Night came on, and the Grampus was still running circles in the waters of the gulf. The sea had quieted down to an abnormal smoothness, and the submarine, with Matt at the engine to relieve Gaines, went on her aimless wanderings.
At midnight Gaines took the engine and gave Matt an opportunity to secure a little rest.
Matt was up for breakfast, and while he, and Captain Nemo, Jr., and Gaines were eating, they heard a muffled detonation, as it might have been of a blast from a great distance. Matt and the captain hurried to the deck, where they found that the mysterious noise had likewise claimed the attention of Cassidy.
"What did it sound like to you, Cassidy?" asked the captain.
"Like a cannon, sir," was the reply, "but it was a powerful ways off."
"That's how it sounded to me."
"What do you think it is?" inquired Matt.
"At a guess," replied the captain, "I should say the cruiser has found the derelict and is trying to break her up. We'll alter our course and see what we can discover."
Just as the Grampus was put on a new tack, there came another of the muffled crashes, which served to give them a further clue as to the location of the firing.
Gaines was told to speed up the motor to the top notch, and the submarine began to cleave her way through the water at her best speed.