The mighty deep

NOT that the Ocean is always and everywhere blue. In a certain “arm of the sea,” the Bristol Channel, it is commonly any tint that you please rather than blue—brown, green, yellow, chocolate, only not the colour that we love. If by chance it dons for a few hours a robe of azure, that robe is merely a passing loan from the sky. And in dull weather it can only be described as a huge puddle of muddy liquid.

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.

Could that be the case? For a long while men decisively answered—No. Everybody knew that water was colourless, so the idea was flung aside as impossible. Another explanation came up instead.

The sea is full of fine dust; and it was suggested that, as vast multitudes of these floating dust-particles are exceedingly small, they might be able to reflect only the smaller blue light-waves, and not the larger yellow or the still larger red waves. Thus the sea would naturally seem to be blue.

After much discussion, careful experiments were made. Different objects were lowered to various depths, and the effect upon their colouring was noted. The outcome of these and other tests went far to prove that the old certainty was wrong, and that water is in itself blue.

Somebody may feel inclined to protest. “Water blue! But that is out of the question. I have good sight, and I assure you there isn’t the least sign of colour in water. Not the faintest. If you dip a bucket in the sea, you will see for yourself.”

Yet all the while the colour may be there, actually existent, though not to be detected by your eyes or mine in a pailful.

A short time ago I had to buy a piece of lace; and my intention was to choose a pale straw or deep cream. The lace was wound in many folds round a large cardboard, and it seemed to be exactly the right hue—a rich yellow-cream, almost butter colour. Without further demur, I ordered about a yard to be cut off.

On reaching home, I found myself in possession of a piece of wide dead-white lace—or all but dead-white. It was actually a very pale cream; and when a great many folds lay one over another the combined effect was rich and yellow. But a single thickness of the material showed no colouring.

The same may be seen with a single piece of very pale blue muslin. It will appear to be white. But yards upon yards of the same, folded together, will become quite a deep blue.

A single thin layer of ocean-water, in like manner, has too faint a hue to be visible to ordinary eyesight. It is only when layers are piled upon layers that the blue becomes distinct; and the deeper the water, the deeper generally will be the colour. Some yards of water-thickness may be said to correspond to a single thickness of lace or muslin.

While, however, we may say with tolerable confidence that the blue of the ocean is a “True Blue,” this alone will not explain all the varieties of tinting, seen at different times and in different places.

Sea-water is sometimes a rich profound blue, and sometimes a pale sickly blue. It is sometimes dull, sometimes brilliant. It is sometimes green, and sometimes almost black. For these variations, even while accepting the new explanation, it has been found needful to revert to the old theory in quest of added help. The sea is blue, because it really and truly is blue. But that is not all. It is a deeper or less deep blue, a duller or brighter blue, a greenish blue or even a dull yellow, because of the vast supplies of dust floating in it.

The Mediterranean was particularly examined, on account of its remarkable depth and brilliancy of colouring; and it was found to be exceptionally laden with dust, both fine and coarse, brought from land by innumerable rivers, and also pounded by breaking waves on the long surrounding coast-lines.

Such floating particles, at all events the bigger ones, are no longer supposed, as once they were, to reflect only the tiny blue light-waves. On the contrary, they are believed to reflect all the waves of light indiscriminately, whether large or small; while the sea, by virtue of its own power as a Blue material, captures all those reflected waves except the blue, and allows the latter alone to reach our eyes.

Near British shores the water has often a strongly green tint; and this may be due in part to floating particles of sand. The yellow of the sand, combining with the blue of the water, would naturally form green. Possibly also the sea, near shore, is sometimes affected in colour by floating sea-weeds, green-tinted.

The blue of the sky is often reflected on the sea-surface, and sometimes so powerfully as to overcome the real ocean-colour. One hardly understands how intense such a sky-reflection may be, until one has watched the whole sea transformed into glowing crimson or gold from a radiant sunset.

Much the same perplexity has been felt about the blue colour of air, as about the blue colour of the ocean; and much the same course of explanation has been followed. Its blueness was long maintained to be due only or mainly to the “scattering of sunlight” by infinite numbers of floating dust-specks, which also serve to account for the golden and crimson tints of sunset. It now appears that oxygen, an important element in the atmosphere, has a faint blue tint of its own, like water, which at least helps to answer for the blue of the air.

We may therefore say of Water that it is believed to be transparently and intrinsically blue; and that its colour, though not actually due to floating specks of dust and other impurities, is a good deal affected by them. Such materials in the Ocean help to modify its colouring, sometimes deepening it, sometimes adding to its brilliance, sometimes deadening its brightness, sometimes turning it green or yellow. Careful observation has also shown that, when water is especially free from dust-specks, it is of a darker and duller hue than when they are present in large quantities to capture and reflect the sunbeams.