to judge, generally in process of decrease. In Switzerland,
although the ancients even in Roman days were in contact with the ice,
they were so unobservant that they did not even remark that the ice
was in motion. Only during the last two centuries have we any
observations of a historic sort which are of value to the geologist.
Fortunately, however, the signs written on the rock tell the story,
except for its measurement in terms of years, as clearly as any
records could give it. From this testimony of the rocks we perceive
that in the geological yesterday, though it may have been some tens of
thousands of years ago, the Swiss glaciers, vastly thickened, and with
their horizontal area immensely expanded, stretched over the Alpine
country, so that only here and there did any of the sharper peaks rise
above the surface. These vast glaciers, almost continually united on
their margins, extended so far that every portion of what is now the
Swiss Republic was covered by them. Their front lay on the southern
lowlands of Germany, on the Jura district of France; on the south, it
stretched across the valley of the Po as far as near Milan. We know
this old ice front by the accumulations of rock _debris_ which were
brought to it from the interior of the mountain realm. We can
recognise the peculiar kinds of stone, and with perfect certainty
trace them to the bed rock whence they were riven. Moreover, we can
follow back through the same evidence the stages of retreat of the
glaciers, until they lost their broad continental character and
assumed something like their present valley form. Up the valley of any
of the great rivers, as, for instance, that of the Rhone above the
lake of Geneva, we note successive terminal moraines which clearly
indicate stages in the retreat of the ice when for a time it ceased to
go backward, or even made a slight temporary readvance. It is easily
seen that on such occasions the stones carried to the ice front would
be accumulated in a heap, while during the time when day by day the
glacier was retreating the rock waste would be left broadcast over the
valley.

As we go up from the course of the glacial streams we note that the
successive moraines have their materials in a progressively less
decayed state. Far away from the heap now forming, and in proportion
to the distance, the stones have in a measure rotted, and the heaps
which they compose are often covered with soil and occupied by
forests. Within