264 GEOGNOSY OF THE APPALACHIANS. [XIII. 



of the Tremadoc slates,* which are considered equivalent to 

 the Levis formation. 



"We have seen that, according to Logan, a dislocation a little 

 to the north of Lake Champlain causes the Quebec group to 

 overlie the higher members of the Champlain division. The 

 same uplift, according to him, brings up, farther south, the 

 Red sand-rock of Vermont, which to the west of the disloca- 

 tion rests upon the upturned and inverted strata of various 

 formations from the Calciferous sand-rock to the Utica and 

 Hudson River shales. These latter, according to him, are seen 

 to pass for considerable distances beneath nearly horizontal 

 layers of the Red sand-rock, the Utica slate, in one case, hold- 

 ing its characteristic fossil, Triarthrus Beckii. This relation, 

 which is well shown in a section at St. Albans, figured by 

 Hitchcock,f was looked upon by Emmons and by Adams as 

 evidence that the Red sand-rock was the representative of the 

 Medina sandstone of the New York system. When, however, 

 the former had recognized the Potsdam age of the sand-rock, 

 with its Olenellus, which he supposed to be Paradoxides, this 

 condition of things was conceived to be an evidence of the 

 existence beneath the Potsdam of an older and unconfonnable 

 fossiliferous series already mentioned. 



The objections made by Emmons to Rogers's view of the 

 Champlain age of the Taconic rocks were threefold : first, the 

 great differences in lithological characters, succession, and thick- 

 ness between these and the rocks of the Champlain division 

 as previously known in New York ; second, the supposed un- 

 conformable infraposition of a fossiliferous series to the Pots- 

 dam ; and, third, the distinct fauna which the Taconic rocks 

 were supposed to contain. The first of these is met by the 

 fact, now established, that, in the Appalachian region, the Cham- 

 plain division is represented by rocks having, with the same 

 organic remains^ very different lithological characters, and a 

 thickness tenfold greater than in the typical Cham plain region 

 of northern New York. The second objection has already 



* Quar. Geol. Journal, XIX. p. 36. 

 t Geology of Vermont, p. 374. 



