Page:A Treatise on Geology, volume 1.djvu/335

 CHAP. VI. was in the latest period of the ice rafts that the large erratic blocks were scattered in greatest abundance.

None of these phenomena appear to require more violent watery movements than such as the sinking and rising of the land must have occasioned, even if it were accomplished by many small gradations. In particular cases, to which the agency of icebergs is inapplicable, excessive local violence of water has been appealed to. For explanation of the bands of angular chalk flints parallel to the axis of the Wealden, Murchison requires the violent concussion of limited tracts, from which he supposes these flint bands to have been mainly derived. There is no antecedent improbability in a postulate of this kind; its necessity must be judged of as a special problem on appropriate evidence.

The diluvial deposits appear, in general, characterised by the presence of a great number of land animals, and some sorts of trees, which are much more similar to existing forms of life than are the tertiary quadrupeds and plants. But this general or average result requires to be limited by several considerations: first, there are deposits reputed tertiary, as the sandy deposits of Eppelsheim, on the Rhine, in which occur a vast number of species very nearly approaching to existing races; secondly, among the animals of the diluvial period are species, and even genera, as totally distinct from the actual creation as any of the tertiary groups; thirdly, in deposits of undoubtedly tertiary date, as the subapennines of Italy, the sands and marls of the Danube, and flanks of the Carpathians, the crag of Norfolk, bones and teeth of elephant, rhinoceros, mastodon, and other genera of the diluvial period, have been found, though not frequently. It appears, therefore, certain, on this evidence, that the transition from the tertiary to later periods was not accompanied by a sudden