some minutes more the dirigible moved back and forth through the air,
her observers watching for the presence of hidden enemy craft. Then,
without warning, came the message:

"Sorry, but engine trouble threatens and will compel our return to land,
and to our base if possible."

"The best of luck to you," Dave ordered wirelessed back to these British
comrades. "We'll stand by until we're as close to shore as we can go."

For he knew that, near shore, the shoals became dangerous shallows at
this point on the coast.

Away limped the "blimp," the "Grigsby" following, and standing ready to
do rescue work should the dirigible need assistance.

But the "blimp" not only made her way over to shore, but vanished slowly
in the distance.

All of the mine-sweepers that had come up were ordered by signal to
continue sweeping over the shoals.

"I want to see more of this work personally," Dave told his executive
officer, who was now to be left in command. "Clear away one of the power
launches. I'll take Mr. Ormsby with me."

So Dave was taken over to one of the mine-sweeping, snub-nosed craft that
had formerly been a steam trawler on the Dogger Banks. The commanding
officer, Hartley, proved most glad to welcome them.

"We'll make you as comfortable as we can," promised Hartley.

"Now, please don't do anything of the sort," Darry protested. "Let us be
mere spectators, or pupils, and have no fuss made over us. Instruct your
men, if you'll be good enough, to omit salutes and to chat with us, if
they have a chance, like comrades or pals. We want to see your real
working ways, not a demonstration."

"All right, then," sighed Mr. Hartley, and passed the orders.

"When do you men sleep?" Dave inquired of a sailor who paused to light a
pipe as he stood well up in the bow.

"When the blooming ship is hin dry-dock, sir," answered the British tar.

"Don't you have regular watches?"

"Yes, sir."

"How long are the watches?"

"Usually twenty-four hours in each day, sir."

Darry laughed, for he knew no living man could stand working twenty-four
hours a day for any length of time.

"You were a trawler before you came into this branch of the service?"
Ormsby asked.

"No, sir. Hi was a chimney sweep; that's wot made me good for this bally
old business, sir."

"You like this work?" Ormsby next asked.

"Yes, sir, hit's the next best thing to being killed, sir," was the
solemn response.

"Have you seen any mine-sweepers dest