For if, instead of a solid rock, we shall suppose a continent composed of either dry sand or watery mud, without solidity or stability, how imperfect still would be that world for the purpose of sustaining lofty trees and affording fruitful soils!

We have now mentioned the two extreme states of things; but the constitution of this earth is no other than an indefinite number of soils and situations, placed between those two extremes, and graduating from the one extreme, in which some species of animals and plants delight in finding their prosperity, to the other, in which another species, which would perish in the first, are made to grow luxuriantly.  That is to say, the surface of this earth, which is so widely adapted to the purpose of an extensive system of vegetating bodies and breathing animals, must consist of a gradation from solid rock to tender earth, from watery soil to dry situations; all this is requisite, and nothing short of this can fulfil the purpose of that world which we actually see.

We have been representing this continent of our earth as coming out of the ocean a solid mass, which surely it is in general, or in a great degree; but we find the surface of this body at present in a very different state; and now it will be proper to take a view of this change from solid rock to fertile soil.

Upon this occasion I shall give the description of nature from the writings of a philosopher who has particularly studied this subject.  It is true that M. de Luc, who furnishes the description, draws, from this process of nature, an argument for the perpetual duration or stability of mountains; and this is the very opposite of that view which I have taken of the subject; but as, in this operation of nature producing plants on stones, he allows the surface of the solid stone to be changed into earth and vegetables, it is indifferent to the present theory how he shall employ this earth and vegetable substance, provided it be acknowledged that there is a change from the solid state of rock to the loose or tender nature of an earth, from the state of a body immovable by the floods and impenetrable to the roots of plants, to one in which some part of the body may be penetrated and removed.

[8]"Les pluies et les rosees forment partout ou elles sejournent, des depots qui sont la premiere source de toute vegetation.  Ces depots sont toujours meles des semences des mousses, que l’air charie continuellement, et auxquelles se joignent bientot les semences presque aussi abondantes des gramens, qui sont l’herbe dominante de nos prairies.  Ainsi partout ou la pluie a forme quelque petit depot, il croit de la mousse ou des gramens.  Ceux-ci demandent un peu plus de terre vegetale pour croitre, ils germent, et se conservent principalement dans les intervalles et les creux des pierres:  mais la mousse croit bientot sur la surface la plus unie.  Il n’est aucune pierre long-temps exposee a l’air, qui soit parfaitement polie; l’action de l’air, du soleil, des eaux, des gelees, detruiroit ce poli quand il existeroit.  Le moindre creux alors recoit un depot de la pluie, et nourrit un brin de mousse, ces brins poussent des racines; et de nouveaux jets autour d’eux, qui contribuent a arreter l’eau de la pluie et de la rosee, et par ce moyen a arreter les depots Nourriciers.”