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BIDLET ON THE 







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the ash-beds from destruction and denudation to the present day. 



The centre of the promontory which ends in Cape PlacelHere 



consists at the top of a bluish, rather loose-textured basalt ; but 



the dense thickets and woods here make the geology difficult to 



see. On the north side of the Sapate, however, we come again to 



scoria-beds in the cliffs traversed, as above mentioned, by basalt 



dykes ; and at Cape PlacelHere itself we found scoriaceous rocks, 



with volcanic agglomerates, pumices, and other loose-textured 



lavas, which seem to confirm the theory of an important crater 



having formerly existed in the neighbourhood. The Cape itself, 



however, appears to be basalt, and we were unable to trace any 



remains of a crater in this direction. One can only suggest from 



the angle at which the bed of scoria above mentioned lies that 



the crater from which they were ejected was somewhere to the 



N.E. of Cape Placelli&e. 



Mr. Ridley writes : — " In one spot on this side of the island we 

 found a cavern eaten out by the sea ; its walls were formed by two 

 dykes traversing the scoria-beds ; the softer scoria had been re- 

 moved by the sea up to a certain height, forming a small cave ; I 

 mention this because I believe it to be the origin of the Hole in 

 the Wall that pierces Cape PlacelHere, which was some distance 

 beyond this. "We were unable to reach the Hole because of the 

 great difficulty of getting there by land, though we made several 

 attempts; nor were we able to reach it by sea on account of 

 having no boats. Cape PlacelHere consists of a narrow high wall 

 of basalt, scoria, and pumiceous and tufaceous rocks, running 

 almost due north, the base of which is of some thickness, and 

 the top a narrow broken edge. As far as we could make out 

 from the nearest point we could reach, a dyke runs half across 

 the entrance to the Hole on the eastern side. 



"Sand occurs in several of the larger bays, chiefly on the north 

 side ; but in Peak Bay we were informed that during the winter 

 months, when the current sets this way from the north, all this 

 sand is removed, and the large basalt boulders underlying it are 

 uncovered. At certain spots and at certain times black sand is 

 found on the shore ; this seems to be produced by the washing- 

 out of the lighter grains of quartz and fragments of shells &c, so 

 that only the heavier hornblende and magnetite crystals and 

 grains are left." 



Above S. Antonio Bay are extensive sand-hills, the sand being 

 drifted up by the wind from the south. In some spots it was 





















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