mmm
G E O L O G Y A N D M I N E R A L O G Y . 59
more rapid at that period when the land being higher attracted more
clouds, and consequently there was greater rainfall, and probably
snow water, to assist the process. Although this action is sufficient
to account for the present size and appearance of these ravines, I am
inclined to think that they had their rudimentary origin, or their
courses traced out previous to their enlargement by running water,
in the sheets of lava as they spread outwards from the crater’s edge
in a semi-fluid or viscous state. Plowing in a sluggish manner, the
outer edge of the .lava would naturally terminate in a form somewhat
similar to that of the fingers of a human hand when spread out
flat upon the palm; each subsequent flow or stratum taking the
same course and shape, the spaces left between the fingers, as it
were, would represent the commencement of the ravines. That the
lavas have travelled very slowly is evidenced by the elongation, in
the direction of the flow, of the air cavities contained in them, as
well as by the remarkable forms which the scum has assumed
where it has accumulated, before cooling, very like the froth
on the surface of stagnant water. In the locality of High Knoll
and Ladder Hill, this hardened scum so greatly resembles in texture
the stems of trees as to be commonly mistaken for petrified wood.
Some of it is so scoriaceous or full of minute cavities that it floats
for a considerable time when placed in water; it is, in fact, a kind
of coarse pumice.
A confirmation of the opinion that the larger ravines had their
origin in the flows of lava, I think, may he obtained by walking
along the ridge, or present crater edge, and noticing the natural
forms of the spurs or divisions which separate one from the other.
Standing on Diana’s Peak, and looking down eastward, the flow of
lavas appears to have taken two directions. One stream, that nearest
to the hill on which stands Sunberry Cottage, has flowed irregularly
for about a quarter of a mile easterly, when it seems to have
divided ; one branch has flowed northerly towards Prosperous Bay,
on which is situated Arnos Yale, and now shows a very ragged
steep ridge for about a mile, until it reaches “ Shark’s Valley,” when
it turns in an easterly direction towards George’s Island, and then
gradually slopes down, losing itself in Shark’s Valley, about three-
quarters of a mile distant from the sea shore; the other branch seems
to have travelled on still more easterly, forming that very irregular
portion of the Island lying between Stone Top Bay and Deep