Far up in the Northwest, along the banks of the broad, winding stream the Sioux call the Elk, a train of white-topped army-wagons is slowly crawling eastward. The October sun is hot at noon-day, and the dust from the loose soil rises like heavy smoke and powders every face and form in the guarding battalion so that features are wellnigh indistinguishable. Four companies of stalwart, sinewy infantry, with their brown rifles slung over the shoulder, are striding along in dispersed order, covering the exposed southern flank from sudden attack, while farther out along the ridge-line, and far to the front and rear, cavalry skirmishers and scouts are riding to and fro, searching every hollow and ravine, peering cautiously over every "divide," and signalling "halt" or "forward" as the indications warrant.