In this great Old-World continent there are many highly individualized areas, each separated from the rest of the continent by strong geographical barriers; it has a dozen or so of great peninsulas upon its seaboard, many great islands off its shores, and the interior of the land is divided into many separated regions by mountain ridges or by deserts. It is a land where man necessarily fell into variety, because of the isolation that the geography gave. If we look at the other continents,—namely, the Americas, Africa, and Australia,—we find that they want this varied and detailed structure. They each consist of a great triangular mass, with scanty subordinate divisions. In all of them put together there are not so many great peninsulas as there are in Europe. If we exclude those that are within the Arctic Circle, there are but few on the four regular continents, none of which compare in size or usefulness to man with the greater peninsulas of the Old World. The only one of value is that of Nova Scotia, in North America.
These regular continents are all in the form of triangles, with their apices pointing towards the southern pole. Near either long shore lie the principal mountain systems that give definition to the coast line. The middle portion of each continent is generally a region of plain, somewhat diversified by lesser mountain systems. Along either shore is a narrow fringe of plain land to the east and west of the main mountain chains. Near the northern part of the continent, and aiding to define the base of the triangle, there is another system of mountains having a general east and west course. With the exception of North America, none of these regular continents have seas inclosed within their areas,—such bodies of water as form so striking a feature in the Asiatic continent, which is indeed a land of mediterranean seas.
In a word, these continents are characteristically as simple as the Asiatic continent is varied. Their mass is undivided, and their organic or human histories are necessarily less diversified than in such a land-mass as Asia.
The continent of North America is, of all the triangular continents, the most nearly akin in its structure to the great Old-World land. In the first place, it is the only one of these continents that has the same general conditions of climate; then it has a far greater diversity of form than the similar masses of South America, Africa, and Australia. North America has several considerable seas inclosed within its limits or bordering upon its shores; its mountain systems are more varied in their disposition than in the other regular continents. So that in a way this continent in its structure lies intermediate between the Asiatic type and what is considered the normal form of continents.
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.
The distribution of moisture over the surface of the continent is effected in much the same way as is the distribution of heat. The Gulf Stream gives an abundant rainfall to the States about the Gulf of Mexico lying to the north of that basin; its effects on the rainfall are seen even as far north as the New England States, but they have little effect to the west of the Mississippi River. The high mountains of the Cordilleras cut off the Pacific winds from the centre of the continent, so that very little of the water which flows down to the Gulf of Mexico or to the Atlantic is derived from the Pacific. From the general conditions thus rudely outlined the following arrangement of climates arises. The northern half of the continent is more completely under the dominion of the Arctic Sea than any part of Europe or Asia; the only parts of it fit for the use of civilized man are the northern watershed of the St. Lawrence, the valley of Lake Winnipeg and the Saskatchewan, and the west-coast region as far north as Alaska. The rest of the northern part of the continent is practically barred out from the life of the race by the intensity of the winter cold, and by the brevity of the summer season.