The final result of these various surveys was a line with maximum grades of 116 feet to the mile. This does not compare unfavorably with most of the transcontinental routes subsequently built. It is interesting to observe, however, that the Central Pacific summit is some 2,000 feet higher than the altitude of Beckwourth’s Pass, and that the maximum grade of the Western Pacific Railway, built years afterwards through that pass, is only 52.8 feet to the mile, or one per cent. Neither Judah nor his immediate successors, therefore, discovered the best route across the Central Sierras. [Illustration] _Temperature._ A second physical difficulty incident to mountain construction was found in the mountain climate. The summer climate of the Sierras is delightful, at least at altitudes of about 6,000 to 7,000 feet. At lower elevations the temperature is often uncomfortably warm. But the winter climate is quite different. As early as August the nights begin to get cold, the first snows come in November, while in January the trails become impassable, and the high levels are unvisited by man until the following year. The official record shows that the greater part of the mountain construction on the Central Pacific occurred between July, 1866, and July, 1868. Mr. Stanford has testified that both the winter of 1866-67 and that of 1867-68 were unusually severe, and his engineers have dwelt in great detail upon the consequent impediments to their work. Not only did the frozen earth resist pick and shovel, but there were snow banks from 30 to 100 feet deep. It was necessary to remove this snow to permit excavation, and to keep clear the space to be occupied by embankments in order to prevent settling. When the summit was approached tunnels had to be driven through the snow to the rock face. As the whole working force could not be employed in the tunnels, the surplus labor, with all its supplies, was hauled beyond the summit and put to work, at great expense, in the cañons of the Truckee River. The first snow sheds were built in the summer of 1867, and in the following years it was decided to cover all the cuts and points where the road crossed the paths of the great avalanches beyond the summit. The total length of sheds and galleries built by the fall of 1869 was 37 miles, and the cost was $2,000,000.[99] In addition to the difficulties caused by snow, it must be remembered that the frozen earth, though uncovered, was difficult to work. Not only was it necessary to blast out material which could have been cheaply moved at a more favorable time, but, when piled into embankments, the ground settled in the spring as the frost was leaving, and required constant attention.[100]