temperature of 6° above the freezing-point. The city of New York,
about 11° south of London, has a winter temperature of much greater
severity. The mean temperature of the State of New York, as determined
by a long series of observations, is 44° 31'.

The mean temperature of countries is found to be very stable, and but
very small variations have been detected in modern times. But that
there have been important climatic changes, since the Christian era,
cannot be doubted, unless we doubt history. Not many centuries ago, it
was a common thing for all the British rivers to freeze up during the
winter, and to remain so for several months. If space permitted, an
interesting statement could he made of the changes which have taken
place in vegetation in Greenland, and throughout certain northern
parts of Europe,--also in Palestine, Greece, and other southern
countries,--while we know that the earth's inclination upon its axis
has been unchanged.

Mrs. Somerville remarks, that, though the temperature of any one place
may be subject to very great variations, yet it never differs from the
mean state more than a few degrees.

Without this atmospheric covering of ours, it is considered that the
temperature of the earth at its surface would be the same as that of
the celestial spaces, supposed to be at least 76° below zero, or
_possibly_, says Humboldt, 1400° below! Human life, without our
atmosphere, could not exist for a single moment.

It is computed, that, if the annual heat received by the earth on its
surface could be equally distributed over it, it would melt, in the
course of a year, a stratum of ice 46 feet thick, though it covered