loſophy as to ſtart Difficulties to the Suppoſition of this natural Fertility of the Earth, I ſhall endeavour to obviate them by the following Paſſage.
"As Vegetables derive for their Support a great deal more Subſtance from the Air and Water than from the Earth, ſo, when they decay, they reſtore to the Earth more than they received from it; moreover, Foreſts engroſs great Quantities of Rain Water by ſtopping the Vapours that form it. Thus, in Woods that have remained untouched for a long Time, the Layer of Earth, in which the Buſineſs of Vegetation is carried on, muſt have received a conſiderable Addition. But Animals reſtoring to the Earth leſs than they derive from it, and Men conſuming enormous Quantities of Vegetables for firing and other Purpoſes, it follows that the Layer of vegetating Earth, in well peopled Countries, muſt be conſtantly on the Decline, and become at laſt like the Surface of Arabia Petrea, and ſo many other Provinces of the Eaſt, (which in Fact is the Part of the World that was earlieſt inhabited)
