LET. XV.

OF THE EARTH.

257

This revolution, however, has not takenplace. The East and West Indies, and a greatpart of the vast continents of Africa and Ame-rica, lie in the neighbourhood of the equator,and are sufficient proofs, that the earth rises todefend itself against the invasions of the ocean.Every part of the 'globe, therefore, from thecenter to the circumference, is subject to theaction of a centrifugal force; and supposing theprimitive figure of the earth to have been thatof a globe, which is the shape it would naturallyassume from the mutual attraction of its con-stituent parts, this force, or the action arisingfrom a constant rotation upon its axis, wouldevidently change it into an oblate spheroid, ora body nearly resembling a turnip, or an orange.This was the figure determined by Newton, whofound, by mathematical calculations, that thepolar diameter of the earth is to the equatorial,as two hundred and twenty-nine is to two hun-dred and thirty; or, that the regions of theequator are elevated about thirty-five miles morethan those at the poles.

Who could have imagined, that such a simplecircumstance as the retardation of clocks incertain climates, and the necessary shorteningof the pendulum, would have given birth tosuch a grand and important discovery, as thatof the true figure of the earth ! But such is thewonderful connection and secret dependence of

S things;