We have hitherto considered light chiefly as a simple homogeneous substance, as if all its rays were white, and as if they were all refracted in the same manner by the different lenses on which they fall. Investigations however, into the nature of this wonderful fluid, have demonstrated that this is not the case, and that it is possessed of certain additional properties, of the utmost importance in the system of nature. Had every ray of light been a pure white, and incapable of being separated into any other colours, the scene of the universe would have exhibited a very different aspect from what we now behold. One uniform hue would have appeared over the whole face of nature, and one object could scarcely have been distinguished from another. The different shades of verdure which now diversify every landscape, the brilliant colouring of the flowery fields, and almost all the beauties and sublimities which adorn this lower creation would have been withdrawn. But it is now ascertained that every ray of white light is composed of an assemblage of colours, whence proceed that infinite variety of shade and colour with which the whole of our terrestrial habitation is arrayed. Those colours are found not to be in the objects themselves, but in the rays of light which fall upon them, without which they would either be invisible, or wear an uniform aspect. In reference to this point, Goldsmith has well observed: ‘The blushing beauties of the rose, the modest blue of the violet, are not in the flowers themselves, but in the light that adorns them. Odour, softness, and beauty of figure are their own; but it is light alone that dresses them up in those robes which shame the monarch’s glory.’