84 St. Helena. 



PART I. 



scoriae. Several extensive streams, however, belonging 

 to this series, retain their stony character ; these are 

 either of a blackish-green colour, with minute acicular 

 crvstals of feldspar, or of a very pale tint, and almost 

 composed of minute, often scaly, crystals of feldspar, 

 abounding with microscopical black specks; they are 

 S'enerallv compact and laminated ; others, however, of 

 similar composition, are cellular and somewhat decom- 

 posed. Xone of these rocks contain large crystals of 

 feldspar, or have the harsh fracture peculiar to trachyte. 

 These feldspathic lavas and tuffs are the uppermost or 

 those last erupted ; innumerable dikes, however, and 

 great masses of molten rock, have subsequently been 

 injected into them. They converge, as they rise, 

 towards the central curved ridge, of which one point 

 attains the elevation of 2,700 feet. This ridge is the 

 hio-hest land in the island ; and it once formed the 

 northern rim of a great crater, whence the lavas of this 

 series flowed : from its ruined condition, from the 

 southern half having been removed, and from the 

 violent dislocation which the whole island has under- 

 gone, its structure is rendered very obscure. 



Basaltic series. — The margin of this island is 

 formed by a rude circle of great, black, stratified, ram- 

 parts of basalt, dipping seaward, and worn into cliffs, 

 which are often nearly perpendicular, . and vary in 

 height from a few hundred feet to two thousand. 

 This circle, or rather horse-shoe shaped ring, is open to 

 the south, and is breached by several other wide spaces. 

 Its rim or summit generally projects little above the 

 level of the adjoining inland couutry; and the more 

 recent feldspathic lavas, sloping down from the central 

 heightSj generally abut against and overlap its inner 

 marsrin : on the north-western side of the island, how- 

 ever, they appear (judging from a distance) to have 



