chap. i. Small Orifices of Eruption. 19 



several times mentioned, especially with reference to 

 the remarkable manner in which the white calcareous 

 stratum, in other parts so horizontal (Woodcut No. 2), 

 dips under it into the sea. It is a broad summit, with 

 obscure traces of a crateriform structure, and is com- 

 posed of basaltic rocks, 1 some compact, others highly- 

 cellular, with inclined beds of loose scorise, of which 

 some are associated with earthy lime. Like Red Hill, 

 it has been the source of eruptions, subsequently to the 

 elevation of the surrounding basaltic plain ; but unlike 

 that hill, it has undergone considerable denudation, 

 and has been the seat of volcanic action at a remote 

 period, when beneath the sea. I judge of this latter 

 circumstance from finding on its inland flank the last 

 remnants of three small points of eruption. These 

 points are composed of glossy scorise, cemented by 

 crystalline calcareous spar, exactly like the great sub- 

 marine calcareous deposit, where the heated lava has 

 rolled over it : their demolished state can, I think, be 

 explained only by the denuding action of the waves of 

 the sea. I was guided to the first orifice by observing 

 a sheet of lava, about 200 yards square, with steepish 

 sides, superimposed on the basaltic plain, with no adjoin- 

 ing hillock, whence it could have been erupted ; and 

 the only trace of a crater which I was able to discover, 

 consisted of some inclined beds of scoriae at one of its 

 corners. At the distance of fifty yards from a second 

 level-topped patch of lava, but of much smaller size, I 



1 Of these, one common variety is remarkable for being full of 

 small fragments of a dark jasper-red earthy mineral, which, when 

 examined carefully, shows an indistinct cleavage ; the little frag- 

 ments are elongated in form, are soft, are magnetic before and after 

 being heated, and fuse with difficulty into a dull enamel. This 

 mineral is evidently closely related to the oxides of iron, but I 

 cannot ascertain what it exactly is. The rock containing this 

 mineral is crenulated with small angular cavities, which are lined 

 and filled with yellowish crystals of carbonate of lime. 



