The theory consists in this, that it is necessary to have a habitable country situated in the atmosphere, or above the surface of the sea.

It is difficult to say precisely what constitutes a habitable country.  A resting place out of the water suffices for such amphibious animals as, while they necessarily live in the atmosphere, feed in the sea.  Man, more versatile in his nature than most animals, and more capable of adapting his manners to his circumstances, is even sometimes found subsisting in situations where the land affords him little more than it does the seal on which he feeds.  The growth of terrestrial plants, however, seems necessary to the idea of a habitable country; and, for the growth of plants, there is required soil:  Now, this is only to be procured by the resolution or decay of solid land.

We are not to consider the resolution of our land as being the effect of accident, while it is performed by the operations of the sun and atmosphere, by the alternate action of moisture and of drought, and by the casual operations of a river in a flood.  Nothing is more steady than the resolution of our land; nothing rests upon more certain principles; and there is nothing which in science may be more easily investigated.

Calcareous, argillaceous, and other soluble earths, compose many of the strata; but in many more, which are partly or chiefly composed of insoluble substances, those soluble earths are mixed in various proportions.  Now, when the siliceous substance, which is the insoluble part, shall be supposed resisting every effort of the elements towards its dissolution, those compound masses upon the surface of the earth, however endued with hardness and solidity, are gradually impaired by the dissolution of some of their constituent parts, and by the separation of others which are thus exposed to the ablution of water.  In like manner, by the resolution of the surrounding parts, the solid silex, which is supposed to be insoluble, is removed from its bed, and thus suffers new parts of the solid land to be exposed to those injuries of the air, by which the general good of plants, of animals, and even of future worlds, are consulted.

The solid land is resolved into stones, gravel, sand, earths, and clays; all or either of these, by retaining moisture, and affording places for the roots of plants, are disposed for vegetation in different degrees; a mixture of the different earths being, upon the whole, the best suited to that purpose; and this compound body, mixed with vegetable or animal substances, becoming a most luxuriant soil.