6,
that, in his tour there three years before, he had bored in Siberia to
the depth of seventy feet, and, after passing through much frozen soil
mixed with ice, had come down upon a solid mass of pure transparent ice,
the thickness of which, after penetrating two or three yards, they did
not ascertain. We may conceive, therefore, that even at the period of
the mammoth, when the Lowland of Siberia was less extensive towards the
north, and consequently the climate more temperate than now, the cold
may still have been sufficiently intense to cause the rivers flowing in
their present direction to sweep down from south to north the bodies of
drowned animals, and there bury them in drift ice and frozen mud.

If it be true that the carcass of the mammoth was imbedded in pure ice,
there are two ways in which it may have been frozen in. We may suppose
the animal to have been overwhelmed by drift snow. I have been informed
by Dr. Richardson, that, in the northern parts of America, comprising
regions now inhabited by many herbivorous quadrupeds, the drift snow is
often converted into permanent glaciers. It is commonly blown over the
edges of steep cliffs, so as to form an inclined talus hundreds of feet
high; and when a thaw commences, torrents rush from the land, and throw
down from the top of the cliff alluvial soil and gravel. This new soil
soon becomes covered with vegetation, and protects the foundation of
snow from the rays of the sun. Water occasionally penetrates into the
crevices and pores of the snow; but, as it soon freezes again, it serves
the more rapidly to consolidate the mass into a compact iceberg. It may
sometimes happen that cattle grazing in a valley at the base of such
cliffs, on the borders of a sea or river, may be overwhelmed, and at
length inclosed in solid ice, and then transported towards the polar
regions. Or a herd of mammoths returning from their summer pastures in
the north, may have been surprised, while crossing a stream, by the
sudden congelation of the waters. The missionary Huc relates, in his
travels in Thibet in 1846, that, after many of his party had been frozen
to death, they pitched their tents on the banks of the Mouroui-Ousson
(which lower down becomes the famous Blue River), and saw from their
encampment "some black shapeless objects ranged in file across the
stream. As they advanced nearer no change either in form or distinctness
was apparent; nor was it till they were quite close, that