“Evidently,” said Ned dryly, “and if I may offer a word of advice, sir, you will examine this chap Gradbarr before he gets a chance to leave the yard—hullo! what’s that?”
A rivet had fallen from the ladder above and dropped clattering to the iron-grated floor behind him. It had been dislodged by Gradbarr’s foot, but the fellow, who had been listening to every word uttered below, was too quick to be discovered by Ned’s upward glance. With the agile movement of a snake, he slipped from the deck and down the ladder before his presence was even suspected.
“Now we will take a look about us,” said Mr. Lockyer; “feel like moving, Sim?”
“Oh, I’m all right now, sir,” said the youngster rising, though rather weakly, to his feet; “say, but that gas does knock a fellow out when it gets going.”
“Yes, but on board the boat, when she is in commission, there will be no danger from it,” declared the inventor; “automatic valves to regulate it safely have been provided for.”
As he spoke he fitted a key to a door in an after bulkhead, similar in all respects to the forward partition, and led the way into a long, low room with steel-riveted walls, filled with peculiar-looking machinery. The boys could make out the forms of cylinders and crankshafts, but every other device about the place was strange to them.
The engine-room was unlike any other they had ever entered. It was spotless, and every bit of metal fairly gleamed and shone. Queer-looking levers and handles were everywhere, and at the farther end of it were several gauges affixed to another steel bulkhead.
“Behind those gauges are the air-tanks to drive the engines,” explained the inventor. “Here are the pumps for compressing it. We can carry a pressure in our tanks of six hundred pounds to the square inch, which is sufficient to drive the boat at thirty miles an hour on the surface, and from eight to fifteen under the water. We have triple propellers, each driven independently. If one breaks down it makes little difference.”
“Wow!” exclaimed Herc. Ned looked astonished. Old Tom only gasped.
“If you can do all that, sir,” he said, “your craft’s the marvel of the age.”