298 BULLETIN OF THE 



of Newgate Mountain (E. IV. 2. 2) by a band of friable red shale 

 (391). A part of A. 1, S. of E. II. shows a peculiar dark green trap con- 

 glomerate, accompanied by beds or dikes of amygdaloid and fine-grained 

 trap (341). A conglomerate east of Saltonstall Lake contains fragments 

 of a fine-grained light green sub-amygdaloidal trap, similar to that in 

 P. 1 of E. I. (324). The ridge anterior to Lamentation Mountain is 

 partly composed of a peculiar trap conglomerate, or rather brecciated 

 amygdaloid, distinctly parallel or stratified in its arrangement (365). 

 Many similar extracts might be noted. 



In New Jersey, I believe First Mountain to be proved an overflow by 

 observations at Paterson and Feltville (L and M), although Eussell takes 

 the other view. As early as 1822, Cooper wrote that "this mass of 

 floetz trap is poured over the old red sandstone" (240), but it is doubt- 

 ful whether he had considered the possibility of its intrusion. Second 

 Mountain is probably also an overflow, as its sheet is very amygdaloidal 

 and irregular in structure near the under surfoce at Little Falls, and 

 its effect on the underlying sandstone is very slight ; but its upper con- 

 tact has not yet been described. Cook mentions pebbles of trap in the 

 sandstone beneath the First Mountain (6, 337), but later says that no 

 fragments of trap are found in any of the stratified beds (c, 34). 



There are no decisive observations of contact for the trap sheets of 

 Pennsylvania and the States farther south. H. D. Rogers speaks indefi- 

 nitely of "overflowed" trap {g, 670), of amygdaloid near the borders of 

 certain of the larger dikes {g, 671), and of "sandy volcanic tuff's" and 

 " trap shales " interstratified with the sandstones, mostly in Nova 

 Scotia, some in Connecticut and the Middle States {g, 762). Lesley's 

 general section (copied in fig. 1 9) shows " the original sea, the lava and its 

 vent, the manner in which it lifted the new red layers at its outburst, 

 so soon as it was near enough the surfiice to do so, and overflowed them 

 above" (a, 133), but evidence to prove this sequence of events is wanting. 



Heinrich mentions that amygdaloids are found in the Virginia traps 

 (244). 



The sheets which are proved by their appearance at the contacts to 

 be overflows have the following characters : they produce very little 

 metamorphic effect on the underlying strata ; they often show some ve-- 

 sicular structure near the base, sometimes within the mass, and are 

 always very amygdaloidal at the upper surface. It cannot be said that 

 amygdaloids occur only in the overflow sheets, for they are reported in 

 some dikes, and in rare instances in intrusions ; but the vesicular struc- 

 ture is as frequent in the overflows as it is rare elsewhere. 



