SUBJACENT ROCKS. 385 



all sides, and portions of it were successively brought 

 above the sea till the island attained its present 

 condition. Slight shocks of earthquake were said 

 to be felt even now occasionally. 



Following up the valley, at a point about half a 

 mile above the town, its sides recede a little, forming 

 a small basin- shaped expansion ; and on the western 

 side, a small lateral valley comes down, bringing a 

 rill of water into the main brook. At this point, 

 some beds of red and grey shale make their appear- 

 ance, containing some thin bands of a smooth com- 

 pact limestone, — hard, brittle, laminated, and very 

 different in aspect from the coral rock which still 

 caps the banks of the valley farther back from the 

 river. These rocks appeared only here and there, 

 in small holes and breaks of the ground, and I 

 could not find any section large enough to shew 

 their dip or strike ; they appeared, however, to lie 

 nearly horizontally. They were of considerable 

 thickness, as on a sloping ground, the summit of 

 which was about 400 feet above the sea, they 

 occupied the lower half of the slope down to the 

 river. There was also a considerable mass of 

 trap-rock, resembling the toadstone of Derby- 

 shire in its general aspect, exhibited on both 

 sides of the river, but not with sufficient clearness 

 to enable me accurately to make out its relations to 

 the surrounding rocks. On the west side it oc- 

 curred at the mouth of the small lateral valley, 

 and I could trace it nearly up to the base of the 



vol. i. 2 c 



