“Then it will be too late to save any of those on the ship,” observed Mark.

“I’m afraid so,” the scientist made reply.

The Mermaid rested some distance above the surface of the waters. She moved slightly to and fro with the wind, and rocked gently. The professor was examining the broken machinery.

“I have a plan!” suddenly cried Mark.

“What is it?” asked Mr. Henderson.

“Can’t we bore a hole in the tank, insert a small faucet or tap, and let the gas out that way gradually?” asked the boy. “When we get down we can rescue those in danger of fire, and, later, can repair the break.”

“The very thing!” exclaimed Mr. Henderson. “I never thought of that! Here, Washington! Bring me a drill, and a small stop-cock!”

The drill was obtained from the engine room. Working rapidly Mr. Henderson bored a hole in the lower part of the holder. As soon as the metal was penetrated the gas, which was under considerable pressure, rushed from the tank with a hissing sound. At once the Mermaid began to settle rapidly.

But the professor was prepared for this. He thrust the end of the stop-cock into the hole. It was screwed fast and the valve turned. This stopped the flow of gas and checked the descent of the ship. Then, by opening the tap the vapor was allowed to escape gradually, bringing the Flying Mermaid gently to the water.

As the adventurers approached they could see that the vessel was now a mass of flames. The wind was driving the fire toward the forecastle, and the crew had sought refuge aft. But this expedient could not last long, for, already the tongues of fire were licking the sides of the craft and coming nearer and nearer the seemingly doomed men. The vessel was a large one, and heavily laden.