Scotland and Scandinavia. And here I must add, that endless questions of
interest will arise to those who will study, not merely the invasion of
that truly European flora, but the invasion of reptiles, insects, and
birds, especially birds of passage, which must have followed it as soon
as the land was sufficiently covered with vegetation to support life.
Whole volumes remain to be written on this subject. I trust that some of
your younger members may live to write one of them. The way to begin
will be: to compare the flora and fauna of this part of England very
carefully with that of the southern and eastern counties; and then to
compare them again with the fauna and flora of France, Belgium, and
Holland.

As for the Atlantic flora, you will have to decide for yourselves whether
you accept or not the theory of a sunken Atlantic continent. I confess
that all objections to that theory, however astounding it may seem, are
outweighed in my mind by a host of facts which I can explain by no other
theory. But you must judge for yourselves; and to do so you must study
carefully the distribution of heaths, both in Europe and at the Cape; and
their non-appearance beyond the Ural Mountains, and in America, save in
Labrador, where the common ling, an older and less specialised form,
exists. You must consider, too, the plants common to the Azores,
Portugal, the West of England, Ireland, and the Western Hebrides. In so
doing young naturalists will at least find proofs of a change in the
distribution of land and water, which will utterly astound them when they
face it for the first time.

As for the Northern flora, the question whence it came is puzzling
enough. It seems difficult to conceive how any plants could have
survived when Scotland was an archipelago in the same ice-covered
condition as Greenland is now; and we have no proof that there existed
after the glacial epoch any northern continent from which the plants and
animals could have come back to us. The species of plants and animals
common to Britain, Scandinavia, and North America, must have spread in
pre-glacial times, when a continent joining them did exist.

But some light has been thrown on this question by an article, as
charming as it is able, on "The Physics of the Arctic Ice," by Dr. Brown,
of Campster. You will find it in the 'Quarterly Journal of the
Geological Society' for February 1870. He shows there that even in
Greenland peaks and crags are lef