THE SEA-GIRT FORTRESS CHAPTER I Man Overboard "Where are we now?" asked Oswald Detroit, emerging from the cabin of the Diomeda. "Where "Ask me another," replied his chum, Jack Hamerton, with a merry laugh. "We may be here, we may be there, for all I know. One thing I am certain of: I have just hove the lead, and found that we are in twenty-two fathoms, with a gravelly bottom. That's good enough for me. Also, by dead reckoning, we are three hundred and seventy-eight miles from Lowestoft, and I can't take an observation because of this fog." "You don't seem at all anxious," remarked Detroit, who regarded the wall of thick white mist with evident mistrust. "Why should I? The yacht's as sound as anyone could desire, and we've