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being manifestly an insulated remnant of the sandstone, Forma- 

 tion I., of the Appalachian series. 



Composition and Structure. — The formation we are describing 

 embraces two principal members, which preserve their respective 

 characters with very great uniformity. The lowest of these, 

 which reposes sometimes on the primary rocks at the foot of 

 the adjoining hills, sometimes on the lower strata of the older 

 secondary series, originally forming the bed of the valley, is a 

 conglomerate easily recognised. This rock consists of a rather 

 fine-grained compact red sandstone, occasionally argillaceous, 

 imbedding rounded, water-worn pebbles of various dimensions, 

 generally coinposed of white quartz. When these pebbles are 

 large and diversified in their colour and composition, as happens 

 in certain beds, and when the paste is less abundant and more 

 argillaceous than usual, the whole mass possesses a considerable 

 resemblance to the less calcareous varieties of the Potomac 

 marble. Bowlders of a rock having these features lie strewed in 

 great numbers in many parts of the red sandstone region east of 

 the Highlands, extending as far as the Hudson, and traceable to 

 this stratum of the Green Pond Mountain. 



In the inferior beds, the character of the rock is somewhat dif- 

 ferent; being in many places almost white, and consisting chiefly 

 of a white sandstone, thickly studded with white quartz pebbles. 

 These layers are conspicuously seen in the outlying low hills, 

 near the southern termination of the Green Pond Mountain ; they 

 are also visible at many other points, as, for example, ten miles 

 north of Macapin Pond. Their contiguity to a tract of white sand- 

 stone of the older series. Formation I., suggests this rock as the 

 probable source of the arenaceous materials of these beds. We 

 thus find in this, as in other formations, that the lowermost layers 

 are derived from the more immediately adjacent rocks, being 

 deposited during the first influx of the currents, before time had 

 elapsed for the introduction of the sediments from more distant 

 quarters. Ascending a little, the beds of the lower part of the con- 

 glomerate become progressively more tinged with the red matter, 

 so prevalent throughout the higher portions of the formation. 



The other division of the formation overlies the former, and 

 is a compact argillaceous red sandstone, much resembling the 

 firmer varieties of the red shale of the district east of the 



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