Page:The wonders of optics (1869).djvu/94

86 its companions. Violet, being at the top, is of course the most refrangible. The cause of the separation of the colours of white light is consequently only the effect of their individual character. They were, so to speak, so many streams flowing together until an unexpected deviation in their course caused them to separate. This change in the direction of their flow brought out their personal individuality, and they at once became completely disunited.

Every single tint in the prismatic spectrum is simple, and cannot be decomposed. This may be shown by passing any of them through another prism, when it will be found that no change will take place in the colour or size of the pencil. Hence those worlds already spoken of, whose light of day is red, blue, or green, never see any colours but these. (Fig. 6, Frontispiece).

It is just as easy to reunite the colours into which white light is decomposed, by applying a second prism in a reversed position to the pencil of coloured light, as it is to separate them in the first instance. The method of accomplishing this is shown in fig. 7, Frontispiece.



Another experiment in the same direction consists in