Now and then a whistle sounded at a distance in one direction or another, and once they heard the slow, steady beat of a propeller through the enveloping mist, but no craft came very near them, and _The Dart_, proceeding slowly and cautiously, with Harry winding lugubrious wails of warning from the patent fog-horn every half minute or so and Kendall straining his eyes into the gray wall ahead, slid through the water.
