With a general resemblance in their fossils, nothing can be more dissimilar, on the whole, than the lithological or mineral characters of the Eocene deposits of France and England; “those of our own island,” says Lyell,[84] “being almost exclusively of mechanical origin--accumulations of mud, sand, and pebbles; while in the neighbourhood of Paris we find a great succession of strata composed of limestones, some of them siliceous, and of crystalline gypsum and siliceous sandstone, and sometimes of pure flint used for millstones. Hence it is by no means an easy task to institute an exact comparison between the various members of the English and French series. It is clear that, on the sites both of Paris and London, a continual change was going on in the fauna and flora by the coming in of new species and the dying out of others; and contemporaneous changes of geographical conditions were also in progress in consequence of the rising and sinking of the land and bottom of the sea. A particular subdivision, therefore, of time was occasionally represented in one area by land, in another by an estuary, in a third by sea; and even where the conditions were in both areas of a marine character, there was often shallow water in one, and deep sea in another, producing a want of agreement in the state of animal life.” The Eocene rocks, as developed in France and England, may be tabulated as follows, in descending order:-- [84] “Elements of Geology,” p. 292. English. French. / \ / Calcaire de la Beauce. | Hempstead beds. | \ Grès de Fontainebleau. | | Upper Eocene. < | / Calcaire silicieux or | Bembridge beds. >Fluvio-marine< Calcaire Lacustre | | series. | Moyen. Gypseous \ | \ series of Montmartre. | / Osborne beds. | / Grès de Beauchamp | Headon beds. / \ and Calcaire Marin. | | Upper Bagshot sand. Upper Sables Moyens. | Middle Eocene.< / Lower Sables Moyens, | Barton clay. \ Middle < Lower Calcaire | Bracklesham beds. / Bagshot. | Grossier, and | \ Glauconie Grossière. | | Lower Bagshot / Lits coquillières. \ beds. \ Glauconie Moyenne.