, and with Jack at the engines, Jimmie
insisted upon mounting to the deck again to look about them.

Cool and sweet the air gushed down the little open hatchway upon the
injured man. Under its influence and aided by the ministrations of Ned,
the proprietor of the third "U-13" rapidly gained control of himself.

"Head west southwest," he instructed Ned. "We'll be mighty apt to find
the mouth of the Thames on that course. There are many places I'd rather
go, but you are right--we must have a surgeon!"

Giving the course to Harry, Ned proceeded to do everything in his power
to ease the hurt of their friend.

"On deck, there!" announced Jimmie presently, his face at the hatchway.

"Hello!" answered Ned. "What is it?"

"I see a light about a point off the port bow!"

"What do you make it out to be?"

"I think it is a lighthouse!" declared Jimmie.

"Margate!" murmured Mackinder. "We are safe enough now, but be careful
about the money, boys!"

"Sail ho!" rang out Jimmie's voice again.

CHAPTER XXII

MORE MYSTERY

"What do you see now, Jimmie?" asked Ned anxiously, stepping to the foot
of the ladder.

"There's a small steamer coming up rapidly from the starboard side,"
replied the lookout.

"Perhaps we'd better dive again," suggested Ned.

"Aw, go on!" protested Jimmie. "What's the use of diving every time
anything comes along? We're neutral!"

"We are, yes," agreed Ned, "but this 'U-13' name is not neutral, and if
the steamer is an English vessel they'll probably not stop to ask
questions."

"Why not swing a white light at 'em, then?"

"That's a good idea, too!" agreed Ned. "If they seem to be heading toward
us, just get a white flag going."

"They are not showing any light at all," announced Jimmie. "They're just
sneaking along like an express train."

"Let us know at once if anything happens," Ned responded, turning back to
his patient.

The boys had not long to wait.

Out of the gathering darkness Jimmie saw a burst of flame which lighted
up a portion of the approaching steamer. A bright flash in a wave some
distance in advance of the "U-13" next attracted his attention. The sharp
roar of a cannon came to the ears of all.

"Are they shooting at us?" asked Ned, again approaching the ladder.

"Don't know!" Jimmie replied briefly. "I saw the flash and heard the
noise. There was a splash some distance ahead of us in the water. Maybe
they can't aim straight."

Ned mounted the rungs of t