190 GEOLOGY OF THE SECOND DISTRICT. 



a fine natural section of tlie strata : they have a dip first to the south, which changes to tlie 

 west and northwest, but it is only slight, and the lowest strata that can be observed arc only 

 a few rods below the bridge. The above view of these falls was taken from the north side, 

 about twenty rods below the bridge, or at that point where they are the most distinct when 

 seen beneath it. 



It will be a repetition of what has already been said, that most if not all of our falls are 

 produced by uplifts of the rock ; and I make the repetition merely to call the attention of 

 observers more to this fact, as it brings out fully and clearly the truth of the assertion that 

 these phenomena are principally due to geological causes. We are not aware how great and 

 liow extensive have been the operations of certain agents in the production of all such changes 

 upon the earth, and how much they diversify the physical features of our landscapes. In 

 order, therefore, to understand physical geography, the elements of geology, at least, become 

 essential ; as without them, we are deficient in some important items of knowledge. 



The slight break in the limestone at Glen's falls is an interesting fact ; for, from examina- 

 tion, it seems to be due rather to a wave communicated to the crust, than to a more direct 

 application of force beneath ; an oscillation, or wave which was communicated at the time the 

 great fracture of the Hudson river slates took place. Some facts confirmatory of this view 

 will be related when I speak of the limestone of Essex county. ' 



