also, excellent evidence, that it
endured for an enormous time, as measured by years, at each point. The cold
may have come on, or have ceased, earlier at one point of the globe than at
another, but seeing that it endured for long at each, and that it was
contemporaneous in a geological sense, it seems to me probable that it was,
during a part at least of the period, actually simultaneous throughout the
world. Without some distinct evidence to the contrary, we may at least
admit as probable that the glacial action was simultaneous on the eastern
and western sides of North America, in the Cordillera under the equator and
under the warmer temperate zones, and on both sides of the southern
extremity of the continent. If this be admitted, it is difficult to avoid
believing that the temperature of the whole world was at this period
simultaneously cooler. But it would suffice for my purpose, if the
temperature was at the same time lower along certain broad belts of
longitude.

On this view of the whole world, or at least of broad longitudinal belts,
having been simultaneously colder from pole to pole, much light can be
thrown on the present distribution of identical and allied species. In
America, Dr. Hooker has shown that between forty and fifty of the flowering
plants of Tierra del Fuego, forming no inconsiderable part of its scanty
flora, are common to Europe, enormously remote as these two points are; and
there are many closely allied species. On the lofty mountains of equatorial
America a host of peculiar species belonging to European genera occur. On
the highest mountains of Brazil, some few European genera were found by
Gardner, which do not exist in the wide {375} intervening hot countries. So
on the Silla of Caraccas the illustrious Humboldt long ago found species
belonging to genera characteristic of the Cordillera. On the mountains of
Abyssinia, several European forms and some few representatives of the
peculiar flora of the Cape of Good Hope occur. At the Cape of Good Hope a
very few European species, believed not to have been introduced by man, and
on the mountains, some few representative European forms are found, which
have not been discovered in the intertropical parts of Africa. On the
Himalaya, and on the isolated mountain-ranges of the peninsula of India, on
the heights of Ceylon, and on the volcanic cones of Java, many plants
occur, either identically the same or representing each other, and at the
same ti