CHAPTEK III. 



DENUDATION, SYNCLINAL AND ANTICLINAL CURVES, UNCON- 

 FORMABLE STRATIFICATION, AND WASTE PRODUCED BY 

 CHEMICAL ACTION. 



I MUST now more precisely explain the meaning of a 

 few terms which I have already employed, and shall have 

 occasion to use very frequently. 



Denudation, in the geological sense of the word, 

 means the stripping away of rocks from the surface, 

 so as to expose other rocks that lay concealed beneath 

 them. 



Eunning water wears away the ground over which it 

 passes, and carries away detrital matter, such as pebbles, 

 sand, and mud ; and if this goes on long enough over 

 large areas, there is no reason why any amount of 

 matter should not in time be removed. For instance, 

 we have a notable case in North America of a consider- 

 able result from denudation, now being effected by 

 the river Niagara, where, below the Falls, the river 

 has cut a deep channel through the rocks, about seven 

 miles in length. The proofs are perfect that the Falls 

 originally began at the great escarpment at the lower 

 end of what is now this gorge : that the river, falling 

 over this ancient cliff, by degrees wore for itself a 

 channel backwards, from two hundred to a hundred 

 and sixty feet deep, through strata that on either side 

 of the gorge once formed a continuous plateau. 



