fter the
discrimination has once been made. As to the southward movement of an
immense field of ice, extending over the whole north, it seems
inevitable, the moment we admit that snow may accumulate around the pole
in such quantities as to initiate a pressure radiating in every
direction. Snow, alternately thawing and freezing, must, like water,
find its level at last. A sheet of snow ten or fifteen thousand feet in
thickness, extending all over the northern and southern portions of the
globe, must necessarily lead, in the end, to the formation of a northern
and southern cap of ice, moving toward the equator.

I have spoken of Tijuca and the Dom Pedro Railroad as favorable
localities for studying the peculiar southern drift; but one meets it in
every direction. A sheet of drift, consisting of the same homogeneous,
unstratified paste, and containing loose materials of all sorts and
sizes, covers the country. It is of very uneven thickness,--sometimes
thrown into relief, as it were, by the surrounding denudations, and
rising into hills,--sometimes reduced to a thin layer,--sometimes, as,
for instance, on steep slopes, washed entirely away, leaving the bare
face of the rock exposed. It has, however, remained comparatively
undisturbed on some very abrupt ascents; as, for instance, on the
Corcovado, along the path leading up the mountain, are some very fine
banks of drift,--the more striking from the contrast of their deep red
color with the surrounding vegetation. I have myself followed this sheet
of drift from Rio de Janeiro to the top of the Serra do Mar, where, just
outside the pretty town of Petropolis, the river Piabanha may be seen
flowing between banks of drift, in which it has excavated its bed;
thence I have traced it along the beautiful macadamized road leading to
Juiz de Fora in the province of Minas Geraes, and beyond this to the
farther side of the Serra da Babylonia. Throughout this whole tract of
country, in the greater part of which travelling is easy and
delightful,--an admirable line of diligences, over one of the finest
roads in the world, being established as far as Juiz de Fora,--the drift
may be seen along the roadside, in immediate contact with the native
crystalline rock. The fertility of the land, also, is a guide to the
presence of drift. Wherever it lies thickest over the surface, there are
the most flourishing coffee-plantations; and I believe that a more
systematic regard to this fact would have