In reaching Leavenworth, I had crossed two of the five divisions of America: the other three lie before me on my way to San Francisco. The eastern slopes of the Alleghanies, or Atlantic coast; their western slopes; the Great Plains; the Grand Plateau, and the Pacific coast--these are the five divisions. Fort Riley, the center of the United States, is upon the border of the third division, the Great Plains. The Atlantic coast is poor and stony, but the slight altitude of the Alleghany chain has prevented its being a hinderance to the passage of population to the West: the second of the divisions is now the richest and most powerful of the five: but the wave of immigration is crossing the Mississippi and Missouri into the Great Plains, and here at Fort Riley we are upon the limit of civilization. This spot is not only the center of the United States and of the continent, but, if Denver had contrived to carry the Pacific Railroad by the Berthoud Pass, would have been the center station upon what Governor Gilpin, of Colorado, calls the “Asiatic and European railway line.” As it is, Columbus in Nebraska has somewhat a better chance of becoming the Washington of the future than has this block-house. Quitting Fort Riley, we found ourselves at once upon the plains. No more sycamore and white-oak and honey-locust; no more of the rich deep green of the cottonwood groves; but yellow earth, yellow flowers, yellow grass, and here and there groves of giant sunflowers with yellow blooms, but no more trees. As the sun set, we came on a body of cavalry marching slowly from the plains toward the fort. Before them, at some little distance, walked a sad-faced man on foot, in sober riding-dress, with a repeating carbine slung across his back. It was Sherman returning from his expedition to Santa Fé. CHAPTER X. LETTER FROM DENVER. MONDAY, _3d September._ MY DEAR ----, Here we are, scalps and all. On Tuesday last, at sundown, we left Fort Riley, and supped at Junction City, the extreme point that “civilization” has reached upon the plains. Civilization means whisky: post-offices don‘t count. It was here that it first dawned upon us that we were being charged 500 dollars to guard the United States Californian mail, with the compensation of the chance of being ourselves able to rob it with impunity. It is at all events the case that we, well armed as the mail officers at Leavenworth insisted on our being, sat inside with forty-two cwt. of mail, in open bags, and over a great portion of the route had only the driver with us, without whose knowledge we could have read all and stolen most of the letters, and with whose knowledge, but against whose will, we could have carried off the whole, leaving him gagged, bound, and at the mercy of the Indians. As it was, a mail-bag fell out one day, without the knowledge of either Dixon or the driver, who were outside, and I had to shout pretty freely before they would pull up.