August i8, 1910] 



NATURE 



209 



There are two main lines of cleavage between rival 

 schools of testinfj. One insists upon the matching 

 of colours, the other on the necessity for naming 

 colours. The first is official and based upon Holm- 

 gren's tests. A candidate is given a skein of coloured 

 wool, and required to pick out from a heap of skeins 

 other wools that, in his opinion, match the wool 

 given him. The second method of testing is per- 

 formed by exhibiting a colour in wool, card, or pre- 

 ferablv by means of light from a distant lantern, and 

 the candidate is required to name the colour shown 

 in whatever language he knows. The colour is ex- 

 hibited detached from any other colour that could 

 give external help, the man must judge of the ex- 

 posed colour alone and unaided, and name it in 

 common terms. Now each of these modes of colour 

 perception are common habits with us in our daily 

 life. We constantly match colour, consciously or un- 

 consciously, and we as often, perhaps more often, 

 name colours we see, matching them mentally and 

 naming them according to a standard we have learned 

 by experience. On the respective merits of these 

 methods, the rival schools clash, and, so far as can 

 be judged, the disagreement rests upon theoretic 

 conclusions rather than practical experience. 



If we consider these two tests in relation to actual 

 life, or, at any rate, the life of a seaman, it can 

 scarcely be denied that the second non-official test, 

 naming the colour, is the one that most nearly tallies 

 with his experience. The seaman is required to pick 

 up a light, most likely a solitary light, and judge 

 of its colour without possible comparison ; he must 

 rely on his judgment of that light in relation to the 

 mental impressions that are part and parcel of his 

 cerebration, and the impression he receives is in- 

 stantly and unconsciously correlated with a name, the 

 name of a colour in the language in which his mind 

 works. To name is second nature. What the name 

 may be matters not, so long as it be current coin ; 

 the "B" line in the spectrum may be "red" to us 

 or "blood-colour" to the savage, and "F" "blue" to 

 us and " sea-colour " to the savage : the intention is 

 the same. 



But it is argued by the adherents of the Holmgren 

 test that the matching of colour is more likely to be 

 I rue, for it eliminates possible errors due to ignorance 

 in precise nomenclature, e.g., three people may see 

 the same colour and variously describe it as purple 

 or mauve or heliotrope, with a result that a fourth 

 might not be sure what colour was meant, yet each 

 of the three would find no difficulty in matching the 

 colour correctlv, particularly if they were women who 

 took an interest in their dress. 



The good and bad of these tests can only be put 

 to proof when thev are tried on known colour-blind 

 persons. Then it has been found that persons can 

 successfully match colours who grossly misname 

 them when the colours are shown singly. On the 

 other hand, there are some who can name colours 

 who fail to match well. The evidence of the cases, 

 particularlv those of the first and more important 

 group, has been sifted and is established. Which, 

 then, of these two persons is the colour blind, he 

 who can match but not name or he who can name 

 but not match? The solution of this perplexity is 

 as follows : Matching depends rather on a keen 

 sense of light and shade than on colour sense ; 

 colour-blind persons can be educated up to the match- 

 ing test, but never to acquire a colour sense thev 

 do not possess. Those who name colour accurately 

 yet fail to match are bunglers, folk just ignorant of 

 what matching means; the maid-of-all-work will 

 know, but a vouth or a seaman may not. 



NO. 2129, VOL. 84] 



On the mode of applications of tests, if a little 

 pleasantry be permitted, it can scarcely be denied 

 that in some aspects the official methods are as fine 

 a joke as could well be devised. What would a 

 stranger visitant think of these heaps of coloured 

 wools? Surely he would commend a State 

 whose paternal care extended to the examina- 

 tion of young ladies desiring employment in 

 haberdashery shops, to the end that they may 

 be good at matching their customers' patterns ! 

 That these wools were to test the seaman's ability to 

 pick up lights in rain and shine, storm and fog, our 

 visitant would surely find unthinkable. And yet it is 

 so. So far has theory divorced from experiment 

 carried us. If it be well to let the punishment fit 

 the crime, how much more should the test of. a quality 

 fit the usage of that quality. It seems obvious that 

 the ability to see lights and signal flags should be 

 tested with lights and flags. That this is now recog- 

 nised is shown by the number of testing lanterns that 

 have been fathered since Edridge Green directed atten- 

 tion to the matter ; but some of the lanterns are bad 

 by reason of the poor range of their tints. 



The next line of cleavage between rival schools is 

 due to differences in opinion as to what are to be 

 the crucial colours of the tests. Here theories of 

 colour vision come in inost emphatically, and until 

 this problem is solved, we cannot expect agreement 

 unless there be a truce to theory and a trial by ordeal. 



There is one satisfactory mode of surmounting the 

 difficulty in the choice of crucial colours, that is, by 

 the use of the spectrum itself. Much of the experi- 

 mental work on colour vision has been done with the 

 spectroscope, and the appreciation of the value of it 

 as an everyday appliance is shown in that, within 

 the last two years, there has been devised three pieces 

 of apparatus for colour testing by direct appeal to 

 the spectrum. A verv clever projection spectroscope 

 has been devised bv Dr. J. H. Tomlinson, and valu- 

 able instruments for direct view of the spectrum by 

 Dr. Maitland Ramsey and bv Dr. Edridge Green. 

 Of these instruments, the first has the advantage 

 that both examiner and candidate can view the 

 spectrum together. But Edridge Green's instrument 

 has the germ of the right principle in colour testing, 

 for it is provided with scales which give the measure- 

 ment of the aperture of the shutters in wave-lengths, 

 so that bv this means the range of distinction of 

 colour throughout the spectrum can be measured and 

 registered. 



In conclusion, what we want is not only 

 a trustworthy mode of qualitative test, but also 

 a quantitative test — some mode whereby we 

 can express a man's colour-sense in terms as 

 stable as we can express his form-sense bv 

 Snellen's test types. .At present, opinion and fact 

 are hopelessly muddled by our inabilitv to convev 

 what our tests show. Say a man fails to distinguish 

 a certain red: he must be written down "red blind," 

 notwithstanding he can see another red. To sav he 

 is red blind is both true and false, but it is the only 

 statement that can be made in the absence of' finer 

 modes of expression. We want to take the measure 

 of his perception of the colours of the spectrum and 

 register them in simple terms. Given such an abso- 

 lute register of his colour sense, there will remain 

 only the expression of opinion as to his capability for 

 doing certain work. Reauirements will vary with the 

 work to be done. For seamen and railway men we 

 should require the highest standard, even as is 

 reaiiired of them for form vision. 



We wish the new committee a happv issue out of 

 all its troubles ! ' N. B. H. 



