The Ash Bed at Meriden. 25 



part has already been thus consumed. The destructive process is 

 still going on, and probably about as fast as it has worked on the 

 average in the past. Now following along the edge of this sheet to 

 the north, we find successively the ash bed, outcrops of dense trap, 

 then bluffs of trap conglomerate, and further on, more dense trap, 

 from which it may be safely argued that a bed or sheet which pre- 

 sents these varied appearances can only be of extrusive origin. Fur- 

 ther evidence to the same conclusion will be found by examining a 

 small outcrop on the back or eastern slope of the anterior ridge, 

 about east of the ash bed, where the trap sheet is just covered by 

 the over-lying sandstones, which near the trap contain fragments of 

 it, showing unmistakably that the trap was there as a foundation 

 on which these over-lying beds were deposited. 



Similar characteristics may be found in various other trap ridges 

 of the neighborhood, and constitute most interesting features for 

 discovery, observation and reflection. I may instance one locality 

 where the contact of the over-lying sandstone on the back of the 

 upper surface of the thick trap sheet that forms Lamentation Mount- 

 ain is particularly well shown; this is at Spruce Brook, where it runs 

 on the eastern slope of Lamentation northward towards the road 

 that passes by the north end of the mountain; it flows from the trap 

 to the sandstone and exposes an excellent natural section that de- 

 serves as much attention as the ash bed, even though it is not quite 

 so striking in its appearance. It shows the over-lying sandstone to 

 contain many vesicular fragments derived from the trap, and in the 

 vesicles of these fragments, a lens reveals the finer sediments lying 

 just as fine sandy deposits lie in the scoriaceous surface of submarine 

 lava-flows at the present time. The conclusion that these lava sheets 

 are great surface flows, extruded at the time when the Triassic sand- 

 stones were accumulating, is borne out not only by the direct evi- 

 dence of the kind here adduced, but also by the contrast thus afford- 

 ed with the features of the West Rock ridge, which runs northward 

 from New Haven. Roaring Brook, not far west of Cheshire, on the 

 eastern slope of Gaylord's Mountain, has exposed a contact of the 

 trap sheet of this mountain with the sandstone that lies on its back; 

 and the two together exhibit all the characteristics that might be ex- 

 pected of an intrusive sheet. The trap is dense and fine-grained, 

 and not in the least vesicular; its upper surface is relatively smooth 

 and the sandstone lying close upon it is indurated; at one point, a 

 narrow, fine-grained branch or off shoot of the main sheet may be 

 seen penetrating the over-lying beds for several feet; but these over- 

 lying beds do not contain trap fragments. This association of feat- 



