=The Applications of Colour to the Work of Everyday Life= are so universal that a complete list is almost impossible, though some of the most important are mentioned below. In a general way the visual characteristics of every visible object are determined by contrasts of light and colour, outline itself being governed by differences of light intensity. In Nature, colour is practically universal. There are few objects perfectly white. Most of them have colour of greater or less complexity; even snow under a cloudless sky has a blue tint which is measurable against such white objects as pure lime sulphate, zinc white, etc., the blue tint being manifestly reflected from the cloudless sky, as it disappears under a cloudy overcast. =Some of the Scientific Applications of Colour.=--It associates colour sensations with definite names and values; discovers and classifies cases of colour-blindness, and is a preparation for the physical study of light. It is also essential for studying the physiological structure of the organs of vision, for disclosing abnormal conditions of the blood, and for measuring the colour of the hair and skin for the anthropological classification of races. It is used in general laboratory work for analytical and original investigation; and it furnishes standards of value for the petroleum industry, the International Tanning Association, the inter-States Cotton Seed Oil Association, etc. It is also one of the principal factors in all artistic industries; for, besides having an important educational value in questions of harmony, contrast, and taste, it is of direct commercial value in such industries as dyeing, calico printing, all woollen industries, wall-paper printing, paint making, house decoration, etc. =General Instructions for Using the Apparatus.=--The apparatus consists of a frame having six little windows, fitted with sliding shutters, and a tray containing eighteen standardized glasses. The frame must be placed on a table or stand facing the children, with a window or some other source of diffused white light behind it. Care must be taken not to have a coloured background of any kind. The glasses are in three colours, Red, Yellow, and Blue, of different depths. The depth of colour is marked in figures on each glass, and corresponding numbers in the three colours are of equal intensity. It is of importance that the six spectrum colour terms should be the only ones used in the preliminary stages. The first step in colour teaching must be to develop and train the perceptive faculties of the children so as to enable them to express in words the colour sensations which are excited. For this purpose it is necessary to begin by demonstrating that the six spectrum colours Red, Orange, Yellow, Green, Blue, and Violet, are derived from white light.