Although this varied structure of the continent of North America makes it more fit for the uses of man than the continents of Africa, South America, and Australia, there are certain considerable disadvantages in its physical conditions. To show the relation of these evil and fortunate features, it will be necessary for us to consider the general geography of the continent somewhat in detail.
The point of first importance concerns the distribution of heat and moisture over the surface of the land; for on these features depends the fitness of the land for all forms of life. The influences which principally determine the climate of a continent come to it from the neighboring seas. The moisture arises there, and finds its way thence to the land; and the heat or coolness which modifies the land climate comes with it.
North America faces three oceans. On the north is the extremely cold Arctic Sea, mostly covered by enduring ice: it is the extreme coldness of this sea, and its ice-clad character near the continent of America, that in good part causes the great severity of its winters. Where the Arctic Sea lies against Europe and Asia it is partly warmed by the Gulf Stream, and so is not completely ice-bound even in winter; but that part of it which lies near the northern coast of America is ice-bound the whole year, and the winds that come from it are many degrees below those that come over open water.
Both the Atlantic and Pacific oceans send streams of warm water against the American coast. But the Gulf Stream has actually very little direct effect upon our climate; it only touches the coast about the Gulf of Mexico, where the temperature is naturally so high that its warming power is not felt. It then leaves our coast, to give its warmth to the shores of Europe and to the European part of the Arctic Ocean. The Pacific current corresponding to the Gulf Stream is feebler than the Atlantic current, and sends its tide of waters against the northwest shore of America. Its effects on that coast are very noticeable; but they are limited, by the geography of that shore, within narrow bounds. In the first place, the passage of Behring’s Strait is too small to permit its waters to have access to the Arctic Sea; then the high ranges of the Cordilleras fence off the interior of the continent, so that the warm winds that blow from the sea cannot penetrate far to the east. Confined to the shore, the heat of the Pacific Gulf Stream generates a large amount of fog; this fog shuts off the sun’s rays, and so lowers the temperature almost as much as the current itself serves to raise it.