Aug. 2.] THE NEW ZEALAND GAZETTE. 3083

appear of the same colour as one which the Examiner selects. The most suitable objects and at the same time the most readily obtainable are skeins of wool, which can be procured of almost every desired hue and tone. An advantage of skeins of wool, besides their portability, is that, owing to their want of gloss, they appear of approximately the same tone from whichever side they are viewed. The colours of the skeins to be selected include reds, oranges, yellows, yellowish-greens, pure greens, blue-greens, blues, violets, purples, pinks, browns, and greys. Several shades of each colour, with at least five graduations of each tint, are provided, from the deepest to the lightest greens and greys. Varieties of pinks, blues, and violets, and of light grey, together with shades of brown, yellow, red, and pink, are well represented. The test-skeins with which the examinees are to compare the other skeins are five in number—(1) a light green, (2) a pink, (3) a bright red, (4) a purple, and (5) a yellow. These five colours will suffice to indicate approximately the amount and kind of colour-blindness which may exist. The light-green skein, which is a tolerably pure green mixed with a large proportion of white, is chosen as the colour which closely matches the spectrum colour which the red and green blind distinguish as white or grey. It is chosen of a pale tint, as it then becomes puzzling to the colour-blind to distinguish its colour by luminosity. A light-grey or drab skein will represent the same brightness to him that this pale colour does, and, although he may be trained to distinguish bright colours by their relative luminosities, in the case of these pale varieties he will be unable to do so. The pink is chosen for similar reasons, and, in fact, it is nearly a complementary colour to the green. The pink is, according to the Young-Helmholtz theory, a mixture of two fundamental colours, the blue and the red, and as in the green blind it excites both the blue and red sensations it may be confused with grey, or with a green. In the red colour-blind it excites in excess the blue sensations mixed with what they call white. A blue or violet may therefore be matched with it.

The method of examination is as follows:—

Method of Examination and Diagnosis.

The wools are placed in a heap on a large table covered by a white cloth or white paper, and in broad daylight. The first test-skein is taken from the pile, and laid far enough away from the others not to be confounded with them during the examination. The person examined is requested to look carefully at the test-skein and then to select other skeins from the pile most nearly resembling it in colour, and to place them by the side of the sample. At the outset it is necessary that he should thoroughly understand that he is required to search the heap for the skeins which make an impression on his chromatic sense or sense of colour, similar to that made by the test-skein, and quite independently of any name he may give the colour. The Examiner should explain that resemblance in every respect is not necessary; that there are no two specimens exactly alike; that the only question is the resemblance of the colour; and that, consequently, the candidate must endeavour to find something similar in shade and something lighter and something darker of the same colour.

If the person examined cannot succeed in understanding this by a verbal explanation, resort must be had to action. The Examiner should himself pick out the skeins, thereby showing in a practical manner what is meant by a shade, and then restore the whole to the pile, except the sample skein. This should always be done before a candidate is reported as failed.

As it would require too much time to examine every individual in this way, it is advisable, when examining large numbers, to instruct them all at once, and to ask them to attentively observe the examination of those preceding them so as to become more familiar themselves with the process. This saves time, and there is no loss of security, for no one with a defective chromatic sense will be able to find the correct skeins in the heap the more easily from having a moment before seen others looking for and arranging them. He will make the same characteristic mistakes; but the normal observer, on the other hand, will generally accomplish his task much better and more quickly after having seen how it has to be done.

The coloured plate shows the test-colours—that is, those which the Examiner presents to the persons examined.

As to the similarity between the confusion-colours and the wools which the colour-blind take from the heap, reliance must be placed simply on the hue, and not their brightness or degree of colour-saturation.

We can now pass directly to the test itself. The following are the directions for conducting it, and for making a diagnosis of the results:—

TEST I.—The green test-skein, which is labelled Test No. I in the bundle, is placed before the candidate. This sample is the palest shade (the lightest) of very pure green, which is neither a yellow-green nor a blue-green to the normal eye, but fairly intermediate between the two, or at least not verging upon yellowish-green.

Rule.—The examination must continue until the examinee has placed near the test-skein all or nearly all the skeins of the same colour, or else, with these or separately, one or more incorrect skeins, or until he has sufficiently proved that he can easily and unerringly distinguish the correct colours, or else has given unmistakable proof of a difficulty in accomplishing it.

Diagnosis.—An examinee who places with the test-skein “incorrect colours”—that is to say, who thinks that they resemble the “test-colour”—is colour-blind, whilst if he evinces a manifest disposition to do so, though he does not absolutely do so, he has a feeble chromatic sense or sense of colour.

TEST II.—The pink skein, which is labelled No. II, is placed before the candidate. The colour is midway between the lightest and darkest. It only approaches that given as II of the plate, as the colour of the wool is much more brilliant and saturated, and bluer.

Rule.—The trial must be continued until the examinee has placed all or the greater part of the skeins of the same colour near the test-skein, or else, together or separately, several incorrect skeins. If he is colour-blind he will probably select either the light or deep shades of blue and violet, especially the deep, or the light or deep shades of one kind of green or grey inclining to blue.

TEST III.—The red skein labelled No. III is placed before the candidate. It is necessary to have a vivid red colour, like the red flag used as signals on railways. The colour should be that of III of the plate, rather towards yellowish-red.

Rule.—This test should be continued until the person examined has placed beside the test-skein the greater part of the skeins belonging to this hue, or else several “incorrect skeins.”

TEST IV.—The purple skein labelled No. IV is placed before the candidate.

Rule.—This test should be continued until the person examined has placed beside the test-skein all or nearly all of the skeins belonging to that colour, or else several incorrect skeins. If he is colour-blind he will most probably select any shade of blue or green, also pinks and greys.

TEST V.—The yellow skein labelled No. V is placed before the candidate.

Rule.—This test should be continued until the person examined has placed beside the test-skein all or nearly