Davis.] 122 [November 1, 



When therefore it is demonstrated and admitted that most of 

 the Connecticut Valley trap ridges are old overflows, they as- 

 sume a considerable importance in explaining the structure of the 

 enveloping sandstones, for they may be taken as horizons in the 

 sandstone series, easily followed and in some cases safely identi- 

 fied in their several faulted outcrops. So long as the trap was 

 considered intrusive, it could not serve thus as a guide; for if 

 intrusive it need not always break up between the sandstone 

 strata, but may sometimes have broken across them and so fail to 

 mark any single horizon : and so long as its general overflow ori- 

 gin has been neglected, the peculiar structure of the Connecticut 

 sandstones has not been correctly determined. 



Wherever the trap-sheets are known to be overflows, their 

 igneous origin may be neglected in the present inquiry, and they 

 may be considered as conformable members of the sedimentary 

 series; recognizable strata among the monotonous sandstones and 

 shales, and we may now return to the question, how are the faults 

 and folds determined ? 



The* most conspicuous example of a large fault is that one by 

 which the heavy trap sheet of the Hanging Hills, near Meriden, 

 Conn., is brought again to the surface in Lamentation Mountain 

 some five miles to the eastward. The evidence for this is 

 the similarity in series of strata found on the face of each out- 

 crop-slope, as described by Percival in his Geology of Connecti- 

 cut, 1842 ; and though the case is made very probable, more ex- 

 amination is needed before it can be generally accepted. Under 

 the heavy trap there is found in descending order, shale, lime- 

 stone, amygdaloidal trap and sandstone on both of these slopes; 

 and the probability that this agreement should be accidental is 

 very small; it much more probably shows a double outcrop of 

 the same series of rocks ; and as the dip is eastward in. each case, 

 the repetition must be the effect of a fault. There is no likeli- 

 hood that this fault will ever be seen directly, for the valley 

 where it is hidden is occupied by heavy masses of drift — the 

 irregular kame-like hills about Beaver Pond, on the line of the 

 ~New Haven and Hartford R. R., a few miles north of Meriden ; but 

 although unseen, it is nearly as well proved as the often-mentioned 

 faults of Virginia and Tennessee. Several smaller faults have simi- 

 lar but less complete evidence. 



