IMAGE EVALUATION 
 TEST TARGET {MT-3) 
 
 
 .V 
 
 
 Z. 
 
 1.0 ^Bs 
 
 I.I 
 
 1.25 
 
 
 2.5 
 2.2 
 
 2.0 
 
 !.8 
 
 U ill 1.6 
 
 
 ^3 
 
 ^^t^ -/ 
 
 >^m 
 
 
 V^/ 
 
 #1'''^ 
 
 ^ 
 
 
 >^ 
 
 Photographic 
 
 Sdences 
 
 Corporation 
 
 33 WEST MAIN STREET 
 
 WEBSTER, N.Y. MS60 
 
 (716) 872-4503 
 
 *•' . *i 
 
 \'B> •■ : 
 

 C/.JL 
 
 CIHIVi/ICMH 
 Microfiche 
 
 CIHM/ICMH 
 Collection de 
 microfiches. 
 
 Canadian Institutcr for Historical Microreproductions / Institut Canadian de microreproductions historiques 
 
Tschnical and Bibliographic Notes/Notas tachniquas at bibliographiquas 
 
 Tha Instituta has attamptad to obtain tha bast 
 original copy availabia for filming. Faaturas of this 
 copy which may ba bibliographically uniqua, 
 which may altar any of tha imagas in tha 
 raproduction, or which may significantly changa 
 rha usual mathod of filming, ara chackad balow. 
 
 0Colourad covars/ 
 Couvartura da coulaur 
 
 r~7j Covars damagad/ 
 
 D 
 D 
 
 D 
 
 Couvartura andommagA* 
 
 Covars rastorad and/or laminatad/ 
 Couvartura rastaurAa at/ou palliculAa 
 
 Covar titia missing/ 
 
 La titra da couvartura manqua 
 
 Colourad maps/ 
 
 Cartas giographiquas 0n coulaur 
 
 Colourad ink (i.a. othar than blua or black)/ 
 Encra da coulaur (i.a. autra qua blaua ou noira) 
 
 |~~| Colourad platas and/or illustrations/ 
 
 D 
 
 Planchas at/ou illustrations an coulaur 
 
 Bound with othar mctarial/ 
 Ralii avac d'autras documants 
 
 Tight binding may causa shadows or distortion 
 along intarior margin/ 
 
 La re liura sarria paut causar da I'ombra ou da la 
 distorsion la long da ia marge intdrieure 
 
 Blank laaves addad during restoration may 
 appear within tha text. Whenever possibia, thesa 
 have baan omitted from filming/ 
 II sa paut qua cartainas pages blanches ajouties 
 lors d'una rastauration apparaissant dans la taxta. 
 mais. lorsqua cala itait possibia, cas pagas n'ont 
 pas M film<kas. 
 
 Additional comments:/ 
 Commentairas supplimantaires: 
 
 L'Institut a microfilm* la meilleur exemplaire 
 qu'il lui a itt possibia da sa procurer. Las details 
 de cat axamplaire qui sent peut-dtre uniques du 
 point da vua bibliographiqua, qui peuvent modifier 
 una image raproduita, ou qui peuvent axiger une 
 modification dans la m^thoda normale du fllmage 
 sont indiqute ci-dessous. 
 
 I I Colourad pagas/ 
 
 Pagas da coulaur 
 
 Pagas damagad/ 
 Pagas andommagdas 
 
 Pagas restored and/oi 
 
 Pagas reataur^es at/ou palliculias 
 
 Pagas discoloured, stained or foxei 
 Pages dicolories, tacheties ou piqudes 
 
 Pagas datached/ 
 Pagas ddtachies 
 
 Showthrough/ 
 Transparanca 
 
 Quality of prin 
 
 QualitA inigala da I'impression 
 
 Includas supplementary mataric 
 Comprand du material supplimantaira 
 
 Only edition available/ 
 Seule Edition disponible 
 
 I I Pages damaged/ 
 
 I I Pages restored and/or laminated/ 
 
 r~~7| Pages discoloured, stained or foxed/ 
 
 I I Pages detached/ 
 
 r7] Showthrough/ 
 
 I I Quality of print varies/ 
 
 rn Includas supplementary material/ 
 
 r~| Only edition available/ 
 
 n 
 
 Pages wholly or partially obscured by errata 
 slips, tissues, etc., have been refilmed to 
 ensure the best possible image/ 
 Les pages totalement ou partiallemant 
 obscurcies par un feuillet d'errata, une pelure, 
 etc.. ont itib film^es d nouveau de faqon d 
 obtenir la meilleure image possible. 
 
 This item is filmed at the reduction ratio checked below/ 
 Ce document est film* au taux de rMuction indiquA ci-dessous. 
 10X 14X 18X 22X 
 
 26X 
 
 30X 
 
 yi—r 
 
 12X 
 
 16X 
 
 20X 
 
 24X 
 
 28X 
 
 32X 
 
Th« copy filmed her* has been reproduced thanks 
 to the generosity of: 
 
 L^iilature du Quebec 
 Quebec 
 
 L'exemplaire filmi fut reproduit grice i la 
 g^n^rositi de: 
 
 L6giilature du Quibec 
 Quebec 
 
 The images appearing here are the best quality 
 possible considering the condition and legibility 
 of the original copy and in Iceeping with the 
 filming contract specif icationa 
 
 Original copioa in printed paper covers are filmed 
 beginning with the front cover and ending on 
 the laat page with a printed or illustrated imprea' 
 sion, or the back cover when appropriate. All 
 other original copiee are filmed beginning on the 
 first page with a printed or illustrated impres- 
 sion, and ending on the last page with a printed 
 or illustrated impression. 
 
 The last recorded frame on each microfiche 
 shall contain the symbol -^(meaning "CON- 
 TINUED"), or the symbol V (meaning "END"), 
 whichever appliea. 
 
 l\Mapa. platea. charts, etc.. may be filmed at 
 different reduction ratioa. Those too large to be 
 entirely includsd in one expoaure are dlmed 
 beginning in the upper left hand comer, left to 
 right and top to bottom, aa many frames aa 
 required. The following diagrams illustrate the 
 method: 
 
 Lea imeges suivantee ont M reproduites avec (e 
 plus grand soin, compta tenu de la condition et 
 de la nettet* de l'exemplaire film*, st en 
 eonformit* avec lea conditions du contrat de 
 fllmage. 
 
 Lea exemplaires origlnaux dont la couverture en 
 papier eat imprimte sont filmte en commen^ant 
 par la premier plat et en terminant soit par la 
 dernlAre page qui comporte une empreinte 
 d'Impreaaion ou d'llluatration. soit par le second 
 plat, sdon le eas. Tous lee autres exemplaires 
 originaux sont tWmim en commenqant par la 
 premiere page qui comporte une empreinte 
 dimpression ou d'illustration et en terninant par 
 la dernlAre page qui comporte une telle 
 empreinte. 
 
 Un dea symboles suivants apparaitra sur !a 
 derniAre image de cheque microfiche, selon le 
 caa: le symbols -^ signifie "A SUIVRE". le 
 symbols V signifie "FIN". 
 
 Lee cartea. planches, tableeux. etc.. peuvent itre 
 filmis A dea taux de rMuction diff^rents. 
 Lorsque le document est trop grand pour dtre 
 reproduit en un seui clich*. il est film* d partir 
 da I'angle sup4rieur gauche, de gauche i droits, 
 et de haut en baa. en prenant le nombre 
 d'Images nteessaire. Les diagrammes suivants 
 illustrent la m^thoda. 
 
 1 2 3 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
/^ 
 
 COLOR-BLINDNESS. 
 
 ti^W 
 
'a> 
 
 «• 
 
 f 
 
 ^ 
 
II J ■ ' ' 
 
 fvSv V-. 
 
 r., 
 
 «»(■ 
 
Resolution adopted by the Board of Supervising Inspectors of Steam- 
 Vessels, January 25, 1881. 
 
 Resolved, That the thanKs of this board are due, and are hereby tendered, to 
 Professor B. Joy Jeffries, of Boston, Mass., and Professor W. H. Carmalt, of Yale 
 College, Now Haven, Conn., for their thorough and exhaustive discussion of the im- 
 portant question of "color-blindness," and valuable information imparted to this 
 board in regard to the various methods employed in determining color-blindness in 
 persons ; and that the Supervising Inspector-General inform the gentlemen, by letter, 
 of the action of this board. 
 
KAM- 
 
 (1, to 
 ' Yale 
 (5 iin- 
 I this 
 588 in 
 ^tter^ 
 
 COLOR-BLINDNESS. 
 
 KEMARKS BY Dh. B. JOY JEFFRIES, OF BOSTON, MASS., AT THE TWENTY- 
 NINTH ANNUAL MEETING OF THE BOARD OF 8UPERVISIN(^ INSPECT- 
 ORS OF STEAM-VESSELS. 
 
 Tlie special stndy of the physiology of vision has been iiitiiiiatelv 
 assoc-iated with my professional work as an ophtlialiiiic snigeon. Color- 
 blindness Ironi disease is one of the symptoms we have to deal with. 
 A knowledge of it as a congenital defect, not associated with any dis- 
 coverable lesion of the eye or the brain, has for many years impressed 
 me with Its probable danger on land and sea. Scientists or physicians 
 have had, however, no means of detecting it so qnickly and so'readily 
 as to enable them to thereby engage the attention of those in authority 
 Avho had the power to establish rules and regulations of control for the 
 protection of the community from this heretofore hidden danger 
 Therefore, as soon as my friend Dr. Frithiof Holmgren, professor of 
 physiology at the Uuiversity of Upsala, Sweden, published his mono- 
 graph on color-blindness and its dangers and detection, I saAv that his 
 inothod of examination Mdth the worsteds was so sure and so rapid in 
 the hands of an expert, that I had no longer any hesitancy in publicly 
 calling attention, in the early part of 1877, to the danger from color- 
 blindness on our railroads and on the sea, from the necessary use of 
 colored signals, &c. I commenced investigations bv his metlifKl, and 
 my flrst results are in the Ninth Annual Keport of the Board of Health of 
 Massachusetts. I was soon urged to write a manual upon the subject 
 incorporating Professor Holmgren's monograph, which ha<l in part 
 been published by the Snuthsonian Institution. I accordingly wrote a 
 book on "Color-blindness, its dangers and its detection," "^giving a 
 histor\ and explanation of this curious defect, the results of my own 
 personal examination of many thousand males and females, those of 
 other examiners in Europe with whom I had corresponded, the various 
 methods of detecting the defect, and the amount of it in any given 
 case; the explanation of how it had and does escape notice or detection 
 the rules and regulations of European countries for its control on land 
 and sea, and a bibliography of some seven hundred articles written on 
 the color-sense. The book quickly attracted the attention of the medi- 
 cal departments of the Government, and it was adopted as a manual 
 to be, with the Holmgren worsted test therein recommended, distributed 
 to the medical officers of the Army, Navy, and :\rarine-Hospital Service, 
 to guide them in the cxaminaiions they were called upon to make under 
 orders of their several Departments. 
 
 Tliis book Avas only the second one in English on this subject; a 
 monograph from Professor Wilson, of Edinburgh, in 1852, being the 
 other, which had failed to draw ])iiblic attention to the subject as it 
 deserved, the reason undoubtedly being the lack of such a quick and 
 practical test as that of I'rofcssor Holmgren, since brought forward. 
 This perstmal explanation has been necessary to show that the subject 
 was an entirely new one to the laity, the profession, and even to the 
 
HpecialiHts who lisid not hoconio piji<;ti«all,v iUMiUiiint('<l with it. There- 
 fore I hiive been and am eaHed upon t'ol' a<l\ ice ami explanation hy 
 niedieal otiieers and others whose otlieial duties interest them, direetlv 
 or otherwise, in Hie detet-tion of eoh)r -hlimlness. Sueh adviee anil 
 explanations I have alw lys {riven freely to the beat of my ability, and 
 have allowed nosacritl(U! of time, or money to prevent imj from respond- 
 ing to ea<;h and «!very call to talk, to hieture, to explain, to answer 
 mquiry by letter, or to appear before interested authorities, as the 
 higislative railroad committees of Massachusetts and Connecticut, and 
 the Naval Committee of Congress, and tinallv before nmny seientitic 
 societies. Especially have I felt it my duty to'assist those in authoritv 
 in uniha-standing the subject before imddng rules and regulation's 
 governing visual defe(!ts and coh»r-blindness. Thus it is .that I conu! 
 before tliis l)oard at my (nvn expense, stimidated <uily with a desire 
 that, so far as I can make <'lear, they nniy be able to protect the com- 
 munity from th(^ hidden danger of defc(!tive sight, by discriminating 
 rules based upon the praeti<5al facts of scientific observation. 
 
 Th«* Sui)ervising rnsi)ector-General says, in his annual report, that 
 the rides m reference to cohu'-blindness "were the most important, 
 probably, ever adoj)ted by the board." Now, the nec<;ssity of physical 
 examination of soldiers was finally recognized by the comnmnity during 
 the war. The crystallization, so to speak, of' society in thiscountrv 
 which has since so rajudly followed, has of necessity led to the required 
 physi(!al examination of various classes in civil life, and has naturallv 
 often met with great opposition on the part of those subjected to it. 
 Sympathy is always with the defective person, as amongst us the rights 
 of the community are nearly universally sacrificed to those of the 
 individual. This is, of (jourse, a potent cause of the difficulty of pro- 
 tecting the community by laws which render physical examinations 
 necessary. ^ 
 
 The railroad committee of the legislature of Massachusetts tohl me 
 when I was arguing hvthiv. them, that I never should succeed in mak- 
 ing them " oculists." But since they, as any body of the laity, would not 
 accept or act upon I he opinion and testimony of ])rofessional experts nn- 
 chaUc>i(fe<l,l had to consume valualde time in explaining to them some of 
 the laws ot form and color-perception, A\athout a recognition of which it is 
 impossible to understand even the general bearings of this subject of 
 of defective \asion from poor eyesight or color-blindness. Your board, 
 therefore, must permit nie to draw their attention to some of the con- 
 ditions ot our sense of sight and color, which bear so directly on what 
 now concerns us. 
 
 Through the eye we receive two impressions, uamely,/o>v/i and color. 
 These are very distinct, and not at all necessarily connecited. The com- 
 plex arrangement of the internal part of the human eye, by which it 
 resembles perfectly a camera ohscura, is necessary in order that a sharplv- 
 deflned picture of external objects should be received on our retina. 
 The slightest congenital or pathological change from a normal condi- 
 tion causes imperfect vision. Now, this is not the case with reference 
 to color. The curves of the refracting media of the eye may be very 
 untnie, the media themselves not transparent, and yet the impression 
 ot color may be quite perfect. A person so Idiud Avith cataract as to 
 be only able to tell where the Avindow is, may be able, if not color-blind, 
 to disti nguish quite delicate or pale shades of color. Through a ground- 
 glass window we can reacUly see the color of a signal-light, though we 
 
 X 
 
 I 
 
5 
 
 X 
 
 n.imot, of cmir^.., «li,stinf.iiish the form of iiny object. Hence the "lej.t 
 ^i^llIe, pnictinilly, of color for njomjiIm over /J>m/ As is well known nil 
 attempts .it the intro.ln(tion of fonn for co/or in signals, on 1 e mV « 
 well as on railroaWs, hav«. been j-iven np as nsdess? 
 
 There is a natnral e.nnlition of our sense of form and color wln'cli 
 
 MUMt be nn<lerstoo(l as It may bear directly up(m the exi.lanation of 
 
 nnstakes in qnickly disc-rnin^' form or cohu' .sio,,als. It is only at the 
 
 centre <j( our retina that we have perleet form penu^ptio... Fr^m hero 
 
 Thriw;\r' ^''T' ?^ «*^'^''"«'.«'l>J»'"f« distini^tly diminishes rai.idly. 
 Ihis tact we are almost un<-onseious of, since we can so easily turn our 
 eyes towards an obj.-ct an.l let the iumj-e of it fall upon this spot of best 
 s.Kht in he centre of the retina. Ch)se one eye anil look at^ w r as 
 louf as "constitution " in siu^h print as this, and you Mill notice h J 
 really only the first three or four lett.'rs are distinct, and we m ist s 
 18 said, run our ey(; along- to catch the rest of the word. Hence, w hen 
 
 s K^noticr "* "" ''^'^''''^ "''""''^ "*""*"' ""*' "'"'■'' ^"^ '•"'' "'^'^^ '^^" ««■ 
 
 Now this same law holds true as to color. It is only at the centre of 
 the retina that we huye our best color sense. Onr feeliiiL' for the color 
 tiu es trom here outwards. Close one eye and look with the other at a 
 red water on your thumb-nail. Then, keeping the eye flxe(V move he 
 hand slowly off to one side, and it will be found that the waferi? ml 
 tmmstancte, loses Its color, and may appear even black. This fading 
 fro^n the centre of the retina outwards yaric^s with the different colorf 
 
 Another natural or normal condition of our form-sense and our color 
 sense is very important to be recognized and remembered. It is the 
 persistency oi the impression on the retina. If we gaze steadily for a 
 time, say at a pictnre in a dark frame on the wall, especially wlien we 
 c.^)en our eyes m the morning after rest and the retina is more sensi- 
 tnv, then when we close our eyes W(i still see the ])ictnre. Now if we 
 open them and look at another ]HU-tion of the wall or at the ceilin-' the 
 
 !i.M. "'«Hn ''''*^"' r* I'r^' ^'''"'^ ^^''^^•^' ''"^^ "»^ ^"^'""6, instead of being 
 (aik,AMll appear light; moreover, if the wall or ceiling we look at is 
 
 . ppear L.iger. If the wall or ceiling is nearer, then the picture will 
 appear smaller, A pilot steadily gazing at the outliiu' of a schooner in 
 a dim light Mill see another in the direction he turns his eyes 
 
 ihis IS true, al,s(., of color, and hence of importance, as is rea<lilv 
 ^-Jj": fr'l^''-'' "^ *'i*-' ^»^-isl^t-red disk, about six i.lches inVlianJ^ 
 etei, as I hold it up against the wall, whilst I count twenty. Now 
 when I remove it and you ccmtinue to h.ok at the wall Mhere it was 
 iwf .!""*• ""';"'■''*'*" '^'^^ ''OHtinue and y.m will still see it, but sud<lenly,' 
 nstl-i^l'm!^ ' yoiLseea^rnvM-ircle; the comj.lementary after-imagl > 
 as It IS called. Just tin; same as you see with this green disk— a com- 
 plementary or rose-colored spot appears in its stead. If you gaze at 
 the setting sun Avhen it is a ball of red and then turn to the east you 
 will see a rising fprn, one. A man who has gazed steadily at a "red 
 i>rt/-^ light will, on turning away, see suddenly a green starhoan) li oUt I 
 mention these curious phenomena oi nontml vision as they must^notbe 
 orgotten in investigating mistakes or accidents, and have a direct 
 bearing m all attempted tests of the coh.r sense with lanterns 
 
 Scientists at present generally admit but three base «u- j.rimary cohu's, 
 namely: m/, (jfrn-^, and viokt. Now, with the central i.ortion of our 
 retina we can perceive all three of those colors. In a zone outside of 
 
 i 
 
this, red fails us; iiixl iiyniii, inn /-oiicoutsidi'of this, both r«-(l and ^'roon 
 tail us, and wv can percciv^^ nul.v l>lu«'or violet. Color l»lin<lness is the 
 failure of one ur more of these three sensations, vi/: led, j>reen, and 
 violet. T'leni is n'd Itlindness, yieen-idindness, and violet blindness. 
 The. first two praetieally involve eaeli other. Violet includes blindness 
 to yellow. It is very iiue indeed. When, thcretbi'c, we use the term 
 color-blind, it means red or ;;reen-blindness; one iuvolvinj;' the other. 
 NO much so that the two are sonu^times «*onsidered the same, and called 
 red-oreen blindness. This must be remendiered, sin<-(i a {ktsou rt^ported 
 red blind is su|»posed to be aitle to see yreen as the normal-eyed, which 
 is not the ease. A (M)lor-l)lind do«'snot seertMl as «reen or ;ireen as red, 
 but both app«'ar (jraii'iHli to him. In proportion as he is color blind, all 
 colors «',ontaininy' n-d and ;;reen appear as if so much j;ray or white and 
 black ndx(Ml had been use<l instea<l of th«! pi«iu«'nts. Hence a white 
 lantern when smoky will ^ive him tins sensation of a };recn or a \•^'i\ 
 one. lie has learned instinctively tojudj;'e of the color of li<;ht by its 
 intensity. Very naturally, thereVoie," if he calls th(>m by the color 
 name we do, he is supposed to see them as we do. This l' will return 
 to hereaft<'r. 
 
 The(hin<ier from <'(>h)r-blindness is, of coni'se, in propiu'tion to tin* 
 amount. Xow, examinations of males and females of all races, cohus, 
 cimntries, aj>e.s, and (h'},'ree8 of civilization or education, ha\ c proved 
 that about four \wv cent, of the former and one-fourth of one per cent, 
 of the latti'r are more or h'ss (,'olor-blind. The result of my own testing' 
 18,550 males was tindin;,' 7G4 more or less (tolor-blind, or' about 4 per 
 cent.; and of 14,r)r>7 femah^s, only 11 defective. I wouhl say at once that 
 this must be rej^anhMl only as a sexual ditlerence, and Jia's nothinji" to 
 do with women's greater familiarity with colored obje<5ts. One ^ireat 
 reason why this has not been known till now is, that we have not had 
 the means of testing lary-e numbers of people rapidly and with accuracy. 
 But you will at once ask, how is it that the color-blind have escaped 
 detection, and do so now in every-day life? I should take up too much 
 of y<mr time to exi»lain this in detail, and would refer you to chapter 
 eleven, of my Manual. It is of itself one of the most inti'restiny' jtoints 
 of this curious defect. How even a i»ortrait or landscap*' ]»ainter may 
 escape <letection, exc<'pt by accident, is well worth seriously consider- 
 iiifi' in rehition to the necessity of exiterts in testiu};' pilots or railroad 
 emph»yes. 
 
 Coh)r-blindness is congenital, and it does not chan{>e as one rtows 
 up, nor can it be altered by any practice with <'olors. It may be total, 
 that is, a person may have no sensation whatever of color, and the 
 whole wouhl be to them but shades of yray. It is onlv ])artially pal- 
 liated, but not altered in artificial lij;iit. Tlie color-blind do not 'make 
 such jiToss mistakes by j>as-liyiit or when looking- through a i)ale lemon- 
 colored {>hiss like pas-light. It is a mistake to sui)i)ose that there- 
 fore they may see colored sif>nids better by night. This is tmrnmitted 
 light, taking only the eoh)r of the glass, but little modified bv the s()urce 
 of illumination. It is oidy retle(!ted light from colored objects which i.s 
 changed so as to assist them. It was su])i>os«'d that their vision was 
 changed or altered by looking through a solution of fuchine, as in this 
 Avedge-shaped little tank. This is a mistake. The relati«ms of light 
 and shade are changed, and these being what the color-blind d(?cide bv 
 in namhuf colors, they, and others, concluded the color sense was really 
 altered. This is referred to be(!ause it has passed from jouiiial to news- • 
 paper that color-blindness was thus curable. 
 
 i 
 
i 
 
 Color-MiiKliicsH is very In'mlitiuy; of iiiipoitaiH'*', \s\wro n mod ftil. 
 lows Hie paicnts' or KniiKlpnrciits' profcNsioii. It follows, as jases in 
 taiiiiltcs sliow, tlie jjeiicral law of lieredih , "inire the, liin|» ratio in a 
 t'oMiMMinitycontainin-;inanycolor-l>lin<ltain::.eH. A practieal |)oint here 
 IS, (hat alter aiw^ident from collision or otherwise, anil those implicated 
 lire killed or drowned, w<^ may, perhaps, jnd«:e whether it was due to 
 eoh)r-l>lindness l»y (indiiij; whether (hey helonyed to ccdorldind tiuni- 
 dies, and luid Itiiiod relatives whoarti detective. 
 
 (Joh)r-l>lindness may exist (ionj-enitally in one eye. Persims who can 
 Ix' put into (he so-odled hypnotic coniiition niav l»e (emporarilv ren- 
 dered color-l.lmd therelty. Moreover, the colorblind who can he thrown 
 into this conddioii may he maiht to see colors whilst hvpiiotized. 
 
 Color-hiindiiess, besides hciiiK- <'<>n-;eni(al and hei('di(ary, may ho 
 
 ac(piired. It is u symptom oC soi liseases of (he hiain anil (he op(ic 
 
 nerve. Men, after any exhausting diseasj^ like typhoid fever, should 
 be tested beh>rea;-a in assniniiiK their duties. The necessity of periodic 
 examinations, lor instance widi pilo(s as often as they are relicensed 
 i.s thus readily understood. This, (piite asi(h^ from "the necessity of 
 testin^i' their visual |)ower, which may have decreased from manycaiiHes 
 <liirin;; the precedin;-' year. 
 
 Professor Niiel, of Loiivain, Hel;>iiiin, sent iin" the followi'ij«- account 
 ot a -.-i'so under his care, which was reiiorted to the Koviu iMe<licul 
 Academy: 
 
 ".r<»sei.li Dhnr, of Tiirinne h' (Irosse, ait l-'O, laborer on the Grand 
 Ceiidal lioad, consiiKed me January 12, 1878. I found that he had 
 been in the Hospital St. INerre, at LcMivain, a vear befor*', with troiil)le 
 m the backof the rijiht eye, (»//<• /<f'r/v> irtrohiilhnitr.) From (his he re- 
 coveivd to having' vision tw<»-thirds of the normal. Af(er a mondi at the 
 Jiosjatal, he returned to his work and continued at it a vear without his 
 condition lieiiij^ noticed. Dminj.^ this year, however, I)hiir had to act 
 one day as a j-iiard. In the «'veniii<' he put out a (inrii instead of u 
 rcti lantern, and retiiriu'd into the yiiard-lioiise. ilaviii};' tor some 
 reason to «(> out a few mimites later, he passed near the lantern, when 
 suddenly he was in doubt as to the color of the signal. Lookiiifi' at it 
 im.re closely with his h'ft eye, (which was then healthv,) ami comparing 
 t he (wodit!ereiit faces of the si«;ual, he found that he had in reality 
 sliown the (jirn, instead of the ml lioht. These facts he even now 
 reca Is very well, and distim^tly remembers how he could not distin- 
 guish between the re.l, green, ami white lights with the right eve, and 
 couhl only tell them by looking close-to with his left. Tli(> ('iirum- 
 stance so alfected him that he consulted a phvsician, who dismissed 
 Jiim with the remark that he had probably been drinking. 
 
 "On examination, I found the visual aciiteness of tlu' hdt eve normal 
 ot the right six-ninths of normal. Visual tiehl of left eye tor white 
 iiorinal; ol right eyeonly 30(h'grees up, down, and inwards; outwards,' 
 40 degrees. The color sense is greatly altered in the right eye. RM 
 and green are confounded Avith gray; violet aj)i.ear blue; tlu' i>atient 
 conhl only distinctly distinguish yellow and bine. In the left eye the 
 cohir sense for red and green was diminished; the object had' to be 
 larger than what the iKu-mal eye could recognizi'. 
 
 "Here, then, we have an ei'n])loye with defective color sense, from a 
 dis«'aseot the nervous centres, continuing hisoccni)ation for a year; but 
 the farst time he ha<l to giye the signal, disi)laying fpren for ]rd. The 
 danger can be readily a]»ineciated. Had he been all engineer an aeci- 
 
8 
 
 dent would certainly have resulted. I would especially recall the tact 
 tnat Ins right eye, so defective in color sense, had a visual power of 
 six-ninths of the normal, Avhich would have allowed him to have con- 
 tmued m service. And still furtlier, that the color sense had also fallen 
 m the left eye, where there was still nornal visual power. The pa- 
 tient s doubts and my prtiliminary examination were convincing. Later 
 the left eye also confouuded red and green, yet its visual acuteness 
 renmmed normal or nearly so. 
 
 "CUnical observations have sufficiently demonstrated the not infre- 
 quent occurrence of acquired color-blindness. If, now, its frequency has 
 already attracted attention, it should be still further rememb»'red as 
 being so much more dangerous than when congenital. In acquired 
 color-blindness the person may for many days be quite unaware of hi» 
 altered color-sense, and would only recognize it after repeated mistakes, 
 any one of which under favorable circumstances may prove fatal 
 
 /Whenever the surgeon suspects acquired color-blindness, the first 
 thing requisite is the examination of the visual field for colors. In 
 these cases we can also question a,' to color names, since the individual 
 has knoAvn them, as we may prove by the color sense of his other eye 
 If perfect, or his having still some color sense remaining. Most cer- 
 ..amly the first requisite in the control of color-blindness in certain 
 public services, as of the anomalies of refraction in the army, is to insist 
 on the examiner haviiig a good kuoA\ ledge of ophthalmology." 
 
 Injuries about the head, such as sailors and railroad employes are 
 particularly subject to, may cause diminished color perception Ob- 
 served cases might be cited in support of this statement. 
 
 Alcohol and tobac(!o, each alone or when combined, produce, in poi- 
 sonous doses, a deterioriation of the vision and color sense, as has been 
 long known by specialists. This question has been very carefully 
 studied and reported on by ophthalmic surgeons in Europe, England 
 and this country quit(; recently. The results are the same, namely 
 tnat alcohol ami tobacco together, or each alone, do cause failure of 
 eyesight, botli as to form and color. And, what is most important to 
 be remembered, the color-blindness may exist when the person seea 
 otherwise quite well. Hence such a person would escape detection. 
 One of the writers on this topic, ?rofes,S(n' Xuel, above quoted, very tmily 
 remarus: "The ordinary methods of examination Avould not detect such 
 a color defect, especially at its outset; perimetric examinations are 
 indispensal)le." 
 
 These additional and peculiar tests, re(]iiisite after sickness and in- 
 juries, are therefore also necessary where there is anv sus]»icion of alco- 
 hol or tobacco, parth'ularly as it is the central portion of the flehl 'vliich 
 IS affected, just where we have our lies< dsion. J?"ow the i)oint is, that 
 such tj';;ts can only be a])})licd by .skilled surgeons. The danger from 
 partial or total color-blindness from these causes is the greater since 
 they are sure to be overl'wked by non-ex])erts, especiiillv as the visual 
 power for form may be so good as not to call tlie person's attention ta 
 his own trouble, and cause him even to escape detection when exam- 
 ine<l by the laity. Hem-e, therefore, tlie absolut*; necessity for periodic 
 examniations of tlio.se known to use alcohol or tol)acco very freely. 
 And snn.lar j)eriodic examinations by skilled experts are equally re(|ui- 
 site f(U' all injured «n- contu.sed, and tho.se conAalcscent from exhausting 
 di.sea.ses, before they return to their positions. 
 
 It will now at once be asked of me, if one out of e\ery twenty-five 
 
ot our male friends is likely to be color-blind, how is it that this defect 
 has escaped detection ? A railway official said to me, "I have been 
 coniu'cted with railroa dill}.' forty years, and never heai'd of color-blind- 
 ness; It It exists I must have known about it." So, also, the head- 
 centre of the Brotherhood of Locomotive Engineers never had heard 
 ot color-blindness. For a full answer and explanation I must refer to- 
 tJic; «l>ecud cluipter in my Manual on "Concealment of eolor-blindnes* 
 in practical hfe." I there show how the color-blind <leceive themselves 
 and others, jind, growing up in ignorance of th(;ir detect, escape detec- 
 tion. To this nirst be added the very important tiict that, till very 
 recently, methods of testing for color-blindness have been used which 
 were wholly inadequate to exj)ose particularly the lighter forms of the 
 cha\t '• ^"""^^ ^^*'' 1**^"'"**^'^^**^ <l^^ote the folloAving from that 
 
 "The color-bUnd who are quick-witted enough to discover early that 
 something is wrong with their vision by the smiles of their listener* 
 when they mention this or that object by color, are equallv qnick- 
 witted m avoiding so doing. They have found tnat there are names 
 ot certain attributes they cannot comprehend, and hence must let alone. 
 Ihey learn, also, what we forget, that so many objects of every-dav 
 lite always have the same cjolor, as red tiles or bricks, and the color 
 names of these they use Avith freedom, whilst they often, even un- 
 consciously, are cautious not to ncme the coh)r of a new object till thev 
 have heard It applied, after which it is a mere matter " of memorv, 
 stimulated by a consciousness of defect. I have often recalled to the 
 coIor-bJmd their own acts and wor«ls, and surprised them by an exposure 
 ot the mental jugglery they employed to escape detection, of which 
 thej^ were almost unaware, so much had it become a matter of habit 
 Another important point is, that as violet-blindness is very rare the 
 vast uia](>rity of defective are red or green-blind. These persons see 
 violet and yellow as the itormal-eyed, and thev naturallv a]»plv these 
 color names correctlv. Wiieu, theretbre, thev fail in red or green, a 
 casual observer attiiuutes it to sinqde carelessness: Jience a verv readv 
 avoidance of detection. It does not seem possible that any one wh» 
 sees so much correctly, a.id whos(i ideas of color so correspond with 
 our own, cannot be equally corre(!t tlironghout, if thev Avill but take 
 the pains to notice aiu' learn. Color-blindness is also a"s(mrce of pettv 
 mortihcation, which teaches its possessor to be on constant guard over 
 himst'lf in ayoKhng exposure and its accoi.ipanying irritation. Ilie 
 inteUigent eol()r-blind finds many ways of drawing a <lecision of color 
 from those he is in contact Avith, and nlways lets shop-keepers pick out 
 the (iolors he calls lor, just as the color-blind shoi)-keei.er lets his eus- 
 tomer do the same, if lie can; and when he fails in this, aial makes 
 mistidces .Miou^li fo k)S(^ his phice, he can take refuge in the mourniiijr 
 stores, wliere liis (h'fect is an advantage." 
 
 Prjjf. FTolingren well says: "To judg.> correctly of eolor-blindness 
 and the various itractical (luesfions coiiiK'cted with it, it is of the high- 
 est importance to distinctly observe the ditteroiice betAveen Ihc manner 
 in^which the color-))!ii,(l person sees, and the manner in which he iionien 
 comrs. I he sensation is based upon tlie nature of tlu' sense of color 
 in the .uganiz;ition of the optic nerve from birth. The name, on the 
 contrary IS learned, ft is convenfional; it dej)ends upon exercise and 
 hahit. llM' iiitmes of cohms are natundlv the objective e\i»ression of 
 .subjective sensations; bui, on the otiier hand, tliev are regulated l>y 
 
10 
 
 the system of the normal siftlit, and cannot, conse(iuentIv, agree with 
 that ol the cohjr-bhnd. They can, nevertheless, be learnea by the lat- 
 ter and even applied correctly in many cases. There is connected 
 with this lact ii peculiarity of utmost importance, practically, to the 
 question i/i point, and one which has given rise to the most serious 
 embarrassments and misunderstandings. This has been, and is still 
 one of the chief causes of our erroneous ideas on the subject of color- 
 bhndness existing in the masses, because it is the veil under which this 
 delect usually conceals itself from our observation in every-day life, 
 and un<ler which, even to the last moment, it will succeed in escaping 
 discovery m cases where, as frecpiently happens, the methods of ex- 
 ploration employed are indecisive or are based uiioii erroneous princi- 
 ples. * 
 
 " If we reflect on the condition of the color-blind, it is difflcult to under- 
 stand how lie can avoid being detected in his daily intercourse Avith 
 those endowed witli normal sight, and yet experience has sufficientlv 
 controverted this idea. That Avhich we have acquired in examining 
 en mmse the personnel of a railway, for example, AAhere it is required 
 night and day to give attention to colored signals, is singularly worthy 
 ■of notice. We learn by it that a number of coior-blind were discovered, 
 although their defective sense of color had never been suspected l)y 
 themselves or any one else, and the majority liad correctlv nerformed 
 their duties." " "^ 
 
 I have said that "no one can have tested and talked with manv 
 color-bhnd without being (jonvinced that we can hardly set any limit 
 to their capacity for learning other attributes of colored objects, and 
 recognizing and remembering their color names through tliese alone. 
 Thus, as we now well know, they may even deceive themselves, as 
 well as others, into the belief that they have gained bv practice a color 
 perception they were not born with." 
 
 The color-blind have even succeeded as landsca])*! and portrait paint- 
 ers^ as they have seemingly succeeded as pilots and railroad engineers. 
 n the painter's colors are not marked or chosen lor hiiu detection mav 
 result, as shown by the following case: " A student of the Koyal Acad- 
 emy of London, who was selected, not only by the authorities" but also 
 by his fellow-students, as having about the best perception for form and 
 power of light and shade, turned to the use of colors. In this it was 
 naturally supposed he would exhibit extraordinarv talent, and become 
 a great painter. He was allowed to take a portrait bv Titian from the 
 JNational Gallery and have it in a snudl room to hiinself. There lie 
 copied it to his best ability, as he stated to the principal and to his 
 brother students. No one lia<l seen him at work. His result w^as the 
 most perfect (;opy, as far as light and shade went, but in pea-green. He 
 finally became an engraver." 
 
 Color names the color-blind learn in various ways to use as we do, 
 and this has heretofore greatly assisted them in escaping detec^tiou. 
 And in this way they even now escape, since, in spite of the warnings 
 jears ago of Gcethe and Helmholtz, that asking them the names -of 
 colors would simply drive both parties crazv, there are many whose 
 official duty slumld teach them better, who still cannot get rid of the 
 idea that they can find out how another jiersons sees colors by simply 
 asking them the color-names of objects. Every one who has tlie slight- 
 est knowledge of this subject and any experience at all, now admits 
 that attempting to test the color sense by asking the names of colors. 
 
 4- 
 
 I 
 
 -: 
 
 i 
 
u 
 
 eyed can he 
 
 to be iiorinal- 
 
 d light and 
 
 A 
 
 
 is 8iiii])ly ridiculous. By such exanuiuition the uoi 
 shown to be color-blind as readily as the color-blind \m 
 eyed. This is equally true of colored objects by d 
 colored ol)je(;ts by transmitted hght, viz., lanterns, &. 
 
 NoAV, the oidy way Ave can compare mental notes witl .mother j)erson 
 is by what he says or what he does; that is, bv the tongue or by his 
 expression through nuiscular action. It being certain that Ave (;anjiot 
 find out how a color im])r<'sses anotlnu- person's brain by what his 
 tongue t(?lls us, we ?iiust api)eal to the nniscular sense, we must cause 
 hnn to do something Avith his lumd, for instance, which Avill prove that 
 the impression of tLe color on his brani is the same as ours or not. 
 Therefiu-e it is tluvt any proper test nuist depend on this principle of 
 comparison. x x ./ 
 
 Comparison tests are numerous, but vary greatly in their sim])licity 
 or i)racticability. For the purposes of the medical ofticcns of the Depart- 
 ment tins board is concerned Avith the test which must l)e absolutely sure, 
 rapid of a] (plication, and thi? apparatus inexpensive. For a description 
 of all the A-arious tests for color-blindness, I nuist refer to my Manual. 
 I wdl hero only exhibit and explain to the board some of the principal 
 ones, nicluding those adopted as standards by the rides of the State 
 Board of Health of Connecticut. 
 
 Woinow^-i disk has a centre of one-half each black and white, and out- 
 side these are concentric circles, each of Avhich is composed of equal 
 parts of two of tlie three primary colors— red, green, and violet. While 
 It revolves rapidly the centre is gray, and the concentric rings have 
 definite colors to our eyes, while to the person who is blind to the color 
 not represented in the ring, this ring may appear like the cenire, 
 namely, grayish. 
 
 Simultaneous contrast tents may be varied. I Avill shoAV but a fcAV. 
 I have bent a piece of white (;ard-board to a right angle and fastene(i 
 to the adjacent surtacies a little square of black cloth. Now, holding a 
 piece ot colored glass Avith one edge u-sting in the angle of the paper, 
 about dividing the right angle made by tlie card-board, and looking 
 doAvn from aboA-e, we shall see the retleiition of the A^ertically placed 
 bhick sijuars of the color «f the glass, but tha horizontallv placed one 
 AviU appear to us of the complementary color of the glass. Now this 
 Ithenoinenon does not occur to the color-'olind. 
 
 Still imfs cards, here before you, are letters, numbers, or figures printed 
 in scpiares on a ground of squares, the colors of the letters, &c., and 
 the ground-work being those whi<!h the color-blind confuse. Hence 
 they cannot see to read the lett(u\s or discern the figures. 
 
 P//»V/t'r'.v test is, as you see, also one of simultaneous contrast. On 
 <;olored pages letters and nuird)ers are printed in black and gray. When 
 the page is covered Avith tissue paper the color-blind cannot 'see these 
 letters or figures Avhen the normal-eye<l can. This pamphlet, thus 
 arranged, is a ])ractical test used on the Swiss railroads bv Professor 
 rfliiger, of Berne. 
 
 Holmgren's comi>aiison test with the Avorsteds the board all know of. 
 As is seen, the selection of coh)rs, tiie numbers of each, &c., are not 
 arbitrary, but must be carefully chosen. I have arranged Avith a dealer 
 in Avorsteds to always supply standard sets, as he does < ^ some of the 
 Dei>artments of tlie Government. The choice of the green, purple, and 
 red test Avorsteds is of importance, and examiners liaA^e been no little 
 annoyed and perplexed by not having the right ones to work with. 
 
12 
 
 Dr. Jeffries then described the ^vorsted test, referriiiL' to ]iis Maii- 
 iiiil for i.iore detaHed exjdanatiou. Its m'wi^r/ siiiiplicitv was dwelt 
 on, aiul the conseqnent (hmger of any one not most tliorouVldv posted 
 both ui tlieorv and practice, making most fatal mistakes, finding color- 
 blindness where it did not really exist, and not detecting it where present 
 Ihe test was most perfect, but never could be understood too Avell He 
 aiKl'others^*'"' ridi<-ulously it had been misused by railroad omdals 
 
 Daae's test is copied from Hol.agren's. On a card in book form are 
 arranged rows of little scpiares of worked worsteds. Some rows are 
 correct, namely, arranged from the darker to lighter of the same color. 
 Others are arranged of the colors the color-blind especially confound, 
 and they will say when asked that these rows are correct. It is arrauced 
 to detect red, green, and violet-blindness. ^ 
 
 Bonders' worsted test consists, as you see, of a series of little pieces 
 of wood, on which are wound colored worsteds. By testing a lartre 
 number of color-Mind, he found Just what colors they confounded, and 
 he Nvmds one of them on the stock, letting the other color come in as a 
 single^ thread once or twice in the row. Now, these two colors looking 
 alike to the color-blind, they cannot see any difference, and cannot say 
 that there are any or how many bands of a different color or appear- 
 ance from the rest of the stock. The sticks, as I show, are arranged 
 to detect the three forms of color-blindness— red, green, and violet-blind- 
 
 The quantitative measure of color-blindness is very important The 
 defect exists in all degrees; and, as a certain amount may not prevent 
 persons acting m some capacities, tlie exact determination of the exist- 
 ing- chroniatic loss becomes very necessary. For this piu-pose various 
 methods have been devised, based upon the several i)nnciples of color- 
 perception which have been described or alluded to. These are in the 
 Lonnecticut rules. 
 
 Holmgren's method, with colored shadows, I regret not being able to 
 exhibit to you, as the apparatus is too cumbersome to be easily trans- 
 ported. It is described in my United States Manual. In the centre is 
 a round-mcked petroleum lamp; from the stand project two horizontal 
 «w?i *"'' T./' ^^^f l^'^^'l 8H^«« before the light, the pencil to cast a 
 shadow, and the white porcelame on which it is cast; on the other arm 
 IS the mirror, by refiection from which another shadow is cast on the 
 porcelame; the mirror is movable towards and from the lamp At a 
 certain distance the shadows will appear of the same brightness to the 
 normal eye, and we measure the amount of color-blindness by the differ- 
 ence in distance of lamp and mirror re(iuisite to cause the two shadows 
 to seem eqiially bright. This is one of the ''control methods" used bv 
 Professor Holmgren on the Swedish railroads. 
 
 Bonders' method of quantitatively determining the color percention hu 
 reflected hght, is by placing these colored disks, from one to twentv 
 millimetres in diameter, on a surface of black velvet hung on the wall 
 On approaching slowly a small colored object, the normal eye detects 
 the color but little later thn.n he sees the light. The person who has 
 any loss of the chromatic sense, that is in any tlegree color-blind, sees ' 
 the color much later than he sees the reflected light. On this is based 
 the method of examination. Bright saturated colors, one millimetre in 
 diameter, when placed on black velvet in a good light, will be seen bv 
 an eye with normal visual acuteness at a distance of five metres 
 
 4t^' 
 
13 
 
 ^ Professor Bonders says: "It is interesting to observe how the exam- 
 ined gradnallj' passes from doubt to certainty. We show him a single 
 disk at live metres distance; he sees the little disk, but not its colorf a 
 step nearer, and he ventures to call it 'red;' another step, and he doubt- 
 fully says, ' no, green.' Finally he says ' red ' again, and at last decides 
 more positively for this color. Just when he became certain is readily 
 determined. Or, we put a number of the disks of varying diametei^ 
 together on the large piece of velvet, and pointing to each with a stick, 
 ask its color quickly. With i)artial color sense, it readily appears how 
 in approaching, first the larger disks and then the smaller are rightly 
 named; whilst, with less color-perception, only the larger are told close- 
 to; and when there is complete absence, the color of even these is not 
 recognized. We may thus determine the numerical degree of mlor- 
 bimdnesH with sufficient accuracy." 
 
 ponders' method ofqiiantitatirely determining color perception by trans- 
 mitted hght, IS by the apparatus before you, used on the railroads in 
 Holland. The hght is from a candle, siich as is emploved to determine 
 the candle-power of gas. This is placed behind a blackened wooden 
 screen, in which is an opening, twenty-live millimetres in diameter 
 cohered Avith ground glass; in front of this hole a rotating metal disk is 
 arranged, pierced Avith holes, 1, 2, 5, 15. and L»() millimetres in diameter; 
 just behind tlie opening in the screen is a rotating disk, with holes- 
 one clear, the others containing red and green signal-lantern glass, as 
 also other colors— which we can, by turning, bring in front of the hole 
 in the screen; the candle is arranged to slide along a scale, thereby 
 giving us its distance from the screen; the room is partly darkened 
 and otherwise the examination is conducted in the same way as in 
 the reflected light. From the distance at which the candle is from the 
 screen, the size of the hole necessary in the screen, and the distance of 
 the person examined from the screen, we may calculate just what his 
 degree of chromatic sense or color-blindness is. For the formula for 
 this and further description, I would refer to my Manual. 
 
 Now as I turn the disk to change the color of the light and vary the 
 size of the opening in the screen, the members of the board see how 
 perfectly we imitate the conditions of seeing the colored signals on the 
 railroads as well as the port and starboard lights. A spot of colored 
 light IS presented to the eye just as a red or green light appears to the 
 pilot's ej'e on the water. As soon as seen bv the normal eye the color 
 18 instantly recognized. Not so with the pilot Avhose color sense is in 
 any degree less than the normal eye. If partially defective, he mav 
 finally hit on the color when he has approached it, perhaps too near to 
 avoid a collision. If more defective, h(^, will decide instantly icronqly, 
 and cause an accident; aid how many have thus occurred, and liow 
 many will occur before defective sight for form and color absolutely 
 prevents a pilot being licensed or reliccnsed ? 
 
 As color-blind engineers escape accident by fortunate guessing and 
 assistance from familiarity with the surroundings, &c., so the color- 
 blind pilot has escaped by his tamiliarity with the surroundings. The 
 direction of the wind tells him which way the sailing-vessel ought to be 
 moving, and therefore which light ought to l)e tewards him. The 
 position of the steamer on the river, therecognit o, of direction by the 
 dimly-seen outline, a knowledge of a certain vessel or steamer likely 
 to be met with just at this point, and many extraneous circumstances 
 help the color-blind to rightly guess which light il is he sees. But how 
 
14 
 
 often are all those extraneous conditions absent for the pilot <»r th e 
 railroad engineer, when, from the coh)r of light alone, iiistantoiiroiis 
 recognition of port or starboard danger or safety must be made to 
 save (iolhsion, and whiijli iveognition is so certaiir for the normal eve 
 that the lack of it cau harilly be believed? 
 
 Now, this ai)paratus of Professor Uonders, in i)ractical use in Holland, 
 and directed by tiie Connecticut rules, enables us to exactly imitate 
 the condition of seeing colored signals when t\wvo, are no extrnneom 
 circumstumex to help the decmon of the 2>ilot or eiiffineer. If the- o is 
 any value in the use of colored signals, then certainly there is danger 
 m aUowmg those who (iannot distinguish the?n by ffieir color to steer 
 our vessels or run our locomotives. The testing color-blind pilots or 
 railroad employes who have been long in service, and fortunatelv for 
 us escaped any very serious collisions, &e., is a very interesting psv<'o- 
 logical study. As thvy cannot see their mistakes, they «!annot believe 
 m them. The red or green-blind s(^e blue and yellow as we do : therefore 
 by showing them two bright worsteds of these colors together, and telling 
 them that in their examination they made as marked mistakes as to class 
 these yellow and blue a^ the mme, gives them, if they will believe us 
 some little com-eption of the gravity of their defecjt. But seeiii"- is 
 said to be believing, and as they cannot see as wo do, they are 'iiot 
 likeiy to believe as we do, since such belief means loss of occupation 
 
 Hence, we see at this time the great value of Don'ders' apparatus. 
 By it the medical examiner can perfectly prove to the interested laity, 
 or inspectors, the pilot's employers or friends, just how he is defective 
 IN'othing is more convincing than the witnessing such an examination' 
 properly (ioncUn^ted. The most skeptical have always admitte*! the 
 danger, which they could not before appre(;iate, and whicjh satisfied 
 them so thoroughly that they never asked for further tests with signal- 
 lanterns, &c. But a misuse of this test, as, in fact, of any, may equallv 
 perplex the medical examiner, reiuh;r him doubtful of his diagnosis 
 cause in the laity suspicion of the Avhole question of the existence of 
 defect or danger from it, and confirm the examined in his belief that he 
 does see colors as the normal-eyed. All tests, therefore, must, in justice 
 to the examined, be appHed only by those thoroughly competent,' whose 
 education enables them to learn them and perfecrly understand them 
 when described by the expert. 
 
 I would call the attention of the board to an addition I have made 
 to Bonders' apparatus, by which, as you see, I can interpose a neutral- 
 colored (London smoke, so-called, used for spectacles) glass, which will 
 simply darken the colored light or the Avhite light. Now it will be re- 
 membered that red or green colors make a liglit darker to a color-blind in 
 proportion to the amount of his defect and the de]>th of the pigment. 
 Hence, when lu^ sees a white light bticorae darker bv inter])osing a 
 smoke-glass, he immediately concludes that it is (!olored, and sayslwZ 
 or (freen, ac(!ording to circumstances. So darkening a pale-greeii glass 
 will make it seem the same as red to him, and rendering a red one 
 brighter will make it appear greciii to him. I do not know any Avay 
 oflScials can be made to api)reciate the peculiar danger of the defect 
 l)etter than by this arrangement, which so iierfeetly exposes the color- 
 blind's exact condition of vision and shows how dangerous it is. When 
 we remember that a slightly-smoky lantern, a little rain or fog or 
 sleet, a dirty glass, or blurred eyesight from fatigue, ex])osure, or stim- 
 ulants, cause the <!olor-bhnd to mistake the signals, by changing their 
 
 i 
 
-f 
 
 16 
 
 usual condition and relative bn't/htiu-SH, by which (done thci/ decitle, then 
 we can realize that, however well they may apparently yiii'ss at colored 
 sij-nal-li«ht,s close-to, they are most <lanf;erous on the look-out, or in 
 coianuHul, or at tlu^ wheel. This use of Lon(h)u smoked glass to test 
 the color-blind must, of courst*, be thonmghly understood, and the 
 pnnciple ot its application. When thus understandinj-ly em])loyed it 
 18 a j.aeat help to the expert in proviiiy the defect to the interested 
 laity. 
 
 But now to reply to a member of the board, who says: "You have 
 shown us all these dirterent tests by various experts, <'ach one of whom 
 probably thiidis his is the best; how are we to decide as to their rela- 
 tive merits?" &v. Tlie several ways of examiniii}.' which have been 
 exhibited are all control testH, to fortity the result obtained by the first 
 and simplest method, namely, Holmgren's worsteds. ThereisiKKiuestion 
 ot one IxHug bt'tter than the other. Except for determining the umount 
 ol color-blindness, they are not needed. Wherever thev show color- 
 blindness, the Holmgren test will do it in infinitely less time. The sev- 
 eral Government Departments do not require them, as they have not 
 yet decided on the standard amount of color perception requisite. This, 
 renders it all the more necessary that the examiner should be verv 
 familiar with the worsted-test and have thoroughlv mastered it, Avhich 
 eviiu Prof. Holmgren says cannot be dime without patient, intelligent 
 study aiid practi<!al experience. It has been greatly to the credit of 
 the me<li(!al officers of the Marine-Hospital Service, and proof of the 
 value of the method, that they have succeeded so well Avith it. This 
 IS shown in the annual report of the Supervising Surgeon-General. 
 Inabihty on the part of the laity to I'oiujeive it possible that sucli a 
 seemingly common-iJace test as the Avorsteds reallv at once pointed (mt 
 the dangerous julot or engineer, and the necessity of deci'ding the 
 amount ot coh)r-blindness, have called for these additional <piantitative 
 ami control tests. But the examiner must understand them thoroughlv 
 and be competent to explain them in exhibiting the defect of the color- 
 blind he IS testing by them. 
 
 V'mml KcutencsH, or the poAver of form perception, is tested bv the 
 same means all over the world, namely, the ability to read letters or 
 distinguish tonus of certain sizes at certain distances under the same 
 circumstances of illumination. Normal visual power has been decided 
 by the average of hundreds of thousands of iKU-nial eyes. It is to be 
 able to read tiiese test-letters at tAventy feet; of course the eye, if neces- 
 sary, to be fitted Avith the glasses it may need from being near-sighted 
 over-sighte<l, or astigmatic, &c. The standard of normal vision is un- 
 doubtedly rather too low than too high. In the Navv and Armv a 
 (lefanite standanl is reciuired in recruits. No definite one is <udered for 
 pilots, as certainly ought to De. The ex})mination of the eves and the 
 testuig the vision is, by the Treasury orders, left to the medical officer 
 as he alone can, Avhen the vision is defectiAe, examine the interior of 
 tin; eye and determine the cause of such defect, and whether, as with 
 cataract, cVc, it is ])rogrcssive. So, also, he alone can sav Avhether there 
 IS granulai- lids, the results <.f specific or other disease,' liable to cause 
 tuture trouble, and so on. It is only he, and he only Avheii he under- 
 stands, AA'ho can (h'tect the cause of failing vision for distance, which 
 comes with increasing years, and can only be vem.''died with glasses. 
 lliis cans*' IS the very (MMiimon defect known as over-sight«'<lness, the 
 eyel tail being Just the reverse from near-sightedness, too short. This de- 
 
16 
 
 feet is most (lece]»tive to the laity, as the ophtlialmic surs.eon has <hiilv 
 proof of in his work of reinedyiiiK' it by ylass,'s. It is, no <loul>t, a i.oten't 
 and latent canse ot railroad aecid<Mits. 
 
 I Inive thus brieHy alluded to visunl aeuteiu'ss and nonml rwon to 
 show the necessity ot a standard l.eiiiff decided on to govern the medi- 
 cal officers m their examinations, which can be carried out by them 
 alone by i>ro[>er tests and ophthalmic- instruments. There seems to be 
 no desire on the part of the I)e])artment, as has been the case with 
 reterence to the railroads, to take these examinations (mt of the hands 
 ot medical men. Some standard to govern all medi.'al otticcrs' rulinos 
 IS called for in justice to both them and the examined. Very likcTv 
 such standard has been left undetermined in view of an interiiational 
 one being- adopted which the Department could be governed by 
 
 I have .-^hown how color-blindness can be detected and the proof of 
 Its danger made apparent to all, and explained why the tests for it 
 cannot be carried out in justi<!e to the examined or to the community 
 by those not thoroughly competent, as medical men only are. 1 will 
 now turn directly to the explanation of why the two following orders 
 are not tair to the examined and the community: 
 
 CIRCULAR. 
 
 Modification of Depar 
 
 1880. 
 Department No. 19. 
 
 Unent Circular No. 14, relating to ExaminaHon of 
 Pilots for Color-Blindness. 
 
 _^ ? Treasury Department, 
 
 steamboat fnspection. ) Washington, D. C, March 9, 1880. 
 
 To the Supervising and Local Inspectors of Steam- Vessels: 
 
 In view of the expense and hardship likely to accrue to pilots living 
 at points remote from stations of the Revenue Marine-Hospital Service 
 in visiting such stations for the purpose of being examined as to color- 
 blindness, as required by the amendment to Rule 47, Rules and Regu- 
 lations of the Board of Supervising Inspe(!tors, Department circular 
 No. 14, dated February 17, 1880, is hereby so modified as to allow pilots 
 employed at places remote from a marine-hospital station to be examined 
 by any respectable resident physician, whose certificate tiiat such pilot 
 18 exempt trom the disease known as color-blindness shall accompany 
 the license and oath of oflftce of such officer when sent to any board of 
 T'T io^?f ^,*^^^ ^^^ renewal of his license in the manner provided in 
 Rule 42, Rules and Regulations. Upon the receipt of the certificate a 
 license shall be issued the same as though said examination had been 
 mat e by a marine-hospital surgeon. This modification is not to be 
 app.'ied to appUcants for original licenses; they, in all cases, must be 
 examined m the manner provided in circular No. 14. 
 
 A second visual examination will not be required in any case and 
 mspectors will therefore retain all certificates upon their permanent 
 files tor reference in cases of applications for renewal of licenses 
 
 JOHN SHERMAN, 
 
 Secretary. 
 
17 
 
 CIRCULAR. 
 Pilots Incompletely Color- Blind. 
 
 l).-partimfutNo.4C. I TREASURY DEPARTMENT, 
 
 Steamboat Inspection. 5 Washington, I>. C, May 20, 1880. 
 
 Local inspectors of steam-vcsseLs are hereby authorized to (ixainine 
 with the colored signal-lightH all pilots applyiii^r tor a renewal of license 
 who liaye been reported by the examininf-xsurKeon as only hmmwletely 
 color-blind; and if the inspectors are satisfied, after siicli' examination, 
 that said pdots can sutHciently distinguish the colored siLnial-liohts 
 usea on steam -vessels, it will be within their discretion to renew the 
 licenses. 
 
 Local inspectors will report in detail to the Supervising- Inspector- 
 treneral ot Steam- Vessels all examinations made under tlie provisions 
 pt this circular, and accom])any their reports with coiiics of the examin- 
 mg-surgeons' reports. Local inspectors will make requisitions upon 
 the Department tor authority to purchase the signal-lanterns necessarv 
 tor the above-mentioned examinations, stating the cost of the same in 
 their requisitu)ns. 
 
 JOHN SHEEMAN, 
 
 ISecretary. 
 FroHi what I have said, it will, I tliink, be readily seen that trusting 
 the examination of the eyes to any "res])ectable resident physician" is 
 sunply useless. The reason given in Circular 19 is, that it is a hard- 
 ship tor a pilot to travel any great distance to where a marine-hospital 
 surgeon is stationed. But is it not sacrificing the community to the 
 individual, to allow such a pilot as that of the tug " Lumberman" to kill 
 the people and destroy property? There is not one chance in a hun- 
 clred that in an out-of-the-way place where a pilot would apply to anv 
 "resident physician," that the latter would know anything about color- 
 blindness, even if he had ever heard of it. He would have no appara- 
 tus to test by or book of instructions to guide him, such as are put in 
 the hands of the medical officers of the Marine-Hospital Service to be 
 studied and used. He would be more likely than not to call a pilot 
 color-blind trom pure ignorance, and, if not honest, might be readily 
 persuaded out of the belief. There is, of coiu-se, no surety and no hold 
 on the physician. Even the surgeons connected with the European 
 railroads, and hence men of good medical attainments, wholly failed, 
 althougii supplied with proper apparatus, until they had been thoroughly 
 taught by the experts in this sort of work. As a matter of fact phy- 
 sicians and sm-geons have left the whole subject of color-blindness and 
 Its detection, &c to the specialists, ophthalmic surgeons, whose particu. 
 lar studies enable them to take up the question l)oth theoretically and 
 practically in an understanding manner. Prom personal knowledjie I 
 know how difficult it has been for the medical officers of the several 
 departments of the Government to do justice to themselves and to the 
 examined with these tests which have been necessarily put in their 
 hands. As I said in my Manual, they can learn, and are now doing so, 
 ot course, often under great disadvantages, from lack of being abfe to 
 consult with others and learn de visu, which is here of such great value 
 l^or these very reasons the railroad surgeons in Sweden were all sent 
 to Upsala, where Professor Holmgren could teach them practically and 
 scientifically how to test. "^ 
 
 2 B 
 
18 
 
 "^ McvontI ri»iu(l «.t'(i mi nation will not be reijuired in any iohi;'^ nvvonl- 
 iiiff toCinMiliir 11>. Tlu' fiu-ts \vlii<h I Irnvt; ^ivrii in ivWnvnvv to actiii i red 
 color-bliiidiit'ss, tVnin iiijiuy,tV(>iiuli.s<'ii.s«', from al('(>li(>l,iiinl I'rom tobacco, 
 an;, I think, .sntlici«'iit proof of tlu^ need of testing' the <'oh)r-,sciis(' at 
 least as often as a liceiis*- is renewed. Most certainly the eyesij^lit, as 
 to form, shonhl be teste(l as often as tliat, which, with tlte testinj;' for 
 color sense, can all be (huu^ tiioronj,'idy in a few moments by tin; medi- 
 <!al otlicer of the department, wiio alone shmdd be intrnsted with it. 
 Tlu! laity cannot do this; it is a medical examination, for medi(;al men 
 to carry ()nt. 
 
 I have said tliat a person born color-blind dies so, and that it cannot 
 be altered or alleviated. Ho far, therefore, as conj^enital color-blind- 
 ness is concerned, one examination wonhl be sntlicient; but the (pies- 
 tion of acquired color-blindness must never be forj^otten or ijinored, 
 and the need of testiny for visual power at least once a year is abso- 
 lutely necessary. Ophthalmic surgeons know only too well how gvud- 
 ually-failiiiff sit;ht, from catara(;t or disease, nmy not be recognized even 
 by the patient himself, an<l never be known «u' detected except by their 
 methods of examininji' the eyes. 
 
 Incomplete! !/ color-blind pilots are, by Circular No. 4(5, taki^n out of the 
 hands of the niedical otticer, and allowed to be tested by the local in- 
 spector with colored sif,aial-lights. 
 
 The Supervising- Inspector-Ueneral says, in his annual report: "The 
 last circular was issued because it was deemed but a simple act of jus- 
 tice that pilots of many years' experience, without accident of any kind, 
 should have the fullest opportunity consistent with the public safety 
 to i>rove themselves competent to continue in the exercise of the duties^ 
 of the profession in which they have been edu(!ated." 
 
 Now, the color-blind pilot of the tuj,^ "Lumberman," who caused the 
 death of ten people an«l the loss of i)roperty, &c., might perfectly well 
 have been just such a case, namely, one that the medical officer would 
 record, in accordance with his instructions, "incompletely color-blind,'^ 
 and hence fallen to the local inspector to decide on, who, by the tests 
 he is directed to use, would i)ronounce him perfectly safe to hv re- 
 licensed. 
 
 It is necessary, ttrst, to explain to the board what "incomplete color- 
 blindness" is. It is to be remend)ered that the defect exists in all 
 degrees, and none of the Government departments have yet dtM-ided 
 the anu)unt iiermissible in any given case, »&c. By referring to page 
 40 of the United States Manual, it will be seen that I'rofessor Holm- 
 gren proposes to "classify the different kinds of color-blindness under 
 especial heads, to be able the better to grasp the whole." He says: 
 
 "We might, indeed, divide this blindness into (!ongenital and acquired ; 
 but, as we are cimcerned alone with congenital color-blindness, the 
 division is as follows : 
 
 "I. Total color-blindness, in which the faculty of perceiving colors is 
 absolutely Avauting, and where the visual sense, consequently, can only 
 perceive the difference betv/een darkness and light, as well as the differ- 
 ent degrees of intensity of light." [Several such cases are lately 
 reported.] 
 
 "II. Partial color-blindness, in which the faculty of certain percep- 
 tions of color, l»ut not of all, is wanting. It is subdivided into — 
 
 "1st. Complete color-blindness, in which oiu' of the three funda- 
 mental sensations, one of the i)erceptive organs of color in the retina, 
 
 I 
 
 ! I 
 
I 
 
 the 
 
 I 
 
 19 
 
 is WHlitiiij;; aiHl ill \vlii<-li, ('((iisfMiiiciifly, tlir colon-d \ isiiiil Held has 
 hut two raii;>«'.s. Tliis ■;toiii> iiirlti(lc.>, tiirt-c kinds, namely: 
 
 "(«.) K»'(l-l)IiiHln('M.s. 
 
 "(/>.) (Irccn-hlindiu'ss. 
 
 "(V'.j Violet-lilindncMs. 
 
 "2d. Incoinplctc (((lor-ldiiidiH'ss, winTe one of fin' tlin-c kinds of ('!<'- 
 nicnts, or |M:lia|>.s all, arc inferior in exeitahility or in nniMber.s to tlio.se 
 of the normal chnmiatic sense. This {;roii|> i'nelndes tin- winde of a 
 series of ditfereiit forms and dej;rees, a part of which, the sniierior de- 
 crees, which mifiht i)c called iunniiplch- mlM'nxhu-ss and incomplrfc 
 tfmn-hliiiihicss, {and iiiromplch' riolif-ldiii(htfxs,) constit.it^'s tlu' transi- 
 tions to the «'orrespoiidin<i' kinds of complete colorhlindness ; and 
 unother part of which— the ii:ferior (h-j-recs, whi<-h we «'all a fct-lde 
 cliroinaficntiisc — constitutes the transition to the normal sense of <-(dorH. 
 This classifi<'atioii is (piite practical and conformable to experit-iice. 
 We know no classitlcation which, tlKuij^ii distinj;nishiiij' accurately be- 
 tween the ditfereiit essential forms of a (h'tcctive sense of colors, draws 
 a surer, more dechled, and more juactical limit between the defective 
 sense of colors and the normal sense." 
 
 Now, till we liav«' sonu^ better, or more precis*', or more simjile, these 
 are the expressions and these are the terms the s]>ecialist and the «'\ 
 pert must use in describing;' or recordiufj his cases, namely, the condi- 
 tion of tln' examined, just as we must re<'ord the examiiied as being 
 iiear-si«:lited, or over-sif;hted, or astifjmatic, or liavinf-' vision one-lialf, 
 &c. They are technical terms connected with a technical subject. It 
 is not the fault of the subject or of the medical examiners that "the laity 
 do not thoroughly uiKh'rstand their use or si<-iiificance. Much iliist 
 has been thrown into the eyes of the community and of those in official 
 position <lesirous of doing their duty towards tiie community by ignor- 
 ant and wily jiersons using these terms expressing the varioi'is kinds 
 and degrees of color-blindness in a totally jjcrverted ami false way, 
 with the purpose of deceptiiui and with the view of showing the defect 
 to be but a great rarity, an<l by no means <laugerous, «S:c. 
 
 I M-ouhl illustrat(> my point by saying that if, after examination by 
 the various tests I have shown, I sliouhl re])ort an engineer or a i>ilot 
 as invniHpU'fcly cohu-blind, it by no means is to be understood that I 
 indorse that man as ItettiT or more safe than one I rep< t as completely 
 red or green-blind. In fact, I do not hesitate, to say that I regard 
 partial or incomplete color-blindness as >«ore da ngerims. For instance, 
 a medical officer of the Navy, inspecting recruits, told me that, with 
 any apparatus formerly supplied him, he could not be proved to be at 
 all deficient as to (!olors, yet that, at a <listan(!e, when he could recog- 
 nize the red port-light, he coiihl not distinguish the green starboard- 
 light from the white masthead-light. Testing him with the worsteds, 
 I tbuml that he was partially green-bUnd, and wouhl be recorded simply 
 as "incompletely (!olor-blind." Nowhere under the United States Gov- 
 ernment is it yet re<iuired to record the exact amount oX^ chromatit; de- 
 fect nuineri(;ally, as Ave record the anumiit of visual power for form 
 nunu'ri(!ally, e. g., vision, two-thirds normal, &c. Hence, no ajiparatus 
 is ]>ut in the hands of United States medi<^al officers to measure color- 
 blindness by other than the decision above spoken of, decided by 
 Holmgren's worsted test. A definite amount is rerpiired by the Ccm- 
 necticut laws, and the apparatus I have shown you is designated as the 
 m<»thod of determining it accurately. The medical officer I speak of 
 
20 
 
 Htat^Ml inoHt iHH.l.v that 1... w.m.I.I I„. „,o«t diu.«rious on tht- wutcl. all 
 . more., ns 1... wouM .o.uim.H W n^ht. SuH, u n.an wnuhl „ s, i 
 t.) •.«,„„' .Icf.Mtum rx.M.pt by tlHuouKli t.'sts in conipH.'nt Inuwls. Tl 
 
 a t.. ly n. („-hhn,l, iMMn^ ofton liKht, an- only t.m tlnnly <.<.nvi uhmI 
 
 hat tlu.^HhvayH aiv and ,va<lily .U.^mvc those about then, int th« 
 
 i.h.i that at^ th., most tla-y an, only a little careless or inattentive 1 e.^ 
 
 r ..on""! ""■''"' '•r '•'^.' ^"">' "i'^fi"«"'-^l»; '-f "< a .lista ee w e 
 the normal eye easily and instantaneously recooni/es then., th > coh'r 
 is Kone or l.e,on.es doubtful; henee, the pe<,ulia; .lan^^'r ' 
 
 1 In, truth IS thai, both on the railroa<ls aiul on the ocean, each and 
 every decree of chromatic delect is dangerous to life and prl, per y 
 I iui«ht iilmost say, in inverse ratio to the amount, becais.^ the 1 -sser 
 
 ?; k n ! •'armlessness. Experience on the railroads has pn ved 
 
 fd V V il 7""''"'7^''' >•• , ' '"'"''V' tlM* tinu^ will come when the commu- 
 
 e;u;d:;';^a;;;r::u.in::?:^'^" ''"•"^•"" ^'■♦^"^ -i<-»i-<i.u- ^ .aihoad 
 
 the l^'lll'lllS''''^**''//' '"'•'' ;'^" ^'^'' '"'^•>' '^" ♦'"'>' 'ittempti.l to test by 
 the si«ual-li«hts even those who were found by the suri^^eons vomulctdl 
 
 such were 'n^r';;'}- 'T" ■'""^■^' 'i'^'""-^ ''''"'' ''^»"'« ''' tluM-ondush;;; tha? 
 .such weie not detectiv." or dan^^eroiis, and be perfectlv willinjr to re- 
 Ucenxe then, even witho:;t the pressure' spoken , f in tlu^e, Sof the 
 8uro,M,us ot the department. Still more likely would tlu,y b to ,» 
 themse vcs that the partially <M,h,r-blind Wi^re either notso,or fio 
 wSv";'i^^;i T •' f""' T^ ^'^'^ '" «""*'^' >'^' I'^^rtV^ctly site ^ ru^! 
 
 Hkc l\- iJ uh', '"'^' ^''"'' r'^'^'f^' *1*'^"^'*'^*^'*^ men, who either see 
 8i«n.il-li«hts when near enough, and when in a room -.uess at them 
 
 it'dt'/'T' TT'^^^\ '''' l>^'-'i«<'ly tliose who are,(la,«em : and 
 S .m''t^T ri ''^'''^^ '•";'" '^''*l' -i«""l.lights, and giving their offlc al 
 sanction to the license, only renders them more dangerous, since then 
 
 ^l^r" '''"" '''"^"""'^ '"'^ *'•" ^"^ ""^ ^'^^'^ ^■^•^•^•l'^"^ from defect 
 A competent niedical examiner will with certainty very quickly detect 
 S^^^well' l'''^'"i''""^^"'''^^^ ^^ Holmgren's worsted tL^ Si e can 
 on. tI , T; ''^ l^'W-^V^l*!^^^"'*"'^' tliat such blindness is danger 
 ous. lest^iug with signal-lights will not show this danger, and this is 
 the special reason why I appear at this time before this boaSlLtW 
 
 8eiZand'hif^.^n^^>"*;''""*\'^>^ ^''^ ''''^ '^ ^"'^ out a man's 3 
 Sc 1 Sfl .n^i^ TV- ^*''" rf ^"^' ^**'^"^^^^ -^'Snals is to put up the 
 mgnal-lghts and ask hini what he sees. Upon tliis very uaturallv i^ 
 
 tS *^^^,^"'^"1^^- ^.^: f^ 'Rowing local inspectors to test wS Sal 
 lights. The same mistake has been made by other boards, and without 
 
 dStive% i'lnf^ u^ 7, ^'^'l^"'^ *« ^^'"^ wenrnve to retain partially. 
 oSis if tH*. Ml?r''S"^* f^'^I^* unchallenged the asscJtion and 
 opinions ot the Medical department in the face of such seeminLdv 
 common-sense Ideas, that to take a pilot out and ask him the names of 
 off S'dT £'''^' "^^'•'' "^ ? ^'^^•1 "P signal-lights a short diSce 
 
 So^t hl"c:rr/>e^yi:f/^^ ^^"^^*' '^^^''^ ^"^ ^-^-* -^ ^^^ 
 
 It wiU be simply from my lack of prape.iy presSTthe subjS 
 
 r 
 
 .. 
 
f 
 
 91 
 
 Now, pnu,ti,.tllv, this is wiuit frJq,u..,tly .hm-ui; uh 1 nu'. v tl . u * 
 Ziliuttniu ^ i ^' •' ''.•""••'""•^•l <**' ""'1 ''^' <'<>"»'H iMu'k With his inn. 
 
 lij?l t as the l.I.usli-jrreen oiu. sl,„w.i l.y Dr. .hAncs w o Nh, • hll^ 
 
 ^i™'*,.''",';:::!:;'' :;';"'^ t'- "^""* *'"' "'"--s™'" ofV.,,";-! .'',,;rvo 
 
 to attcinpt to j.-,v(5 an opinion. All sdentific exiuats w lo riV l ?n 
 practn^al exponenco entiroly apv.Mvith nu> in this/ ll^olV s i iji{"^ 
 once of opnnon. Th. Sapervisinft' Surgvon-Gr uTal^Vl Ui^vs h . 
 Annual R.port, p. 21: "When si.nn.l-liglts are pr ,ose s'Ss . or 
 
22 
 
 color-bliiHlnrss m o])i)()sitiou to tlie united ()i>inioiis of the best inforiited 
 oplitlialiiiologists 111 Emo])e jind Aineiica. it seems to l)e asstniied tluit 
 the m(;rli(.al examiner lias a peculiar and sjieeial interest in the rejee- 
 tioii <»t the eandidate. This assiim]tti<»n needs no refutation " 
 
 I innst 1)e allowed here to read from my Manual, i). 183, what a verv 
 pmeiised seiontitie exjiert, J»rofessor Ilolmoren, savs in reterenee to 
 testiii--- railroad employes Avith lanterns, since «»f course the same ap- 
 ])lies ft) testing' witli si->nal-lij>hts: 
 
 "The HTcat majority of ]»eo])le are inclined to believe that the best 
 niethod (it testing- The railr<»;,d pemmnci tor color-blindness would be 
 the use ot the signals employed, namely, the lanterns and tlaj-s, as be- 
 my' the most direct, easiest, and suitable. This, to every i)ractical man 
 Avlio has made no specialty of color-blindness, is so obvious as to be a 
 recognized tact. Any method which we are here concerned with has 
 only the aim of iireventiny' the mistaking- the si->iials bv the resi.onsi- 
 ble permnueL What more sim].le, is asked with seemini-' rij;ht, than 
 to he assured that the radroad em])loyes can distinguish the signals ' 
 VN hat other me. hod can quicker bring us to our desired end'' And 
 how can Ave reac^h it more readily, since these signals are in use on all 
 railroads? But there is another eondith)ii necessarv. The examina- 
 tion must not only juove that the men are able to distinouish one, two 
 or any definite number of lanterns or fiags, so or so often, but that thev 
 can distinguish all tiags and all lanterns under every condition; in a 
 word, that their color sense is as normal as we have a right to demand " 
 lesting with lanrerns becomes but a hazard between the examiner 
 and examined, where the latter may rea<lily often win, and where the 
 tormer bears all the loss if the examined afterward fails but once Of 
 course the «'xaminer is sure to win, if the i)lay is continued ion- 
 enough, t(u^, if we know beforehand the examined is color-blind we 
 can sooner or later cause him to make a mistak<> as to the cohu' of the 
 anterns. But if we do not know that he is color-blind, and aiv testin..- 
 inm to (lecide this, then we shall soon find how unada])ted this method 
 IS, and how impractical. Naturally, much dep.'uds u]»on just how it 
 IS employed. For instance, let us supi)ose that the usual colored lights 
 are sJiown to the examine<l, one after the other, and he is asked their 
 color or meaning, whilst from his answer his color sense is to be .lecided 
 on. As alr«'ady shown, the color-blind wwy decide righrh", but we need 
 hardly add that the normal-eyed may fail from carelessness, inatten- 
 tioi:, oreven slip of the tongue, neiice. a color-blind is passed as 
 normal, and the ivverse; so in this form tlie method is not practical 
 10 attain certainty the test must l>e c(mtinued and repeate<l till the 
 examined's color sense admits of no doubt. But In.w often must we 
 repeat m order to be sure ? How «»ften must mistakes be made in order 
 to prove color-blindness? Or how often may thev b(> nuule and the 
 < etect still be considered not jn-esent? It is, of course, imi.ossible to 
 (lecide these (piestio..s. Certainty naturallv increases with the number 
 ot trials, but the method is still untrustworthy, and it is dei.ending too 
 much ()n the knowledge and experience ol the examiner in reference to 
 col(>r-hIin(lness, to exi)ect a decision from him on such tests." 
 
 Ihis, now, is the ])ractical experience of a thorough inedical-exi)ert 
 examiner atter testing a great many railroad emplovi's. He has been 
 sjieaking, too, of the 'pl(^stion of lantern tests in tln^ hands of medical 
 men spe(;ially instructed. If thc.v so utterlv fail, as is evident, how 
 would It be i)ossible for hnud in,wector.s to decide whether there was 
 
 r 
 
23 
 
 ■ 
 
 color-blindiicss, and whetlier it was dangerous, &c. As I said, any de- 
 gree of eolor-blindness would very readily pass uiuletected by them; 
 the most dangerous cases, namely, the partial or incomphte, Avouki 
 most surely eseape and be declared perfectly safe. This, too, by the 
 most lioniist inspector, unintluenced by surr<mnding pnssure, from 
 whicli, vc])orts sliow, none are free. 
 
 The same sort of pressure that was a])plied to this board was brouglir 
 to bcjir on the Board of Health of the State of Connecticut, to whicli, 
 trom hicic of personal a(^quaintance witli the subject, tlun- also yielded. 
 Xiiey allowed defective em])loy{:-,>, to be tested bv wliat tliev themselves 
 a^id tlieu'coiuisel demanded, lunnely. Hags and 'lanterns at eightvrods. 
 liie results trom tluj worsted test were, however, entirely substan- 
 tiated by these second examinations, an account of wlii(;h wi'll be given 
 you by Dr. \V. il Carmalt, professor of oplitlialmoh.gv at Yale Uiii- 
 versity, and who was one of the examiiu'is under tlie State laws. 
 
 [Since the meeting of the board, full reports, &c., have appeared, 
 irom which the following are cpioted as of special interest:] 
 
 Di. Chamberlain, secretary of the Connecticut State Board of Health, 
 reports m the Boston Medical and SurgicalJournal of Februarys, 1881, 
 iis toilows: " ' ' 
 
 "It so happened, however, that, at tlie outset of the examinations, 
 sevcTal engineers, closely c(mnected with the principal oflicers of one 
 ot tlie most intlnentuil roads, were found nuu-e or h'ss defective, ami 
 others, of greater or less influence ])o]itically, were involved. A special 
 api)(|al, signed by 6,000 or more, including nearlv, if not all, railroad 
 presidents and prominent officials, as Avell as bv leading politicians, 
 was lUTseuted to the board of health, asking tliat the methods of ex- 
 amination be entirely clianged, and practical tests onlv emploved, such 
 as tlie flags and lanterns used in signalling. The gre;it cry was that the 
 men be tested by the tools with which tliev worke<l,bvi)ractical t<'sts— 
 as it those were not practical which ascertained the fact. sur*'lv, and 
 with the greatest ease and rai»i(lity. In (h'ference to these repre"s«Mita- 
 tioiis, however, those condemned by the worsted system were allow^nl 
 a ti'i (her trial by flags and lanterns, at eightv rods.' The results of this 
 were soimnvhat surprising to the iiu'ii. Out of tAventy-tbur men exam- 
 ined by Dr. Bacon, and found color-blind bv the worsteds, twentv-one 
 faile(l by flags and lanterns, and the others 'answered mon' or les's un- 
 satisfactorily. Similar results were obtained by Professor Carnmlt the 
 other examiner." ' ' 
 
 From the Report of the Connecticut State Board of Health are taken 
 the follo.ving: 
 
 Extracts from the Report of Dr. W. T. Baeon, Examinhuj Ophthalmic 
 
 Svrgeou. 
 
 "The whole number examined was 1,029. Of these 4.6 iier cent had 
 ■color (lefects and 7..") ])er cent, had visual defects. 
 
 "Those failing to show satisfactory color perception bv the tests 
 enumerated were tried with the flags and lanterns at eighty rods, one or 
 both, in use on the road. Of the twenty-five coh)r-blind to red or <>reen 
 tAyenty-four appealed to the Hags, and twentv-one of these failed in 
 distinguishing red from green, while three named the <'olors c(UTe<'tlv 
 In testrig with the Hags, one of the officers of the road was always 
 
24 
 
 present, and his color perception compared with the euinlov^.s and wifh 
 Hune My experience with the flag Lt has couvLct dC Ui ^ u 
 wholly nnrehable method for the detection of color-bl i l ess and niiv 
 have a worse effect tlmn if it had not been nsed, by giA^^^r" to^Ccdor^ 
 
 uence Avnicn Jie did m)t before possess. Even those tested l»v it .ira 
 not satished, as their failnre is almost always attSted to some can' e 
 as the li«ht, want of sleep, &c. The three who calltS the co or^ or' 
 rectly were qnite blind to green by all the other tests nsed -m uv in 
 
 Z TZ''''^''''^?^'^ •"'""* '"^^•^' «l^»8erons thaii tl ose nnabte o ,mn e 
 the flags Besides its nnreliability, the test with flaos Zl lanh™ 
 IS impmcticable when a large nnniber of men are to be tried a,^? 
 frthV'^ the ernp oj-^s of the roads in this Stat. cSd have been te ted 
 by this nethod during the three months given by the law without^S 
 loss of time and inconvenience to the railroad compaS.^ ^^''^ 
 
 i.ltun^7Zv^y^^^^^^^ t'""^ Massachusetts Leg- 
 
 fr.1 !vl Vi ^-^ ^*' ■^^^^' *^^' following evidence was given bv the 
 
 VessSrf '" who appeared before the Board of Inspectors of St'ean,^ 
 
 JL^""' J^?'^«i^«- -^"ow in<> to say one Avord to explain to the com 
 mittee. Those re-examinations Avith flags and lanterns were wh it t m 
 board of health felt forced to allow froin the i>m?«. rpuTupmithem^ 
 and therefore, their counsel called for that fbrm of eiaminEn and 
 that Sdti'ff V\^"^'^^^ ]'' '^^^^'^•^ '^' P^'«fe««or sak™!4^"',neu 
 
 '; Professor Oarmalt. That is just Avhat I Avas on the point of s-iv 
 
 tSs of'thos^'itnt^^^^^^^ '"'''' '^'''''^ "'^ '^ iStl S: 
 
 if ...mI ! • T^^^ ^'"^''•^ "'' ""^' t^'^ts with flags and lanterns and 
 It made certain rules as to how they should be done I m-otes ed 
 
 icgciuitn as .ururate — 1 Avould not alloAv niAsolf to s-iv ti..if fi...f . 
 wa» free from .•oloi-Wiu.lnoss becan.se l,e\ "'»' le „ -ll ti ' H ,'i ' 3 
 
 AAas. The modified rules, as we called th.'m, were for th.' ..n.tect on f 
 
 old en.ployeswho ha.l been on the road for f ve years <rmr, ulwlo 
 
 had shoAn. as they sup,.ose<l, iheir <-apabilitv for .lo ng h, • l',, ^^ 
 
 Ik mo<l,f,e.l ru cs avctc not applied to those innv en.pl^v 's vh • d 
 
 een on tlie road but a sh.n-t time, and were still ]eai4 i^^tl.c i b s 
 
 ness, an. Avere not regarded as eoming umh-r snel, a reg Pti T 'v 
 
 lad not h.arn.'d the board sai.l, the peculiar d,..ree f i t ■ s 'v t 'V 
 
 UM i^tedueat,.d tlieir eyes, if they were color-bliml, to d.I e hj tK 
 
 httle differences, and tliey Avould not run the risk vith then Ts til 
 
 cmne back to that point again, with s<,me other s a is Cs t "I't 1 h m / 
 
 But to g<, on: Of the twenty-eight men whon, 1 1^ drZ^M ei 1 1 
 
 f them were n,.wen.,,Ioyes, and did not come un.ler tlie t s f .Ix- ?, 
 nation w.tli flags and hinterns; tlierefcne, it leaves twent who i 
 
25 
 S'S iS/SrS ^0 *»»""«'? "»' "-e ^i-Sle M»n that I e^a,„. 
 
 The uselessness of lanterus in determining the color sense in onm 
 panson wi h the other tests, especially that by the woSeds has be ,' 
 equally well shown through the reports of the surgeons of the M^^^^^^ 
 Hospital department. And further, the dangerous chLcteroTth^ 
 degree of color-blindness which Circular 46 would have Yheloc'd ^ 
 spectors decide on, is equally well shown by these surgeons' reports 
 
 burgeon Button, at Detroit, reports the details of suXanexamivL 
 tion, and says as to the pilot, "but when tried on ligLs of which m 
 knew nothing It confirmed what I decided withiri fl\e m^nuTes afte? 
 commencing the first examination, that he was both «S TndTedUhJ 
 and my diagnosis^completely color-blind' would sbmd^ ^ 
 
 ao tar as the test on the river amono- vesspl^j i« «.,...r.^r.,.«.i t i 
 maintained that it is no test at all. VeTs^ls' Ugbts have S pdhm? 
 A process of mental calculation, coupled with hirSedL of S 
 
 S'''^?.T^'^"«' ^/■*^"'" "^^*^' e^i^les him to (iSethf matter 
 after a little reflection as to the position and course of the vessel 
 independently of his chromatic sense " vessel, 
 
 That all these helps will tail the color-bhnd is shown bv the i>ilot of 
 
 % / X. . ", ^'^^^ ^^^ <^ase of a man incomnletelv or narH-iiUr 
 
 ciotftr'm.r^/.ir''"-,- ^''"' '»;=?' ^^po^'or te«tr&iaC« s 
 
 uose-to, anil, ot course, reliceuses him over the snraeon's he-id >.'..» 
 
 ves'seTtteelvtr/'"' '^ ^"'™-«'S'"" "» " <Snc™ an'^T, iting S 
 vessel thereby, will honestly swear it mm not lit How often iJ^it 
 
 carried out every man who showexl anvc<>lor-blindiL's bv tte wor^^^^^^^ 
 tes sli^wed by his direct mistakes o^ uncerfaintv how dang^^^^^^^^ 
 was. No local inspectors with sigiml-lights, or an^ of the uinstru^fed 
 aity, can thus make evident the da n^^e? either to themseh'es or ot < . 
 This seeming ability of men who have been < vl m^^^^^^^^^ 
 inedical exannners to see colored signals close-to r mm t em I • J 
 always correctly, has been the bugbear of all offichi s I Vvo i^ 
 ever, never found any officials wlu> would Sient^y t^teii t o ^. n e 
 ^m"n:>t'f:^'w:^^^ coh.i-bliudteied by Ledic^ ex^^lii^ ^ 
 ,ni.i.f / \ tia.kly admit that they were mistaken, however fiiev 
 might art when subjected to the pressure of surrounding'cirJum.tam-ef 
 
 Tf/iftoT"'^;?' J'''''' 'Y'l'^:^ ^^\^ '^P^^* ^f *'^« examination bv Surg,.,n 
 llutton At reiiuest ot the Supervising Surgeon-General •mrl ^7 . 
 
 Si^t^ V :;:h t!'di!;l"''"' ''^^ '^^«^'^:™ cai^d n ^ni\ot,id : 
 
 ff n i 1 • ' *' eoinnuMitiug on it in explanation. Ffe spoke of 
 
 It in terms ot praise, ami, after tin,, explanatorv <lis(aissi,>n thH ,, • 1 
 ot Inspectors adnntted the correctness of Surgeon irutton's\!mi ill 
 
26 
 
 the Annual Report of tlu; Supervising Surgeon-General of the Marine- 
 Ho.spitul Servi<!e.J 
 
 [Some two liours were tlien spent by the various meinl)«H\s of the 
 board in questioning Dr. Jetfries and Professor Carmalt, in order to 
 satisfy tlieir (h)ubts, or liave inisuiiderstandings <;leared up, by ])ersonal 
 explanations by these gentlemen of the various tests, and especially 
 the apparent contradictory evidence of (lofect as shown by the worsteds 
 . and the signal-lamps as they had been use. [. The board'flnaliy a}>reed 
 with tliese gentlemen.] 
 
 Dr. Jeffries resumed: Our explanations liave slio\vn the great danger 
 which may arise from these examinations being taken out of the hands 
 of the surgeons, and they have equally shown how readilythis mistake 
 was made; a mistake most apt to be made at first by almost all offlc^ials 
 wlio have to frames laws and instriu'tions as to these tests, which are 
 so incomprehensible till seen and understood. A desire to see justice 
 done between the community and the pilot alone actuates the criticisms 
 made. 
 
 It is with great pleasure that I testify to how far ahead of our 
 motlier country, England, this board is in this matter. There the tests 
 ot masters and mates for visual power and <!ol()r-l)lindnes8 have been 
 left to the examiners in seamanship, of course non-medical men, with 
 a result, reported to Parliament, th; ^t is simply ridiculous. 
 
 [NoTi:.— Keforeiico should be here made to tbo speech of IIou. B. W. Harris ot 
 Mass., Ill tlie U. S. House of Representatives, Feb. 18, 1881, in Congressional Record. ] 
 
 On the other hand, across the channel in Holland, very strict rules 
 are carefully api)lied by competent medical men. I quot«^ from my 
 Manual, p. 262, as follows: " Regulations were also propo.sed to the 
 government by Professor Donders in reference to the navy and mer- 
 chant marine; and they are now aocepte<l and enforced, as seen from 
 an order in the same ofBcial paper, " Nederlandische Staats-Oouraut." 
 of March 3, 1879. 
 
 "The Minister of the Department of Industrv, Commerce, and the 
 JNavy, referring to article 2 of tlie royal decsree of Feb. 17, 1879, (Staats- 
 blad, No, 37) in regard to the carrying out directions for the (examina- 
 tion for a warrant as mate in the merchant marine, as directe<l by 
 royal order of May 5, 1877, (Staatsb^ad, No. 98) has decided to re- 
 quire — 
 
 "1st. In the test for visual acuteness and color-sensarion ordered in 
 the article, the following: 
 
 "«. Normal vision,withoutcorrecting-glasses, with one eye, andatleast 
 one-half of normal vision »\ ith the other eye. 
 
 "ft. Both eyes must be without manifest hypermetropia of a degTee 
 above D 1.00, and in one eye at least normal vision. 
 
 li ^ ^T' I ■ /I -I -I . ■■ . . . , . . - 
 
 U 
 
 c. Visual field not limited in either eve. 
 
 "rf. Eyes and eyelids externally healthy without habitual congestion 
 or imitation. 
 
 " e. Color perception perfect for transmitted light in one eye, and at 
 leant one-half in the other, accordirg to Donders' method. 
 
 " Al. The report and declaration of the expert, as required in the above, 
 shaU be f'onsidered valid for one month only from the time the test is 
 made. 
 
 (Signed.) "TAK VON POORTVLIET. 
 
 "Graveniiage, Feb. 27, 1879. 
 
27 
 
 J!JnV^t-' "h""^ "''^'"'' three oi)hthalniic snrseons are aj.iM.intcd as tl.e 
 Sen." " ^^^"""»t^^^'-^ "^ A.u«terdani, Kotterclmn, and J.eeu- 
 
 now different are these precise re-nhitions, and the means of earrv- 
 ii.« them o.it from the h,ose n.ethods en.ph.y.Ml in Kn-land. H > w 
 I'uu'h hotter also, tlian the re^nh.tions of onr Tr,.,surx C artnn. t 
 ni winch no dcfinif. standard i.f vision or e..lor-l>lin.lness isC i -^^^^^ 
 and l.yu'h.eh ],r<M-isH.v the most (lan-erons eas.vs, viz the i,?" ■.! v 
 
 s t sf ^^ ^i^ ;"■*■' "f *^'"'«-^'i""'^ '>.y t'u. local inspector throng.!, 
 
 ll.'pcated notice has been taken <,f the especial dano-cr on the s.-a. 
 i^ri^-M;."^.i.I "*""■'' ^^^*''' ''''^^•^' ^^*^^^*^'^ tl'^ ^^'''li'-^'l So,.ietvof 
 
 J>Jlf nZf?'' '"'''"'^" ''"'*;•' ^*''" ^'"' "'''^'"^' *»<■ ""'<' <'"""tr.v only be of 
 ^ ;?. . vv *i *«^»'"'^-vesseIs from aH parts <,f the uorhl pass ,.ach 
 
 ew ;,f bn 'ol r 'Tr'' "'''^^' ^^1 ''''" ''^''1* ••'■^ 'ittle if the olti.-ers and 
 
 1 1 , 1 e H. ^ ^'^ ^'T "/r"' "^ ''"'"•^' l'^'^'<**'l'tion. If there are color- 
 DlMul on tlu> other vessel, collisuni nniy occur. 
 
 "As to the i-ailroads, it is not of such im])ortance that the reouire- 
 ments as to color-blin.bn'ss sho,d<l be the same in all (-(.untries. If one 
 countiy has one set ot reonlations, and another a differei.t one, whilst 
 tun- ;"3"»*''\'"> •;^'""i"'';ion, it concerns only the indivi<b.al country 
 law." ''■' '"'''''"''' '* '' »''^<-'s*^ary to have an international 
 
 I follow these sentences in my Manual by saying: "The test for 
 
 inM.^: m? .Vt?^'''7 'V "'"'l*^*' '" ^'* '••' i'«'"<lily carried out bv the 
 
 sm«eons attach.'.! to y.-ssels, espe.-ially naval m.'.li.-al .,rticers. there 
 ca be no jxreat.lit1i.Mdty ni havin- an int.'rnational ..•.mimission met 
 :1 H r h'" ^'^^^'■r^■^'l•'^^■^l'''»l ^•••v.-rnall th. navi.-s an.l nuarhant- 
 inaiine..t the yivat maritime nations at h-ast. It wonl.l th.'U be as 
 readily reco^niz.'.l that every .)m.vr an.l man must be abh- 1<» iH'rte.-tlv 
 AvhatTlu'fjneim'" '" "'*''*'" "^''^-^ •''" ^<» '^"•»" ^^'l'<'i'«' they belony anil 
 
 slu^nld hf^ e.jnclmsi.>n in iny Manual is: "An int.n-nati.mal .'..mniission 
 ^honl.l be .-alle.! to establish rules f..r the c.)ntr..l of .•.)lor-blin.lii(.ss .m 
 tlie sea, an.l the .'arrynio- out th.' same .'xaminati.>ns amoniist nilots 
 
 li?r,n'T'i'" . '*''''■'' 'i '^t^''™^'^'« '"'<l sailing- vessels, in the navies an.l 
 tiie mer.umnt-niarine." 
 
 As the members of the board well know, a petition in favor of such 
 a conmnssion was ])resented to Congress, r.'f rre.l t.) the Xaval C.nn- 
 nuttee, an.l most favorably re})orte.l .)n by the intro.luction of a bill to 
 initiate it by the Exe.-utive. This bill may .-..me up at th.- next s.'ssion 
 ot ( .myress, it not reach.'d by the ])res..nt throufih the petiti.)n. Such 
 a (ionimission was stronj-ly favore.l by the S.'.-retarv .>f the Xaw in his 
 annual rep.)rt for IS8(>. Its spe.-ial value t.) this Boar.l of Su i). t vising 
 Insptictors .)t .Stea,m- Vessels, all tlu' memb.-rs .;an r.vilize. The rules 
 an.l regulatmns ajire.'.l upon, ami tin; standards .)f tests and re.iuire- 
 mentsot visual power an.l cohu- p.'rc.'pti.m, would be a basis for the 
 board to a.-t ui).»n whi.'h n.) ])r.'ssure c.mld aff.M-t, an.l relieve the in.li- 
 vidual members ot the..nus an.l the resiumsibility, whi.-li hasnaturallv 
 caused them so much time and trouble in their attempts t.. .h> justice 
 
28 
 
 pSp£i£:£=SS;S3 
 
 REMARKS OF PROFESSOR CARMALT. 
 
 Mr. President and Gentlemen of the Board : 
 
 tion'Sl;;;^.^*'' '"^'^ nothing to the scientific exposition of the ques- 
 Tion 01 colorbhnduess and visual power wliidi Dr T«.m.i..t, i...^ i ^ T 
 
 the'S'ofV f ^'?f """ asl^Jni^erVt^t^i it^ X oyS Iff 
 the fetate ot Connecticut has, however, given me a famili- itv wiflfti?! 
 objections urged against the'law of that State whicr^ 
 law fof Sr. ''' ^^'' i^ niakingup your niindH a's tX' i hSbmTy of a 
 IriiTnlidoyS""'*"^ ''^"" ''''''' ""'''' *^- ^"^^tations of tEelt? 
 fh J^ qiiestion which almost invariably follows every exposition of 
 the Holmgren worsted-test from those wo have had to do S Snil 
 
 u» tUb accuiate so tar as they are conceriu'd' tlipv <1m Jaf,.-.^ ,.,i, .<- 
 ca 1 c„l„r.bU,,d,,e.s, b„,, D^tor, d,H,.slt foL^^^^ 
 
 rf;i.J^4^'^'\'^"*^ noimal eye can determine with i)re('ision." 
 shown vvi;rr' '^I^l^'^^^'i^!'^' the construction of which Dr. Jeffries has 
 shmMi 3 oil, has proved that the normal eve can see the c lors o^' Hut 
 
 2^^ LUC spot oi iignt, to determine its color at 10 T '^ nv <> r<i,.+ >'l 
 the case may be, dep'ending upon the anSt orJerr;^ of his colo 
 
 Ihe .ame innety-six percent, who pass the woiWed test lass^m.s. 
 fiiUy lie test with Bonders' apparatus; the idenS £^r p ?c^t w^ 
 fhc Do !f.r''^''^'^r'* "*'"¥ mistakes' at the sixteen-feet Istancc'with 
 t ,?s,?^ 4^'^"r-*"-' ;";? ^'r^/>Wiged to move up (.loser to it i or. U^ 
 to be sure. >ow I insist that the spark of light reiiresents evil IiiIa 
 signal-hglits of your vessels when carried oft'tar enough ; bS }]H-'"csts ^> 
 
29 
 
 ^1.. n/r "^ ^•'^ '''^'P'^' '^"'^ ^^"«'' *l^e incompletdy color-blind 
 
 men ot your rules pass successfully, are not one-tenth, nay, one 
 dredth, part so severe as the remaining ninety-six Der ce t -ile n .itl^H 
 In fact, they are no tests at all. The test of I S's im n hr strnf^H.' 
 IS not whether he can lift 5, 10, or 25 pounds, \v e S he tn lift 
 «ay 5a5i pounds. On that last half-piund ot^ visualS e so to s fi k' 
 wdl in the all-important emerftency of fog or narrow (-ha i^el (Spend 
 the lives of perhaps hundreds of persons. Holding tin, ..n. t shfe iSts 
 
 Zr:' '^"' ^IT "*"^y *'^V ^'^^"" '^ ">"« ^"«t«nt lr,m hcM nan; is li ? he 
 hrst ten or htty pounds lifted in the illustration above give i. It s no 
 prootor evidence that he can see the smne thing ac<rumtev at four 
 tunej, tlu^ distance; and, even if he does not fail, vou im s see that 1 e 
 has had an even chance of guessim, right. 
 
 That such men do fail is certain, even on such low tests -is avpi-p 
 adopted by the Connecticut State Board of He.lt , m petition of t7ie 
 emphjyes, which was that they should be exa.nine'i J^t rods, n 
 the "flags ami lanterns m common use on the roiu in (.uestion " To 
 say nothing of the flags, which v.ried from a <liitv b ack re I to a 
 clean white, the Lmterns, as .ppc-aling more *lire< tl\ to your ,■ ^se 
 might, by tlie t.-rms of the rules, vary from the head-light ot'^eim^fe 
 to the teeble switch-light on a turn-out. The han<l-lant ™ ot con 
 du.-,tors, brakemen, &c., have no flxed standard; and, altlm."' vo„ ue 
 
 nK)reaccurateinyour.-H.sfrMc^w,.s,Di^Jemi(^shas's]M,wnv^.^S^^ 
 
 the intensity of the light must be in ,>assing through the va r islv nu m^ 
 
 lactured glasses found in the shops of the shi],-chandler, &! ^ 
 
 with flwf r.?^'""i"''*?"- '"^"ti«»^^!' -I endeavored, as fairly as I could 
 AUth the ridiculously inaccurate instruments at my disposal to net .it 
 the man's color-sense, as he would have shown it bv tL Donders n' 
 mratus^ To this end, I surrounded the lantern oiwdUideTbut o e 
 with a black box, so that there should be no side reflection to guile 
 him. On the open (or front) side I passed the slides of c()l,,red ahisses 
 to represent the ditterent colors of the signals, and tl en bv a moner 
 system of signalbng and clerical assistance, an ace. m e recoJd was 
 kept, respectively, of the slides I passed before the lanterns, Ind The 
 m swers which the man made to correspond. I used for sM^ La-een 
 red and smoked glasses of difterent intensities, made by usino S 
 slides respectively single or double. I warne<l the men, inUvance of 
 
 h^ t fJftrV ^^"' ^l^^'^^ to them that there was no 'Sh* 
 mit; told them they must give the name of the color, hnt if it wis 
 
 not call It a 60/or ami the correct re])ly would go to their credit If 
 
 IT^H'^- ! ^"" ^'^^'^ ''''' t'^r^'"'^ ^»"'^ ^'->- «"^'^' it the name of a cohi- 
 It was evidence against their proper color-,,erceptioii. The distance' 
 eighty rods relative to the size of light used was so short that a peS 
 with normal color-perception had no sort of hesitation in lainini t e 
 colors immediately and promptly. As the rapiditv with w likl tit e 
 cision IS made is of course an element of great pVactical imp or nee 
 they were allowed Ave seconds in which to tell the color iS 
 
 nln^'^ V Jf ' '"^^^'f ^^''' conditions mentioned so stronglv in'their t nT 
 most of them made errors which, in the first place, were characteTil?£ 
 of the delect, and in he second wouhl have been Altai to the sal^'ty of 
 their tram it made when on actual duty. ^ 
 
 1 )vill not weary you with reading the whole list. Let it be sufficient 
 to give a couple, more or less, of the most characteristic, aftei-, in Sii- 
 
30 
 
 
 Dark smoke ho ,.alle(l Kod, 
 
 ^♦'<* lu' ciilU'tl Giocii. 
 
 ™'» ■: J'«3 called Dim White. 
 
 yy^V led lie called White. 
 
 Liyht smoke he called Green. 
 
 JJ^'^'P it^«l he called White. 
 
 Deep green he sai<l, '' Don't know." 
 
 liiiiPiili 
 
 made, botlf ^Z the\^!,Sls l^' if ^^'f. '^^'^kes he 
 
 a.qui;.ed (it^ nu.y have K'sSlnp v e^^^S^^^ 'jj;^ ,':!;L:^^^^?I -^f 
 this man, all the others were less th- n t .i u f « I ^ T' ^'^V^f ^ 
 
 m addition, the sniToiindin<-N -n.^ «ii..i. ..w. +i. '^'^' ".M « npecuii^ it. 
 
 P 
 
 J^ 
 
,n 
 
 f 
 
 J 
 
 u 
 
 81 
 
 of health, with their cohjml hii.terii.s, one man iuulavgomg the exami- 
 nation, the i-.>mamaer, eolhu-te.! togiither a few feet awty, vvere discnss- 
 hf.?Hli^' f ; which they eould see alsc,; some question arose ammig 
 these last as to a eertain liffht, Avhen one spoke up, saving: "If voS 
 want to know how a whiter li^ht looks, look at the stars." Thev were 
 Mnf,imnma tor a standard; their comrade ffave them the informa- 
 tion sought tor, the use of which had undoubtedly stood him in uood 
 stead m times past, just as it has stood by your color-blind pilots, and 
 Avil a«ain: but unless you can guarantee to them a star-lit sky, or 
 
 S. 'I'^H*'^'^'^'* -n"'"''^ "' "'^ '""*^^" ^'^^« "" ^■"«' «i' ^'»n» ov snow to 
 stiirl) tlieir l)rilliancy---you are putting them in positions of responsi- 
 bility entirely beyond their physical powers. 
 
 I thank you sincerely, gentleme.n, for the attention with which you 
 have listened. 1 wish you could see that we are presenting to you a 
 problem as ciipable of deinonstration as any you are familiar with in 
 geometry. If the color-blind man puts along yntli the green worsted 
 a light-bromi, or s ate, or gray, and, with the brilliant scarlet worsted, 
 a dark-brown or blacik, or even dark-green, it is because he sees them 
 so, and the old proposition of our school-days— <' things which are equal 
 to the same thing, are equal t(. each other"— comes back to us. The 
 difference between the green and red is, to him, simply the difterence 
 between a light and a dark-brown. If you think that is enough for 
 your signal-lights, our errand here has been a fruitless one 
 
 or