322 /. D. Dana on American Geological History. 



and twenty miles in the Connecticut valley : and similar strata 

 occur in Southeastern New York, in New Jersey, Yirginia, North 

 Carolina and Nova Scotia. These long valleys are believed to 

 have been estuaries, or else river courses. 



The period of these deposits is regarded as the earlier Juras- 

 sic by Professor "W. B. Kogers. Dr. Hitchcock supposes a por- 

 tion of the preceding or Triassic Period to be represented.* 



Many of the layers show, 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 

 Yirginia, 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 

 region ? Is it not clear that these old valleys, occurring at in- 

 tervals from Nova Scotia to South Carolina, originally made by 

 foldings of the earth's crust, were still sinking ? 



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 be- 

 neath and the overlying sandstone, constitutes the trap moun- 

 tains, ridges, and dykes, thickly studding the Connecticut Yalley, 

 standing in palisades along the Hudson, and diversifying the 

 features of New Jersey and parts of Yirginia and North Caroli- 

 na. The trap is a singularly constant attendant on the sandstone, 



* This Red Sandstone, after being known for a while under the name of " Old Red 

 Sandstone," was long called the " New Red Sandstone," it being shown to be above 

 the carboniferous system. The first step towards a nearer determination of its age 

 was made by Mr. J. H. Redfield in a paper on the Fossil Fishes of the Connecticut 

 yalley published in 1836, who made it Jurassic (Lias or Oolitic), (Ann.Lyc. 38". Hist. 

 N. Y., vol. iv.) Mr. W. C. Redfield added to the facts bearing on this conclusion 

 through discoveries made in New 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 Cypridae in North Carolina, in each of the belts in Virginia, 

 in the belt in Pennsylvania near Phenixville, and one plant (Lycopodites Williamso- 

 nis) common to Virginia and Massachusetts, he suggested that all the beds were 

 probably Jurassic (Am. J. Sci. [2], xix, 123). Mr. E. Hitchcock, Jr., detected re- 

 cently a fossil plant (Clathropteris rectiusculus, Am. J. Sci. [2j, xx, 22), near the 

 middle of the sandstone formation in Massachusetts, and remarks that it indicates 

 the existence of the Lower Jurassic at that place, and also renders it probable that 

 the Triassic may be represented in the inferior beds, as is sustained by Prof. Hitch- 

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

 North Carolina, (communicated to the Amer. Assoc. at Albany in August last,) which 

 are related to those of the Triassic and Jurassie 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. 



