CHAPTER XL 



SUPERFICIAL DEPOSITS {continued). 



Early condition of the surface after elevation from beneath the sea. — Lacustrine 

 and broad river period. — Passage to present condition. — Remains of extinct 

 species of quadrupeds. — Ancient river deposits. 



WE have now to ascertain the changes which the surface has undergone since large 

 masses of land were raised from beneath the sea. In this inquiry I shall endeavour to 

 explain first, the transition from ancient to modern phenomena, showing why the latter 

 must have mainly resulted from the former, in consequence of alterations in the relative 

 level of land and water ; and secondly, the modern terrestrial changes and accumula- 

 tions. In this attempt to connect in one series the operations which took place during 

 an early condition of the surface with that which now prevails, the following subjects 

 will be successively examined in this and the subsequent chapter. 1st. The early con- 

 dition of Siluria shortly after its emersion from the sea, when that region must, it is 

 supposed, have been in great part irrigated by lakes and broad rivers. 2ndly. How such 

 great water courses have been diminished. Srdly. The proofs that Siluria on the one 

 hand, and parts of England on the other, were inhabited by early races of quadrupeds. 

 4thly. The desiccation of lakes and turbaries within the historic sera. 5thly. The 

 modern action of rivers. 6thly. The periodical floods of sand, and effects of great 

 storms, &c. 7thly. Terrestrial accumulations, such as shell marl, travertine, &c. 



In this chapter the reader must figure to himself the condition of the surface, imme- 

 diately after the rise of the land from beneath the sea, when large hollows were occupied 

 by water which has been subsequently let off by transverse gorges, and the lowering 

 of the river-courses to their present levels 1 . 



1 In speaking of lakes I make an application of the term which some geologists may perhaps disapprove 

 of, seeing that no zoological proofs of lacustrine deposits are brought forward. Still as the occurrence of 

 fine silt and sand in embayed flats, thus distinguished from the coarse drift before described, can in no way 

 be explained, except by the tranquil occupation of water, I am compelled to believe that in the intermediate 

 period between the elevation of the bottom of the ancient sea and the establishment of the present drainage, 

 such tracts were in fact lakes, which have since been let off. 



