26 Anniversary Address of the 



sandstones and sandy or gravelly strata with subordinate 

 diagonal layers, confirm these views. Such movements took 

 place contemporaneously with the growth of organic matter, 

 just as subsidence on a grand scale is now going on over 

 vast areas in the Pacific and Indian Oceans, — a class of facts 

 on which Mr Darwin has founded his theory of atolls, or the 

 origin of annular coral islands with lagoons. His theory, as 

 you have probably observed, has been recently embraced and 

 more fully elucidated by Mr Dana, in his valuable chapters 

 on the geology of the American Exploring Expedition under 

 Captain Wilkes. 



The investigations of Professor Edward Forbes, on the 

 laws governing the distribution of marine animal life, at 

 various depths in the Mediterranean, have powerfully aided 

 us in determining the conditions under which particular 

 strata were formed, the depth of water being deducible from 

 a careful study of the organic contents of each bed. Avail- 

 ing themselves of this key. Captain Ibbetson and Professor 

 Forbes have shown how the lower cretaceous strata of the 

 Isle of Wight have been deposited on a gradually sinking 

 submarine bottom, while Mr Prestwich has applied the same 

 method of reasoning, with equal success, to the eocene strata 

 of Alum and WhiteclifF Bays in the same island.* In this 

 instance it is remarkable, that after a depression of 1800 

 feet very slowly effected, there was still contiguous land in- 

 habited by the Paleeothere of Binstead and Hordwell and its 

 contemporaries, as well as a freshwater estuary, implying 

 that the movements in different parts of that region were 

 either very unequal or opposite, or that they consisted of 

 great oscillations of level. It would be easy to cite a variety 

 of continental authorities in support of the same principle, 

 but enough has been said to entitle me to ask, whether the 

 subsidence of mountainous masses, lying immediately beneath 

 the floor of the ocean, brought about by such slow degrees, can 

 possibly occur, without causing beneath many of the sunk 

 areas, vast flexures of the strata, which as they sink for 

 miles vertically must occasionally be forced to pack them- 



* Prestwich, Quart. Journ. Geol. Soc. vol. ii. p. 223. 



