GEOLOGICAL RESEARCHES. 31 



time; but no fossils have yet been discovered in them. 

 Lyell's classification of the Tertiary deposits ; the 

 result of the studies which he carried on with the 

 assistance of Deshayes and others, was published in the 

 third volume of the ' Principles of Geology ' in 1833. 

 The establishment of Lyell's divisions of Eocene, 

 Miocene, and Pliocene, was the starting-point of a most 

 important series of investigations by *Prestwich and 

 others of these younger deposits ; as well as of the post- 

 tertiary, quaternary, or drift beds, which are of special 

 interest from the light they have thrown on the early 

 history of man. 



A full and admirable account of what has recently 

 been accomplished hi this department of science, es-. 

 pecially as regards the palaeozoic rocks, will be found 

 in Etheridge's late address to the Geological Society. 



The thickness of the sedimentary strata implies an 

 enormous lapse of time, but the amount of subsequent 

 destruction which has taken place is scarcely less sur- 

 prising. Ramsay, for instance, has shown that in Wales 

 from 9,000 to 11,000 feet of solid rock have been re- 

 moved from large tracts of country. Faults or cracks 

 there extend for miles, with the strata on one side 

 raised in some cases as much as 10,000 feet above the 

 same strata on the other, and yet there is not on the 

 surface the slightest vestige of this gigantic dislocation. 



The long lines of escarpment again, which stretch 

 for miles across our country, and were long supposed 

 to be ancient coast lines, are now ascertained, mainly 

 through the researches of Whitaker, to be due to the 

 differential action of aerial causes. 



Before 1831 the only geological maps of this 



