N. U. Darton — Trap of New Jersey. 135 



The long, level-crested ridge extending with palisadal front 

 along the Hudson River northward from New York for thirty 

 miles is a well known member of the series, and the Watchung 

 or Orange Mountains some miles westward are other conspicuous 

 instances. Sonrland Mountain crossing the Delaware just below 

 Lambertsville, Cushetunk Mountain east of Clinton and the 

 line of ridges extending from south of New Brunswick to the 

 Delaware and beyond, embrace the other large masses. 



The earlier writers, from Pierce in 1819 to Rogers in 1836, 

 expressed opinions in regard to the origin and nature of the 

 trap masses, but they were so vague and contradictory that 

 their significance is hardly noteworthy. 



Rogers was the first to definitely recognize the evidence of 

 intrusion and he considered all the trap masses subsequent in 

 date to the enclosing sediments. 



In 1846 Emmons described the palisade trap near the New 

 Jersey-New York line and presented evidence indicating its in- 

 trusive nature and sheet-like structure. 



Cook, in the Geology of New Jersey, 1868, described all the 

 larger trap masses as intruded sheets, and as evidence of the in- 

 trusive nature of the Watchung Mountain outcrops, refers to 

 the occurrence of indurated shales and limestones on the back 

 of the mountain, northwest of Plainfield (at Feltville) and to 

 their analogy in general relations to the Palisade and other in- 

 trusive traps. 



Russell, in 1878, described in some detail the occurrence of 

 what were supposed to be intensely altered shales and limestone 

 on the inner side of the first Watchung Mountain at Feltville, 

 and added great weight to the prevailing view that the Watch- 

 ung and all the other trap masses were intrusive. 



In 1882, Davis visited several typical localities in the New 

 Jersey area for the purpose of determining the nature of the 

 traps, and while he agreed with previous observers, Emmons, 

 Cook, Credner, and Russell, in regard to the intrusive nature 

 of the palisade trap, he stated his conviction that the Watchung 

 traps were extrusive and similar in relations to some of the ex- 

 trusive sheets which he had studied in the Connecticut valley. 

 He found the base of the second Watchung trap resting on ap- 

 parent tuff deposits at Little Falls and the conformable base 

 and the amygdnlar and ropy-surfaced rock of the first Watch- 

 ung trap exposed near Paterson. At the Feltville locality 

 he found no traces of the alteration described by Rogers, Cook, 

 and Russell, but on the contrary, it was seen that the vesicular, 

 slag-like rock was overlain by unaltered shales with an inter- 

 vening trap breccia at some points. This breccia alone was 

 considered satisfactory proof of the extrusive nature of the 



