416 Oil American Geological History. 



Many of the layers sliow, by their shrinkage cracks, ripple- 

 marks, and footprints, as others have observed, that they were 

 formed in shallow waters, or existed as exposed mud-flats. But 

 they accumulated till they were over a thousand feet thick in 

 Viro-inia, and in New England two or three thousand, according 

 to the lowest estimate. Hence the land must have been sinking 

 to a depth equal to this thickness, as the accumulation went on, 

 since the layers were formed successively at or near the surface. 



Is it not plain, then, that the oscillations, so active in the Ap- 

 palachian revolution and actually constituting it, had not alto- 

 gether ceased their movements, although the times were so quiet 

 that numerous birds and reptiles were tenants of the Connecticut 

 reo'ion ? Is it not clear that these old vallevs occurrinor at 

 intervals from Nova Scotia to South Carolina, originally made by 

 foldino-s of the earth's crust, w^ere still sinkino^ ? 



And did not the tension below of the bending rocks finally 



cause ruptures ? Even so : and the molten rock of the earth's 



interior which then escaped, through the crystalline rocks beneath 



and the overlying sandstone, constitutes the trap mountains, 



-rido-es, and dykes, thickly studding the Connecticut Valley, 



shown to be above the carboniferous system. The first step towards a 

 nearer determination of its age was made bv Mr. J. H. Redfield in a paper 

 on the Fossil Fishes of the Connecticut valley published in 1836, who made 

 it Jurassic (Lias or Oolitic,) (Ann. Lye. N". Hist. N. Y., vol. iv.) Mr. "W. 

 C. Redfield added to the facts bearing on this conclusion through discoveries 

 made m I^ew Jersey and Virginia. Prof W. B. Rogers deduced from the 

 coal plants of the Richmond beds, the same age for those beds, while ad- 

 mitting that other beds of the sandstone might be Triassic. Afterwards on 

 finding the same Posidonia and Cyprida3 in ]^orth Carolina, in each of the 

 beds in Virginia, in the belt in Pennsylvania near Phenixville, and one plant 

 (Lyeopodites Wilhamsonis) common to Virginia and Massachusetts, he 

 suggested that all the beds were probably Jurassic (Am. J. Sci. [2..] six, 

 123.) Mr. E. Hichcock, Jr., detected recently a fossil plant {Clathropterh 

 recthisculus, Am. J. Sci. [2,] xx, 22,) near the middle of the sandstone forma- 

 tion in Massachusetts, and remarks that it indicates the existence of the 

 Lower -iurassic at that place, and also renders it probable that the Triassic 

 may be represented in the inferior beds, as is sustained by Prof. Hitchcock. 

 Prof. Emmons has recently obtained Reptilian Fish, and Molluscan fossils 

 in JS'orth Carolina, (communicated to the Amer. Assoc, at Albany in August 

 last,) which are related to those of the Triassic and Jurassic periods. The 

 amount of evidence as far as now understood therefore tends to sustain the 

 view that the Period of the sandstone, while it may cover part of the 

 Triassic, is mainly Jurassic. 



