A mile eastward of the town of Praya, there is a steep-sided gorge, about
one hundred and fifty yards in width, cutting through the basaltic plain
and underlying beds, but since filled up by a stream of more modern lava.
This lava is dark grey, and in most parts compact and rudely columnar; but
at a little distance from the coast, it includes in an irregular manner a
brecciated mass of red scoriae mingled with a considerable quantity of
white, friable, and in some parts, nearly pure earthy lime, like that on
the summit of Red Hill. This lava, with its entangled lime, has certainly
flowed in the form of a regular stream; and, judging from the shape of the
gorge, towards which the drainage of the country (feeble though it now be)
still is directed, and from the appearance of the bed of loose water-worn
blocks with their interstices unfilled, like those in the bed of a torrent,
on which the lava rests, we may conclude that the stream was of subaerial
origin. I was unable to trace it to its source, but, from its direction, it
seemed to have come from Signal Post Hill, distant one mile and a quarter,
which, like Red Hill, has been a point of eruption subsequent to the
elevation of the great basaltic plain. It accords with this view, that I
found on Signal Post Hill, a mass of earthy, calcareous matter of the same
nature, mingled with scoriae. I may here observe that part of the
calcareous matter forming the horizontal sedimentary bed, especially the
finer matter with which the embedded fragments of rock are whitewashed, has
probably been derived from similar volcanic eruptions, as well as from
triturated organic remains: the underlying, ancient, crystalline rocks,
also, are associated with much carbonate of lime, filling amygdaloidal
cavities, and forming irregular masses, the nature of which latter I was
unable to understand.

Considering the abundance of earthy lime near the summit of Red Hill, a
volcanic cone six hundred feet in height, of subaerial growth,--considering
the intimate manner in which minute particles and large masses of scoriae