two hundred miles from the
shore."[888] Wolves, in the arctic regions, often venture upon the ice
near the shore, for the purpose of preying upon young seals which they
surprise when asleep. When these ice-floes get detached, the wolves are
often carried out to sea; and though some may be drifted to islands or
continents, the greater part of them perish, and have been often heard
in this situation howling dreadfully, as they die by famine.[889]

During the short summer which visits Melville Island, various plants
push forth their leaves and flowers the moment the snow is off the
ground, and form a carpet spangled with the most lively colours. These
secluded spots are reached annually by herds of musk-oxen and reindeer,
which travel immense distances over dreary and desolate regions, to
graze undisturbed on these luxuriant pastures.[890] The rein-deer often
pass along in the same manner, by the chain of the Aleutian Islands,
from Behring's Straits to Kamtschatka, subsisting on the moss found in
these islands during their passage.[891] But the musk-ox,
notwithstanding its migratory habits, and its long journeys over the
ice, does not exist, either in Asia or Greenland.[892]

_On floating islands of drift-wood._--Within the tropics there are no
ice-floes; but, as if to compensate for that mode of transportation,
there are floating islets of matted trees, which are often borne along
through considerable spaces. These are sometimes seen sailing at the
distance of fifty or one hundred miles from the mouth of the Ganges,
with living trees standing erect upon them. The Amazon, the Congo, and
the Orinoco, also produce these verdant rafts, which are formed in the
manner already described when speaking of the great raft of the
Atchafalaya, an arm of the Mississippi, where a natural bridge of
timber, ten miles long, and more than two hundred yards wide, existed
for more than forty years, supporting a luxuriant vegetation, and rising
and sinking with the water which flowed beneath it.

On these green islets of the Mississippi, observes Malte-Brun, young
trees take root, and the pistia and nenuphar display their yellow
flowers: serpents, birds, and the cayman alligator, come to repose
there, and all are sometimes carried to the sea and engulphed in its
waters.[893]

Spix and Martius relate that, during their travels in Brazil, they were
exposed to great danger while ascending the Amazon in a canoe, from the
vast quantity of drift