440 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



All of Ibcm arc older, and much older; some of them go back as 

 far ill time as the upthro-vv of primreval rocks. 



The drift mantle covers the valleys as well as the hill slopes 

 and hill tops. It is itself composed of material supplied from 

 previous denudation and removal — the very soil of the tertiary. 



What I conceive fo be the true explanation is the following: 

 Let us travel from the Highlands to the Catskills, along the Hud- 

 son from Dunderl^erg to Round top, and we shall get at the order 

 and succession of events sufficient for our theory. The Highlands 

 were the primary uplifts. Their strata was consolidated before 

 their fracture, hence they appeared above the Atlantic as bold, 

 jao-ged peaks, much higher than at present. In the upthrow there 

 were profound chasms and gulfs. Upon the north-east and south- 

 east there were shore lines. Immediately upon their emergence 

 from the waves, there commenced the process of degradation, 

 accomplished by all and the same chemical laws and atmospherie 

 ao-encies as at the present. From their ruins, the neighboring 

 shores were built up, and their profound chasm filled; hence we 

 have the slates, and the sandstones which are found within them; 

 hence* the taconic rocks which lie upon their Hanks. Their sum- 

 mits wei-e lowered, their fissures widened, and the borrowed mate- 

 rial transported to build up the succeeding formation. 



In the lapse of time, the next succeeding uplift took place, which 

 carried the highland higher, and brought up the hills of New 

 Marlborough, and Westchester county, northward along the Hud- 

 son; this action reached to the Wallkill, and southwards to Staten 

 Island. This uplift was attended with fracture and contortion of 

 the softer taconic. They also came up in serrated and jagged out- 

 lines. Thev underwent the same process of degradation and remo- 

 val into the seas inland, to build up the silurian. With the eleva- 

 tion of mountains, there were corresponding valleys for drainage. 

 Each succeeding growth of the continent had its river and lake 

 system, as well as its shore line. 



In process of time the silurian suffered an elevation, in the Shaw- 

 angunk mountains, and these too had to suficr the same process to 

 help build up the Mesosoic, which was deposited upon the shore 

 line south of the Highlands. The southern rim of the devonian 

 was elevated by the Shawanguuk uplift, but not its interior. 

 Each in turn has helped to form the next succeeding geologic 

 formation, but the oldest most of all; hence our primary are our 

 lowest mountains. The devonian help build the carboniferous; the 



