The reader will observe that our author uses the fence only as a convenient formula for expressing the power of the wind, and does not consider it a necessary method of its application. We do not attach much value to this statement of the comparative power of the wind and horse, for no common ground is mentioned on which they can be compared. Undoubtedly, each is incomparably excellent in its way, and every general comparison made for such practical purposes as are contemplated, which gives a preference to the one, must be made with some unfairness to the other. The scientific tables are, for the most part, true only in a tabular sense. We suspect that a loaded wagon, with a light sail, ten feet square, would not have been blown so far by the end of the year, under equal circumstances, as a common racer or dray horse would have drawn it. And how many crazy structures on our globe’s surface, of the same dimensions, would wait for dry-rot if the traces of one horse were hitched to them, even to their windward side? Plainly, this is not the principle of comparison. But even the steady and constant force of the horse may be rated as equal to his weight at least. Yet we should prefer to let the zephyrs and gales bear, with all their weight, upon our fences, than that Dobbin, with feet braced, should lean ominously against them for a season.
Nevertheless, here is an almost incalculable power at our disposal, yet how trifling the use we make of it. It only serves to turn a few mills, blow a few vessels across the ocean, and a few trivial ends besides. What a poor compliment do we pay to our indefatigable and energetic servant!
“If you ask, perhaps, why this power is not used, if the statement be true, I have to ask in return, why is the power of steam so lately come to application? so many millions of men boiled water every day for many thousand years; they must have frequently seen that boiling water, in tightly closed pots or kettles, would lift the cover or burst the vessel with great violence. The power of steam was, therefore, as commonly known down to the least kitchen or washwoman, as the power of wind; but close observation and reflection were bestowed neither on the one nor the other.”
Men having discovered the power of falling water, which after all is comparatively slight, how eagerly do they seek out and improve these privileges? Let a difference of but a few feet in level be discovered on some stream near a populous town, some slight occasion for gravity to act, and the whole economy of the neighborhood is changed at once. Men do indeed speculate about and with this power as if it were the only privilege. But meanwhile this aerial stream is falling from far greater heights with more constant flow, never shrunk by drought, offering mill-sites wherever the wind blows; a Niagara in the air, with no Canada side;—only the application is hard.
There are the powers too of the Tide and Waves, constantly ebbing and flowing, lapsing and relapsing, but they serve man in but few ways. They turn a few tide mills, and perform a few other insignificant and accidental services only. We all perceive the effect of the tide; how imperceptibly it creeps up into our harbors and rivers, and raises the heaviest navies as easily as the lightest chip. Everything that floats must yield to it. But man, slow to take nature’s constant hint of assistance, makes slight and irregular use of this power, in careening ships and getting them afloat when aground.
The following is Mr. Etzler’s calculation on this head: To form a conception of the power which the tide affords, let us imagine a surface of 100 miles square, or 10,000 square miles, where the tide rises and sinks, on an average, 10 feet; how many men would it require to empty a basin of 10,000 square miles area, and 10 feet deep, filled with seawater, in 6¼ hours and fill it again in the same time? As one man can raise 8 cubic feet of seawater per minute, and in 6¼ hours 3,000, it would take 1,200,000,000 men, or as they could work only half the time, 2,400,000,000, to raise 3,000,000,000,000 cubic feet, or the whole quantity required in the given time.
This power may be applied in various ways. A large body, of the heaviest materials that will float, may first be raised by it, and being attached to the end of a balance reaching from the land, or from a stationary support, fastened to the bottom, when the tide falls, the whole weight will be brought to bear upon the end of the balance. Also when the tide rises it may be made to exert a nearly equal force in the opposite direction. It can be employed wherever a point d’appui can be obtained.
“However, the application of the tide being by establishments fixed on the ground, it is natural to begin with them near the shores in shallow water, and upon sands, which may be extended gradually further into the sea. The shores of the continent, islands, and sands, being generally surrounded by shallow water, not exceeding from 50 to 100 fathoms in depth, for 20, 50, or 100 miles and upward. The coasts of North America, with their extensive sandbanks, islands, and rocks, may easily afford, for this purpose, a ground about 3,000 miles long, and, on an average, 100 miles broad, or 300,000 square miles, which, with a power of 240,000 men per square mile, as stated, at 10 feet tide, will be
