Southwestern New England Region. 439 



radiating cross sections a knowledge of the true order of bed- 

 ding."* 



There have been few geologists more thorough and con- 

 scientious than Raphael Pumpelly, and the realization of the 

 danger of inferring faults is perhaps a characteristic of all the 

 best American geologists of the recent past and of the present 

 alike. It ought, however, to be pointed out that the danger 

 of inferring faults where they are absent, is hardly more serious 

 than that of assuming their absence where they are present. 

 The present attitudes of the rock beds must be accounted for 

 either by the one or the other kind of deformation or by the 

 two in conjunction, and these attitudes can in most cases of 

 difficult areal geology be accounted for upon either theory. It 

 is also worth noting that the edge of a ridge which shows 

 many "bay-like curves" is just the kind most likely to be 

 caused by a series of parallel and intersecting faults ; and the 

 presence of folds with pitching axes, while offering a possible 

 and perhaps adequate explanation for the alternation of forma- 

 tions in the direction of their strike, does not necessarily reveal 

 the real or the only actual cause. 



This assumption of the absence of faulting throughout the 

 New England area has been fundamental and far-reaching in 

 the work of the Survey, as is shown by the fact that in the 

 area of 200 square miles mapped with great detail and described 

 in the report cited, but a single fault is indicated, and this a 

 strike fault, presumably an overthrust. As the work has been 

 extended to the south the same tendency to resist the tempta- 

 tion to locate faults has been manifest, and from his own 

 experience the writer can testify that in twelve seasons of 

 independent field work, or until the Pomperaug Valley area 

 of Newark rocks was examined, not a single normal fault was 

 entered upon his maps. It is believed that the tendency has 

 been hardly less marked in the work of other members of the 

 division, and it might almost be added, for the most careful 

 work upon the crystalline schists throughout the country. 

 Indeed it would hardly be too much to say that structural 

 studies of the crystalline areas of the United States, with the 

 single exception of the Great Basin region, have been carried 

 out upon the assumption that rock deformation takes place by 

 one process only, namely, by crustal folding and the thrusts 

 incident to folding. Even in the classical area of the Great 

 Basin the attempt has recently been made, though unsuccess- 

 fully, to explain the structure by a system of folds alone. 

 This marked trend in American geological work may be in no 

 small measure due to the classical geological studies of the 



* Pumpelly, Wolff, and Dale ; Geology of the Green Mountains in Massa- 

 chusetts. U. S. Geol. Survey, Mon. xxiii, 7, 1894. 



