In a somewhat similar manner the young of many small animals are conveyed from lake to lake and from river to river, by attaching themselves to the feet and legs of birds, floating or wading in the water.
A great many other curious examples like these of the manner in which nature has provided for the wide dissemination of the minuter forms of animal and vegetable life might be given if time and space would allow.
Glacial Action
Whenever the temperature of a country, either from its great elevation or from its high latitude, is such that the summer cannot thaw the snow and ice which the winter produces, what are called glaciers are formed. These glaciers are beds of solid ice, of many hundred feet in thickness, which are formed in valleys or upon broad slopes of land, and which all the time slowly move down the descent upon which they lie, as if there were a certain slight and imperfect fluidity in the constitution of the ice. When such a glacier has it lower termination in a valley it sometimes ploughs up the ground before it, and deposits stones, which it has brought down upon its surface, in a particular way, and produces other curious effect, the results of the glacial action, by which the geologists feel confident that they can determine, upon a proper examination of any district or valley, whether or not a glacier has ever been at work there.
When these glaciers terminate upon the shore of the sea, the lower edge is forced out over the water by the pressure of a mass above and behind, until the projecting mass, sometimes many hundred feet in thickness, is broken off, falls over, and is borne away by the current or the wind, This is the way in which the immense icebergs that are seen floating about even in the middle of the ocean are formed.
The Glacial Period of North America
It is alleged by geologists that there are abundant evidences of former glacial action throughout all the northern and central parts of North America, and also of Europe and Asia, indicating that at some remote period the climate in all the northern latitudes was very much colder than it is now. Indeed, some astronomical arguments have recently been advanced showing that the earth, by the laws of its motion round the sun, which lead to a change in the position of its axis in relation to the sun, is subject to certain grand oscillations of temperature, in which the regions of the north and of the south poles are alternately made warmer and colder, and that at the present time the condition of the north pole is intermediate between the two extremes. However this may be, there are undoubted geological proofs that in former ages the northern countries, both of the old continent and the new, have been at one period much colder, and at another much warmer, than at present. When the climate was colder the reign of ice in all the northern regions, and the influence of it in connecting continents and transporting animals and men, would be of course greatly increased. If now we suppose that at such a time great numbers of the then existing species of animals were transported across the intervening seas, and then gradually spread themselves southward, undergoing slow modifications as they advance, to fit them for the new conditions to which the changes of the climate or their own changes of habitation exposed them, we should have very nearly the result which is now observed to exist.
These ideas, however, are, after all, at present only the speculations of naturalists and philosophers, ingenious and interesting as they are.
Physical Features of the Country
Chapter 2. Face of the Country
The Map
The map on the adjoining page represents the portion of the North American continent which is at the present time occupied by the people of the United States. It will assist very much in reading intelligently the history of the country if we first obtain a clear and comprehensive view of the great and leading features of its geography.
These features are very marked and striking - more so, perhaps, than those of any other country on the globe. This will clearly appear by an inspection of the map, and by filling out, in imagination, the outline which the map presents, with the details which will be given in this description.
As you look upon the map imagine that you are in the air, looking down upon it as from a balloon, and take notice of what you see. On the east and on the west are the shores of two oceans, That on the east is the Atlantic. The Pacific is on the west.
The Lake Country.
Toward the north is an immense tract of nearly level land, covered with forests, but containing a vast number of depressions in the surface of the land, all of which are filled with water and form lakes, some large and others small. This land, though level, is high, so that there is a very considerable though gradual descent from the lakes to the ocean. The lakes are kept constantly full by the rains and by the melting of the snows, and the surplus waters flow off in one vast channel, northward and eastward to the sea.
One of the large lakes, though still much higher than the sea, is marked as a low lake, for it is two or three hundred feet below the level of the others, and the water flowing from the upper lakes into it, in descending from one level to the other, passes over a high precipice, thus producing an immense fall, which is the celebrated Niagara.
The surplus waters of all the large lakes flow off finally in a northeasterly direction, almost exactly parallel to the coast until they reach the sea. The river thus formed is now known as the St. Lawrence. Observe, that between the river and the coast there is a long and somewhat narrow strip of land, which will be spoken of more particularly under another head. All this region of the lakes is inhabited - during the summer season by immense numbers of beasts upon the land, of birds in the regions of the air, and of fishes in the water. In the winter it is buried deep in ice and snow. The birds at that season have all flown. The animals have retired to dens and holes, where some sleep, torpid, till the spring returns, and others burrowing beneath the frosty covering which clothes the ground, gain their livelihood there by digging for roots, or gnawing the bark of trees, or catching the fish that are still swimming in the imprisoned waters.
Fur-Bearing Animals
Almost all the land animals that inhabit these regions - being exposed for six months in the year to intense cold - are protected by a thick and warm coat of hair and fur. In the larger animals the hair is coarse, but thick and warm, though much less so than in the case of the smaller animals; for the smaller the body is that is exposed, the more perfect the protection that it requires, one large mass being more easily kept warm than a multitude of small ones.
The region of these lakes, and of the country north of it, which, for many hundreds of miles, maintains the same character, is one of the most extensive and most celebrated fur-bearing districts in the world. The shores of the lakes, and the banks of all the millions of little brooks and streams, are full of minks, otter, beavers, sables, and multitudes of other swimming and burrowing animals of that kind, whose fur is softer than silk and warmer than wool. When, therefore, you look upon the map and imagine that your eyes are surveying the real country, you must picture it to your mind as swarming with all this life, winter and summer.
In the summer these animals ramble about in the forests, or along the borders of the lakes and streams, amid a profusion of the most luxuriant and most beautiful flowers. Some climb the trees, and run along upon the branches in search of nuts for their winter stores. Some burrow in the ground, at the margin of the water, with the orifices of their dwelling convenient either for foraging upon the land, or for fishing and swimming in the ponds and streams.