d
this was done.

Ten minutes later, however, the "blimp" was so close at hand that there
could be no mistaking its identity. It belonged, beyond a question, to
one of the squadrons of the Royal Naval Air Service.

"Radio message from the 'blimp,' sir," called a messenger, darting from
the doorway of the wireless room. "Do you wish a written copy, sir?"

Lieutenant Fernald glanced at Dave, who shook his head.

"Let's have the message orally," Fernald called down to the deck.

"'Blimp' wants to know, sir, if these two craft are the 'Grigsby' and
'Reed.'"

"Tell the operator to admit the fact," Fernald ordered.

"Officer in charge of the 'blimp,' sir, says that he was to report and
help you yesterday, but that the weather was too foggy."

"Tell the operator to send back: 'Good morning. Glad to have you with us.
Signature, Darrin,'" Dave directed.

The seamen and petty officer at the anti-aircraft gun left their station.
Straight onward came the "blimp," dropping much lower just as it passed
over. From the car beneath the big gas-bag several men leaned over to
wave friendly hands, a greeting that was instantly responded to by Dave's
and Dan's jackies, for the dirigible, after sailing over the "Grigsby,"
turned and floated over the "Reed."

"Message from the 'blimp,' sir," again iterated the messenger on the
deck. "Message says: 'We're to keep near you and try to spot submarines
for you.'"

"More power to your vision," was the message sent back by Dave.

"You're working northward, toward the shoals?" asked "Blimp."

"Yes," Darrin acknowledged.

"That's a likely place to find one or two of the Hun pirates resting,"
"Blimp" continued.

"Always a good hunting ground," Dave assented, in a radio message.

This took place while the dirigible was flying back and forth, ahead and
astern, between the destroyers and to either side of their course.

"It's a fine thing to be able to move at aircraft speed," said Lieutenant
Fernald, rather enviously. "If we could only make such speed, sir!"

"If we could build ships that would steam sixty to a hundred miles an
hour, then the enemy could build them also," Dave returned. "There would
be little, if any, net gain for us. But if we could find the secret of
doubling the speed of aircraft, and keep said secret from the boches,
that would be an achievement that would soon end the war."

For ten miles the sweepers proceeded, with a total "catch" of only three
mines, which