The great majority of seaweeds grow between tide-marks, and they undoubtedly perform an important service in preventing the wear and tear of the coast in many situations. Some, however, grow in much deeper waters, and these, also, may serve as breakwaters of no mean strength. Such is the case, for instance, at San Pedro, near Los Angeles, California, where the abundant growth offshore forms such a barrier to the ocean rollers as to turn the open roadstead into a calm harbor within it. This belongs to the group of gigantic kelps of which those at the Falkland Islands and about Tierra del Fuego are other and noted species. Were it not for the growth of this strong, cable-like, buoyant plant, large numbers of other plants and sea-animals would find it impossible to exist exposed to the violence of the South Pacific waves. Sometimes the stems reach twelve hundred feet in length, and the bladders by which the immense fronds are buoyed up are as big as kegs. This gigantic seaweed is plentiful all along the Pacific coast of America to Alaska, and the natives of our northwest coast used to make extensive use of it in the way of ropes, etc. It was from this weed that, by a careful preparation, they made the lines for their harpoons and deep-sea fishing; and the bladders furnished them ready-made receptacles for eulachon oil, for water for their seatrips, and for other liquids. A California correspondent of the New York “Evening Post” gave a pretty picture, not long ago, of one of the kelp patches at St. Nicholas Island, where the beds of this wonderful plant reach out for a mile or more, growing up from the rocks below and forming an effectual break; the seas losing their force in their effort to pass through the submarine meshwork. The vines constitute a veritable forest, and, drifting over it in fifty or sixty feet of water, you may see a perfect maze of stems with broad leaves waving gracefully in the current, forming arbors, arches, and colonnades. Here, poised idly, in rich contrast to the olive-hued mass, may be seen fish of a bright golden color, others in tints of blue and green. The sea swell coming in causes an undulatory movement, and the long colonnades seem to melt one into another, reappearing in different shapes. When the leaves reach the surface, the shore wind, sweeping down from the hills, lifts them from the water, and they flutter in the air like mimic sails. Each leaf is a study. Many are encrusted with a delicate bryozoön, which presents the effect of white lace upon the surface, while a close inspection will reveal minute anemones, coiled tubular worms, which throw out flower-like organs of exquisite beauty; while flat shells lie among them, and crawling here and there are marvels of animal life, shell-less mollusks, which so mimic the weed that it is almost impossible to distinguish them. [Illustration: DIATOMS, MAGNIFIED, IN A DROP OF WATER.]