88 PALJIONTOLOGY OF NEW-YORK. 



IVOTE C— (S€e Page 70.) • 



This process of the subsidence of the sea-bottom when loaded by accumulating 

 sediments, is clearly recognized by Herschel in his explanation of the rising of 

 Scandinavia, which he says may be caused by the accumulation of sediments on the 

 adjacent ocean bed; which, giving way beneath the pressure, will drive a portion 

 of the yielding matter beneath the adjacent continent, thus causing the elevation. 

 This process of depression at one point and elevation at another by the yielding 

 mass beneath, doubtless offers an explanation of many phenomena both of recent 

 and more ancient geological times. I have shown in the preceding pages that the 

 strata comjxjsing the Lower Helderberg group, and to a great extent the Oriskany 

 sandstone also, follow a line parallel to the Appalachian chain, and do not extend 

 far to the westward : at the same time it is shown that there had been a movement 

 in the accumulated sediments of prior date, and these beds lie unconformably above 

 the inclined beds of the Hudson-river rocks below. The depression of the accumu- 

 lated matter along the axis of the Appalachians, displacing the yielding masa 

 beneath, would cause an elevation or bulging of the ocean bed on the western side, 

 which, at the distance of a hundred miles, might have risen so near to the surface 

 as to prevent the accumulation of sediments; while the slope of gradually deepening 

 waters towards the present mountain range would allow the formation of just such 

 a set of strata as we now find, having their thickening edges towards the east, while 

 they gradually thin out on the west. 



WOTE ». 



From the study of the palsezoic formations in the Appalachian chain, and their 

 distribution over the great plateau of the West, wo discover why it is quite 

 impossible to have uniformity in the nature of the strata, or in the conditions of 

 the surface. The coiulilioiis accompanying the transportation and deposition of the 

 sediments which took place along the lines which now mark the mountain chain, 

 were very different from the conditions attending the accumulation on either side. 

 We see that the mountainous region is mountainous, not from the folded and 

 plicated condition of the beds constituting the mass, but because of former ac- 

 cumulations of matter. The metamorphic condition is simply the result of the 



