earned from
an examination of existing glaciers. Further down the valley, where
now the glaciers never extend, are seen very distinctly the same signs.
There are the same moraines, striated rocks, and bowlders that have
evidently traveled from their home up the valley. The only explanation
possible in this case is that once the glaciers extended to that point
in the valley.

It required a person who was perfectly familiar with the behavior of
Alpine glaciers, and knew exactly what marks they left behind in their
passage, to point out the proofs of their former presence in Northern
Europe and America, where it seems almost impossible to believe they
existed. Such a man was Louis Agassiz, the eminent naturalist. Born and
educated in Switzerland, he spent nine years in researches among the
glaciers of the mountains of his native country. He proved the former
wide extension of the glaciers of Switzerland. With these results before
them, geologists were not long in showing that there had once been
glacial ice over a large part of Europe and North America.

The proofs in this case are almost exactly the same as those used to
show that the ancient glaciers of Switzerland were once larger than now.
But as the great glaciers of the glacial age were many times larger than
any thing we know of at the present day, there were of course different
results produced.

For instance, the water circulating under Alpine glaciers is enabled
to wash out and carry away the mass of pulverized rock and dirt ground
along underneath the ice. But when the glaciers covered such an enormous
extent of country as they did in the Glacial Age, the water could not
sweep away this detritus, and so great beds of gravel, sand, and clay
would be formed over a large extent of country. But to go over the
entire ground would require volumes; it is sufficient to give the
results.

The interior of Greenland to-day is covered by one vast sea of ice.
Explorers have traversed its surface for many miles; not a plant, or
stone, or patch of earth is to be seen. In the Winter it is a snow-swept
waste. In the Summer streams of ice-cold water flow over its surface,
penetrating here and there by crevasses to unknown depths. This great
glacier is some twelve hundred miles long, by four hundred in width.<3>
Vast as it is, it is utterly insignificant as compared with the great
continental glacier that geologists assure us once held in its grasp the
larger portion of North