in doing so, prejudices must disappear, and that scientific investigation
only helps us the better to understand revealed Scripture.
Without taking into consideration the period occupied in building
up the Island, the data we have to guide us in fixing its birth so long
ago are those changes which have manifestly occurred in the contour
of the land. I f then we are able to fix definitely the outline of the
formation as it originally stood, and then assume, after careful observation,
a rate for its disintegration and decomposition, we may
easily arrive, by a simple calculation, at a fairly correct estimate of
the time required for it to assume its present size and shape. I f we
pick up a piece of stone anywhere on the higher land and break it
across, we see directly that its interior presents a hard bright metallic
lava fracture very different in colour and texture from its external
coating, which for about a quarter of an inch in thickness is soft
and friable. We quite fail, indeed, to recognise the inside and the
outside of the stone as the same substance; but it is only exposure
to wet and dry weather alternately that has thus oxydized or rotted
and changed the external surface, which crumbling away and falling
into clay or dust allows the atmospheric influence to continue acting
on the stone, eating deeper and deeper into it until it becomes, in
time, completely reduced to powder. This process is continually
going on in large rocks as well as small stones, and the higher the
altitude, where the' most moisture exists, or the nearer the rocks
are to the influence of the sea, so much quicker does disintegration
and decomposition take place. There remains no landmark
whereby to judge how much higher the edge of the great crater, or
central mountain ridge, once was than it is at present, but that it
was much higher is certain. Its lava edges have through ages (just
as is still the case, with the assistance also of vegetation), gone on
passing into alluvial soil, which in its turn has been washed down by
rains to the valleys and plateaux of the lower districts. Much of the
upper surface of the Island has in this way been removed, while much
also still remains as marl in a transition state from lava rock to
surface soil; indeed most of the upper parts of the Island are now
covered with these grey, blue, or yellow marls, hut they do not
extend to more than a few feet in depth, when the hard lava again
occurs. There are many opportunities of observing this in the roadside
pits which the road-menders, searching for material, have opened.
The rapidity with which rocks disintegrate or wear away varies
according to their nature ; often the harder rock, lying side by side
with those of different quality, is left standing while its adjacent
ground disappears. We have already noticed this in the case of
the large dike traversing the Sandy Bay crater, and to which we
shall again recur in connexion with the subject now before us.
There are, however, in addition to that dike, other large ones intersecting
the edge of the crater, which by the same process have been
laid hare; some of these are of considerable size, and, although not
so conspicuous and easily traced as the Great Lot dike, they all
partake of the same general direction and lie parallel with it. At
intervals, where the directions coincide, the crater edge itself is at
present formed for some distance by the exposed edge of a dike.
This may be seen to the westward of Diana’s Peak, where
the narrow roadway leading to the highest mountain top appears
to pass along the top of a wall, this wall being nothing more
than the dike itself, with perpendicular faces of a hundred feet
or more, and a width of only eight or ten feet. But for the ferns
and other native vegetation which thickly clothe it, and conceal the
danger, this perilous way would certainly be less popular with
pleasure-seekers and pic-nic parties en route for Diana’s Peak. The
edge of the crater, about three miles further to the westward, a little
beyond West Lodge, is again cut by some of these dikes crossing it
at very acute angles. Three of them of considerable thickness, but
not rendered so strikingly conspicuous by denudation of the surrounding
rocks, lie within the space of half a mile; and, although
placed in such near proximity to one another, differ entirely in
composition. Proceeding in the direction already indicated, to a
short distance beyond the old Piquet House on the ridge, we arrive
at the first of these dikes. I t is composed of a compact dolerite, of
a deep brownish hue, containing disseminated augite and chrysolite,
partly amygdaloidal and zeolitic, the cavities being filled or lined
with minute white transparent crystals in form resembling chabazite.
Massive boulders of this rock have become detached and rolled down
the hillside, where they lie scattered about, protruding above
the grassy slopes on either side of the road leading from West
Lodge down to Thompson’s Wood. Upon nearing Thompson’s Wood
House, where a small patch of weather-beaten Pine trees stands in its
rear, other boulders similarly lodged occur, but of a somewhat more
laminated character. Their composition also is found on exami