The long, dark corridors of the vast automobile and airplane factory were silent. The same old ponderous machines loomed here and there, while smaller ones stood sentry everywhere. At the end of one long alleyway a small light gleamed. Flickering first to the right, then to the left, it cast gigantic shadows against the walls.
Two boys were working over a “mule.” A mule in a factory, as you will remember, is one of those hard-working, snub-nosed little motors that drag trucks about from department to department. The boys were working over the motor of this mule. There came now and then the metallic clink of a wrench, or the tap tap of a hammer, followed by a grunt of satisfaction or disgust.
“There!” Johnny Thompson straightened up and stretched his cramped muscles. “I guess she’s about ready to move.”
The trip across-continent and the return had been accomplished. Aside from the stirring adventure on the desert, they had met with no unusual experiences. The connecting-rods, struck from the steel of mysterious composition, had performed wonderfully well. When measured by instruments that were exact to the ten-thousandth part of an inch, it had been found that they had worn down only thirty-four ten thousandths of an inch, while connecting-rods of the best known commercial steel would have worn one hundred and forty-two ten thousandths of an inch in making the same mileage. Small figures, but in the history of steel they promised to mark an epoch.
The inventor’s mind was improving but he had not as yet succeeded in recalling the formula. While hoping for his recovery, the boys were preparing to make a more rigorous test of this new steel. The company were manufacturing a new type of seaplane. Every afternoon the two boys, togged out in aviator’s garb, were learning to fly this new plane. It was planned that, when the boys found themselves to be perfect masters of this new vehicle of the air, the six connecting-rods should be placed in the motor of the seaplane, and that it be shipped to the Pacific coast. There, under ideal conditions, they were to test out, not only the connecting-rods, but the seaplane, flying, as a last trial, a thousand miles or more.
The pay Johnny had received for the cross-continent trip had enabled him to make a large payment on his debt of honor. As for Pant, he, for the first time in his life, had a savings account.
During their forenoons they were busy in the factory. At times Johnny thought of the vial of dark liquid that reposed on the shelf in the laboratory, the one he had placed there the night he made the analysis of the mysterious steel. At one time while in the laboratory he had glanced up to make sure it was there. It was still in its place. He had been tempted to tell the chemist about it but was afraid of being laughed at.
“Never mind,” he told himself, “in time I will learn to make a chemical analysis myself. Then I’ll see what’s what.”
The question of the strange white fire puzzled him at times. He wondered, too, how the automobile of the contortionist had happened to catch fire in the desert. But these were mere vague wonderings which had no answer.
Though they were well occupied during the day, the boys found time at night for working upon a new, strange problem of which as yet, their friend, Mr. McFarland, the president and manager, knew nothing. It was this problem that occupied their minds at the present moment. It was a stirring moment. Many nights they had spent working over a new type of engine, one that had never been set in a motor vehicle before. Now it was ready for the try-out.