An examiner should, as far as possible, with the exceptions given in the instructions, avoid all conversation with the candidate, simply asking, “What colour is this?” and recording the answer without comment. If an examiner after each answer say, “Quite right,” or some such expression, the following is likely to occur. The candidate after, say, six correct answers, makes a mistake; the examiner says, “Are you sure?” Then the candidate knows at once that he has made a mistake, and makes a guess, very probably a correct one. When a similar colour is shown subsequently, he remembers the mistake he made, and gives the second, and probably the correct answer. In addition to being an efficient test, it is a very rapid test, as many men who have been certified as normal after a lengthy examination with other tests have at once disclosed their defect by calling the green light of the lantern red. Many are under the impression that in an examination with the lantern the dichromics simply guess. This is entirely wrong. A man who did guess would know that he was incompetent. I find that men have named the coloured lights in strict accordance with their colour-perception. A man may, however, guess if examined by an inexperienced and ignorant examiner, who when the examinee has made a mistake promptly corrects it in a cross tone. A normal-sighted person will guess when examined in this way. The examiner must receive the examinee with a smiling face and courteous manner, and appear pleased and satisfied with the answers, no matter what they may be. The candidate is then placed at his ease, and answers according to his colour-perception. It will be noticed that the lantern detects those who have a slightly diminished colour-perception, as well as the dangerous varieties of colour-blindness. The former undoubtedly are not as efficient as those who have a normal colour-perception, so that a definite standard will have to be fixed, as in the case of visual acuity. Further details will be found in my book on Colour-Blindness.[12] [12] _International Scientific Series._ Kegan Paul & Co., 1909. _Summary of method of examination._--(1) Show all the colours on one disc with the largest aperture. (2) Show the reds, greens, and yellow modified by the neutral glasses. (3) Show all the colours on one disc with Number 3 aperture. (4) Show red, then immediately afterwards yellow with largest aperture. Then show green and yellow immediately afterwards. (5) Test the candidate with the red, green, and yellow with the smallest aperture. (6) Show the neutrals or ground glass alone. (7) Show blue made by combining blue or purple with the signal green. (8) Show a colour, for instance, green, and then combine another glass of the same colour. (9) Show the red produced by the combination of purple with red A. (10) Give the combination of red A and signal green.