24 St. J ago. paet i. 



chiefly to innumerable, microscopically minute, black 

 specks, which, when a fragment is heated, are easily 

 fused, and evidently are either hornblende or augite. 

 These rocks, therefore, although at first appearing like 

 baked clay or some altered sedimentary deposit, contain 

 all the essential ingredients of trachyte ; from which 

 they differ only in not being harsh, and in not con- 

 taining crystals of glassy feldspar. As is so often 

 m the case with trachytic formation, no stratification is 

 here apparent. A person would not readily believe that 

 these rocks could have flowed as lava ; vet at St. Helena 

 there are well characterised streams (as will be described 

 in an ensuing chapter) of nearly similar composition. 

 Amidst the hillocks composed of these rocks, I found in 

 three places, smooth conical hills of phonolite, abound- 

 ing with fine crystals of glassy feldspar, and with needles 

 of hornblende. These cones of phonolite, I believe, 

 bear the same relation to the surrounding feldspathic 

 strata which some masses of coarsely crystallised augitic 

 rock, in another part of the island, bear to the surround- 

 ing basalt, namely, that both have been injected. The 

 rocks of a feldspathic nature being anterior in origin to 

 the basaltic strata, which cap them, as well as to the 

 basaltic streams of the coast-plains, accords with the 

 usual order of succession of these two grand divisions of 

 the volcanic series. 



The strata of most of these hills in the upper part, 

 where alone the planes of division are distinguishable, 

 are inclined at a small angle from the interior of the 

 island towards the sea-coast. The inclination is not the 

 same in each hill ; in that marked A it is less than 

 in B, D, or E ; in C the strata are scarcely deflected 

 from a horizontal plane, and in F (as far as I could 

 judge without ascending it) they are slightly inclined 

 in a reverse direction, that is, inwards and towards the 



