The ocean was the home of the first living thing, either plant or animal, that appeared on our planet; seaweeds and salt-water animals are found in much older rocks than any that contain the fossils of land life. Moreover, though called a “wide waste of waters,” and seeming a complete desert as we gaze upon its restless surface on a dull morning, there is a greater number of animals and plants by count, and quite as large a variety, under the waves as above them, and the bottom of the sea—at all events near its margin—is more populous than any bit of woods you ever saw.
There exists in our ponds and ditches a race of plants so minute that it requires a powerful microscope to examine them. Under this instrument it is seen that they have delicate, flinty shells or armor, which is of a great variety of forms,—coiled, globular, boat-shaped, spindle-like, and so on,—and always beautifully sculptured. These minute and beautiful diatoms, as they are called, move about freely, and were long supposed to be animals; now they are known to be the simplest of seaweeds, consisting of only one cell. Since life first began, these diatoms, and other microscopic plants much like them, have swarmed not only in the fresh waters, but in all the oceans of the globe, furnishing food for mollusks and all the lowly animals whose food is brought into their mouths by the currents. Innumerable, and as wide-spread as the salt water itself, every one of these myriads of minute plants has left a record; for its delicate, glass-like shell was indestructible, and when the bit of life was lost, it sank slowly down to the bottom. What effect toward perceptible sediment could come from a thing so small that it would scarcely be felt in your eye? One or two, or even a million, would go for little; but century after century, through ages too long for us to comprehend, a steady rain of these exquisitely engraved particles of flint showered down upon the still sea-floor, almost as thickly as you have seen motes in a sunbeam, until there was deposited a layer, many feet in thickness, of nothing but diatom-skeletons. Though this went on to a greater or less extent everywhere in the sea, such deposits are not now to be discovered everywhere, because disturbing causes swept the shells away, or broke up the floor after it had been laid down; but in various parts of the world to-day, you may find wide beds of rock made up wholly of such skeletons, soldered together into hard stone; while in some regions the mud of our sea-bottom appears to consist of almost nothing else. The mighty chalk cliffs of Great Britain and the French coast were built up in precisely this way at the bottom of an ancient sea, whence they have been lifted, but they are composed of much besides diatoms.
From the simplicity of diatoms the vegetation of the sea can be traced upward through larger and more complicated kinds of plants until we reach the enormous algæ that break the gloom of black headlands by their brilliant tints, and furnish a lurking-place under their wide-spreading and dense foliage for hosts of marine animals—some hiding for safety, others to watch for prey.
Seaweeds grow in all latitudes, even close to the pole, but mainly along the shore, for below the depth of about one hundred fathoms none but microscopic forms are known. These latter float about, of course, and many of them have been thought to be animals because they seem able to move at their own will. They come to the surface as well as haunt the depths; and the Red Sea takes its name from the fact that a minute carmine-tinted alga occasionally rises to the surface in throngs so dense and wide as to tinge the water for miles at a stretch. The same thing occurs in the Pacific, where the sailors call it “sea-sawdust.”
The proper home of the seaweed, however, is a rocky shore between tide-marks or just below them, and it is because the eastern coast of the United States is deficient in rocks—at least south of Cape Cod—that this is poor in algæ, compared with other regions. The seaweed has no roots, and only clings to the rock for support; shifting sand therefore would not hold it, and there are great sandy deserts under the ocean, bare of algæ, as some land regions are sandy deserts naked of terrestrial plants.
It often happens, however, that masses of weed will be torn away from their moorings and set adrift. This does not necessarily kill them, for they go on flourishing while afloat, and such is supposed to be the origin of those great areas of “gulfweed” vegetation in mid-ocean called “sargasso seas.” You will remember that a branch of the Gulf Stream, striking over toward the Moorish coast of Africa, is turned southward there, and sweeps down to the equator, then westward again, circumscribing a broad region in the middle Atlantic whose only currents go round and round in a slow whirlpool; and here it is that the gulfweed concentrates in masses sometimes dense enough to impede the progress of a ship—Columbus reported among the wonders of his first voyage the trouble he had in sailing through it—and covering an area between the Azores and the Bahamas as large as the Mississippi valley. This is the Sargasso Sea ordinarily referred to in books, but it is not the only one. A thousand miles west of San Francisco there is a similar collection of floating plants, and others exist under like conditions in the southern oceans.
THE MARBLED ANGLER ON ITS GULFWEED RAFT.
These floating meadows, as it were, are chosen as the abode of a long list of animals that rarely quit the safety and plenty of their precincts. Among these are innumerable pretty jelly-fishes, sea-worms, and mollusks without shells, which cling to the buoyant plants, and perhaps feed solely upon them. Here are to be had in abundance the fairy-like, rare pteropods, the richly purple janthinas towing their curious rafts of eggs, and no end of small crabs. Here a small fish, something like a perch, spends his whole time building a nest like a bird’s in the tangled weed-masses, and carefully guarding his treasures against the large marauding fishes that haunt the place to the dread of its peaceful inhabitants; and here those far-flying birds, the wandering albatross and the petrels, hover about in search of something to capture and eat. The Sargasso Sea is an extremely interesting part of the ocean, except to the luckless sailor becalmed and balked in its midst, as was Sir John Hawkins when he penned the following quaint observations, some three centuries ago:
Were it not for the Moving of the Sea, by the Force of Winds, Tides and Currents, it would corrupt all the World. The Experience of which I Saw Anno 1590, lying with a Fleet about the Islands of Azores, almost Six Months, the greatest Part of the time we were becalmed, with which all the Sea became so replenished with several sorts of Gellies and Forms of Serpents, Adders and Snakes, as seem’d Wonderful; some green, some black, some yellow, some white, some of divers Colours, many of them had Life, and some there were a Yard & a half, & some two Yards long; which had I not seen, I could hardly have believed.