Familiar as the boys were with submarine construction, it was an easy task for them to aid the inventor in unclamping the deck ventilators. The gas rushed out in their faces, but they stepped aside and it did not harm them. All this was watched from the shadows of a corner of the shed by Gradbarr.
“Looks like I’ve failed, after all,” he muttered, as presently, the gas having cleared off, the inventor decided it was safe to descend and they entered the conning tower.
Stealthily as a cat, the machinist crept from his hiding place, and, ascending the ladder, followed them.
Within the conning tower the lads found themselves upon a steel ladder with chain hand-rails, much like what they had been accustomed to on a man-of-war. Descending this with quick, nervous steps, Lockyer darted for a door opening in the bulkhead at one end of the chamber, at the foot of the ladder, which was about ten by twenty feet. From this door slow, lazy curls of smoke were coming. Thanks to the opened ventilators, however, the interior of the submarine was comparatively free of gases, and the inventor unhesitatingly passed through the door. As he did so his foot caught against a soft, yielding object. The next instant a quick glance downward showed him that he had tripped on the recumbent form of a boy. In his hand the lad clutched a wrench. Stooping swiftly, Lockyer picked him up and bore him out into the other chamber, where, assisted by the boys, he stretched him upon a bench. Although the lad’s cheeks were ghastly pale, his chest was heaving, and presently he opened his eyes.
“Thank goodness you are all right, then, Sim!” breathed Mr. Lockyer. The lad, a slight young chap of about sixteen, with a mop of curly hair and large, round blue eyes, looked up at him.
“Did I do it, Mr. Lockyer? Did I do it?”
“Do what?” asked the inventor, in the indulgent tone he might have used to one whose mind was wandering.
“Why, turn off the gas valve. I tried to; but I don’t know if I made good before everything began to get wavy and it all went dark.”
“I don’t understand you,” said the inventor; “I thought the gas came from a leak. Do you mean that some one was tampering with the valve?”