The whistling buoy is also used to some extent in British, French, and German waters, with good results.  The latest use to which it has been put in this country has been to place it off the shoals of Cape Hatteras, where a light ship was wanted but could not live, and where it does almost as well as a light ship would have done.  It is well suited for such broken and turbulent waters, as the rougher the sea the louder its sound.

[Illustration:  Fig. 2.—­BROWN’S bell buoy.]

Bell-Buoys.—­The bell-boat, which is at most a clumsy contrivance, liable to be upset in heavy weather, costly to build, hard to handle, and difficult to keep in repair, has been superseded by the Brown bell-buoy, which was invented by the officer of the lighthouse establishment whose name it bears.  The bell is mounted on the bottom section of an iron buoy 6 feet 6 inches across, which is decked over and fitted with a framework of 3-inch angle-iron 9 feet high, to which a 300-pound bell is rigidly attached.  A radial grooved iron plate is made fast to the frame under the bell and close to it, on which is laid a free cannon-ball.  As the buoy rolls on the sea, this ball rolls on the plate, striking some side of the bell at each motion with such force as to cause it to toll.  Like the whistling-buoy, the bell-buoy sounds the loudest when the sea is the roughest, but the bell-buoy is adapted to shoal water, where the whistling-buoy could not ride; and, if there is any motion to the sea, the bell-buoy will make some sound.  Hence the whistling-buoy is used in roadsteads and the open sea, while the bell-buoy is preferred in harbors, rivers, and the like, where the sound-range needed is shorter, and smoother water usually obtains.  In July, 1883, there were 24 of these bell-buoys in United States waters.  They cost, with their fitments and moorings, about $1,000 each.

Locomotive-Whistles.—­It appears from the evidence given in 1845, before the select committee raised by the English House of Commons, that the use of the locomotive-whistle as a fog-signal was first suggested by Mr. A. Gordon, C.E., who proposed to use air or steam for sounding it, and to place it in the focus of a reflector, or a group of reflectors, to concentrate its sounds into a powerful phonic beam.  It was his idea that the sharpness or shrillness of the whistle constituted its chief value.  And it is conceded that Mr. C.L.  Daboll, under the direction of Prof.  Henry, and at the instance of the United States Lighthouse Board, first practically used it as a fog-signal by erecting one for use at Beaver Tail Point, in Narragansett Bay.  The sounding of the whistle is well described by Price-Edwards, a noted English lighthouse engineer, “as caused by the vibration of the column of air contained within the bell or dome, the vibration being set up by the impact of a current of steam or air at a high pressure.”  It is probable that the metal of the bell is likewise