61 JOURNAI^ OP' THE 



coid or hydro-micaceous; and very often they may be bet- 

 ter described as cong-lomerate slates, being- composed of 

 flattened and differently colored soft, slaty fra«-ments of 

 all sizes, from minute particles to an inch and more in 

 diameter. '• "'■ '■ * ^' In Montgomery county, in a 

 very heavy ledg'e of siliceous slates, occurs a siliceous con- 

 g-lomerate, which is filled for hundreds of feet with very 

 sino-ular siliceous concretions, some of which Dr. Em- 

 mons has described under the name of Paleotrochis; but 

 the rock for several miles, as well as at this particular 

 locality, contains a multitute of rounded and ovoid 

 masses from the smallest sizes to that of a hen's egg' 

 showing the w de prevalence of conditions favorable to 

 the operation of concretionary forces. " " ^' The tal- 

 cose, siliceous, chloritic slates are more abundant towards 

 the base of the series, the east side, and the clay slates 

 predominate on the west." 



He also mentions the occurrence of beds of pyrophyl- 

 lite, and the abundance of quartz veins. The strike is 

 given. as northeast, and the dip prevalently west at steep 

 angles. 



"The belt is bounded on both sides by the Laureutian, 

 on which it lies unconformably, and from which its ma- 

 terials were derived. The stratigraphy therefore indi- 

 cates the horizon of these rocks to be the Huronian, and 

 lithology iigrees with that determination."^ 



RESULTS OP MORE RECENT PETROGRAPHIC STUDIES. 



T/ic Slates cuid Schists. One of the results of the late 

 geological work in this belt has been to identify at least 

 the argillaceous, sericitic, and chloric schists and slates 

 with those of Emmons' Taconic and Kerr's Huronian. 

 These rocks are termed schists, and again they are term- 

 ed slates. Certainly a great number of them have a true 

 slaty cleavage, while others are more truly schistose, i. e. 

 the laminae are not essentially parallel. These different 



1 Ibid, p. 133. 



