In it there is presented the history of the most recent changes that have taken place in a particular basin, and it descends so far as the Chalk formation, the extent of which over the globe is vastly more considerable than that of the materials of the basin of Paris. The chalk, which has been considered so modern, is thus found to be advanced in antiquity among the ages of the great period preceding the last catastrophe. It forms a sort of limit between the most recent formations, those to which the name of _Tertiary_ may be reserved, and the formations which are named _Secondary_, which have been deposited before the Chalk, but after the Primitive and Transition formations. _Recapitulation of the Observations upon the Succession of the Tertiary Formations._ The most superficial strata, those deposits of mud and clayey sand, mixed with rolled pebbles, that have been transported from distant countries, and filled with bones of land animals, the species of which are for the most part unknown, or at least foreign to the country in which they are found, seem especially to have covered all the plains, filled the bottom of all the caverns, and choked up all the fissures of rocks that have come in their way. Described with particular care by Mr Buckland, under the name of _diluvium_, and very different from those other beds equally consisting of transported matters, continually deposited by torrents and rivers, which contain only bones of animals that still live in the country, and distinguished by the name of _alluvium_, the former are now considered by all geologists as exhibiting the most obvious proof of the immense inundation which has been the last of the catastrophes of our globe[245]. Between this diluvium and the chalk, are the formations alternately filled with fresh water and salt water productions, which mark the irruptions and retreatings of the sea, to which this part of the globe has been subjected, since the deposition of the chalk-strata: first, marls and buhrstones, or cavernous quartz, filled with fresh-water shells, similar to those of our marshes and pools; under them marls, sandstones, and limestones, all the shells of which are marine, such as oysters, &c. At a greater depth are found fresh water formations of an older date, and particularly those famous gypsum deposits of the neighbourhood of Paris, which have afforded so much facility in ornamenting the buildings of that great city, and in which we have discovered whole genera of land-animals, of which no traces had been elsewhere perceived.