"One moment," said the captain, as he put forth a restraining hand. "What will you do, or how will you act if some one should catch you in the tower?" he asked. Ralph hesitated: "I hadn't thought of that; why,--well,--I suppose I should try to explain it in some way or other," he said. "I am afraid that would not do. Allow me to make a suggestion. Go up boldly, as though you had a perfect right to, or that you did not suspect it was a forbidden place; if some one accosts you look at him in a surprised way, make an apology, and retire; I give you this pointer because you may be flustrated and unable to make a prompt reply, and that would show guilt of some kind," said the captain. Ralph went out and loitered about, gazing at the various pieces of machinery, and finally stood on the steps of the conning tower, which, at the angle of the boat in its inclined position, were almost horizontal. He stretched himself out on the stairs, and turned his head. From that point he 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.