“I guess it was rats,” said Jack. “They are always in ships.”
“Old wooden ships, yes,” admitted Mark. “But I’ll bet there’s not a rat aboard the Mermaid.”
“Then you were dreaming,” said Jack, as if that settled it.
Mark did not speak further of the noise, but he did considerable thinking. However, the next night there was no further disturbance.
The fourth day out, when everything had passed off well, the engines doing their best, the professor decided to speed them up a bit, since he was satisfied they had “found” themselves as mechanics term it.
“We’ll see how fast we can go through the water,” said Mr. Henderson, “and then I think we can safely turn our course south. We are well beyond the ordinary lines of travel now.”
Having oiled the bearings well, and seen that everything was in place and properly adjusted, the professor and the boys took their places in the conning tower, while Washington, Tom and Bill remained in the engine room. Andy stayed on deck with his gun.
“I might see a big fish, and we could vary our bill of fare,” he said with a laugh.
“Here we go!” exclaimed the professor as he shifted the levers and turned some wheels and valves. “Now we’ll see how fast we can travel.”
As he spoke the Mermaid responded to the added impulse of the compressed air and shot through the water at a terrific speed. The sudden increase in momentum almost threw the boys from their feet, and they would have fallen had they not grasped some projecting levers.