table absorbs all the rays but the green, which it reflects to the eye: but your coat is of a different texture, and absorbs all but the blue rays.. Charles. Why is paper and the snow white? Tutor. The whiteness of paper is occasioned by its reflecting the greatest part of all the rays that fall upon it. And every flake of snow being an assemblage of frozen globules of water sticking together, reflects and refracts the light that falls upon it in all directions so as to mix it very intimately, and produce a white image on the eye. James. Does the whiteness of the sun's light arise from a mixture of all the primary colours? Tutor. It does, as may be easily proved by an experiment, for if any of the seven colours be intercepted at the lens, the image in a great measure loses its whiteness. With the prism I will divide the ray into its seven colours*, I will then take a convex lens in order to re-unite them into a single ray, which will exhibit a round image of a shining white; but if only five or six of these rays be taken with the lens, it will produce a dusky white. Charles. And yet to this white colour of the sun we are indebted for all the fine colours exhibited in nature: * A figure will be given on this subject with explanations, Conversation XVIII. on the Rainbow. Fairest of beings! first created light! Prime cause of beauty! for from thee alone, The sparkling gem, the vegetable race, The nobler worlds that live and breathe, their charms, The lovely hues peculiar to each tribe, MALLET. Tutor. These are very appropriate lines, for without light the diamond would lose all its beauty. James. The diamond, I know, owes its brilliancy to the power of reflecting almost all the rays of light that fall on it but are vegetable and animal tribes equally indebted to it? Tutor. What does the gardener do to make his endive and lettuces white? Charles. He ties them up. Tutor. That is, he shuts out the light, and by this means they become blanched. I could produce you a thousand instances to show, not only that the colour, but even the existence of vegetables, depend upon light. Close wooded trees have only leaves on the outside, such is the cedar in the garden. Look up the inside of a yew tree, and you will see that the inner branches are almost, or altogether barren of leaves. niums and other green-house plants turn their flowers to the light; and plants in genera 1, ifdoomed to darkness, soon sicken and die. Gera James. There are some flowers, the petals of which are, in different parts, of different colours, how do you account for this? Tutor. The flower of the heartsease is of this kind, and if examined with a good microscope, it will be. found that the texture of the blue and yellow parts is very different. The texture of the leaves of the white and red rose is also different. Clouds also which are so various in their colours are undoubtedly more or less dense, as well as being differently placed with regard to the eye of the spectator; but the whole depends on the light of the sun for their beauty, to which the poet refers: But see, the flush'd horizon flames intense With vivid red, in rich profusion stream'd O'er heaven's pure arch. At once the clouds assume Their gayest liveries; these with silvery beams |