As we were sailing along through the Sound, a herd of porpoises came gambolling by, their black bodies and fins now appearing, now sinking beneath the surface.  Captain Truck had a harpoon ready, and he placed himself in the forechains, with a rope round his waist.  He stood with his weapon high poised in the air, ready to strike.  We were all on the watch.  In a few moments his harpoon flew from his hand.