It was about six o’clock that night that the alarm bell set up a sudden ringing. The professor who was making some calculations on a piece of paper jumped to his feet, and so did a number of the others.
“We are nearing the bottom!” he cried. “The bell has given us warning!”
CHAPTER XV
IN THE STRANGE DRAUGHT
The boys ran to attend to the engines and apparatus to which they had been assigned in view of this emergency. The professor, Washington, Bill, Tom and Andy, who had kept to themselves since the descent, came running out of the small cabin where they usually sat, and wanted to know what it was all about.
“We may hit something, in spite of all precautions,” Mr. Henderson remarked. “Slow down the ship.”
The Mermaid was, accordingly checked in her downward flight, by a liberal use of the gas and the negative gravity machine.
The bell continued to ring, and the dials pointed to the mark that indicated the ship was more than one hundred and fifty miles down.
Mark, who had run to the engine room to check the descent, came back.
“Why didn’t you slow her down?” asked the professor.
“I did,” replied the boy. “The negative gravity and the gas machines are working at full speed.”