I am convinced, by repeated observation, that marbles, lime-stones, chalks, marls, clays, sand, and almost all terrestrial substances, wherever situated, are full of shells and other spoils of the ocean.

'Second Discours: Histoire & Théorie de la Terre', Histoire Naturelle, Générale et Particulière, Avec la Description du Cabinet du Roi (1749), Vol. 1, 76–77; Natural History, General and Particular (1785), Vol. 1, trans. W. Smellie