Chap. X.] THE LAPSE OF TIME. 55 



upwards of 30 miles, and along this line the vertical 

 displacement of the strata varies from 600 to 3000 feet. 

 Professor Eamsay has published an account of a down- 

 throw in Anglesea of 2300 feet ; and he informs me 

 that he fully believes that there is one in Merioneth- 

 shire of 12,000 feet ; yet in these cases there is nothing 

 on the surface of the land to show such prodigious 

 movements ; the pile of rocks on either side of the 

 crack having been smoothly swept away. 



On tlie other hand, in all parts of the world the piles 

 of sedimentary strata are of wonderful thickness. In 

 the Cordillera I estimated one mass of conglomerate at 

 ten thousand feet ; and although conglomerates have 

 probably been accumulated at a quicker rate than finer 

 sediments, yet from being formed of worn and rounded 

 pebbles, each of which bears the stamp of time, they 

 are good to show how slowly the mass must have been 

 heaped together. Professor Eamsay has given me the 

 maximum thickness, from actual measurement in most 

 cases, of the successive formations in different parts of 

 Great Britain ; and this is the result : — 



Feet. 



Palceozoic strata (not including igneous beds) .. .. 57,154 



Secondary strata .. .. 13,190 



Tertiary strata 2,240 



— making altogether 72,584 feet; that is, very nearly 

 thirteen and three-quarters British miles. Some of the 

 formations, which are represented in England by tliin 

 beds, are thousands of feet in tliickness on the Con- 

 tinent. Moreover, between each successive formation, 

 we have, in the opinion of most geologists, blank 

 periods of enormous length. So that the lofty pile of 



sedimentary rocks in Britain gives but an inadequate 

 23 



