This, James Hutton's last work, was unfinished at his death in 1797. The text is written by an amanuensis on the rectos only, with occasional notes on the versos. Not infrequently pieces have been torn from the sheets before they were written on. There are some corrections by Hutton himself, especially at the beginning, and an early draft of part of the preface, bound in after folio 2, is also in his hand. On folios ii-viii are comments on the work in an unidentified hand.