We grope out in the darkness, and post our pickets in hollows and depressions, where, should the bivouac be approached over the distant ridges, they can best observe objects against the sky. The men are tired; and, as they cannot walk post and keep awake, the utmost vigilance is enjoined on non-commissioned officers. Hour after hour I prowl around among the sentries, giving prompt answer to the muffled challenge that greets me with unvarying watchfulness. At one o'clock Colonel Mason and I, making the rounds together, come suddenly upon a post down among the willows next the stream, and are not halted; but we find the sentinel squatting under the bank, only visible in the starlight, apparently dozing. Stealing upon him from behind, I seize his carbine, and the man springs to his feet. Mason sternly rebukes him for his negligence, and is disposed to order him under guard; but old Sergeant Schreiber, who was never known to neglect a duty in his life, declares that he and the sentry were in conversation, and watching together some object across the stream not half a minute before we came upon them. Everywhere else along our front we find the men alert and watchful. At three o'clock the morning grows chilly, and the yelping of the coyotes out over the prairie is incessant. My orders are to call the General at half-past three; and, making my way through the slumbering groups, I find him rolled in his blanket at the foot of a big cottonwood, sleeping "with one eye open," for he is wide awake in an instant, and I return to my outpost towards the southeast. Outlined against the southern sky is a high ridge, some two miles away. It sweeps around from our left front, where it is lost among the undulations of the prairie. Square to the northeast, some twenty miles distant, the southernmost masses of the Black Hills are tumbled up in sharp relief against the dawn. A faint blush is stealing along the Orient; the ridge line grows darker against the brightening sky; stars overhead are paling, and the boughs of the cottonwoods murmur soft response to the stir of the morning breeze. Objects near at hand no longer baffle our tired eyes, and the faces of my comrades of the guard look drawn and wan in the cold light. We are huddled along a slope which did well enough for night watching; but, as the lay of the land becomes more distinct, we discern, four hundred yards farther out to the southeast, a little conical mound rising from a wave of prairie parallel to our front but shutting off all sight of objects between it and the distant range of heights, so I move my outpost quickly to the new position, and there we find unobstructed view.