If a candidate hesitate about a colour and ultimately name it correctly, a second and, if necessary, a third glass of the same colour should be combined with the first. The fact that in one case a single glass is used, and in another two or three of the same coloured glass, makes very little difference in the colour of the light to the normal-sighted. This is not the case with the colour-blind; a dichromic who has hesitated about a green and then correctly named it may emphatically call the light red when another green glass is put in front of the first. Care must be taken when the candidate is going to be examined with two glasses at once, such as one of the neutral, ground, or ribbed glasses, and a coloured glass, that he does not see the light until both are in position, or else he may see the colour before it is modified in the necessary way. If the candidate call the standard red, green; or the standard green, red, in any circumstances--that is, either alone or in combination with the modifying glasses--he is to be rejected. The examiner should ascertain for himself how far the various colours are visible when modified with the neutral glasses. If the red and green be not visible with the thickest neutral in the conditions of luminosity and external lighting which the examiner is employing, he should use the darkest neutral which allows the colours to be plainly visible to the normal-sighted. In all cases of doubt the examinee should be asked to walk towards the lantern and told to say when the light is visible, and asked to name its colour. The distance at which the light is visible, and then that at which the colour is visible, should be noted and compared with the normal. Particular attention should be paid to the answers given to the combination of the thickest neutral glass with the standard red and green respectively. The examiner should utilise the fact that successive contrast is increased in the colour-blind, as this is an easy method of detecting the trichromics. The red having been shown, the light should be quickly changed to yellow or clear, the examiner’s hand being placed over the aperture if there be any intervening colours. It is necessary that the yellow should be shown immediately after the red without any intervening colours being first seen by the candidate. The normal-sighted do not see any change in the yellow or clear when they are shown after the red light, but the trichromic call the yellow light, green. The examinee should then be shown the green light, and then the yellow or clear, in the same way as mentioned for the red. The normal-sighted will easily recognise the yellow, but the trichromic will call it red. This portion of the examination must never be omitted in any examination in which the candidate is passed. The two divisions of the test--that is, showing yellow immediately after red and after green--may be used at different periods of the examination, and, if there be any doubt, repeated.