PARALLELISM OF THE QUEBEC GROUP. 35 



About twenty-five miles further south, at the small promontory- 

 called Sharp-shins, or Lone-rock Point, at Burlington, a formation of 

 limestone, which appears to belong to the Potsdam, is seen resting 

 on black slate, the contact being visible. In the debris of bro- 

 ken slate, at the foot of this cliff, the Rev. Mr. Perry found some 

 imperfect fossils. Among these I recognized a fragment of Con- 

 ularia, and the punctured border of the head of a Trinucleus, 

 As the fossils were found loose, the age of the slates is not deter- 

 mined palseontologically. But I have shown (Am. Jour. Sci., 2d 

 Sep., Vol. 33, p. 102) that the underside.of the limestone, or the 

 surface of it which is in contact with the slate, is smoothed, and 

 presents very much the appearance of slickensides. There are 

 thus at this place also indications of a dislocation. 



At Buck mountain, still further south in Vermont, I have also 

 shown (Soc. Cit., p. 103) that the Potsdam is brought up by a 

 fault (with an upthrow on the east side) against the Chazy and 

 Black River. I think the limestone at the north end of this 

 mountain belongs to the Quebec group. 



At Snake mountain, about a mile further south, the Potsdam has 

 about 700 feet of black slate below it. But as the undoubted 

 Chazy limestone is seen at the foot of the hill, apparently plung- 

 ing under the slate which supports the Potsdam, there must in- 

 evitably be here (as Dr. Emmons has long held) one or more 

 great faults. No fossils have been found in the slates at this 

 locality, i.e., in those that have the Potsdam above them. 



All the evidence, both physical and palasontological, thus far 

 collected, seems to show that (in the disturbed region of the south- 

 eastern portion of the palaeozoic basin of North America) when- 

 ever the Potsdam, with its primordial fauna, appears to overlie 

 rocks holding the types of the second fauna, there will be found 

 some evidence of a great fault, often with an overlap, by which 

 the older rocks are not only brought up to a level with the newer? 

 but even shoved over them. This solution of the great problem, 

 which for twenty years has been so much discussed by American geo- 

 logists was first brought out by Sir W. E. Logan, in Dec, 1860, and 

 all the new facts ascertained since then, along the line of the 

 fault, prove that it is the only true one that has yet been ad- 

 vanced. 



