Colour-blindness and colour-perception / by F. W. Edridge-Green.

  • Edridge-Green, F. W. (Frederick William), 1863-1953.
Date:
1891
Catalogue details

Licence: Public Domain Mark

Credit: Colour-blindness and colour-perception / by F. W. Edridge-Green. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    which is reflected from or transmitted by a substance. ' Without these rays a substance will not only not be coloured, but appear black. For instance, if we look at a piece of ultramarine by thfe light of burning sodium it appears black. Without light we cannot have colour, and as the light of the sun is white, it must follow that something must be added to, or subtracted from, this light j before colour can be produced. In the following chapters ; it will be shown why a certain combination of rays gives I rise to the sensation of a certain colour. In this chapter ' it only remains for. us to consider what changes in the ' series are capable of giving rise to any sensation of colour, j The following are the ways in which white light is \ altered so as to give rise to the sensation of colour. i 1. Colours produced by Dispersion.—When colours are 1 produced in this way, the white light is not altered in character. The constituent rays, on account of their ! unequal refrangibility, are spread out in the form of a ' series. This is called the dispersion of white light. The ] colours of the rainbow are good examples of colours pro- J duced by dispersion. * 2. Colours produced by Absorption.—In the case of i opaque bodies a certain number of rays of light are ab- \ sorbed, and the remainder reflected, giving rise to a sensa- j tion of colour. In the case of transparent bodies, a certain \ ny.mber of rays are absorbed, and the remainder trans- , mitted, giving rise to a sensation of colour. . | This is the commonest way in which colours are pro- * duced; the colours of flowers and pigments of all kinds * being due to this cause. When pigments are mixed the j resulting colour is that which is reflected by both pig- : ments. It is in this way that yellow and blue pigments, • when mixed, make a green. The pigments used are not I pure—that is to say, the yellow pigment reflects green as