Over the rolling plains they rode, now and then catching sight of distant herds of cattle under the guard of cowboys, again gaining a view of the distant Centre O ranch. But they saw no sign of Molick or Len, nor could they catch, in the direction they were going, a glimpse of the place where the fence work and dam building had been going on. A little later they topped another rise, and began to descend into a sheltered and fertile valley where Mr. Carson usually sent his choice cattle to fatten before shipping them to the dealers in Chicago and elsewhere. As the three came within sight of this valley they saw a strange sight Instead of the cattle quietly grazing, with perhaps small bunches of them wandering now and then to the banks of the stream to get a drink, the whole herd seemed scattered along the water course. And instead of quietly drinking the cattle seemed fighting among themselves. Pushing, struggling, rearing with heads up against one another, bellowing and stampeding. On the outside vainly rode two or three cowboys who were doing their best to keep the rearmost cattle from rushing over those in the front rank, who were nearest the water. "What does it mean?" demanded Mr. Carson of Skinny, as he urged his horse forward. "What does it mean?" "It's a stampede!" cried Dave. "Maybe Len is trying some of his mean tricks again." "It's a trick, but it isn't any like that," said Skinny. "None of that Molick crowd is around here now." "But what's the matter?" demanded the ranchman. "Water--or, rather lack of water," said the cowboy briefly. "The cattle are half mad with thirst I expect. And I guess maybe it isn't so much of a real thirst as it is the fear that there won't be any water left after an hour or two. Cattle know more that way than we give 'em credit for." "This is serious!" exclaimed Mr. Carson. "I thought you'd think so. That's why I come for you," Skinny explained. The three rode down the slope, the confusion among the cattle increasing every moment. "What can you do?" asked Dave. "Have to drive 'em over to the other range, there's water there, I should think," Mr. Carson answered. "That is, if Molick and his bunch haven't tried any of their tricks there." "No, they can't stop the supply there," said Skinny. "It's only here, where the river takes a sharp turn above us, that they could cut off the supply." "Then you think there's no question but that they did it?" as had Dave of Mr. Carson. "Hardly any doubt," was the reply. "But of course I'll look into it. Watch out now, Dave. Those cattle are fairly wild, and I don't want you to be hurt." The ranchman looked affectionately at the youth, and Dave felt a warm spot in his heart for the man who had done so much for him. "I don't believe we can drive 'em back until they've licked up every last drop," said Skinny. "Then they'll know there's no use in stayin' and we may be able to do somethin' with 'em." "Is it drying up as badly as that?" asked Mr. Carson.