62 



OUTLINES OF GEOLOGY. 



issuing from this ridge Canada Creek forms Trenton Falls, 

 and the formation is opened to a great depth. To the north 

 of Trenton the formation extends to a great breadth, and 

 may be traced to the north-west across the St. Lawrence, 

 and into Canada. 



On the eastern side of the Highlands it is occasionally 

 found in small formations, which appear to have been divide 

 ed when that range was elevated, and it is found in detached 

 masses on its eastern slope. The red sandstone of the val- 

 leys of the Passaic and Hackensack, are often covered with 

 boulders of the transition limestone. 



149. The slate group is composed of the following rocks : 



Clay slate ; 



Roofing slate ; 



Silicious slate ; 



Talcose slate ; 



Calcareous slate ; 



Chlorite slate ; 



Micaceous slate. 

 Its upper layers alternate with the transition limestone, 

 and it is to be distinguished from the inferior order in many 

 cases, only by its rocks either containing fossils, or alternat- 

 ing with such as do. It is the lowest group in which any 

 trace is to be found of organized beings. 



150. The organic remains of this group appear to be si- 

 milar, if not identical, with those of the transition limestone. 

 Although its stratification is distinctly marked, the formation 

 by crystallization begins to play an important part. This is 

 apparent in the great number of imbedded crystals. Its stra- 

 tification is much disturbed, being frequently twisted and 

 undulating. It abounds in veins, and is among the forma- 

 tions most rich in the metals. 



