moraines of the _higher_
latitudes. For it is a fact very significant in its bearings on the
diluvial controversy, that it is in the higher latitudes in both
hemispheres that these peculiar deposits are chiefly to be found. They
have been traced in Patagonia in the one hemisphere, from the southern
limits of the country to the forty-first degree of south latitude; and
in Europe in the other, to the fortieth; and in America to even the
thirty-eighth degree of north latitude. But in the great belt, nearly
eighty degrees in breadth, which, encircling the globe from east to
west, includes with the torrid the warmer portions of the temperate
zones, they have scarce any existence at all, or exist at least in
different forms and exceedingly reduced proportions. The superficial
deposits, in their most characteristic conditions, are deposits of the
colder portions of the globe, and in many parts indicate that there
prevailed during their formation a much severer climate than now obtains
in the regions in which they occur. The shells which they contain in
Britain, for instance, though almost all of existing species, are many
of them such as are not now to be found in the British seas, but in seas
about ten degrees further to the north; and there is evidence that the
line of perpetual snow must have descended at the time to a lower level
than that attained by our second-class hills, and that almost every
Highland valley had its glacier. They represent, too, vast periods of
time;--earlier periods, during which the land gradually sank, till only
its higher eminences were uncovered, and great floats of icebergs went
careering over its submerged plains and lower hills; and later periods,
during which the land as gradually arose, after apparently many pauses
and oscillations, until at length, when it had reached a level scarce
eighty feet higher than that which it at present maintains, the climate
softened, and the glaciers which had formed in the later times among its
hills ultimately disappeared. Beds of sea-shells of the boreal type,
that belong to those ice ages, may be still found occupying the places
in which they had lived and died, many miles inland, and hundreds of
feet over the sea level. Boring shells, such as the pholodadidae, may be
detected far out of sight of the ocean, still occupying the cells which
they had scooped out for themselves in hard limestone or yielding shale;
and serpula and nuliporate encrustations may be se