"Yes, very interesting—and some very harrowing. I saw a man drowning not long ago. We were powerless to help him."
"Heavens, what a sight!" exclaimed Foster. "The expression on his face must have been tragic."
"Pitiful—the most pitiful I ever looked at. He seemed to be calling to us. Such agony and despair; but it did not last long."
"But while it did last—did you have a camera? What a chance for a photographer! That is my line, you know. Did ever a photographer get a chance to photograph the expression on the face of a drowning man? What a picture it would be?"
"Don't," said the girl, with a shudder. "For mercy's sake, do not speak of such things."
"I beg your pardon, Miss Fleming," said Ross, gently. "It was very tactless in me."
"And I, Miss Fleming," said Foster, with a bow, "was led away by professional enthusiasm. Please accept my apology, too. Still, lieutenant, I must say that I would like the chance."
"Sorry, Mr. Foster," answered Ross, coldly. "We do all sorts of things to men in the navy, but we don't drown them for the sake of their pictures. Suppose I show you around, for at two bells the men will be back from their dinner. Now, aft here, is the gasoline engine, which we use to propel the boat on the surface. We can't use it submerged, however, on account of the exhaust; so, for under-water work, we use a strong storage battery to work a motor. You see the motor back there, and under this deck is the storage battery—large jars of sulphuric acid and lead. It is a bad combination if salt water floods it."
"How? What happens?" asked Foster.
"Battery gas, or, in chemical terms, chlorine gas is formed. It is one of the most poisonous and suffocating of all gases. That is the real danger in submarine boats—suffocation from chlorine. It will remain so until we get a better form of motive power, liquid or compressed air, perhaps. And here"—Ross led them to a valve wheel amidships—"as though to invite such disaster, they've given us a sea cock."