188 THE PHENOMENA OF DRIFT, OR 



This appearance results from a £2^rcat number of valleys of vari- 

 ous depths, running very nearly north and south, and almost 

 exactly parallel to one another. Of course, where the mountain 

 runs nearly east and' west, these valleys will cross it at right 

 ant^les. I formerly supposed these valleys to be the result of the 

 original structure, or mode of elevation, of the mountain. But 

 discovorin"- stria? and broad gi'ooves on the top of the ridge, es- 

 pecially along its northern edge, I was led to inquire whether the 

 valleys also might not have been the result of glacio-aqueous 

 acrency : and it occurred to me, that if they were, they would not 

 cross the ridge at right angles, as it curved so as to run almost 

 north and south ; but would retain their parallel, that is, nearly 

 north and south direction : whereas, if the result of original 

 structure, or elevation, they would probably cross the ridge at 

 right angles on all parts. An excursion along the top satisfied 

 me that they preserve their parallelism in a most remarkable 

 manner ; and that the slight deviations from it, where the valleys 

 run in nearly the same direction as the ridge, are such as to con- 

 firm, instead of invalidating, the supposition of their glacio- 

 aqueous origin. We there sometimes find a narrow ridge, termi- 

 nating on the north in a bold but rounded front, which appears 

 as if it had been powerfully acted upon by a force which was 

 not sufficient to remove it, and was, therefore, obliged to urge its 

 way on either side, so as to form t^vo narrow valleys a little 

 diverging from the main one. The northern extremity of some 

 of these bluffs of trap is arranged somewhat like steps, and re- 

 minds one of Berzelius's description of the northern extremities 

 of mountains in Sweden, which resemble sacks of wool piled 

 one upon another. 



The depth of these valleys varies from a few feet to several 

 hundred. Through one of them Connecticut river passes ; and 

 its bed is more than eight hundred feet below the ridges that rise 

 on either bank very precipitously, and exhibit striip and rounding 

 from top to bottom. But I have ascertained that this gorge was 

 in part produced by a fault running across the sandstone in this 

 place, whereby it suffered a depression where the river runs ; so 

 that we cannot suppose that glacio-aqueous action wore down 



