It would be interesting to consider each of the main lines of railroad which connect the Mississippi Valley with the Pacific, and study the features of the country through which it runs, determining as far as possible the surveyor's reasons for selecting that particular course. Some of the railroads follow for long distances the routes of the emigrants. The emigrants, in their turn, often made use of the ancient Indian trails. [Illustration: FIG. 95.--THE CARSON PASS, SUMMIT OF SIERRA NEVADA MOUNTAINS One of the main emigrant routes to the Pacific Coast] While Nature seems to have striven to raise impassable barriers to shut off the Pacific slope from the rest of the continent, yet she failed at some points, and through the unguarded passes the wild animals and Indians first found their way. Then came the trappers, prospectors, farmers, and at last the railroad, until the wilderness was over-run. Because of its temperate climate, abundant rainfall, and rich soil, the Mississippi Valley was rapidly settled after the pioneers had once reached it. The plains rising slowly westward toward the base of the Rocky Mountains were found to be more arid the farther they were explored. Consequently there exists a broad strip of plain which is even to-day sparsely settled. The emigrants went on to the fertile valleys nearer the Pacific, where the rainfall is more abundant. The American settlers did not then understand irrigation, although it was practised by the Mexicans to the south. Because the discovery of precious metals was first made in California, the pioneers crossed the intervening mountains without giving a thought to the mineral riches which might be concealed in their depths. Later, mines were opened in the mountains all through the arid regions. The necessity of providing food for the miners brought about the discovery that the desert lands were very productive wherever the waters of the streams could be brought to them. THE LIFE OF THE PROSPECTOR Perhaps some of us who have comfortable homes, sleep upon soft beds, wear neat clothes, and can obtain every variety of food that we wish, think with pity of the men who lead a rough and lonely life among the mountains far from all comforts. Let us learn something more about the life and work of the prospectors, for we may find much that is desirable in their experiences. Not many thousands of years ago our ancestors led what we would now call a wild and savage life. They had no permanent homes, but wandered here and there in search of food, and lived in caves or constructed the rudest kind of shelter from the storms. Perhaps we are right in feeling thankful that we were not born in those primitive times, but are there not really many things to regret about the way in which we have to live at the present day?