"What's up now?" demanded Ned Rector and Tad in one breath. Every member of the outfit had sprung to his feet. "Sounds like a stampede," flung back the foreman, making a flying leap for his pony. The other cowboys were up like a flash and into their saddles, uttering sharp "ki-yis" and driving in the spurs while they laid their quirts mercilessly over the rumps of the ponies. Tad Butler, Ned Rector and Walter Perkins were not far behind the cowmen in reaching their own ponies and leaping into their saddles. Not so with Chunky. He only paused in his eating long enough to look his surprise and to direct an inquiring look at the Chinaman, while the others went dashing across the plain toward the herd. "Allee same likee this," announced Pong, making a succession of violent gestures that Stacy did not understand. But the boy nodded his head wisely and went on with his eating. Out where the grazing herd had been peacefully eating its noonday meal all was now excitement and action. Revolvers were popping, cowboys were yelling and the herd was surging back and forth, bellowing and dashing in and out, a shifting, confused mass of color and noise. The boys did not know what to make of it. "Yes; they are stampeding," decided Ned, riding alongside of Tad Butler. "I don't believe it," answered Tad. "It looks to me as if something else were the trouble." "What?" "I don't know. It's an awful mix-up, whatever they may call it." "Yes; see! They are fighting." Surely enough, large numbers of the cattle seemed to be arrayed against each other, sending up great clouds of dust as they ran toward each other, locked horns and engaged in desperate conflict. It was noticed, however, that the muleys kept well out of harm's way, standing aloof from the herd and looking on ready to run at the shake of a horn in their direction. "Now, look there! What are they doing?" asked Walter. "They seem to be cutting out a bunch of steers," answered Tad. "That's funny. I can't imagine what it is all about." Neither could Professor Zepplin, who had ridden up at a more leisurely pace, explain to the boys the meaning of the scene they were viewing. "If we knew, we might turn in and help," suggested Walter. "That's right," replied Tad. "Suppose we ride up there where the men are at work. We may find something to do. Anyway, we'll find out what the trouble is." Starting up their ponies, the boys galloped up the line, keeping a safe distance from the herd as they did so, and halting only when they had reached the trail leaders, as the cattle at the head of the line are called. "What's the trouble?" shouted Ned as they came within hailing distance of the perspiring foreman. "Mixed herd," he called back, curtly, driving his pony into the thick of the fight and yelling out his orders to the men. "I know almost as much about it as I did before," announced Ned, disgustedly. "Got any idea, Tad?" "Yes; I have."