98 St. Helena. 



PAItT 1. 



where are apt l to assume singular and even grotesque 

 shapes, like that of Lot : the peak at Fernando Noronha 

 offers an instance ; at St. J ago, however, the cones 

 of phonolite, though tapering, have a regular form. 

 Supposing, as seems probable, that all such hillocks 

 or obelisks have originally been injected, whilst 

 liquefied, into a mould formed by yielding strata, as 

 certainly has been the case with Lot, how are we to 

 account for the frequent abruptness and singularity of 

 their outlines, compared with similarly injected masses 

 of greenstone and basalt ? Can it be due to a less 

 perfect degree of fluidity, which is generally supposed 

 to be characteristic of the allied trachytic lavas ? 



Superficial deposits. — Soft calcareous sandstone 

 occurs in extensive, though thin, superficial beds, both 

 on the northern and southern shores of the island. 

 It consists of very minute, equal-sized, rounded particles 

 of shells, and other organic bodies, which partially 

 retain their yellow, brown, and pink colours, and oc- 

 casionally, though very rarely, present an obscure trace 

 of their original external forms. I in vain endeavoured 

 to find a single unrolled fragment of a shell. The 

 colour of the particles is the most obvious character 

 by which their origin can be recognised, the tints 

 being affected (and an odour produced) by a moderate 

 heat, in the same manner as in fresh shells. The par- 

 ticles are cemented together, and are mingled with 

 some earthy matter : the purest masses, according to 

 Beatson, contain 70 per cent, of carbonate of lime. 

 The beds, varying in thickness from two or three feet 

 to fifteen feet, coat the surface of the ground ; they 

 generally lie on that side of the valley which is pro- 

 tected from the wind, and they occur at the height 



1 D'Anbnissort, in his ' Traite de Geognosie' (torn, ii. p. 540 J 

 particularly remarks that this is the case. 



