112 Junction of Trap and Sandstone. 



wrought upon the sandstone, seems to have been in exact proportion 

 to the mass of trap with which it is in contact. 



From (p) fig. 3, to (r) there is a steep precipice fronting east- 

 ward, evidently the termination of a large dyke which lies beneath 

 the surface. East of this, the dip of the sandstone is considerably 

 greater than in the other parts of the town, being in some places in- 

 clined at an angle of from 25° to 30°. South of the dyke, supposed 

 to run north of, and parallel with the Cheshire road, the inclination 

 of the sandstone is less to the east, but it appears to have an addi- 

 tional dip to the south. This dip, though inconsiderable, is suffi- 

 cient to show that the disturbing cause did not uniformly act in par- 

 allel lines, and it is not impossible but the sandstone may have been 

 fractured, both in the lines (pr) fig. 3, and {b p), fig. 5, by the force 

 which elevated it ; on which supposition, a small diagonal fracture 

 in the direction {p k) fig. 3, would cause the sandstone south of 

 {bp) fig. 5, to dip gently to the south. It should be mentioned that 

 there is no visible connection between the sandstone lying on the 

 Cheshire road, and that south of the dell through which the brook I 

 have described flows, until we pass west of the point (c), fig. 5 : but 

 that the sandstone at (m) fig. 5. retains the ordinary dip to the east, 

 as if it had been undisturbed by the commotion that rent its nearest 

 neighbor north. 



The supposition of such a force, fracturing the sandstone in two 

 directions, accounts satisfactorily for the existence of those numerous 

 rents and fissures in the sandstone, now occupied by trap, in the 

 form of veins and dykes. 



It is not my intention to go into an inquiry concerning the origin 

 of the trappean family of rocks ; and I will only remark, that the 

 appearances presented by the sections I have attempted to describe, 

 in my opinion, and in the opinion of others who have visited those 

 places, whether men of science or not, carry as convincing evidence 

 of the former action of fire, as does the fine coal and ashes left in the 

 bed of a pit of charcoal. To the sections already described, I will 

 add one more, about a mile south-west from the Cheshire road, 

 where the sandstone, at its junction with the trap, has been fused, and 

 both sandstone and trap are vesicular. To a knowledge of this last 

 section, and for some suggestions concerning the others, I am indebt- 

 ed to the kindness, scientific knowledge, and extensive acquaintance 

 with the geological structure of this region, of my friend F. Cook, 

 M. D. of this place. 



Walliugford, July 21, 1834. 



