has been made for such seeds, and they have not been found.
Professor Kerner of Innsbruck examined the snow on the surface of
glaciers, and assiduously collected all the seeds he could find, and
these were all of plants which grew in the adjacent mountains or in the
same district. In like manner, the plants growing on moraines were found
to be those of the adjacent mountains, plateaux, or lowlands. Hence he
concluded that the prevalent opinion that seeds may be carried through
the air for very great distances "is not supported by fact."[176] The
opinion is certainly not supported by Kerner's facts, but neither is it
opposed by them. It is obvious that the seeds that would be carried by
the wind to moraines or to the surface of glaciers would be, first and
in the greatest abundance, those of the immediately surrounding
district; then, very much more rarely, those from more remote mountains;
and lastly, in extreme rarity, those from distant countries or
altogether distinct mountain ranges. Let us suppose the first to be so
abundant that a single seed could be found by industrious search on each
square yard of the surface of the glacier; the second so scarce that
only one could possibly be found in a hundred yards square; while to
find one of the third class it would be necessary exhaustively to
examine a square mile of surface. Should we expect that _one_ ever to be
found, and should the fact that it could not be found be taken as a
proof that it was not there? Besides, a glacier is altogether in a bad
position to receive such remote wanderers, since it is generally
surrounded by lofty mountains, often range behind range, which would
intercept the few air-borne seeds that might have been carried from a
distant land. The conditions in an oceanic island, on the other hand,
are the most favourable, since the land, especially if high, will
intercept objects carried by the wind, and will thus cause more of the
solid matter to fall on it than on an equal area of ocean. We know that
winds at sea often blow violently for days together, and the rate of
motion is indicated by the fact that 72 miles an hour was the average
velocity of the wind observed during twelve hours at the Ben Nevis
observatory, while the velocity sometimes rises to 120 miles an hour. A
twelve hours' gale might, therefore, carry light seeds a thousand miles
as easily and certainly as it could carry quartz-grains of much greater
specific gravity, rotundity, and