Colour Blindness

R. Brudenell Carter
1892 Royal United Services Institution Journal  
in the Chair. COLOUR I3LINDNESS. 139 R. I~RUDESELL CARTER, Esq. NR. CHAIRMAS, It has long bccn known to thosc cngagcd in tho pursuit of natural pliilosophy, and, to' somo cxtcnt, also to the gcncml public, that a certain number of pcrsons arc so or anized as to recci\-c sensations of tlic great bulk of tho community. Tho pcrsons so nffcctcd havo bccn described, not vcry accumtcly, as " colour blind f and, until latcly, need only remind you that d i n t wc call the scnsation of d i t o light,
more » ... ch as that of tho sun or of the elcctric arc. is not only produced by colour wliich differ, either in comp Y etencss or in kind, from thosc of Downloaded by [McGill University Library] at 14:04 19 March 2015 984 COLOUR BLINDSESS. tho impact upon the retina, or nemous expansion within the eye, of a rapid succcssion of waves of the luminifcrous cthcr, but also that these waves must be of many different magnitudes, so ns to afford a blcnding together of many different amplitudes of vibration. Whcn a bcam of such whito light is snffercd to enter a dark chamber, it can bo analysed, so to speak, by tho interposition of n prism ; with tho effect that it will not only bo compelled to deviate &s a wholo from its original straight courso, but that the deviation will be much grcntcr for small and rapid waves than for largo and slow ones. A beam of whito light, originally circular in outline, will be thus cstcndcd into a horizontal band, in which tho lmgest wa-ics will be a t one cnd of tho band, and tho smallcst at thc other, whilo tho intervening magnitudes will bo eredy distributed between tho ends in the order of their rcspcctivo sizcs. There will bo a regular gradation of ware magnitude, from tho end of thc band which is least deflected from its original course, to that which is most dcflcctcd. (Prismatic spectrum shown.) The different parts of the band thus produced will differ not only in wave magnitudc, but also, and very conspicuously, in colonr. Tho band will no longer bo white, but brilliantly parti-coloured. A t the end whcrc it is least dcflcctcd, and whero the largest warts fall, it is said to bo red. A t the end where yt is most deflected, and wheru tho smallest waves fall, it ia said to bo .dolet. I n the intermcdiotc portionfi it presents tho well-known succcssion of the prismatic colours, in which, according to Nowton, red is followed by orange, yellow, grecn, blue, and indigo, the la& passing into xiolct. When we come to inquire into tho nature of these rery striking and beautiful phcnomeua, wo find that certain colour sensationa are results of the impact upon the retina of vibrat,ionR of uniform wave lcngth, while others are results of tho impact of mixtures of diffcrcnt TTILVU lengths, mixtures lcss complicated than that which produces tho scnsation of whito light, but still com licated when compared with the uniform magnitude of vibration wkch impresses tlic conscionsness with ono of tho primary or*nnmingled colonr sensations. It seems to bo determined by espciimcnt that .the primary sensations are threo in number-red, grecn, and bluc ; and that each one of these, when of a certain hue and.purity, is,produced by the impact of waves of a single magnitude. When the simplo character of these thrco primarics was firat asccrtaincd, thcy wore dcscribcd. aa rcd, green, and violet; b u t your own experiments, Sir, appear to have cstablished that the sensation of violct is duo to the dilution of spectral bluo with white light; and, hence, ,to speak of tho primary itself a8 "bluc" seems to bo tho moro corrcct nornenclaturc. All the inkrmcdiato portions of tho spectrum are admixtures mom or lcse complicated ; an2 ?lot only so, but. every colonr which wo recognizo in the universe in an admistnrc of one, two, or all of tho threo primaries, in varxing proportions, and with more or leas white light. This fact, long known hypothetically, has received exyrimcntal proof at the hands of our Chairmen, who has succeeded, by combining selected portions of the spcctrnm with whito light, in matching the
doi:10.1080/03071849209417720 fatcat:b52jsfcggbchjjyuxzh6kj5msa