RESEARCHES IN SOUND. 461 



one-eleventh of the number of hours and half-hours of the whole time. 

 The fog-gun was found to answer a useful purjiose ; vessels by the help 

 of it alone having come into the harbor during a fog at night, as well as 

 in the day, that otherwise could not possiblj^ have entered. This signal 

 was continued until it was superseded by a bell boat. A gun was also 

 used at West Quoddy Head, near the extreme eastern part of Maine. 

 It consisted of a short piece, or carronade, 5 feet long, with a bore of 5^ 

 inches, charged with four pounds of blasting-powder. The i)owder was 

 made up in cartridges and kept in chests in the work-house. The gun 

 was only fired on foggy days, when the steamboat running between Boston 

 and Saint John, New Brunswick, was approaching the light-house from 

 the former place. In going in the other direction the signal was not so 

 much required, because in the former case (of api^roach) the vessel had 

 been for souie time out of sight of hmd, and consequently its position 

 could not be so well known. The firing was commenced with the hear- 

 ing of the steamer's whistle as she was approaching, and as the wind 

 durin^g the fog at this place is generally from the south, the steamer 

 could be heard five or six miles. The firing was continued as frequently 

 as the gun could be loaded until the steamer answered by a signal of 

 three puffs of its whistle. The number of discharges was from one to 

 six, the latter exhausting a keg of powder valued at $8. The keeper of 

 the light-house acted as gunner, without compensation other than his 

 salary. The cost of powder was paid by the steamboat company. The 

 report of the gun was heard from two to six miles. 



This signal has been abandoned, — because of the danger attending its 

 use, — the length of the intervals between the successive explosions, — 

 and the brief duration of the sound, which renders it difficult to deter- 

 mine with accuracy its direction. 



The lamented General Bache, of the Light-House Board, adopted a 

 very ingenious i)lan for an automatic fog-signal, which consisted in tak- 

 ing advantage of a conical opening in the coast, generally designated a 

 blowhole. On the apex of this hole he erected a chimney which termi- 

 nated in a tube surmounted by a locomotive- whistle. By this arrange- 

 ment a loud sound was produced as often as a wave entered the mouth 

 of the indentation. The i)enetrating power of the sound from this 

 arrangement would not be great if it depended merely on the hydro- 

 static pressure of the wave, since this, under fa*'orable circumstances, 

 would not be more than that of a column of water 20 fe-'t high, giving 

 a pressure of about 10 pounds to the square inch. The effect however 

 of the percussion might add considerably to this, though the latter 

 would be confined in effect to a single instant. In regard to the prac- 

 tical result from this arrangement, which was continued in operation 

 for several years, it was found not to obviate the necessity of jjroduc- 

 ing sounds of greater power. It is however founded on an ingenious 

 idea, and may be susceptible of application in other cases. 



