426 W. 31. Davis — Topographic Development of the 



of the main trap sheet. Lamentation Mountain is on the right 

 with the slightly detached Chauncy Peak rising a little over 

 its farther end ; and Higby (Besick) Mountain rises on the left. 

 The strong fault that passes a little east of Meriden separates 



Higby a»o Lamentation Mountains. 



these two mountains, while the greater fault which runs west 

 of Meriden cuts off the north end of Lamentation. The view 

 of these mountains is highly suggestive. 



The extension of the faults to the northeast and southwest of 

 the trap ridges is seldom traceable very far. Southwest of the 

 anterior trap ridge, the country is generally soon covered with 

 drift ; but occasionally certain beds of conglomerate serve to 

 indicate the course of a fault, as is the case with the great 

 fault between the Hanging Hills and Lamentation Mountain, 

 which may be followed two miles southwest of Meriden. To 

 the northeast, the occurrence of a second posterior ridge in 

 certain localities may in time serve to unravel the fault lines, 

 as it has already for the fault between Chauncy Peak and Higby 

 Mountain, which is thus traced about three miles to the north- 

 east of the gap that it produces in the main sheet. All these 

 localities are given in detail in the itinerary of the summer 

 school, as above. 



The systematic arrangement of the faults in this district, 

 already mentioned in earlier papers, is thus confirmed. When 

 this is once perceived, it is evident that the normal sequence of 

 the Triassic beds can be found only by crossing the monocline 

 obliquely to the northeast, always keeping within the limits of 

 a single fault-block. This seems to me to be the key to the 

 structure of the region. The remainder of this paper is 

 occupied with considerations not discussed in the Bulletin. 



The mechanism suggested to account for the production of 

 a monocline with its system of faults thus arranged has been 

 in the mind of other writers. Some fourteen years ago, Mr. 

 G. K. Gilbert conceived its essential features, and gave a brief 

 account of it in his description of the Great Basin Panges.* 

 He made the theoretical suggestion "that in the case of the 

 Appalachians, the primary phenomena are superficial ; and in 

 that of the Basin Ranges they are deep-seated, the superficial 

 being secondary ; that such a force as has crowded together 

 the strata of the Appalachians — whatever may have been its 



* Wheeler's Surveys west of the 100th Meridian, iii, 1875, 62. 



