chap. iv. Elevation of the Land. 103 



flanks of this hill, was probably washed down from the 

 upper part, as soon as the trees perished, and the shelter 

 afforded by them was lost. 



Elevation of the land. — Seeing that the lavas of 

 the basal series, which are of submarine origin, are 

 raised above the level of the sea, and at some places to 

 the height of maoy hundred feet, I looked out for 

 superficial signs of the elevation of the land. The 

 bottoms of some of the gorges, which descend to the 

 coast, are filled up to the depth of about a hundred 

 feet, by rudely divided layers of sand, muddy clay, and 

 fragmentary masses ; in these beds, Mr. Seale has found 

 the bones of the tropic-bird and of the albatross; the 

 former now rarely, and the latter never visiting the 

 island. From the difference between these layers, and 

 the sloping piles of detritus which rest on them, I 

 suspect that they were deposited, when the gorges stood 

 beneath the sea. Mr. Seale, moreover, has shown that 

 some of the fissure-like gorges, 1 become, with a concave 

 outline, gradually rather wider at the bottom than at 

 the top ; and this peculiar structure was probably 

 caused by the wearing action of the sea, when it entered 

 the lower part of these gorges. At greater heights, 

 the evidence of the rise of the land is even less clear : 

 nevertheless, in a bay-like depression on the table-land 

 behind Prosperous Bay, at the height of about 1,000 

 feet, there are flat-topioed masses of rock, which it is 

 scarcely conceivable, could have been insulated from 

 the surrounding and similar strata, by any other agency 

 than the denuding action of a sea-beach. Much denu- 

 dation, indeed, has been effected at great elevations, 

 which it would not be easy to explain by any other 

 means: thus, the flat summit of the Barn, which is 



' A fissure-like gorge, near Stony-top, is said by Mr. Seale to be 

 8i0 feet deep, and only 115 feet in width. 



