gle for breath in the suddenly darkened hull. Almost as if it had happened half an hour ago, I saw it.
"Thank God for telautomatics," I murmured, as the thought swept over me of what we had escaped. "No one was aboard her, at least."
Chlorine was escaping rapidly from the overturned storage batteries, for a grave danger lurks in the presence of sea water, in a submarine, in combination with any of the sulphuric acid. Salt water and sulphuric acid produce chlorine gas, and a pint of it inside a good-sized submarine would be sufficient to render unconscious the crew of a boat. I began to realise the risks we had run, which my confidence in Captain Shirley had minimised. I wondered whether hydrogen in dangerous quantities might not be given off, and with the short-circuiting of the batteries perhaps explode. Nothing more happened, however. All kinds of theories suggested themselves. Perhaps in some way the gasoline motor had been started while the boat was depressed, the "gas" had escaped, combined with air, and a spark had caused an explosion. There were so many possibilities that it staggered me. Captain Shirley sat stunned.
Yet here was the one great question, Whence had come the impulse that had sent the famous Z99 to her fate?
"Could it have been through something internal?" I asked. "Could a current from one of the batteries have influenced the receiving apparatus?"
"No," replied the captain mechanically. "I have a secret method of protecting my receiving instruments from such impulses within the hull."
