396' REPORT OF NATIONAL MUSEUM, 1904. 



libriating currents from the bed of the ocean, from reels, islands, and coasts, and 

 finally deposited from suspension over the great area where we now find it expo&ad 

 to observation. 



The probable cause of the elevation of the land he thought to be 

 secular refrigeration accompanied by contraction, whereby a gradually 

 accumulating tension was finally overcome by a yielding of the solid 

 strata, such being regarded as paroxysmal and productive of earth- 

 quakes. At the same time a sudden increase of the velocity of the 

 earth's rotation would result, and this in turn would increase the flow 

 of the ocean currents above mentioned. 



In attempting to account for the overturned character of the folds 

 in the mountain chains of the eastern United States, he seems to have 

 actually outdone the Rogers brothers in fecundity of ideas. He wrote: 



Paroxysmal elevation and the action of inertia offer a satisfactory explanation of 

 the folded axes and eastwardly dip. Suppose the sudden elevation of a mountain 

 mass one mile in height, or more distant from the axis of rotation than it was before 

 its elevation. It would still retain the linear velocity it had when a mile nearer the 

 axis of rotation, while the proper linear velocity at this increased distance would be 

 ;; ■ !]' "' miles, or 690 feet greater per hour than that which it had before its elevation. 

 Inertia would- therefore cause the mass at the top to press to the westward with a 

 force proportional to its mass and the above-mentioned velocity, and at intermediate 

 heights with a proportionally less momentum. If the strata he capable of yielding, 

 they must, when elevated in highly curved wrinkles, tend to fall over westward as a 

 consequence of the influence of inertia and the revolution of the earth from west to 

 east on its axis. 



Such a view from a man of Mather's training and at this late date 

 certainly seems extraordinary. 



Commenting further on the effects of centrifugal force, particularly 

 upon bodies of different densities, he argued that as such is greatest 

 under the equator, any subterranean force tending to elevate portions 

 of the earth's surface by their elastic tension would here be most 

 effective. In this way he would account for the supposed fact that 

 most of the highest mountains are found within the Tropics. Reason- 

 ing along the same lines, he conceived it possible that fractures might 

 be expected to develop in the direction of circles parallel to the equator 

 at a distance intermediate between it and the poles, where the curva- 

 ture resulting from the revolution of the earth would be greatest. 



In continuation of his work begun in 1832. T. A. Conrad in 1845 issued 



his volume on the Medial Tertiary formations, the general plan of the 



work conforming closely to those which we have already considered 



(pp. 306, 320, and 354). In this latter work he de- 



Conrad's Medial ., , . . 



Tertiary of North scribed these lormations as occupying a shallow but 



America, 1845. . ... ■£ 



very extensive depression in the Cretaceous rocks, the 

 most northern locality known being Cumberland County, New Jersey, 

 whence it extended southward in a very connected series, spreading 

 out over a large portion of the Atlantic seaboard. 



