56 



RELATIONS OF THE TACONIC 



Whitehall iiiountain, so thai all doubt in icgarcl to its position and relation is removed by 

 direct inspection. 



The diagram in Fig. 2 illustrates the. position and relations exhibited at Whitehall. 



Fig:. 2. 



a, a. Easterly prolongation of the mountain, which is surmounted by the Calciferous sandrock ; b, b. Tertiary clay; 

 c, c. Taconic and black slate ; rf, d. Calciferous sandstone, unconformable to the Taconic slate, and dipping 

 southeast at an angle of 10-45 degrees. 



From this exposition, no one can doubt ihc wide difference in age between this slate and 

 those of the Hudson river ; the former being below the oldest members of the New-York 

 system, while (he latter rest conformably upon the middle members of the Champlain 

 division. The Taconic or black slate, the newest mendier of the Taconic series, was not 

 only deposited anterior to (he other under consideralion, but wtis dislurl)ed or removed 

 from the horizontal position; and its deposition and tlisturbance seem to mark the close of 

 one geological period of great duration, if we may judge from the united thicltness of the 

 rocks belonging to it. 



Another section (Fig. 3) , differing l)ut little in detail from the preceding, but exhibiting 

 more fully the relations of these systems, is annexed. 



Fig. 3. 



Near a church three miles east of Whitehall, is a deep ravine in which the Taconic slate, rf, d, is denuded; ' 



a, a. Calciferous sandstone. 



Another section (Fig. 4) , passing through the slates and shales of the Hudson river as 

 well as the Taconic slates, is taken from the hills of Greenbush opposite the city of Albany. 



Fig. 4. 



a. Tertiary clay ; b. Hudson river shales ; c, c. Taconic slate ; d. Calciferous sandstone. 



Passing east from the ft^rry, the first rocks are the shales of Hudson river, overlaid by tertiary 

 clays: these continue to the Red mill. Leaving the mill, the rocks are concealed till we reach 

 the summit of a low range of hills bordering the eastern side of the valley of the Hudson. 



