"What in the world did the passengers have to be frightened about so long as Joe and I stopped the train and averted the disaster? They ought to be tickled."

"Well, they wouldn't be if they knew how that rock came to be on the track. You probably did not see the conductor when he threw some pieces of round wood over the brink into the ravine, but I did, and I know that they were the rollers that were used to bring that bowlder into place after it had been tumbled down from the bluff. There's train-wreckers in this country, I tell you."

Roy's bike was so excited over what might have happened if we had found that railroad half an hour later, that he could not tell a straight story; but this is what I managed to draw from him after much patient and ingenious questioning:

When Joe and I disappeared in one direction and Arthur Hastings and his wheel sped swiftly away in the other, Roy Sheldon seated himself upon the rock with his lamp in his hand, and whistled softly, keeping time with his heels, for a full minute; then he grew tired of doing nothing, jumped off the rock and made a circuit of it, looking closely at it on all sides. It had cut a deep gash in the bluff as it came down, but Roy thought the ditch ought to have stopped it, because it was lower than the track. Somehow Roy could not bring himself to believe that it had come down with speed enough to run across a three foot ditch, up a hill that was eighteen inches high and six feet long, and stop so squarely in the middle of the track.

"There's something rather queer about it," soliloquized the young wheelman, as he moved around the obstruction. "Now, then, what's that?"

Just then something attracted his attention, and he bent over to examine it. It was the print of a foot in the soft earth at the end of one of the sleepers. Roy placed his own foot within it, and found, to his consternation, that it was at least a third larger than his shoe. Then he made another impression beside it, and the difference in size satisfied him beyond all doubt that he had not made that suspicious track himself. There were hobnails in the track, and that proved that none of Roy's party could have stepped in that particular spot, for there were no nails of that sort in their foot-gear.

"This rock was put here for a purpose," said Roy; and when the thought passed through his mind the cold chills crept all over him. "There must have been a good many of them in the gang, for half a dozen men couldn't roll so heavy a weight out of the ditch unless they had something to work with. What's this and this, and those pieces of timber over there?"

The longer the boy continued his investigations, the more he found to confirm the alarming suspicions that had arisen in his mind. The objects that now attracted his notice were several pieces of round wood, with the bark scratched and torn from them, and as many sticks of timber that were likewise covered with wounds and abrasions. There were other large footprints too in abundance—in fact the ground about looked as though a large party of men had been at work there for a long time—and presently the boy discovered marks upon the bowlder itself which might have been made with a spade or crowbar.

"Were we all blind that we didn't notice these things when we first came here?" said Roy to himself. "Probably we were so highly excited that we couldn't notice any thing except the rock. The fiends who put this thing on the track with the intention of wrecking the train ought to be hanged without judge or jury. I am glad I didn't know what I know now, for I wouldn't have had the courage to stay here alone."

Just then the thought flashed through Roy's mind that perhaps the would-be train-wreckers were concealed somewhere in the vicinity waiting for the time when they could descend into the gulf and complete their work, and that their evil eyes might at that very moment be fastened upon him, while they were discussing plans for getting him out of their way. If Joe and Arthur had known all this, would they have been so ready to dash off into the darkness to warn the unsuspecting engineer of his peril? How easily one of those concealed villains could have tumbled both his friends out of their saddles with a shot from a revolver! And what had prevented them, when the boys first started away, from throwing from the top of the bluff an obstruction upon the track that would have sent both the wheelmen to the ground? No doubt it was because Roy and his friends acted with so much promptness that they did not have time to think of it; but hadn't they had plenty of time since then to recover from their surprise and plan vengeance? This fear almost unnerved Roy. He took one step toward his wheel, but the thought that passed through his mind was driven out as quickly as it came. Come what might, he would not desert his post. He would stay there and warn the train, if one of his companions did not succeed in doing it, and in the mean time if those scoundrels wanted a fight, they could have it.