not many leifure-hours, never banished from his mind, that he would little deferve to be of the human fpecies, were he indifferent about his fellow-creatures :

Homo fum: humani nihil a me alienum puto.

Moft of the fubjects handled in the following fheets, admit but of probable reafoning; and with refpect to fuch reafonings, it is often difficult to fay, what degree of conviction they ought to produce. It is easy to form plaufible arguments ; but to form fuch as can ftand the test of time, is not always eafy. I could amufe the reader with numerous examples of conjectural arguments, which, fair at a diftant view, vanish like a cloud on a near approach. Several examples, not to go farther, are mentioned in the preliminary difcourfe of this book. The hazard of being misled by fuch arguments, gave the author much anxiety; and after his utmost attention, he can but faintly hope, that he has not often wandered far from truth.

Above thirty years ago, he began to collect materials for a natural history of man; and in the vigour of youth, did not think the undertaking too bold, even for a fingle hand. He has difcovered of late, that his utmost abilities are scarce fufficient for executing a few imperfect fketches.

Edinburgh, Feb. 23. 1774.