Page:Anti-slavery and reform papers by Thoreau, Henry David.djvu/111

 lOO A nil- Slavery and Reform Papers.

our Green ^Mountains need some of that sea-green to be mixed with them.

The computation of the power of the waves is less satisfactory. While only the average power of the wind, and the average height of the tide, were taken before, now the extreme height of the waves is used, for they are made to rise ten feet above the level of the sea, to which, adding ten more for depression, we have twenty feet, or the extreme height of a wave. Indeed, the power of the waves, which is produced by the wind blowing obliquely, and at disadvantage upon the water, is made to be, not only three thousand times greater than that of the tide, but one hundred times greater than that of the wind itself, meeting its object at right angles. jNLjreover, this power is measured by the area of the vessel, and not by its length mainly, and it seems to be forgotten that the motion of the waves is chiefly undulatory, and exerts a power only within the limits of a vibration, else the very continents, with their extensive coasts, would soon be set adrift.

Finally, there is the power to be derived from sunshine, by the pi-iuciple on which Archimedes contrived his burning-mirrors, a multiplication of mirrors reflecting the rays of the sun upon the same spot, till the requisite degree of heat is obtained. The principal application of this power will be to the boiling of water and production of steam. So much for these few and more obvious powers, already used to a trifling extent. But there are innumerable others in nature, not described nor dis- covered. These, however, will do for the present. This would be to make the sun and the moon equally our satellites. For, as the moon is the cause of the tides.