1846.] The Taconic System. 205 



The relations of the newer members of the Taconic system M'ere 

 then ilhistrated by a series of diagrams, which, as they were taken 

 from observation, showed very clearly the fact that the older mem- 

 bers of the New York system of the Champlain division repose 

 directly upon the Taconic slate, or some other member of this 

 system. 



Many instances of superposition were cited, and so well estab- 

 lished is this statement, that it is admitted by those who reject the 

 views of Dr. E. ; but in order to avoid the inference which must 

 necessarily follow, it is maintained that the rocks have been over- 

 turned, and that the so called Taconic slate is merely the Hudson 

 river slate, or shale slightly altered, having the lower limestone 

 reposing upon it in an inverted position. This is considered in- 

 consistent with the facts on the ground, that there is not only su- 

 perposition, but succession; that the succession in the instances 

 referred to is similar to the succession that everywhere prevails 

 in the Champlain division, namely, first, the Potsdam sandstone, 

 or calciferous sandstone, birdseye, &c. ; and then Trenton lime- 

 stone and its slate. A careful examination of the localities proved 

 the succession contended for, and that the principal change of 

 position which the rocks have undergone, is merely an elevation, 

 or uplift, and the nature of this change was illustrated by refer- 

 ence to the falls of Montmorenci, where a force was evidently 

 applied below the gneiss, which brought up that rock, supporting 

 the whole of the Champlain division in the order in which the 

 members were deposited. Uplifts of this character, extend from 

 the Highlands of the Hudson to Montmorenci, and in no case are 

 the rocks turned over, but they always appear in their tnie suc- 

 cession, and in many instances with two and three hundred feet 

 of Taconic slate beneath. This fact goes to show where the line 

 of demarcation between the Taconic and New York system should 

 be drawn. 



Dr. Emmons here alluded to the condition of the rocks in the 

 valley of the Hudson river, where the shales are comparatively 

 largely, and the limestones of the Champlain division are but 

 feebly developed; which causes much obscurity in regard to their 



