Triassic Formation of the Connecticut Valley. 427 



source — has acted in the Ranges on some portion of the earth's 

 crust beneath the immediate surface ; and the upper strata, by 

 continually adapting themselves, under gravity, to the inequal- 

 ities of the lower, have assumed the forms we see. Such a 

 hypothesis, assigning to subterranean determination the position 

 and direction of lines of uplift in the Range system, and 

 leaving the character of the superficial phenomena to depend 

 on the character and condition of the superficial materials, 

 accords well with many of the observed facts, and especially 

 with the persistence of ridges where structures are changed." 

 The essential peculiarities of the method for the production of 

 a faulted monocline is here clearly stated, although no oppor- 

 tunity is noted for independent verification of the suggestion, 

 ,such as appears in Connecticut in the correspondence between 

 the course of the faults and the trend of the underlying 

 schists. 



In my previous paper concerning the origin of the faulted 

 monocline, no special consideration was given to the cause of 

 the discordance between the course of the faults and the strike 

 of the beds in the Meriden region, which now appears as so 

 strong a structural characteristic. It may be suggested that 

 this is the result of a force of compression acting on the whole 

 mass of crystalline and overlying rocks in a direction oblique 

 to the strike of the schists, whose structure determines the 

 course of the faults. The schists trending northeast and the 

 compression being exerted from west to east so that movement 

 of any point in the schists must take place in an east and west 

 vertical plane, a result such as that which here obtains might 

 be produced. A consequence of this would appear in the 

 much greater uplift given to the southwestern than to the 

 northeastern part of any block thus obliquely tilted ; but the 

 unworn surface of any block would slope eastward, in the 

 direction of the dip of its beds. When deeply eroded, the 

 older members of the series of tilted beds would be revealed 

 in the southwestern part of the block ; while the newer still 

 remain in the northeastern part, as we find them. 



The topographic development of the Meriden region and 

 indeed of the valley as a whole, may be briefly sketched. Its 

 early structural topography, such as would have resulted from 

 its dislocation without erosion, finds modern illustration in the 

 tilted lava blocks of Southern Idaho, as described by Russell. 

 This writer, from whose vivid descriptions we derive so clear 

 a picture of our western country, says that the whole of the 

 Great Basin — the "immense region lying between the Sierra 

 Nevada and the Rocky Mountain systems has been broken by 

 a multitude of fractures, having an approximately north and 

 south trend, that divide the region into long, narrow, oro- 



