People often grow to like best that to which they are accustomed. A lady, who had spent most of her life on the borders of that brown Channel, once assured me that she infinitely preferred it to the “deep blue sea.” She had been to stay by the latter, and had found its monotony of tint so uninteresting that she was charmed to get back to her old friend. Tastes differ, certainly. Not many would agree with her. Yet it is a fact that the great Turner went to the Bristol Channel, with all its mud, for many of his marvellous sea and cloud effects. “Deeply, darkly, beautifully blue,” sang Byron of the ocean, and he sang truly, even though the ocean itself, putting aside the Bristol Channel, is not always and uniformly azure. Near land the tint is often greenish. Sometimes it is pure green. Often it is a pale and watery blue. At other times we have a leaden grey. The genuine ocean-blue, which resembles nothing else on Earth, can seldom be enjoyed till one gets on really deep water, far from land. Or--till one is looking at the Mediterranean. Why should the sea be blue? And why should the sky be blue? For the matter of that, why should anything be blue? What do we mean by colour?--whether blue or green, red or yellow? We mean that particular tint--or sensation--which the object in question causes us to see--or feel. The object receives sunlight, and reflects it to our eyes. And since sunlight is white or yellowish-white, one might expect that everything we look upon would appear to us white or yellowish-white. But everything does not. And the reason is that a ray of sunlight is really a bundle of lesser rays, each of which has its own colour. If a ray of light is made to pass through a prism, these lesser sub-rays are spread out upon wall or floor, always in the same order, from violet at one end to red at the other end. Light is believed to be due to enormous numbers of most minute wavelets; and for each colour the wavelets have a definite but different size. They are smallest at the violet end, and largest at the red end. Now when a ray of sunlight falls upon anything--leaf or flower, earth or water--some of the sub-rays are absorbed or taken in, and some are rejected or refused admission. A healthy leaf, for instance, absorbs the red, the yellow, the blue, the violet, and refuses the green, which is therefore thrown back from the leaf-surface to our eyes, making it green to us. A ripe tomato absorbs the yellow and green, the blue and violet, and reflects the red. A lump of blacklead absorbs greedily all the rays, reflecting none, and so to our eyes it is black or without colour. The petals of a white rose, on the contrary, absorb so little colour of any kind, that practically the entire ray is sent again to us as white light. If this is the manner in which the ocean is blue, it means that sea-water, and indeed water generally, must in itself be actually blue, as a cake of ultramarine, a sapphire, a corn-flower, a forget-me-not, are blue.