124 CHAMPLAIN DIVISION. 



from any other slate, of a distant formation. It is only by position, and its fossils, that it 

 can be recognized. Its fragile character is quite worthy of notice ; as by its inability to 

 withstand the combined action of water and frost, it is constantly passing into soil. This 

 is especially the case if broken and raised from its beds. Under these circumstances, it 

 forms an argillo-calcareous soil of the best character. 



This mass is well developed in the valley of the Mohawk ; but in the Champlain and 

 Hudson, it is very imperfectly known. In the vicinity of Glensfalls and Sandyhill, it is 

 easily recognized in its place above the Trenton limestone. It skirts the valley of the 

 Hudson at Miller's falls ; but in this range, especially upon the east side of the valley, it is 

 concealed ainong the shales, and so much altered by pressure and other disturbances that 

 it is by no means clearly defined. It may be studied in the gorges of Loraine in Jefferson 

 county, where it may be seen in its inferior and superim- connections. Its tliickness is not 

 less than seventy-five, nor over one hundred feet. In obtaining this estimate, I have been 

 guided by the distribution of the Triarthus beckii, and the lithological character of the rock. 

 There is less siliceous matter in the mass, which has received the appellation of Utica slate. 



§ 8. Loraine shales. 



The incorporation of the Utica slate with the shales of this section, may be well observed 

 in the deep gorges of Jefferson and Lewis counties. A band of slate, quite fossiliferous, 

 lies at the base of the shales, which is usually considered the superior part of the Utica slate. 

 Within a few feet of this band, I have found the Pterinea carinata, which is one of the 

 characteristic fossils of the shales. The shales are composed of alternating beds of slate in 

 this mass in New-York, similar to the Utica slate, and thin siliceous beds, which become, 

 in the superior portion, thick beds, with far less interposed shale. It forms, strictly speak- 

 ing, thin and thick-bedded sandstones, of which the thick beds were deposited last. 



The distribution of the fossils in this mass is worthy of notice. Proceeding from the 

 fossiliferous band of the Utica slate, the fossils diminish rapidly, so that in the middle and 

 inferior parts of the Loraine shales very few fossils exist ; while at the upper portion the 

 mass becomes highly charged witli organic bodies, though distributed more abundantly 

 through calcareous bands. But then they diminish again ; and when the thick-bedded 

 sandstone appears, they cease, with few exceptions. This peculiar distribution, and the 

 confined limits of the fossiliferous beds, render the recognition of these shales, when they 

 lie in proximity to the Taconic system, quite clifficidt ; still, by careful examination for 

 the thin fossiliferous bands, doubts may be usually reiuoved. I say careful examination, 

 for a careless observer would jjrobalily pass over some highly fossiliferous strata without 

 recognizing them, in consequence of tlieir obliteration outwardly ; and it is only where the 

 stratum is broken in the disturbed part of tlic formation, that they can be observed. 



In describing this rock, it is hardly possible to separate the thick-bedded mass at the 

 superior part, from the Loraine shales proper : there is a perfect transition of one into the 



