Presently Cassidy, who was using the binoculars, declared that he could see a sail. This compelled the captain to alter his views as to the cause of the firing. If there was a sail, then it was impossible that the cruiser was struggling to destroy the derelict.
Just about then another roar of cannon was heard, this time so weirdly distinct that there could be no doubt as to what had caused the report.
"That's cannon, all right," muttered Cassidy, "but why is a schooner doing the shooting?"
"We'll get inside," said the captain, "and submerge until the periscope ball is just awash. It may be well to come into this thing cautiously."
All those on deck descended to the periscope room. Here, as once before, the captain and Matt kept their eyes on the mirror of the periscope table.
Slowly but clearly a schooner came into sight, and also the wreck of a two-masted brig.
"That brig is the derelict," remarked the captain, "and it looks as though the schooner is trying to sink her."
"Mighty queer to find a schooner carrying cannon," observed Cassidy.
"That's right, too," said the captain, plainly puzzled.
"There are two boats alongside the wreck," said Matt, excitedly, "and men are climbing over the bulwarks! What does that mean, captain?"