hat's all right," said Blake, and he tried to make his voice sound
hearty. "You are welcome to the light."

"A thousand thanks," murmured Mr. Labenstein, as he bowed himself out.

And then, when the door had closed on him and they had taken the
precaution of closing their transom, Joe burst out in a cautious whisper
with:

"What in the world did you let him take it for, Blake Stewart? Don't you
see what his game is?"

"Yes," was Blake's quiet answer; "I think I do."

"Well, then----"

"What is his game?" asked Charlie.

"I presume he wants to use the flash lamp to give a signal at night to
some German submarine," said Blake quietly--very quietly, under the
circumstances, it might seem.

"And you let him take a light for that?" cried Joe.

"Wait a bit!" advised Blake, and he smiled at his chum. "Do you know
anything about these flashlights, Joe?"

"A little--yes. I know a powerful one, like that you gave Labenstein,
can be seen a long way on a dark night."

"Well, then maybe you know something else about them, or you may have
forgotten it. Like the proverb which says 'blessings brighten as they
vanish,' so the light of these lamps sometimes glows very strong just
before the battery goes on the blink and douses the glim."

Joe looked at his chum for a moment, uncomprehendingly, and then a smile
came over his face.

"Do you mean you gave him a light with a battery in it that was almost
played out?" he asked.

"Exactly," answered Blake, with another smile. "This is a light I have
had for some time. I noticed, only last night, that it was brighter
than usual. Just as a fountain pen--at least, the old-fashioned
kind--used to flow more freely when there were only a few drops of ink
left, so this battery seems to be strongest just before it gives out
altogether.

"I suspected this was going to happen, but I tested the battery with a
galvanometer to-day and I found out it has about ten flashes left. After
that the light will be dead."

"Is that why you gave it to him?" asked Charlie.

"The very reason. As soon as he asked for a light it occurred to me that
he wanted to use it--or might use it--to give a signal at night to some
watching submarine commander waiting for a chance to torpedo us. I
thought if I let him do it with this failing light he might do the Huns
more damage than he could us."

"How?" asked Joe.

"By not being able to give the proper signals. He'll need to flash a
light for some little