Uniformity in Geological Change 



States. These older rocks are still as flat and 

 horizontal as when first formed; yet, since their 

 origin, not only have most of the actual moun- 

 tain-chains been uplifted, but some of the very 

 rocks of which those mountains are composed 

 have been formed, some of them by igneous and 

 others by aqueous action. 



It would be easy to multiply instances of 

 similar unconformability in formations of other 

 ages; but a few more will suffice. The carbon- 

 iferous rocks before alluded to as horizontal on 

 the borders of Wales are vertical in the Mendip 

 hills, Somersetshire, where the overlying beds of 

 the New Red Sandstone are horizontal. Again, 

 in the Wolds of Yorkshire the last-mentioned 

 sandstone supports on its curved and inclined 

 beds the horizontal Chalk. The Chalk again 

 is vertical on the flanks of the Pyrenees, and the 

 tertiary strata repose uncomformably upon it. 



As almost every country supplies illustrations 

 of the same phenomena, they who advocate the 

 doctrine of alternate periods of disorder and re- 

 pose may appeal to the facts above described, 

 as proving that every district has been by turns 

 convulsed by earthquakes and then respited for 

 ages from convulsions. But so it might with 

 equal truth be affirmed that every part of Europe 

 has been visited alternately by winter and sum- 

 mer, although it has always been winter and 

 always summer in some part of the planet, and 

 neither of these seasons has ever reigned simul- 

 taneously over the entire globe. They have 

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