JUNE 7.] THE NEW ZEALAND GAZETTE. 1467

All that is required is that the Examiner shall conduct the examination according to the rules laid down, and from the wools selected judge whether the candidate is or is not colour-blind, the nature of his colour-blindness being immaterial.

(10.) The result of every test should be reported to the Marine Department on the Form Exn. 2, and on Form Exn. 14 when the candidate is up for examination for a certificate of competency, and on the Form Exn. 2b when the candidate is up for examination in colours only.

All cases of failure should also be reported to the Marine Department on Form Exn. 17b, to which should be attached Form Exn. 17c, containing the pieces of the wools incorrectly selected by the candidate. (See par. 4.)

Holmgren’s Method of Testing for Colour.

The method of testing consists in asking the candidate to select from variously-coloured objects those which 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 three in number —(1) a light-green, (2) a pink or pale-purple, and (3) a bright-red. These three 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 or light-purple is chosen for similar reasons, and, in fact, it is nearly a complementary colour to the green. The purple 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:—

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 examination, 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. 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, and some of the mistakes likely to be made by colour-blind people. The colours in the plate are of two characters:—

1. The colours for samples (test-colours)—that is, those which the Examiner presents to the person examined; and

2. The “confusion-colours”—that is to say, those which the colour-blind may select as matches with the sample.

The first are shown on the plate as horizontal bands, and are distinguished by Roman numerals (I., IIa., and IIb.); the second as vertical bands under the test-colours, and are distinguished by Arabic figures (1, 2, 3, &c.).

As to the similarity between the confusion-colours of the plate 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. The confusion-colours shown in the plate are only to illustrate the mistakes which the colour-blind may make, and for this purpose they serve perfectly. Having made this explanation, we can pass directly to the test itself. The following are the directions for conducting it, and for making a diagnosis from the results:—

Test I.—The green test-skein, which is labelled Test No. I. in the bundle, is exhibited to 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 several other skeins of the same colour, or else, with these or separately, one or more skeins of the class of “confusion-colours” such as 1 to 5 in the plate, or until he has sufficiently proved that he can easily and