ecutive officer, "I've about concluded that the
enemy mine-laying submarines do not go back to base port for more mines.
They have some method for delivering them near here, and thus the
mine-layers are able to keep more steadily at work."

"That fits in excellently with my idea," Darrin nodded.

"And that would account for the great numbers of mines that the enemy is
able to lay hereabouts, and yet not have many of the craft caught by us,"
Lieutenant Fernald continued.

"Exactly," Dave agreed. "Moreover, the mine-layers take on their new
supplies at night, and do their resting here at night, and get away from
these shoals just before daylight."

"Of course," Fernald agreed. "If they rested here much in the daytime the
aircraft would discover and destroy them."

"We'll both keep at work on our ideas, Fernald," Dave proposed. "Besides,
we can take time to find facts to support our theories. Then we can get
together and start in the biggest smashing of mine-laying craft on
record."

Both paused in their talk to listen to the sudden boom of guns. Judged by
the sound and the wind, the firing was some six miles away.

"Lookout there!" Darrin sang out. "Do you see anything?"

"Yes, sir," came the reply from aloft. "It must be the 'Reed,' sir. She
must have gotten into something stiff, for she's moving shoreward at
slow speed and firing as fast as she can serve her guns. She's firing in
shoreward, sir."

CHAPTER XVI

HITTING CLOSE TO THE SALT TRAIL

"GIVE us a rocket signal if you need help," Dave signalled the attendant
mine-sweeper.

Then to the officer of the watch:

"Give us full speed, and we'll run down to see if the 'Reed' has work
enough for two of our kind."

A little further south he signalled same orders to the patrol boat that
he had given to the mine-sweeper.

Then the "Grigsby" rushed onward as if she scented something of which she
did not wish her crew to be deprived.

As soon as Darrin discovered that Dalzell was using his searchlight he
ordered the "Grigsby's" also to be used. Over the waters the bar of light
swept until it picked up a sight that made the officers on the bridge
gasp for sheer astonishment.

Two submarines, some five hundred yards apart, lay on the surface of the
sea.

Strangest part of all, neither craft was serving its guns. Why they
neither fought nor dived puzzled the "Grigsby's" officers until the
"Reed's" guns ceased firing and her blinkers signalled to Dav