The system employed by this department _was_ a defective one, and we know of many instances in which candidates have passed the colour test, though they ought to have been rejected, and are at present in the service. The subject of testing for colour vision was brought prominently forward some two or three years ago, and a Committee of the Royal Society, to which I acted as secretary, was requested to consider the methods at that time in force on the railways and in the mercantile marine, and to find one which was not open to objection. It recommended the system that had been elaborated by Holmgren, a Swedish physicist, and known as Holmgren’s test, which has long been in force in Sweden and elsewhere. This system has, I am glad to say, been adopted by the Board of Trade, and by most of the railway companies in the United Kingdom. There have been numerous indications that this change of method was necessary. Only within the last month (April, 1894), for instance, I was informed by the Medical Officer who had to examine the employés on a certain railway in Scotland by the Holmgren test that he had found some, amongst others an engine-driver, who were colour blind, and presumably unfit for the posts they occupied owing to this defect. There is one popular objection which is always made against this test, or indeed against any proper test, viz., that the examination is not made under the same conditions which absolutely exist, nor with the very lights which the candidates have to distinguish from one another--that is, the red and green lights. Let me beg of you to remark, that as a mere matter of guessing, the chances are equal that a man would name the light shown correctly. If you turn a man’s back to the light, and if he has a coin in his pocket and deliberately calls heads red and tails green, he will have a good chance of passing the test; for, if he guessed rightly three or four times, no one would fail to pass him on his answers. The great point in a test is to cause the candidate to _do something_ to show that he appreciates colour. It is this _doing something_ and saying nothing which is the important feature in the Holmgren test. A man may be ignorant of the names of colours--colour ignorant it is called--but he cannot be ignorant of the colours themselves if he has normal colour vision. As a matter of fact, the colour blind may possibly distinguish between red and green lights by having carefully noted, under ordinary conditions of atmosphere, their different brightness, and by their difference in saturation with their neutral colour. If external conditions are altered, as they are in actual daily life, these slight indications vanish, and the quick naming of the colour to be read becomes a mere matter of chance. A proper test should include all variations that can occur in these respects. It cannot be too strongly impressed upon every one that a man who is colour blind to colours in ordinary daylight is