In some (we quote Mrs. Somerville) the winters
are mild and the summers cool, whereas in others the extremes of heat
and cold prevail.
Climates are not found coincident with lines of latitude; they are
quite as often found parallel to lines of longitude. If you connect
the extreme points of the mean annual temperatures by a line passing
round the earth, you have a zone, but never a true circle. The curves
are longitudinal.
Climate is dependent on temperature, winds, the elevation of land,
soil, ranges of mountains, and proximity of bodies of water; and it is
also the expression, if we may so term it, of the changes in the
atmosphere sensibly affecting our organs. Humboldt refers it to
humidity, temperature, changes in barometric pressure, calmness or
agitation of the air, amount of electric force, and transparency of
the sky.
When mountains range themselves in lines of latitude across a
continent, they are barriers to civilization, to the mingling of
races, and the union of states. Thus, the Pyrenees have always kept
France and Spain apart, the Alps and the Apennines have secluded
Switzerland from its neighbors. In our own country, Providence has
placed our great mountains on a northern and southern axis; the
slopes, the direction, the prevailing winds, the facilities for
transportation and travel favor no one of our northern, southern, and
western States more than another.
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