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.