate p>ticles1 
& we may see ,dr ,tyndall produce f a   
m]e suspicion ( nitrite ( butyle an     
imm5se cl\d1 ! m9ute visible portion (  
:i* is /ill cl\d1 & !re=e mu/ conta9 _m 
molecules ( nitrite ( butyle4  ,b       
evid5ce f diff]5t & indep5d5t s\rces is 
n[ cr[d+ 9 ^u u :i* compels u to admit t
 if we c\ld pu% ! process ( subdivision 
/ill fur!r we %\ld come to a limit1     
because ea* portion w\ld !n conta9 only 
"o molecule1 an individual body1 "o &   
indivisible1 unalt]able by any p[] 9    
nature4  ,ev5 9 our ord9>y exp]im5ts on 
v f9ely divid$ matt] we f9d t ! sub/ance

 is beg9n+ to lose ! prop]ties :i* x    
exhibits :5 9 a l>ge mass1 & t effects  
dep5d+ on ! individual action (         
molecules are beg9n+ to become prom95t4 
,! /udy ( ^! ph5om5a is at pres5t ! pa? 
:i* leads to ! developm5t ( molecul>    
sci5ce4  ,t sup]ficial t5sion ( liquids 
:i* is call$ capill>y attraction is "o (
 ^! ph5om5a4  ,ano!r important class (  
ph5om5a are ^? :i* are due to t motion (
 agitation by :i* ! molecules ( a liquid
 or gas are cont9ually work+ _! way f "o
 place to ano!r1 & cont9ually *ang+ _!  
c\rse1 l p hu/l$ 9 a cr[d4  ,on ?is     
dep5ds ! rate ( diffusion ( gases &     
liquids ?r\gh ea* o!r1 to ! /udy ( :i*1 
z "o ( ! keys ( molecul> sci5ce1 t      
unwe>i$ inquir] into nature's secrets1 !
 late ,pr(4 ,graham1 devot$ su* ardu\s  
lab\r4  ,! rate ( electrolytic          
conduction is1 accord+ to ,wi$emann's   
!ory1 influ5c$ by ! same cause2 & !     
conduction ( heat 9 fluids dep5ds       
probably on ! same k9d ( action4  ,9 !  
case ( gases1 a molecul> !ory has be5   

develop$ by ,clausius & o!rs1 capable ( 
ma!matical treatm5t1 & subject$ to      
exp]im5tal inve/igation2 & by ?is !ory  
ne>ly e kn[n me*anical prop]ty ( gases  
has be5 expla9$ on dynamical pr9ciples2 
s t ! prop]ties ( individual gase\s     
molecules are 9 a fair way to become    
objects ( sci5tific rese>*4  ,n[ ,mr    
,/oney has po9t$ out#a t ! num]ical     
results ( exp]im5ts on gases r5d] x     
probable t ! mean di/ance ( _! p>ticles 
at ! ord9>y temp]ature & pressure is a  
quantity ( ! same ord] ( magnitude z a  
million? ( a millimetre1 & ,sir ,william
 ,?omson has s9ce#b %ewn1 by sev]al     
indep5d5t l9es ( argum5t1 drawn f       
ph5om5a s diff]5t 9 !mselves z !        
electrification ( metals by contact1 !  
t5sion ( soap-bubbles1 & ! friction (   
air1 t 9 ord9>y solids & liquids !      
av]age di/ance betwe5 contigu\s         
molecules is less ?an ! hundr$-million?1
 & great] ?an ! two-?\s&-million? ( a   
c5timetre4  #a ,phil4 ,mag41 ,aug4      
#ahfh4 #b ,nature1 ,m>* #ca1 #ahgj4     

,^!1 ( c\rse1 are exce$+ly r\gh         
e/imates1 = !y are d]iv$ f measurem5ts  
"s ( :i* are /ill confess$ly v r\gh2 b  
if at ! pres5t "t1 we c =m ev5 a r\gh   
plan = arriv+ at results ( ?is k9d1 we  
may hope t1 z our means ( exp]im5tal    
inquiry become m accurate & m v>i$1 our 
conception ( a molecule w become m      
def9ite1 s t we may be able at no di/ant
 p]iod to e/imate its weight ) a great] 
degree ( precision4  ,a !ory1 :i* ,sir  
,w4 ,?omson has f\nd$ on ,helmholtz's   
spl5did hydrodynamical !orems1 seeks = !
 prop]ties ( molecules 9 ! r+ vortices (
 a uni=m1 frictionless1 incompressible  
fluid4  ,su* :irl+ r+s may be se5 :5 an 
exp]i5c$ smok] s5ds out a dext]\s puff (
 smoke into ! /ill air1 b a m evanesc5t 
ph5om5on x is difficult to conceive4    
,?is evanesc5ce is ow+ to ! viscosity ( 
! air2 b ,helmholtz has %ewn t 9 a      
p]fect fluid su* a :irl+ r+1 if once    
g5]at$1 w\ld g on :irl+ = ev]1 w\ld     
always consi/ ( ! v same portion ( !    
fluid :i* 0 fir/ set :irl+1 & c\ld nev] 

be cut 9 two by any natural cause4  ,!  
g5]ation ( a r+-vortex is ( c\rse       
equally beyond ! p[] ( natural causes1 b
 once g5]at$1 x has ! prop]ties (       
individuality1 p]man5ce 9 quantity1 &   
inde/ructibility4  ,x is also ! recipi5t
 ( impulse & ( en]gy1 :i* is all we c   
affirm ( matt]2 & ^! r+-vortices are    
capable ( su* v>i$ connexions & knott$  
self-involutions1 t ! prop]ties (       
diff]5tly knott$ vortices mu/ be z      
diff]5t z ^? ( diff]5t k9ds ( molecules 
c be4  ,if a !ory ( ?is k9d %\ld be     
f\nd1 aft] conqu]+ ! enorm\s ma!matical 
difficulties ( ! subject1 to repres5t 9 
any degree ! actual prop]ties (         
molecules1 x w /& 9 a v diff]5t         
sci5tific position f ^? !ories (        
molecul> action :i* are =m$ by inve/+ ! 
molecule ) an arbitr>y sy/em ( c5tral   
=ces inv5t$ expressly to acc\nt = !     
obs]v$ ph5om5a4  ,9 ! vortex !ory we h  
no?+ arbitr>y1 no c5tral =ces or occult 
prop]ties ( any o!r k9d4  ,we h no?+ b  
matt] & motion1 & :5 ! vortex is once   

/>t$ its prop]ties are all det]m9$ f !  
orig9al impetus1 & no fur!r assumptions 
are possible4  ,ev5 9 ! pres5t          
undevelop$ /ate ( ! !ory1 !             
contemplation ( ! individuality &       
inde/ructibility ( a r+-vortex 9 a      
p]fect fluid _c fail to di/urb !        
commonly receiv$ op9ion t a molecule1 9 
ord] to be p]man5t1 mu/ be a v h>d body4
  ,9 fact "o ( ! fir/ conditions :i* a  
molecule mu/ fulfil is1 app>5tly1       
inconsi/5t ) its be+ a s+le h>d body4   
,we "k f ^? spectroscopic rese>*es :i* h
 ?r[n s mu* light on diff]5t bran*es (  
sci5ce1 t a molecule c be set into a    
/ate ( int]nal vibration1 9 :i* x gives 
(f to ! surr\nd+ m$ium light ( def9ite  
refrangibility--light1 t is1 ( def9ite  
wave-l5g? & def9ite p]iod ( vibration4  
,! fact t all ! molecules 7say1 (       
hydrog57 :i* we c procure = our         
exp]im5ts1 :5 agitat$ by heat or by !   
passage ( an electric sp>k1 vibrate     
precisely 9 ! same p]iodic "t1 or1 to   
speak m accurately1 t _! vibrations are 

compos$ ( a sy/em ( simple vibrations   
hav+ always ! same p]iods1 is a v       
rem>kable fact4  ,i mu/ leave x to o!rs 
to describe ! progress ( t spl5did s]ies
 ( spectroscopic discov]ies by :i* !    
*emi/ry ( ! heav5ly bodies has be5      
br\ght )9 ! range ( human inquiry4  ,i  
wi% r to direct y\r att5tion to ! fact  
t1 n only has e molecule ( t]re/rial    
hydrog5 ! same sy/em ( p]iods ( free    
vibration1 b t ! spectroscopic          
exam9ation ( ! light ( ! sun & />s %ews 
t1 9 regions ! di/ance ( :i* we c only  
feebly imag9e1 !re are molecules vibrat+
 9 z exact unison ) ! molecules (       
t]re/rial hydrog5 z two tun+-=ks tun$ to
 conc]t pit*1 or two wat*es regulat$ to 
sol> "t4  ,n[ ?is absolute equality 9 ! 
magnitude ( quantities1 occurr+ 9 all   
p>ts ( ! univ]se1 is wor? our           
consid]ation4  ,! dim5sions ( individual
 natural bodies are ei!r q indet]m9ate1 
z 9 ! case ( planets1 /ones1 trees1 c41 
or !y v>y )9 mod]ate limits1 z 9 ! case 
( se$s1 eggs1 c42 b ev5 9 ^! cases small

 quantitative diff]5ces are met ) :i* d 
n int]f]e ) ! ess5tial prop]ties ( !    
body4  ,ev5 cry/als1 :i* are s def9ite 9
 geometrical =m1 are v>iable ) respect  
to _! absolute dim5sions4  ,among !     
works ( man we sometimes f9d a c]ta9    
degree ( uni=mity4  ,!re is a uni=mity  
among ! diff]5t bullets :i* are ca/ 9 ! 
same m\ld1 & ! diff]5t copies ( a book  
pr9t$ f ! same type4  ,if we exam9e !   
co9s1 or ! weights & measures1 ( a      
civiliz$ c\ntry1 we f9d a uni=mity1 :i* 
is produc$ by c>eful adju/m5t to /&>ds  
made & provid$ by ! /ate4  ,! degree (  
uni=mity ( ^! national /&>ds is a       
measure ( t _s ( ju/ice 9 ! nation :i*  
has enact$ laws to regulate !m & appo9t$
 (fic]s to te/ !m4  ,?is subject is "o 9
 :i* we1 z a sci5tific body1 take a w>m 
int]e/2 & y are all aw>e ( ! va/ am\nt (
 sci5tific "w :i* has be5 exp5d$1 &     
pr(itably exp5d$1 9 provid+ weights &   
measures = comm]cial & sci5tific        
purposes4  ,! e>? has be5 measur$ z a   
basis = a p]man5t /&>d ( l5g?1 & e      

prop]ty ( metals has be5 inve/igat$ to  
gu>d aga9/ any alt]ation ( ! mat]ial    
/&>ds :5 made4  ,to weigh or measure any
 ?+ ) mod]n accuracy1 requires a c\rse (
 exp]im5t & calculation 9 :i* almo/ e   
bran* ( physics & ma!matics is br\ght   
into requisition4  ,yet1 aft] all1 !    
dim5sions ( our e>? & its "t ( rotation1
 ?\gh1 relatively to our pres5t means ( 
comp>ison1 v p]man5t1 are n s by any    
physical necessity4  ,! e>? might       
contract by cool+1 or x might be enl>g$ 
by a lay] ( meteorites fall+ on x1 or   
its rate ( revolution might sl[ly       
slack51 & yet x w\ld cont9ue to be z mu*
 a planet z be=e4  ,b a molecule1 say ( 
hydrog51 if ei!r its mass or its "t (   
vibration 7 to be alt]$ 9 ! lea/1 w\ld  
no long] be a molecule ( hydrog54  ,if1 
!n1 we wi% to obta9 /&>ds ( l5g?1 "t1 & 
mass :i* %all be absolutely p]man5t1 we 
mu/ seek !m n 9 ! dim5sions1 or !       
motion1 or ! mass ( our planet1 b 9 !   
wave-l5g?1 ! p]iod ( vibration1 & !     
absolute mass ( ^! imp]i%able &         

unalt]able & p]fectly simil> molecules4 
,:5 we f9d t "h1 & 9 ! />ry heav5s1 !re 
are innum]able multitudes ( little      
bodies ( exactly ! same mass1 s _m1 & no
 m1 to ! gra91 & vibrat+ 9 exactly !    
same "t1 s _m times1 & no m1 9 a second1
 & :5 we reflect t no p[] 9 nature c n[ 
alt] 9 ! lea/ ei!r ! mass or ! p]iod (  
any "o ( !m1 we seem to h advanc$ along 
! pa? ( natural k to "o ( ^? po9ts at   
:i* we mu/ accept ! guidance ( t fai? by
 :i* we und]/& t t :i* is se5 0 n made (
 ?+s :i* d appe>4  ,"o ( ! mo/ rem>kable
 results ( ! progress ( molecul> sci5ce 
is ! light x has ?r[n on ! nature (     
irrev]sible processes--processes1 t is1 
:i* always t5d t[>ds & nev] away f a    
c]ta9 limit+ /ate4  ,?us1 if two gases  
be put into ! same vessel1 !y become    
mix$1 & ! mixture t5ds cont9ually to    
become m uni=m4  ,if two unequally heat$
 portions ( ! same gas are put into !   
vessel1 some?+ ( ! k9d takes place1 & ! 
:ole t5ds to become ( ! same temp]ature4
  ,if two unequally heat$ solid bodies  

be plac$ 9 contact1 a cont9ual          
approximation ( bo? to an int]m$iate    
temp]ature takes place4  ,9 ! case ( !  
two gases1 a sep>ation may be effect$ by
 *emical means2 b 9 ! o!r two cases !   
=m] /ate ( ?+s _c be re/or$ by any      
natural process4  ,9 ! case ( !         
conduction or diffusion ( heat ! process
 is n only irrev]sible1 b x involves !  
irrev]sible dim9ution ( t "p ( ! :ole   
/ock ( !rmal en]gy :i* is capable ( be+ 
conv]t$ into me*anical "w4  ,?is is     
,?omson's !ory ( ! irrev]sible          
dissipation ( en]gy1 & x is equival5t to
 ! doctr9e ( ,clausius conc]n+ ! gr[? ( 
:at he calls ,entropy4  ,! irrev]sible  
"* ( ?is process is /rik+ly embodi$ 9   
,f\ri]'s !ory ( ! conduction ( heat1 :]e
 ! =mulae !mselves indicate1 = all      
positive values ( ! "t1 a possible      
solution :i* cont9ually t5ds to ! =m ( a
 uni=m diffusion ( heat4  ,b if we      
attempt to asc5d ! /ream ( "t by giv+ to
 its symbol cont9ually dim9i%+ values1  
we are l$ up to a /ate ( ?+s 9 :i* !    

=mula has :at is call$ a critical value2
 & if we inquire into ! /ate ( ?+s !    
in/ant be=e1 we f9d t ! =mula becomes   
absurd4  ,we ?us arrive at ! conception 
( a /ate ( ?+s :i* _c be conceiv$ z !   
physical result ( a previ\s /ate ( ?+s1 
& we f9d t ?is critical condition       
actually exi/$ at an epo* n 9 ! utmo/   
dep?s ( a pa/ et]nity1 b sep>at$ f !    
pres5t "t by a f9ite int]val4  ,?is idea
 ( a beg9n+ is "o :i* ! physical        
rese>*es ( rec5t times h br\ght home to 
u1 m ?an any obs]v] ( ! c\rse (         
sci5tific ?\ght 9 =m] times w\ld h _h   
reason to expect4  ,b ! m9d ( man is n1 
l ,f\ri]'s heat$ body1 cont9ually settl+
 d[n into an ultimate /ate ( quiet      
uni=mity1 ! "* ( :i* we c already       
pr$ict2 x is r l a tree1 %oot+ out      
bran*es :i* adapt !mselves to ! new     
aspects ( ! sky t[>ds :i* !y climb1 &   
roots :i* contort !mselves among !      
/range /rata ( ! e>? into :i* !y delve4 
,to u :o brea! only ! _s ( our own age1 
& "k only ! *>act]i/ics ( contempor>y   

?\ght1 x is z impossible to pr$ict !    
g5]al tone ( ! sci5ce ( ! future z x is 
to anticipate ! p>ticul> discov]ies :i* 
x w make4  ,physical rese>* is          
cont9ually reveal+ to u new features (  
natural processes1 & we are ?us compell$
 to se>* = new =ms ( ?\ght appropriate  
to ^! features4  ,h5ce ! importance ( a 
c>eful /udy ( ^? relations betwe5       
ma!matics & ,physics :i* det]m9e !      
conditions "u :i* ! ideas d]iv$ f "o    
dep>tm5t ( physics may be safely us$ 9  
=m+ ideas to be employ$ 9 a new         
dep>tm5t4  ,! figure ( spee* or ( ?\ght 
by :i* we transf] ! language & ideas ( a
 famili> sci5ce to "o ) :i* we are less 
acqua9t$ may be call$ ,sci5tific        
,metaphor4  ,?us ! words ,velocity1     
,mom5tum1 ,=ce1 c4 h acquir$ c]ta9      
precise mean+s 9 ,elem5t>y ,dynamics4   
,!y are also employ$ 9 ! ,dynamics ( a  
,connect$ ,sy/em 9 a s5se :i*1 ?\gh     
p]fectly analog\s to ! elem5t>y s5se1 is
 wid] & m g5]al4  ,^! g5]aliz$ =ms (    
elem5t>y ideas may be call$ metaphorical

 t]ms 9 ! s5se 9 :i* e ab/ract t]m is   
metaphorical4  ,! *>act]i/ic ( a truly  
sci5tific sy/em ( metaphors is t ea* t]m
 9 its metaphorical use reta9s all !    
=mal relations to ! o!r t]ms ( ! sy/em  
:i* x _h 9 its orig9al use4  ,! me?od is
 !n truly sci5tific--t is1 n only a     
legitimate product ( sci5ce1 b capable (
 g5]at+ sci5ce 9 its turn4  ,!re are    
c]ta9 electrical ph5om5a1 aga91 :i* are 
connect$ toge!r by relations ( ! same =m
 z ^? :i* connect dynamical ph5om5a4    
,to apply to ^! ! phrases ( dynamics )  
prop] di/9ctions & provisional          
res]vations is an example ( a metaphor (
 a bold] k9d2 b x is a legitimate       
metaphor if x conveys a true idea ( !   
electrical relations to ^? :o h be5     
already tra9$ 9 dynamics4  ,suppose1 !n1
 t we h successfully introduc$ c]ta9    
ideas belong+ to an elem5t>y sci5ce by  
apply+ !m metaphorically to "s new class
 ( ph5om5a4  ,x becomes an important    
philosophical "q to det]m9e 9 :at degree
 ! applicability ( ! old ideas to ! new 

subject may be tak5 z evid5ce t ! new   
ph5om5a are physically simil> to ! old4 
,! be/ in/ances = ! det]m9ation ( ?is "q
 are ^? 9 :i* two diff]5t explanations h
 be5 giv5 ( ! same ?+4  ,! mo/ celebrat$
 case ( ?is k9d is t ( ! corpuscul> & ! 
undulatory !ories ( light4  ,up to a    
c]ta9 po9t ! ph5om5a ( light are equally
 well expla9$ by bo?2 beyond ?is po9t1  
"o ( !m fails4  ,to und]/& ! true       
relation ( ^! !ories 9 t "p ( ! field   
:]e !y seem equally applicable we mu/   
look at !m 9 ! light :i* ,hamilton has  
?r[n ^u !m by 8 discov]y t to e         
bra*i/o*rone problem !re corresponds a  
problem ( free motion1 involv+ diff]5t  
velocities & times1 b result+ 9 ! same  
geometrical pa?4  ,pr(essor ,tait has   
writt5 a v int]e/+ pap] on ?is subject4 
,accord+ to a !ory ( electricity :i* is 
mak+ great progress 9 ,g]many1 two      
electrical p>ticles act on "o ano!r     
directly at a di/ance1 b ) a =ce :i*1   
accord+ to ,web]1 dep5ds on _! relative 
velocity1 & accord+ to a !ory h9t$ at by

 ,gauss1 & develop$ by ,riemann1 ,lor5z1
 & ,neumann1 acts n in/antane\sly1 b    
aft] a "t dep5d+ on ! di/ance4  ,! p[] )
 :i* ?is !ory1 9 ! h&s ( ^! em95t m51   
expla9s e k9d ( electrical ph5om5a mu/  
be /udi$ 9 ord] to be appreciat$4       
,ano!r !ory ( electricity1 :i* ,i pref]1
 d5ies action at a di/ance & attributes 
electric action to t5sions & pressures 9
 an all-p]vad+ m$ium1 ^! /resses be+ !  
same 9 k9d ) ^? famili> to eng9e]s1 & ! 
m$ium be+ id5tical ) t 9 :i* light is   
suppos$ to be propagat$4  ,bo? ^! !ories
 are f\nd to expla9 n only ! ph5om5a by 
! aid ( :i* !y 7 orig9ally con/ruct$1 b 
o!r ph5om5a1 :i* 7 n ?\ght ( or p]haps n
 kn[n at ! "t2 & bo? h indep5d5tly      
arriv$ at ! same num]ical result1 :i*   
gives ! absolute velocity ( light 9 t]ms
 ( electrical quantities4  ,t !ories    
app>5tly s fundam5tally oppos$ %\ld h s 
l>ge a field ( tru? common to bo? is a  
fact ! philosophical importance ( :i* we
 _c fully appreciate till we h rea*$ a  
sci5tific altitude f :i* ! true relation

 betwe5 hypo!ses s diff]5t c be se54  ,i
 %all only make "o m rem>k on ! relation
 betwe5 ,ma!matics & ,physics4  ,9      
!mselves1 "o is an op]ation ( ! m9d1 !  
o!r is a dance ( molecules4  ,!         
molecules h laws ( _! own1 "s ( :i* we  
select z mo/ intelligible to u & mo/    
am5able to our calculation4  ,we =m a   
!ory f ^! p>tial data1 & we ascribe any 
deviation ( ! actual ph5om5a f ?is !ory 
to di/urb+ causes4  ,at ! same "t we    
confess t :at we call di/urb+ causes are
 simply ^? p>ts ( ! true circum/ances   
:i* we d n "k or h neglect$1 & we       
endeav\r 9 future to take acc\nt ( !m4  
,we ?us ackn[l$ge t ! s-call$ di/urbance
 is a m]e figm5t ( ! m9d1 n a fact (    
nature1 & t 9 natural action !re is no  
di/urbance4  ,b ?is is n ! only way 9   
:i* ! h>mony ( ! mat]ial ) ! m5tal      
op]ation may be di/urb$4  ,! m9d ( !    
ma!matician is subject to _m di/urb+    
causes1 su* z fatigue1 loss ( memory1 & 
ha/y conclusions2 & x is f\nd t1 f ^! & 
o!r causes1 ma!maticians make mi/akes4  

,i am n prep>$ to d5y t1 to "s m9d ( a  
high] ord] ?an ours1 ea* ( ^! errors    
might be trac$ to ! regul> op]ation ( ! 
laws ( actual ?9k+2 9 fact we ourselves 
(t5 d detect1 n only errors (           
calculation1 b ! causes ( ^! errors4    
,?is1 h[ev]1 by no means alt]s our      
conviction t !y are errors1 & t "o      
process ( ?\ght is "r & ano!r process   
wrong4  ,i  ,"o ( ! mo/ pr(\nd          
ma!maticians & ?9k]s ( our "t1 ! late   
,george ,boole1 :5 reflect+ on ! precise
 & almo/ ma!matical "* ( ! laws ( "r    
?9k+ z comp>$ ) ! exce$+ly p]plex+ ?\gh 
p]haps equally det]m9ate laws ( actual &
 fallible ?9k+1 0 l$ to ano!r ( ^? po9ts
 ( view f :i* ,sci5ce seems to look out 
into a region beyond h] own doma94  ,we 
mu/ admit1 he says1 t !re exi/ laws 7(  
?\ght7 :i* ev5 ! rig\r ( _! ma!matical  
=ms does n pres]ve f violation4  ,we mu/
 ascribe to !m an au?ority1 ! ess5ce (  
:i* does n consi/ 9 p[]1 a supremacy :i*
 ! analogy ( ! inviolable ord] ( !      
natural _w 9 no way assi/s u to         

compreh5d4     ,introductory ,lecture on
 ,exp]im5tal ,physics4  ,james ,cl]k    
,maxwell   ,! ,univ]sity ( ,cambridge1 9
 accordance ) t law ( its evolution1 by 
:i*1 :ile ma9ta9+ ! /ricte/ cont9uity   
betwe5 ! successive phases ( its hi/ory1
 x adapts itself ) m or less promptness 
to ! requirem5ts ( ! times1 has lately  
in/itut$ a c\rse ( ,exp]im5tal ,physics4
  ,?is c\rse ( /udy1 :ile x requires u  
to ma9ta9 9 action all ^? p[]s (        
att5tion & analysis :i* h be5 s long    
cultivat$ 9 ! ,univ]sity1 calls on u to 
ex]cise our s5ses 9 obs]vation1 & our   
h&s 9 manipulation4  ,! famili> app>atus
 ( p51 ink1 & pap] w no long] be        
suffici5t = u1 & we %all require m room 
?an t af=d$ by a seat at a desk1 & a    
wid] area ?an t ( ! black bo>d4  ,we owe
 x to ! munific5ce ( our ,*ancellor1 t1 
:atev] be ! "* 9 o!r respects ( !       
exp]im5ts :i* we hope h]eaft] to        
conduct1 ! mat]ial facilities = _! full 
developm5t w be ^u a scale :i* has n    
hi!rto be5 surpass$4  ,! ma9 feature1   

!re=e1 ( ,exp]im5tal ,physics at        
,cambridge is ! ,devon%ire ,physical    
,laboratory1 & ,i ?9k x desirable t on !
 pres5t occasion1 be=e we ent] on !     
details ( any special /udy1 we %\ld     
consid] by :at means we1 ! ,univ]sity ( 
,cambridge1 may1 z a liv+ body1         
appropriate & vitalise ?is new organ1 ! 
outw>d %ell ( :i* we expect soon to rise
 be=e u4 ,! c\rse ( /udy at ?is         
,univ]sity has always includ$ ,natural  
,philosophy1 z well z ,pure ,ma!matics4 
,to diffuse a s\nd k ( ,physics1 & to   
imbue ! m9ds ( our /ud5ts ) correct     
dynamical pr9ciples1 h be5 long reg>d$ z
 among our highe/ functions1 & v few ( u
 c n[ place ourselves 9 ! m5tal         
condition 9 :i* ev5 su* philosoph]s z ! 
great ,desc>tes 7 involv$ 9 ! days be=e 
,newton _h ann\nc$ ! true laws ( !      
motion ( bodies4  ,inde$ ! cultivation &
 diffusion ( s\nd dynamical ideas has   
already effect$ a great *ange 9 !       
language & ?\ghts ev5 ( ^? :o make no   
pret5sions to sci5ce1 & we are daily    

receiv+ fre% pro(s t ! popul>isation (  
sci5tific doctr9es is produc+ z great an
 alt]ation 9 ! m5tal /ate ( society z ! 
mat]ial applications ( sci5ce are       
effect+ 9 its outw>d life4  ,su* inde$  
is ! respect paid to sci5ce1 t ! mo/    
absurd op9ions may become curr5t1       
provid$ !y are express$ 9 language1 !   
s\nd ( :i* recals "s well-kn[n sci5tific
 phrase4  ,if society is ?us prep>$ to  
receive all k9ds ( sci5tific doctr9es1 x
 is our "p to provide = ! diffusion &   
cultivation1 n only ( true sci5tific    
pr9ciples1 b ( a _s ( s\nd criticism1   
f\nd$ on an exam9ation ( ! evid5ces on  
:i* /atem5ts app>5tly sci5tific dep5d4  
,:5 we %all be able to employ 9         
sci5tific education1 n only ! tra9$     
att5tion ( ! /ud5t1 & 8 famili>ity )    
symbols1 b ! ke5ness ( 8 eye1 !         
quickness ( 8 e>1 ! delicacy ( 8 t\*1 & 
! adroitness ( 8 f+]s1 we %all n only   
ext5d our influ5ce ov] a class ( m5 :o  
are n fond ( cold ab/ractions1 b1 by    
op5+ at once all ! gateways ( k1 we %all

 ensure ! association ( ! doctr9es (    
sci5ce ) ^? elem5t>y s5sations :i* =m ! 
obscure backgr\nd ( all our consci\s    
?\ghts1 & :i* l5d a vividness & relief  
to ideas1 :i*1 :5 pres5t$ z m]e ab/ract 
t]ms1 are apt to fade entirely f !      
memory4  ,9 a c\rse ( ,exp]im5tal       
,physics we may consid] ei!r ! ,physics 
or ! ,exp]im5ts z ! lead+ feature4  ,we 
may ei!r employ ! exp]im5ts to illu/rate
 ! ph5om5a ( a p>ticul> bran* (         
,physics1 or we may make "s physical    
rese>* 9 ord] to exemplify a p>ticul>   
exp]im5tal me?od4  ,9 ! ord] ( "t1 we   
%\ld beg91 9 ! ,lecture ,room1 ) a c\rse
 ( lectures on "s bran* ( ,physics aid$ 
by exp]im5ts ( illu/ration1 & conclude1 
9 ! ,laboratory1 ) a c\rse ( exp]im5ts (
 rese>*4  ,let me say a few words on ^! 
two classes ( exp]im5ts1--,exp]im5ts (  
,illu/ration & ,exp]im5ts ( ,rese>*4 ,! 
aim ( an exp]im5t ( illu/ration is to   
?r[ light ^u "s sci5tific idea s t !    
/ud5t may be enabl$ to grasp x4  ,!     
circum/ances ( ! exp]im5t are s arrang$ 

t ! ph5om5on :i* we wi% to obs]ve or to 
exhibit is br\ght into prom95ce1 in/ead 
( be+ obscur$ & entangl$ among o!r      
ph5om5a1 z x is :5 x occurs 9 ! ord9>y  
c\rse ( nature4  ,to exhibit illu/rative
 exp]im5ts1 to enc\rage o!rs to make !m1
 & to cultivate 9 e way ! ideas on :i*  
!y ?r[ light1 =ms an important "p ( our 
duty4  ,! simpl] ! mat]ials ( an        
illu/rative exp]im5t1 & ! m famili> !y  
are to ! /ud5t1 ! m ?or\ghly is he      
likely to acquire ! idea :i* x is meant 
to illu/rate4  ,! educational value (   
su* exp]im5ts is (t5 inv]sely           
proportional to ! complexity ( !        
app>atus4  ,! /ud5t :o uses home-made   
app>atus1 :i* is always go+ wrong1 (t5  
le>ns m ?an "o :o has ! use ( c>efully  
adju/$ in/rum5ts1 to :i* he is apt to   
tru/1 & :i* he d>es n take to pieces4   
,x is v necess>y t ^? :o are try+ to    
le>n f books ! facts ( physical sci5ce  
%\ld be enabl$ by ! help ( a few        
illu/rative exp]im5ts to recognise ^!   
facts :5 !y meet ) !m out ( doors4      

,sci5ce appe>s to u ) a v diff]5t aspect
 aft] we h f\nd out t x is n 9 lecture  
rooms only1 & by means ( ! electric     
light project$ on a scre51 t we may     
witness physical ph5om5a1 b t we may f9d
 illu/rations ( ! highe/ doctr9es (     
sci5ce 9 games & gymna/ics1 9 travell+  
by l& & by wat]1 9 /orms ( ! air & ( !  
sea1 & :]ev] !re is matt] 9 motion4     
,?is habit ( recognis+ pr9ciples amid ! 
endless v>iety ( _! action c nev]       
degrade our s5se ( ! sublimity ( nature1
 or m> our enjoym5t ( its beauty4  ,on !
 contr>y1 x t5ds to rescue our sci5tific
 ideas f t vague condition 9 :i* we too 
(t5 leave !m1 buri$ among ! o!r products
 ( a lazy cr$ulity1 & to raise !m into  
_! prop] position among ! doctr9es 9 :i*
 our fai? is s assur$1 t we are ready at
 all times to act on !m4  ,exp]im5ts (  
illu/ration may be ( v diff]5t k9ds4    
,"s may be adaptations ( ! commone/     
op]ations ( ord9>y life1 o!rs may be    
c>efully arrang$ exhibitions ( "s       
ph5om5on :i* occurs only "u peculi>     

conditions4  ,!y all1 h[ev]1 agree 9    
?is1 t _! aim is to pres5t "s ph5om5on  
to ! s5ses ( ! /ud5t 9 su* a way t he   
may associate ) x ! appropriate         
sci5tific idea4  ,:5 he has grasp$ ?is  
idea1 ! exp]im5t :i* illu/rates x has   
s]v$ its purpose4  ,9 an exp]im5t (     
rese>*1 on ! o!r h&1 ?is is n ! pr9cipal
 aim4  ,x is true t an exp]im5t1 9 :i* !
 pr9cipal aim is to see :at happ5s "u   
c]ta9 conditions1 may be reg>d$ z an    
exp]im5t ( rese>* by ^? :o are n yet    
famili> ) ! result1 b 9 exp]im5tal      
rese>*es1 /rictly s call$1 ! ultimate   
object is to measure some?+ :i* we h    
already se5--to obta9 a num]ical e/imate
 ( "s magnitude4  ,exp]im5ts ( ?is      
class--^? 9 :i* measurem5t ( "s k9d is  
involv$1 are ! prop] "w ( a ,physical   
,laboratory4  ,9 e exp]im5t we h fir/ to
 make our s5ses famili> ) ! ph5om5on1 b 
we mu/ n /op "h1 we mu/ f9d out :i* (   
its features are capable ( measurem5t1 &
 :at measurem5ts are requir$ 9 ord] to  
make a complete specification ( !       

ph5om5on4 ,we mu/ !n make ^!            
measurem5ts1 & d$uce f !m ! result :i*  
we require to f9d4  ,?is *>act]i/ic (   
mod]n exp]im5ts--t !y consi/ pr9cipally 
( measurem5ts1--is s prom95t1 t ! op9ion
 seems to h got abroad1 t 9 a few ye>s  
all ! great physical con/ants w h be5   
approximately e/imat$1 & t ! only       
occupation :i* w !n be left to m5 (     
sci5ce w be to c>ry on ^! measurem5ts to
 ano!r place ( decimals4  ,if ?is is    
really ! /ate ( ?+s to :i* we are       
approa*+1 our ,laboratory may p]haps    
become celebrat$ z a place ( consci5ti\s
 lab\r & consummate skill1 b x w be out 
( place 9 ! ,univ]sity1 & ought r to be 
class$ ) ! o!r great work%ops ( our     
c\ntry1 :]e equal ability is direct$ to 
m useful ends4  ,b we h no "r to ?9k ?us
 ( ! unse>*able ri*es ( creation1 or ( !
 untri$ f]tility ( ^? fre% m9ds into :i*
 ^! ri*es w cont9ue to be p\r$4  ,x may 
possibly be true t1 9 "s ( ^? fields (  
discov]y :i* lie op5 to su* r\gh        
obs]vations z c be made )\t artificial  

me?ods1 ! great explor]s ( =m] times h  
appropriat$ mo/ ( :at is valuable1 & t !
 glean+s :i* rema9 are s\ght aft]1 r =  
_! ab/rus5ess1 ?an = _! intr9sic wor?4  
,b ! hi/ory ( sci5ce %ews t ev5 dur+ t  
phase ( h] progress 9 :i* %e devotes    
h]self to improv+ ! accuracy ( !        
num]ical measurem5t ( quantities ) :i*  
%e has long be5 famili>1 %e is prep>+ ! 
mat]ials = ! subjugation ( new regions1 
:i* w\ld h rema9$ unkn[n if %e _h be5   
cont5t$ ) ! r\gh me?ods ( h] e>ly       
pione]s4  ,i might br+ =w>d in/ances    
ga!r$ f e bran* ( sci5ce1 %ew+ h[ !     
lab\r ( c>eful measurem5t has be5 rew>d$
 by ! discov]y ( new fields ( rese>*1 & 
by ! developm5t ( new sci5tific ideas4  
,b ! hi/ory ( ! sci5ce ( t]re/rial      
magnetism af=ds u a suffici5t example ( 
:at may be done by ,exp]im5ts 9 ,conc]t1
 su* z we hope "s day to p]=m 9 our     
,laboratory4  ,t celebrat$ travell]1    
,humboldt1 0 pr(\ndly impress$ ) !      
sci5tific value ( a comb9$ ef=t to be   
made by ! obs]v]s ( all nations1 to     

obta9 accurate measurem5ts ( ! magnetism
 ( ! e>?2 & we owe x ma9ly to 8         
en?usiasm = sci5ce1 8 great reputation &
 8 wide-spread influ5ce1 t n only       
private m5 ( sci5ce1 b ! gov]nm5ts ( mo/
 ( ! civilis$ nations1 our own among !  
numb]1 7 induc$ to take "p 9 !          
ent]prise4  ,b ! actual work+ out ( !   
s*eme1 & ! arrangem5ts by :i* ! lab\rs (
 ! obs]v]s 7 s direct$ z to obta9 ! be/ 
results1 we owe to ! great ma!matician  
,gauss1 work+ along ) ,web]1 ! future   
f\nd] ( ! sci5ce ( electro-magnetic     
measurem5t1 9 ! magnetic obs]vatory (   
,gott+51 & aid$ by ! skill ( !          
in/rum5t-mak] ,leys]4  ,^! m51 h[ev]1   
did n "w alone4  ,numb]s ( sci5tific m5 
jo9$ ! ,magnetic ,union1 le>n$ ! use ( !
 new in/rum5ts & ! new me?ods ( r$uc+ ! 
obs]vations2 & 9 e city ( ,europe y     
might see !m1 at c]ta9 /at$ times1      
sitt+1 ea* 9 8 cold wood5 %$1 ) 8 eye   
fix$ at ! telescope1 8 e> att5tive to ! 
clock1 & 8 p5cil record+ 9 8 note-book !
 in/antane\s position ( ! susp5d$       

magnet4  ,bacon's conception (          
,exp]im5ts 9 conc]t 0 ?us realis$1 !    
scatt]$ =ces ( sci5ce 7 conv]t$ into a  
regul> army1 & emulation & jeal\sy      
became out ( place1 = ! results obta9$  
by any "o obs]v] 7 ( no value till !y 7 
comb9$ ) ^? ( ! o!rs4  ,! increase 9 !  
accuracy & complet5ess ( magnetic       
obs]vations :i* 0 obta9$ by ! new me?od1
 op5$ up fields ( rese>* :i* 7 h>dly    
suspect$ to exi/ by ^? ^: obs]vations ( 
! magnetic ne$le _h be5 conduct$ 9 a m  
primitive mann]4  ,we mu/ res]ve = its  
prop] place 9 our c\rse any detail$     
description ( ! di/urbances to :i* !    
magnetism ( our planet is f\nd to be    
subject4  ,"s ( ^! di/urbances are      
p]iodic1 foll[+ ! regul> c\rses ( ! sun 
& moon4  ,o!rs are sudd51 & are call$   
magnetic /orms1 b1 l ! /orms ( !        
atmosph]e1 !y h _! kn[n seasons (       
frequ5cy4  ,! la/ & ! mo/ my/]i\s ( ^!  
magnetic *anges is t secul> v>iation by 
:i* ! :ole "* ( ! e>?1 z a great magnet1
 is be+ sl[ly modifi$1 :ile ! magnetic  

poles creep on1 f c5tury to c5tury1     
along _! w9d+ track 9 ! pol> regions4   
,we h ?us le>n$ t ! int]ior ( ! e>? is  
subject to ! influ5ces ( ! heav5ly      
bodies1 b t besides ?is !re is a        
con/antly progressive *ange go+ on1 !   
cause ( :i* is entirely unkn[n4  ,9 ea* 
( ! magnetic obs]vatories ?r\gh\t ! _w  
an arrangem5t is at "w1 by means ( :i* a
 susp5d$ magnet directs a ray ( light on
 a prep>r$ %eet ( pap] mov$ by          
clockwork4  ,on t pap] ! nev]-re/+ he>t 
( ! e>? is n[ trac+1 9 telegraphic      
symbols :i* w "o day be int]pret$1 a    
record ( its pulsations & its flutt]+s1 
z well z ( t sl[ b mighty work+ :i* w>ns
 u t we mu/ n suppose t ! inn] hi/ory ( 
our planet is end$4  ,b ?is great       
exp]im5tal rese>* on ,t]re/rial         
,magnetism produc$ la/+ effects on !    
progress ( sci5ce 9 g5]al4  ,i ne$ only 
m5tion "o or two in/ances4  ,! new      
me?ods ( measur+ =ces 7 successfully    
appli$ by ,web] to ! num]ical           
det]m9ation ( all ! ph5om5a (           

electricity1 & v soon aft]w>ds !        
electric telegraph1 by conf]r+ a        
comm]cial value on exact num]ical       
measurem5ts1 contribut$ l>gely to !     
advancem5t1 z well z to ! diffusion (   
sci5tific k4  ,b x is n 9 ^! m mod]n    
bran*es ( sci5ce alone t ?is influ5ce is
 felt4  ,x is to ,gauss1 to ! ,magnetic 
,union1 & to magnetic obs]v]s 9 g5]al1 t
 we owe our deliv]ance f t absurd me?od 
( e/imat+ =ces by a v>iable /&>d :i*    
prevail$ s long ev5 among m5 ( sci5ce4  
,x 0 ,gauss :o fir/ bas$ ! practical    
measurem5t ( magnetic =ce 7& !re=e ( e  
o!r =ce7 on ^? long e/abli%$ pr9ciples1 
:i*1 ?\gh !y are embodi$ 9 e dynamical  
equation1 h be5 s g5]ally set aside1 t  
^! v equations1 ?\gh correctly giv5 9   
our ,cambridge textbooks1 are usually   
expla9$ !re by assum+1 9 addition to !  
v>iable /&>d ( =ce1 a v>iable1 & !re=e  
illegal1 /&>d ( mass4  ,su*1 !n1 7 "s ( 
! sci5tific results :i* foll[$ 9 ?is    
case f br++ toge!r ma!matical p[]1      
exp]im5tal sagacity1 & manipulative     

skill1 to direct & assi/ ! lab\rs ( a   
body ( zeal\s obs]v]s4  ,if !re=e we    
desire1 = our own advantage & = ! hon\r 
( our ,univ]sity1 t ! ,devon%ire        
,laboratory %\ld be successful1 we mu/  
endeav\r to ma9ta9 x 9 liv+ union ) !   
o!r organs & faculties ( our le>n$ body4
  ,we %all !re=e fir/ consid] ! relation
 9 :i* we /& to ^? ma!matical /udies :i*
 h s long fl\ri%$ among u1 :i* deal )   
our own subjects1 & :i* diff] f our     
exp]im5tal /udies only 9 ! mode 9 :i* !y
 are pres5t$ to ! m9d4  ,!re is no m    
p[]ful me?od = introduc+ k into ! m9d   
?an t ( pres5t+ x 9 z _m diff]5t ways z 
we c4 ,:5 ! ideas1 aft] ent]+ ?r\gh     
diff]5t gateways1 effect a junction 9 ! 
citadel ( ! m9d1 ! position !y occupy   
becomes impregnable4  ,opticians tell u 
t ! m5tal comb9ation ( ! views ( an     
object :i* we obta9 f /ations no fur!r  
ap>t ?an our two eyes is suffici5t to   
produce 9 our m9ds an impression ( !    
solidity ( ! object se52 & we f9d t ?is 
impression is produc$ ev5 :5 we are aw>e

 t we are really look+ at two flat      
pictures plac$ 9 a /]eoscope4  ,x is    
!re=e natural to expect t ! k ( physical
 sci5ce obta9$ by ! comb9$ use (        
ma!matical analysis & exp]im5tal rese>* 
w be ( a m solid1 available1 & endur+   
k9d ?an t possess$ by ! m]e ma!matician 
or ! m]e exp]im5t]4  ,b :at w be !      
effect on ! ,univ]sity1 if m5 ,pursu+ t 
c\rse ( read+ :i* has produc$ s _m      
di/+ui%$ ,wrangl]s1 turn aside to "w    
exp]im5ts8  ,w n _! att5dance at !      
,laboratory c\nt n m]ely z "t )drawn f  
_! m legitimate /udies1 b z !           
introduction ( a di/urb+ elem5t1 ta9t+  
_! ma!matical conceptions ) mat]ial     
imag]y1 & sapp+ _! fai? 9 ! =mulae ( !  
textbook8  ,besides ?is1 we h already   
he>d compla9ts ( ! undue ext5sion ( our 
/udies1 & ( ! /ra9 put ^u our que/ioni/s
 by ! weight ( le>n+ :i* !y try to c>ry 
) !m into ! ,s5ate-,h\se4  ,if we n[ ask
 !m to get up _! subjects n only by     
books & writ+1 b at ! same "t by        
obs]vation & manipulation1 w !y n break 

d[n altoge!r8  ,! ,physical ,laboratory1
 we are told1 may p]haps be useful to ^?
 :o are go+ out 9 ,natural ,sci5ce1 & :o
 d n take 9 ,ma!matics1 b to attempt to 
comb9e bo? k9ds ( /udy dur+ ! "t (      
resid5ce at ! ,univ]sity is m ?an "o m9d
 c be>4  ,no d\bt !re is "s reason = ?is
 feel+4  ,_m ( u h already ov]come !    
initial difficulties ( ma!matical tra9+4
 ,:5 we n[ g on ) our /udy1 we feel t x 
requires ex]tion & involves fatigue1 b  
we are confid5t t if we only "w h>d our 
progress w be c]ta94  ,"s ( u1 on ! o!r 
h&1 may h _h "s exp]i5ce ( ! r\t9e (    
exp]im5tal "w4  ,z soon z we c read     
scales1 obs]ve times1 focus telescopes1 
& s on1 ?is k9d ( "w ceases to require  
any great m5tal ef=t4  ,we may p]haps   
tire our eyes & we>y our backs1 b we d n
 greatly fatigue our m9ds4  ,x is n till
 we attempt to br+ ! !oretical "p ( our 
tra9+ into contact ) ! practical t we   
beg9 to exp]i5ce ! full effect ( :at    
,f>aday has call$ m5tal in]tia--n only !
 difficulty ( recognis+1 among !        

concrete objects be=e u1 ! ab/ract      
relation :i* we h le>n$ f books1 b !    
di/ract+ pa9 ( wr5*+ ! m9d away f !     
symbols to ! objects1 & f ! objects back
 to ! symbols4  ,?is h[ev] is ! price we
 h to pay = new ideas4  ,b :5 we h      
ov]come ^! difficulties1 & successfully 
bridg$ ov] ! gulph betwe5 ! ab/ract & ! 
concrete1 x is n a m]e piece ( k t we h 
obta9$3 we h acquir$ ! rudim5t ( a      
p]man5t m5tal end[m5t4  ,:51 by a       
repetition ( ef=ts ( ?is k9d1 we h m    
fully develop$ ! sci5tific faculty1 !   
ex]cise ( ?is faculty 9 detect+         
sci5tific pr9ciples 9 nature1 & 9       
direct+ practice by !ory1 is no long]   
irksome1 b becomes an unfail+ s\rce (   
enjoym5t1 to :i* we return s (t51 t at  
la/ ev5 our c>eless ?\ghts beg9 to run 9
 a sci5tific *annel4  ,i q admit t our  
m5tal en]gy is limit$ 9 quantity1 & ,i  
"k t _m zeal\s /ud5ts try to d m ?an is 
good = !m4 ,b ! "q ab\t ! introduction (
 exp]im5tal /udy is n entirely "o (     
quantity4  ,x is to a great ext5t a "q (

 di/ribution ( en]gy4  ,"s di/ributions 
( en]gy1 we "k1 are m useful ?an o!rs1  
because !y are m available = ^? purposes
 :i* we desire to accompli%4  ,n[ 9 !   
case ( /udy1 a great "p ( our fatigue   
(t5 arises1 n f ^? m5tal ef=ts by :i* we
 obta9 ! ma/]y ( ! subject1 b f ^? :i*  
are sp5t 9 recall+ our w&]+ ?\ghts2 & ^!
 ef=ts ( att5tion w\ld be mu* less      
fatigu+ if ! di/urb+ =ce ( m5tal        
di/raction c\ld be remov$4  ,?is is !   
reason :y a man ^: s\l is 9 8 "w always 
makes m progress ?an "o ^: aim is some?+
 n imm$iately connect$ ) 8 occupation4  
,9 ! latt] case ! v motive ( :i* he     
makes use to /imulate 8 flagg+ p[]s     
becomes ! means ( di/ract+ 8 m9d f ! "w 
be=e him4  ,!re may be "s ma!maticians  
:o pursue _! /udies entirely = _! own   
sake4  ,mo/ m51 h[ev]1 ?9k t ! *ief use 
( ma!matics is f\nd 9 ! int]pretation ( 
nature4  ,n[ a man :o /udies a piece (  
ma!matics 9 ord] to und]/& "s natural   
ph5om5on :i* he has se51 or to calculate
 ! be/ arrangem5t ( "s exp]im5t :i* he  

means to make1 is likely to meet ) f>   
less di/raction ( m9d ?an if 8 sole aim 
_h be5 to %>p5 8 m9d = ! successful     
practice ( ! ,law1 or to obta9 a high   
place 9 ! ,ma!matical ,tripos4  ,i h    
kn[n m51 :o :5 !y 7 at s*ool1 nev] c\ld 
see ! good ( ma!matics1 b :o1 :5 9 aft] 
life !y made ?is discov]y1 n only became
 em95t z sci5tific eng9e]s1 b made      
consid]able progress 9 ! /udy ( ab/ract 
ma!matics4  ,if our exp]im5tal c\rse    
%\ld help any ( y to see ! good (       
ma!matics1 x w relieve u ( mu* anxiety1 
= x w n only ensure ! success ( y\r     
future /udies1 b x w make x mu* less    
likely t !y w prove injuri\s to y\r     
heal?4   ,b :y %\ld we lab\r to prove ! 
advantage ( practical sci5ce to !       
,univ]sity8  ,let u r speak ( ! help :i*
 ! ,univ]sity may give to sci5ce1 :5 m5 
well tra9$ 9 ma!matics & enjoy+ !       
advantages ( a well-appo9t$ ,laboratory1
 %all unite _! ef=ts to c>ry out "s     
exp]im5tal rese>* :i* no solit>y work]  
c\ld attempt4  ,at fir/ x is probable t 

our pr9cipal exp]im5tal "w mu/ be !     
illu/ration ( p>ticul> bran*es ( sci5ce1
 b z we g on we mu/ add to ?is ! /udy ( 
sci5tific me?ods1 ! same me?od be+      
sometimes illu/rat$ by its application  
to rese>*es belong+ to diff]5t bran*es (
 sci5ce4  ,we might ev5 imag9e a c\rse (
 exp]im5tal /udy ! arrangem5t ( :i* %\ld
 be f\nd$ on a classification ( me?ods1 
& n on t ( ! objects ( inve/igation4  ,a
 comb9ation ( ! two plans seems to me   
bett] ?an ei!r1 & :ile we take e        
opportunity ( /udy+ me?ods1 we %all take
 c>e n to dissociate ! me?od f !        
sci5tific rese>* to :i* x is appli$1 &  
to :i* x owes its value4  ,we %all !re=e
 arrange our lectures accord+ to !      
classification ( ! pr9cipal natural     
ph5om5a1 su* z heat1 electricity1       
magnetism & s on4  ,9 ! laboratory1 on !
 o!r h&1 ! place ( ! diff]5t in/rum5ts w
 be det]m9$ by a classification accord+ 
to me?ods1 su* z weigh+ & measur+1      
obs]vations ( "t1 optical & electrical  
me?ods ( obs]vation1 & s on4  ,!        

det]m9ation ( ! exp]im5ts to be p]=m$ at
 a p>ticul> "t mu/ (t5 dep5d ^u ! means 
we h at comm&1 & 9 ! case ( ! m         
elaborate exp]im5ts1 ?is may imply a    
long "t ( prep>ation1 dur+ :i* !        
in/rum5ts1 ! me?ods1 & ! obs]v]s        
!mselves1 are be+ gradually fitt$ = _!  
"w4  ,:5 we h ?us br\ght toge!r !       
requisites1 bo? mat]ial & intellectual1 
= a p>ticul> exp]im5t1 x may sometimes  
be desirable t be=e ! in/rum5ts are     
dism\nt$ & ! obs]v]s disp]s$1 we %\ld   
make "s o!r exp]im5t1 requir+ ! same    
me?od1 b deal+ p]haps ) an entirely     
diff]5t class ( physical ph5om5a4  ,our 
pr9cipal "w1 h[ev]1 9 ! ,laboratory mu/ 
be to acqua9t ourselves ) all k9ds (    
sci5tific me?ods1 to comp>e !m1 & to    
e/imate _! value4  ,x w1 ,i ?9k1 be a   
result wor?y ( our ,univ]sity1 & m      
likely to be accompli%$ "h ?an 9 any    
private laboratory1 if1 by ! free & full
 discussion ( ! relative value ( diff]5t
 sci5tific proc$ures1 we succe$ 9 =m+ a 
s*ool ( sci5tific criticism1 & 9 assi/+ 

! developm5t ( ! doctr9e ( me?od4  ,b   
admitt+ t a practical acqua9tance ) !   
me?ods ( ,physical ,sci5ce is an        
ess5tial "p ( a ma!matical & sci5tific  
education1 we may be ask$ :e!r we are n 
attribut+ too mu* importance to sci5ce  
altoge!r z "p ( a lib]al education4     
,=tunately1 !re is no "q "h :e!r !      
,univ]sity %\ld cont9ue to be a place ( 
lib]al education1 or %\ld devote itself 
to prep>+ "y m5 = p>ticul> pr(essions4  
,h5ce ?\gh "s ( u may1 ,i hope1 see     
reason to make ! pursuit ( sci5ce ! ma9 
bus9ess ( our lives1 x mu/ be "o ( our  
mo/ con/ant aims to ma9ta9 a liv+       
connexion betwe5 our "w & ! o!r lib]al  
/udies ( ,cambridge1 :e!r lit]>y1       
philological1 hi/orical or              
philosophical4  ,!re is a n>r[          
pr(essional _s :i* may gr[ up among m5 (
 sci5ce1 j z x does among m5 :o practise
 any o!r special bus9ess4  ,b surely a  
,univ]sity is ! v place :]e we %\ld be  
able to ov]come ?is t5d5cy ( m5 to      
become1 z x 71 granulat$ into small     

worlds1 :i* are all ! m worldly = _! v  
smallness4  ,we lose ! advantage ( hav+ 
m5 ( v>i$ pursuits collect$ into "o     
body1 if we d n endeav\r to imbibe "s ( 
! _s ev5 ( ^? ^: special bran* ( le>n+  
is diff]5t f our own4  ,x is n s long   
ago s9ce any man :o devot$ himself to   
geometry1 or to any sci5ce requir+      
cont9u$ application1 0 look$ ^u z       
necess>ily a misan?rope1 :o mu/ h ab&on$
 all human int]e/s1 & betak5 himself to 
ab/ractions s f> remov$ f ! _w ( life & 
action t he has become ins5sible alike  
to ! attractions ( pleasure & to !      
claims ( duty4  ,9 ! pres5t day1 m5 (   
sci5ce are n look$ ^u ) ! same awe or ) 
! same suspicion4  ,!y are suppos$ to be
 9 league ) ! mat]ial _s ( ! age1 & to  
=m a k9d ( advanc$ ,radical p>ty among  
m5 ( le>n+4  ,we are n "h to def5d      
lit]>y & hi/orical /udies4  ,we admit t 
! prop] /udy ( mank9d is man4  ,b is !  
/ud5t ( sci5ce to be )drawn f ! /udy (  
man1 or cut (f f e noble feel+1 s long z
 he lives 9 intellectual fell[%ip ) m5  

:o h devot$ _! lives to ! discov]y (    
tru?1 & ! results ( ^: enquiries h      
impress$ !mselves on ! ord9>y spee* &   
way ( ?9k+ ( m5 :o nev] he>d _! names8  
,or is ! /ud5t ( hi/ory & ( man to omit 
f 8 consid]ation ! hi/ory ( ! orig9 &   
diffusion ( ^? ideas :i* h produc$ s    
great a diff]5ce betwe5 "o age ( ! _w & 
ano!r8  ,x is true t ! hi/ory ( sci5ce  
is v diff]5t f ! sci5ce ( hi/ory4  ,we  
are n /udy+ or attempt+ to /udy ! work+ 
( ^? bl9d =ces :i*1 we are told1 are    
op]at+ on cr[ds ( obscure p1 %ak+       
pr9cipalities & p[]s1 & compell+        
reasonable m5 to br+ ev5ts to pass 9 an 
ord] laid d[n by philosoph]s4  ,! m5 ^: 
names are f\nd 9 ! hi/ory ( sci5ce are n
 m]e hypo!tical con/itu5ts ( a cr[d1 to 
be reason$ ^u only 9 masses4  ,we       
recognise !m z m5 l ourselves1 & _!     
actions & ?\ghts1 be+ m free f !        
influ5ce ( passion1 & record$ m         
accurately ?an ^? ( o!r m51 are all !   
bett] mat]ials = ! /udy ( ! calm] p>ts (
 human nature4  ,b ! hi/ory ( sci5ce is 

n re/rict$ to ! enum]ation ( successful 
inve/igations4  ,x has to tell (        
unsuccessful inquiries1 & to expla9 :y  
"s ( ! able/ m5 h fail$ to f9d ! key (  
k1 & h[ ! reputation ( o!rs has only    
giv5 a firm] foot+ to ! errors into :i* 
!y fell4  ,! hi/ory ( ! developm5t1 :e!r
 normal or abnormal1 ( ideas is ( all   
subjects t 9 :i* we1 z ?9k+ m51 take !  
deepe/ int]e/4  ,b :5 ! action ( ! m9d  
passes out ( ! intellectual /age1 9 :i* 
tru? & error are ! alt]natives1 into ! m
 viol5tly emotional /ates ( ang] &      
passion1 malice & envy1 fury & madness2 
! /ud5t ( sci5ce1 ?\gh he is oblig$ to  
recognise ! p[]ful influ5ce :i* ^! wild 
=ces h ex]cis$ on mank9d1 is p]haps 9 "s
 measure disqualifi$ f pursu+ ! /udy (  
?is "p ( human nature4  ,b !n h[ few ( u
 are capable ( d]iv+ pr(it f su* /udies4
  ,we _c ent] into full sympa?y ) ^! l[]
 phases ( our nature )\t los+ "s ( t    
antipa?y to !m :i* is our sure/ safegu>d
 aga9/ a rev]sion to a mean] type1 & we 
gladly return to ! company ( ^?         

illu/ri\s m5 :o by aspir+ to noble ends1
 :e!r intellectual or practical1 h ris5 
above ! region ( /orms into a cle>]     
atmosph]e1 :]e !re is no                
misrepres5tation ( op9ion1 nor ambiguity
 ( expression1 b :]e "o m9d comes into  
close/ contact ) ano!r at ! po9t :]e bo?
 approa* ne>e/ to ! tru?4   ,i propose  
to lecture dur+ ?is t]m on ,heat1 &1 z  
our facilities = exp]im5tal "w are n yet
 fully develop$1 ,i %all endeav\r to    
place be=e y ! relative position &      
sci5tific connexion ( ! diff]5t bran*es 
( ! sci5ce1 r ?an to discuss ! details (
 exp]im5tal me?ods4  ,we %all beg9 )    
,!rmometry1 or ! regi/ration (          
temp]atures1 & ,calorimetry1 or !       
measurem5t ( quantities ( heat4  ,we    
%all !n g on to ,!rmodynamics1 :i*      
inve/igates ! relations betwe5 ! !rmal  
prop]ties ( bodies & _! o!r dynamical   
prop]ties1 9 s f> z ^! relations may be 
trac$ )\t any assumption z to ! p>ticul>
 con/itution ( ^! bodies4  ,! pr9ciples 
( ,!rmodynamics ?r[ great light on all !

 ph5om5a ( nature1 & x is probable t _m 
valuable applications ( ^! pr9ciples h  
yet to be made2 b we %all h to po9t out 
! limits ( ?is sci5ce1 & to %ew t _m    
problems 9 nature1 especially ^? 9 :i* !
 ,dissipation ( ,en]gy comes into play1 
are n capable ( solution by ! pr9ciples 
( ,!rmodynamics alone1 b t 9 ord] to    
und]/& !m1 we are oblig$ to =m "s m     
def9ite !ory ( ! con/itution ( bodies4  
,two !ories ( ! con/itution ( bodies h  
/ruggl$ = victory ) v>i\s =tunes s9ce ! 
e>lie/ ages ( speculation3 "o is ! !ory 
( a univ]sal pl5um1 ! o!r is t ( atoms &
 void4  ,! !ory ( ! pl5um is associat$ )
 ! doctr9e ( ma!matical cont9uity1 & its
 ma!matical me?ods are ^? ( !           
,diff]5tial ,calculus1 :i* is !         
appropriate expression ( ! relations (  
cont9u\s quantity4  ,! !ory ( atoms &   
void leads u to atta* m importance to ! 
doctr9es ( integral numb]s & def9ite    
proportions2 b1 9 apply+ dynamical      
pr9ciples to ! motion ( imm5se numb]s ( 
atoms1 ! limitation ( our faculties =ces

 u to ab&on ! attempt to express ! exact
 hi/ory ( ea* atom1 & to be cont5t )    
e/imat+ ! av]age condition ( a gr\p (   
atoms l>ge en\gh to be visible4  ,?is   
me?od ( deal+ ) gr\ps ( atoms1 :i* ,i   
may call ! /ati/ical me?od1 & :i* 9 !   
pres5t /ate ( our k is ! only available 
me?od ( /udy+ ! prop]ties ( real bodies1
 involves an ab&onm5t ( /rict dynamical 
pr9ciples1 & an adoption ( ! ma!matical 
me?ods belong+ to ! !ory ( probability4 
,x is probable t important results w be 
obta9$ by ! application ( ?is me?od1 :i*
 is z yet little kn[n & is n famili> to 
our m9ds4  ,if ! actual hi/ory ( ,sci5ce
 _h be5 diff]5t1 & if ! sci5tific       
doctr9es mo/ famili> to u _h be5 ^? :i* 
mu/ be express$ 9 ?is way1 x is possible
 t we might h consid]$ ! exi/5ce ( a    
c]ta9 k9d ( cont+5cy a self-evid5t tru?1
 & treat$ ! doctr9e ( philosophical     
necessity z a m]e sophism4  ,ab\t !     
beg9n+ ( ?is c5tury1 ! prop]ties (      
bodies 7 inve/igat$ by sev]al di/+ui%$  
,fr5* ma!maticians on ! hypo!sis t !y   

are sy/ems ( molecules 9 equilibrium4   
,! some:at unsatisfactory nature ( !    
results ( ^! inve/igations produc$1     
especially 9 ?is c\ntry1 a reaction 9   
fav\r ( ! opposite me?od ( treat+ bodies
 z if !y 71 s f> at lea/ z our exp]im5ts
 are conc]n$1 truly cont9u\s4  ,?is     
me?od1 9 ! h&s ( ,gre51 ,/okes1 & o!rs1 
has l$ to results1 ! value ( :i* does n 
at all dep5d on :at !ory we adopt z to !
 ultimate con/itution ( bodies4  ,"o v  
important result ( ! inve/igation ( !   
prop]ties ( bodies on ! hypo!sis t !y   
are truly cont9u\s is t x furni%es u ) a
 te/ by :i* we c asc]ta91 by exp]im5ts  
on a real body1 to :at degree ( t5uity x
 mu/ be r$uc$ be=e x beg9s to give      
evid5ce t its prop]ties are no long] !  
same z ^? ( ! body 9 mass4              
,inve/igations ( ?is k9d1 comb9$ ) a    
/udy ( v>i\s ph5om5a ( diffusion & (    
dissipation ( en]gy1 h rec5tly add$     
greatly to ! evid5ce 9 fav\r ( !        
hypo!sis t bodies are sy/ems ( molecules
 9 motion4  ,i hope to be able to lay   

be=e y 9 ! c\rse ( ! t]m "s ( ! evid5ce 
= ! exi/5ce ( molecules1 consid]$ z     
individual bodies hav+ def9ite          
prop]ties4  ,! molecule1 z x is pres5t$ 
to ! sci5tific imag9ation1 is a v       
diff]5t body f any ( ^? ) :i* exp]i5ce  
has hi!rto made u acqua9t$4  ,9 ! fir/  
place its mass1 & ! o!r con/ants :i*    
def9e its prop]ties1 are absolutely     
inv>iable2 ! individual molecule c nei!r
 gr[ nor decay1 b rema9s un*ang$ amid   
all ! *anges ( ! bodies ( :i* x may =m a
 con/itu5t4  ,9 ! second place x is n ! 
only molecule ( its k9d1 = !re are      
innum]able o!r molecules1 ^: con/ants   
are n approximately1 b absolutely       
id5tical ) ^? ( ! fir/ molecule1 & ?is  
:e!r !y are f\nd on ! e>?1 9 ! sun1 or 9
 ! fix$ />s4  ,by :at process (         
evolution ! philosoph]s ( ! future w    
attempt to acc\nt = ?is id5tity 9 !     
prop]ties ( su* a multitude ( bodies1   
ea* ( !m un*angeable 9 magnitude1 & "s (
 !m sep>at$ f o!rs by di/ances :i*      
,a/ronomy attempts 9 va9 to measure1 ,i 

_c conjecture4  ,my m9d is limit$ 9 its 
p[] ( speculation1 & ,i am =c$ to       
believe t ^! molecules mu/ h be5 made z 
!y are f ! beg9n+ ( _! exi/5ce4  ,i also
 conclude t s9ce none ( ! processes (   
nature1 dur+ _! v>i$ action on diff]5t  
individual molecules1 h produc$1 9 !    
c\rse ( ages1 ! slighte/ diff]5ce betwe5
 ! prop]ties ( "o molecule & ^? ( ano!r1
 ! hi/ory ( ^: comb9ations has be5      
diff]5t1 we _c ascribe ei!r _! exi/5ce  
or ! id5tity ( _! prop]ties to !        
op]ation ( any ( ^? causes :i* we call  
natural4  ,is x true !n t our sci5tific 
speculations h really p5etrat$ b5ea? !  
visible appe>ance ( ?+s1 :i* seem to be 
subject to g5]ation & corruption1 &     
rea*$ ! entrance ( t _w ( ord] &        
p]fection1 :i* cont9ues ?is day z x 0   
creat$1 p]fect 9 numb] & measure &      
weight8  ,we may be mi/ak54  ,no "o has 
z yet se5 or h&l$ an individual         
molecule1 & our molecul> hypo!sis may1 9
 its turn1 be supplant$ by "s new !ory (
 ! con/itution ( matt]2 b ! idea ( !    

exi/5ce ( unnumb]$ individual ?+s1 all  
alike & all un*angeable1 is "o :i* _c   
ent] ! human m9d & rema9 )\t fruit4  ,b 
:at if ^! molecules1 inde/ructible z !y 
are1 turn out to be n sub/ances         
!mselves1 b m]e affections ( "s o!r     
sub/ance8  ,accord+ to ,sir ,w4         
,?omson's !ory ( ,vortex ,atoms1 !      
sub/ance ( :i* ! molecule consi/s is a  
uni=mly d5se pl5um1 ! prop]ties ( :i*   
are ^? ( a p]fect fluid1 ! molecule     
itself be+ no?+ b a c]ta9 motion        
impress$ on a portion ( ?is fluid1 & ?is
 motion is %ewn1 by a !orem due to      
,helmholtz1 to be z inde/ructible z we  
believe a portion ( matt] to be4  ,if a 
!ory ( ?is k9d is true1 or ev5 if x is  
conceivable1 our idea ( matt] may h be5 
introduc$ into our m9ds ?r\gh our       
exp]i5ce ( ^? sy/ems ( vortices :i* we  
call bodies1 b :i* are n sub/ances1 b   
motions ( a sub/ance2 & yet ! idea :i*  
we h ?us acquir$ ( matt]1 z a sub/ance  
possess+ in]tia1 may be truly applicable
 to t fluid ( :i* ! vortices are !      

motion1 b ( ^: exi/5ce1 ap>t f !        
vortical motion ( "s ( its p>ts1 our    
exp]i5ce gives u no evid5ce :atev]4  ,x 
has be5 ass]t$ t metaphysical           
speculation is a ?+ ( ! pa/1 & t        
physical sci5ce has extirpat$ x4  ,!    
discussion ( ! categories ( exi/5ce1    
h[ev]1 does n appe> to be 9 dang] ( com+
 to an end 9 our "t1 & ! ex]cise (      
speculation cont9ues z fasc9at+ to e    
fre% m9d z x 0 9 ! days ( ,?ales4