out in luminous relief.

Deep down below the water there is a listening "ear"--a submarine
telephone device through which a submarine betrays its presence; any
sound the undersea boat makes, the beating of the propellers, for
instance, is heard by this ear, and in turn by the ear of the man who
holds the receiver.

Presently the man who is on detector watch grows tense. He listens
attentively and then stands immobile for a moment or so. Then he steps
to a telephone and a bell rings in the chart-house where the captain and
his navigating and watch officers are working out the courses and
positions.

"I hear a submarine signalling, sir," comes the voice from the depths to
the captain who stands by the desk with the receiver at his ear.

"What signal?" barks the skipper.

"MQ repeated several times. Sounds as if one boat was calling another."
(The sailor referred to the practice which submarines have of sending
subaqueous signals to one another, signals which are frequently caught
by listening war-ships of the Allies.)

The captain orders the detector man to miss nothing, and then a general
alarm (to quarters) is passed through the great vessel by word of mouth.
This is no time for the clanging of bells and the like. The lookouts are
advised as to the situation.

"I hope we're not steaming into a nest." The captain frowns and picks up
the telephone. "Anything more?" he asks.

"Still getting signals, sir; same as before; same direction and
distance."

Down to the bridge through a speaking-tube, running from the top of the
forward basket-mast comes a weird voice.

"Bright light, port bow, sir. Distance about 4,000 yards." (Pause.)
"Light growing dim. Very dim now."

From other lookouts come confirmatory words.

"Dim light; port bow."

"The light has gone."

"It's a sub, of course," murmurs an officer. "No craft but a submarine
would carry a night light on her periscope. She must be signalling." A
thrill goes through the battleship. In a minute the big steel fighter
may be lying on her side, stricken; or there may be the opportunity for
a fair fight.

The captain sends an officer below to the detector and changes the
course of the ship. Every one awaits developments, tensely.

The wireless operator enters the chart-house.

"I can't get your message to the ---- (another battleship), sir. I can't
raise her. Been trying for ten minutes."

The officer who has been below at the detector comes up and hears