Note 9 — Treatise on Agriculture.

In this respect nature has been neither negligent or niggardly, if (as Fourcroy asserts) the purest sand be a mixture of quartz, alumina, and sometimes of calcareous matter. Speculative geology is romance, and does not merit the name of science; yet is science obliged to borrow her theory of soils. The alternation of heat and cold, moisture and dryness, decomposed the mountains of primitive, secondary and tertiary formation; rains, and the laws of gravity, brought these from places of more, to places of less elevation—where, by mechanical mixture and chymical combination, the present substrata were formed. But these were yet naked and unproductive, when the Cryptogamia family (mopes and lichens) took possession of them, and in due time produced that vegetable matter, which made the earth productive and the globe habitable!