Our camp is pitched to-day about ten miles west of the 96th meridian. If we were to travel south from this point 350 miles, we should reach Omaha, which is 946 feet above the sea, so that if we were sitting on the bank of the Missouri at that point, we should be just about as high above tide-water as we are while lolling here in the tall rank grass. By going from Omaha to San Francisco over the Pacific Railroad, we see the elevations of the country; then by striking westward from this point to the head-waters of the Missouri, and then down the Columbia, we shall see at once the physical features of the two sections. The engineers of the Pacific Railroad, after gaining the top of the bluff behind Omaha, have a long and apparently level sweep before them. Yet there is a gradually ascending grade. Four hundred and eighty-five miles west of Omaha we come to the 104th meridian, at an elevation of 4,861 feet. If we go west from this point to that meridian, we shall strike it at the mouth of the Yellowstone, 1,970 feet above tide-water. Near the 105th meridian is the highest point on the Union Pacific, at Sherman, which is 8,235 feet above the sea. Three hundred miles beyond Sherman, at Green River, is the lowest point between Omaha and the descent into Salt Lake Valley, 6,112 feet above the ocean level. At that point we are about twenty-six miles west of the 110th meridian. Now going northward to the valley of the Missouri once more, we find that Fort Benton is about the same number of miles west of the same meridian, but the fort is only 2,747 feet above the sea. Just beyond Fort Benton we come to the Rocky Mountains,--the only range to be crossed between Lake Superior and the Columbia. We enter the Deer Lodge Pass near the 112th meridian, where our barometer will show us that we are about five thousand feet above the sea. We find that the miners at work on the western slope have cut a canal through the pass, and have turned the waters of the Missouri into the Columbia. The pass is so level that the traveller can hardly tell when he has reached the dividing line. Going south now along the meridian, we shall find that between Green River and Salt Lake lies the Wasatch Range, which the Union Pacific crosses at an elevation of 7,463 feet at Aspen Station, 940 miles west of Omaha. From that point the line descends to Salt Lake, which is 4,220 feet above the sea. Westward of this, on the 115th meridian, 1,240 miles from Omaha, we reach the top of Humboldt Mountains, 6,169 feet above tide-water, while the elevation is only 1,500 feet on the same meridian in the valley of the Columbia. At Humboldt Lake, 1,493 miles west of Omaha, the rails are at the lowest level of the mountain region, 4,047 feet above the sea. This is a little west of the 119th meridian, about the same longitude as Walla Walla on the great plain of the Columbia, which is less than 400 feet above the sea.