,,h>p]',s ,,libr>y ( ,,liv+ ,,?\ght ,illu/ration3 ,,h>p]',s ,,libr>y ( ,,liv+ ,,?\ght ,wie ,alles si* zum ,ganz5 webt ,e9s 9 dem &]n wirkt und lebt6 ,,! ,,e!r ,,( ,,space ,,by ,,sir ,,oliv] ,,lodge1 ,f4,r4,s4 ,,h>p] ,,bro!rs ,,london ,,new ,,york ,illu/ration3 ,,fig4 #ae4 ,view ( ,e!r ma*9e complete & 9 action4 7,see ,*apt] ,v1 & figs4 #ab & #ac47 ,frontispiece ,,! ,,e!r ,,( ,,space ,,by ,,sir ,,oliv] ,,lodge1 ,f4,r4,s4 ,d4 ,sc4 ,lond41 ,hon4 ,d4 ,sc4 ,oxon4 et ,vict4 ,,ll4,d4 ,/4 ,&rews1 ,glasg[1 & ,ab]de5 ,vice-,presid5t ( ! ,in/itution ( ,electrical ,eng9e]s ,rum=d ,m$alli/ ( ! ,royal ,society ,ex-,presid5t ( ! ,physical ,society ( ,london ,late ,pr(essor ( ,physics 9 ! ,univ]sity ,college ( ,liv]pool ,honor>y ,memb] ( ! ,am]ican ,philosophical ,society ( ,philadelphia2 ( ! ,man*e/] ,philosophical ,society2 ( ! ,batavian ,society ( ,rott]dam2 & ( ! ,academy ( ,sci5ces ( ,bologna ,pr9cipal ( ! ,univ]sity ( ,birm+ham ,,illu/rat$ ,,london ,,& ,,new ,,york ,,h>p] ,,bro!rs #de ,,albem>le ,,/reet1 ,w4 #aiji ,copyright1 #aiji1 by ,h>p] ,bro!rs ,all rights res]v$ ,,preface ,inve/igation ( ! nature & prop]ties ( ! ,e!r ( ,space has long be5 = me ! mo/ fasc9at+ bran* ( ,physics1 & ,i welcome ! opportunity ( attempt+ to make g5]ally kn[n ! conclusions to :i* ,i h s f> be5 l$ on ?is great & p]haps inexhau/ible subject4 ,,oliv] ,,lodge4 ,,univ]sity ,,( ,,birm+ham1 ,m>*1 #aiji4 ,,to ,,! ,,f\nd]s ,,( ,,univ]sity ,,college1 ,,liv]pool1 ,,especially ,,to ,,^? ,,be>+ ,,! ,,names ,,( ,,ra?bone ,,& ,,( ,,holt ,,?is ,,book ,,is ,,inscrib$ ,,cont5ts ,,*apt] ,,page ,,introduction4 ,,g5]al ,,& ,,hi/orical xi ,i4 ,,! ,,lum9if]\s ,,e!r ,,& ,,! ,,mod]n ,,!ory ,,( ,,light #a ,,ii4 ,,! ,,int]/ell> ,,e!r ,,z ,a ,,connect+ ,,m$ium #ac ,,iii4 ,,influ5ce ,,( ,,motion ,,on ,,v>i\s ,,ph5om5a #bi ,,iv4 ,,exp]im5ts ,,on ,,! ,,e!r #dd ,v4 ,,special ,,exp]im5t ,,on ,,e!rial ,,viscosity #fg ,,vi4 ,,e!rial ,,d5sity #hj ,,vii4 ,,fur!r ,,explanations ,,conc]n+ ,,! ,,d5sity ,,& ,,en]gy ,,( ,,! ,,e!r #hg ,,viii4 ,,e!r ,,& ,,matt] #ih ,,ix4 ,,/r5g? ,,( ,,! ,,e!r #aae ,x4 ,,g5]al ,,!ory ,,( ,,ab]ration #abg ,,app5dix #a4 ,,on ,,gravity ,,& ,,e!rial ,,t5sion #adc ,,app5dix #b4 ,,calculations ,,9 ,,connexion ,,) ,,e!r ,,d5sity #adf ,,app5dix #c4 ,,fresnel',s ,,law ,a ,,special ,,case ,,( ,a ,,univ]sal ,,pot5tial ,,function #aeb ,,li/ ,,( ,,illu/rations ,,fig4 ,illu/rations ( ,ab]ration4 #a4 ,cannon %ots #ce #b4 ,boats or ,waves #cf #c4 ,ligh?\se beams #cg #d4 ,ray ?r\gh a mov+ /ratum #dj #e4 ,wave-fronts 9 mov+ m$ium #da #f4 ,normal reflexion 9 mov+ m$ium #dc ,exp]im5ts on ,e!r drift4 #g4 ,int]f]5ce ,kaleidoscope #ea #h4 ,hoek's exp]im5t #ec #i4 ,exp]im5t ( ,masc>t & ,jam9 #ed #aj4 ,diagram ( ,mi*elson's exp]im5t #fa ,illu/rations ( ,e!r ,ma*9e 7,lodge74 #aa4 ,diagram ( c\rse ( light #fi #ab4 ,g5]al view ( :irl+ "p ( ,e!r ,ma*9e #gb #ac4 ,g5]al view ( optical frame #gc #ad4 ,draw+ ( optical details #gd #ae4 ,view ( ,e!r ,ma*9e 9 action ,frontispiece #af4 ,appe>ance ( int]f]5ce b&s & micromet] wires #gf #ag4 ,iron mass = magnetisation #gg #ah4 ,appe>ance ( b&s #gf #ai4 ,arrangem5t = electrification #gh ,,introduction ,e!r or !r 7 probably f ,i burn17 a mat]ial sub/ance ( a m subtle k9d ?an visible bodies1 suppos$ to exi/ 9 ^? p>ts ( space :i* are app>5tly empty4 ,s beg9s ! article ,e!r1 writt5 = ! n9? edition ( ! ,encyclopdia ,britannica1 by ,james ,cl]k ,maxwell4 ,! d]ivation ( ! ^w seems to indicate "s connexion 9 m5's m9ds ) ! idea ( ,fire3 ! o!r ?ree elem5ts1 ,e>?1 ,wat]1 ,air1 repres5t+ ! solid1 liquid1 & gase\s conditions ( ord9>y matt] respectively4 ,! "n !r sugge/s a f> m subtle or p5etrat+ & ultra-mat]ial k9d ( sub/ance4 ,newton employs ! t]m = ! m$ium :i* fills space--n only space :i* appe>s to be empty1 b space also :i* appe>s to be full2 = ! lum9if]\s e!r mu/ und\bt$ly p5etrate betwe5 ! atoms--mu/ exi/ 9 ! pores s to speak--( e transp>5t sub/ance1 else light c\ld n travel ?r\gh x4 ,! foll[+ is an extract f ,newton's surmises conc]n+ ?is m$ium3-- ,qu4 #ah4 ,if 9 two l>ge tall cyl9drical ,vessels ( ,glass inv]t$1 two little ,!rmomet]s be susp5d$ s z n to t\* ! ,vessels1 & ! ,air be drawn out ( "o ( ^! ,vessels1 & ^! ,vessels ?us prep>$ be c>ri$ out ( a cold place into a w>m "o2 ! ,!rmomet] 9 vacuo w gr[ w>m z mu* & almo/ z soon z ! ,!rmomet] :i* is n 9 vacuo4 ,& :5 ! vessels are c>ri$ back into ! cold place1 ! ,!rmomet] 9 vacuo w gr[ cold almo/ z soon z ! o!r ,!rmomet]4 ,is n ! ,heat ( ! w>m ,room convey$ ?r\gh ! ,vacuum by ! ,vibrations ( a mu* subtil] ,m$ium ?an ,air1 :i* aft] ! ,air 0 drawn out rema9$ 9 ! ,vacuum8 ,& is n ?is ,m$ium ! same ) t ,m$ium by :i* ,light is transmitt$1 & by ^: ,vibrations ,light communicates ,heat to ,bodies8444 ,& d n ! ,vibrations ( ?is ,m$ium 9 hot ,bodies contribute to ! int5s5ess & duration ( _! ,heat8 ,& d n hot ,bodies communicate _! ,heat to contigu\s cold ones by ! ,vibrations ( ?is ,m$ium propagat$ f !m into ! cold ones8 ,& is n ?is ,m$ium exce$+ly m r>e & subtile ?an ! ,air1 & exce$+ly m ela/ic & active8 ,& do? x n readily p]vade all bodies8 ,& is x n 7by its ela/ic =ce7 exp&$ ?r\gh all ! ,heav5s8 ,qu4 #bb4 ,may n ,planets & ,comets1 & all gross ,bodies1 p]=m _! motions m freely1 & ) less resi/ance 9 ?is !real ,m$ium ?an 9 any ,fluid1 :i* fills all ,space adequately )\t leav+ any ,pores1 & by consequ5ce is mu* d5s] ?an ,quick-silv] & ,gold8 ,& may n its resi/ance be s small1 z to be inconsid]able8 ,= in/ance2 if ?is !r 7= s ,i w call x7 %\ld be suppos$ #gjjjjj times m ela/ic ?an our ,air1 & above #gjjjjj times m r>e2 its resi/ance w\ld be above #fjjjjjjjj times less ?an t ( ,wat]4 ,& s small a resi/ance w\ld sc>ce make any s5sible alt]ation 9 ! ,motions ( ! ,planets 9 t5 ?\s& ,ye>s4 ,t ! e!r1 if !re be su* a ?+ 9 space1 c pass readily into or ?r\gh matt] is (t5 held prov5 by tilt+ a m]cury b>omet]2 :5 ! m]cury rises to fill ! transp>5t vacuum4 ,ev]y?+ po9ts to its univ]sal p]meance1 if x exi/ at all4 ,b ^!1 aft] all1 are antique ?\ghts4 ,electric & ,magnetic in=mation has l$ u beyond !m into a region ( great] c]ta9ty & k2 s t n[ ,i am able to advocate a view ( ! ,e!r :i* makes x n only uni=mly pres5t & all-p]vad+1 b also massive & sub/antial beyond conception4 ,x is turn+ out to be by f> ! mo/ sub/antial ?+--p]haps ! only sub/antial ?+--9 ! mat]ial univ]se4 ,comp>$ to e!r ! d5se/ matt]1 su* z lead or gold1 is a filmy gossam] /ructure2 l a comet's tail or a milky way1 or l a salt 9 v dilute solution4 ,to lead up to & ju/ify ! idea ( ! reality & sub/antiality1 & va/ ?\gh z yet l>gely unrecognis$ importance1 ( ! ,e!r ( ,space1 ! foll[+ *apt]s h be5 writt54 ,"s ( !m repres5t ! exp&$ notes ( lectures :i* h be5 giv5 9 v>i\s places--*iefly ! ,royal ,in/itution2 :ile ! fir/ *apt] repres5ts a lecture be=e ! ,a%molean ,society ( ! ,univ]sity ( ,ox=d 9 ,june1 #ahhi4 ,"o *apt] 7viz4 ,*ap4 ,,ii7 has already be5 pr9t$ z "p ( an app5dix to ! ?ird edition ( ,mod]n ,views ( ,electricity1 z well z 9 ! ,=tnightly & ,nor? ,am]ican ,reviews2 b no o!r *apt]s h yet be5 publi%$1 ?\gh p>ts appe> 9 m elaborate =m 9 ,proce$+s or ,transactions ( le>n$ societies4 ,! problem ( ! con/itution ( ! ,e!r1 & ( ! way 9 :i* portions ( x are modifi$ to =m ! atoms or o!r con/itu5t units ( ord9>y matt]1 has n yet be5 solv$4 ,mu* "w has be5 done 9 ?is direction by v>i\s ma!maticians1 b mu* m rema9s to be done4 ,& until x is done1 "s scepticism is reasonable--p]haps laudable4 ,mean:ile !re are few physici/s :o w diss5t f ,cl]k ,maxwell's p5ultimate s5t5ce 9 ! article ,e!r ( :i* ! beg9n+ has already be5 quot$3-- ,:atev] difficulties we may h 9 =m+ a consi/5t idea ( ! con/itution ( ! !r1 !re c be no d\bt t ! int]planet>y & int]/ell> spaces are n empty1 b are occupi$ by a mat]ial sub/ance or body1 :i* is c]ta9ly ! l>ge/1 & probably ! mo/ uni=m body ( :i* we h any k4 ,,! ,,e!r ,,( ,,space ,,*apt] ,i ,,! ,,lum9if]\s ,,e!r ,,& ,,! ,,mod]n ,,!ory ,,( ,,light ,! olde/ & be/ kn[n function = an e!r is ! conveyance ( light1 & h5ce ! "n lum9if]\s 0 appli$ to x2 ?\gh at ! pres5t day _m m functions are kn[n1 & m w almo/ c]ta9ly be discov]$4 ,to beg9 ) x is be/ to le>n :at we c1 conc]n+ ! prop]ties ( ! ,int]/ell> ,e!r1 f ! ph5om5a ( ,light4 ,= n[ wellnigh a c5tury we h _h a wave !ory ( light2 & a wave !ory ( light is q c]ta9ly true4 ,x is directly demon/rable t light consi/s ( waves ( "s k9d or o!r1 & t ^! waves travel at a c]ta9 well-kn[n velocity1--a*iev+ a di/ance equal to sev5 times ! circumf]5ce ( ! e>? e second2 f ,new ,york to ,london & back 9 ! ?irtie? "p ( a second2 & tak+ only eight m9utes on ! j\rney f ! sun to ! e>?4 ,?is propagation 9 "t ( an undulatory di/urbance necess>ily involves a m$ium4 ,if waves sett+ out f ! sun exi/ 9 space eight m9utes be=e /rik+ our eyes1 !re mu/ necess>ily be 9 space "s m$ium 9 :i* !y exi/ & :i* conveys !m4 ,waves we _c h1 unless !y be waves 9 some?+4 ,no ord9>y matt] is compet5t to transmit waves at any?+ l ! spe$ ( light3 ! rate at :i* matt] conveys waves is ! velocity ( s\nd1--a spe$ comp>able to "o-million? ( ! spe$ ( light4 ,h5ce ! lum9if]\s m$ium mu/ be a special k9d ( sub/ance2 & x is call$ ! e!r4 ,! lum9if]\s e!r x us$ to be call$1 because ! conveyance ( light 0 all x 0 !n kn[n to be capable (2 b n[ t x is kn[n to d a v>iety ( o!r ?+s also1 ! qualify+ adjective may be dropp$4 ,b1 inasmu* z ! t]m 'e!r' is also appli$ to a famili> organic comp\nd1 we may di/+ui% ! ultra-mat]ial lum9if]\s m$ium by call+ x ! ,e!r ( ,space4 ,wave-motion 9 e!r1 light c]ta9ly is2 b :at does "o mean by ! t]m wave8 ,! popul> notion is1 ,i suppose1 ( some?+ heav+ up & d[n1 or p]haps ( some?+ break+ on a %ore4 ,b if y ask a ma!matician :at he means by a wave1 he w probably reply t ! mo/ g5]al wave is su* a function ( x & y & t z to satisfy ! diff]5tial equation dy_/dt v dy_/dx2 :ile ! simple/ wave is y a s9 7x-vt74 ,& he might possibly refuse to give any o!r answ]4 ,& 9 refus+ to give any o!r answ] ?an ?is1 or its equival5t 9 ord9>y words1 he is entirely ju/ifi$2 t is :at is meant by ! t]m wave1 & no?+ less g5]al w\ld be all-inclusive4 ,translat$ into ord9>y ,engli% ! phrase signifies1 ) accuracy & compreh5sive complet5ess1 ! full details ( a di/urbance p]iodic bo? 9 space & "t4 ,any?+ ?us d\bly p]iodic is a wave2 & all waves--:e!r 9 air z s\nd waves1 or 9 e!r z light waves1 or on ! surface ( wat] z ocean waves--c be compreh5d$ 9 ! def9ition4 ,:at prop]ties are ess5tial to a m$ium capable ( transmitt+ wave-motion8 ,r\ghly we may say two3 ela/icity & in]tia4 ,ela/icity 9 "s =m1 or "s equival5t ( x1--9 ord] to be able to /ore up en]gy & effect recoil2 in]tia1--9 ord] to enable ! di/urb$ sub/ance to ov]%oot ! m>k & oscillate beyond its place ( equilibrium to & fro4 ,any m$ium possess+ ^! two prop]ties c transmit waves1 & unless a m$ium possesses ^! prop]ties 9 "s =m or o!r1 or "s equival5t = !m1 x may be said ) mod]ate security to be incompet5t to transmit waves4 ,b if we make ?is latt] /atem5t "o mu/ be prep>$ to ext5d to ! t]ms ela/icity & in]tia _! v l>ge/ & broade/ signification1 s z to include any possible k9d ( re/or+ =ce1 & any possible k9d ( p]si/5ce ( motion1 respectively4 ,^! matt]s may be illu/rat$ 9 _m ways1 b p]haps a simple load$ la?1 or spr+1 9 a vice w s]ve well en\gh4 ,pull x to "o side1 & its ela/icity t5ds to make x recoil2 let x g1 & its in]tia causes x to ov]%oot its normal position4 ,t is :at in]tia is1--p[] ( ov]%oot+ a m>k1 or1 m accurately1 p[] ( mov+ = a "t ev5 aga9/ driv+ =ce1--p[] to ru% uphill4 ,bo? causes toge!r make x sw+ to & fro till its en]gy is exhau/$4 ,?is is a di/urbance simply p]iodic 9 "t4 ,a regul> s]ies ( su* spr+s1 set at equal int]vals & />t$ vibrat+ at regul> int]vals ( "t "o aft] ! o!r1 w\ld be p]iodic 9 space too2 & s !y w\ld1 9 disconnect$ fa%ion1 typify a wave4 ,a s]ies ( p5dulums w d j z well1 & if set sw++ 9 ord]ly fa%ion w furni% at once an example & an appe>ance ( wave motion1 :i* ! mo/ casual obs]v] mu/ recognise z su*4 ,! r[ ( spr+s obvi\sly possesses ela/icity & in]tia2 & any wave-transmitt+ m$ium mu/ simil>ly possess "s =m ( ela/icity & "s =m ( in]tia4 ,b n[ proce$ to ask :at is ?is ,e!r :i* 9 ! case ( light is ?us vibrat+8 ,:at corresponds to ! ela/ic displacem5t & recoil ( ! spr+ or p5dulum8 ,:at corresponds to ! in]tia :]eby x ov]%oots its m>k8 ,d we "k ^! prop]ties 9 ! e!r 9 any o!r way8 ,! answ]1 giv5 fir/ by ,cl]k ,maxwell1 & n[ reit]at$ & insi/$ on by exp]im5ts p]=m$ 9 e important laboratory 9 ! _w1 is3-- ,! ela/ic displacem5t corresponds to electro/atic *>ge1--r\ghly speak+1 to electricity4 ,! in]tia corresponds to magnetism4 ,?is is ! basis ( ! mod]n electromagnetic !ory ( light4 ,let me attempt to illu/rate ! mean+ ( ?is /atem5t1 by review+ "s fundam5tal electrical facts 9 ! light ( ^! analogies3-- ,! old & famili> op]ation ( *>g+ a ,leyd5 j>--! /or+ up ( en]gy 9 a /ra9$ dielectric--any electro/atic *>g+ :atev] is q analog\s to ! draw+ aside ( our flexible spr+4 ,x is mak+ use ( ! ela/icity ( ! e!r to produce a t5d5cy to recoil4 ,lett+ g ! spr+ is analog\s to p]mitt+ a dis*>ge ( ! j>--p]mitt+ ! /ra9$ dielectric to recov] itself--! electro/atic di/urbance to subside4 ,9 ne>ly all ! exp]im5ts ( electro/atics e!rial ela/icity is manife/4 ,next consid] in]tia4 ,h[ w\ld "o illu/rate ! fact t wat]1 = in/ance1 possesses in]tia--! p[] ( p]si/+ 9 motion aga9/ ob/acles--! p[] ( possess+ k9etic en]gy8 ,! mo/ direct way w\ld be1 to take a /ream ( wat] & try sudd5ly to /op x4 ,op5 a wat] tap freely & !n sudd5ly %ut x4 ,! impetus or mom5tum ( ! /opp$ wat] makes itself manife/ by a viol5t %ock to ! pipe1 ) :i* ev]ybody mu/ be famili>4 ,?is mom5tum ( wat] is utilis$ by eng9e]s 9 ! wat]-ram4 ,a precisely analog\s exp]im5t 9 ,electricity is :at ,f>aday call$ ! extra curr5t4 ,s5d a curr5t ?r\gh a coil ( wire r\nd a piece ( iron1 or take any o!r arrangem5t = develop+ p[]ful magnetism1 & !n sudd5ly /op ! curr5t by break+ ! circuit4 ,a viol5t fla% occurs1 if ! /oppage is sudd5 en\gh1 a fla% :i* means ! bur/+ ( ! insulat+ air p>tition by ! accumulat$ electromagnetic mom5tum4 ,! sci5tific "n = ?is electrical in]tia is self-induction4 ,briefly we may say t ne>ly all electromagnetic exp]im5ts illu/rate ! fact ( e!rial in]tia4 ,n[ return to consid] :at happ5s :5 a *>g$ conductor 7say a ,leyd5 j>7 is dis*>g$4 ,! recoil ( ! /ra9$ dielectric causes a curr5t1 ! in]tia ( ?is curr5t causes x to ov]%oot ! m>k1 & = an in/ant ! *>ge ( ! j> is rev]s$2 ! curr5t n[ fl[s backw>ds & *>ges ! j> up z at fir/2 back aga9 fl[s ! curr5t2 & s on1 *>g+ & rev]s+ ! *>ge1 ) rapid oscillations1 until ! en]gy is all dissipat$ into heat4 ,! op]ation is precisely analog\s to ! release ( a /ra9$ spr+1 or to ! pluck+ ( a /ret*$ /r+4 ,b ! dis*>g+ body1 ?us ?r[n into /rong electrical vibration1 is imb$d$ 9 ! all-p]vad+ e!r2 & we h j se5 t ! e!r possesses ! two prop]ties requisite = ! g5]ation & transmission ( waves1 viz43 ela/icity1 & in]tia or d5sity2 h5ce j z a tun+ =k vibrat+ 9 air excites arial waves1 or s\nd1 s a dis*>g+ ,leyd5 j> 9 e!r excites e!rial waves1 or light4 ,e!rial waves c !re=e be actually produc$ by direct electrical means4 ,i dis*>ge "h a j>1 & ! room is = an in/ant fill$ ) light4 ,) light1 ,i say1 ?\gh y c see no?+4 ,y c see & he> ! sp>k inde$--b t is a m]e second>y di/urbance we c = ! pres5t ignore--,i d n mean any second>y di/urbance4 ,i mean ! true e!rial waves emitt$ by ! electric oscillation go+ on 9 ! neighb\rhood ( ! recoil+ dielectric4 ,y pull aside ! prong ( a tun+ =k & let x g3 vibration foll[s & s\nd is produc$4 ,y *>ge a ,leyd5 j> & let x dis*>ge3 vibration foll[s & light is excit$4 ,x is light1 j z good z any o!r light4 ,x travels at ! same pace1 x is reflect$ & refract$ accord+ to ! same laws2 e exp]im5t kn[n to optics c be p]=m$ ) ?is e!rial radiation electrically produc$1--& yet y _c see x4 ,:y n8 ,= no fault ( ! light1 ! fault 7if !re be a fault7 is 9 ! eye4 ,! ret9a is incompet5t to respond to ^! vibrations--!y are too sl[4 ,! vibrations set up :5 ?is l>ge j> is dis*>g$ are f a hundr$ ?\s& to a million p] second1 b t is too sl[ = ! ret9a4 ,x responds only to vibrations betwe5 #djj billion & #gjj billion p] second4 ,! vibrations are too quick = ! e>1 :i* responds only to vibrations betwe5 #dj & #dj1jjj p] second4 ,betwe5 ! highe/ audible & ! l[e/ visible vibrations !re has be5 hi!rto a great gap1 :i* ^! electric oscillations g f> to fill up4 ,!re has be5 a great gap simply because we h no int]m$iate s5se organ to detect rates ( vibration betwe5 #dj1jjj & #djj1jjj1jjj1jjj1jjj p] second4 ,x 0 !re=e an unexplor$ t]ritory4 ,waves h be5 !re all ! "t 9 any quantity1 b we h n ?\ght ab\t !m nor att5d$ to !m4 ,x happ5s t ,i h myself succe$$ 9 gett+ electric oscillations s sl[ z to be audible1--! l[e/ ,i _h got 9 #ahhi 7 #abe p] second1 & = "s way above ?is ! sp>ks emit a musical note2 b no "o has yet succe$$ 9 directly mak+ electric oscillations :i* are visible1--?\gh indirectly e "o does x :5 !y light a c&le4 ,x is easy1 h[ev]1 to h an electric oscillator :i* vibrates #cjj million times a second1 & emits e!rial waves a y>d long4 ,! :ole range ( vibrations betwe5 musical tones & "s ?\s& million p] second1 is n[ fill$ up4 ,) ! l>ge cond5s]s & self-inductances employ$ 9 mod]n cable telegraphy1 x is easy to get a s]ies ( beautifully regul> & gradually damp$ electric oscillations1 ) a p]iod ( two or ?ree seconds1 record$ by an ord9>y signall+ in/rum5t or siphon record]4 ,^! electromagnetic waves 9 space h be5 kn[n on ! side ( !ory ev] s9ce #ahfe1 b int]e/ 9 !m 0 imm5sely quick5$ by ! discov]y ( a receiv] or detector = !m4 ,! great ?\gh simple discov]y by ,h]tz1 9 #ahhh1 ( an electric eye1 z ,"l ,kelv9 call$ x1 made exp]im5ts on ^! waves = ! fir/ "t easy or ev5 possible4 ,f t "t onw>d we possess$ a sort ( artificial s5se organ = _! appreciation1--an electric arrangem5t :i* c virtually see ^! int]m$iate rates ( vibration4 ,s9ce !n ,branly discov]$ t metallic p[d] c\ld be us$ z an extraord9>ily s5sitive detector2 & on ! basis ( ?is discov]y1 ! 'coh]]' 0 employ$ by me = di/ant signall+ by means ( electric or e!ric waves2 until n[ :5 _m o!r detectors are available 9 ! v>i\s sy/ems ( wireless telegraphy4 ,) ^! ,h]tzian waves all mann] ( optical exp]im5ts c be p]=m$4 ,!y c be reflect$ by pla9 %eets ( metal1 conc5trat$ by p>abolic reflectors1 refract$ by prisms1 & conc5trat$ by l5ses4 ,i h made1 = in/ance1 a l>ge l5s ( pit*1 weigh+ ov] ?ree hundr$weight1 = conc5trat+ !m to a focus4#a ,!y c be made to %[ ! ph5om5on ( int]f]5ce1 & ?us h _! wave-l5g? accurately measur$4 ,!y are /opp$ by all conductors1 & transmitt$ by all insulators4 ,metals are opaque2 b ev5 imp]fect insulators1 su* z wood or /one1 are /rik+ly transp>5t2 & waves may be receiv$ 9 "o room f a s\rce 9 ano!r1 ! door betwe5 ! two be+ %ut4 ,! real nature ( metallic opacity & ( transp>5cy has long be5 cle> 9 ,maxwell's !ory ( light1 & ^! electrically produc$ waves only illu/rate & br+ home ! well-kn[n facts4 ,! exp]im5ts ( ,h]tz are1 9 fact1 ! apo!osis ( ,maxwell's !ory4 99 99 99 99 99 ,?us1 !n1 9 e way1 ,cl]k ,maxwell's brilliant p]ception or ma!matical d$uction1 9 #ahfe1 ( ! real nature ( light is abundantly ju/ifi$2 & = ! fir/ "t we h a true !ory ( light1--no long] bas$ ^u analogy ) s\nd1 nor ^u ! suppos$ prop]ties ( "s hypo!tical jelly or ela/ic solid1 b capable ( be+ treat$ ^u a sub/antial basis ( its own1 9 alliance ) ! sci5ces ( ,electricity & ( ,magnetism4 ,light is an electromagnetic di/urbance ( ! e!r4 ,optics is a bran* ( electricity4 ,out/&+ problems 9 optics are be+ rapidly solv$1 n[ t we h ! means ( def9itely excit+ light ) a full p]ception ( :at we are do+1 & ( ! precise mode ( its vibration4 ,x rema9s to f9d out h[ to %ort5 d[n ! waves--to hurry up ! vibration until ! light becomes visible4 ,no?+ is want$ b quick] modes ( vibration4 ,small] oscillators mu/ be us$--v mu* small]--oscillators n mu* bigg] ?an molecules4 ,9 all probability--"o may almo/ say c]ta9ly--ord9>y light is ! result ( electric oscillation 9 ! molecules or atoms ( hot bodies1 or sometimes ( bodies n hot--z 9 ! ph5om5on ( phosphoresc5ce4 ,! direct g5]ation ( visible light by electric means1 s soon z we h le>nt h[ to atta9 ! necess>y frequ5cy ( vibration1 w h mo/ important practical consequ5ces2 & t matt] is initially dealt ) 9 a section on ! ,manufacture ( ,light1 #adi1 9 ,*apt] ,,xiv ( ,mod]n ,views ( ,electricity4 ,b "h we ab&on fur!r consid]ation ( ?is aspect ( our great subject4 ,,footnote3 #a ,see ,lodge & ,h[>d1 ,philosophical ,magaz9e = ,july1 #ahhi4 ,see also ,phil4 ,mag41 ,augu/1 #ahhh1 page #bbi4 ,,*apt] ,,ii ,,! ,,int]/ell> ,,e!r ,,z ,a ,,connect+ ,,m$ium ,s f> ,i h giv5 a g5]al idea ( ! pres5t condition ( ! wave !ory ( light1 bo? f its !oretical & f its exp]im5tal sides4 ,! waves ( light are n any?+ me*anical or mat]ial1 b are some?+ electrical & magnetic--!y are 9 fact electrical di/urbances p]iodic 9 space & "t1 & travell+ ) a kn[n & trem5d\s spe$ ?r\gh ! e!r ( space4 ,_! v exi/5ce dep5ds ^u ! e!r1 & _! spe$ ( propagation is its be/ kn[n & mo/ c]ta9 quantitative prop]ty4 ,a /atem5t ( ?is k9d does n ev5 initially express a ti! ( our k on ! subject2 nor does our k exhau/ any l>ge "p ( ! region ( discov]able fact2 b ! /atem5t above made may be reg>d$ z c]ta91 al?\gh ! abs5ce ( me*anics or ord9>y dynamics ab\t x removes x1 or seems to remove x1 f ! category ( ! hi/orically s\nde/ & be/ work$ dep>tm5t ( ,physical ,sci5ce1 viz4 t explor$ by ! ,newtonian me?od4 ,?\gh 9 tru? !re is e reason to suppose t we %\ld h _h ,newton ) u 9 ^! mod]n developm5ts4 ,!re is1 ,i believe1 a g5]al t5d5cy to und]rate ! c]ta9ty ( "s ( ! convictions to :i* natural philosoph]s h gradually1 9 ! c\rse ( _! /udy ( nature1 be5 impell$2 m especially :5 ^? convictions h ref]5ce to some?+ intangible & occult4 ,! exi/5ce ( a cont9u\s space-fill+ m$ium1 = in/ance1 is probably reg>d$ by mo/ educat$ p z a m or less fanciful hypo!sis1 a figm5t ( ! sci5tific imag9ation1--a mode ( collat+ & weld+ toge!r a c]ta9 numb] ( obs]v$ facts1 b n 9 any physical s5se a reality1 z wat] & air are realities4 ,i am speak+ purely physically4 ,!re may be ano!r po9t ( view f :i* all mat]ial reality c be d5i$1 b ) ^? que/ions physics prop] has no?+ to d2 x accepts ! evid5ce ( ! s5ses1 reg>d+ !m z ! tools or in/rum5ts :]e) man may hope to und]/& "o def9ite aspect ( ! univ]se2 & x leaves to philosoph]s1 equipp$ f a diff]5t arm\ry1 ! o!r aspects :i* ! mat]ial univ]se may--nay1 mu/--possess4 ,by a physical explanation is meant a cle> /atem5t ( a fact or law 9 t]ms ( some?+ ) :i* daily life has made u famili>4 ,we are all *iefly famili>1 f our y\? up1 ) two app>5tly simple ?+s1 motion & =ce4 ,we h a direct s5se = bo? ^! ?+s4 ,we d n und]/& !m 9 any deep way1 probably we d n und]/& !m at all1 b we are accu/om$ to !m4 ,motion & =ce are our prim>y objects ( exp]i5ce & consci\sness2 & 9 t]ms ( !m all o!r less famili> occurr5ces may conceivably be /at$ & grasp$4 ,:5ev] a ?+ c be s cle>ly & def9itely /at$1 x is said to be expla9$1 or und]/ood2 we are said to h a dynamical !ory ( x4 ,any?+ %ort ( ?is may be a provisional or p>tial !ory1 an explanation ( ! less kn[n 9 t]ms ( ! m kn[n1 b ,motion & ,=ce are po/ulat$ 9 physics z ! completely kn[n3 & no attempt is made to press ! t]ms ( an explanation fur!r ?an t4 ,a dynamical !ory is recognis$ z be+ at once necess>y & suffici5t4 ,n[1 x mu/ be admitt$ at once t ( v few ?+s h we at pres5t su* a dynamical explanation4 ,we h no su* explanation ( matt]1 = in/ance1 or ( gravitation1 or ( electricity1 or e!r1 or light4 ,x is always conceivable t ( "s su* ?+s no purely dynamical explanation w ev] be =?com+1 because some?+ m ?an motion & =ce may p]haps be ess5tially involv$4 ,/ill1 physics is b\nd to pu% ! se>* = an explanation to its fur!/ limits2 & s long z x does n hoodw9k itself by vagu5ess & m]e phrases--a feebl5ess aga9/ :i* its lead]s are mightily & sometimes cruelly on _! gu>d1 pref]r+ to risk ! rejection ( wor?y ideas r ?an p]mit a semi-acceptance ( any?+ fanciful & obscure--s long z x vigor\sly probes all ph5om5a )9 its rea*1 seek+ to r$uce ! physical aspect ( !m to t]ms ( motion & =ce1--s long x mu/ be ^u a safe track4 ,&1 by its failure to deal ) c]ta9 ph5om5a1 x w le>n--x already beg9s to suspect1 its lead]s mu/ long h surmis$--! exi/5ce ( "s ?ird1 z yet unkn[n1 category1 by incorporat+ :i* ! physics ( ! future may rise to high] flights & an enl>g$ scope4 ,i h said t ! ?+s ( :i* we are p]man5tly consci\s are motion & =ce1 b !re is a ?ird ?+ :i* we h likewise be5 all our lives 9 contact )1 & :i* we "k ev5 m prim>ily1 ?\gh p]haps we are s imm]s$ 9 x t our k realises itself lat]1--viz4 life & m9d4 ,i d n n[ pret5d to def9e ^! t]ms1 or to speculate z to :e!r ! ?+s !y d5ote are ess5tially "o & n two4 ,!y exi/1 9 ! s5se 9 :i* we p]mit ourselves to use t ^w1 & !y are n yet incorporat$ into physics4 ,till !y are1 !y may rema9 m or less vague2 b h[ or :5 !y c be incorporat$1 is n = me ev5 to conjecture4 ,/ill1 x is op5 to a physici/ to /ate h[ ! univ]se appe>s to him1 9 its broad "* & physical aspect4 ,if ,i 7 to make ! attempt ,i %\ld f9d x necess>y = ! sake ( cle>ness to beg9 ) ! simple/ & mo/ fundam5tal ideas2 9 ord] to illu/rate1 by facts & notions 9 univ]sal k1 ! k9d ( process :i* ess5tially occurs 9 connection ) ! =mation ( high] & less famili> conceptions1--9 regions :]e ! common in=mation ( ! race is s slight z to be useless4 ,prim>y ,acqua9tance ) ! ,ext]nal ,_w4 ,beg9n+ ) our mo/ fundam5tal s5se ,i %\ld sket* ! matt] ?us3-- ,we h muscles & c move4 ,i _c analyse motion1--,i d\bt if ! attempt is wise1--x is a simple imm$iate act ( p]ception1 a direct s5se ( free unresi/$ muscul> action4 ,we may inde$ move )\t feel+ x1 & t tea*es u no?+1 b we may move s z to feel x1 & ?is tea*es u mu*1 & leads to our fir/ sci5tific inf]5ce1 viz4 space2 t is1 simply1 room to move ab\t4 ,we might h _h a s5se ( be+ jamm$ into a full or tight-pack$ univ]se2 b we h n3 we feel x to be a spaci\s "o4 ,( c\rse we d n /op at ?is baldness ( inf]5ce3 our educat$ faculty leads u to realise ! exi/5ce ( space f> beyond ! possibility ( direct s5sation2 &1 fur!r1 by means ( ! direct appreciation ( spe$ 9 connection ) motion1--( uni=m & v>iable spe$1--we become able to =mulate ! idea ( "t1 or uni=mity ( sequ5ce2 & we atta9 o!r m complex notions--accel]ation & ! l--^u a consid]ation ( :i* we ne$ n n[ ent]4 ,b our muscul> s5se is n limit$ to ! p]ception ( free motion3 we con/antly f9d x re/rict$ or =cibly resi/$4 ,?is muscul> action imp$$ is ano!r direct s5se1 t ( =ce2 & attempts to analyse x into any?+ simpl] ?an itself h hi!rto result$ only 9 confusion4 ,by =ce is meant prim>ily muscul> action n accompani$ by motion4 ,our s5se ( ?is tea*es u t space1 ?\gh roomy1 is n empty3 x gives u our second sci5tific inf]5ce--:at we call matt]4 ,aga9 we d n /op at ?is b>e inf]5ce4 ,by ano!r s5se1 t ( pa91 or m]e s5sation1 we discrim9ate betwe5 masses ( matt] 9 app>5tly intimate relation ) ourselves1 & o!r or =eign lumps ( matt]2 & we use ! fir/ portion z a measure ( ! ext5t ( ! second4 ,! human body is our /&>d ( size4 ,we proce$ also to subdivide our idea ( matt]1--accord+ to ! v>ieties ( resi/ance ) :i* x appeals to our muscul> s5se1--into f\r diff]5t /ates1 or elem5ts z ! anci5ts call$ !m2 viz4 ! solid1 ! liquid1 ! gase\s1 & ! e!rial4 ,! resi/ance exp]i5c$ :5 we enc\nt] "o or o!r ( ^! =ms ( mat]ial exi/5ce v>ies f some?+ v impressive--! solid1--?r\gh some?+ ne>ly impalpable--! gase\s1--up to some?+ entirely imag9ative1 fanciful1 or inf]5tial1 viz4 ! e!r4 ,! e!r does n 9 any way affect our s5se ( t\* 7i4e4 ( =ce72 x does n resi/ motion 9 ! slighte/ degree4 ,n only c our bodies move ?r\gh x1 b mu* l>g] bodies1 planets & comets1 c ru% ?r\gh x at :at we are pleas$ to call a prodigi\s spe$ 7be+ f> great] ?an t ( an a?lete7 )\t %[+ ! lea/ sign ( friction4 ,i myself1 inde$1 h design$ & c>ri$ out a s]ies ( delicate exp]im5ts to see :e!r a :irl+ mass ( iron c\ld to ! smalle/ ext5t grip ! e!r & c>ry x r\nd1 ) s mu* z a ?\s&? "p ( its own velocity4 ,^! %all be describ$ fur!r on1 b mean:ile ! result arriv$ at is di/9ct4 ,! answ] is1 no2 ,i _c f9d a trace ( me*anical connection betwe5 matt] & e!r1 ( ! k9d kn[n z viscosity or friction4 ,:y1 !n1 if x is s impalpable1 %\ld we ass]t its exi/5ce8 ,may x n be a m]e fanciful speculation1 to be extrud$ f physics z soon z possible8 ,if we 7 limit$ = our k ( matt] to our s5se ( t\*1 ! "q w\ld nev] ev5 h pres5t$ itself2 we %\ld h be5 simply ignorant ( ! e!r1 z ignorant z we are ( any life or m9d 9 ! univ]se n associat$ ) "s k9d ( mat]ial body4 ,b our s5ses h atta9$ a high] /age ( developm5t ?an t4 ,we are consci\s ( matt] by means o!r ?an its resi/+ =ce4 ,matt] acts on "o small portion ( our body 9 a totally diff]5t way1 & we are said to ta/e x4 ,ev5 f a di/ance x is able to fl+ (f small p>ticles ( itself suffici5t to affect ano!r delicate s5se4 ,or aga91 if x is vibrat+ ) an appropriate frequ5cy1 ano!r "p ( our body responds2 & ! univ]se is discov]$ to be n sil5t b eloqu5t to ^? :o h e>s to he>4 ,are !re any m discov]ies to be made8 ,yes2 & already "s h be5 made4 ,all ! s5ses hi!rto m5tion$ speak to u ( ! pres5ce ( ord9>y matt]1--gross matt]1 z x is sometimes call$1--?\gh :5 appeal+ to our s5se ( smell1 & m especially to a dog's s5se ( smell1 x is n v gross2 /ill1 ) ! s5ses hi!rto enum]at$ we %\ld nev] h become aw>e ( ! e!r4 ,a /roke ( lightn+ might h smitt5 our bodies back into _! inorganic con/itu5ts1 or a torp$o-fi% might h inflict$ on u a /range k9d ( torm5t2 b f ^! viol5t tutors we %\ld h le>nt little m ?an a s*oolboy le>ns f ! once ev]-ready cane4 ,b x s happ5s t ! :ole surface ( our sk9 is s5sitive 9 yet ano!r way1 & a small portion ( x is a/\nd+ly & beautifully s5sitive1 to an impression ( an altoge!r diff]5t "*--"o n necess>ily associat$ ) any =m ( ord9>y matt]--"o t w occur equally well ?r\gh space f :i* all solid1 liquid1 or gase\s matt] has be5 remov$4 ,hold y\r h& ne> a fire1 put y\r face 9 ! sun%9e1 & :at is x y feel8 ,y are n[ consci\s ( some?+ n arriv+ by ord9>y matt] at all4 ,y are n[ z directly consci\s z y c be ( ! e!rial m$ium4 ,true ! process is n v direct4 ,y _c appreh5d ! e!r z y c matt]1 by t\*+ or ta/+ or ev5 smell+ x2 b ! process is analog\s to ! k9d ( p]ception we might get ( ord9>y matt] if we _h ! s5se ( he>+ alone4 ,x is some?+ ak9 to vibrations 9 ! e!r t our sk9 & our eyes feel4 ,x may be rightly ass]t$ t x is n ! e!rial di/urbances !mselves1 b o!r di/urbances excit$ by !m 9 our tissues1 t our heat n]ves feel2 & ! same ass]tion c be made = our m highly-develop$ & specialis$ sight n]ves4 ,all n]ves mu/ feel :at is occurr+ next door to !m1 & c directly feel no?+ else2 b ! radiation1 ! cause :i* excit$ ^! di/urbances1 travell$ ?r\gh ! e!r1--n ?r\gh any o!rwise kn[n mat]ial sub/ance4 ,x %\ld be a commonplace to rehe>se h[ we "k ?is4 ,briefly1 ?us3 ,radiation conspicu\sly comes to u f ! sun4 ,if any free or ord9>y matt] exi/s 9 ! int]v5+ space1 x mu/ be an exce$+ly r>e gas4 ,9 o!r words1 x mu/ consi/ ( scatt]$ p>ticles ( matt]1 "s big en\gh to be call$ lumps1 "s s small z to be m]ely atoms1 b ea* ) a consid]able gap betwe5 x & its neighb\r4 ,su* isolat$ p>ticles are absolutely incompet5t to transmit light4 ,&1 p>5!tically1 ,i may say t no =m ( ord9>y matt]1 solid1 liquid1 or gase\s1 is compet5t to transmit a ?+ travell+ ) ! spe$ & subject to ! kn[n laws ( light4 ,= ! conveyance ( radiation or light all ord9>y matt] is n only incompet5t1 b hopelessly & absurdly incompet5t4 ,if ?is radiation is a ?+ transmitt$ by any?+ at all1 x mu/ be by some?+ sui g5]is4 ,b x is transmitt$1--= x takes "t on ! j\rney1 travell+ at a well-kn[n & def9ite spe$2 & x is a quiv]+ or p]iodic di/urbance1 fall+ "u ! g5]al category ( wave-motion4 ,no?+ is m c]ta9 ?an t4 ,no physici/ disputes x4 ,newton himself1 :o is commonly & truly ass]t$ to h promulgat$ a rival !ory1 felt ! necessity ( an e!rial m$ium1 & knew t light consi/$ ess5tially ( waves4 ,sight4 ,a small digression "h1 to avoid any possible confusion due to ! fact t ,i h purposely associat$ toge!r temp]ature n]ves & sight n]ves4 ,!y are admitt$ly n ! same1 b !y are alike 9 ?is1 t !y bo? af=d evid5ce ( radiation2 &1 7 we bl9d1 we might /ill "k a good deal ab\t ! sun1 & if our temp]ature n]ves 7 imm5sely increas$ 9 delicacy 7n all ov]1 = t w\ld be m]ely pa9ful1 b 9 "s protect$ region71 we might ev5 le>n ab\t ! moon1 planets1 & />s4 ,9 fact1 an eye1 consi/+ ( a pupil 7pref]ably a l5s7 & a sunk5 cavity l9$ ) a surface s5sitive to heat1 c\ld readily be imag9$1 & might be some:at s+ul>ly effective4 ,x w\ld be m ?an a light record]1 x c\ld detect all ! e!rial quiv]+s caus$ by surr\nd+ objects1 & h5ce w\ld see p]fectly well 9 :at we call ! d>k4 ,b x w\ld probably see f> too mu* = conv5i5ce1 s9ce x w\ld necess>ily be affect$ by e k9d ( radiation 9 simple proportion to its en]gy2 unless1 inde$1 x 7 provid$ ) a supply ( scre5s ) suitably select$ absorb+ p[]s4 ,b :atev] might be ! advantage or disadvantage ( su* a s5se-organ1 we z yet d n possess "o4 ,our eye does n act by detect+ heat2 9 o!r words1 x is n affect$ by ! :ole range ( e!rial quiv]+s1 b only by a v m9ute & app>5tly insignificant portion4 ,x :olly ignores ! e!r waves ^: frequ5cy is comp>able ) t ( s\nd2 &1 = ?irty or =ty octaves above ?is1 no?+ ab\t u responds2 b high up1 9 a range ( vibration ( ! inconceivably high pit* ( f\r to sev5 hundr$ million million p] second--a range :i* extremely few accessible bodies are able to emit1 & :i* x requires "s k & skill artificially to produce--to ^? waves ! eye is acutely1 surpass+ly1 & mo/ intellig5tly s5sitive4 ,?is little fragm5t ( total radiation is 9 itself trivial & negligible4 ,7 x n = m51 & gl[-worms1 & a few o!r =ms ( life1 h>dly any ( x w\ld ev] occur1 on su* a mod]ate-siz$ lump ( matt] z ! e>?4 ,except = an occasional volcano1 or a fla% ( lightn+1 only gigantic bodies l ! sun & />s h en]gy en\gh to produce ^! high] flute-l notes2 & !y d x by %e] ma9 =ce & viol5ce--! viol5ce ( _! gravitative en]gy--produc+ n only ^!1 b e o!r k9d ( radiation also4 ,gl[-worms1 s f> z ,i "k1 alone h le>nt ! secret ( emitt+ ! physiologically useful waves1 & none o!rs4 ,:y ^! waves are physiologically useful--:y !y are :at is call$ light1 :ile o!r k9ds ( radiation are d>k1 is a "q to be ask$1 b1 at pres5t1 only t5tatively answ]$4 ,! answ] mu/ ultimately be giv5 by ! ,physiologi/2 = ! di/9ction betwe5 light & non-light c only be /at$ 9 t]ms ( ! eye1 & its peculi> specialis$ s5sitiv5ess2 b a h9t may be giv5 him by ! ,physici/4 ,! e!rial waves :i* affect ! eye & ! photographic plate are ( a size n :olly incomp>able ) t ( ! atoms ( matt]4 ,:5 a physical ph5om5on is conc]n$ ) ! ultimate atoms ( matt]1 x is (t5 relegat$ at pres5t to ! field ( k summ>is$ "u ! head ( ,*emi/ry4 ,sight is probably a *emical s5se4 ,! ret9a may conta9 complex aggregations ( atoms1 %ak5 asund] by ! incid5t light vibrations1 & rapidly built up aga9 by ! liv+ tissues 9 :i* !y live2 ! n]ve-end+s mean:ile appreciat+ !m 9 _! tempor>ily dissociat$ condition4 ,a vague speculation6 ,n to be fur!r c\nt5anc$ except z a work+ hypo!sis lead+ to exam9ation ( fact2 b1 nev]!less1 ! direction 9 :i* ! ?\ghts ( "s physici/s are t5d+--a direction t[>ds :i* _m rec5tly discov]$ exp]im5tal facts po9t4#b ,gravitation & ,cohesion4 ,x w\ld take too long to d m ?an sugge/ "s o!r functions = :i* a cont9u\s m$ium ( communication is necess>y4 ,we %all argue 9 ,*apt] ,,viii t te*nical action at a di/ance is impossible4 ,a body c only act imm$iately on :at x is 9 contact )2 x mu/ be by ! action ( contigu\s p>ticles1--t is1 practically1 ?r\gh a cont9u\s m$ium1 t =ce c be transmitt$ across space4 ,radiation is n ! only ?+ ! e>? feels f ! sun2 !re is 9 addition its gigantic gravitative pull1 a =ce or t5sion m ?an :at a million million /eel rods1 ea* sev5te5 feet 9 diamet]1 c\ld /& 7see ,*ap4 ,,ix74 ,:at me*anism transmits ?is gigantic =ce8 ,aga91 take a /eel b> itself3 :5 viol5tly /ret*$1 ) h[ great t5acity its p>ts cl+ toge!r6 ,yet its p>ticles are n 9 absolute contact1 !y are only virtually atta*$ to ea* o!r by means ( ! univ]sal connect+ m$ium--! e!r1--a m$ium t mu/ be compet5t to transmit ! greate/ /resses :i* our k ( gravitation & ( cohesion %[s u to exi/4 ,electricity & ,magnetism4 ,hi!rto ,i h ma9ly conf9$ myself to ! p]ception ( ! e!r by our anci5t s5se ( radiation1 :]eby we detect its subtle & delicate quiv]+s4 ,b we are gr[+ a new s5se2 n p]haps an actual s5se-organ1 ?\gh n s v unlike a new s5se-organ1 ?\gh ! portions ( matt] :i* g to make ! organ are n associat$ ) our bodies by ! usual l9ks ( pa9 & disease2 !y are m analog\s to artificial tee? or me*anical limbs1 & c be b\ght at an in/rum5t-mak]'s4 ,electroscopes1 galvanomet]s1 telephones--delicate in/rum5ts ^!2 n yet eclips+ our s5se-organs ( fle%1 b 9 a few cases com+ )9 measurable di/ance ( _! surpris+ s5sitiv5ess4 ,& ) ^! :at d we d8 ,c we smell ! e!r1 or t\* x1 or :at is ! close/ analogy8 ,p]haps !re is no useful analogy2 b nev]!less we deal ) x1 & t closely4 ,n yet d we fully realise :at we are do+4 ,n yet h we any dynamical !ory ( electric curr5ts1 ( /atic *>ges1 & ( magnetism4 ,n yet1 inde$1 h we any dynamical !ory ( light4 ,9 fact1 ! e!r has n yet be5 br\ght "u ! doma9 ( simple me*anics--x has n yet be5 r$uc$ to motion & =ce3 & t probably because ! =ce aspect ( x has be5 s s+ul>ly elusive t x is a "q :e!r we ought to ?9k ( x z mat]ial at all4 ,no1 x is ap>t f me*anics at pres5t4 ,conceivably x may rema9 ap>t2 & our fir/ additional category1 :]e) ! f\ndations ( physics mu/ "s day be enl>g$1 may turn out to be an e!rial "o4 ,& "s su* inclusion may h to be made be=e we c attempt to annex vital or m5tal processes4 ,p]haps !y w all come 9 toge!r4 ,h[soev] ^! ?+s be1 ?is is ! k9d ( mean+ lurk+ 9 ! phrase t we d n yet "k :at electricity or :at ! e!r is4 ,we h z yet no dynamical explanation ( ei!r ( !m2 b ! pa/ c5tury has taught u :at seems to _! /ud5t an ov]:elm+ quantity ( facts ab\t !m4 ,& :5 ! pres5t c5tury1 or ! c5tury aft]1 lets u deep] into _! secrets1 & into ! secrets ( "s o!r ph5om5a n[ 9 c\rse ( be+ rationally inve/igat$1 ,i feel z if x w\ld be no m]ely mat]ial prospect t w be op5+ on our view1 b "s glimpse into a region ( ! univ]se :i* ,sci5ce has nev] ent]$ yet1 b :i* has be5 s\ght f f>1 & p]haps bl9dly appreh5d$1 by pa9t] & poet1 by philosoph] & sa9t4 ,note on ! ,spell+ ( ,e!real4 ,! usual ^w e!real sugge/s some?+ unsub/antial1 & is s us$ 9 poetry2 b = ! prosaic treatm5t ( ,physics x is unsuitable1 & e!ric has occasionally be5 us$ in/ead4 ,no j d]ivation c be giv5 = su* an adjective1 h[ev]2 & ,i h be5 accu/om$ simply to spell e!rial ) an i :5 no poetic mean+ 0 int5d$4 ,?is alt]native spell+ is n incorrect2 b ,milton uses ! v>iant e!re\s1 9 a s5se sugge/ive ( some?+ /rong & sub/antial 7,p>4 ,lo/1 vi1 #dgc74 ,ei!r ^w1 !re=e1 c be employ$ to replace e!real 9 physics3 & 9 succe$+ *apt]s "o or o!r ( ^! is = ! mo/ "p employ$4 ,,footnote3 #b ,cf4 sections #aeg;,a1 #adc1 #ahg1 & *ap4 xvi41 ( my ,mod]n ,views ( ,electricity4 ,,*apt] ,,iii ,,influ5ce ,,( ,,motion ,,on ,,v>i\s ,,ph5om5a ,not)/&+ its g5u9e physical nature & prop]ties1 ! e!r is s+ul>ly intangible & inaccessible to our s5ses1 & accord+ly is a subject on :i* x is extremely difficult to try exp]im5ts4 ,_m h be5 ! attempts to detect "s ph5om5a dep5d+ on its motion relative to ! e>?4 ,! e>? is travell+ r\nd ! sun at ! rate ( #ai miles a second1 & al?\gh ?is is sl[ comp>$ ) light--be+ 9 fact j ab\t #a_/aj1jjj? ( ! spe$ ( light1--yet x w\ld seem feasible to obs]ve "s modification ( optical ph5om5a due to ?is motion ?r\gh ! e!r4 ,& "o su* ph5om5on is inde$ kn[n1 namely1 ! /ell> ab]ration discov]$ by ,bradley 9 #agbi4 ,! position ( objects n on ! e>?1 & n connect$ ) ! sol> sy/em1 is app>5tly alt]$ by an am\nt comp>able to "o "p 9 t5 ?\s&1 by ! e>?'s motion2 t is to say1 ! app>5t place ( a /> is %ift$ f its true place by an angle #a_/aj1jjj? ( a radian1#c or ab\t #bj seconds ( arc4 ,?is is call$ ,a/ronomical ,ab]ration1 & is extremely well kn[n4 ,b a numb] ( o!r problems op5 out 9 connexion ) x1 & on ^! x is desirable to ent] into detail4 ,= if ! e!r is /ation>y :ile ! e>? is fly+ ?r\gh x--at a spe$ va/ly fa/] ?an any cannon ball1 z mu* fa/] ?an a cannon ball z an express tra9 is fa/] ?an a saunt] on foot--x is = all practical purposes ! same z if ! e>? 7 /ation>y & ! e!r /ream+ pa/ x ) ?is imm5se velocity1 9 ! opposite direction4 ,& "s consequ5ce ( su* a drift might at fir/ sight c]ta9ly be expect$4 ,x might1 = in/ance1 seem d\btful :e!r t]re/rial survey+ op]ations c be conduct$1 ) ! extreme accuracy expect$ ( !m1 )\t "s all[ance = ! viol5t ru% ( ! light-convey+ m$ium pa/ & ?r\gh ! !odolite ( ! obs]v]4 ,let u !re=e consid] ! :ole subject fur!r4 ,,ab]ration4 ,ev]ybody kn[s t to %oot a bird on ! w+ y mu/ aim 9 front ( x4 ,e "o w readily admit t to hit a squatt+ rabbit f a mov+ tra9 y mu/ aim beh9d x4 ,^! are examples ( :at may be call$ ab]ration f ! s5d]'s po9t ( view1 f ! po9t ( view ( ! s\rce4 ,& ! ab]ration1 or ne$ful div]g5ce betwe5 ! po9t aim$ at & ! ?+ hit has opposite sign 9 ! two cases--! case :5 receiv] is mov+1 & ! case :5 s\rce is mov+4 ,h5ce1 if bo? be mov+1 x is possible = ! two ab]rations to neutralise ea* o!r4 ,s to hit a rabbit runn+ alongside ! tra9 y mu/ aim /raight at x4 ,if !re 7 no air t is all simple en\gh4 ,b e rifleman kn[s to 8 co/ t ?\gh he fixes bo? himself & 8 t>get tightly to ! gr\nd1 s z to de/roy all ab]ration prop]1 yet a curr5t ( air is v compet5t to introduce a k9d ( spuri\s ab]ration ( its own1 :i* may be call$ w9dage2 & t he mu/ n aim at ! t>get if he wants to hit x1 b mu/ aim a little 9 ! eye ( ! w9d4 ,s mu* f ! %oot]'s po9t ( view4 ,n[ att5d to ! po9t ( view ( ! t>get4 ,consid] x made ( s(t en\gh mat]ial to be completely p5etrat$ by ! bullet1 leav+ a longi% hole :]ev] /ruck4 ,a p]son beh9d ! t>get1 :om we may call a m>k]1 by apply+ 8 eye to ! hole imm$iately aft] ! hit1 may be able to look ?r\gh x at ! %oot]1 & !reby to spot ! successful man4 ,i "k t ?is is n precisely ! function ( an ord9>y m>k]1 b x is m complete ?an 8 ord9>y function4 ,all he does usually is to signal an imp]sonal hit2 "s "o else has to record ! id5tity ( ! %oot]4 ,i am r assum+ a volley ( %ots1 & t ! m>k] has to allocate ! hits to _! respective s\rces by means ( ! holes made 9 ! t>get4 ,well1 w he d x correctly8 ,assum+1 ( c\rse1 t he c d s if ev]y?+ is /ation>y1 & ignor+ all curvature ( pa?1 :e!r v]tical or horizontal curvature4 ,if y ?9k x ov] y w p]ceive t a w9d w n prev5t 8 do+ x correctly2 ! l9e ( hole w po9t to ! %oot] along ! pa? ( 8 bullet1 ?\gh x w n po9t along 8 l9e ( aim4 ,also1 if ! %ots are fir$ f a mov+ %ip1 ! l9e ( hole 9 a /ation>y t>get w po9t to ! position ! gun occupi$ at ! in/ant ! %ot 0 fir$1 ?\gh x may h mov$ s9ce !n4 ,9 nei!r ( ^! cases 7mov+ m$ium & mov+ s\rce7 w !re be any error4 ,b if ! t>get is 9 motion1 on an arm\r$ tra9 = in/ance1 !n ! m>k] w be at fault4 ,! hole w n po9t to ! man :o fir$ ! %ot1 b to an individual ahead ( him4 ,! s\rce w appe> to be displac$ 9 ! direction ( ! obs]v]'s motion4 ,?is is common ab]ration4 ,x is ! simple/ ?+ 9 ! _w4 ,! easie/ illu/ration ( x is t :5 y run ?r\gh a v]tical %[]1 y tilt y\r umbrella =w>d2 or1 if y h n got "o1 ! drops hit y 9 ! face2 m accurately1 y\r face z y run =w>d hits ! drops4 ,s ! %[] appe>s to come f a cl\d ahead ( y1 in/ead ( f "o ov]head4 ,we h ?us ?ree motions to consid]1 t ( ! s\rce1 ( ! receiv]1 & ( ! m$ium2 &1 ( ^!1 only motion ( receiv] is able to cause an ab]rational error 9 fix+ ! position ( ! s\rce4 ,s f> we h att5d$ to ! case ( projectiles1 ) ! object ( lead+ up to light4 ,b light does n consi/ ( projectiles1 x consi/s ( waves2 & ) waves matt]s are a little diff]5t4 ,waves crawl ?r\gh a m$ium at _! own def9ite pace2 !y _c be flung =w>ds or sideways by a mov+ s\rce2 !y d n move by reason ( an initial mom5tum :i* !y are gradually exp5d+1 z %ots d2 _! motion is m analog\s to t ( a bird or o!r self-propell+ animal1 ?an x is to t ( a %ot4 ,! motion ( a wave 9 a mov+ m$ium may be lik5$ to t ( a r[+-boat on a riv]4 ,x crawls =w>d ) ! wat]1 & x drifts ) ! wat]2 its resultant motion is comp\nd$ ( ! two1 b x has no?+ to d ) ! motion ( its s\rce4 ,a %ot f a pass+ /eam] reta9s ! motion ( ! /eam] z well z t giv5 x by ! p[d]4 ,x is project$ !re=e 9 a slant direction4 ,b a boat l[]$ f ! side ( a pass+ /eam]1 & r[+ (f1 reta9s none ( ! motion ( its s\rce2 x is n project$1 x is self-propell$4 ,t is l ! case ( a wave4 ,! diagram illu/rates ! diff]5ce4 ,fig4 #a %[s a mov+ cannon or ma*9e-gun1 mov+ ) ! arr[1 & fir+ a succession ( %ots :i* %>e ! motion ( ! cannon z well z _! own1 & s travel slant4 ,! %ot fir$ f position #a has rea*$ ,a1 t fir$ f position #b has rea*$ ,b1 & t fir$ f position #c has rea*$ ,c1 by ! "t ! f\r? %ot is fir$ at ,d4 ,! l9e ,a ,b ,c ,d is a prolongation ( ! axis ( ! gun2 x is ! l9e ( aim1 b x is n ! l9e ( fire2 all ! %ots are travell+ aslant ?is l9e1 z %[n by ! arr[s4 ,!re are ?us two directions to be di/+ui%$4 ,!re is ! r[ ( successive %ots1 & !re is ! pa? ( any "o %ot4 ,^! two directions enclose an angle4 ,x may be call$ an ab]ration angle1 because x is due to ! motion ( ! s\rce1 b x ne$ n give rise to any ab]ration4 ,true direction may /ill be p]ceiv$ f ! po9t ( view ( ! receiv]4 ,to prove ?is let u att5d to :at is happ5+ at ! t>get4 ,! fir/ %ot is suppos$ to be ent]+ at ,a1 & if ! t>get is /ation>y w leave x at ,y4 ,a m>k] look+ along ,y ,a w see ! position :5ce ! %ot 0 fir$4 ,?is may be lik5$ to a /ation>y obs]v] look+ at a mov+ />4 ,he sees x :]e & z x 0 :5 ! light />t$ on its long j\rney4 ,he does n see its pres5t position1 b !re is no reason :y he %\ld4 ,he does n see its physical /ate or any?+ z x is n[4 ,he sees x z x 0 :5 x s5t ! in=mation :i* he has j receiv$4 ,!re is no ab]ration caus$ by motion ( s\rce4 ,illu/ration3 ,,fig4 #a4 ,%ots or ,di/urbances ) ,mom5tum f a ,mov+ ,gun4 ,b n[ let ! receiv] be mov+ at same pace z ! gun1 z :5 two grappl$ %ips are fir+ into ea* o!r4 ,! motion ( ! t>get c>ries ! po9t ,y =w>d1 & ! %ot ,a leaves x at ,z1 because ,z is c>ri$ to :]e ,y 04 ,s 9 t case ! m>k] look+ along ,z ,a w see ! gun1 n z x 0 :5 fir+1 b z x is at ! pres5t mom5t2 & he w see likewise ! r[ ( %ots mak+ /raight = him4 ,?is is l an obs]v] look+ at a t]re/rial object4 ,motion ( ! e>? does n di/urb ord9>y vision4 ,fig4 #b %[s z ne>ly ! same sort ( ?+ z possible = ! case ( emitt$ waves4 ,! tube is a s\rce emitt+ a succession ( di/urbances )\t mom5tum4 ,a ,b ,c ,d may be ?\ght ( z horizontally fly+ birds1 or z cre/s ( waves1 or z self-swimm+ torp$oes2 or !y may ev5 be ?\ght ( z bullets1 if ! gun /&s /ill e "t x fires1 & only moves betwe5 :iles4 ,illu/ration3 ,,fig4 #b4 ,waves or ,di/urbances )\t ,mom5tum f a ,mov+ ,s\rce4 ,! l9e ,a ,b ,c ,d is n[ nei!r ! l9e ( fire nor ! l9e ( aim3 x is simply ! locus ( di/urbances emitt$ f ! successive positions #a #b #c #d4 ,a /ation>y t>get w be p5etrat$ 9 ! direction ,a ,y1 & ?is l9e w po9t out ! correct position ( ! s\rce :5 ! receiv$ di/urbance />t$4 ,if ! t>get moves1 a di/urbance ent]+ at ,a may leave x at ,z1 or at any o!r po9t accord+ to its rate ( motion2 ! l9e ,z ,a does n po9t to ! orig9al position ( ! s\rce1 & s !re w be ab]ration :5 ! t>get moves4 ,o!rwise !re w\ld be none4 ,illu/ration3 ,,fig4 #c4 ,beam f a ,revolv+ ,ligh?\se4 ,n[ ,fig4 #b also repres5ts a p>allel beam ( light travell+ f a mov+ s\rce1 & ent]+ a telescope or ! eye ( an obs]v]4 ,! beam lies along ,a ,b ,c ,d1 b ?is is n ! direction ( vision4 ,! direction ( vision1 to a /ation>y obs]v]1 is det]m9$ n by ! locus ( successive waves1 b by ! pa? ( ea* wave4 ,a ray may be def9$ z ! pa? ( a labell$ di/urbance4 ,! l9e ( vision is ,y ,a #a1 & co9cides ) ! l9e ( aim2 :i* 9 ! projectile case 7,fig4 #a7 x did n4 ,! case ( a revolv+ ligh?\se1 emitt+ long p>allel beams ( light & br&i%+ !m rapidly r\nd1 is r int]e/+4 ,fig4 #c may assi/ ! ?9k+ out ( ?is case4 ,successive di/urbances ,a1 ,b1 ,c1 ,d1 lie along a spiral curve1 ! spiral ( ,ar*im$es2 & ?is is ! %ape ( ! beams1 z se5 illum9at+ ! du/ p>ticles1 ?\gh ! pit* ( ! spiral is too gigantic to be di/+ui%$ f a /raight l9e4 ,at fir/ sight x might seem z if an eye look+ along ^? curv$ beams w\ld see ! ligh?\se slightly out ( its true position2 b x is n s4 ,! true rays or actual pa?s ( ea* di/urbance are truly radial2 !y d n co9cide ) ! app>5t beam4 ,an eye look+ at ! s\rce w n look tang5tially along ! beam1 b w look along ,a ,s1 & w see ! s\rce 9 its true position4 ,x w\ld be o!rwise = ! case ( projectiles f a revolv+ turret4 ,?us1 nei!r translation ( /> nor rotation ( sun c affect direction4 ,!re is no ab]ration s long z ! receiv] is /ation>y4 ,b :at ab\t a w9d1 or /ream+ ( ! m$ium pa/ s\rce & receiv]1 bo? /ation>y8 ,look at ,fig4 #a aga94 ,suppose a r[ ( /ation>y cannon fir+ %ots1 :i* get bl[n by a cross w9d along ! slant #a ,a ,y 7neglect+ ! curvature ( pa? :i* w\ld really exi/73 /ill ! hole 9 ! t>get fixes ! gun's true position1 ! m>k] look+ along ,y ,a sees ! gun :i* fir$ ! %ot4 ,!re is no true deviation f ! po9t ( view ( ! receiv]1 provid$ ! drift is uni=m ev]y:]e1 al?\gh ! %ots are bl[n aside & ! t>get is n hit by ! p>ticul> gun aim$ at x4 ,) a mov+ cannon comb9$ ) an oppos+ w9d1 ,fig4 #a w\ld become v l ,fig4 #b4 7,n4,b4--,! actual case1 ev5 )\t complication ( sp9n+1 etc41 b m]ely ) ! curv$ pa? caus$ by /eady w9d-pressure1 is n s simple1 & !re w\ld really be an ab]ration or app>5t displacem5t ( ! s\rce t[>ds ! w9d's eye3 an app>5t exagg]ation ( ! effect ( w9d %[n 9 ! diagram47 ,9 ,fig4 #b ! result ( a w9d is mu* ! same1 ?\gh ! details are r diff]5t4 ,! m$ium is suppos$ to be drift+ d[nw>ds1 across ! field4 ,! s\rce may be tak5 z /ation>y at ,s4 ,! horizontal arr[s %[ ! direction ( waves 9 ! m$ium2 ! dott$ slant l9e %[s _! resultant direction4 ,a wave c5tre drifts f ,d to #a 9 ! same "t z ! di/urbance rea*es ,a1 travell+ d[n ! slant l9e ,d ,a4 ,! angle betwe5 dott$ & full l9es is ! angle betwe5 ray & wave-normal4 ,n[1 if ! motion ( ! m$ium inside ! receiv] is ! same z x is outside1 ! wave w pass /raight on along ! slant to ,z1 & ! true direction ( ! s\rce is fix$4 ,b if ! m$ium inside ! t>get or telescope is /ation>y1 ! wave w cease to drift z soon z x gets inside1 "u cov] z x 72 x w proce$ along ! pa? x has be5 really pursu+ 9 ! m$ium all ! "t1 & make its exit at ,y4 ,9 ?is latt] case--( diff]5t motion ( ! m$ium inside & outside ! telescope--! app>5t direction1 su* z ,y ,a1 is n ! true direction ( ! s\rce4 ,! ray is 9 fact b5t :]e x ent]s ! diff]5tly-mov+ m$ium 7z %[n 9 ,fig4 #d74 ,illu/ration3 ,,fig4 #d4 ,ray ?r\gh a ,mov+ ,/ratum4 ,a sl[] mov+ /ratum b5ds an oblique ray1 slant+ ) ! motion1 9 ! same direction z if x 7 a d5s] m$ium4 ,a quick] /ratum b5ds x oppositely4 ,if a m$ium is bo? d5s] & quick] mov+1 x is possible = ! two b5d+s to be equal & opposite1 & ?us = a ray to g on /raight4 ,p>5!tically ,i may say t ?is is precisely :at happ5s1 on ,fresnel's !ory1 d[n ! axis ( a wat]-fill$ telescope expos$ to ! g5]al t]re/rial e!r drift4 ,9 a mov+ m$ium waves d n advance 9 _! normal direction1 !y advance slantways4 ,! direction ( _! advance is prop]ly call$ a ray4 ,! ray does n co9cide ) ! wave-normal 9 a mov+ m$ium4 ,illu/ration3 ,,fig4 #e4 ,successive ,wave ,fronts 9 a ,mov+ ,m$ium4 ,all ?is is well %[n 9 ,fig4 #e4 ,s is a /ation>y s\rce emitt+ successive waves1 :i* drift z sph]es to ! "r4 ,! wave :i* has rea*$ ,m has its c5tre at ,c1 & ,c ,m is its normal2 b ! di/urbance1 ,m1 has really travell$ along ,s ,m1 :i* is !re=e ! ray4 ,x has advanc$ z a wave f ,s to ,p1 & has drift$ f ,p to ,m4 ,di/urbances subsequ5tly emitt$ are f\nd along ! ray1 precisely z 9 ,fig4 #b4 ,a /ation>y telescope receiv+ ! light w po9t /raight at ,s4 ,a mirror1 ,m1 int5d$ to reflect ! light /raight back mu/ be set normal to ! ray1 n tang5tial to ! wave front4 ,! diagram also equally repres5ts ! case ( a mov+ s\rce 9 a /ation>y m$ium4 ,! s\rce1 />t+ at ,c1 has mov$ to ,s1 emitt+ waves z x w5t2 :i* waves1 z emitt$1 spread out z simple sph]es f ! !n position ( s\rce z c5tre4 ,wave-normal & ray n[ co9cide3 ,s ,m is n a ray1 b only ! locus ( successive di/urbances4 ,a /ation>y telescope w\ld look n at ,s1 b along ,m ,c to a po9t :]e ! s\rce 0 :5 x emitt$ ! wave ,m2 a mov+ telescope1 if mov+ at same rate z s\rce1 w look at ,s4 ,h5ce ,s ,m is sometimes call$ ! app>5t ray4 ,! angle ,s ,m ,c is ! ab]ration angle1 :i* 9 ,*ap4 ,x we d5ote by 4 ,fig4 #f %[s normal reflexion = ! case ( a mov+ m$ium4 ,! mirror ,m reflects light receiv$ f ,s1 to a po9t ,s1--j 9 "t to cat* ! s\rce !re if t is mov+ ) ! m$ium4 ,p>5!tically ,i may say t ! "t tak5 on ! d\ble j\rney1 ,s ,m ,s1 :5 ! m$ium is mov+1 is n q ! same z ! d\ble j\rney ,s ,m ,s1 :5 all is /ation>y2 & t ?is is ! pr9ciple ( ,mi*elson's great exp]im5t2 :i* mu/ be ref]r$ to lat]4 ,illu/ration3 ,,fig4 #f4 ,normal ,reflexion 9 ,mov+ ,m$ium4 ,! angle ,m ,s ,x is ! angle 9 ! !ory ( ,mi*elson's exp]im5t describ$ 9 ,*apt] ,,iv4 ,! e!r /ream we speak ( is always to be consid]$ m]ely z "o relative to matt]4 ,absolute velocity ( matt] means velocity ?r\gh ! e!r--:i* is /ation>y4 ,if !re 7 no su* physical /&>d ( re/ z ! e!r--if all motion 7 relative to matt] alone--!n ! cont5tion ( ,cop]nicus & ,galileo w\ld h _h no real mean+4 ,,footnote3 #c ,radian is ! "n giv5 by ,pr(4 ,james ,?omson to a unit angle ( circul> measure1 an angle ^: arc equals its radius1 or ab\t #eg4 ,,*apt] ,,iv ,,exp]im5ts ,,on ,,! ,,e!r ,we h arriv$ at ?is3 t a uni=m e!r /ream all ?r\gh space causes no ab]ration1 no error 9 fix+ direction4 ,x bl[s ! waves along1 b x does n di/urb ! l9e ( vision4 ,/ell> ab]ration exi/s1 b x dep5ds on motion ( obs]v]1 & on motion ( obs]v] only4 ,e!rial motion has no effect ^u x2 & :5 ! obs]v] is /ation>y ) respect to object1 z he is :5 us+ a t]re/rial telescope1 !re is no ab]ration at all4 ,survey+ op]ations are n r5d]$ ! lea/ inaccurate by ! exi/5ce ( a univ]sal e!rial drift2 & !y !re=e af=d no means ( detect+ x4 ,b obs]ve t ev]y?+ dep5ds on ! e!r's motion be+ uni=m ev]y:]e1 inside z well z outside ! telescope1 & along ! :ole pa? ( ! ray4 ,if /ation>y any:]e x mu/ be /ation>y altoge!r3 !re mu/ be no b\nd>y betwe5 /ation>y & mov+ e!r1 no plane ( slip1 no quick] motion ev5 9 "s regions ?an 9 o!rs4 ,= 7ref]r+ back to ! rem>ks prec$+ ,fig4 #d7 if ! e!r 9 receiv] is /agnant :ile outside x is mov+1 a wave :i* has advanc$ & drift$ z f> z ! telescope w cease to drift z soon z x gets inside1 b w advance simply along ! wave-normal4 ,& 9 g5]al1 at ! b\nd>y ( any su* *ange ( motion a ray w be b5t1 & an obs]v] look+ along ! ray w see ! s\rce n 9 its true position1 n ev5 9 ! app>5t position appropriate to 8 own motion1 b lagg+ beh9d t position4 ,su* an ab]ration z ?is1 a lag or negative ab]ration1 has nev] yet be5 obs]v$2 b if !re is any slip betwe5 lay]s ( e!r1 if ! e>? c>ries any e!r ) x1 or if ! e!r1 be+ 9 motion at all1 is n equally 9 motion ev]y:]e ?r\gh\t e transp>5t sub/ance1 !n su* a lag or negative ab]ration mu/ occur1 9 precise proportion to ! am\nt ( ! c>riage ( e!r by mov+ bodies 7cf4 p4 #fa74 ,on ! o!r h&1 if ! e!r behaves z a p]fectly frictionless inviscid fluid1 or if = any o!r reason !re is no rub betwe5 x & mov+ matt]1 s t ! e>? c>ries no e!r ) x at all1 !n all rays w be /raight1 ab]ration w h its simple & well-kn[n value1 & we %all be liv+ 9 a virtual e!r /ream ( n9ete5 miles a second1 by reason ( ! orbital motion ( ! e>?4 ,x may be difficult to imag9e t a great mass l ! e>? c ru% at ?is trem5d\s pace ?r\gh a m$ium )\t di/urb+ x4 ,x is n possible = an ord9>y sph]e 9 an ord9>y fluid4 ,at ! surface ( su* a sph]e !re is a visc\s drag1 & a sp9n+ motion diffuses out !nce ?r\gh ! fluid1 s t ! en]gy ( ! mov+ body is gradually dissipat$4 ,! p]si/5ce ( t]re/rial & planet>y motions %[s t e!rial viscosity1 if exi/5t1 is small2 or at lea/ t ! am\nt ( en]gy ?us got rid ( is a v small fraction ( ! :ole4 ,b !re is no?+ to %[ t an appreciable lay] ( e!r may n adh]e to ! e>? & travel ) x1 ev5 ?\gh ! =ce act+ on x be b small4 ,?is1 !n1 is ! "q be=e u3-- ,does ! e>? drag "s e!r ) x8 or does x slip ?r\gh ! e!r ) p]fect fre$om8 7,nev] m9d ! e>?'s atmosph]e2 ! "p x plays is kn[n & n important47 ,9 o!r words1 is ! e!r :olly or p>tially /agnant ne> ! e>?1 or is x /ream+ pa/ u ) ! opposite ( ! full t]re/rial velocity ( n9ete5 miles a second8 ,surely if we are liv+ 9 an e!r /ream ( ?is rapidity we ought to be able to detect "s evid5ce ( its exi/5ce4#d ,x is n s easy a ?+ to detect z y w\ld imag9e4 ,we h se5 t x produces no deviation or error 9 direction4 ,nei!r does x cause any *ange ( col\r or ,doppl] effect2 t is1 no %ift ( l9es 9 spectrum4 ,no /eady w9d c affect pit*1 simply because x _c bl[ waves to y\r e> m quickly ?an !y are emitt$4 ,x hurries !m along1 b x l5g!ns !m 9 ! same proportion1 & ! result is t !y arrive at ! prop] frequ5cy4 ,! precise effects ( motion on pit* are summ>is$ 9 ! foll[+ table3-- ,*anges ( ,frequ5cy due to ,motion4 ,s\rce approa*+ %ort5s waves4 ,receiv] approa*+ alt]s relative velocity4 ,m$ium fl[+ alt]s bo? wave-l5g? & velocity 9 exactly comp5satory mann]4 99 99 99 99 99 ,:at o!r ph5om5a may possibly result f motion8 ,"h is a li/3-- ,ph5om5a result+ f ,motion4 7#a7 ,*ange or app>5t *ange 9 direction2 obs]v$ by telescope1 & call$ ab]ration4 7#b7 ,*ange or app>5t *ange 9 frequ5cy2 obs]v$ by spectroscope1 & call$ ,doppl] effect4 7#c7 ,*ange or app>5t *ange 9 "t ( j\rney2 obs]v$ by lag ( phase or %ift ( int]f]5ce fr+es4 7#d7 ,*ange or app>5t *ange 9 int5sity2 obs]v$ by en]gy receiv$ by !rmopile4 99 99 99 99 99 ,:at we h arriv$ at s f> is ! foll[+3-- ,motion ( ei!r s\rce or receiv] c alt] frequ5cy2 motion ( receiv] c alt] app>5t direction2 motion ( ! m$ium c d nei!r4 ,b ! "q mu/ be ask$1 c x n hurry a wave s z to make x arrive out ( phase ) ano!r wave arriv+ by a diff]5t pa?1 & ?us produce or modify int]f]5ce effects8 ,or aga91 may x n c>ry ! waves d[n /ream m pl5tifully ?an up /ream1 & ?us act on a pair ( !rmopiles1 arrang$ =e & aft at equal di/ances f a s\rce1 ) unequal int5sity8 ,& once m1 p]haps ! laws ( reflection & refraction 9 a mov+ m$ium are n ! same z !y are if x be at re/4 ,!n1 moreov]1 !re is d\ble refraction1 col\rs ( ?9 plates & ?ick plates1 pol>isation angle1 rotation ( ! plane ( pol>isation2 all sorts ( optical ph5om5a t ne$ consid]ation4 ,x may h to be admitt$1 p]haps1 t 9 empty space ! effect ( an e!r drift is difficult to detect1 b w n ! pres5ce ( d5se matt]--especially ! passage ?r\gh d5se transp>5t matt]--make ! detection easi]8 ,s a great numb] ( que/ions arise1 all ( :i* h be51 f "t to "t1 s]i\sly discuss$4 ,int]f]5ce4 ,z an in/ance ( su* discussion1 consid] ,no4 #c ( ! ph5om5a tabulat$ above4 ,i expect t e read] und]/&s int]f]5ce1 b ,i may j briefly say t two simil> sets ( waves int]f]e :5ev] & :]ev] ! cre/s ( "o set co9cide ) & oblit]ate ! tr\ghs ( ! o!r set4 ,light advances 9 any giv5 direction :5 cre/s 9 t direction are able to rema9 cre/s1 & tr\ghs to rema9 tr\ghs4 ,b if we contrive to split a beam ( light into two halves1 to s5d !m r\nd by diff]5t pa?s1 & make !m meet aga91 !re is no gu>antee t cre/ w meet cre/ & tr\gh tr\gh2 x may be j ! o!r way 9 "s places1 & :]ev] t opposition ( phase occurs !re1 !re w be local oblit]ation or int]f]5ce4 ,two reunit$ half-beams ( light may ?us produce local /ripes ( d>kness1 & ^! /ripes are call$ int]f]5ce b&s4 ,x is n to be suppos$ t !re is any de/ruction ( light1 or any dissipation ( en]gy3 x is m]ely a case ( r$i/ribution4 ,! bright p>ts are bright] j 9 proportion z ! d>k p>ts are d>k]4 ,! scre5 is illum9at$ 9 /ripes & no long] uni=mly1 b its total illum9ation is ! same z if !re 7 no int]f]5ce4 ,,projection ,,( ,,int]f]5ce ,,b&s4 ,x is n easy to project ^! int]f]5ce b&s on a scre5 s z to make !m visible to an audi5ce1--p>tly because ! b&s or /ripes ( d>kness are exce$+ly n>r[2 inde$ ,i _h n previ\sly se5 ! exp]im5t attempt$4 ,b by means ( :at ,i call an int]f]5ce kaleidoscope1 consi/+ ( two mirrors set at an angle ) a ?ird semi-transp>5t mirror betwe5 !m1 x is possible to get ! b&s rem>kably cle> & bright1 s t !y c readily be project$3 & ,i %[$ ^! at a lecture to ! ,royal ,in/itution ( ,great ,brita9 9 #ahib4 ,ea* mirror is m\nt$ on a tripod ) adju/able screw feet1 :i* /& on a ?ick iron slab1 :i* aga9 re/s on holl[ india-rubb] balls4 ,look+ d[n on ! mirrors ! plan is z 9 ! diagram ,fig4 #g1 :i* indicates suffici5tly ! geometry ( ! arrangem5t1 & %[s t ! two half-beams1 into :i* ! semi-transp>5t plate divides ! light1 w ea* travel r\nd ! same cont\r ,a ,b ,c 9 opposite directions1 & w !n reunite & travel toge!r t[>ds ! po9t ( ! arr[4 ,a p>allel beam f an electric lant]n1 :5 ?us treat$1 depicts bright & broad int]f]5ce b&s on a scre54 ,& ! arrangem5t is v little s5sitive to di/urbance1 because ! pa?s ( ! two halves ( ! beam are id5tical1 & because ( ! m\nt+4 ,a piece ( good glass c be int]pos$ )\t di/urbance1 & ! table c be /ruck a heavy bl[ )\t confus+ ! b&s4 ,illu/ration3 ,,fig4 #g4 ,plan ( ,int]f]5ce ,kaleidoscope ) ?ree mirrors4 ,! arr[-fea!r ray is bifurcat$ at ,a by a semi-transp>5t mirror ( ?9ly-silv]$ glass2 & ! two halves reunite along ! arr[-head aft] trav]s+ a triangul> cont\r ,a ,b ,c 9 opposite directions4 ,! simple geometrical relations :i* p]mit ?is are suffici5tly indicat$ 9 ! figure4 ,! arrangem5t w\ld suit ,fizeau's exp]im5t4 ,! only regul> & ord]ly way ( caus+ a %ift ( ! b&s is to accel]ate "o half ( ! beam & to ret>d ! o!r half1 by mov+ a transp>5t sub/ance along ! cont\r4 ,= in/ance1 let ! sides ( ! triangle ,a ,b ,c1 or "o ( !m1 consi/ ( a tube ( wat] 9 :i* a rapid /ream is ma9ta9$2 !n ! /ream has a *ance ( accel]at+ "o half ! beam1 & ret>d+ ! o!r half1 !reby %ift+ ! fr+es f _! normal position by a measurable am\nt4 ,?is is ! exp]im5t made 9 #ahei by ,fizeau4 7,app5dix #c47 ,n[ t mo/ int]e/+ & important1 & ,i ?9k n[ well-kn[n1 exp]im5t ( ,fizeau proves q simply & def9itely t if light be s5t along a /ream ( wat]1 travell+ inside ! wat] z a transp>5t m$ium1 x w g quick] ) ! curr5t ?an aga9/ x4 ,y may say t is only natural2 a w9d assi/s s\nd "o way & ret>ds x ! opposite way4 ,yes1 b !n s\nd travels 9 air2 & w9d is a bodily transf] ( air2 h5ce1 ( c\rse1 x gives ! s\nd a ride4 ,:]eas light does n really travel 9 wat]1 b always 9 e!r2 & x is by no means obvi\s :e!r a /ream ( wat] c help or h9d] x4 ,exp]im5t decides1 h[ev]1 & answ]s 9 ! affirmative4 ,x helps x along ) j ab\t half ! spe$ ( ! wat]2 n ) ! :ole spe$1 :i* is curi\s & important1 & really means t ! mov+ wat] has no effect :atev] on ! e!r ( space1 ?\gh we mu/ def] expla9+ h[ ?is comes ab\t4 ,suffice = pres5t purposes ! fact t ! velocity ( light inside mov+ wat]1 & !re=e presumably inside all transp>5t matt]1 is alt]$ to "s ext5t by motion ( t matt]4 ,illu/ration3 ,,fig4 #h4 ,hoek's arrangem5t4 ,! light f s\rce ,s is reflect$ s z to travel half ?r\gh /agnant wat] & half ?r\gh air on its direct j\rney1 ! pa? be+ inv]t$ on ! return j\rney1 aft] :i* x ent]s ! eye4 ,does n ?is fact af=d an easy way ( detect+ a motion ( ! e>? ?r\gh ! e!r8 ,e vessel ( /agnant wat] is really travell+ along ?r\gh ! e!r at ! rate ( n9ete5 miles a second4 ,s5d a beam ( light ?r\gh x "o way1 & x w be hurri$2 its velocity1 in/ead ( be+ #adj1jjj miles a second1 w be #adj1jji miles4 ,s5d a beam ( light ! o!r way1 & its velocity w be #aci1iia2 j z mu* less4 ,br+ ^! two beams toge!r2 surely "s ( _! wave-l5g?s w int]f]e4 ,m4 ,hoek1 ,a/ronom] at ,utre*t1 tri$ ! exp]im5t 9 ?is v =m2 "h is a diagram ( 8 app>atus 7,fig4 #h74 ,bab9et _h tri$ ano!r =m ( ! exp]im5t previ\sly4 ,hoek expect$ to see int]f]5ce b&s1 f ! two half-beams :i* _h trav]s$ ! wat]1 "o 9 ! direction ( ! e>?'s motion & ! o!r aga9/ x4 ,b no int]f]5ce b&s 7 se54 ,! exp]im5t gave a negative result4 ,illu/ration3 ,,fig4 #i4 ,arrangem5t ( ,masc>t & ,jam94 ,a modification ( ,fig4 #h1 ) ! beam split def9itely into two halves by reflexion f a ?ick glass plate & reunit$ be=e obs]vation4 ,! two half-beams g ?r\gh /agnant wat] 9 opposite directions4 ,an exp]im5t1 h[ev]1 9 :i* no?+ is se5 is nev] a v satisfactory =m ( a negative exp]im5t2 x is1 z ,masc>t calls x1 d\bly negative1 & we require "s gu>antee t ! conditions 7 "r = see+ :at might really h be5 9 "s sort !re4 ,h5ce ,masc>t & ,jam9's modification ( ! exp]im5t is pref]able 7,fig4 #i74 ,! ?+ n[ look$ = is a %ift ( already exi/+ int]f]5ce b&s1 :5 ! above app>atus is turn$ s z to h diff]5t aspects ) respect to ! e>?'s motion2 b no %ift 0 se54 ,int]f]5ce me?ods all fail to display any trace ( relative motion betwe5 e>? & e!r4 ,try o!r ph5om5a !n4 ,try refraction4 ,! index ( refraction ( glass is kn[n to dep5d on ! ratio ( ! spe$ ( light outside1 to ! spe$ inside1 ! glass4 ,if !n ! e!r be /ream+ ?r\gh glass1 ! velocity ( light w be diff]5t inside accord+ z x travels ) ! /ream or aga9/ x1 & s ! index ( refraction may be diff]5t4 ,arago 0 ! fir/ to try ?is exp]im5t by plac+ an a*romatic prism 9 front ( a telescope on a mural circle1 & obs]v+ ! deviation x produc$ on />s4 ,obs]ve t x 0 an a*romatic prism1 treat+ all wave-l5g?s alike2 he look$ at ! deviat$ image ( a />1 n at its disp]s$ image or spectrum1--else he might h detect$ ! *ange-(-frequ5cy-effect due to motion ( s\rce or receiv] fir/ actually se5 by ,sir ,w4 ,hugg9s4 ,i d n ?9k ,arago w\ld h se5 x1 because ,i d n suppose 8 arrangem5ts 7 delicate en\gh = t v small effect2 b !re is no error 9 ! conception ( 8 exp]im5t1 z ,pr(4 ,masc>t has inadv]t5tly sugge/$ !re 04 ,!n ,maxwell repeat$ ! attempt 9 a mu* m p[]ful mann]1 a me?od :i* c\ld h detect$ a v m9ute effect inde$1 & ,masc>t has also repeat$ x 9 a simple =m4 ,all are absolutely negative4 ,well1 !n1 :at ab\t ab]ration8 ,if "o looks ?r\gh a mov+ /ratum1 say a sp9n+ glass disk1 !re ought to be a %ift caus$ by ! motion 7see ,fig4 #d74 ,t p>ticul> exp]im5t has n be5 tri$1 b ,i ent]ta9 no d\bt ab\t its result1 ?\gh a high spe$ & consid]able ?ickness ( glass or o!r m$ium w\ld be necess>y to produce ev5 a microscopic app>5t displacem5t ( objects se5 ?r\gh x4 ,b ! spe$ ( ! e>? is available1 & ! :ole l5g? ( a telescope tube may be fill$ ) wat]2 surely t is en\gh to displace rays ( light appreciably4 ,sir ,george ,airy tri$ x at ,gre5wi* on a />1 ) an appropriate z5i?-sector full ( wat]4 ,/>s 7 se5 ?r\gh ! wat]-telescope precisely z ?r\gh an air telescope4 ,a negative result aga96 7,! !ory is fully dealt ) 9 ,*apt] ,x & ,app5dix #c47 ,/ell> obs]vations1 h[ev]1 are unnecess>ily difficult4 ,fresnel _h po9t$ out t a t]re/rial s\rce ( light w\ld d j z well4 ,he _h also 7be+ a man ( exce$+ g5ius7 pr$ict$ t no?+ w\ld happ54 ,hoek has n[ tri$ x 9 a p]fect mann] & no?+ did happ54 ,b ^! facts are n at all disconc]t+2 !y are j :at ought to be anticipat$1 9 ! light ( true !ory4 ,! abs5ce ( all effect caus$ by /agnant d5se matt] ins]t$ 9 ! pa? ( a beam ( light1 t is ( d5se transp>5t matt] n artificially mov$ ) ref]5ce to ! e>?--or r ) ref]5ce to s\rce & receiv]--is explicable on ,fresnel's !ory conc]n+ ! behavi\r ( e!r inside matt]4 ,if ! index ( refraction ( ! matt] is call$ 1 t means t ! spe$ ( light inside x is #a_/? ( ! spe$ outside or 9 vacuo4 ,& t is only ano!r way ( say+ t ! virtual e!rial d5sity inside x is repres5t$ by 1 s9ce ! velocity ( waves is inv]sely z ! squ>e root ( ! d5sity ( ! m$ium :i* conveys !m2--! ela/icity be+ reckon$ z con/ant1 & ! same inside z out4 ,b !n if ! e!r is incompressible its d5sity mu/ really be con/ant1--s h[ c x be d5s] inside matt] ?an x is outside8 ,! answ] is t presumably ! e!r is n really extra d5se1 b is1 z x 71 load$ by ! matt]4 ,! atoms ( matt]1 or ! con/itu5t electrons1 mu/ be presum$ to be %ak5 by ! passage ( ! waves ( light1 z !y obvi\sly are 9 fluoresc5t sub/ances2 & accord+ly ! spe$ ( propagation w be less5$ by ! extra load+ :i* ! waves enc\nt]4 ,x is n a real increase ( d5sity1 b a virtual increase1 :i* is really due to ! addition ( a c]ta9 fraction ( mat]ial in]tia to ! in]tia ( ! e!r itself4 ,! d5sity ( e!r outside be+ #a1 & t ( ! load$ e!r inside be+ 1 ! effect ( ! load is expressible z -#a1 :ile ! free e!r is ! same inside z out4 ,suppose n[ t ! matt] is mov$ along4 ,! extra load+1 be+ "p ( ! matt]1 ( c\rse travels ) x1 & !reby affects ! spe$ ( light to ! ext5t ( ! load1--t is to say1 by an am\nt proportional to -#a z contra/$ ) 4 ,?is is ,fresnel's pr$ict$ ratio 7-#a73 1 or #a-a_/2 & 9 ,fizeau's exp]im5t ) runn+ wat]--especially z repeat$ lat]1 ) mod]n accuracy1 by ,mi*elson--?is repres5ts exactly ! am\nt ( obs]v$ effect ^u ! light4 ,b if1 in/ead ( runn+ wat]1 /agnant wat] is us$--t is /ation>y ) respect to ! e>?1 ?\gh /ill mov+ viol5tly ?r\gh ! e!r--!n ! 7-#a7 effect ( ! load w be fix$ to ! matt]1 & c produce no extra or motile effect4 ,! only "p t c\ld produce an effect ( t k9d w\ld be ! free e!r1 ( d5sity #a4 ,b !n ?is--on ! above view--is absolutely /ation>y1 n be+ c>ri$ along by ! e>? at all2 h5ce ?is c give no effect ei!r4 ,consequ5tly ! :ole effect ( an e!r-drift pa/ ! e>? is z]o1 on optical exp]im5ts1 accord+ to ! !ory ( ,fresnel2 & t is exactly :at all ! exp]im5ts j describ$ h confirm$4 ,s9ce !n ,pr(4 ,masc>t1 ) great p]t9acity1 has attack$ ! ph5om5a ( ?ick plates1 ,newton's r+s1 d\ble refraction1 & ! rotatory ph5om5on ( qu>tz2 b he has f\nd absolutely no?+ attributable to a /ream ( e!r pa/ ! e>?4 ,! only positive result ev] suppos$ to be atta9$ 0 9 a v difficult pol>isation obs]vation by ,fizeau 9 #ahei4 ,unless ?is has be5 repeat$1 x is safe/ to ignore x2 b ,i believe t ,"l ,rayleigh has repeat$ x1 & obta9$ a negative result4 ,fizeau also sugge/$1 b did n attempt1 :at seems an easi] exp]im5t1 ) =e & aft !rmopiles & a s\rce betwe5 !m1 to obs]ve ! drift ( a m$ium by its convection ( en]gy2 b argum5ts bas$ on ! law ( ex*anges#e t5d to %[1 & d %[ z ,i ?9k1 t a probable alt]ation ( radiat+ p[] due to motion ?r\gh a m$ium w\ld j comp5sate ! effect o!rwise to be expect$4 ,we may summ>ise mo/ ( ^! /atem5ts z foll[s3-- ,summ>y4 ,a real & app>5t *ange ( wave-l5g?4 ,s\rce alone ,a real b n app>5t error 9 direction4 mov+ produces ,no lag ( phase or *ange ( int5sity1 except t appropriate to alt]$ wave-l5g?4 ,no *ange ( frequ5cy4 ,m$ium alone ,no error 9 direction4 mov+1 or ,a real lag ( phase1 b undetectable s\rce & receiv] )\t control ov] ! mov+ m$ium4 toge!r1 produces ,a *ange ( int5sity correspond+ to diff]5t di/ance1 b comp5sat$ by *ange ( radiat+ p[]4 ,an app>5t *ange ( wave-l5g?4 ,an app>5t error 9 direction4 ,receiv] alone ,no *ange ( phase or ( int5sity1 mov+ produces except t appropriate to diff]5t virtual velocity ( light4 ,i may say1 !n1 t n a s+le optical ph5om5on is able to %[ ! exi/5ce ( an e!r /ream ne> ! e>?4 ,all optics g on precisely z if ! e!r 7 /agnant ) respect to ! e>?4 99 99 99 99 99 ,well1 !n1 p]haps x is /agnant4 ,! exp]im5ts ,i h quot$ d n prove t x is s4 ,!y are equally consi/5t ) its p]fect fre$om & ) its absolute /agnation2 ?\gh !y are n consi/5t ) any int]m$iate position4 ,c]ta9ly1 if ! e!r 7 /agnant no?+ c\ld be simpl] ?an _! explanation4 ,! only ph5om5a !n difficult to expla9 w\ld be ^? dep5d+ on light com+ f di/ant regions ?r\gh all ! lay]s ( m or less dragg$ e!r4 ,! !ory ( a/ronomical ab]ration w\ld be s]i\sly complicat$2 9 its pres5t =m x w\ld be upset 7p4 #de74 ,b x is nev] wise to control facts by a !ory2 x is bett] to inv5t "s exp]im5t t w give a diff]5t result 9 /agnant & 9 free e!r4 ,none ( ^? exp]im5ts s f> describ$ are really discrim9ative4 ,!y are1 z ,i say1 consi/5t ) ei!r hypo!sis1 ?\gh n v obvi\sly s4 ,illu/ration3 ,,fig4 #aj4 ,! c\rse ( ! light & ( ! two half-beams 9 ,mi*elson's mo/ fam\s exp]im5t4 ,! light is split at ,a1 "o half s5t t[>ds ,b & back1 ! o!r half to ,c & back4 ,comp>e ) ,fig4 #g4 ,mi*elson ,exp]im5t4 ,mr4 ,mi*elson1 h[ev]1 ( ! ,unit$ ,/ates1 inv5t$ a plan t look$ z if x really w\ld discrim9ate2 &1 aft] ov]com+ _m difficulties1 he c>ri$ x out4 ,x is describ$ 9 ! ,philosophical ,magaz9e = #ahhg4 ,mi*elson's fam\s exp]im5t consi/s 9 look+ = int]f]5ce betwe5 two half-beams ( light1 ( :i* "o has be5 s5t to & fro across ! l9e ( e!r drift1 & ! o!r has be5 s5t to & fro along ! l9e ( e!r drift4 ,a semi-transp>5t mirror set at #de is employ$ to split ! beam1 & a pair ( normal & ord9>y mirrors1 set p]p5dicul> to ! two half-beams1 are employ$ to return !m back :5ce !y came1 s t !y c ent] ! eye ?r\gh an obs]v+ telescope4 ,x diff]s ess5tially f ! int]f]5ce kaleidoscope1 ,fig4 #g1 inasmu* z !re is n[ no lum9\s pa? ,b ,c1 & no cont\r enclos$ by ! light4 ,ea* half-beam goes to & fro on its own pa?1 & ^! pa?s1 in/ead ( be+ co9cid5t1 are widely sep>ate1--"o ,nor? & ,s\?1 = in/ance1 & ! o!r ,ea/ & ,we/4 ,"u ^! conditions ! b&s are mu* m tremul\s ?an !y 7 9 ! arrangem5t ( ,fig4 #g1 & are subject to e k9d ( di/urbance4 ,! app>atus has to be excessively /eady1 & no fluctuation ev5 ( temp]ature mu/ be p]mitt$ 9 ! pa? ( ei!r beam4 ,to secure ?is1 ! s\rce1 ! mirrors1 & ! obs]v+ telescope1 7 all m\nt$ ^u a massive /one slab2 & ?is 0 float$ 9 a ba? ( m]cury4 ,! slab c\ld !n be sl[ly turn$ r\nd1 s t sometimes ! pa? ,a ,b & sometimes ! pa? ,a ,c lay approximately along or a?w>t ! direction ( ! e>?'s motion 9 space4 ,& inasmu* z ! motion along w\ld take a little long] ?an ! motion across1 ?\gh ev]y?+ else 0 accurately ! same1 "s %ift ( ! int]f]5ce b&s might be expect$ z ! slab rotat$4 ,b :]eas 9 all ! exp]im5ts previ\sly describ$ ! effect look$ = 0 a fir/-ord] effect1 ( magnitude "o 9 t5 or tw5ty ?\s&1--dep5d+1 t is to say1 on ! fir/ p[] ( ! ratio ( spe$ ( e>? to spe$ ( light1--! effect n[ to be expect$ dep5ds on ! squ>e ( t same ratio1 & !re=e _c be great]1 ev5 9 ! mo/ fav\rable circum/ances1 ?an #a "p 9 a hundr$ million4 ,x is easy to realise !re=e t x is an exceptionally difficult exp]im5t1 & t x requir$ bo? skill & p]t9acity to p]=m x successfully4 ,t x is an exceptionally difficult exp]im5t w be realis$ :5 ,i say t x w\ld fail 9 conclusiv5ess unless "o "p 9 #djj millions c\ld be cle>ly detect$4 ,mr4 ,mi*elson reckons t by 8 late/ arrangem5t he c\ld see #a 9 #djjj millions if x exi/$ 7:i* is equival5t to detect+ an error ( #a_/ajjj ( an in* 9 a l5g? ( #fj miles72 b he saw no?+4 ,ev]y?+ behav$ precisely z if ! e!r 0 /agnant2 z if ! e>? c>ri$ ) x all ! e!r 9 its imm$iate neighb\rhood4 ,& t 0 8 conclusion4 ,!ory ( ,mi*elson ,exp]im5t4 ,! !ory ( ! ,mi*elson exp]im5t c be express$ ?us3 its optical diagram be+ ! same z is express$ geometrically 9 ,fig4 #f4 ,if a relatively fix$ s\rce & receiv] move ?r\gh ! e!r ) velocity u1 su* t u_/v ! ab]ration con/ant2 !n ! "t ( any to & fro j\rney ,s ,m1 incl9$ at angle to ! direction ( ! drift1 is increas$1 above :at x w\ld be if !re 7 no drift1 9 ! ratio 7#a-s97 _/ 7#a-7 ,?is foll[s f m]ely geometrical consid]ations4 ,h5ce if a ray is split1 & half s5t s t #j :ile ! o!r half is s5t s t #ij 7z 9 ,fig4 #aj71 ! "o w lag beh9d ! o!r by a di/ance times ! di/ance travell$2 :i*1 ?\gh v small1 may be a p]ceptible fraction ( a wave-l5g?1 & !re=e may cause a p]ceptible %ift ( ! b&s4 ,b :5 ! exp]im5t is prop]ly p]=m$1 no su* %ift is obs]v$4 ,! exp]im5t ?us seems to prove t !re is no motion ?r\gh ! e!r at all1 t !re is no e!rial drift pa/ ! e>?1 t ! e!r imm$iately 9 contact ) ! e>? is /agnant--or t ! e>? to t ext5t c>ries all neighb\r+ e!r ) x4 ,if we wi% to evade ?is conclusion1 !re is no easy way ( do+ s4 ,= x dep5ds on no d\btful prop]ties ( transp>5t sub/ances1 b on ! /raight=w>d fundam5tal pr9ciple und]ly+ all su* simple facts z t--,x takes long] to r[ a c]ta9 di/ance & back1 up & d[n /ream1 ?an x does to r[ ! same di/ance 9 /ill wat]2 or t x takes long] to run up & d[n a hill1 ?an to run ! same di/ance laid out flat2 or t x co/s m to buy a c]ta9 numb] ( oranges at ?ree a p5ny & an equal numb] at two a p5ny ?an x does to buy ! :ole lot at five = twop5ce4 ,h5ce1 al?\gh !re may be "s way ( gett+ r\nd ,mr4 ,mi*elson's exp]im5t1 !re is no obvi\s way2 & if ! true conclusion be n t ! e!r ne> ! e>? is /agnant1 x mu/ lead to "s o!r important & unkn[n fact4 ,t fact has n[ come cle>ly to light4 ,x 0 fir/ sugge/$ by ! late ,pr(essor ,g4,f4 ,fitz,gerald1 ( ,tr9ity ,college ,dubl91 :ile sitt+ 9 my /udy at ,liv]pool & discuss+ ! matt] ) me4 ,! sugge/ion bore ! impress ( tru? f ! fir/4 ,x indep5d5tly occurr$ also to ,pr(essor ,h4,a4 ,lor5tz1 ( ,leid51 into ^: !ory x completely fits1 & :o has brilliantly work$ x into 8 sy/em4 ,x may be expla9$ briefly ?us3-- ,electric *>ges 9 motion con/itute an electric curr5t4 ,simil> *>ges repel ea* o!r1 b curr5ts 9 ! same direction attract4 ,consequ5tly two simil> *>ges mov+ 9 p>allel l9es w repel ea* o!r less ?an if /ation>y1--less also ?an if mov+ "o aft] ! o!r 9 ! same l9e4 ,likewise two opposite *>ges1 a fix$ di/ance ap>t1 attract ea* o!r less :5 mov+ side by side1 ?an :5 *as+ ea* o!r4 ,! modification ( ! /atic =ce1 ?us caus$1 dep5ds on ! squ>$ ratio ( _! jo9t spe$ to ! velocity ( light4 ,atoms ( matt] are *>g$2 & cohesion is a residual electric attraction 7see end ( ,app5dix #a74 ,s :5 a block ( matt] is mov+ ?r\gh ! e!r ( space its cohesive =ces across ! l9e ( motion are dim9i%$1 & consequ5tly 9 t direction x exp&s1 by an am\nt proportion$ to ! squ>e ( ab]ration magnitude4 ,a light j\rney1 to & fro1 across ! pa? ( a relatively mov+ m$ium is slightly quick] ?an ! same j\rney1 to & fro1 along 7see p4 #fd74 ,b if ! j\rneys are plann$ or set out on a block ( matt]1 !y d n rema9 q ! same :5 x is convey$ ?r\gh space3 ! j\rney across ! direction ( motion becomes long] ?an ! o!r j\rney1 z we h j se54 ,& ! extra di/ance comp5sates or neutralises ! extra spe$2 s t light takes ! same "t = bo?4 ,,footnotes3 #d ,! ^w /ation>y is ambigu\s4 ,i propose to use /agnant1 z mean+ /ation>y ) respect to ! e>?1 i4e4 z oppos$ to /ation>y 9 space4 #e ,"l ,rayleigh1 ,nature1 ,m>* #be1 #ahib4 ,,*apt] ,v ,,special ,,exp]im5t ,,on ,,e!rial ,,viscosity ,! balance ( evid5ce at ?is /age seems to incl9e 9 ! s5se t !re is no e!r drift1 t ! e!r ne> ! e>? is /agnant1 t ! e>? c>ries all or ! great] "p ( ! neighb\r+ e!r ) x1--a view :i*1 if true1 mu/ s+ul>ly complicate ! !ory ( ord9>y a/ronomical ab]ration3 z is expla9$ at ! beg9n+ ( ! la/ *apt]4 ,b n[ put ! "q ano!r way4 ,c matt] c>ry neighb\r+ e!r ) x :5 x moves8 ,ab&on ! e>? altoge!r2 its motion is v quick1 b too uncontrollable1 & x always gives negative results4 ,take a lump ( matt] t y c deal )1 & see if x pulls any e!r along4 ,t is ! exp]im5t :i* ,i set myself to p]=m1 & :i* 9 ! c\rse ( ! ye>s #ahia-ig ,i p]=m$4 ,x may be ?us describ$ 9 ess5ce3-- ,take a /eel disk1 or r a c\ple ( l>ge /eel disks a y>d 9 diamet] clamp$ toge!r ) a space betwe54 ,m\nt ! sy/em on a v]tical axis1 & sp9 x l a teetotum z fa/ z x w /& )\t fly+ to pieces4 ,!n take a p>allel beam ( light1 split x into two by a semi-transp>5t mirror1 ,m1 a piece ( glass silv]$ s ?9ly t x lets half ! light ?r\gh & reflects ! o!r half1 some:at z 9 ,fig4 #g2 & s5d ! two halves ( ?is split beam r\nd & r\nd 9 opposite directions 9 ! space betwe5 ! disks4 ,!y may ?us travel a di/ance ( #bj or #cj or #dj feet4 ,ultimately !y are all[$ to meet & ent] a telescope4 ,if !y h gone q id5tical di/ances !y ne$ n int]f]e1 b usually ! di/ances w diff] by a hundr$-?\s&? ( an in* or s1 :i* is q en\gh to br+ ab\t int]f]5ce4 ,! mirrors :i* reflect ! light r\nd & r\nd betwe5 ! disks are %[n 9 ,fig4 #aa4 ,if !y =m an accurate squ>e ! la/ two images w co9cide1 b if ! mirrors are ! lea/ incl9$ to "o ano!r at any unaliquot "p ( #cfj ! la/ image splits into two1 z 9 ! kaleidoscope is well kn[n1 & ! int]f]5ce b&s may be reg>d$ z result+ f ^? two s\rces4 ,! c5tral :ite b& bisects normally ! di/ance betwe5 !m1 & _! am\nt ( sep>ation det]m9es ! wid? ( ! b&s4 ,!re are _m int]e/+ optical details "h1 b ,i %all n g into !m4 ,illu/ration3 ,,fig4 #aa4 ,diagrammatic ,plan ( ,optical ,frame = ,e!r ,ma*9e2 ) ,/eel ,disks1 "o y>d 9 diamet]1 inside ! frame4 ,! actual app>atus is %[n 9 ,figs4 #ac & #ad & ,fig4 #ab4 ,m is a semi-transp>5t mirror1 reflect+ half an incid5t beam & transmitt+ ! o!r half4 ,! two half-beams ea* g ?ree times r\nd ! squ>e cont\r1 9 opposite directions1 & !n reunite4 ,x is an ext5sion ( ! idea ( ,fig4 #g4 ,! ?+ to obs]ve is :e!r ! motion ( ! disks is able to replace a bright b& by a d>k "o1 or vice v]sa4 ,if x does1 x means t "o ( ! half-beams1 viz4 t :i* is travell+ 9 ! same direction z ! disks1 is help$ on a trifle1 equival5t to a %ort5+ ( j\rney by "s qu>t] million? ( an in* or s 9 ! :ole l5g? ( #cj feet2 :ile ! o!r half-beam1 viz4 t travell+ aga9/ ! motion ( ! disks1 is ret>d$1 or its pa? virtually l5g!n$1 by ! same am\nt4 ,if ?is accel]ation & ret>dation actually occurs1 waves :i* did n int]f]e on meet+ be=e ! disks mov$1 w int]f]e n[2 = "o w arrive at ! common goal half a l5g? beh9d ! o!r4 ,n[ a gradual *ange ( bright space to d>k1 & vice v]sa1 %[s itself1 to an obs]v] look+ at ! b&s1 z a gradual *ange ( position ( ! bright /ripes1 or a %ift ( ! b&s4 ,a %ift ( ! b&s1 & especially ( ! middle :ite b&1 :i* is mu* m /able ?an ! o!rs1 is :at we look =4 ,! middle b& is1 or %\ld be1 free f ! conc]t9a-l motion :i* is liable to infect ! o!rs4 ,at fir/ ,i saw pl5ty ( %ift4 ,9 ! fir/ exp]im5t ! b&s sail$ across ! field z ! disks got up spe$ until ! crosswire _h trav]s$ a b& & a half4 ,! conditions 7 su* t _h ! e!r :irl$ at ! full spe$ ( ! disks ,i %\ld h se5 a %ift ( ?ree b&s4 ,x look$ v mu* z if ! light 0 help$ along at half ! spe$ ( ! mov+ matt]1 j z x is inside wat]4 ,on /opp+ ! disks ! b&s return$ to _! old position4 ,on />t+ !m aga9 9 ! opposite direction1 ! b&s ought to h %ift$ ! o!r way too1 if ! effect 0 g5u9e2 b !y did n2 !y w5t ! same way z be=e4 ,! %ift 0 !re=e :olly spuri\s2 x 0 caus$ by ! c5trifugal =ce ( ! bla/ ( air ?r[n (f f ! mov+ disks4 ,! mirrors & frame _h to be protect$ f ?is4 ,_m o!r small *anges _h to be made1 & gradually ! spuri\s %ifts h be5 r$uc$ & r$uc$1 l>gely by ! skill & pati5ce ( my assi/ant1 ,mr4 ,b5jam9 ,davies1 until pres5tly !re 0 b>ely a trace ( !m4 ,b ! exp]im5t is n an easy "o4 ,n only does ! bla/ ex]t pressure1 b at high spe$s ! *urn+ ( ! air makes x q hot4 ,moreov]1 ! tremor ( ! :irl+ ma*9e1 9 :i* f f\r to n9e horse-p[] is sometimes be+ exp5d$1 is b too liable to communicate itself to ! optical "p ( ! app>atus4 ,( c\rse elaborate precautions are tak5 aga9/ ?is4 ,al?\gh ! two p>ts1 ! me*anical & ! optical1 are s close toge!r1 _! supports are entirely indep5d5t4 ,b !y h to re/ on ! same e>?1 & h5ce communicat$ tremors are n abs5t4 ,!y are ! cause ( mo/ ( ! slight residual tr\ble4 ,! :ole exp]im5t is describ$ 9 fairly full detail 9 ! ,philosophical ,transactions ( ! ,royal ,society = #ahic & #ahig4 ,& !re also are describ$ "s fur!r modifications :]eby ! :irl+ disks are electrifi$--likewise )\t optical effect1 & are also magnetis$2 or r a great iron mass1 /rongly magnetis$ by a curr5t1 is us$ to replace ! /eel disks4 ,! effect 0 always z]o1 h[ev]1 :5 spuri\s results 7 elim9at$2 & x is cle> t at no practicable spe$ does ei!r electrification or magnetisation conf] ^u matt] any appreciable visc\s grip ^u ! e!r4 ,atoms mu/ be able to ?r[ x into vibration1 if !y are oscillat+ or revolv+ at suffici5t spe$2 o!rwise !y w\ld n emit light or any k9d ( radiation2 b 9 no case d !y appe> to drag x along1 or to meet ) resi/ance 9 any uni=m motion ?r\gh x4 ,only _! accel]ation is effectual4 ,9 ! light ( ,l>mor's electron !ory1 we "k n[ t accel]ation ( atoms1 or r ( a *>ge ^u an atom1 necess>ily g5]ates radiation1 proportional 9 am\nt to ! squ>e ( ! accel]ation--:e!r t be tang5tial or normal4 ,!re is no !oretical reason = assum+ any influ5ce on uni=m velocity4 ,& ev5 ! influ5ce on accel]ation is exce$+ly small "u ord9>y circum/ances4 ,only dur+ ! viol5ce ( collision are e!r waves freely excit$4 ,! pres5t exp]im5t1 h[ev]1 has no?+ to d ) accel]ation3 x is a te/ ( viscosity4 ,an accel]ation t]m exi/s 9 motion ?r\gh ev5 a p]fect fluid4 ,illu/ration3 ,,fig4 #ab4 ,g5]al view ( :irl+ "p ( ,e!r ma*9e1 ) pair ( /eel disks1 & motor4 ,to face page #gb4 ,illu/ration3 ,,fig4 #ac4 ,g5]al view ( optical framework--su/a9+ mirrors1 telescope1 & collimator--to surr\nd ! disks ( ! ,e!r ma*9e4 ,comp>e fig4 #aa4 ,to face page #gc4 ,! conclusion at :i* ,i arriv$ 9 #ahib & #ahic is ?us express$ 7p4 #ggg ( vol4 #ahd ,philosophical ,transactions ( ! ,royal ,society73 ,i feel confid5t ei!r t ! e!r betwe5 ! disks is q unaffect$ by _! motion1 or1 if affect$ at all1 by some?+ less ?an ! ?\s&? "p4 ,at ! same "t1 s f> z rigor\s pro( is conc]n$1 ,i %\ld pref] to ass]t t ! velocity ( light betwe5 two /eel plates mov+ toge!r 9 _! own plane an in* ap>t is n increas$ or dim9i%$ by s mu* z ! #a_/bjj? "p ( _! velocity4 ,t 0 ! conclusion 9 #ahic2 b s9ce !n obs]vations h be5 cont9u$1 & x is n[ q safe to *ange ! #a_/bjj? into #a_/ajjj?4 ,! sp9 0 sometimes cont9u$ = ?ree h\rs to see if an effect develop$ ) "t2 & _m o!r precautions 7 tak51 z briefly n>rat$ 9 ! ,philosophical ,transactions = #ahig4 ,! foll[+ illu/rations give an idea ( ! app>atus employ$4 ,fig4 #ab %[s a photograph ( ! :irl+ ma*9e be=e be+ bolt$ d[n to its /one pi]2 ) ! pair ( disks at top ready to be :irl$ by an armature on ! %aft1 :i* is suppli$ ) a curr5t sometimes ( n9e horse-p[]4 ,! armature w9d+ 0 ( l[ resi/ance1 & 0 specially brac$1 s z to give high spe$ )\t fly+ out1 & )\t g5]at+ too mu* back-,e ,m ,f4 ,! amp]e-met] & volt-met] & ! c>bon rheo/at 79 armature circuit71 = regulat+ ! spe$1 are pla9ly se54 ,! smoo? pulley on ! %aft is = apply+ a brake4 ,! small disk above x is p]=at$ to act z a sir5 = e/imation ( spe$2 b o!r arrangem5ts = ?is purpose 7 subsequ5tly add$4 ,! two l>ge disks at top 7 ( ! be/ circul>-saw /eel2 !y are some:at ?ick] at middle ?an at edge1 & are /rongly bolt$ up betwe5 iron *eeks1 :i* are atta*$ to ! %aft4 ,! l[] end ( ! %aft is a /ep-be>+ ( h>d5$ /eel 9 a vessel ( oil4 ,! upp] coll> is ela/ic1 s z to all[ = a /eady+ teetotum action at high spe$s4 ,fig4 #ac is a photograph ( ! optical squ>e1 :i* 0 ultimately to be plac$ 9 position surr\nd+ ! disks4 ,! slit & collimator are %[n2 ! micromet] end ( ! obs]v+ telescope is out ( ! picture4 ,! mirrors on ! sides ( ! squ>e are accurately plane2 !y are adju/able on geometric pr9ciples1 & are press$ aga9/ _! be>+s by /rong spiral spr+s4 ,!y 7 made by ,hilg]4 ,a draw+ ( ! arrangem5t is giv5 9 ,fig4 #ad1 & "h ! d\ble micromet] eye-piece is visible4 ,9 ,fig4 #ae ! :ole app>atus is %[n m\nt$4 ,! :irl+ ma*9e /rongly bolt$ d[n to a /one pi] indep5d5t ( ! floor2 ! optical frame indep5d5tly support$ by a gall[s frame f o!r pi]s4 ,! c5trifugal m]cury spe$-indicator is visible 9 front1 & ,mr4 ,davies is regulat+ ! spe$4 ,at ! back is se5 a boil]-plate scre5 = ! obs]v] ) 8 eye at ! telescope4 7,see ,frontispiece47 ,illu/ration3 ,lodge ,phil4 ,trans4 #ahic4 ,a4 ,plate #ca4 ,! mirror frame is pivot$ on a v]tical axis "h ,horizontal axis ( frame ,mode ( m\nt+ ! semi-transp>5t mirror ,m s z to give altitude & azimu? movem5t to ! reflect$ beam ,details ( brass plate support+ f\r? mirror front1 side & back views ,back view %[s ! ?ree slots 9 :i* ! ends ( ! support+ screws re/ giv+ a f9e adju/m5t1 ! plate be+ support$ by ?ree rigid pu%es & ?ree ela/ic pulls4 ,,fig4 #ad ,plan ( optical frame ) /eel disk 9 position1 & glaz$ drum to isolate !m f ! frame4 ,g repres5ts "o ( ! panes ( optical glass4 ,supports ( telescope & collimator also %ewn1 & "p ( ! fix+ ( ! f\r mirrors #a4b4c4d41 ?ree ( !m let into recesses 9 ! wood5 frame1 ea* mirror held by a brass plate support$ by ?ree f9ely cut screws aga9/ :i* x is press$ by ! spr+-bolts %ewn ,m is ! semi-transp>5t mirror ,we/1 ,newman li? ,,fig4 #ad4 ,to face page #gd4 ,! exp5se ( ! app>atus 0 borne by my fri5d ! late ,george ,holt1 %ip[n]1 ( ,liv]pool4 ,fig4 #af exhibits some?+ l ! appe>ance se5 9 ! eye-piece1 ) ! int]f]5ce b&s on ea* side ( ! middle b&1 & ) ! micromet] wires set 9 position--ea* mov$ by an indep5d5t micromet] head4 ,! /raight v]tical wire 0 usually set 9 ! c5tre ( ! middle :ite b&1 & ! ,x wire on ! yell[ ( ! fir/ col\r$ b& on "o side or ! o!r4 ,! me?od ( obs]vation n[ consi/s 9 sett+ a wire ( ! micromet] accurately 9 ! c5tre ( ! middle b&1 :ile ano!r wire is usually set on ! fir/ b& to ! left4 ,!n ! micromet] heads are read1 & ! sett+ repeat$ once or twice to see h[ closely & dep5dably !y c be set 9 ! same position4 ,!n we beg9 to sp9 ! disks1 & :5 !y are go+ at "s high spe$1 measur$ by a sir5 note & 9 o!r ways1 ! micromet] wires are reset & read--reset sev]al times & read ea* "t4 ,!n ! disks are /opp$ & m read+s are tak54 ,!n _! motion is rev]s$1 ! wires set & read aga92 & f9ally ! motion is once m /opp$ & ano!r set ( read+s tak54 ,by ?is means ! absolute %ift ( middle b&1 & its relative int]pretation 9 t]ms ( wave-l5g?1 are simultane\sly obta9$2 = ! di/ance f ! "o wire to ! o!r1 :i* is (t5 two revolutions ( a micromet] head1 repres5ts a :ole wave-l5g? %ift4 ,9 ! be/ exp]im5ts ,i d /ill (t5 see some?+ l a fiftie? ( a b& %ift2 b x is caus$ by residual spuri\s causes1 = x repeats itself ) suffici5t accuracy 9 ! same direction :5 ! disks are spun ! o!r way r\nd4 ,( real rev]sible %ift1 due to motion ( ! e!r1 ,i see no?+4 ,i d n believe ! e!r moves4 ,x does n move at a five-hundr$? "p ( ! spe$ ( ! /eel disks4 ,fur!r exp]i5ce confirms & /r5g!ns ?is e/imate1 & my conclusion is t su* ?+s z circul> saws1 fly:eels1 railway tra9s1 & all ord9>y masses ( matt] d n appreciably c>ry ! e!r ) !m4 ,_! motion does n seem to di/urb x 9 ! lea/4 ,! presumption is t ! same is true = ! e>?2 b ! e>? is a big body1--x is conceivable t s great a mass may be able to act :5 a small mass w\ld fail4 ,i w\ld n l to be too sure ab\t ! e>?--at lea/ n on a /rictly exp]im5tal basis4 ,:at ,i d feel sure ( is t if mov+ matt] di/urbs e!r 9 its neighb\rhood at all1 x does s by "s m9ute action1 comp>able 9 am\nt p]haps to gravitation1 & possibly by means ( ! same prop]ty z t to :i* gravitation is due--n by any?+ t c fairly be lik5$ to e!rial viscosity4 ,s f> z exp]im5t has gone1 our conclusion is t ! viscosity or fluid friction ( ! e!r is z]o4 ,& t is an entirely reasonable conclusion4 ,illu/ration3 ,,fig4 #af4 ,approximate appe>ance ( ! int]f]5ce b&s & micromet] wires z se5 9 ! eye-piece ( ! telescope ( ! ,e!r ma*9e4 ,illu/ration3 ,,fig4 #ah4 ,appe>ance ( ! int]f]5ce b&s 9 ! *annel ( ! iron sph]oid4 ,!y 7 reflect$ 9 ! upp] iron z %[n4 ,to face page #gf4 ,oblate sph]oid = ,:irl+ ,ma*9e4 ,illu/ration3 ,,fig4 #ag4 ,section ( oblate sph]oid ( s(t iron = :irl+ ma*9e1 %[+ arrangem5t = w9d+ c5tral core ) wire s z to be able to magnetise x /rongly :ile sp9n+ inside ! optical frame4 ,to face page #gg4 ,,magnetisation4 ,= te/+ ! effect ( magnetism1 an oblate sph]oid 0 made ( specially select$ s(t iron1 #c feet 9 diamet]1 weigh+ ne>ly a ton4 ,its section is %[n 9 ,fig4 #ag4 ,x _h an annul> *annel or groove1 half an in* wide & #a foot deep1 r\nd ! bottom ( :i* 0 w\nd a kilometre ( insulat$ wire to a dep? ( #d in*es2 ! t]m9als ( :i* 7 br\ght out to slid+ contacts on ! %aft1 s t ! :ole c\ld be v highly magnetis$ :ile x 0 sp9n+4 ,ev]y?+ 0 arrang$ s z to be symmetrical ab\t ! c5tral axis4 ,to ! coil ( wire1 ^: resi/ance 0 #cj ohms1 #aaj volts 0 ord9>ily1 & #bbj volts exceptionally1 appli$4 ,! magnetic field ) #aaj volts 0 ab\t #ahjj c4g4s41 on ! av]age1 all ov] ! ma9 region ?r\gh :i* ! beam ( light circulat$4 ,?is light-be>+ space1 or gap 9 ! magnetic circuit1 0 only half an in* wide2 & accord+ly 9 ! eye-piece ! iron surfaces c\ld be se51 above & bel[1 z well z ! int]f]5ce b&s 9 ! lum9\s gap4 ,! :ole appe>ance is depict$ 9 ,fig4 #ah4 ,,electrification4 ,= ! electrification exp]im5t1 a ?ird & insulat$ disk 0 clamp$ betwe5 ! two /eel disks & kept electrifi$ to sp>k+ t5sion4 ,! arrangem5t is %[n diagrammatically on a small] scale 9 ,fig4 #ai4 ,illu/ration3 ,,fig4 #ai4 ,arrangem5t = electrify+ a ?ird or middle /eel disk to sp>k+ pot5tial :ile sp9n+4 ,! electrification te/ 0 exceptionally easy to apply1 by connect+ ! insulat$ *>g+ p9 to a ,voss ma*9e 9 action3 because :5 ! disks 7 sp9n+ & ! b&s 9 good condition1 ! electrification c\ld be in/antane\sly appli$1 tak5 (f1 rev]s$1 or :atev] 0 desir$2 & ! effect ( ! sudd5 l[]+ ( pot5tial by sp>ks pass+ betwe5 ! revolv+ plates c\ld be exactly look$ =4 ,! conclusion ( my second ,philosophical ,transactions pap]--t ( #ahig--;is t nei!r an electric nor a magnetic transv]se field conf]s viscosity ^u ! e!r1 nor enables mov+ matt] to grip & move x rotationally4 ,,"q ,,( ,a ,,possible ,,longitud9al ,,magnetic ,,drift4 ,lat] ,i tri$ a longitud9al magnetic field also2 arrang+ a s]ies ( f\r l>ge electric bobb9s or long coils along ! sides ( a squ>e inscrib$ at #de 9 ! optical squ>e1 ,figs4 #aa & #ac2 s t ! light w5t along _! axes4 ,! details ( ?is exp]im5t h be5 only p>tially record$1 b ! sali5t po9ts are to be f\nd /at$ 9 ! ,philosophical ,magaz9e = ,april1 #aijg1 pages #die-ejj4 ,! result 0 aga9 negative2 t is to say1 a magnetic field causes no p]ceptible accel]ation 9 a beam ( light s5t along ! l9es ( =ce4 ,! extra velocity t c\ld h be5 obs]v$ w\ld h be5 #a_/i? ( a millimetre p] second1 or #af miles p] h\r1 = ea* ,c4,g4,s4 unit ( field int5sity4 ,ano!r mode ( express+ ! result is t ! diff]5ce ( magnetic pot5tial appli$1 namely1 a drop ( two million ,c4,g4,s4 units ( magnetic pot5tial1 does n hurry light along x by s mu* z #a_/ej? "p ( a wave-l5g?4 ,!re may be reasons = suppos+ t "s mu* sl[] drift or conveyance ?an ?is is really caus$ 9 ! e!r by a magnetic field2 b if s1 ! e!r mu/ be reg>d$ z s excessively d5se t ! am\nt ( su* a drift = any practicable magnetic field seems almo/ hopelessly beyond exp]im5tal means ( detection4 ,,*apt] ,,vi ,,e!rial ,,d5sity ,?is leads u to ent] ^u ! "q ( :e!r x is possible to det]m9e ) any approa* to accuracy ! actual d5sity or massiv5ess ( ! e!r ( space1 comp>$ ) ^? =ms ( matt] to :i* our s5ses h made u accu/om$4 ,! argum5ts on :i* an e/imate may be made ( ! d5sity or massiv5ess ( ! e!r z comp>$ ) t ( matt] dep5d on ! foll[+ consid]ations1 ! validity ( :i* aga9 is dep5d5t ^u an electrical !ory ( matt]4 ,9 ?is !ory1 or work+ hypo!sis1 an assumption has to be made3 b x is "o = :i* !re is a l>ge am\nt ( ju/ification1 & ! reasons = x are giv5 9 _m books1--among o!rs 9 my book on ,electrons1 & likewise at ! end ( ! new edition ( ,mod]n ,views ( ,electricity1 also 9 my ,romanes ,lecture1 publi%$ by ! ,cl>5don ,press 9 #aijc4 ,put briefly1 ! assumption is t matt] is compos$1 9 "s way or o!r1 ( electrons2 :i* aga9 mu/ be consid]$ to be ess5tially peculi>ities1 or s+ul>ities1 or def9ite /ructures1 9 ! e!r itself4 ,inde$1 a consid]ation ( electrons alone is suffici5t = ! argum5t1 provid$ x be admitt$ t !y h ! mass :i* exp]im5t %[s !m to possess1 & ! size :i* electrical !ory d$uces = !m3 ! basis ( ! idea--:i*1 inde$1 is n[ exp]im5tally prov$--be+ t _! in]tia is due to _! self-induction1--i4e4 to ! magnetic field ) :i* !y mu/ be surr\nd$ z long z !y are 9 motion4 ,! mass1 or in]tia1 ( an electron is comp>able to ! ?\s&? "p ( t ( ! atom ( hydrog54 ,its l9e> dim5sion1 let u say its diamet]1 is comp>able to ! "o-hundr$-?\s&? "p ( :at is commonly kn[n z molecul> or atomic dim5sion2 :i* itself is ! t5-million? "p ( a millimetre4 ,h5ce1 ! mass & ! bulk ( an electron be+ kn[n1 its d5sity is det]m9$1 provid$ we c assume t its mass is all dep5d5t on :at is conta9$ )9 its p]iph]y4 ,b t la/ assumption is "o t q def9itely _c be made3 its mass is = ! mo/ "p outside itself1 & has to be calculat$ by magnetic consid]ations4 7,see ,app5dix #b47 ,^! details are gone into 9 my pap] 9 ! ,philosophical ,magaz9e = ,april1 #aijg1 & 9 ,*apt] ,,xvii ( ,mod]n ,views ( ,electricity4 ,b )\t repeat+ argum5ts "h1 x w suffice to say t al?\gh ! e/imates may be made 9 v>i\s ways1 diff]+ entirely f ea* o!r1 yet ! result+ diff]5ces are only slight2 ! calculat$ d5sities come out all ( ! same ord] ( magnitude1 namely1 some?+ comp>able to #aj ,c4,g4,s4 units1--t is to say1 a million million grammes p] cubic c5timetre1 or1 9 o!r words1 a ?\s& tons to ! cubic millimetre4 ,b1 ?r\gh\t1 we h se5 reason to ass]t t ! e!r is incompressible2 argum5ts = ?is are giv5 9 ,mod]n ,views ( ,electricity1 ,*apt] ,i4 ,&1 inde$1 ! fundam5tal m$ium fill+ all space1 if !re be su*1 mu/1 9 my judgm5t1 be ultimately incompressible2 o!rwise x w\ld be compos$ ( p>ts1 & we %\ld h to seek = some?+ /ill m fundam5tal to fill ! int]/ices4 ,! e!r be+ incompressible1 & an electron be+ suppos$ compos$ simply & solely ( e!r1 x foll[s t x _c be ei!r a cond5sation or a r>efaction ( t mat]ial1 b mu/ be "s s+ul>ity ( /ructure1 or "s portion o!rwise diff]5tiat$4 ,x might1 = in/ance1 be some?+ analog\s to a vortex r+1 diff]5tiat$ k9etically1 i4e4 by reason ( its rotational motion1 f ! rema9d] ( ! e!r2 or x might be diff]5tiat$ /atically1 & be some?+ :i* w\ld h to be call$ a /ra9-c5tre or a region ( twi/1 or some?+ :i* _c be v cle>ly at pres5t imag9$ ) any security2 ?\gh v>i\s sugge/ions h be5 made 9 t direction4 ,! simple/ plan = u is to ?9k ( x some:at z we ?9k ( a knot on a piece ( /r+4 ,! knot diff]s 9 no respect f ! re/ ( ! /r+1 except 9 its ti$-up /ructure2 x is ( ! same d5sity ) ! re/1 & yet x is diff]5tiat$ f ! re/2 &1 9 ord] to cease to be a knot1 w\ld h to be unti$--a process :i* z yet we h n le>n$ h[ to apply to an electron4 ,if ev] su* a proc$ure becomes possible1 !n electrons w !reby be resolv$ into ! g5]al body ( ! undiff]5tiat$ e!r ( space1--t "p :i* is indep5d5t ( :at we call matt]4 ,! important notion = pres5t purposes is m]ely ?is3 t ! d5sity ( ! undiff]5tiat$ or simple e!r1 & ! d5sity ( ! ti$-up or be-knott$ or o!rwise modifi$ e!r con/itut+ an electron1 are "o & ! same4 ,h5ce ! argum5t above giv51 at lea/ :5 prop]ly work$ out1 t5ds to e/abli% ! e!rial d5sity z ( ! ord] #aj times t ( wat]4 ,!re ought to be no?+ surpris+ 7?\gh ,i admit t !re is some?+ v surpris+7 9 su* an e/imate2 inasmu* z _m conv]g+ l9es ( argum5t t5d to %[ t ord9>y matt] is a v por\s or gossam]-l sub/ance1 ) int]spaces great z comp>$ ) ! spaces actually occupi$ by ! nuclei :i* con/itute x4 ,our conception ( matt]1 if x is to be compos$ ( electrons1 is necess>ily r l ! conception ( a sol> sy/em1 or r ( a milky way2 :]e !re are innum]able dots "h & !re1 ) great int]spaces betwe54 ,s t ! av]age d5sity ( ! :ole ( ! dots or mat]ial p>ticles tak5 toge!r1--t is to say1 _! aggregate mass comp>$ ) ! space !y occupy1--is excessively small4 ,9 ! va/ ext5t ( ! ,cosmos1 z a :ole1 ! small bulk ( actual matt]1 comp>$ ) ! volume ( empty space1 is /rik+--z we %all %[ directly2 & n[ on ! small scale1 among ! atoms ( matt]1 we f9d ! conditions to be simil>4 ,ev5 :at we call ! d5se/ mat]ial is ( extraord9>ily insignificant massiv5ess z comp>$ ) ! unmodifi$ e!r :i* occupies by f> ! great] proportion ( its bulk4 ,:5 we speak ( ! d5sity ( matt]1 we are really ?\gh n consci\sly express+ ! gr\p-d5sity ( ! modifi$ e!r :i* con/itutes matt]1--n e/imat$ p] unit1 b p] aggregate2 j z we might e/imate ! gr\p or av]age d5sity ( a cl\d or mi/4 ,reckon$ p] unit1 a cl\d has ! d5sity ( wat]2 reckon$ p] aggregate1 x is an impalpable filmy /ructure ( h>dly any d5sity at all4 ,s x is ) a cobweb1 s p]haps x is ) a comet's tail1 s also ) ! ,milky ,way1 ) ! cosmos1--&1 z x n[ turns out1 ) ord9>y matt] itself4 ,= consid] ! av]age d5sity ( ! mat]ial cosmos4 ,x comes out almo/ incr$ibly small4 ,9 o!r words1 ! am\nt ( matt] 9 space1 comp>$ ) ! volume ( space x occupies1 is almo/ inf9itesimal4 ,"l ,kelv9 argues t ultimately x mu/ be really inf9itesimal 7,philosophical ,magaz9e1 ,aug41 #aija1 & ,jan41 #aijb71 t is to say t ! volume ( space is inf9itely great] ?an ! total bulk ( matt] :i* x conta9s4 ,o!rwise ! comb9$ =ce ( gravity--or at lea/ ! aggregate gravitational pot5tial--on :i* ! velocity g5]at$ 9 mat]ial bodies ultimately dep5ds1 w\ld be f> great] ?an obs]vation %[s x to be4 ,! :ole visible univ]se1 )9 a p>allax ( #a_/ajjj second ( arc1 is e/imat$ by ,"l ,kelv9 z ! equival5t ( a ?\s& million ( our suns2 & ?is am\nt ( matt]1 di/ribut$ z x is1 w\ld h an av]age d5sity ( #af #aj grammes p] c4c4 ,x is notewor?y h[ exce$+ly small is ?is av]age or aggregate d5sity ( matt] 9 ! visible region ( space4 ,! e/imat$ d5sity ( #aj c4g4s4 means t ! visible cosmos is z mu* r>] ?an a vacuum ( a hundr$ million?s ( an atmosph]e1 z t vacuum is itself r>] ?an lead4 ,x is because we h reason to ass]t t any ord9>y mass ( matt] consi/s1 l ! cosmos1 ( sep>at$ p>ticles1 ) great int]v5+ di/ances 9 proportion to _! size1 t we are able to ma9ta9 t ! aggregate d5sity ( ord9>y /uff1 su* z wat] or lead1 is v small comp>$ ) ! cont9u\s m$ium 9 :i* !y exi/1 & ( :i* all p>ticles are suppos$ to be really compos$4 ,s t lead is to ! e!r1 z reg>ds d5sity1 v mu* z ! vacuum above spok5 ( is to lead4 ,! fundam5tal m$ium itself mu/ be ( uni=m d5sity ev]y:]e1 :e!r mat]ialis$ or free4 ,,*apt] ,,vii ,,fur!r ,,explanations ,,conc]n+ ,,! ,,d5sity ,,& ,,en]gy ,,( ,,! ,,e!r ,a read] may suppose t 9 speak+ ( ! imm5se d5sity or massiv5ess ( e!r1 & ! absurdly small d5sity or specific gravity ( gross matt] by comp>ison1 ,i int5d to signify t matt] is a r>efaction ( ! e!r4 ,t1 h[ev]1 is n my int5tion4 ,! view ,i advocate is t ! e!r is a p]fect cont9uum1 an absolute pl5um1 & t !re=e no r>efaction is possible4 ,! e!r inside matt] is j z d5se z ! e!r outside1 & no d5s]4 ,a mat]ial unit--say an electron--is only a peculi>ity or s+ul>ity ( "s k9d 9 ! e!r itself1 :i* is ( p]fectly uni=m d5sity ev]y:]e4 ,:at we s5se z matt] is an aggregate or gr\p+ ( an enorm\s numb] ( su* units4 ,h[ !n c we say t matt] is millions ( times r>] or less sub/antial ?an ! e!r ( :i* x is ess5tially compos$8 ,^? :o feel any difficulty "h1 %\ld be?9k !mselves ( :at !y mean by ! av]age or aggregate d5sity ( any discont9u\s sy/em1 su* z a p[d]1 or a gas1 or a precipitate1 or a sn[/orm1 or a cl\d1 or a milky way4 ,if x be urg$ t x is unfair to comp>e an obvi\sly discrete assemblage l ! />s1 ) an app>5tly cont9u\s sub/ance l air or lead1--! answ] is t x is entirely & accurately fair2 s9ce air1 & e o!r kn[n =m ( matt]1 is ess5tially an aggregate ( p>ticles1 & s9ce x is always _! av]age d5sity t we mean4 ,we d n ev5 "k = c]ta9 _! individual atomic d5sity4 ,! phrase specific gravity or d5sity ( a p[d] is ambigu\s4 ,x may mean ! specific gravity ( ! dry p[d] z x lies1 l sn[2 or x may mean ! specific gravity ( ! p>ticles ( :i* x is compos$1 l ice4 ,s also ) reg>d to ! d5sity ( matt]1 we might mean ! d5sity ( ! fundam5tal mat]ial ( :i* its units are made--:i* w\ld be e!r2 or we might1 & 9 practice d1 mean ! d5sity ( ! aggregate lump :i* we c see & h&le2 t is to say1 ( wat] or iron or lead1 z ! case may be4 ,9 say+ t ! d5sity ( matt] is small1--,i mean1 ( c\rse1 9 ! la/1 ! usual1 s5se4 ,9 say+ t ! d5sity ( e!r is great1--,i mean t ! actual /uff ( :i* ^! highly por\s aggregates are compos$ is ( imm5se1 ( wellnigh incr$ible1 d5sity4 ,x is only ano!r way ( say+ t ! ultimate units ( matt] are few & f> betwe5--i4e4 t !y are excessively small z comp>$ ) ! di/ances betwe5 !m2 j z ! planets ( ! sol> sy/em1 or worlds 9 ! sky1 are few & f> betwe51--! int]v5+ di/ances be+ enorm\s z comp>$ ) ! portions ( space actually occupi$ by lumps ( matt]4 ,x may be not$ t x is n unreasonable to argue t ! d5sity ( a cont9uum is necess>ily great] ?an ! d5sity ( any disconnect$ aggregate3 c]ta9ly ( any assemblage ^: p>ticles are actually compos$ ( ! mat]ial ( ! cont9uum4 ,because ! =m] is all !re1 ev]y:]e1 )\t break or int]mitt5ce ( any k9d2 :ile ! latt] has gaps 9 x1--x is "h1 & !re1 b n ev]y:]e4 ,inde$1 ?is v argum5t 0 us$ long ago by t notable g5ius ,rob]t ,hooke1 & ,i quote a passage :i* ,pr(essor ,poynt+ has discov]$ 9 8 collect$ po/hum\s works & k9dly copi$ out = me3-- ,z = matt]1 t ,i conceive 9 its ess5ce to be immutable1 & its ess5ce be+ expatiation det]m9ate1 x _c be alt]$ 9 its quantity1 ei!r by cond5sation or r>efaction2 t is1 !re _c be m or less ( t p[] or reality1 :atev] x be1 )9 ! same expatiation or cont5t2 b e equal expatiation conta9s1 is fill$1 or is an equal quantity ( mat]ia2 & ! d5se/ or heavie/1 or mo/ p[]ful body 9 ! _w conta9s no m mat]ia ?an t :i* we conceive to be ! r>e/1 ?9ne/1 lighte/1 or lea/ p[]ful body ( all2 z gold = in/ance1 & !r1 or ! sub/ance t fills ! cavity ( an exhau/$ vessel1 or cavity ( ! glass ( a b>omet] above ! quicksilv]4 ,nay1 z ,i %all aft]w>ds prove1 ?is cavity is m full1 or a m d5se body ( !r1 9 ! common s5se or acceptation ( ! ^w1 ?an gold is ( gold1 bulk = bulk2 & t because ! "o1 viz4 ! mass ( !r1 is all !r3 b ! mass ( gold1 :i* we conceive1 is n all gold2 b !re is an int]mixture1 & t va/ly m ?an is commonly suppos$1 ( !r ) x2 s t vacuity1 z x is commonly ?\ght1 or errone\sly suppos$1 is a m d5se body ?an ! gold z gold4 ,b if we consid] ! :ole cont5t ( ! "o ) t ( ! o!r1 )9 ! same or equal quantity ( expatiation1 !n are !y bo? equally conta9+ ! mat]ia or body4--,f ! ,po/hum\s ,works ( ,rob]t ,hooke1 ,m4,d41 ,f4,r4,s41 #agje1 pp4 #aga-b 7z copi$ 9 ,memoir ( ,dalton1 by ,angus ,smi?74 ,newton's contempor>ies did n excel 9 p[] ( cle> expression1 z he himself did2 b ,pr(essor ,poynt+ int]prets ?is s+ul> attempt at utt]ance ?us3--,all space is fill$ ) equally d5se mat]ia4 ,gold fills only a small fraction ( ! space assign$ to x1 & yet has a big mass4 ,h[ mu* great] mu/ be ! total mass fill+ t space4 ,! tacit assumption "h made is t ! p>ticles ( ! aggregate are all compos$ ( "o & ! same cont9u\s sub/ance1 --practically t matt] is made ( e!r2 & t assumption1 9 ,hooke's day1 mu/ h be5 only a speculation4 ,b x is ! k9d ( speculation :i* "t is ju/ify+1 x is ! k9d ( tru? :i* we all feel to be 9 process ( e/abli%m5t n[4#f ,we d n dep5d on t sort ( argum5t1 h[ev]2 :at we dep5d on is exp]im5tal measure ( ! mass1 & ma!matical e/imate ( ! volume1 ( ! electron4 ,= calculation %[s t h[ev] ! mass be acc\nt$ =--:e!r electro/atically or magnetically1 or hydrodynamically--! e/imate ( ratio ( mass to effective volume c diff] only 9 a num]ical coeffici5t1 & _c diff] z reg>ds ord] ( magnitude4 ,! only way out ( ?is conclusion w\ld be ! discov]y t ! negative electron is n ! real or ! ma9 matt]-unit1 b is only a subsidi>y +r$i5t2 :]eas ! ma9 mass is ! m bulky positive *>ge4 ,t la/ hypo!sis h[ev] is at pres5t too vague to be useful4 ,moreov]1 ! mass ( su* a *>ge w\ld 9 t case be unexpla9$1 & w\ld ne$ a fur!r /ep2 :i* w\ld probably l& u 9 mu* ! same sort ( e!rial d5sity z is involv$ 9 ! e/imate :i* ,i h bas$ on ! m famili> & tractable negative electron4 7,see ,app5dix #b47 ,x may be said :y assume any f9ite d5sity = ! e!r at all8 ,:y n assume t1 z x is inf9itely cont9u\s1 s x is inf9itely d5se--:atev] t may mean--& t all its prop]ties are inf9ite8 ,?is might be possible 7 x n = ! velocity ( light4 ,by transmitt+ waves at a f9ite & measurable spe$1 ! e!r has giv5 itself away1 & has let 9 all ! possibilities ( calculation & num]ical /atem5t4 ,its prop]ties are !reby exhibit$ z ess5tially f9ite--h[ev] inf9ite ! :ole ext5t ( x may turn out to be4 ,p>5!tically we may rem>k t gravitation has n yet exhibit$ any simil> k9d ( f9ite prop]ty2 & t is :y we "k s little ab\t x4 ,,e!rial ,,en]gy4 ,in/ead !n ( say+ t ! d5sity ( ! e!r is great1 ! cle>e/ mode ( expression is to say t ! d5sity ( matt] is small4 ,j z we c say t ! d5sity ( ! visible cosmos is small1 al?\gh 9 individual lumps its d5sity is comp>able to t ( iron or rock4 ,at ! risk ( repetition1 ,i h expla9$ ?is ov] aga91 because x is a matt] on :i* confusion may easily arise4 ,! really important ?+ ab\t e!r is n s mu* its d5sity1 consid]$ 9 itself1 z ! en]gy :i* t d5sity necess>ily involves1 on any k9etic !ory ( its ela/icity4 ,= x is n impossible--h[ev] hopeless x may seem n[--t a modicum ( t en]gy may "s day be p>tially utilis$4 ,"l ,kelv9's incipi5t k9etic !ory ( ela/icity is a complicat$ matt]1 & ,i w only briefly ent] ^u x4 ,b be=e do+ s1 ,i want to remove an objection :i* is sometimes felt1 z to ! fluid & easily p]meable "* ( a m$ium ( ?is great d5sity1--t is to say1 z to ! abs5ce ( friction or viscosity--! abs5ce ( resi/ance to bodies mov+ ?r\gh x4 ,z a matt] ( fact !re is no necess>y connexion :atev] betwe5 d5sity & viscosity4 ',d5sity' & ',viscosity' are entirely diff]5t ?+s2 &1 if !re is no fluid friction1 a fluid may h any d5sity y please )\t int]pos+ any ob/acle to con/ant velocity4 ,to accel]ation x does inde$ oppose an ob/acle1 b t appe>s z ess5tially a "p ( ! in]tia or massiv5ess ( ! mov+ body4 ,x contributes to its mom5tum2 &1 if ! fluid is ev]y:]e pres5t1 x is impossible to discrim9ate betwe51 or to treat sep>ately1 t "p ( ! in]tia :i* belongs to ! fluid displac$1 & t "p :i* belongs to ! body mov+ ?r\gh x1--except by !ory4 ,z = ! ela/icity ( ! e!r1 t is asc]ta9able at once f ! spe$ at :i* x transmits waves4 ,t spe$--! velocity ( light--is accurately kn[n1 #c #aj c5timetres p] second4 ,& ! ratio ( ! ela/icity or rigidity to ! d5sity is equal to ! squ>e ( ?is spe$2--t is to say1 ! ela/icity mu/ be #i #aj times ! d5sity2 or1 9 o!r words1 #aj ,c4,g4,s4 units4 ,t is an imm$iate consequ5ce ( ! e/imate ( d5sity & ! fact ( ! velocity ( light2 & if ! d5sity is admitt$1 ! o!r _c be conte/$4 ,b we mu/ g on to ask1 ,to :at is ?is rigidity due8 ,if ! e!r does n consi/ ( p>ts1 & if x is fluid1 h[ c x possess ! rigidity appropriate to a solid1 s z to transmit transv]se waves8 ,to answ] ?is we mu/ fall back ^u ,"l ,kelv9's k9etic !ory ( ela/icity3--t x mu/ be due to rotational motion--intimate f9e-gra9$ motion ?r\gh\t ! :ole e!rial region--motion n ( ! nature ( locomotion1 b circulation 9 clos$ curves1 return+ ^u itself1--vortex motion ( a k9d f> m f9ely gra9$ ?an any waves ( light or any atomic or ev5 electronic /ructure4 ,n[ if ! ela/icity ( any m$ium is to be ?us expla9$ k9etically1 x foll[s1 z a necess>y consequ5ce1 t ! spe$ ( ?is int]nal motion mu/ be comp>able to ! spe$ ( wave propagation2--t is to say t ! int]nal squirm+ circulation1 to :i* e "p ( ! e!r is subject1 mu/ be c>ri$ on ) a velocity ( ! same ord] ( magnitude z ! velocity ( light4 ,?is is ! !ory !n1--?is !ory ( ela/icity z dep5d5t on motion1--:i*1 9 comb9ation ) ! e/imate ( d5sity1 makes ! int]nal en]gy ( ! e!r s gigantic4 ,= 9 e cubic millimetre ( space we h1 accord+ to ?is view1 a mass equival5t to :at1 if x 7 matt]1 we %\ld call a ?\s& tons1 circulat+ int]nally1 e "p ( x1 ) a velocity comp>able to ! velocity ( light1 & !re=e conta9+--/or$ away 9 t small region ( space--an am\nt ( en]gy ( ! ord] #aj ergs1 or1 :at is ! same ?+1 #c #aj kil[att c5turies2 :i* is o!rwise expressible z equal to ! en]gy ( a million horse-p[] /ation work+ cont9u\sly = =ty million ye>s4 ,,summ>is$ ,,brief ,,/atem5ts ,,conc]n+ ,,! ,,e!r 7,z communicat$ by ! au?or to ! ,briti% ,association at ,leice/]1 #aijg74 #a4 ,! !ory t an electric *>ge mu/ possess ! equival5t ( in]tia 0 cle>ly e/abli%$ by ,j4,j4 ,?omson 9 ! ,philosophical ,magaz9e = ,april1 #ahha4 #b4 ,! discov]y ( masses small] ?an atoms 0 made exp]im5tally by ,j4,j4 ,?omson1 & communicat$ to ,section ,a at ,dov] 9 #ahii4 #c4 ,! !sis t ! corpuscles s discov]$ consi/$ :olly ( electric *>ges 0 su/a9$ by _m p1 & 0 cl9*$ by ! exp]im5ts ( ,kaufmann 9 #aijb4 #d4 ,! conc5tration ( ! ionic *>ge1 requir$ to give ! obs]v$ corpuscul> in]tia1 c be easily calculat$2 & consequ5tly ! size ( ! electric nucleus1 or electron1 is kn[n4 #e4 ,! old p]ception t a magnetic field is k9etic has be5 develop$ by ,kelv91 ,heaviside1 ,fitz,gerald1 ,hicks1 & ,l>mor1 mo/ ( :om h treat$ x z a fl[ along magnetic l9es2 ?\gh x may also1 p]haps equally well1 be reg>d$ z a fl[ p]p5dicul> to !m & along ! ,poynt+ vector4 ,! =m] doctr9e is su/a9$ by ,l>mor1 z 9 accordance ) ! pr9ciple ( ,lea/ ,action1 & ) ! absolutely /ation>y "* ( ! e!r z a :ole2 ! latt] view appe>s to be m consi/5t ) ! !ories ( ,j4,j4 ,?omson4 #f4 ,a *>ge 9 motion is well kn[n to be surr\nd$ by a magnetic field2 & ! en]gy ( ! motion c be express$ 9 t]ms ( ! en]gy ( ?is concomitant field1--:i* aga9 mu/ be acc\nt$ z ! k9etic en]gy ( e!re\s fl[4 #g4 ,putt+ ^! ?+s toge!r1 & consid]+ ! e!r z ess5tially incompressible--on ! /r5g? ( ! ,cav5di% electric exp]im5t1 ! facts ( gravitation1 & ! g5]al idea ( a connect+ cont9u\s m$ium--! au?or reckons t to deal ) ! e!r dynamically x mu/ be treat$ z hav+ a d5sity ( ! ord] #aj grammes p] cubic c5timetre4 7,see ,app5dix #b47 #h4 ,! exi/5ce ( transv]se waves 9 ! int]ior ( a fluid c only be expla9$ on gyro/atic pr9ciples1 i4e4 by ! k9etic or rotational ela/icity ( ,"l ,kelv94 ,& ! int]nal circulatory spe$ ( ! intr9sic motion ( su* a fluid mu/ be comp>able ) ! velocity ) :i* su* waves are transmitt$4 #i4 ,putt+ ^! ?+s toge!r1 x foll[s t ! intr9sic or con/itutional vortex en]gy ( ! e!r mu/ be ( ! ord] #aj ergs p] cubic c5timetre4 ,conclusion4--,?us e cubic millimetre ( ! univ]sal e!r ( space mu/ possess ! equival5t ( a ?\s& tons1 & e "p ( x mu/ be squirm+ int]nally ) ! velocity ( light4 ,,footnote3 #f ,x does n seem to h be5 notic$ t 9 ,qu]y #bb1 quot$ 9 ! ,introduction to ! pres5t book1 ,newton seems to ?r[ out a curi\s h9t 9 ?is same direction1--?\gh he imm$iately ab&ons x aga94 ,he does n appe> to h c>efully edit$ 8 qu]ies2 probably !y 7 publi%$ po/hum\sly4 ,,*apt] ,,viii ,,e!r ,,& ,,matt] ,,! ,,me*anical ,,necessity ,,= ,a ,,cont9u\s ,,m$ium ,,fill+ ,,space ,9 ?is *apt] ,i propose to summ>ise 9 simple & consecutive =m mo/ ( ! argum5ts already us$4 ,?irty ye>s ago ,cl]k ,maxwell gave to ! ,royal ,in/itution ( ,great ,brita9 a rem>kable address on ,action at a ,di/ance4 ,x is report$ 9 ! ,j\rnal ,r4,i41 ,vol4 ,,vii1 & to x ,i w\ld direct att5tion4 ,mo/ natural philosoph]s hold1 & h held1 t action at a di/ance across empty space is impossible2 9 o!r words1 t matt] _c act :]e x is n1 b only :]e x is4 ,! "q ,:]e is x8 is a fur!r "q t may dem& att5tion & require m ?an a sup]ficial answ]4 ,= x c be argu$ on ! hydrodynamic or vortex !ory ( matt]1 z well z on ! electrical !ory1 t e atom ( matt] has a univ]sal ?\gh ne>ly inf9itesimal preval5ce1 & ext5ds ev]y:]e2 s9ce !re is no def9ite %>p b\nd>y or limit+ p]iph]y to ! region di/urb$ by its exi/5ce4 ,! l9es ( =ce ( an isolat$ electric *>ge ext5d ?r\gh\t illimitable space4 ,& ?\gh a *>ge ( opposite sign w curve & conc5trate !m1 yet x is possible to deal ) bo? *>ges1 by ! me?od ( sup]position1 z if !y ea* exi/$ sep>ately )\t ! o!r4 ,9 t case1 !re=e1 h[ev] f> !y rea*1 su* nuclei cle>ly ex]t no action at a di/ance 9 ! te*nical s5se4 ,"s philosoph]s h reason to suppose t m9d c act directly on m9d )\t int]v5+ me*anism1--& sometimes t has be5 spok5 ( z g5u9e action at a di/ance2 b no prop] conception or physical model c be made ( su* a process1 nor is x cle> t space & di/ance h any p>ticul> mean+ 9 ! region ( psy*ology4 ,! l9ks betwe5 m9d & m9d may be some?+ q o!r ?an physical proximity2 & 9 d5y+ action at a di/ance across empty space ,i am n d5y+ telepa?y or o!r activities ( a non-physical k9d4 ,= al?\gh bra9 di/urbance is c]ta9ly physical1 & is an ess5tial concomitant ( m5tal action :e!r ( ! s5d+ or receiv+ v>iety1 yet we "k f ! case ( heat t a mat]ial movem5t c be excit$ 9 "o place at ! exp5se ( correspond+ movem5t 9 ano!r1 )\t any simil> k9d ( transmission or mat]ial connexion betwe5 ! two places3 ! ?+ t travels across vacuum is n heat4 ,9 all cases :]e physical motion is involv$1 h[ev]1 ,i w\ld h a m$ium s\ght =4 ,x may n be matt]1 b x mu/ be some?+2 !re mu/ be a connect+ l9k ( "s k9d1 or ! transf]5ce _c occur4 ,!re c be no attraction across really empty space4 ,& ev5 :5 a mat]ial l9k exi/s1 s t ! connexion is obvi\s1 ! explanation is n complete2 = :5 ! me*anism ( attraction is und]/ood1 x w be f\nd t a body really only moves because x is pu%$ by some?+ f beh9d4 ,! ess5tial =ce 9 nature is ! vis a t]go4 ,s :5 we h f\nd ! traces1 or discov]$ ! connect+ ?read1 we /ill run up aga9/ ! ^w cohesion2 & we ought to be ex]cis$ 9 our m9ds z to its ultimate mean+4 ,:y ! :ole ( a rod %\ld foll[1 :5 "o end is pull$1 is a matt] requir+ explanation2 & ! only explanation t c be giv5 involves1 9 "s =m or o!r1 a cont9u\s m$ium connect+ ! discrete & sep>at$ p>ticles or atoms ( matt]4 ,:5 a /eel spr+ is b5t or di/ort$1 :at is x t is really /ra9$8 ,n ! atoms--! atoms are only displac$2 x is ! connect+ l9ks t are /ra9$--! connect+ m$ium--! e!r4 ,di/ortion ( a spr+ is really di/ortion ( ! e!r4 ,all /ress exi/s 9 ! e!r4 ,matt] c only be mov$4 ,contact does n exi/ betwe5 ! atoms ( matt] z we "k !m2 x is d\btful if a piece ( matt] ev] t\*es ano!r piece1 any m ?an a comet t\*es ! sun :5 x appe>s to reb\nd f x2 b ! atoms are connect$1 z ! comet & ! sun are connect$1 by a cont9u\s pl5um )\t break or discont9uity ( any k9d4 ,matt] acts on matt] only ?r\gh ! e!r4 ,b :e!r matt] is a ?+ utt]ly di/9ct & sep>ate f ! e!r1 or :e!r x is a specifically modifi$ portion ( x--modifi$ 9 su* a way z to be susceptible ( locomotion & yet cont9u\s ) all ! re/ ( ! e!r1 :i* c be said to ext5d ev]y:]e f> beyond ! b\nds ( ! modifi$ & tangible portion--are que/ions dem&+1 & ,i may say 9 process ( receiv+1 answ]s4 ,e su* answ] involves "s view ( ! univ]sal & possibly inf9ite uni=m omnipres5t connect+ m$ium1 ! ,e!r ( space4 ,x has be5 said1 some:at s>ca/ically1 t ! e!r 0 made 9 ,engl&4 ,! /atem5t is only an exagg]ation ( ! tru?4 ,i might ev5 urge t x has be5 l>gely con/ruct$ 9 ! ,royal ,in/itution2 =1 ,i w summ>ise n[ ! *ief l9es ( evid5ce on :i* its exi/5ce is believ$ 91 & our k ( x is bas$4 ,fir/ ( all1 ,newton recognis$ ! ne$ ( a m$ium = expla9+ gravitation4 ,9 8 ,optical ,qu]ies he %[s t if ! pressure ( ?is m$ium is less 9 ! neighb\rhood ( d5se bodies ?an at great di/ances f !m1 d5se bodies w be driv5 t[>ds ea* o!r2 & t if ! dim9ution ( pressure is inv]sely z ! di/ance f ! d5se body1 ! law ( =ce w be ! inv]se squ>e law ( gravitation4 ,all t is requir$1 !re=e1 to expla9 gravity1 is a dim9ution ( pressure1 or increase ( t5sion1 caus$ by ! =mation ( a matt] unit--t is to say ( an electron or corpuscle4 ,& al?\gh we d n yet "k :at an electron is--:e!r x be a /ra9 c5tre1 or :at k9d ( s+ul>ity 9 ! e!r x may be--!re is no difficulty 9 suppos+ t a slight1 almo/ inf9itesimal1 /ra9 or attempt$ r>efaction %\ld be produc$ 9 ! e!r :5ev] an electron comes into be+--to be relax$ aga9 only on its resolution & de/ruction4 ,/rictly speak+ x is n a real /ra91 b only a /ress2 s9ce !re c be no actual yield1 b only a pull or t5sion1 ext5d+ 9 all directions t[>ds inf9ity4 ,! t5sion requir$ p] unit ( matt] is almo/ ludicr\sly small1 & yet 9 ! aggregate1 ne> su* a body z a planet1 x becomes enorm\s4 ,! =ce ) :i* ! moon is held 9 its orbit w\ld be great en\gh to te> asund] a /eel rod f\r hundr$ miles ?ick1 ) a t5acity ( #cj tons p] squ>e in*2 s t if ! moon & e>? 7 connect$ by /eel in/ead ( by gravity1 a =e/ ( pill>s w\ld be necess>y to :irl ! sy/em once a mon? r\nd _! common c5tre ( gravity4 ,su* a =ce necess>ily implies enorm\s t5sion or pressure 9 ! m$ium4 ,maxwell calculates t ! gravitational /ress ne> ! e>?1 :i* we mu/ suppose to exi/ 9 ! invisible m$ium1 is #cjjj times great] ?an :at ! /ronge/ /eel c\ld /&2 & ne> ! sun x %\ld be #bejj times z great z t4 ,! "q has aris5 9 my m9d1 :e!r1 if ! :ole s5sible univ]se--e/imat$ by ,"l ,kelv9 z equival5t to ab\t a ?\s& million suns--7 all conc5trat$ 9 "o body ( specifiable d5sity1#g ! /ress w\ld n be s great z to produce a t5d5cy t[>ds e!rial disruption2 :i* w\ld result 9 a dis9tegrat+ explosion1 & a scatt]+ ( ! p>ticles once m z an enorm\s nebula & o!r fragm5ts into ! dep?s ( space4 ,= ! t5sion w\ld be a maximum 9 ! int]ior ( su* a mass2 &1 if x rose to ! value #aj dynes p] squ>e c5timetre1 some?+ w\ld h to happ54 ,i d n suppose t ?is c be ! reason1 b "o w\ld ?9k !re mu/ be "s reason1 = ! scatt]$ condition ( gravitative matt]4 ,too little is kn[n1 h[ev]1 ab\t ! me*anism ( gravitation to enable u to adduce x z ! /ronge/ argum5t 9 support ( ! exi/5ce ( an e!r4 ,! olde/ valid & conclusive requisition ( an e!re\s m$ium dep5ds on ! wave !ory ( light1 "o ( ! f\nd]s ( :i* 0 ! ,royal ,in/itution ,pr(essor ( ,natural ,philosophy at ! beg9n+ ( la/ c5tury1 ,dr4 ,?omas ,"y4 ,no ord9>y matt] is capable ( transmitt+ ! undulations or tremors t we call light4 ,! spe$ at :i* !y g1 ! k9d ( undulation1 & ! facility ) :i* !y g ?r\gh vacuum1 =bid ?is4 ,s cle>ly & univ]sally has x be5 p]ceiv$ t waves mu/ be waves ( some?+--some?+ di/9ct f ord9>y matt]--t ,"l ,salisbury1 9 8 presid5tial address to ! ,briti% ,association at ,ox=d1 criticis$ ! e!r z little m ?an a nom9ative case to ! v]b to undulate4 ,x is truly t1 ?\gh x is also truly m ?an t2 b to illu/rate t lum9if]\s aspect ( x1 ,i w quote a p>agraph f ! lecture ( ,cl]k ,maxwell's to :i* ,i h already ref]r$3-- ,! va/ int]planet>y & int]/ell> regions w no long] be reg>d$ z wa/e places 9 ! univ]se1 :i* ! ,creator has n se5 fit to fill ) ! symbols ( ! manifold ord] ( ,8 k+dom4 ,we %all f9d !m to be already full ( ?is wond]ful m$ium2 s full1 t no human p[] c remove x f ! smalle/ portion ( space1 or produce ! slighte/ flaw 9 its inf9ite cont9uity4 ,x ext5ds unbrok5 f /> to />2 & :5 a molecule ( hydrog5 vibrates 9 ! dog-/>1 ! m$ium receives ! impulses ( ^! vibrations1 & aft] c>ry+ !m 9 its imm5se bosom = sev]al ye>s1 deliv]s !m1 9 due c\rse1 regul> ord]1 & full tale1 into ! spectroscope ( ,mr4 ,hugg9s1 at ,tulse ,hill4 ,?is w suffice to emphasise ! fact t ! eye is truly an e!rial s5se-organ--! only "o :i* we possess1 ! only mode by :i* ! e!r is enabl$ to appeal to u2 & t ! detection ( tremors 9 ?is m$ium--! p]ception ( ! direction 9 :i* !y g1 & "s inf]5ce z to ! quality ( ! object :i* has emitt$ !m--cov] all t we mean by sight & see+4 ,i pass !n to ano!r function1 ! electric & magnetic ph5om5a display$ by ! e!r2 & on ?is ,i w only p]mit myself a v %ort quotation f ! writ+s ( ,f>aday1 ^: :ole life may be said to h be5 direct$ t[>ds a bett] und]/&+ ( ^! e!re\s ph5om5a4 ,inde$ ! /atue 9 ! entrance hall ( ! ,royal ,in/itution1 ,albem>le ,/reet1 may be consid]$ z ! /atue ( ! discov]] ( ! electric & magnetic prop]ties ( ! ,e!r ( space4 ,f>aday conjectur$ t ! same m$ium :i* is conc]n$ 9 ! propagation ( light might also be ! ag5t 9 electromagnetic ph5om5a4 ,= my own "p1 he says1 consid]+ ! relation ( a vacuum to ! magnetic =ce1 & ! g5]al "* ( magnetic ph5om5a ext]nal to ! magnet1 ,i am mu* m incl9$ to ! notion t 9 ! transmission ( ! =ce !re is su* an action1 ext]nal to ! magnet1 ?an t ! effects are m]ely attraction & repulsion at a di/ance4 ,su* an action may be a function ( ! !r2 = x is n unlikely t1 if !re be an !r1 x %\ld h o!r uses ?an simply ! conveyance ( radiation4 ,?is conjecture has be5 amply /r5g!n$ by subsequ5t inve/igations4 ,"o m function is n[ be+ discov]$2 ! e!r is be+ f\nd to con/itute matt]--an imm5sely int]e/+ topic1 on :i* !re are _m active work]s at ! pres5t "t4 ,i w make a brief quotation f ,pr(essor ,sir ,j4,j4 ,?omson1 :]e he summ>ises ! conclusion :i* we all see loom+ be=e u1 ?\gh x has n yet be5 completely atta9$1 & w\ld n by all be simil>ly express$3-- ,! :ole mass ( any body is j ! mass ( e!r surr\nd+ ! body :i* is c>ri$ along by ! ,f>aday tubes associat$ ) ! atoms ( ! body4 ,9 fact1 all mass is mass ( ! e!r2 all mom5tum1 mom5tum ( ! e!r2 & all k9etic en]gy1 k9etic en]gy ( ! e!r4 ,?is view1 x %\ld be said1 requires ! d5sity ( ! e!r to be imm5sely great] ?an t ( any kn[n sub/ance4 ,yes1 f> d5s]--s d5se t matt] by comp>ison is l gossam]1 or a filmy imp]ceptible mi/1 or a milky way4 ,n unreal or unimportant1--a cobweb is n unreal1 nor to c]ta9 creatures is x unimportant1 b x _c be said to be massive or d5se2 & matt]1 ev5 plat9um1 is n d5se :5 comp>$ ) ! e!r4 ,n till la/ ye>1 h[ev]1 did ,i realise :at ! d5sity ( ! e!r mu/ really be1#h comp>$ ) t modification ( x :i* appeals to our s5ses z matt]1 & :i* = t reason engrosses our att5tion4 ,is !re any o!r function possess$ by ! e!r1 :i*1 ?\gh n yet discov]$1 may lie )9 ! b\nds ( possibility = future discov]y8 ,i believe !re is1 b x is too speculative to ref] to1 beyond say+ t x has be5 urg$ z probable by ! au?ors ( ,! ,unse5 ,univ]se1 & has be5 ?us t5tatively ref]r$ to by ,cl]k ,maxwell3-- ,:e!r ?is va/ homog5e\s expanse ( isotropic matt] is fitt$ n only to be a m$ium ( physical int]action betwe5 di/ant bodies1 & to fulfil o!r physical functions ( :i*1 p]haps1 we h z yet no conception1 b also 444 to con/itute ! mat]ial organism ( be+s ex]cis+ functions ( life & m9d z high or high] ?an ours are at pres5t--is a "q f> transc5d+ ! limits ( physical speculation4 ,& !re = ! pres5t ,i leave t aspect ( ! subject4 ,e!r & ,matt]4 ,i %all n[ attempt to illu/rate "s relations betwe5 e!r & matt]4 ,! "q is (t5 ask$1 is e!r mat]ial8 ,?is is l>gely a "q ( words & conv5i5ce4 ,und\bt$ly1 ! e!r belongs to ! mat]ial or physical univ]se1 b x is n ord9>y matt]4 ,i %\ld pref] to say x is n matt] at all4 ,x may be ! sub/ance or sub/ratum or mat]ial ( :i* matt] is compos$1 b x w\ld be confus+ & inconv5i5t n to be able to discrim9ate betwe5 matt] on ! "o h&1 & e!r on ! o!r4 ,if y tie a knot on a bit ( /r+1 ! knot is compos$ ( /r+1 b ! /r+ is n compos$ ( knots4 ,if y h a smoke or vortex-r+ 9 ! air1 ! vortex-r+ is made ( air1 b ! atmosph]e is n a vortex-r+2 & x w\ld be only confus+ to say t x 04 ,! ess5tial di/9ction betwe5 matt] & e!r is t matt] moves1 9 ! s5se t x has ! prop]ty ( locomotion & c effect impact & bomb>dm5t2 :ile e!r is /ra9$1 & has ! prop]ty ( ex]t+ /ress & recoil4 ,all pot5tial en]gy exi/s 9 ! e!r4 ,x may vibrate1 & x may rotate1 b z reg>ds locomotion x is /ation>y--! mo/ /ation>y body we "k3 absolutely /ation>y1 s to speak2 our /&>d ( re/4 ,all t we ourselves c effect1 9 ! mat]ial univ]se1 is to alt] ! motion & configuration ( masses ( matt]2 we c move matt]1 by our muscles1 & t is all we c d directly3 ev]y?+ else is indirect4 ,b n[ comes ! "q1 h[ is x possible = matt] to be compos$ ( e!r8 ,h[ is x possible = a solid to be made out ( fluid8 ,a solid possesses ! prop]ties ( rigidity1 imp5etrability1 ela/icity1 & su*-l2 h[ c ^! be imitat$ by a p]fect fluid su* z ! e!r mu/ be8 ,! answ] is1 !y c be imitat$ by a fluid 9 motion2 a /atem5t :i* we make ) confid5ce z ! result ( a great "p ( ,"l ,kelv9's "w4 ,x may be illu/rat$ by a few exp]im5ts4 ,a :eel ( spokes1 transp>5t or p]meable :5 /ation>y1 becomes opaque :5 revolv+1 s t a ball ?r[n aga9/ x does n g ?r\gh1 b reb\nds4 ,! motion only affects p]meability to matt]2 transp>5cy to light is unaffect$4 ,a silk cord hang+ f a pulley becomes rigid & visc\s :5 put into rapid motion2 & pulses or waves :i* may be g5]at$ on ! cord travel along x ) a spe$ equal to its own velocity1 :atev] t velocity may be1 s t !y appe> to /& /ill4 ,?is is a g5u9e case ( k9etic rigidity2 & ! fact t ! wave-transmission velocity is equal to ! rotatory spe$ ( ! mat]ial1 is typical & important1--= 9 all cases ( k9etic ela/icity ^! two velocities are ( ! same ord] ( magnitude4 ,a flexible *a91 set sp9n+1 c /& up on end :ile ! motion cont9ues4 ,a jet ( wat] at suffici5t spe$ c be /ruck ) a hamm]1 & resi/s be+ cut ) a sword4 ,a sp9n+ disk ( pap] becomes ela/ic l flexible metal1 & c act l a circul> saw4 ,sir ,william ,:ite tells me t 9 naval con/ruction /eel plates are cut by a rapidly revolv+ disk ( s(t iron4 ,a vortex-r+1 eject$ f an elliptical orifice1 oscillates ab\t ! /able circul> =m1 z an india-rubb] r+ w\ld d2 ?us furni%+ a beautiful example ( k9etic ela/icity1 & %[+ u cle>ly a fluid display+ "s ( ! prop]ties ( a solid4 ,a /ill fur!r example is ,"l ,kelv9's model ( a spr+ balance1 made ( no?+ b rigid bodies 9 sp9n+ motion4#i ,?is arrangem5t utilises ! processional movem5t ( balanc$ gyro/ats--conceal$ 9 a case & support+ a book--to imitate ! behavi\r ( a spiral spr+1 if x 7 us$ to support ! same book4 ,if ! e!r c be set sp9n+1 !re=e1 we may h "s hope ( mak+ x imitate ! prop]ties ( matt]1 or ev5 ( con/ruct+ matt] by its aid4 ,b h[ are we to sp9 ! e!r8 ,matt] alone seems to h no grip ( x4 ,z already describ$1 ,i h spun /eel disks1 a y>d 9 diamet]1 #djjj times a m9ute1 h s5t light r\nd & r\nd betwe5 !m1 & te/$ c>efully = ! slighte/ effect on ! e!r4 ,n ! slighte/ effect 0 p]ceptible4 ,we _c sp9 e!r me*anically4 ,b we c vibrate x electrically2 & e s\rce ( radiation does t4 ,an electrical *>ge1 9 suffici5tly rapid vibration1 is ! only s\rce ( e!r-waves t we "k2 & if an electric *>ge is sudd5ly /opp$1 x g5]ates ! pulses kn[n z ,x-rays1 z ! result ( ! collision4 ,n spe$1 b sudd5 *ange ( spe$1 is ! necess>y condition = g5]at+ waves 9 ! e!r by electricity4 ,we c also inf] "s k9d ( rot>y motion 9 ! e!r2 ?\gh we h no su* obvi\s means ( detect+ ! sp9 z is furni%$ by vision = detect+ "s k9ds ( vibration4 ,rotation is suppos$ to exi/ :5ev] we put a *>ge into ! neighb\rhood ( a magnetic pole4 ,r\nd ! l9e jo9+ ! two1 ! e!r is sp9n+ l a top4 ,i d n say x is sp9n+ fa/3 t is a "q ( its d5sity2 x is 9 fact sp9n+ ) excessive sl[ness1 b x is sp9n+ ) a def9ite mom5t ( mom5tum4 ,j4,j4 ,?omson's !ory makes its mom5t ( mom5tum exactly equal to e m1 ! product ( *>ge & pole2 ! *>ge be+ measur$ electro/atically & ! pole magnetically4 ,h[ c ?is be %[n exp]im5tally8 ,suppose we _h a sp9n+ top enclos$ 9 a case1 s t ! sp9 0 unrecognisable by ord9>y means--x c\ld be detect$ by its gyro/atic behavi\r to =ce4 ,if all[$ to precess x w respond by mov+ p]p5dicul>ly to a deflect+ =ce4 ,s x is ) ! *>ge & ! magnetic pole4 ,try to move ! *>ge sudd5ly1 & x imm$iately sets (f at "r angles4 ,a mov+ *>ge is a curr5t1 & ! pole & ! curr5t try to revolve r\nd "o ano!r2--a fact :i* may be reg>d$ z exhibit+ a true gyro/atic action due to ! o!rwise unrecognisable e!rial sp94 ,! fact ( su* magnetic rotation 0 discov]$ by ,f>aday4 ,i "k t x is usually work$ out 9 ano!r way1 9 t]ms ( l9es ( =ce & ! re/ ( ! circuit2 b ,i am ?9k+ ( a curr5t z a /ream ( project$ *>ges2 & no "o way ( reg>d+ su* a matt] is likely to exhau/ ! tru?1 or to exclude o!r modes :i* are equally valid4 ,anyh[1 9 :atev] way x is reg>d$1 x is an example ( ! ?ree rectangul> vectors4 ,! ?ree vectors at "r angles to ea* o!r1 :i* may be labell$ ,curr5t1 ,magnetism1 & ,motion respectively1 or m g5]ally ,e1 ,h1 & ,v1 repres5t ! q fundam5tal relation betwe5 e!r & matt]1 & con/itute ! l9k betwe5 ,electricity1 ,magnetism1 & ,me*anics4 ,:]e any two ( ^! are pres5t1 ! ?ird is a necess>y consequ5ce4 ,?is pr9ciple is ! basis ( all dynamos1 ( electric motors1 ( light1 ( telegraphy1 & ( mo/ o!r ?+s4 ,inde$1 x is a "q :e!r x does n und]lie ev]y?+ t we "k 9 ! :ole ( ! physical sci5ces2 & :e!r x is n ! basis ( our conception ( ! ?ree dim5sions ( space4 ,la/ly1 we h ! fundam5tal prop]ty ( matt] call$ in]tia1 :i* c1 to a c]ta9 ext5t1 be expla9$ electromagnetically1 provid$ ! e!re\s d5sity is grant$ z ( ! ord] #aj grammes p] cubic c5timetre4 ,! ela/icity ( ! e!r w\ld !n h to be ( ! ord] #aj c4g4s42 & if ?is is due to intr9sic turbul5ce1 ! spe$ ( ! :irl+ or rotational ela/icity mu/ be ( ! same ord] z ! velocity ( light4 ,?is foll[s hydrodynamically2 9 ! same sort ( way z ! spe$ at :i* a pulse travels on a flexible runn+ endless cord1 ^: t5sion is entirely due to ! c5trifugal =ce ( ! motion1 is precisely equal to ! velocity ( ! cord itself4 ,& s1 on our pres5t view1 ! intr9sic en]gy ( con/itution ( ! e!r is incr$ibly & port5t\sly great2 e cubic millimetre ( space possess+ :at1 if x 7 matt]1 w\ld be a mass ( a ?\s& tons1 & an en]gy equival5t to ! output ( a million-horse-p[] /ation = #dj million ye>s4 ,! univ]se we are liv+ 9 is an extraord9>y "o2 & our inve/igation ( x has only j begun4 ,we "k t matt] has a psy*ical significance1 s9ce x c con/itute bra91 :i* l9ks toge!r ! physical & ! psy*ical worlds4 ,if any "o ?9ks t ! e!r1 ) all its massiv5ess & en]gy1 has probably no psy*ical significance1 ,i f9d myself unable to agree ) him4 ,,footnotes3 #g ,on do+ ! ari?metic1 h[ev]1 ,i f9d ! necess>y conc5tration absurdly great1 %[+ t su* a mass is q insuffici5t4 7,see ,app5dix #a47 #h ,see ,lodge1 ,philosophical ,magaz9e1 ,april1 #aijg4 ,also ,app5dix #b bel[4 #i ,address to ,section ,a ( ,briti% ,association at ,montreal1 #ahhd4 ,,*apt] ,,ix ,,/r5g? ,,( ,,! ,,e!r ,to %[ t ! e!r _c be ! slight & r>efi$ sub/ance :i* at "o "t1 & inde$ until q lately1 x 0 ?\ght to be1 x is useful to rememb] t n only has x to be ! vehicle ( light & ! m$ium ( all electric & magnetic influ5ce1 b also t x has to transmit ! trem5d\s =ces ( gravitation4 ,among small bodies gravitational =ces are slight1 & are altoge!r exce$$ by magnetic & electric or *emical =ces4 ,inde$ gravitational attraction betwe5 bodies ( a c]ta9 smallness c be m ?an c\nt]balanc$ ev5 by ! pressure :i* _! mutual radiation ex]ts--almo/ inf9itesimal ?\gh t is2--s t z a matt] ( fact1 small en\gh bodies ( any w>m? w repel ea* o!r unless !y are 9 an enclosure ( con/ant temp]ature1 i4e4 unless ! radiation pressure ^u !m is uni=m all r\nd4 ,! size at :i* radiation repulsion ov]-balances gravitational attraction1 = equal sph]es1 dep5ds on ! temp]ature ( ! sph]es & on _! d5sity2 b at ! ord9>y temp]ature to :i* we are accu/om$1 say #fj ,fahr5heit or !reab\ts1 equality betwe5 ! two =ces w obta9 = two wood5 sph]es 9 space if ea* is ab\t a foot 9 diamet]2 accord+ to ,pr(essor ,poynt+'s data 7,philosophical ,transactions1 ,vol4 #bjb1 p4 #eda74 ,= small] or hott] bodies1 radiation repulsion ov]p[]s mutual gravitation2 & x increases ) ! f\r? p[] ( _! absolute temp]ature4 ,! gravitational attractive =ce betwe5 p>ticles is exce$+ly small2 & t betwe5 two atoms or two electrons is negligibly small1 ev5 ?\gh !y be )9 molecul> di/ance ( ea* o!r4 ,= in/ance1 two atoms (1 say1 gold1 at molecul> di/ance1 attract ea* o!r gravitationally ) a =ce ( ! ord] 7#aj x #aj7 _/ 7#aj7 #aj _/ #aj x #aj #aj dyne2 :i* w\ld cause no p]ceptible accel]ation at all4 ,! gravitational attraction ( two electrons at ! same di/ance is ! =ty-?\s&-million? "p ( ?is1 & s "o w\ld ?9k mu/ be entirely negligible4 ,& yet x is to ! aggregate attraction ( myriads ( su* bodies t ! resultant =ce ( attraction is due2--a =ce :i* is felt ov] millions ( miles4 ,! =ce is n only felt inde$1 b mu/ be reckon$ z "o ( prodigi\s magnitude4 ,:5 deal+ ) bodies ( a/ronomical size1 ! =ce ( gravitation ov]p[]s all o!r =ces2 & all electric & magnetic attractions s9k by comp>ison into insignificance4 ,^! imm5se =ces mu/ be transmitt$ by ! e!r1 & x is in/ructive to consid] _! am\nt4 ,,"s ,,a/ronomical ,,=ces ,,:i* ,,! ,,e!r ,,has ,,to ,,transmit4 ,ari?metical ,calculation ( ! ,pull ( ! ,e>? on ! ,moon4 ,! mass ( ! e>? is #fjjj trillion 7#f #aj7 tons4 ,! mass ( ! moon is #a_/hj? t ( ! e>?4 ,t]re/rial gravity at ! moon's di/ance 7:i* is #fj e>? radii7 mu/ be r$uc$ 9 ! ratio #a3fj2 t is1 x mu/ be #a_/cfjj? ( :at x is "h4 ,consequ5tly ! pull ( ! e>? on ! moon is #f #aj _/ #hj #cfjj tons weight4 ,a pill> ( /eel :i* c\ld transmit ?is =ce1 provid$ x c\ld su/a9 a t5sion ( #dj tons to ! squ>e in*1 w\ld h a diamet] ( ab\t #djj miles2 z /at$ 9 ! text1 page #ajb4 ,if ?is =ce 7 to be transmitt$ by a =e/ ( weightless pill>s ea* a squ>e foot 9 cross-section1 ) a t5sion ( #cj tons to ! squ>e in* ?r\gh\t1 !re w\ld h to be #e million million ( !m4 ,ari?metical ,calculation ( ! ,pull ( ! ,sun on ! ,e>?4 ,! mass ( ! e>? is #f #aj tons4 ,! int5sity ( sol> gravity at ! sun's surface is #be times ord9>y t]re/rial gravity4 ,at ! e>?'s di/ance1 :i* is ne>ly #bjj sol> radii1 sol> gravity w be r$uc$ 9 ! ratio ( #a3bjj squ>$4 ,h5ce ! =ce ex]t$ by ! sun on ! e>? is 7#be #f #aj7_/7bjj7 tons weight4 ,t is to say1 x is approximately equal to ! weight ( #cg #aj ord9>y tons ^u ! e>?'s surface4 ,n[ /eel may readily be f\nd :i* c /& a load ( #cg tons to e squ>e in* ( cross-section4 ,! cross-section ( a b> ( su* /eel1 compet5t to transmit ! sun's pull to ! e>?1 w\ld !re=e h to be #aj squ>e in*es1 or say #gjj #aj squ>e feet4 ,& ?is is equival5t to a million million r\nd rods or pill>s ea* #cj feet 9 diamet]4 ,h5ce ! /atem5t 9 ! text 7page #bf7 is well )9 ! m>k4 ,! ,pull ( ! ,e>? on ! ,sun4 ,! pull ( ! e>? on ! sun is1 ( c\rse1 equal & opposite to ! pull ( ! sun on ! e>?1 :i* has j be5 calculat$2 b x furni%es ano!r mode ( arriv+ at ! result1 & may be reg>d$ z involv+ simpl] data--i4e4 data m g5]ally kn[n4 ,all we ne$ say is ! foll[+3-- ,! mass ( ! ,sun is #caf1jjj times t ( ! ,e>?4 ,! mean di/ance ( ! sun is1 say1 #bc1jjj e>? radii4 ,h5ce ! weight or pull ( ! sun by ! e>? is #cafjjj_/7bcjjj7 #f #aj tons weight4 ,9 o!r words1 x is approximately equal to ! ord9>y comm]cial weight ( #cf #aj tons1 z already calculat$4 ,! ,c5tripetal ,=ce act+ on ! ,e>?4 ,yet ano!r me?od ( calculat+ ! sun's pull is to express x 9 t]ms ( ! c5trifugal =ce ( ! e>?2 namely1 its mass1 multipli$ by ! squ>e ( its angul> velocity1 multipli$ by ! radius ( its orbit2--t is to say1 ,f ,m 7#b_/,t7 r :]e ,t is ! l5g? ( a ye>4 ,! process ( evaluat+ ?is is in/ructive1 ow+ to ! manipulation ( units :i* x involves3-- ,f #f x #aj tons x 7#d x #ib x #aj miles7_/7#cfe days7 :i* ( c\rse is a mass multipli$ by an accel]ation4 ,! accel]ation is-- 7#dj x #ib x #aj7_/acccjj x 7#bd7 miles p] h\r p] h\r 7#cfhj x #aj x #ebhj7_/acccjj x #egf x 7#cfjj7 feet p] sec4 p] sec4 7#aae x #ebhj7_/acccjj x #egf x #abif feet p] sec4 p] sec4 g_/#afdj ,h5ce ! ,=ce ( attraction is t :i*1 appli$ to ! e>?'s mass1 produces 9 x an accel]ation equal to ! #a_/afdj? "p ( :at ord9>y t]re/rial gravity c produce 9 fall+ bodies2 or ,f #f #aj tons g_/#afdj #f_/afdj x #aj tons weight2 :i* is ! ord9>y weight ( #cg #aj tons1 z be=e4 ,! slight num]ical discrepancy betwe5 ! above results is ( c\rse due to ! approximate "* ( ! data select$1 :i* are tak5 9 r\nd numb]s z q suffici5t = purposes ( illu/ration4 ,if we imag9e ! =ce appli$ to ! e>? by a =e/ ( r\nd rods1 "o = e squ>e foot ( ! e>?'s surface--i4e4 ( ! project$ e>?'s hemisph]e or area ( equatorial plane1--! =ce transmitt$ by ea* w\ld h to be #bgjj tons2 & !re=e1 if ( #cj-ton /eel1 !y w\ld ea* h to be elev5 in*es 9 diamet]1 or ne>ly 9 contact1 all ov] ! e>?4 ,pull ( a ,planet on ! ,e>?4 ,:ile we are on ! subject1 x seems int]e/+ to record ! fact t ! pull ( any planet on ! e>?1 ev5 ,neptune1 di/ant ?\gh x is1 is /ill a gigantic =ce4 ,! pull ( ,neptune is #a_/bj1jjj? ( ! sun's pull3 i4e4 x is #ah billion tons weight4 ,pull ( a ,/> on ! ,e>?4 ,on ! o!r h&1 ! pull ( a fix$ />1 l ,sirius--say a />1 = example1 :i* is #bj times ! mass ( ! sun & #bd light ye>s di/ant--is comp>atively v small4 ,x is easily f\nd by divid+ #bj times ! sun's pull by ! squ>$ ratio ( #bd ye>s to #h m9utes2 & x comes out z #cj million tons weight4 ,su* a =ce is able to produce no p]ceptible effect4 ,! accel]ation x causes 9 ! e>? & ! :ole sol> sy/em1 at its pres5t spe$ ?r\gh space1 is only able to curve ! pa? ) a radius ( curvature ( l5g? ?irty ?\s& times ! di/ance ( ! />4 ,=ce requir$ to hold toge!r ! ,compon5ts ( "s ,d\ble ,/>s4 ,b x is n to be suppos$ t ! transmission ( any ( ^! =ces gives ! e!r ! slighte/ tr\ble1 or /ra9s x to any:]e ne> ! limits ( its capacity4 ,su* =ces mu/ be transmitt$ ) p]fect ease1 = !re are pl5ty ( cases :]e ! =ce ( gravitation is va/ly great] ?an t4 ,9 ! case ( d\ble />s1 = in/ance1 two suns are :irl+ r\nd ea* o!r2 & "s ( !m are :irl+ rem>kably fa/4 ,9 su* cases ! =ce hold+ ! compon5ts toge!r mu/ be enorm\s4 ,p]haps ! mo/ /rik+ case1 = :i* we h sub/antially accurate data1 is ! /> ,aurig2 :i*1 dur+ ! g5]al spectroscopic survey ( ! heav5s und]tak5 by ,pr(essor ,pick]+ ( ,h>v>d1 9 connexion ) ! ,drap] ,memorial1 0 discov]$ to %[ a spectrum ) ! l9es "s days d\ble & alt]nate days s+le4 ,cle>ly x mu/ consi/ ( a pair ( lum9\s objects revolv+ 9 a plane approximately conta9+ ! l9e ( vision2 ! revolution be+ complet$ e f\r days4 ,= ! l9es w !n be optically displac$ by ! motion1 dur+ "p ( ! orbit--^? ( ! advanc+ body to ! "r1 ^? ( ! rec$+ body to ! left1--:ile 9 t "p ( ! orbit :i* lies a?w>t ! direction ( vision1 ! spectrum l9es w return to _! prop] places1--op5+ out aga9 to a maximum1 9 ! opposite direction1 at ! next quadrant4 ,! am\nt ( displacem5t c be r\ghly e/imat$1 enabl+ u to calculate ! spe$ ) :i* ! s\rces ( light 7 mov+4 ,pr(essor ,pick]+1 9 a brief /atem5t 9 ,nature1 ,vol4 ,,xli1 page #djc1 #ahhi1 says t ! velocity am\nts to ab\t #aej miles p] second1 & t x is r\ghly ! same = bo? compon5ts4 ,tak+ ^! data3-- ,equality & uni=mity ( spe$s1 #aej miles p] second ea*1 ,p]iod #d days1 we h all ! data necess>y to det]m9e ! masses2 & likewise ! gravitative pull betwe5 !m4 ,= ! /> mu/ consi/ ( two equal bodies1 revolv+ ab\t a common c5tre ( gravity midway betwe5 !m1 9 ne>ly circul> orbits4 ,! spe$ & p]iod toge!r easily give ! radius ( ! circul> orbit z ab\t #h million miles4 ,equat+ c5trifugal & c5tripetal =ces mv _/ r m _/ 7#br7 & comp>+ ! value ( #dr _/ ,t s obta9$ ) ! r _/ ,t ( ! e>?1 we f9d ! mass ( ea* body mu/ be ab\t #cj1jjj times t ( ! e>?1 or ab\t #a_/aj? t ( ! sun4 99 99 99 99 99 7,?is is treat+ !m z sph]es1 ?\gh !y mu/ really be pull$ into decid$ly prolate %apes4 ,inde$ x may seem surpris+ t ! fur!r portions c keep up ) ! ne>] portions z !y revolve4 ,if !y are ( some?+ l sol> d5sity _! diamet] w be comp>able to half a million miles1 & ! natural p]iods ( _! ne> & f> portions w diff] 9 ! ratio 7#ag_/af7c_/b #aa approximately4 ,t5acity c\ld n hold ! p>ts toge!r1 b gravitational coh]5ce w\ld47 99 99 99 99 99 ,?is1 h[ev]1 is a digression4 ,let u cont9ue ! calculation ( ! gravitative pull4 ,we h masses ( #c #aj #f #aj tons1 revolv+ ) angul> velocity #b #d days1 9 a circle ( radius #h #aj miles4 ,consequ5tly ! c5tripetal accel]ation is #d #h #aj _/ #af miles p] day p] day2 :i* comes out #cb _/ #bb ft4 p] sec4 p] sec41 or ne>ly half ord9>y t]re/rial gravity4 ,consequ5tly ! pull betwe5 ! two compon5ts ( ! d\ble /> ,aurig is g _/ #b4b #ah #aj tons1 or equal to ! weight ( #hj #aj tons on ! e>?1 :i* is m ?an tw5ty million times z great z is ! pull betwe5 ! e>? & our sun4 99 99 99 99 99 ,simple calculations su* z ^! c\ld h be5 made at any "t2 !re is no?+ novel ab\t !m1 z !re is ab\t ! e/imate ( ! e!r's d5sity & va/ intr9sic en]gy1 9 ,*apt]s ,,vi & ,,vii4 ,b !n !re is no?+ hypo!tical or unc]ta9 ab\t !m ei!r2 !y are c]ta9 & def9ite3 :]eas x may be ?\ght !re is some?+ d\btful ab\t ! new] cont5tions :i* involve consid]ation ( ! mass & size ( electrons & ( ! uni=m & incompressible "* ( e!rial con/itution4 ,ev5 ! idea ( massiv5ess z appli$ to ! e!r involves an elem5t ( unc]ta9ty1 or ( figurativ5ess2 because until we "k m ab\t e!r's peculi> nature 7if x is peculi>71 we h to deal ) x 9 accordance ) mat]ial analogies1 & mu/ specify its massiv5ess z t :i* w\ld h to be possess$ by x if x fulfill$ its functions & yet 7 any?+ l ord9>y matt]4 ,x _c really be ord9>y matt]1 because ord9>y matt] is def9itely diff]5tiat$ f x1 & is presumably compos$ ( x2 b ! in]tia ( ord9>y matt]1 h[ev] x be electrically or magnetically expla9$1 mu/ 9 ! la/ resort dep5d on some?+ p>5tally ak9 to in]tia 9 ! fundam5tal sub/ance :i* fills space4 ,& ?is x is :i* we h attempt$ 9 ,*apt]s ,,vi & ,,vii to evaluate & to express 9 ! sob]e/ t]ms possible4 ,,*apt] ,x ,,g5]al ,,!ory ,,( ,,ab]ration ,9 ,*apt] ,,iii ! subject ( ,ab]ration 0 treat$ 9 a simple & geometrical mann]1 b x is n[ "t to deal ) x m g5]ally4 ,& to d ?is compactly ,i mu/ be cont5t 9 ! great] "p ( ?is *apt] to appeal *iefly to physici/s4 ,! foll[+ g5]al /atem5ts conc]n+ ab]ration c be made3-- #a4 ,a ray ( light 9 cle> space is /raight1 :atev] ! motion ( ! m$ium1 unless eddies exi/2 9 o!r words1 no irrotational di/urbance ( e!r c deflect a ray4 #b4 ,b if ! obs]v] is 9 motion1 ! app>5t ray w n be ! true ray1 & 8 l9e ( vision w n truly indicate ! direction ( an object4 #c4 ,9 a /ation>y e!r ! ray co9cides ) wave-normal4 ,9 a mov+ e!r ! ray & wave-normal enclose an ab]ration angle 1 su* t s9 v_/,v1 ! ratio ( ! e!r spe$ to ! light spe$4 #d4 ,9 all cases ! l9e ( vision dep5ds on motion ( ! obs]v]1 & on t alone4 ,if ! obs]v] is /ation>y1 8 l9e ( vision is a ray4 ,if he moves at ! same rate z ! e!r1 8 l9e ( vision is a wave-normal4 #e4 ,l9e ( vision dep5ds n at all on ! motion ( ! e!r1 s long z x has a velocity-pot5tial4 ,h5ce if ?is condition is satisfi$ ! !ory ( ab]ration is q simple4 ,g5]al ,/atem5t z to ,negative ,results 9 ! ,subject4 ,x is notewor?y t almo/ all ! obs]vations :i* h be5 made ) negative results z to ! effect ( ! ,e>?'s orbital motion on ! e!r are equally consi/5t ) complete connexion & complete indep5d5ce betwe5 e!r & matt]4 ,if !re is complete connexion1 ! e!r ne> ! e>? is relatively /agnant1 & negative t]re/rial results are natural4 ,if !re is complete indep5d5ce1 ! e!r is ei!r absolutely /ation>y or has a velocity-pot5tial1 & ! negative results are1 z has be5 %[n1 !reby expla9$4 ,direct exp]im5t on ! subject ( e!rial viscosity proves t t is ei!r really or approximately z]o1 & sub/antiates ! indep5d5ce explanation4 ,def9ition ( a ,ray4 ,a ray signifies ! pa? ( a def9ite or id5tical portion ( radiation en]gy--! direction ( en]gy-flux4 ,9 o!r words1 x may be consid]$ z ! pa? ( a labell$ di/urbance2 = x is "s special feature :i* enables an eye to fix direction3 x is t :i* det]m9es ! l9e ( collimation ( a telescope4 ,n[ 9 ord] t a di/urbance f ,a may rea* ,b1 x is necess>y t adjac5t elem5ts ( a wave front at ,a %all arrive at ,b 9 ! same phase2 h5ce ! pa? by :i* a di/urbance travels mu/ satisfy ?is condition f po9t to po9t4 ,?is condition w be satisfi$ if ! "t ( j\rney d[n a ray & d[n all inf9itesimally diff]+ pa?s is ! same4 ,! equation to a ray is !re=e conta9$ 9 ! /atem5t t ! "t tak5 by light to trav]se x is a m9imum2 or ,a1,b ds_/,v m9imum ,if ! m$ium1 in/ead ( be+ /ation>y1 is drift+ ) ! velocity v1 at angle to ! ray1 we mu/ sub/itute = ,v ! modifi$ velocity ,v cos v cos 2 & s ! function t has to be a m9imum1 9 ord] to give ! pa? ( a ray 9 a mov+ m$ium1 is ,"t ( j\rney ,a1,b ds _/ ,v7cos cos 7 ,a1,b 7,v cos - v cos 7 _/ 7,v7#a-77 ds m9imum :]e is ! ratio v_/,v4 ,pa? ( ,ray1 & ,"t ( ,j\rney1 ?r\gh an ,irrotationally ,mov+ ,m$ium4 ,writ+ a velocity-pot5tial 9 ! above equation to a ray1 t is putt+ v cos d_/ds1 & ignor+ possible v>iations 9 ! m9ute correction factor #a- betwe5 ! po9ts ,a & ,b1 x becomes ,"t ( j\rney ,a1,b cos _/ 7#a - 7 ds_/,v - 7 - 7 _/ ,v7 #a-7 m9imum4 ,n[ ! second t]m dep5ds only on end po9ts1 & !re=e has no effect on pa?4 ,! fir/ t]m conta9s only ! second p[] ( ab]ration magnitude2 & h5ce x has mu* ! same value z if ev]y?+ 7 /ation>y4 ,a ray t 0 /raight1 w rema9 /raight 9 spite ( motion4 ,:atev] %ape x _h1 t x w reta94 ,only cos 1 & v>iations 9 1 c produce any effect on pa?2 & effects s produc$ mu/ be v small1 s9ce ! value ( cos is 7#a - s974 ,a second-ord] effect on direction may !re=e be produc$ by irrotational motion1 b n a fir/-ord] effect4 ,a simil> /atem5t applies to ! "t ( j\rney r\nd any clos$ p]iph]y4 ,mi*elson's ,exp]im5t4 ,we conclude1 !re=e1 t g5]al e!rial drift does n affect ei!r ! pa? ( a ray1 or ! "t ( its j\rney to & fro1 or r\nd a complete cont\r1 to any important ext5t4 ,b t tak+ second-ord] quantities into acc\nt1 ! "t ( go+ to & fro 9 any direction incl9$ at angle to a con/ant drift is1 f ! above expression1 ,t ,t #b,t cos _/ 7#a-7 7#a - s97 _/ 7#a - 7 #b,t1 :]e #b ,t is ! ord9>y "t ( ! d\ble j\rney )\t any drift4 ,h5ce "s slight modification ( int]f]5ce effects by reason ( drift w\ld seem to be possible2 s9ce ! "t ( a to-&-fro light-j\rney dep5ds subord9ately on ! incl9ation ( ray to drift4 ,! above expression applies to ,mi*elson's rem>kable exp]im5t#aj ( s5d+ a split beam to & fro1 half along & half across ! l9e ( ! e>?'s motion2 & is1 9 fact1 a !ory ( x4 ,!re ought to be an effect due to ! diff]5ce betwe5 #j & #ij4 ,b none c be detect$4 ,h5ce1 ei!r some?+ else happ5s1 or ! e!r ne> ! e>? is dragg$ ) x s z n to /ream ?r\gh our in/rum5ts4 ,alt]native ,explanation4 ,b if ! e!r is dragg$ along ne> mov+ matt]1 x behaves l a visc\s fluid1 & all idea ( a velocity-pot5tial mu/ be ab&on$4 ,?is w\ld complicate ! !ory ( ab]ration 7pp4 #de & #fa71 & moreov] is dead aga9/ ! exp]im5tal evid5ce describ$ 9 ,*apt] ,v4 ,! negative result ( ,mr4 ,mi*elson's is1 h[ev]1 explicable 9 ano!r way1--namely1 by ! ,fitz,gerald-,lor5tz !ory t ! l9e> dim5sions ( bodies are a function ( _! motion ?r\gh ! e!r4 ,& su* an effect x is reasonable to expect2 s9ce1 if cohesion =ces are electrical1 !y mu/ be affect$ by motion1 to a kn[n & calculable am\nt1 dep5d+ on ! squ>e ( ! ratio ( ! spe$ to ! velocity ( light4 7,see end ( ,*ap4 ,,iv47 ,! !ory ( ,pr(essor ,h4,a4 ,lor5tz1 accord+ly1 %[s t ! %ape ( ,mi*elson's /one support+ block w be di/ort$ by ! motion2 its dim5sions across & along ! l9e ( e!r drift be+ affect$ diff]5tly4 ,& ! am\nt ( ! *ange w be su* z precisely to comp5sate & neutralise ! optical effect ( motion :i* might o!rwise be p]ceiv$4 ,?is !ory is n[ g5]ally accept$4 ,x is ?is neutralis+ or comp5satory effect1--:i* acts equally on to-&-fro motion ( light1 to-&-fro motion ( electric curr5ts1 & on ! %ape ( mat]ial bodies1--t r5d]s any positive result 9 exp]im5ts on e!r-drift s difficult or impossible to obta92 s t1 9 spite ( ! spe$ ) :i* we are ru%+ ?r\gh space1 no p]ceptible influ5ce is felt on ei!r electrical or optical ph5om5a1 except ^? :i* are due to relative motion ( s\rce & obs]v]4 ,"s ,details 9 ! ,!ory ( ! ,doppl] ,effect1 or ,effect ( ,motion on ,disp]sion by ,prism or ,grat+4 ,:5 light is analys$ by a prism or grat+ into a spectrum1 ! c\rse ( ea* ray is deflect$--refract$ or diffract$--by an am\nt correspond+ to its frequ5cy ( vibration or wave-l5g?4 ,motion ( ! m$ium1 s long z x is /eady1 affects nei!r frequ5cy nor wave-l5g?1 & accord+ly is )\t influ5ce on ! result4 ,x produces no ,doppl] effect except :5 wax+ or wan+4 ,motion ( ! s\rce alone cr[ds ! waves toge!r on ! advanc+ side & spreads !m out on ! rec$+ side4 ,an obs]v] !re=e :om ! s\rce is approa*+ receives %ort] waves1 & "o f :om ! s\rce is rec$+ receives long] waves1 ?an normal4 ,at any fix$ po9t waves w arrive1 !re=e1 ) modifi$ frequ5cy4 ,s long z a s\rce is /ation>y ! wave-l5g?s emitt$ are q normal1 b motion ( an obs]v] may *ange ! frequ5cy ) :i* !y are receiv$1 9 an obvi\s way2 !y are swept up fa/] if ! receiv] is approa*+1 !y h a /]n *ase if x is rec$+4 ,all ?is is famili>1 & 0 geometrically illu/rat$ 9 ,*apt] ,,iii1 b !re are "s m9or & r curi\s details :i* are wor?y ( brief consid]ation4 ,grat+ ,!ory4 ,= suppose a 'grat+' is us$ to analyse ! light4 ,its effect c dep5d on no?+ k9etic2 x mu/ be regulat$ by ! m]ely geometric wid? ( ! rul$ spaces on x4 ,consequ5tly x c only directly appreh5d wave-l5g?s1 n frequ5cies4 ,9 ! case ( a mov+ s\rce1 !re=e1 :5 ! wave-l5g? is really *ang$1 a grat+ w appreciate ! fact1 & w %[ a true ,doppl] effect4 ,b 9 ! case ( a mov+ obs]v]1 :5 all ! waves receiv$ are ( normal l5g?1 ?\gh swept up ) abnormal frequ5cy1 ! grat+ mu/ /ill indicate wave-l5g? alone1 & accord+ly w %[ no true ,doppl] effect4 ,b inasmu* z ! telescope or l9e ( vision is incl9$ at ! angle ( disp]sion to ! direction ( ! incid5t ray1 ord9>y ab]ration mu/ come 91 z x always does :5 an obs]v] moves a?w>t 8 l9e ( vision2 & s !re w be a spuri\s or app>5t ,doppl] effect due to common ab]ration4 ,t is to say a spectrum l9e w n be se5 9 its true place1 b w appe> to be %ift$ by an am\nt almo/ exactly imitative ( a real ,doppl] effect--! imitation be+ correct up to ! second ord] ( ab]ration magnitude4 ,! slight out/&+ diff]5ce betwe5 !m is calculat$ 9 my ,philosophical ,transactions pap]1 #ahic1 page #ghg4 ,x is too small to obs]ve4 ,x is n an important matt]1 b z x is r tr\blesome to "w out ! diffraction obs]v$ by a grat+ advanc+ t[>ds ! s\rce ( light1 x may be z well to record ! result "h4 ,! foll[+ are ! diffract$ rays :i* require att5tion1--) ! incl9ation ( ea* to ! grat+-normal specifi$3-- ,! diffract$ ray if all 7 /ation>y1 2 ,! real diffract$ ray :5 grat+ is advanc+1 2 ,! ray z p]ceiv$1 all[+ = ab]ration1 2 ,! equival5t diffract$ ray if all 7 /ation>y & ! wave-l5g? really %ort5$1 4 ,z an auxili>y we use ! ab]ration angle 1 su* t s9 s9 1 :]e v_/,v4 ,among ^! f\r angles ! foll[+ relations hold2 s t1 giv5 "o ( !m1 all are kn[n4 - s9 7#a - 7 s9 s9 7#a - v]s 7 s9 ,:5ce & are v ne>ly b n absolutely ! same4 is ! ray obs]v$ by an in/rum5t dep5d+ prim>ily on frequ5cy1 l a prism2 is ! ray obs]v$ by an in/rum5t dep5d+ prim>ily on wave-l5g?1 l a grat+4 ,prism ,!ory4 ,n[ let a prism be us$ to analyse ! light2 its disp]sive p[] is 9 mo/ !ories held to dep5d directly ^u frequ5cy--i4e4 ^u a "t relation betwe5 ! p]iod ( a light vibration & ! p]iod ( an atomic or electronic revolution or o!r h>monic excursion4 ,let u say1 !re=e1 t prismatic disp]sion directly indicates frequ5cy4 ,x _c dep5d ^u wave-l5g?1 = ! wave-l5g? inside diff]5t sub/ances is diff]5t1 & ?\gh refractive index corresponds to ?is1 disp]sive p[] does n4 ,9 ! case ( a prism1 !re=e1 no di/9ction c be drawn betwe5 motion ( s\rce & motion ( receiv]2 = 9 bo? cases ! frequ5cy ) :i* ! waves are receiv$ w be alt]$1--ei!r because !y are really %ort]1 ?\gh arriv+ at normal spe$1 or because !y are swept up fa/]1 al?\gh ( normal l5g?4 ,a*romatic ,prism4 ,x mu/ be notic$ t ! obs]vation ( ,doppl] effect by a prism dep5ds entirely on disp]sion2 i4e4 on waves ( diff]5t l5g? be+ affect$ diff]5tly4 ,b prisms c be con/ruct$ ^: disp]sion is correct$ & neutralis$4 ,su* a*romatic prisms1 if p]fectly a*romatic1 w treat waves ( all sizes alike2 &1 accord+ly1 ! %ort5+ ( ! waves f a mov+ s\rce w n produce any effect4 ,a*romatic prisms w !re=e behave to t]re/rial & to extra-t]re/rial s\rces1 i4e4 to relatively /ation>y & relatively mov+ s\rces1 9 ! same way4 ,?is mu/ be recollect$ 9 connexion ) sev]al ( ! negative results rightly obta9$ by "s obs]v]s2 su* z ,arago1 = in/ance1 :o appli$ an a*romatic prism to a /> :i* ! e>? 0 approa*+1 )\t obs]v+ any effect4 ,a ,doppl] effect %\ld h be5 obs]v$ by a disp]sive prism1 b n by an a*romatic "o3 = ! refractive index ( a sub/ance is n affect$ by any motion ( ! e>?4 ,x is n reasonable to expect t refractive index w\ld be affect$1 s9ce x dep5ds 9 simple geometrical fa%ion on ret>d$ velocity1 i4e4 on optical e!rial load+ or app>5t extra int]nal d5sity4 ,an a*romatic grat+1 h[ev]1 is 7ra%ly speak+7 an impossibility4 ,,effect ,,( ,,transp>5t ,,matt]4 ,b :5 a ray is travell+ ?r\gh transp>5t matt]1 w n motion ( t matt] affect its c\rse8 ,if ! matt] is mov$ relatively to s\rce & receiv]1 z 9 ,fizeau's exp]im5t ) runn+ wat]1 mo/ c]ta9ly x w2 to ! full effect ( ! load+ or extra or travell+ d5sity1 7-#a71 comp>$ ) ! total d5sity 4 ,?is fraction ( ! velocity ( ! mat]ial m$ium mu/ directly influ5ce ! velocity ( light1 = ! waves w be convey$ 9 ! s5se ( ! mat]ial motion u1 ) ! additional spe$ u7-#a7_/4 7,see also ,app5dix #c47 ,b if ! transp>5t matt] ?r\gh :i* ! light is go+ is /ation>y ) respect to s\rce & receiv]--only %>+ ) !m ! g5]al planet>y motion1 i4e4 be+ subject to ! opposite all-p]vad+ e!r drift1--!n no influ5ce due to ! drift c be exp]i5c$2 = ! free e!r ( space behaves j z x w\ld if ! matt] 7 n !re4 ,?is c be %[n m elaborately by ! foll[+ calculation4 ,optical ,effect ( ,e!r ,drift ?r\gh ,d5se ,/ation>y ,bodies4 ,! calculation ( ! lag 9 phase caus$ by ,fresnel's e!rial motion may proce$ ?us3--,a d5se slab ( ?ickness z1 :i* w\ld naturally be trav]s$ ) ! velocity ,v_/1 is trav]s$ ) ! velocity 7,v_/7 cos 7v_/7 cos 2 :]e v is ! relative velocity ( ! e!r 9 its neighb\rhood2 :5ce ! "t ( j\rney ?r\gh x is 7z7 _/ ,v7cos 7_/7 cos 71 in/ead ( z_/,v1 ,s ! equival5t air ?ickness1 in/ead ( be+ 7 - #a7z1 is z _/ 7cos 7_/7 cos 7 - z 7 7 cos - cos 7 _/ 7#a - _/7 - #a 7z1 or1 to ! fir/ ord] ( m9uti1 7 - #a7z - z cos 2 be+ ! angle betwe5 ray & e!r drift inside ! m$ium4 ,s ! extra equival5t air lay] due to ! motion is approximately z cos 1 a quantity indep5d5t ( 4 ,h5ce1 no plan = detect+ ?is fir/-ord] effect ( motion is 9 any way assi/$ by ! use ( d5se /ation>y sub/ances2 _! extra e!r1 be+ /ation>y1 does n affect ! lag caus$ by motion1 except inde$ 9 ! second ord] ( small quantities1 z %[n above4 ,direct exp]im5ts made by ,hoek1#aa & by ,masc>t1 on ! effect ( introduc+ tubes ( wat] into ! pa? ( half-beams ( light1 are 9 entire accord ) ?is negative conclusion4 ,?us1 !n1 we f9d t no g5]al motion ( ! entire m$ium c be detect$ by *anges 9 direction1 or 9 frequ5cy1 or 9 phase2 = on none ( !m has x any appreciable 7i4e4 fir/-ord]7 effect1 ev5 :5 assi/$ by d5se matt]4 99 99 99 99 99 ,ano!r mode ( /at+ ! matt] is to say t ! behavi\r ( e!r inside matt] is su* z to enable a pot5tial-function1 v cos ds1 to exi/ ?r\gh\t all transp>5t space1 s f> z motion ( e!r alone is conc]n$4 7,see ,app5dix #c47 ,! exi/5ce ( ?is pot5tial function readily acc\nts = ! abs5ce ( all effect on direction due to ! g5]al drift ( ! m$ium1 :e!r 9 ! pres5ce ( d5se matt] 7su* z wat]-fill$ telescopes7 or o!rwise4 ,:atev] may be ! pa? ( a ray by reason ( reflexion or refraction 9 a /ation>y e!r1 x is precisely ! same 9 a mov+ "o if ?is condition is satisfi$1 al?\gh ! wave-normals & wave-fronts are def9itely %ift$4 ,h[ev] matt] affects or loads ! e!r inside x1 x _c on ?is !ory be said ei!r to hold x /ill1 or to c>ry x ) x4 ,! g5]al e!r /ream mu/ rema9 unaffect$1 n only ne>1 b inside matt]1 if rays are to reta9 precisely ! same c\rse z if x 7 relatively /ation>y4 ,b x mu/ be und]/ood t ! e!rial motion "h contemplat$ is ! g5]al drift ( ! entire m$ium2 or its correlative1 ! uni=m motion ( all ! matt] conc]n$4 ,!re is no?+ to be said aga9/ ab]ration effects be+ producible or modifiable by motion ( p>ts ( ! m$ium1 or by ! artificial motion ( transp>5t bodies & o!r p>tition$-(f regions4 ,artificial motion ( matt] may readily alt] bo? ! "t ( j\rney & ! pa? ( a ray1 = x has no pot5tial conditions to satisfy2 x may easily describe a clos$ cont\r1 & may take "p 9 convey+ light4 ,b ,i mu/ repeat t ?is conveyance ( light by mov+ matt] is an effect due to ! mat]ial load only2 x repres5ts no di/urbance ( ! e!r ( space4 ,fresnel's law1 9 fact1 def9itely means t mov+ transp>5t matt] does n appreciably di/urb ! e!r ( space4 ,direct exp]im5t1 z record$ 9 ,*apt] ,v1 %[s t close to rapidly-mov+ opaque matt] !re is no di/urbance ei!r4 ,i reg>d ! non-di/urbance ( ! e!r ( space by mov+ matt] z e/abli%$4 ,,footnotes3 #aj ,philosophical ,magaz9e1 ,dec41 #ahhg4 #aa ,ar*ives ,nerl&aises 7#ahfi71 ,vol4 ,,iv1 p4 #ddc1 or ,nature1 ,vol ,,xxvi1 p4 #ejj4 ,also ,*apt] ,,iv above4 ,,summ>y4 ,! e/imates ( ?is book1 & ( ,mod]n ,views ( ,electricity1 are t ! e!r ( space is a cont9u\s1 incompressible1 /ation>y1 fundam5tal sub/ance or p]fect fluid1 ) :at is equival5t to an in]tia-coeffici5t ( #aj grammes p] c4c42 t matt] is compos$ ( modifi$ & electrifi$ specks1 or m9ute /ructures ( e!r1 :i* are am5able to me*anical z well z to electrical =ce & add to ! optical or electric d5sity ( ! m$ium2 & t ela/ic-rigidity & all pot5tial en]gy are due to excessively f9e-gra9$ e!rial circulation1 ) an intr9sic k9etic en]gy ( ! ord] #aj ergs p] cubic c5timetre4 ,,app5dix #a ,,on ,,gravity ,,& ,,e!rial ,,t5sion ,9 ! ari?metical examples ( ,*apt] ,,ix we reckon m]ely ! =ce betwe5 two bodies2 b ! ,newtonian t5sion m5tion$ 9 ,*apt] ,,viii does n signify t =ce1 b r a c]ta9 condition or /ate ( ! m$ium1 to v>iations 9 :i*1 f place to place1 ! =ce is due4 ,?is ,newtonian t5sion is a mu* great] quantity ?an ! =ce to :i* x gives rise2 &1 moreov]1 x exi/s at e po9t ( space1 in/ead ( be+ integrat$ all ?r\gh an attract$ body4 ,x rises to a maximum value ne> ! surface ( any sph]ical mass2 & if ! radius be ,r & ! gravitational int5sity is g1 ! t5sion at ! surface is ,t g,r4 ,at any di/ance r1 fur!r away1 ! t5sion is ,t g,r_/r4 ,?is foll[s at once ?us3-- ,/at+ ! law ( gravitation z ,f mm_/r1 ! mean+ "h adopt$ = e!rial t5sion at ! surface ( ! e>? is ,t ,r1 ,e_/r dr ,e_/,r2 s t ! ord9>y int5sity ( gravity is g -d,t_/d,r ,e_/,r #d_/c,r4 ,accord+ly1 ne> ! surface ( a planet ! t5sion is ,t g,r1 or = diff]5t planets is proportional to ,r4 ,! velocity ( free fall f inf9ity to su* a planet is 7#b,t72 ! velocity ( free fall f circumf]5ce to c5tre1 assum+ uni=m di/ribution ( d5sity1 is 7,t72 & f inf9ity to c5tre x is 7#c,t74 ,exp&+ all ?is into words3-- ,! e!rial t5sion ne> ! e>?'s surface1 requir$ to expla9 gravity by its rate ( v>iation1 is ( ! ord] #f #aj c4g4s4 units4 ,! t5sion ne> ! sun is #bejj times z great 7p4 #ajc74 ,) diff]5t sph]es 9 g5]al1 x is proportional to ! d5sity & to ! sup]ficial area4 ,h5ce1 ne> a bullet "o in* 9 diamet]1 x is ( ! ord] #aj2 & ne> an atom or an electron ab\t #aj c4g4s4 ,if ev] ! t5sion rose to equal ! con/itutional ela/icity or intr9sic k9etic en]gy ( ! e!r1--:i* we h se5 is #aj dynes p] squ>e c5timetre 7or ergs p] c4c47 or #aj tons weight p] squ>e millimetre1--x seems likely t some?+ w\ld give way4 ,b no kn[n mass ( matt] is able to cause any?+ l su* a t5sion4 ,a small] aggregate ( matt] w\ld be able to g5]ate ! velocity ( light 9 bodies fall+ t[>ds x f a great di/ance2 & x may be d\bt$ :e!r any mass s great z to be able to d ev5 t c exi/ 9 "o lump4 ,9 ord] to set up a t5sion equal to :at is "h suspect$ ( be+ a critical1 or presumably disruptive1 /ress 9 ! e!r #aj c4g4s41 a globe ( ! d5sity ( ! e>? w\ld h to h a radius ( eight light ye>s4 ,9 ord] to g5]ate a velocity ( free fall "u gravity equal to ! velocity ( light1 a globe ( ! e>?'s d5sity w\ld h to be equal 9 radius to ! di/ance ( ! e>? f ! sun1 or say #bf1jjj times ! e>?'s radius4 ,if ! d5sity 7 less1 ! sup]ficial area w\ld h to be increas$ 9 proportion1 s z to keep ,r con/ant4 ,! :ole visible univ]se )9 a p>allax ( #a_/ajjj second ( arc1 e/imat$ by ,"l ,kelv9 z ! equival5t ( #aj suns1 w\ld be q incompet5t to raise e!rial t5sion to ! critical po9t #aj c4g4s4 unless x 7 conc5trat$ to an absurd degree2 b x c\ld g5]ate ! velocity ( light ) a d5sity comp>able to t ( wat]1 if mass 7 con/ant4 ,if ! av]age d5sity ( ! above visible univ]se 7:i* may be tak5 z #a4f #aj grammes p] c4c47 cont9u$ )\t limit1 a disruptive t5sion ( ! e!r w\ld be rea*$ :5 ! radius 0 comp>able to #aj light ye>s2 & ! velocity ( light w\ld be g5]at$ by x :5 ! radius 0 #aj light ye>s4 ,b het]og5eity w\ld enable ^! values to be rea*$ m easily4 ,gravitation is ?us suppos$ to be ! result ( a me*anical t5sion inh]5tly1 & p]haps in/antane\sly1 set up ?r\gh\t space :5ev] ! e!rial /ructure call$ an electric *>ge comes into exi/5ce2 ! t5sion be+ directly proportional to ! squ>e ( ! *>ge & inv]sely z its l9e> dim5sions4 ,cohesion is q diff]5t1 & is due to a residual electrical attraction betwe5 gr\ps ( neutral molecules across molecul> di/ances3 a v>iant or modification ( *emical aff9ity4 ,,app5dix #b ,,calculations ,,9 ,,connexion ,,) ,,e!r ,,d5sity ,j z ! rigidity ( ! e!r is ( a purely electric "*1 & is n felt me*anically--s9ce me*anically x is p]fectly fluid1--s its d5sity is likewise ( an electromagnetic "*1 & aga9 is n felt me*anically1 because x _c be mov$ by me*anical means4 ,x is by f> ! mo/ /ation>y body 9 exi/5ce2 ?\gh x is end[$ ) high intr9sic en]gy ( local movem5t1 analog\s to turbul5ce1 conf]r+ on x gyro/atic prop]ties4 ,optically1 its rigidity & d5sity are bo? felt1 s9ce optical di/urbances are ess5tially electromotive4 ,matt] loads ! e!r optically1 9 accordance ) ! recognis$ fraction 7-#a7 _/ 2 & ?is load+1 be+ "p & p>cel ( ! matt]1 ( c\rse travels ) x4 ,x is ! only "p am5able to me*anical =ce4 ,! me*anical d5sity ( matt] is a v small portion ( ! e!rial d5sity2 :]eas ! optical or electrical d5sity ( matt]--be+ really t ( e!r affect$ by ! intr9sic or con/itutional electricity ( matt]--is n s small4 ,! relative optical virtual d5sity ( ! e!r inside matt] is measur$ by 2 b x may be really a defect ( ela/icity1 at lea/ 9 non-magnetic mat]ials4 ,electrical & optical effects dep5d ^u e4 ,me*anical or in]tia effects dep5d ^u e4 ,electric *>ges c load ! e!r optically1 q appreciably2 b z reg>ds me*anical load+1 ! d5se/ matt] kn[n is trivial & gossam]-l comp>$ ) ! unmodifi$ e!r 9 ! same space4 ,massiv5ess ( ! ,e!r d$uc$ f ,electrical ,pr9ciples4 ,ea* electron1 mov+ l a sph]e ?r\gh a fluid1 has a c]ta9 mass associat$ ) x2 dep5d5t on its size1 &1 at v high spe$s1 on its velocity also4 ,if we treat ! electron m]ely z a sph]e mov+ ?r\gh a p]fect liquid1 its behavi\r is exactly z if its mass 7 increas$ by half t ( ! fluid displac$ & ! surr\nd+ fluid 7 annihilat$4 ,e!r be+ incompressible1 ! d5sity ( fluid inside & outside an electron mu/ be ! same4 ,s1 deal+ ) x 9 ?is simple/ fa%ion1 ! resultant in]tia is half z great aga9 z t ( ! volume ( fluid correspond+ to ! electron3 t is to say ! effective mass is #b1 :]e is ! uni=m d5sity4 ,if an electron is ( "s o!r %ape ?an a sph]e1 !n ! num]ical "p is modifi$1 b rema9s ( ! same ord] ( magnitude1 s long z !re are no %>p edges4 99 99 99 99 99 ,if1 h[ev]1 we consid] ! mov+ electron z g5]at+ circul> l9es ( magnetic induction1 by reason ( "s rotational prop]ty ( ! e!r1 & if we attribute all ! magnetic in]tia to ! magnetic :irl ?us caus$ r\nd its pa?1--provisionally treat+ ?is :irl z an actual circulation ( fluid excit$ by ! locomotion1--!n we %all proce$ ?us3-- ,let a sph]ical electron e ( radius a be fly+ at mod]ate spe$ u1 s t ! magnetic field at any po9t1 r1 outside1 is ,h eu s9 _/ r1 & ! en]gy p] unit volume ev]y:]e is ,h_/#h4 ,b a magnetic field has be5 ?\ght ( by _m ma!maticians z a circulation ( fluid along ! l9es ( magnetic induction--:i* are always clos$ curves--at "s unkn[n velocity w4 ,s consid] ! en]gy p] unit volume any:]e3 x c be repres5t$ by ! equival5t expressions w ,h_/#h _/#h eus9 _/ r2 :]e=e w_/u 7_/#d7 e s9 _/ r4 ,! velocity ( ! hypo!tical circulation mu/ be a maximum at ! equator ( ! sph]e1 :]e ra & #ij2 s1 call+ ?is w1 w_/u 7_/#d7 e _/ a1 & w_/w a s9 _/ r2 :]e=e ! major "p ( ! circulation is limit$ to a region n f> remov$ f ! surface ( ! electron4 ,! en]gy ( ?is motion is #j1 a1 w #b r s9 rd dr1 :5ce1 sub/itut+ ! above value ( w1 ! en]gy comes out equal to #d_/c a w4 ,comp>+ ?is ) a mass mov+ ) spe$ u1 m #h_/c a7w_/u74 ,?is agrees ) ! simple hydrodynamic e/imate ( effective in]tia if w #cu2 t is to say1 if ! :irl 9 contact ) ! equator ( ! sph]e is ( ! same ord] ( magnitude z ! velocity ( ! sph]e4 ,n[ = ! real relation betwe5 w & u we mu/ make a hypo!sis4 ,if ! two are consid]$ equal1 ! effectively di/urb$ mass comes out z twice t ( ! bulk ( ! electron4 ,if w is small] ?an u1 !n ! mass ( ! effectively di/urb$ fluid is less ev5 ?an ! bulk ( an electron2 & 9 t case ! e/imate ( ! fluid-d5sity mu/ be exagg]at$ 9 ord] to supply ! requir$ en]gy4 ,x is difficult to suppose ! equatorial circulation w great] ?an u1 s9ce x is g5]at$ by x2 & x is mo/ reasonable to treat !m bo? z ( ! same ord] ( magnitude4 ,s1 tak+ !m z equal1 e a 7#d_/7 & m twice ! sph]ical mass4 ,h5ce all ! e/imates ( ! effective in]tia ( an electron are ( ! same ord] ( magnitude1 be+ all comp>able ) t ( a mass ( e!r equal to ! electron 9 bulk4 ,b ! l9e> dim5sion ( an electron is #aj c5timetre diamet]1 & its mass is ( ! ord] #aj gram4 ,consequ5tly ! d5sity ( its mat]ial mu/ be ( ! ord] #aj grams p] cubic c5timetre4 ,?is1 truly1 is enorm\s1 b any r$uction 9 ! e/imate ( ! circulation-spe$1 bel[ t ( an electron1 w\ld only g to increase x4 ,&1 s9ce electrons move sometimes at a spe$ n f> bel[ t ( light1 we _c be accus$ ( "u-e/imat+ ! probable velocity ( magnetic sp9 by treat+ x z ( ! same ord] ( magnitude1 at ! b\nd+ surface ( ! electron1 z its own spe$3 a relation sugge/$1 ?\gh n en=c$1 by gyro/atic analogies4 ,"s ,consequ5ces ( ?is ,great ,d5sity4 ,! amplitude ( a wave ( light1 9 a place :]e x is mo/ int5se1 namely ne> ! sun :]e its en]gy am\nts to #b ergs p] c4c41 comes out only ab\t #aj ( ! wave-l5g?4 ,! maximum tang5tial /ress call$ out by su* /ra9 is ( ! ord] #aj atmosph]es4 ,! hypo!tical lum9\s circulation-velocity1 conf]r+ mom5tum on a wave-front1 9 accordance ) ,poynt+'s inve/igation1 comes out #aj cm4 p] sec4 ,^! calculations are giv5 9 ! conclud+ *apt] ( ! new edition ( ,mod]n ,views ( ,electricity4 ,! suppos$ magnetic e!rial drift1 along ! axis ( a sol5oid or o!r magnetic field1 if x exi/1 is comp>able to #jjc c5tim4 p] sec41 or #d in*es an h\r1 = a field ( int5sity #ab1jjj c4g4s4 ,b x is n to be suppos$ t ?is hypo!tical velocity is sl[ ev]y:]e4 ,close to an electron ! spe$ ( magnetic drift is comp>able to ! locomotion-velocity ( ! electron itself1 & may !re=e rise to some?+ ne> ! spe$ ( light2 say #a_/cj? ( t spe$3 b 9 spite ( t1 at a di/ance ( only #a millimetre away1 x is r$uc$ to practical /agnation1 be+ less ?an a millimicron p] c5tury4 ,9 any sol5oid1 ! amp]e-turns p] l9e> in* furni% a measure ( ! spe$ ( ! suppos$ magnetic circulation along ! axis--no matt] :at ! mat]ial ( ! core may be--9 millimicrons p] sec4 #a micron #aj metre2 #a millimicron is #aj metre #aj c5timetre1 or a million? ( a millimetre4 ,to get up an e!rial spe$ ( #a c5timetre p] second--su* z might be detect$ exp]im5tally by ref9$ optical appliances1 ?r\gh its effect 9 accel]at+ or ret>d+ ! spe$ ( light s5t along ! l9es ( magnetic =ce1--w\ld ne$ a sol5oid ( great l5g?1 r\nd e c5timetre ( :i* #ajjj amp]es circulat$ #cjjj times4 ,t is to say1 a long field ( f\r million c4g4s4 units ( int5sity4 ,9 o!r words1 any /ream+ along magnetic l9es ( =ce1 su* z c\ld acc\nt = ! en]gy ( a magnetic field1 mu/ be comp>able1 9 c5timetres p] second1 to "o f\r-million? ( ! numb] ( c4g4s4 units ( int5sity 9 ! magnetic field4 ,,app5dix #c ,,fresnel',s ,,law ,a ,,special ,,case ,,( ,a ,,univ]sal ,,pot5tial ,,function ,! mod]n view ( ,fresnel's ,law may be word$ ?us3-- ,inside a region occupi$ by matt]1 9 addition to ! univ]sal e!r ( space1 are c]ta9 modifi$ or electrifi$ specks1 :i* build up ! mat]ial atoms4 ,^! *>g$ p>ticles1 :5 !y move1 h specific in]tia1 due to ! magnetic field surr\nd+ ea* ( !m4 ,& by reason ( ?is prop]ty1 & z a consequ5ce ( _! discont9uity1 !y virtually increase ! optical d5sity ( ! e!r ( space1 act+ 9 analogy ) weights di/ribut$ along a flexible cord4 ,?us !y r$uce ! velocity ( light 9 ! ratio ( ! refractive index 3#a1 & !re=e may be tak5 z increas+ ! virtual d5sity ( ! e!r 9 ! ratio #a34 ,t is to say1 _! load+ makes ! e!r behave to optical waves z if--be+ a homog5e\s m$ium )\t ^! discont9u\s loads--x _h a d5sity times t :i* x has 9 space outside matt]4 ,call+ ! d5sity outside #a1 ! extra d5sity inside mu/ be -#a1 s z to make up ! total to 4 ,! -#a portion is t :i* we call matt]1 & ?is portion is readily susceptible to locomotion1 be+ subject to--t is1 accel]at$ by--me*anical =ce4 ,! free portion ( normal d5sity #a is absolutely /ation>y z reg>ds locomotion1 :e!r x be inside or outside a region occupi$ by ord9>y matt]1 = x is n am5able to ei!r me*anical or electric =ces4 ,!y are transmitt$ by x1 b nev] t]m9ate ^u x2 except1 inde$1 at ! peculi> /ructure call$ a wave-front1 :i* simulates "s ( ! prop]ties ( matt]4 7,if free or unmodifi$ e!r c ev] be mov$ at all1 x mu/ be by means ( a magnetic field2 along ! l9es ( :i* x has1 9 sev]al !ories1 be5 suppos$ to circulate4 ,ev5 ?is1 h[ev]1 is n real locomotion47 ,fizeau te/$ t /raight=w>d consequ5ce ( ?is !ory :i* is kn[n z ,fresnel's ,law1 & asc]ta9$ by exp]im5t t a beam ( light 0 accel]at$ or ret>d$ by a /ream ( wat]1 accord+ z x travell$ ) or aga9/ ! /ream4 ,& he f\nd ! magnitude ( ! effect precisely 9 accordance ) ! ratio ( ! locomotive portion ( ! e!r to ! :ole1--! fraction 7-#a7_/ ( ! spe$ ( ! wat] be+ add$ to or subtract$ f ! velocity ( light1 :5 a beam 0 s5t d[n or up ! /ream4 ,b ev5 if ano!r mode ( expression be adopt$1 ! result to be anticipat$ f ?is exp]im5t w\ld be ! same4 ,= in/ead ( say+ t a modifi$ portion ( ! e!r is mov+ ) ! full velocity ( ! body :ile ! re/ is /ation>y1 x is p]missible = "s purposes to treat ! :ole int]nal e!r z mov+ ) a fraction ( ! velocity ( ! body4 ,on ?is me?od ( /atem5t ! e!r outside a mov+ body is /ill absolutely /ation>y1 b1 z ! body advances1 e!r may be ?\ght ( z cont9ually cond5s+ 9 front1 &1 z x 71 evaporat+ beh9d2 :ile1 inside1 x is /ream+ ?r\gh ! body 9 its cond5s$ condition at a pace su* t :at is equival5t to ! normal quantity ( e!r 9 space may rema9 absolutely /ation>y4 ,to ?is end its spe$ backw>ds relative to ! body mu/ be u_/ & accord+ly its spe$ =w>d 9 space mu/ be u7#a-a_/74 ,= consid] a slab ( matt] mov+ flatways ) velocity u2 let its int]nal e!rial d5sity be 1 & let ! ext]nal e!r ( d5sity #a be /ation>y4 ,let ! =w>d spe$ ( ! int]nal e!r ?r\gh space be xu1 s t a beam ( light !re9 w\ld be hurri$ =w>d ) ?is velocity4 ,!n consid] two imag9>y p>allel planes mov+ ) ! slab1 "o 9 advance ( x & ! o!r inside x1 & express ! fact t ! am\nt ( e!r betwe5 ^? two planes mu/ cont9ue con/ant4 ,! am\nt /ream+ relatively backw>ds ?r\gh ! fir/ plane z x moves w be measur$ by u times ! ext]nal d5sity1 :ile ! am\nt simil>ly /ream+ backw>ds ?r\gh ! second plane w be 7u-xu7 times ! int]nal d5sity4 ,b ?is latt] am\nt mu/ equal ! =m] am\nt4 ,9 o!r words1 u#a mu/ equal 7u-xu7 4 ,consequ5tly x comes out x 7-#a7_/2 :i* is ,fresnel's incontrov]tible law = ! convective effect ( mov+ transp>5t matt] on light inside x4 ,! :ole subject1 h[ev]1 may be treat$ m g5]ally1 & = e direction ( ! ray1 on ! l9es ( ,*apt] ,x1 ?us3-- ,inside a transp>5t body light travels at a spe$ ,v_/2 & ! e!r1 :i* outside drifts at velocity v1 mak+ an angle ) ! ray1 inside may be drift+ ) velocity v & angle 4 ,h5ce ! equation to a ray inside su* matt] is ,t ds _/ 77,v_/7 cos v cos 7 m941 :]e s9 _/s9 v_/7,v_/7 4 ,?is may be writt5 ,t cos ds _/ 7,v_/ 7#a-77 - v cos ds _/ 7,v_/ 7#a-772 ! second t]m alone involves ! fir/ p[] ( ! motion1 & assum+ t v cos d_/ds1 & treat+ z a quantity too small = its possible v>iations to ne$ att5tion1 ! expression becomes ,t ,t cos _/ 7#a - 7 - 7,b - ,a7 _/ 7,v7#a - 771 ,t be+ ! "t ( travel ?r\gh ! same space :5 empty4 ,n[1 if ! "t ( j\rney & c\rse ( ray1 h[ev] !y be affect$ by ! d5se body1 are n to be m affect$ by reason ( e!rial drift ?r\gh x ?an if x 7 s mu* empty space1 x is necess>y t ! diff]5ce ( pot5tial betwe5 two po9ts ,a & ,b %\ld be ! same :e!r ! space betwe5 is fill$ ) d5se matt] or n 7or1 say1 :e!r ! ray-pa? is tak5 ?r\gh or outside a portion ( d5se m$ium74 ,9 o!r words 7call+ ! outside & ! inside pot5tial function71 9 ord] to secure t ,t %all n diff] f ,t by any?+ dep5d+ on ! fir/ p[] ( motion1 x is necess>y t ,b-,a %all equal ,b-,a3 i4e4 t ! pot5tial inside & outside matt] %all be ! same up to a con/ant1 or t v cos v cos 2 :i* = ! case ( drift along a ray is precisely ,fresnel's hypo!sis4 ,ano!r way ( putt+ ! matt] is to say t to ! fir/ p[] ( drift velocity ,t ,t - 7 v cos - v cos 7 ds_/,v1 & t ! second or di/urb+ t]m mu/ vani%4 ,h5ce ,fresnel's hypo!sis z to ! behavi\r ( e!r inside matt] is equival5t to ! assumption t a pot5tial function1 v cos ds 1 exi/s ?r\gh\t all transp>5t space1 s f> z motion ( e!r alone is conc]n$4 ,giv5 t condition1 no fir/-ord] int]f]5ce effect due to drift c be obta9$ f /ation>y matt] by s5d+ rays r\nd any k9d ( clos$ cont\r2 nor c ! pa? ( a ray be alt]$ by e!rial drift ?r\gh any /ation>y matt]4 ,h5ce fill+ a telescope tube ) wat] _c modify ! obs]v$ am\nt ( /ell> ab]ration4 ,! equation to a ray 9 transp>5t matt] mov+ ) velocity u 9 a direction 1 & subject to an indep5d5t e!r drift ( spe$ v 9 direction 1 is ds _/ 7,v_/ cos v_/ cos u#a - 7#a_/7 cos 7 con/4 ,,william ,,br5don ,,& ,,son1 ,,ltd4 ,,pr9t]s1 ,,plym\? ,sci5ce = ! ,g5]al ,read] ,,worlds ,,9 ,,! ,,mak+ ,! ,evolution ( ! ,univ]se4 ,,svante ,,arrh5ius1 ( ! ,nobel ,in/itute1 ,/ockholm4 ,illu/rat$4 #fs4 net ,expla9s ! orig9 ( nebul f suns & suns f nebul1 ! univ]sal di/ribution ( life1 ! cons]vation ( en]gy1 etc41 & %[s h[ all may be acc\nt$ = by ! newly develop$ pr9ciple ( ! pressure ( light ,,a/ronomy ,,) ,,! ,,nak$ ,,eye ,g4,p4 ,,s]viss4 ,illu/rat$4 #fs4 net ,tell+ all t may be se5 9 ! skies )\t ! aid ( ! telescope ,,! ,,fri5dly ,,/>s ,m4,e4 ,,m>t94 ,illu/rat$4 #es4 net ,a h&y volume1 enabl+ ! read] to id5tify ! pr9cipal />s & con/ellations ,,sidelights ,,on ,,a/ronomy ,pr(4 ,,simon ,,newcomb4 ,illu/rat$4 #gs4 #f;d4 net ,discusses su* topics z ,are ! ,planets ,inhabit$8 etc4 etc4 ,,! ,,*emi/ry ,,( ,,comm]ce ,pr(4 ,r4,k4 ,,duncan1 au?or ( ,! ,new ,k4 ,illu/rat$4 #gs4 #f;d4 net2 po/-free1 #gs4 #aa;d4 ,an acc\nt ( ! sci5tific processes involv$ 9 mod]n indu/ry1 ) valuable sugge/ions = _! ext5sion ,,new ,,conceptions ,,9 ,,sci5ce ,,c>l ,,snyd]4 ,illu/rat$4 #gs4 #f;d4 net ,deal+ ) ! new worlds reveal$ by ! microscope1 telescope1 etc41 & ! late/ sci5tific !ories bas$ !reon ,,n9ete5? ,,c5tury ,,sci5ce ,dr4 ,,h5ry ,,smi? ,,williams4 ,illu/rat$4 #is4 ,a review ( ! great sci5tific a*ievem5ts ( mod]n times1 & ! problems n[ be+ inve/igat$ ,%ort /udies on great subjects by di/+ui%$ liv+ m54--,! ,/&>d4 ,,h>p]',s ,,libr>y ,,( ,,liv+ ,,?\ght ,foolscap #hvo1 gilt tops1 decorative cov]s1 ri*ly gilt backs ,p] ,volume3 ,clo? #bs4 #f;d4 net1 ,lea!r #cs4 #f;d4 net ,"s ,contributors3 ,,alg]non ,,*>les ,,sw9burne ,,c\nt ,,leo ,,tol/oy ,w4,m4 ,,fl9d]s ,,petrie ,,sir ,,oliv] ,,lodge ,,!odore ,,watts-,,dunton ,,svante ,,arrh5ius ,,erne/ ,a4 ,,g>dn] ,,arnold ,,mey] ,,sir ,,william ,,crookes c4 c4 ,a p]man5tly useful addition to lit]ature4--,! ,daily ,telegraph4 ,pres5t+ sugge/ive 'liv+' ?\ghts on subjects ( vital int]e/4--,! ,times ,h>p]'s ,libr>y ( ,liv+ ,?\ght ,n[ ,ready3 ,,alg]non ,,*>les ,,sw9burne ,,?ree ,,plays ,,( ,,%akespe>e ,leads u to s _m f9e po9ts ( obs]vation4 ,daily ,telegraph ,lum9\s & valuable4--,/&>d ,,c\nt ,,leo ,,tol/oy ,,! ,,tea*+ ,,( ,,jesus ,w set /ud5ts ?9k+4--,*ri/ian ,_w ,w4,m4 ,,fl9d]s ,,petrie ,,p]sonal ,,religion ,,9 ,,egypt ,,be=e ,,*ri/ianity ,%[s :at ,*ri/ianity meant to ^? :o actually he>d ! tea*+ ( ! ,way ,,sir ,,oliv] ,,lodge ,,! ,,e!r ,,( ,,space ,advocat+ ! view :i* makes ! ,e!r n only all p]vad+1 b sub/antial beyond conception--! mo/ sub/antial ?+--p]haps ! only sub/antial ?+ 9 ! mat]ial univ]se ,,pr(4 ,c4,h4 ,,beck] ,,*ri/ianity ,,& ,,islam ,a /udy ( ! simil>ities1 diff]5ces1 & ! int]action ( ideas betwe5 ! two s*ools ( religi\s ?\ght ,a bold ent]prise & "o to be comm5d$4--,! ,daily ,*ronicle ,h>p]'s ,libr>y ( ,liv+ ,?\ght ,n[ ,ready3 ,,?ree ,,plays ,,( ,,%akespe>e ,,alg]non ,,*>les ,,sw9burne ,,! ,,tea*+ ,,( ,,jesus ,,leo ,,tol/oy ,,p]sonal ,,religion ,,9 ,,egypt ,,be=e ,,*ri/ianity ,w4,m4 ,,fl9d]s ,,petrie ,,! ,,e!r ,,( ,,space ,,sir ,,oliv] ,,lodge ,,! ,,orig9 ,,( ,,! ,,new ,,te/am5t ,,pr(4 ,,william ,,wr$e 7,univ]sity ( ,breslau7 ,,*ri/ianity ,,& ,,islam ,,pr(4 ,c4,h4 ,,beck] 7,colonial ,in/itute1 ,hamburg7 ,=?com+3 ,,diamonds ,,sir ,,william ,,crookes ,,religion ,,& ,,art ,,9 ,,anci5t ,,greece ,,pr(4 ,,erne/ ,a4 ,,g>dn] 7,univ]sity ( ,london7 ,,! ,,life ,,( ,,! ,,univ]se #b vols4 ,,pr(4 ,,svante ,,arrh5ius 7,nobel ,in/itute1 ,/ockholm7 ,,jesus ,,or ,,paul8 ,,pr(4 ,,arnold ,,mey] 7,univ]sity ( ,zuri*7 ,,poetic ,,adequacy ,,9 ,,! ,,tw5tie? ,,c5tury ,,!odore ,,watts-,,dunton ,,revelation ,,& ,,inspiration ,,pr(4 ,,re9hold ,,seeb]g 7,univ]sity ( ,b]l97 ,,h>p] ,,bro!rs ,april1 #aiji #de ,albem>le ,/reet ,london1 ,w4 99 99 99 99 99 ,transcrib]'s ,notes ,p>5!ses h be5 add$ to ma!matical equations = cl>ity & correctness4 ,lett]s repres5t+ ma!matical v>iables are n m>k$ z italic :5 ?is w\ld impair cl>ity 9 expressions & equations4 ,! l[] & upp] limits ( def9ite integrals are indicat$ by curly brackets1 e4g4 #j1444;d repres5ts a def9ite integral ) values ( rang+ f #j to 4 ,! c>et "* is us$ 9 ! expression 7#ag_/af7c_/b to signify rais+ ! fraction #ag_/af to ! p[] #c_/b4 ,o!r expon5ts are repres5t$ us+ sup]script$ num]als1 e4g4 x4 ,italic text is d5ot$ by und]scores & bold text by equal signs4 ,obvi\s punctuation & spell+ errors & inconsi/5t hyph5ation h be5 repair$4 ,9 ambigu\s cases1 ! text has be5 left z x appe>s 9 ! orig9al book4