Westward of Humboldt Lake the Central Line rises to the summit of the Sierra Nevadas, crossing them 7,042 feet above the sea, then descending at the rate of 116 feet to the mile into the valley of the Sacramento. Now going back to the plains, to the town of Sidney, which is 410 miles west of Omaha, we find the altitude there the same as at Humboldt Lake. This level does not show itself again till we are well down on the western slope of the Sierra Nevada Range. The entire country between Omaha and Sacramento, with the exception of about 510 miles, is above the level of 4,000 feet, while on the line westward from the point where I am indulging in this topographical revery there are not thirty miles reaching that altitude. With this glance at the configuration of the continent I might make an isometric map in the sand with my fingers, heaping it up to represent the Black Hills at Sherman, a lower ridge to indicate the Wasatch Range, a depression to show the Salt Lake Valley, and then another high ridge to represent the Sierra Nevadas. I might trace the channel of the Missouri and the Columbia, and show that most of this territory is a great plain sloping northward,--that it is lower at Winnipeg than it is here, as low here as it is at Omaha. [Illustration: CONFIGURATION OF THE COUNTRY. The upper line represents the elevations between Omaha and Sacramento, and the lower line between the Red River and Portland, Oregon.] Taking this glance at the physical features of the northern and central portions of the continent, I can see that nature has adapted all this vast area drained by the Missouri and Yellowstone and their tributaries, by the Mississippi, by the Red River, the Assinniboine, the Saskatchawan, and the Columbia, to be the abode, in the future, of uncounted millions of the human race. It is a solitude now, but the vanguard of the approaching multitude is near at hand. The farmer who lives up the stream and tends the ferry where we crossed yesterday has one neighbor within twelve miles; but a twelvemonth hence these acres will have many farm-houses. To-day we have listened to a sermon by the Rev. Dr. Lord, who preached beneath a canvas roof. We were called together by the blowing of a tin trumpet, but a year hence the sweet and solemn tones of church-bells will in all probability echo over these verdant meadows.