412 
Testing for Colour-blindness. [July, 
and “ starboard ” lights of a ship, and these are used in a 
darkened room, a lamp being placed behind them. . The 
testing by coloured glasses follows that of cards or skeins of 
wool, special attention being paid to the candidate s ability 
to distinguish the red from the green glass. Ihe examina- 
tion on the whole is made with a view of determining 
whether a candidate can distinguish signals by day,— as 
flags, which are composed of many colours, — and next 
whether he can distinguish signals by night, — the lamps 
carried by ships, which are either red, green, or white. If, 
therefore, a man can distinguish red from green, and both 
from white or black, the examiner considers that he will be 
able to follow the International Rules for the prevention of 
collisions at sea. This method of testing has,. we are told, 
been found sufficient for the purpose for which it is applied, 
“ that purpose being not to discover and record the pecu- 
liarities of sight of the applicant, nor his powers of detecting 
and arranging all colours and tints, but to test his ability to 
name a common well-known colour when it is placed before 
him.” 
Candidates can hardly be expeCLed to complain of the easy- 
going method sanctioned by the Board of Trade. Never- 
theless it will occur to members of the medical profession 
that it is capable of a good deal of improvement. First, to 
be thoroughly effective the examination should undoubtedly 
be made more practical,— that is, quite in accord with the 
conditions under which the recognition of coloured signals 
at sea will usually take place. Second, the examiners 
should, for obvious reasons, be trained men, well acquainted 
with the subject, and not retired ship-captains. With ex- 
aminations more intelligently conducted than at present, it 
could hardly happen that so large a proportion of the 
candidates who on their first examination called green red, 
and red green, would upon re-examination obtain certifi- 
C^tCSi 
The Board of Trade, however, with every desire to do its 
best, in 1881 endeavoured to ascertain the practice adopted 
by other nations, and a circular was issued to the principal 
powers of Europe, as well as to America. From the answers 
we gather that a colour-test has been in use in the United 
States for some years. In the case of pilots applying for the 
renewal of their licenses, or of applicants for original licenses 
as pilots on steam-vessels, examination is compulsory, and 
since 1880 a voluntary examination for all persons serving 
in the Mercantile. Marine, as to physical fitness and ability 
to distinguish colour, has existed. 
