In this way he will have no clue to the colours which are being shown him. _Objections to other tests for colour-blindness._--The tests which have been proposed for colour-blindness are very numerous, but some are so defective that it is rare to detect a single colour-blind person with them. I have, for instance, tested men whom I knew to be colour-blind with certain lanterns with the result that not a single one was detected. In these so-called tests all the requirements of a test and facts of colour-blindness have been neglected. I must, however, refer to three tests constructed by exceptionally able men, each with considerable knowledge of the subject. I refer to the tests of Professor Holmgren, Professor Stilling, and Professor Nagel. All these tests can be passed at the first attempt without coaching by certain dangerously colour-blind persons, chiefly varieties not known to the inventors, but the chief defect of each is that it is very easy to coach a colour-blind person to pass it. The surgeon to one of our largest railway companies told me that when they used Holmgren’s test they rejected one man in three hundred, but with my lantern twelve in the same number. All these three tests are much better tests when the persons to be examined have not seen them before. A colour-blind man may make only one mistake, say for instance, as in a case I examined the other day, with Nagel’s test (last edition), he passes the test perfectly with the exception of one mistake, that of calling a grey on one card, green. All he has to do is to look for some distinguishing mark on this card in order to go through the test with the ease and certainty of a normal-sighted person. It is the same with Stilling’s letters, he has only to note the letter which he was not able to read and the appearance of the card. A normal-sighted man or woman would readily help him. The confusion of green and grey does not appeal to the average man as a serious defect, especially when he sees his friend go through the rest of the test perfectly. He says to himself, “I suppose he sees a tinge of green in that grey.” The same man would rightly regard it as a most iniquitous proceeding to endeavour to coach his friend through a test when he had seen him mistake a red for a green light. Holmgren’s test rejects a large number of normal-sighted persons, as may be seen by the reports of the Board of Trade; about 50 per cent of those who appeal are found to be normal-sighted and to have been rejected wrongly. WILLIAM BRENDON AND SON, LTD. PRINTERS, PLYMOUTH Reiner and Keeler, L^{td.} OPTICIANS ----AND---- INSTRUMENT MAKERS _MANUFACTURERS OF_ The Edridge-Green Colour Perception Lantern The Edridge-Green Classification Test The Edridge-Green Pocket Test and other Optical and Scientific Instruments THE ABOVE COLOUR TESTS ARE CERTIFIED BY PROF. F. W. EDRIDGE-GREEN 9 Vere Street, Cavendish Square, =London, W.= Telephone: 447 Mayfair.