The riders were frequently killed, but the mail-bags were rarely lost. If a rider did not come in on time, it was known that something serious had happened, and search was immediately made. The riders were not allowed to stop for any purpose whatsoever; neither storms of the greatest severity nor even the presence of hostile Indians near the trail kept them from their duty. One of the few riders who are still living says that he was never afraid except on dark, cloudy nights. At such times he made no attempt to guide his horse, but trusting to the intelligence of the well-trained animal, gave it rein, and at the same time spurred it to its utmost speed. Think of riding at such speed into the dark night, not knowing what is ahead of you! The rider's only safety lay in the carefulness and sagacity of the horse. Such a ride called for more courage than did a conflict with Indians! [Illustration: FIG. 92.--PALISADES OF THE HUMBOLDT RIVER, NEVADA Near the overland trail] The pony express carried no passengers. It carried no freight, not even the usual express package. The messenger was intrusted with nothing but two bundles of letters carefully stowed away in a pair of saddle-bags. The letters were not like our ordinary letters, for the paper used was the thinnest and lightest possible. Hundreds of the letters weighed only a few pounds. It was very important that there should be no great weight, for if the horses were heavily loaded, they could not make the required time. Only those whose business was of great importance could afford to send letters by this express, for the charge was five dollars upon each letter. In spite of the high charge the pony express is said never to have been profitable, for the expenses were very heavy. It was discontinued in 1860, as by that time a telegraph line had been constructed across the continent. HOW CLIMATE AND PHYSICAL FEATURES INFLUENCED THE SETTLEMENT OF THE WEST The story of the exploration and settlement of the Pacific coast, and of the great region lying between the Pacific slope and the Mississippi Valley, offers a most interesting opportunity to study the control which physical features of the earth exert upon the trend of men's activities. The position of the mountains, the courses of the rivers, and the character of the sea-coast have all helped to shape the history of the West. The presence of gold in the rocks of the Sierra Nevada mountains was the chief incentive which led to the breaking down of the barriers placed by Nature between the Pacific and the Mississippi basin.