s in distribution,--such as the
great difference in the marine faunas on the opposite sides of almost every
continent,--the close relation of the tertiary inhabitants of several lands
and even seas to their present inhabitants,--a certain degree of relation
(as we shall hereafter see) between the distribution of mammals and the
depth of the sea,--these and other such facts seem to me opposed to the
admission of such prodigious geographical revolutions within the recent
period, as are necessitated on the view advanced by Forbes and admitted by
his many followers. The nature and relative proportions of the inhabitants
of oceanic islands likewise seem to me opposed to the belief of their
former continuity with continents. Nor does their almost universally
volcanic composition favour the admission that they are the wrecks of
sunken continents;--if they had originally existed as mountain-ranges on
the land, some at least of the islands would have been formed, like other
mountain-summits, of granite, metamorphic schists, old fossiliferous or
other such rocks, instead of consisting of mere piles of volcanic matter.

I must now say a few words on what are called accidental means, but which
more properly might be called occasional means of distribution. I shall
here confine myself to plants. In botanical works, this or that plant is
stated to be ill adapted for wide dissemination; but for transport across
the sea, the greater or less facilities may be said to be almost wholly
unknown. Until I tried, with Mr. Berkeley's aid, a few experiments, it was
not even known how far seeds could resist the injurious action of
sea-water. To my surprise I found that {359} out of 87 kinds, 64 germinated
after an immersion of 28 days, and a few survived an immersion of 137 days.
For convenience' sake I chiefly tried small seeds, without the capsule or
fruit; and as all of these sank in a few days, they could not be floated
across wide spaces of the sea, whether or not they were injured by the
salt-water. Afterwards I tried some larger fruits, capsules, &c., and some
of these floated for a long time. It is well known what a difference there
is in the buoyancy of green and seasoned timber; and it occurred to me that
floods might wash down plants or branches, and that these might be dried on
the banks, and then by a fresh rise in the stream be washed into the sea.
Hence I was led to dry stems and branches of 94 plants with ripe fruit, and
to place t