256 ANNUAL OF SCIENTIFIC DISCOVERY. 



These strata mark the existence of a vast ocean, the shore of which 

 was along- the Atlantic coast. He saw, however, no reason to infer 

 that the Western deposits were deep-sea deposits, as the existence of 

 Echinoderms and fossil corals which live in water of moderate depth 

 would indicate the contrary. He thought that many of the Eastern 

 deposits would be reduced to one epoch, for if at the present time we 

 suppose an elevation of the sea-shore for a few feet, there would be a 

 succession of strata of various compositions similar to those referred to. 

 Prof. Rogers said that he considered the New York and Pennsylva- 

 nia beds of limestone to be of littoral origin, their outlines becoming 

 confused and blended on going west, until in the district of Cincin- 

 nati they come in contact with the overlying clay, which in the East 

 is separated from it, making one common mid-sea deposit of limestone. 

 This is shown by the diminishing size of the pebbles and the thinning 

 of the layers as they recede from the East. In a similar way the pa- 

 leozoic horizons become confused towards the West. The deposits 

 which overwhelmed the animals of the East did not reach the West, 

 and they continued to live, so that inhabitants of different strata at the 

 East occur together at the West. Thus, where there was a layer of 

 thick mud in the East, there is found in the West a deposit of thin clay, 

 forming shales interposed in the limestone. The attempt, therefore, to 

 identify the paleontological character of the deposits of different seas, 

 is unphilosophical. Prof. Rogers also inferred, from various facts which 

 he had observed both east and west of the Alleghanies, and which he 

 connected with the changes consequent upon the subsidence of a sea 

 from the Atlantic slope and from the Western valley, that a continent 

 once occupied the place of the present Atlantic, and that North Amer- 

 ica was then a sea ; and it was evident that precisely the same races 

 did not exist, at the same time, on the east and west sides of that con- 

 tinent. He contended, therefore, for the renunciation of the European 

 nomenclature and classification. 



PHYSICS OF THE MISSISSIPPI RIVER. 



THE American Railroad Journal publishes a memoir on " the phys- 

 ics of the Mississippi River," by C. G. Forshey, from which we ex- 

 tract some of his results. The mean depth of the river at high-water- 

 mark is not materially different at Natchez from what it is at Carroll- 

 ton, though nearly 300 miles apart. A section of the river at Car- 

 rollton, made at high water of 1849, is 168,226 square feet; and at 

 Vidalia (opposite Natchez) the section is 167,000 feet. The bottom 

 of a uniform channel 400 miles up is about on a level with the bar at 

 the Southwest Pass. The rate of fall is not uniform on the surface, 

 but decreases in declivity towards the Gulf, giving a curve of inclina- 

 tion (probably parabolic) to which the Gulf level is a tangent, at the 

 Balize. The mean rate of inclination is 1.80 inch per mile, for the first 

 hundred miles, 2.00 inches for the second hundred, 2.30 inches for the 

 third, and 2.57 inches for the fourth hundred miles. The low-water 

 curve of declivity has a mean descent of .24 inch per mile for the first 

 hundred miles, and .50, .83, 1.20 inch for the next consecutive three 



