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CHAR! M.^ / 1.0 I.I 111= ii!i 2 III 1.8 .25 1.4 1.6 MGE Inc ON COLOUR-PHOTOMETRY AND ON SOME QUflNTITflTlYE RELATIONS OF THE PHENOMENON OF PURKINJE ■'•V * 'i? i;y R. J. WILSOX, MA. O.VCnl.nr-R.pin.ToMHTRV a.\-[) . ,x soMK .JC\XTI- lATlMC KI-;i,ATl().\S ( U- THI-: I'Hi-;.\< )MKX()X <>i- rrKKixjK. _ I.KTc ,:rc threv wavs known nt intMM.rin- ,.f .nu-nsuv :„ li^^ht >.„s,a„n.s of diilercn: culunr ,,ualitv The '"'J " ^" ■"■'^■' ^' ^"'^''1 ■■'^•'■t-r of colour in a wl.itc or -nav disc a-.'i rotate the c. The intensity of the ;;rav will l,e chan-e-i but there wll he no coI„ur perceptible. /.,■., while to a certain extent tne nitrodnction of colonr may chanue the intenM. v it e a chan^a- winch will be above the threshold with re^anl to H^du inter! Mtv. bm n..t w,th rei,^ard to colour quality. The addition ueces- >a:_^- m oroer to can.e a j,i>t noticeable chanj^o n: inteuMtv will dMcr ,or the ditierent col„„r. and will be inver.eiv proportional to their bri-jjhtnevs. A second n,etho.l i. that of the flicker photometer, a. :'^':"''"'' ">■ ''^"f— "■ X. K i,- who f„nnd th.,t ■the .iccun.cv attainable with the flicker photometer a. ^.t proeut constructed, and ,..si„,. H^m „f ,ii,T,rent colours a "i-t .pectrai in hue, is about the sa„,e as with ordinary photometer^ UMU^r U^],^ „{ ^.,.,,^.^,^. ^,,^. ^^^^^^^ ^^^^^^^^^^ „ The thin! method, which wc have n.se.l in the following expcrnnent., has been described In Kirschmann. • an,l later bv irotessor Cruber,' who apparently did not know the work o'f Kirschniann. It is well known that the manifoldness of o.lonr tone, .le- crcases wuh the appru,.ch to the e.xtrenu-s of l.^ht inteuMtv llus chan^.e of colour, the .saturation bein- couslau- w „nlv witlun certain limits independent of the inten.sit;. . and in the ' ' '/■■ >■'/. pp. .so (•/ seq, \o!. i,\, pp. .129-.J46. 1 "=■■'';, ^(<, tier l-jr>i ''"^ w. -■ " il'hilos. .Siii.i., ■v'^ nu,.t t.c.nt ^ivKial r.rR-^.nl..tinn ..f H^ht ,.n,I colour seiwU.m is prc.vicKd t-r 1.V ;;ivin- the l...sr oi ilic colour cone an ludma- tiou t.Avar.ls lliL- .,xi-, .o that v.llnw ..ccupics the hi^'he-t. l.hie- viokt the lt puMlinu. ■■ TlK- >a,Iv pair of e..r.ip\ir.entaiy colour-^ -Ahidi have their niaxinimn .-aturation at equai inten- sities nn.>t therefore he at the eu.ls of that at n-ht an-Ie- to the axis, an.! this coudUl-n ■amI he satisfied sniiK where r.e ir red ird hbie-Kreeti."' It has s,,inetinies been maintained that black can be s^eu Letter on a white back-r-nnd than wlnte on a l/iack baek- ^rround. and, exami.les of printe.l letter- are cited, m \'Un,\. This ,s true ..nlv beear.s,. we have shaped our letters m Micli a wav that thev are adapted T .r the Use of black on wdiite ; the inad.iatioii bein-; different when white i- the surtaee o! the let- ters r.iiher than tlie background. Snnllarl^ Vou /aim lias s.,i(l that vellow on a blue back-ronnd and -rem on re.; ..wniMre easilv s^.n tlian bine ••" velluw and re.i on -veeii, and he ;Utnbiites'this t.. the ,|nalit;es of the colours. Unt if there is such a diiiTerence, it nn-t be due t.. intensity rath.er tlnui to colour (pialitv. i-or if we pL.ce, for example, a bl lek surt.ice one inch s(|n..re coiicentricillv upon i white cardb,.ard ,-4uare of twentv inches to the si.le, we sh..ll have ,V.9 ^'l'--'^^' "'"■^''^'^ "^ white' ..nd one xpiare inch of bl.ick. Let ii- .issv.me that the iutensitv of black to white is as l to 50, Then we ^l.l^e the mtensitv of the whole snrf.ice equal to ,v<'* >^ ,>" l'-'i~ ' ■ '"''' '' the wh<)le surface li.ul been white, we should h.ue It.id. an niten- sitv of 40U X =;>.. Sm while the whole inlensilN w.^uld be _'(M)00, the existeue.'or uon-exist. nee of the black .squ.ire condili-us a difference of iulensitv of _,«,;,„ of the total intensity. On the other hand, if the lar^e surf.ice is bl.ick. it has a t..tal intensity ,,f .V ,., ,iud tile white square will iiow cause an incre.ise ot ,',;V, to the total intellsitv. The same i< the ...se with vellow on a blue back-round, ,,win.- to the ^reat difference ..f inteUsUv of the colours, vellow Used., We in beinj; like white, pi^MUent colours ,ire lC.rsc';nii.iun, Co.'our Sjluration elf. Vel VII, [. y)i, I like bl.ick, if hij^dilv saturated ,1V cilcukite b;, the .d.ove .\!iiprKrtii J.iuruai ut f-vcholot^y , 49 iiictlioil tile i>i>ssil)iliiics in tiu- rli.m-r ..t inti-n^itv hv tlic ^nix-rpMsitiun of each on tlie uiIut, aii'l it uill he iM^iK -nii tlint ,1 yi-ll with re!,'aril to tlieir intensity, ami cnseiinenlly as to the nie.is- nivnient of tlie l)rii,'iitness of culnnrs, tliere are widely (liiiVrent ' icws heM. Whilst M;;:i-ter!iLr^. i~.:- in-tanec . l.iitns th.it i!r impressions of even coniii'.etely different senses ean he eoinpareil with re^janl to their inteiisitv lin terms of nniscnl ir sens.itions;, there are ipihers who would .seareeK- aihni' that lAiii two diiTer- ent colour sensations can he so Compared. Most ■■'" •'' ever, who Iicddthe lattevview hav( investi'^ate the faet- 1 tllo.e, how- I serioii> atteni: t le \er\ fact that colourless li^dit can always be re-ard.ed as th.e s.itnration zero of ,,n\ tolour sh.uld convince ever\l)od\ of the fe;isiliiHt\- of the j'hotonietrv of • olours, even if only indireetl\- ii\ conip.iriu- them with colour- ;. -, !;-h.t. Her::;-- h.ol.ls th.it everv one of his f,,;ir fundament,!! i-oloin, ^ •■.er'.s, apart fmni its ])eree;\e'l intensity, a hri,L;htei;in- fin the c.ise of \er.ow or red i or d.irkenin- i in the e.ise of -ueii or hhiei inrir.eiice. Hillel,; .nd his tried to est.d.lish this stan.l- poiutof Herins; experiment. iH\-. In weak illnmin iiion coloured objects look colourless ; .:t the s.une time the-, eh.in-e their in- tensit;.- \-alne, as is iiecessarv .icconliuL; to I'urkinje's I'henouie- non. Ilillebrand determir.ed in ,i dark room the intesisitv \.uue ot a variai>le riu- of M.,ek .nidi white. Il.uin- oht.iiued these \-alues, !-.e m ide, h\ nuaus of di^cs, ,i series of nuxti'.ies ,,f colour with hl.ack .iiid wh.ite for which the inteiisitv value should h.ue been tlies.iuie, .ind then couiparei! these dises with one another in full d.i\li-ht. He found then th.it thev shoued intensity rei.itious \er\ different fr..m those which thev h.id in weiK idnininatioii t!;:. Ilehnhoit/ h.id come to the foi io\\;;i- cotlchlsiou re;j.irdiu;^' 111 of coiourc'l and uiieoloiired, '.i\s, " with lie e j.' -s;.,:..;y ot ex.ict couipar \:ht. "One cm compare dilTerent colours, re;iar(l to intensit\, but the cert.iinty .lu.l evactiiess of siu h eoui '•'•:-■•; :- !.ir leSs th.iu in the comp.;ri> .ii of !i-lits of the s.mi' colour.- IK states th:,t h. ^.4"^^:- • ■'^'■^"^'■ ,,,„,kn,^.x.ctjml^m«^"ts ^^ the ao^vc- .n,.,uo.t recent inve>tt-at,> n . . ^'^^ . i.-^p,.rimental l-.,v it in:iv 1,1 , ' Ut'ce. iFat noon the total illnnunation he for instance, at the >oltK^. .^^ .^^ ,,,,rc^cnted .,„re>entea hv ..--e h-nu '"^ ':":;'^^^.^„,, ,„„,ues after .ttn- ''^- --■ '■'''' ""•" ^'r\^- "■ n a onr nunntc. aft.r -unripe nsehvh-^^than . """•^'^''':^ ,^;, i, ,ue afternoon there l,v 1...,. than 1 5" i"-^'i74^- ^""•'••^'> .-.^ .,,- Uk- ilhun- , ,.,Hn.r.liniinntinn uUhe iuti.n»it\ 01 ui ,uin.eao,nvS»'>''l'".-,^lnnnt iHnstrate thi- lact .V -,. nil. in t'll sunset. \\e e.m thr-.v.-h 5- t>M,.- luper^. at ,. ?•">.. ^ ^^^^^^ .^^ ^.^^ Therefore .a the ai.nure, the a>e ^; •'\ 7' ' ' 'j-^,^ ,,„,..nui.th ..f the l„-i„la(l.Nliuhtatn>...n ;> -tiH ]"".-^^ ■ ?!„■ uiMrnin- and late in the alt.rnn..n. „• , r ,h^. 1'-'--^ ' ""^'r'' ""^\'r ^;" ,,,.;.ct hv K>r.ehmann in the previous puhlieat..n on the ..mc ""^^^ ^ ,;,, ., ^,,Uter !n>.-ve-n,entionedarticle..e,.an. .-^^^ .,„Un.l,henKuletrua<. th.au ^.m ^ ^^^ ^^^_ ^^^^^^ ^^^^ ,;„„.•• Th. value ot these tnal. is n t v.tlneless. ,Uan,eof inten^ity wonhl seetn to UK K. t e .^ Ucal eontrol trials are only tlw.- wue . ^ J' ; ; . ,^^,.^ :, i„,,^ ,..>UKa ; f..v hv ehan.in, the '"--; J^^j; , J „,„,,.,; ,ues- las that -a ukvc ehan,e of saturatu.n - v- ■■ - I iu\m\nAu. rhysMoZual Oplu-s. ,.. 2,,8. •\ I clian-re of intensity." KirsdiiiininV I this. Th. way in whicli Pn.fc-s>„r (.uiIkt tries to rmmc::.- this :.M.!t uith the hvpothesis ,f Hc-rinj^'-s •• \Vhitc-\-aIui;. " ti.con- ■.v.:'ch u c-ntradicts. is «tre,ndv intcrcstin;^. Wl.,.,, ,:ot onlv • im.Ljcx.l s.iinn.ti.m hut alsuohaiiLrtsof iiitfiisitv ■ kIu -••the :ulditi,,n of white or black. ;^rcat cleviatio„> u.r.'ob- ■■■ •■ Wlui; ^^]nw was added the oh>erved values were .:iio>t always too dark, while .p!dilio,i> ,,t M.^k iiiidi t'" .^ vii ::.'!.s considerahlv Mni'ler ; fur one observer there were no -••:at..,n^ at all. Thi> ,:,ay eaMl;. he accounted for l,v the fact ■ !:; .:.! colour, m hi;^her iuten^itie. teud toward white' in -;.u -,„,.„. ,e. toward black. Tor exau.ple. if a red nnxe.i •"■:..' u,lite.,e u>ed. Hot ou!n i> the situratiou lowered, but at J.e Mi^ tnne tne mten^it;, o, ;h, red is increased, aud cousequentlv .^ e.lect must be ditlerent, accnrtdipn,u. : the ob.erver A,'//Vtv^ that the inteusi^v w [s not chan:^a-d. Crubcr concludes tliat it is possible w'th Mie necessarv practice of the observers, to carrv out connurisons w:th exactUttde to within a few decrees, which agrees we:: with •;ie previous results of Kirschm.inn. •iruber made an iuterestin^ series , ,f ^j.eriments ,„ older to compare v.dues gained in d.uli^ht with tho., which for the -nne co!,.;r discs ,„,d the s.nue observers, accordni;, to H.rin^-s :>.! H.llebrand-s nietho.i, were obtained in wck ilh.miiuti.m. i ae rotation apparatus w.is set upiu a d,.rk room to which lii^ht ■ ':;!:lted t!irou-h a narrow slit covered with .1 milk .^da.ss. ^ 1^ 4. '^.i 4 #: '^2 'III After the ..l..rvcr-, cvc h,.-! l-.onnc accu.t..n,o u, .. ... i,,;„nination, the disc l.u.kol ^r.v un mtat.-n an-, o.na. Wy.u- l;;:,! .ith 1-lack a,vl uln.e ,li^c. It wa. ...and, cxact.y a. l„v.- vven- velativ-!v darker and ,v... an-: Mne :ek..u.l> ImJk. ih 111 \v. da'> i'._:^lit. 'it- T:,eex..erin.enl> which. ;nu.er coudncu^, in a -larU ,■ .■uliao.h;nr-b!iu.l .ecu, further U. >h,.v the ni,i,.^i.nht Herin-s special -WhUcA-alen." the„rv. It '-—>-;;--; .„,-h:i.il that the disappearance .. cu..urs >" -■,>\."- , Uo!.c.,rep<.uUtotheviMon.ftotdc.onr.l,lin.. .. ^ - ,,„,,ins nnlv the excitati..n ..t the hk.ek-wh.te suh^ta u.. H.-K-e f,.r thuu the nurnial inten>ities uf the clour, must he U,..>e which :,-, >ee in weak ilhuninati.-n. aiul there,.re to a u.- .reenclonr-hlind^reen should look hri,nter and uu . U, n, to ar eve ol u.amal colm.r sense. He lound. ho-.se.er that :;;;;;the oriental trial for ,reen.ave a. •'.'^•^--- ^^ for normal persons, vet in ihe .l.rk loom ^reeii h.oke,>e . was not >hurtened. Oue ueul onlv sav that under .ten Lditiott. no wonder that red l.,oked darker ,han to an .ve o, luirmal colour sen-e. . , lu the experiments which .e conducted on the m,- 1.1 y o, colour piK">ents h> differeut ilhuuinatiou, .heap, aiatu. u.d w..s th.t oiD^. Marbe made by /imme.man and altered to si the tlutoiLH-. .liscsused wereot Mdlou- ti.irticular iicods ol tlu case. '"'.,, , .,.,,,. Bradkv coloure.! J.aper ou a black and white backK^ronnd. 1 u H ^of coonr wa; a constant, the ,ray a variable -piantitv. I he u en>itv of the li,ht was relatively cutrolled bv comluctn., Z tvi-dsiua roou. admittiu, davli.ht tluoa.h a .,uare lindovv of fonv bv forty witli tlit- t-piscotister wvT.- iniilc, MiK- will] I'ruk'vx.r Kir-clr.ii.,;!]! .is an i)list-r\ i.-.-, tlit- otlur with tin.- writer. U \v:is iMimd that for .-tnilitjlu, plai. (i>i\Ii,!L,'lit, (luli^-lit tlirMiiMii tiK- .iiicrtin-L-, .nid f.ir 5, u\ 2\ y\ nnvi ;Mti>saL-ii:,pir-, ii.iii...\ini.it<-i\ .n-cur.iiL- nuMsiirt-nit-nts (..juld !)c chtaino!. !)ut f..r Iowlt intcn.^itics the rL-.suIU lUid U> he f(>in])nti'(l from th..- data alrcadv o'ltainw!. Tin- fon.nviii- • .'.k- sllKWS lliv !Uti.-u--i;;(. > tisi.,; ill ,,iit ^ xpiriniiiit- : If for brii^ht sunlij^ht the intciisitv he callet Tlieji for pliiii dnyli^hi tlu to he .ip]ir'i\i!nateh. .\r.:l for the aperture, 5 ti---.ne p.ij'er.-., Ml\ 1 Je caiie i ; _« I.LH 1. 1,1 K)0 !.ai-; \ >.\-,i~ f- nid tO,CK)r),fxx> (appi u.Miiiat .•ly ) ^1 1,, ,. n, ahout 'These emp1r1c.1l!> a»cir'...i!if.l reMiits wo m,t asree wiUi llie iUiii,.!i.l» .,f the jihysuMl ilie.iry of ahsorjiti,,!]. Theoretically if one diilti.-iily traiiMiiitiinj, Iilale (Kroiin.l kIhss, li>siie ii:i;.t r. vie pc-mits the iwwiige of 'of the incident tight, the quantity i.f li^;ht IraiiMiiilted throujjli 11 j.Uti-s (,iin!it tu I'l- — Tin- rensons f..r itio i|..'vi.iliims may Iw s.,ii;.!it in the fnllowinv^ cirfiiiii>iaiic. s I. No traiisriiissirm ,,f |iyi,t ,„ .,l,,.,;,|it.iv .IifTciM-'. There i» aiwiv* a ituaiitity .,f li«ht the path of which n.-,siiiii,Mlie form of a 111. .r.- .,r l...« ni'ii/ar trinuli. II The p:issa),'c- of this retriuti.l iuid pp.l.ahl' Uirht finiU with i\.ry a.l.htioiial plate more favouraljU- eon. liliiin« ' '■"»■ liyhl Hhn-li i^ not ■:■■•■ • -:or surface of each ■ ; irom the p!:«ips heli.. .. ,::. . _, , .^ . , ^ ^, ,,.,, ^ , ;'in. ■ ■. '■'•• ve that these comlitions have a certain fie.nrinjr i'«'"' "ti tin Mi,..r'. if Iti.^il in xeneral. It is alwovs as.sunieil that i I ,!,.4,i ..1 lies the i|n.inlitv of ■ .i!>sorhin».' l»jilv: iu tl.. -l^^.r cnm.encn^ with t.. l„vv.si ami approaching the hi^-hc^t ill-,nninat,.>n. U O.uml'nK- n.nuukcl at the -utsc-t tl-.t -om. .-l.cn.^ ,.,i„ .ith the p.v]n.lice tha, 'ti^ ■'"^''-f 'V^^jt; ^ intcnsilv irrespective ..f the clour. It cannot be .lenicl that the intenMi> III 1 iiul'Mnent more uncertain— nre-^cnce Ot colour (loe> make llie JlUl^ine.. , • . ; .Ln verv conM.lerahly-l.nt with practice t . uncerUn.v . 2k reduce.1. W . thev.fore f.auul it valuable to make fir^t ._ "^Tumuber of practicc-experttncnts in a constant .nt^nsUy M ;::;,ination ulayii^lU,. to accu.om tl. obscr^.r to the coh. r ,„d to tnaki,>K exact statcnents. XU ;-^/;';;;'^ ;;,. „K-th...e., „ ,„„ ,vcr. the onlv ones obtained by the unconscious meth.Hl. ";•..::.,. fouu.1 tha: the mean variation for blue vv.. cousn.cu- ous' V -reat. « >ne wuuhl have thought that this wouM mvandate ■-:..,nent about yellow, where he says that the men, ,,r vellow is als., esiH^cially ^reat, -'f --"';^; "^ M.ch .eiiavi.mr bv the fact that velU.w is much Whter ha . ; .thercolours;an.l that the discriminative sensib, Uy .ol lo s thi- ; uv of Weber. With regard to the blue, however he accouilt- f : th greater inaccuracv 1, attributing it to the circumstance t tSs with that colour bein,^ made first, the observers : ;Mt sufficient practice ; he refers als.. to othe. chsturlmi, ,' wall the blue we fouud that umlormly there u a. ;,,,,,,„„ ,.f intensity with the decrease of the ilhim.natv.n ; L the omtrarv in mo.t ...■. the number of decrees was In.d.e.t i, , .. t illmnimitu^:^ ,,.imented the me.m varia- ,: .- nalurallv the highest in U.we.t mtcUMties. I In- ^^a. .ccted. uwinK to the increased difTicuitv m seem,^ the .. .., • ■• lutheli ^.'^ •'•■'. u.., f:..;iuntlv This iimv '■<• corrrct f"r ihtIC' I 1 ■ t ! ; .nil . . ltie .iiid in .dl itensitics was 3.45. It will be remembered thai l.,i ..ne intensity the averaj^^e mean variation ot the five obser\ers in !'rofc.s.>*or Kirsciiniaini's esperinients in I,uiizi<^ above referred ■ > wa.-i approNim.itely 2.5. Wlun tiu intensity was rednced > twenty Ussxiv papers there wa.s still a binisli colour visible ; • 3>jall trace of colour was jruiie. thotiLjh the intensities eotdd ■ill be jnd:..red wlien 40 and 50 tissne {lapers covered tlie ai»er- ■r. In .dl the colours it w.is hrand t.i be ninch more dilTicnlt I . make ctnnp.irisons when tlie cohnir wa-^ distinctlv present. In the lilsie there was with the decrease uf tiie iiUcnsitv a steady ■••crease in the number of ile;.^'rces added, thouj^'h there occurred ,in occ.isional fliiclnatioii. The residts oluained by .\llen and Wi'-.Mi are cNCejUional in this re^^ard, [iiobablv in con.se<|iience di-.tnrl)ances in the ilhnnination caused I>v a chmdv sky '.n- from '.H -'o tissue [lapei- imm NMiii 30 tissue p.iper> from 5J In the blue-;jreen tile tendency was rather .1 iiecrea.se in the dejfrecs from full inten.Mty down ti> 20 tissue pajx-rs .< the aperture, and in.m tiiit t>) the lowest intensity .1 ::uii i-e in ever>- case. .\t 2u tlie observer could not tell lour was blue or j^^reen but inclined to call it blue. 31 tijt voioiir was far njure blue than ^rcen. At 40 it was i. .... ^ t n I ('.;..».... . .'11.. ! * - ^ inlensitv extendi lo 03 ; t.' --.! lo s() )',. 56 u-ult. iK-in^ n,ncl> lu.h.r tb-UKl. hnwc.l a cnn.r^tcnt .^.^vn^v tcu.k-ncv u..h ih. decrease- „{ iUnininatinn, from an avcra.L <)1 5^-77 ni ni.^livsl inuminati,.nt.,anav.ra,. ..f ,..,U .h.n ,,- luper^ enured the aperture. The decre.u.c wa. nowhere lar,e ; there ben ;■ n . oU-t used n,ore of hhu- than of red, it .ave a ven- s^,,h though re.n,lardin,inut,on.itl-, the fa!hn,nUenMtv. ^\ hen .o tissne papers .ere added the observer could no hMjU^r - ulonr. In the trials be^innin^ ,a lowest in.ens.tv o, Ulunnna- ,„„ ,,, .avancin. towards the highest, the colour r.ap,K.tvd vlun ten tissue paiK-rs cvered the aperture but n n>..kn.K ; U tn Is in thi! intensuv the colour appc.red and .h..ppeared :^nd t '. The average nrean variation at hi.he. uUensOy 1 . rvrs WIS x^n- at lowest intens.tv it was 6.04S. ,or all ..bservers was .V)3, '^ ..,;.. of violet was The avera-c mean variation for tlu •'^''';;^;r;h!nv;d a consistent downwar.i tendency till ,. tissue „,pes controiled the iUuinination ; but when colonr was no r r present the nuntber of decrees ros. when 30, 40 an<1 50 i espectivelv coveted the apertnre. The tendency down- w ^i iJ^id was in every case observ.d.le. In lo^^^t .«te,,s,ty :.t there .as stiU a trace of red left it was ^^^^^^^^f^^^ ,„Uer th..n the black disc on which ,t wa. 7""^^^: J^ ^^^ .1 (.,r one observer bv insertin^a sectorof «, ^^l"^;- ^ a nnon the red rin« of the disc. < )ranKe-red was verv much 1;;:: : exhi ited t^c characteristics of red thron«h.>nt. n ;;;;^;Uitythee.t.n..w.efr.^^^^ WinjiM-i.^.S and at lowest mtensi- from iiLMrK crcnii o.l.Mir in Inw^.t im.n-itv tlir. .i:;;;? ■, vdluw witli .1 tiii-c Ml ,,r,ni;^r,. ,-,, it ,,|, (,, , ,,.,j^^j,^ v.-Iluvv. A. utli'.rs !uvc .ilr.,u!v pnnnul mu, ;la- nuMii v.,ii,ti.,n w.i. extruiic'y I,ir«e an.! tla jn.i^^nicnt^ vari.-,! oui>i,i^r.,l,;> f,,r .lin'on-nt ob.. - "'.■(■r- ,ui(I on ilinViLiit d.U';. !:^tlu- 1.1,1... 1 t,.VIII il^;;;.s^-<.r,5,tlK■nppc•rnnn,!..;,n^^.,^s nuhcat.. the nninl,er <,1 dc-rces „f whit.^ cuntainoi in tin- -r:n llKit \va> l.MUKi wnial in intcn^itv with ih.- r.,I,.nr<.\\xr nnin!)LT ;^i\v. the- niL-an \arialiMn in dc-rcc-. Alter Hi, .xjKriniLiUs witli pi-nicni CMlnnr- in rc-flcctcl li'Aln, It wa.s found d.M'ial.k- to make a lew trials a!>o with transmitted li.luitler was an arran.^^emeiit to hold alw.rbiiij; pLues which tmercepted the incident li;,du. Three colours were thus examined 1 i!e first was a combination of j,rdatine j.Iates which allowe. 1/% ir, ID. , ?5, ^— ri „ — - ir. <* « fi f -. u i «- ff^ ; »/", « = 5-B ■^ T rr "N in - w". -T ji *r ir: P* *0 rO ■7. ' " r* ^ O^ y^ ~ ^ -7. .o- — »>. — _0 3r: t/1 I-* r* u> to ?? r-S &5 ^ -;, J*^' S" ^ >t ~5' "3 j?7 %m ^ 6o ^1 n -.. -. i,« r.-'. u;" 15 f' = - ■-*• '■'- .if ■? 'ii'r 'i 5 5 c ^.a c- '•t •♦ I , S-- ST ^ U-; ■ - w 'O o^ - ir r- y: ^ tr, ( r>> T P* f^l »*; . ?- C-- ir, " H5 . — . CO — T y: '< 3^ f^ rf. ' ~C V. f^ f^.-i ;^ -r 'y- rr. t*'. t J^ -7 V. «/". "N f , ^ f't Irt -^ ir^ •^ -TO o u:^ !?2 ^« ^' if. — tn r^ H i ic-g I/-, "N IT. X T -* ,2 ^ OS ^ -•'^ -^ -vC <:t uu T \r,I,!-, lX.~Ci.i.(irK : Ri-.i'- ,Vo,U,c.-.l l.y ..U.o,i,l..„ ,i,r„.„h . plate, of r.i .daUnv. .UfTerenl in In,. Si'KCTKOSCOWC KXAMINATIOS I Vi-il.k- part of the spcctnun : Trcni red .'nil i- ' o; /'/' Maxiimiin of intensity at al.uiit f,;o hy^ I'l'. When the aperture with the rcl K-'atme V^^^^^'^^^^^^^. papers an.l tl.al of .he white wUh .n, ^^'^ ■^^'^:^^^^^;; ^^^li the ep.V- f lie pUvsi.al i„te.,sUv „! l.uth was J' -'"^J^ ''"; '' i„t eq"alitv could be cot.ster. they appeare. m. lunger ^-l^^)^,,}^^^. I„ t. is n.anner re-eslal,Uslied by an ^''I'l'"""^^'' ••'.'^""''''" 1 \* f,, 'X r suit \>i four readings : the foHowiiiK e.iiiations were ooUii.ed. each Ik ii.K tlie in intensity I .;'» \V;nI, : Keil !n-,i!li,' 'I'Ar.l.l-; X — CmI.ihk : C.kkkn. ITuducM l.y 4 bUu-.grecn and l yellow-Krecn ^>:\Mnv fdnis. SrF.CTROStOI-IC l-.XAMINATIllN : Visible iiart <>f the si>i-rtr>ini ; soi 4"l F/' Maximum of intens.tv at alH)Ut 525 S^l /'/'■ , .!,. r-d iiul IS "ver the white the two openings With ; tissue paper* over tlie rea ami is weie eiiual in briKliliiess. ,. . 1 Then the following e.luce.l by j blue. . v.olet ...d i «reend,lue gelatine lilms Spkctroscoiic KxaminaTion Visible part of the spectrum : 44^ /"/' '" e"' Maximum of intensify about 475 /*^- With ,. tissue paper, over the blue anO^S ovc. ^^^^^J^.^^^T^ ^^n::! a^:=^^^^ i" = -^ ^ J':^.lc:ti.er^ ■ . White (in i itensitv) 36.1' Bine ; Blue ^^^xxni^V. '_ .■ 97'*- " :; .. i^,*.. i % :iuiU-..-,l„,«v,l >tilla^,i:„i„;^. uii.kncx 67 , '^''"■"; ;-''''^:^ ^'"'^^- I-'^""'^ '1>- -H^^rcnt i.!,,,v,onr „f tlu- o...,n>,..,lK. n^ln .„,! l.ft .,ul .,f th. Mvctrnn, .lu,, ,l,..:r pt-ri- "'" ^'^'' "' '■" ^^'"'^^■'^'■■' •'■" ^!""-n,o an ,„,lit7 rcU ..r.c„ flu- nUu.MU ,n ,v,iu.cd ■!hnn::,,u,,,:, will 1.. ..,,,,,,,,,,,,, ,,,,,^. ^^.,,,