This is a treatise, consisting of six letters, upon a very difficult and important question, which, I am afraid, this author's endeavours will not free from the perplexity which has entangled the speculatists of all ages, and which must always continue while we see but in part.

The disciples of subtile speculatists like Aquinas, or of fervent mystics like Bonaventura, were not likely to recognize the worth and importance of the slow processes of experimental philosophy.

The descriptions of the productions of the earth and water, which this volume will contain, may be equally pleasing and useful to the speculatist with any other natural history; and the accounts of various manufactures will constitute no contemptible body of experimental philosophy.