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.

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 cold as to be scarcely inhabitable.