GEOLOGIES AND DELUGES. 247 



seams of limestone and clay called tlie Lias, and these in tlieir 

 turn upon the red beds of the Trias. It might perhaps have been 

 expected that this uniform arrangement would continue through 

 the whole thickness of the stratified rocks, but it was discovered, 

 and the importance of the discovery was recognized so early as 

 1G70 by Bishop Steno, a man of great genius, that the regularity 

 of the successions is liable to interruption at intervals. Thus as 

 we approach Bristol we encounter those beds of limestone which 

 are associated with our coal-bearing strata, and which are conse- 

 quently called " carboniferous " ; but these are by no means re- 

 lated to the beds we have just passed over in the same manner 

 as they are to one another we do not find the highest bed of the 

 carboniferous series offering its upper surface as a gently sloping 

 platform on which the trias may rest ; on the contrary, the car- 

 boniferous beds are seen to lie in great rolling folds, with tne 

 tops of the rising folds absent, as it were sliced off, and it is on 

 the edges, not on the surface, of these beds that the red trias layers 

 are seen to be spread out. This sudden change in disposition 

 may well be called a break in the succession of the rocks, and, as 

 if to emphasize it and compel attention to it, we find it accom- 

 panied by a complete change in the character of the fossils, those 

 occurring in the carboniferous rocks being of entirely different 

 kinds from those which are found in the overlying beds. 



Evidently the carboniferous beds could not have been laid 

 down in the sea in the steeply folded form they now present ; at 

 first they must have been spread out in nearly horizontal layers, 

 and the folded form must have been subsequently impressed 

 upon them, no doubt by the action of some stupendously power- 

 ful force. Subsequent also must have been the removal of the 

 upper parts of the folds and the general planing down which 

 they appear to have undergone. 



To the young geology all this might seem perfectly clear, but 

 in its impulsive explanations it assumed that Nature must have 

 frequently acted in a great and terrible hurry : thus the folding 

 of the rocks was supposed to have been produced suddenly and 

 violently by a single mighty convulsion, which simultaneously 

 changed sea floors into mountain chains, split open the land in 

 wide-gaping chasms our present river valleys and with the 

 same blow destroyed every living inhabitant in the world. 



But the discordance between two sets of rocks is met with not 

 once only, but several times, in the stratified rocks of the earth's 

 crust, and for every discordance there must have occurred a cor- 

 responding catastrophe. 



These catastrophes were as wonderful as Burnett's, and there 

 were more of them, so that at this stage of its existence geology 

 was appropriately designated " catastrophic." It had completely 



