In this
hypothetical condition of the Earth's surface, the power of absorbing and
emitting light and heat would every where be the same under the same
latitudes. The mathematical consideration of climate, which does not
exclude the supposition of the existence of currents of heat in the
interior, or in the external crust of the earth, nor of the propagation of
heat by atmospheric currents, proceeds from this mean, and, as it were,
primitive condition. Whatever alters the capacity for absorption and
radiation, at places lying under the same parallel of latitude, gives rise
to inflections in the isothermal lines. The nature of these inflections,
the angles at which the isothermal, isotheral, or isochimenal lines
intersect the parallels of latitude, their convexity or concavity with
respect to the pole of the same hemisphere, are dependent on causes which
more or less modify the temperature under different degrees of longitude.
The progress of 'Climatology' has been remarkably favored by the extension
of European civilization to two opposite coasts, by its transmission from
our western shores to a continent which is bounded on the east by the
Atlantic Ocean. When, after the ephemeral colonization from Iceland and
Greenland, the British laid the foundation of the first permanent
settlements on the shores of the United States of America, the emigrants
(whose numbers were rapidly increased in consequence either of religious
persecution, fanaticism, or love of freedom, and who soon spread over the
vast extent of territory lying between the Carolinas, Virginia, and the St.
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