We were running under all sail one day when, as I was forward, I saw a line of white water ahead, which I suspected must be caused by a coral reef.  I reported the circumstance.  Fortunately there was but little wind.  I looked out anxiously on either hand to discover an opening.  To the southward the line of foam terminated.  The helm was put down, and the yards braced sharp up; but in five minutes a grating noise was heard and the ship struck heavily.  The seamen rushed from below,--they full well knew the meaning of that ominous sound, and they believed that the ship was hopelessly lost.  The captain at the time was unconscious of everything.  Cousin Silas hurried on deck, and, taking a glance round, ordered the helm to be put up again, the yards to be squared, and the courses which had been clewed up to be let fall.  It was our only chance.  The ship's head swung round; once more she moved--grating on, and, the doctor said, tearing away the work of myriads of polypi. "Hurrah! hurrah!" a shout arose from all forward.  We were free.  Away we flew.