THE LAPSE OP TIMB. 3i7 



glance how far the hard, rocky beds had once extended 

 into the open ocean. The same story is told still more 

 plainly by faults — those great cracks along which the strata 

 have been upheaved on one side, or thrown down on the 

 other, to the height or depth of thousands of feet; for since 

 the crust cracked, and it makes no great difference whether 

 the upheaval was sudden, or, as most geologists now believe, 

 was slow and effected by many starts, the surface of the 

 land has been so completely planed down that no trace of 

 these vast dislocations is externally visible. The Craven 

 fault, for instance, extends for upward of thirty miles, and 

 along this line the vertical displacement of the strata varies 

 from 600 to 3,000 feet. Professor Eamsay has published 

 an account of a downthrow in Anglesea of 3,300 feet; and 

 he informs me that he fully believes that there is one in 

 Merionethshire 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 the 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. 



Palseozoic strata (not including Igneous beds) 57,154 



Secondary strata 13,190 



Tertiary strata 3,240 



—making altogether 73,584 feet; that is, very nearly thir- 

 teen and three-quarters British miles. Some of the for- 

 mations, which are represented in England by thin beds, 

 are thousands of feet in thickness on the Continent. More- 

 over, 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 



