Had you left New York or San Francisco at ten o'clock this morning, by noon the day after to-morrow you could step out at Cheyenne. There you would stand at the heart of the world that is the subject of my picture, yet you would look around you in vain for the reality. It is a van ished world. No journeys, save those which memory can take, will bring you to it now. The mountains are there, far and shining, and the sunlight, and the infinite earth, and the air that seems forever the true fountain of youth, — but where is the buffalo, and the wild antelope, and where the horseman with his pasturing thou sands? So like its old self does the sage-brush seem when revisited, that you wait for the horse man to appear. But he will never come again. He rides in his historic yesterday. You will no more see him gallop out of the unchanging silence than you will see Columbus on the unchanging sea come sailing from Palos with his caravels. And yet the horseman is still so near our day that in some chapters of this book, which were published separate at the close of the nineteenth century, the present tense was used. It is true no longer. In those chapters it has been changed, and verbs like is and have now read was and had Time has ﬂowed faster than my ink.