278 Remwrks on the Taoonio System. 



sharply upon the primary ; the valley is wide, swelHng with 

 knobs and ridges of gravel and drift; marbles and limestones 

 underlie the surface; the springs flow with hard wcUe?', or hold 

 carbonate of lime in solution ; a new order of agriculture greets 

 his vision ; the whole scenery is changed, a change that did 

 not escape the observation of Prof. Hopkins and of President 

 Dwight, when they first travelled into this region. 



From the Konkeput on to the Hudson river he passes over 

 five of these parallel mountains, all having the same peculiari- 

 ties, and three of the valleys filled with limestones. The lime- 

 stones of the valleys, the slates and quartz of the mountains 

 have all of them, for more than thirty miles in width of territory, 

 the steep tilt eastwards. 



At the crossing of the Claverack creek in Columbia county, 

 quite to his surprise he finds a limestone capping the highest 

 slate hill. 



It is conceded by all geologists that the mountains of the 

 American continent have been elevated at diflerent geological 

 periods ; that the continent has undergone repeated oscillations, 

 and that the dynamics elevating the continent have been dif- 

 ferent from those uptilting the mountains. 



Pres. Hitchcock describes six systems of elevations in the 

 State of Massachusetts. Ti\Q fourth in his system is that which 

 elevated these mountains, but in the order of nature it was the 

 second^ for the Silurian rests unconformably to the slates of 

 these mountains, while these slates are unconformable to the 

 primary. They were upheaved, then, before the laying down 

 of the Potsdam sandstone, and after the close of the Taconic 

 epoch. 



The upheaving iovce fractured these rocks simultaneously in 

 two different directions, one longitudinally in long lines of from 

 five to thirty miles, and elevated them many thousand feet, as 

 we may reasonably suppose. This elevating force threw them 

 not up in folds of the strata, as the brothers Kodgers have 

 stated, but in sharp lines of fracture bringing all the strata sue- 



