Immediately afterward, Benson caused the lead fairly to dance a jig on
whatever it touched at bottom.

“What’s the good of that, anyway?” demanded Jacob Farnum.

“You don’t think I’m doing this just for fun, do you, sir?” asked Captain
Jack, with a smile.

“No; I know you generally have an object when you do anything unusual,”
responded the shipbuilder, good-humoredly.

“You know, of course, sir, that noises sound with a good deal of
exaggeration when you hear them under water?”

“Yes; of course.”

“You also know that all three of us have been practicing at telegraphy a
good deal during the past few weeks, because every man who follows the sea
ought to know how to send and receive wireless messages at need.”

“Yes; I know that, Benson.”

“Well, sir, I guess that the lead has been hitting the top of the
’Farnum’s’ hull, and I’ve been tapping out the signal—”

“The signal, ’Come up—rush!’” broke in Hal, with an odd smile.

“Right-o,” nodded Jack Benson.