could see the red liquid in the glass column, but it
was difficult to read the figures.

The glare from the electric light interfered with his sight, and before
he had an opportunity to get a glimpse of the figures from his new
position, one of the petty officers crawled along the passageway, and,
noticing him lying on the stairs, peremptorily ordered him to get down.

Ralph glanced at the man, smiled at him, and promptly complied,
chagrined at his failure. As he entered the little room the captain
eagerly questioned him: "What did it say?" he asked.

"That fellow ordered me away before I could make out the figures," said
Ralph, "but I'm going to try it again."

"How near was the liquid from the top of the glass tube?" asked the
captain.

"Well, I should say about so far," replied Ralph, indicating space
between his thumb and finger. "I guess it was about an inch."

"How long do you think the tube is?" asked the captain.

"I think it must be a foot long; probably more," was the answer.

"I asked you to give me an estimate of the length of the entire tube so
as to give me some assurance that you knew the value of an inch. You
were right; those tubes are twelve inches long. Now let me see; I ought
to know what figures are an inch from the top!" remarked the captain
thoughtfully.

"Pardon me, Captain, but how does it come that you know all about these
boats?" asked Alfred.

"I used to be an officer on a French submarine," he replied in a quiet
tone, and immediately proceeded to make certain mental calculations.
Then he continued: "One inch below the top! That is twenty."

"Twenty what?" asked Ralph.

"Twenty feet; the Germans have the English foot on all their boats. I
wonder they didn't think about that, and make a change before starting
out."

"Maybe it's twenty meters," said Alfred, with a slight laugh.

"Oh, no," replied the captain. "That would be too Frenchy for the
Germans. Besides, it would be too much by all odds. I am sure the
conning tower is not more than twenty feet below the surface of the
water."

"Then the stern of the submarine must be sticking out of the water,"
remarked Alfred.

"Unquestionably," replied the captain.

"How far, do you suppose?" asked Ralph.

"We can easily figure that out," said the captain. "Let me see; we must
first get the angle at which the boat is lying."

[Illustration: _The Entangled Submarine_]

After looking about for some time he continued: "The door j