On the contrary, where a coast is low and sandy, it is undermined and washed away by the waves, and shoals and sandbars and low islands are formed all along the line of it. The rivers, too, in flowing through such a country, undermine and wear away the banks, and bring down great quantities of sand and gravel to fill the beds of the rivers, and choke up the entrances at their mouths.
These causes operate powerfully in the two portions of the eastern coast of this country. The shores in the northern portion are bold and permanent, and almost every considerable indentation in them forms a deep and safe harbor for shipping. In the southern portion, on the other hand, the coast is lined with shoals and sandy islands; and although there are numerous inlets and bays between and among them, they are almost all shallow, and the approaches to them are choked up with continually shifting sands.
It is so with the rivers. The Hudson river has one-third greater depth of water at its mouth than the Mississippi, although the Mississippi reckons twice as many thousands of miles as the Hudson hundreds, in its length, and discharges, doubtless, into the sea, judging from the area which it drains - more than a hundred times the quantity of water.
From these causes the northern coast is much more accessible to ships coming from sea than the southern, and to this advantage, doubtless, and to the facilities for commerce resulting from it, it is owing, in some considerable degree, that so many early settlements were made on the shores of the northeastern slope, and that the section of country lying contiguous to them has made such rapid advances in wealth and population.
The Western Slope
If we pass now across the country to the western slope, we see a range of mountains running parallel with the coast at a comparatively short distance from the sea. This chain of mountains was named by the Spaniards who first explored the country the Sierra Nevada, which means snowy chain. The strip of land which lies between these mountains and the sea is too narrow to produce any considerable rivers. One, however, is seen crossing the chain of mountains, flowing through a gap or gorge, left, it would almost seem, on purpose to allow a passage. The mouth of this river forms a deep and spacious harbor, the only one of importance upon the coast. It is this harbor that has given rise to the city of San Francisco.
The Great Salt Desert
There remains one more district, and that a most remarkable one, to be described. It is the great desert which lies between the Snowy Chain and the range of mountains which bounds the Mississippi on the west. The desert character of this tract arises, it would seem, from the scarcity of rain, and from the sandy and porous character of the soil, which causes all the water that falls upon it to be absorbed so suddenly that it cannot serve the purposes of vegetation. Streams rise in the mountains around it, and some of them, by the confluence of tributaries, become quite large rivers in going down into the valley. But in flowing over the great sandy waste which here receives them, the water is rapidly absorbed. The streams grow smaller and smaller as they go on, and finally disappear. In the spring of the year, when the snows melt, or in times of great rains, these rivers are swollen so as to extend in length a hundred miles or more, but even at such times they finally dwindle away and disappear.
Some of the rivers, however, before they disappear, reach great hollows or depressions in the land, which depressions, of course, they fill, and thus are formed lakes. The smaller of these lakes, in summer, dry up and disappear, leaving only salt incrustations upon the ground; others being larger, are permanent. There is one, the Great Salt lake, which is some hundreds of miles in extent. The water from these permanent lakes is, of course, all the time infiltrating into the sand below, and evaporating into the air above, but before the whole quantity is exhausted, the rains upon the mountains send down a fresh supply, and thus the vast reservoir is never wholly emptied.
The Deposits of Salt
There is one very curious phenomenon which occurs throughout this region, and that is the tendency to deposit salt, which the waters indicate. The great lake, as its name denotes, is salt, and saline incrustations are found upon the ground in various places where lakes and pools have dried away. It is found to be a general law, though perhaps not universal, that wherever lakes exist that are fed by rivers or other streams flowing over the surface of the ground - and not by springs - and which have no outlet to the sea, they are salt. There may be exceptions, but this is the general law.
For a long time the cause of this phenomenon was enveloped in great mystery, but this mystery has at length been solved. It is found that the earth contains, and continually produces saline substances in the soil. The rain falling upon a district of country dissolves a portion of these substances, and they are borne away by the water into brooks and streams. The quantity is too small to affect the taste of the water while it is in this condition, and so we call the water fresh, and it continues fresh until it reaches the sea.
If, however, it never reaches the sea, but like the water that comes down from the mountain sides into the great American desert it spreads itself out into lakes and pools, and there evaporates, the salt then becomes concentrated so as to manifest itself very decidedly to the taste, and to the other senses. For in the process of evaporation it is the water only that is taken up into the air. The saline particles which it contained are all left behind. Thus the saline element accumulates. Every fresh rain brings down an exceedingly small, it is true, but still an additional supply; and as nothing is taken away, the quantity, after the lapse of ages, becomes very great. The Dead Sea, which is isolated in this manner, and has been for thousands of years receiving a small continual supply from the saline substances which the Jordan and its branches have washed from the soil, has become more salt than the ocean.
The Diggers
The great desert valley which lies thus between the Rocky Mountains and the Snowy Chain of the Pacific, is not wholly desert and uninhabited. There are regions on the mountain sides and in the valleys in which a scanty vegetation thrives, and where reptiles and other animals of a humble order are produced. There are even tribes of Indians low and degraded enough to be fitted to these gloomy and desolate abodes. They are called Diggers, from the fact that they obtain their subsistence by digging into the ground for roots and for snails and reptiles of every kind.
Climate of the Country
For nearly six months of the year, throughout the whole breadth of the continent from east to west, the polar cold, following the sun as he withdraws during that season of the year beyond the equator to the south, comes down from the Arctic regions, and envelopes all the northern half of the country in ice and snow, and then, during the remaining six months, the returning sun brings back warmth, and with it spreads verdure and beauty again over the whole.
During the winter season, all along the northern frontier, the snow in the forests lies often for months at a time four and five feet deep, while the ice is at least half that thickness upon the rivers and ponds. The intensity of the cold of course rapidly diminishes in advancing to the southward, and along the southern frontier it is very seldom that either snow or ice is seen.
It is a singular circumstance that the difference of the temperature at the different seasons of the year is very much greater on this continent than on the other. There is about twice as great a difference between the average heat of summer and winter in Quebec as at Paris, it being here much warmer in the one season and much colder in the other. In Scotland the summers are not warm enough to ripen grapes or Indian corn, and yet in the winters the sheep can feed in their pastures almost without interruption during the whole year. In the corresponding region on this side of the Atlantic, while the rays of the summer sun are sufficiently concentrated and continuous to ripen the grapes and the corn, the winter's cold is so intense that, for six long months, the sheep and cattle have no access to the pasturage at all, the whole surface of the ground having become solid as a rock, and being also buried many feet under the snow.