132 GEOLOGICAL APPEARANCES. 



The most prominent features in the geolo- 

 gical structure * of St. Helena, as well as the 

 presence of some extinct craters, offer indubi- 

 table evidence that this island is of volcanic 

 origin. The prevailing form of the land, es- 

 pecially as regards an alternate arrangement of 

 its valleys and hills, radiating from the interior 

 and descending to the coast, reminded me for- 

 cibly of the similar construction that obtains in 

 the principal volcanic islands of the Pacific 

 Ocean. 



The arable soil is chiefly composed of a red 

 argillaceous earth. The composition of the 

 mountains is for the most part a blue or dark- 

 gray basaltic rock, occasionally exhibiting 

 sulphur in its fissures. In some parts of the 

 island, as at Stone Top, there are cliffs which 

 present a vertical arrangement of basaltic co- 

 lumns, equally elegant and interesting with those 

 of the Giant's Causeway ; although they are on a 

 much less gigantic scale. Some of the naked hills, 



* Robert Scale, Esq. F. R.S., resident at St. Helena, 

 has published some beautiful drawings, illustrative of the 

 geology of this island ; and has, after many years patient 

 labour, perfected a most complete model of the country 

 in plaster of Paris, and which is now in the possession of 

 the Honourable East India Company. 



