ometric 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.

Climate affects vegetation and the distribution of animal life, and
thus greatly modifies commerce.

Whatever of importance is accomplished in those countries where
climate has overpowered a race is best and principally done by the men
of the temperate zones, who carry with them perseverance, courage, and
ability, and maintain their ascendency, true to their type, while they
have their life to live.

But with our own eyes we may perceive how much climate affects
agriculture. The humidity or dryness of soils, their natural or
acquired heat or cold, the prevailing winds, the quantity of rain, the
snows, the dews, all affect the planter of the seed and the tiller of
the ground; they increase or diminish the aggregate of the products of
countries, the value of their imports and exports,--in short, their
material power, their resources, their influence, their very
existence.

The climate of our own country is exceedingly variable. The
transitions from heat to cold are very sudden, the range of the
mercury is very great. In the North, we have almost the Arctic
winters; in the South, almost the peculiarities of the tropics. Of the
State of Pennsylvania it has been said, that in this respect it is a
compound of all the countries in the world. Mr. Jefferson and Dr.
Rush, as before observed, insisted that our climate has changed; and
Williams, the historian of Vermont, contends that New England has
deteriorated in its seasons, temperature, harvests, and health, since
its early settlement. Our winds blow from every point of the compass,
but a due north wind is very rare. Our great western lakes have a
large influence on our climate. Some learned men have asserted, that,
if they were land, their area being about ninety-four thousand square
miles, the region would be so