THE LAPSE OF TIME. 297 



district and those ranging across England, which formerly 

 were looked at as ancient sea-coasts, cannot have been thus 

 formed, for each line is composed of one and the same for- 

 mation, while our sea cliffs are everywhere formed by the 

 intersection of various formations. This being the case, we 

 are compelled to admit that the escarpments owe their 

 origin in chief part to the rocks of which they are com 

 posed, having resisted subaerial denudation better than the 

 surrounding surface ; this surface consequently has been 

 gradually lowered, with the lines of harder rock left pro- 

 jecting. Nothing impresses the mind with the vast dura- 

 tion of time, according to our ideas of time, more forcibly 

 than the conviction thus gained that subaerial agencies, 

 which apparently have so little power, and which seem to 

 work so slowly, have produced great results. 



When thus impressed with the slow rate at which the 

 land is worn away through subaerial and littoral action, it is 

 good, in order to appreciate the past duration of time, to 

 consider, on the one hand, the masses of rock which have 

 been removed over many extensive areas, and on the other 

 hand the thickness of our sedimentary formations. I re- 

 member having been much struck when viewing volcanic 

 islands, which have been worn by the waves and ^nred all 

 round into perpendicular cliffs of one or two thousand feet 

 in height ; for the gentle slope of the lava streams, due to 

 their formerly liquid state, showed at a 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 Ramsay has published an account of a downthrow 

 in Anglesea of 2,300 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. 



