"Hard to say. Someone who wanted to put the machine out of business, of course. To be frank, however, it all points to Rooney, who had the shift before mine. He blew the whistle for me when his shift was up, and I left from the camp at once. We passed each other about halfway, so no one else would have had much chance to put anything in there, between his departure from the machine and my arrival. However, it has done no harm, so there's no use worrying about it now, but we had better look good, and see if there's any more of it scattered around."
A close search, however, failed to reveal any more of the dangerous explosive, so the two boys crawled out from under the car and mounted the swinging steel platform, where McCarty showed the other which part of the cog-wheels they had seen below each lever controlled. There was a lever to move the car back and forth on its tracks like a steam engine, a lever to put on brakes, one to control the two-ton steel bucket, and another to raise and lower the long steel crane.
"Best way for you to learn to run it is to come on as fireman," he advised. "It's a hot, dirty job, and long hours, but you've got to learn the steam part first before you can become a good runner. You've got to know enough about a steam engine to tell if your fireman is doing his part right—to know whether he is carrying too much or too little steam, and whether he keeps water enough in the boiler all the time. A careless fireman can easily blow up a boiler and wreck his engine, so it pays to keep an eye on your fireman."
"All right. I'll come on as a fireman," agreed Walter, cheerfully.
"That's right," approved McCarty. "It's the only proper way to learn. Here's another thing to think of: Suppose you went on to that machine to-morrow as a runner. You know now how it works, all about the levers, etc. But, take one example. The first thing you may have to do is to move back on another section of track. A section of track is only fifteen feet long, and the part of the car that rests on it covers twelve of the fifteen feet. The section next is butted up against the one the car is on, but is not fastened to it. Across the ends of the two sections the ground men place two six-foot pieces of iron rail, to catch the center wheels of the car. Now, everything is ready for moving, and the ground men signal, 'Go ahead.' You start ahead. Suddenly the ground men, who are watching cry, 'Hold, hold.' When you have heard that cry you know the car is not hitting that second section right. You have to stop that machine, and stop it, not in a second, but in a fraction of a second, or your machine will be off the track and buried in the sand; or, perhaps, even skidded into the ditch, and likely lost to you forever. Do you suppose a green man, with all that array of levers before him, could act quick enough to save his machine and crew? Why, running a steam locomotive is easy compared to running one of these things. Well, I guess we have gone over everything, and we might as well go back to camp. In the morning we will come out and fire up and take a few lessons in actual practice in firing and handling some of the simpler levers."
"Good!" Walter exclaimed. "Say, what's that haze off there in the west? Isn't it smoke?"
"Indian fires," said McCarty. "They burn off parts of the prairies every six months so as to get fresh pasture for their stock. Appearances are deceptive out here. The air is so clear that one can see objects very far distant. Now, how far off would you say that fire is?"
"About ten miles off," Walter guessed.
"It's more than twice that far," declared the other. "It's a queer country we will be entering soon, and I'm thinking we'll see some queer things before we get through this job. But, here we are at the camp. My, that supper smells good."