HOME STUDIES IN CHEMISTRY AND PHYSICS.
BY PROF. J. T. EDWARDS, D.D.
Director of the Chautauqua School of Experimental Science.
PHYSICS OF EARTH.
Our earth, as a whole, may be compared to a ship sailing on a smooth sea. Like the ship, it has its own motions with reference to other objects, and is affected by forces exterior to itself. The ship feels the influence of winds, currents and tides.
The earth also yields to forces outside of itself; to such an extent, indeed, that philosophers have more than once been led to look for an invisible power, which strangely affected it. For example, Adams[1] and Leverrier[2] were led to prophesy the existence of the planet Neptune, because the earth seemed to yield to the touch of some unknown body, which was afterward discovered at the enormous distance of 2,746,271,000 miles.
The ship, in addition to its motion in regard to distant points and susceptibility of being moved by outside forces, has its own peculiar construction, a complex adjustment of planks, timbers, bolts, spars, sails and ropes. It also has its inhabitants, living beings which move to and fro, quite independent, for the time being, of all other parts of the universe, save that on which they reside.