"Well," said Cassidy, "if that's how you stand we'll let it go at that; but hadn't we better be thinkin' of gettin' back to Palm Beach? Cap'n Nemo, Jr., 'll be lookin' fer ye, an' if you don't show up he'll be worryin'."
"We'll start at once," answered Matt. "All I was delaying for was to get you to go to Turtle Key after the iron chest. Now that it isn't necessary to go there, the quicker we get to Palm Beach, the better."
"Go to your stations, men," said Cassidy to Burke and Harris. "By the same token, I'll go to mine."
Cassidy dropped down below into a small room which contained the gasoline motor, Burke went away to some other part of the ship and Harris climbed into the conning tower. The top of the tower was lowered, and Harris, peering through the lunettes, began communicating the outlook to Cassidy by means of push-buttons.
The fabric of the submarine began to shake and quiver under the spur of the engine. Slowly she backed off the shallow bar where she had grounded, gained deep water, turned and started out into the open sea.
"The trip back to Palm Beach," Harris called down to Matt and his chums, "is to be made with the deck awash. If we was to submerge the Grampus, I'd have to give Cassidy his orders by means of the periscope. There's push-buttons along the edge of the table, an' I can communicate with the engine room from there just as well as from up here."
Matt pushed his head under the black hood of the periscope. The top of the table he found to be a mirror, and upon it was reflected the surface of the sea from the Grampus as a focal point clear out to the horizon's edge.
"This is a fine craft," spoke up Ferral, who had been strolling through the submarine. "That Captain Nemo, Jr., has surely got a head on him to be able to get up such a boat."
"I'm hoping, Dick," said Matt, "that we'll become better acquainted with the Grampus. Just now, though, I'd like to see if we can't get a little information out of the three men in the strong room."
Matt led the way to what Cassidy had called the "foc'sle," and the three boys were soon looking down on the scowling faces of the prisoners.