720 



SOUND-SIGNALS. 



clearly heard seven miles away. Dr. Gladstone 

 records great variability in the range of gun- 

 sound in the Holyhead experiments. Prof. 

 Henry says that a twenty-four-pounder was 

 used at Point Boneta, San Francisco Bay, Cal., 

 in 1856-'57, and that, by the help of it alone, 

 vessels came into the harbor during the fog at 

 night as well as in the day, which otherwise 

 could not have entered. The gun was fired 

 every half -hour, night and day, during foggy 

 and thick weather in the first year, except for 

 a time when powder was lacking. During the 

 second year there were 1,582 discharges. It 

 was finally superseded by a bell-boat, which in 

 its turn was after a time replaced by a siren. 

 A gun was also used at West Quoddy Head, 

 Maine. It was a carronade, five feet long, with 

 a bore of 5J inches, charged with four pounds 

 of powder. The gun was fired on foggy days 

 when the Boston steamer was approaching the 

 lighthouse from St. Johns, and the firing was 

 begun when the steamer's whistle was heard, 

 often when she was six miles away, and was 

 kept up as fast as the gun could be loaded, 

 until the steamer answered with its whistle. 

 The report of the gun was heard from two to 

 six miles. " This signal was abandoned, 1 ' Prof. 

 Henry says, " because of the danger attending 

 its use, the length of intervals between succes- 

 sive explosions, and the brief duration of the 

 sound, which renders it difficult to determine 

 its direction with accuracy." In 1872 there 

 were three fog-guns on the English coast, iron 

 eighteen-pounders, carrying a three-pound 

 charge of powder, which were fired at intervals 

 of fifteen minutes in two places, and of twenty 

 minutes in the other. The average duration 

 of fog at these stations was said to be about 

 six hours, and, as it not unfrequently lasted 

 twenty hours, each gun required two gunners, 

 who had to undergo severe labor, and the risk 

 of remissnessand irregularity was considerable. 

 In 1881 the interval between charges was re- 

 duced to ten minutes. The Trinity House, in 

 its experiments at South Foreland, found that 

 the short twenty-four-pound howitzer gave a 

 better sound than the long eighteen-pounder. 

 Tyndall, who had charge of the experiments, 

 sums up as to the use of the guns as fog-signals 

 by saying : 



The duration of the sound is so short that, unless 

 the observer is prepared beforehand, the sound, 

 through lack of attention, rather than through its own 

 powenessness, is liable to be unheard. Its liability 

 to be quenched by local sound is so great that it is 

 sometimes obliterated by a puff of wind taking pos- 

 session of the ears at the time of its arrival. Its lia- 

 bility to be quenched by an opposing wind, so as to be 

 practically useless at a very short distance to wind- 

 ward, is very remarkable. . . . Still, notwithstand- 

 ing these drawbacks, I think the gun is entitled to 

 rank as a first-class signal. 



The minute gun at sea is known the world 

 over as a signal of distress. The English light- 

 ships fire guns to attract the attention of the 

 life-boat crew when shipwrecks take place in 

 sight of the 3hips, but out of sight of the boats ; 



and guns are used as signals of approaching 

 floods at freshet-times in various countries. 



Rockets. As a signal in rock lighthouses, 

 where it would be impossible to mount large 

 pieces of apparatus, the use of a gun-cotton 

 rocket has been suggested by Sir Eichard Col- 

 linson, deputy-master of the Trinity House. A 

 charge of gun-cotton is inclosed in the head of 

 a rocket, which is projected to the height of 

 perhaps 1,000 feet, when the cotton is exploded, 

 and the sound shed in all directions. Compara- 

 tive experiments with the howitzer and rocket 

 showed that the howitzer "was beaten by a 

 rocket containing twelve ounces, eight ounces, 

 and even four ounces of gun-cotton. Large 

 charges do not show themselves so superior to 

 small charges as might be expected. Some of the 

 rockets were heard at a distance of twenty-five 

 miles. Tyndall proposes to call it the Collinson 

 rocket, and suggests that it might be used in 

 lighthouses and light-ships as a signal by naval 

 vessels. 



Bells. Bells are in use at every United States 

 light-station, and at many they are run by 

 machinery actuated by clock-work, made by 

 Mr. Stevens, of Boston, who, at the suggestion 

 of the Lighthouse Board, has introduced an 

 escapement arrangement moved by a small 

 weight, while a larger weight operates the 

 machinery which strikes the bell. These bells 

 weigh from 300 to 3,000 pounds. There are 

 about 125 in use on the coasts of the United 

 States. Experiments made by the engineers 

 of the French Lighthouse Establishment, in 

 1861-'62, showed that the range of bell-sounds 

 can be increased with the rapidity of the bell- 

 strokes, and that the relative distances for 15, 

 25, and 60 bell-strokes a minute were in the 

 ratio of 1, l T Vb> and ly 2 ^. The French also, 

 with .a hemispherical iron reflector backed 

 with Portland cement, increased the bell range 

 in the ratio of 147 to 100 over a horizontal 

 arc of 60, beyond which its effect gradually 

 diminished. The actual effective range of the 

 bell-sound, whatever the bell-size, is compar- 

 atively short, and, like the gong, it is used only 

 where it needs to be heard for short distances. 

 Mr. Cunningham, Secretary of the Scottish 

 Lighthouse Establishment, in a paper on fog- 

 signals, read in February, 1863, says the bell at 

 Howth, weighing 2 tons, struck four times a 

 minute by a 60-pound hammer falling ten 

 inches, has been heard only one mile to wind- 

 ward against a light breeze during fog; and 

 that a similar bell at Kingston, struck eight 

 times a minute, had been so heard three miles 

 away as to enable the steamer to make her 

 harbor from that distance. Mr. Beaseley, C. 

 E., in a lecture on coast fog-signals, May 24, 

 1872, speaks of these bells as unusually large, 

 saying that they and the one at Ballycottin are 

 the largest on their coasts, the only others 

 which compare with them being those at Stark 

 Point and South Stack, which weigh 31f cwt. 

 and 41 cwt. respectively. Mr. Cunningham, 

 speaking of the fog-bells at Bell Rock and 





