LIGHTHOUSE ESTABLISHMENT, THE UNITED STATES. 



447 



Tided the funds for that purpose. The results 

 of these tests are given in its Annual Reports 

 for 1879 and for 1880. 



None of the various lighthouse establish- 

 ments have as yet succeeded in producing a 

 light that can be identified as to kind, or lo- 

 cated as to site, at any considerable distance, 

 through a fog, or even through a snow-storm. 

 But earnest effort is made to guide the mariner 

 by sound when sight will not avail, and fog- 

 signals of various kinds have been applied to 

 this purpose. 



In the course of his researches as head of the 

 board's committee on experiments, Professor 

 Henry developed two theories, stating them to 

 be good working hypotheses : one relative to 

 the effect of the wind on the direction of sound, 

 arid the other on the failure of sound to make 

 itself heard at irregular intervals. The effect 

 of the publication on the first has been to 

 cause seamen, wishing to hear a fog-signal 

 against which the wind is blowing, to go aloft 

 as they would to see a distant light, and to 

 go as near to the surface of the water as pos- 

 sible to catch the sound, if the wind is wafting 

 the sound toward them. 



As to the interval in the audibility of a 

 continuous sound, it is now accepted that a 

 fog-signal may be in full blast and audible 

 for a long distance, and inaudible at varying 

 points within that distance, and that the sound 

 may shade off from audibility to inaudibility, 

 and back to audibility, several times in pass- 

 ing from the fog - signal to that point far- 

 thest distant from it where it is clearly heard. 

 Hence mariners understand that, though they 

 may not hear it, still they may be within ear- 

 shot of a fog-signal in operation. They also 

 fully realize the fact that they may, while 

 sailing toward the sound already caught, lose 

 it, and that by continuing their course they 

 may pick it up again. They also understand 

 that, while sailing away from the fog-signal, 

 they may lose its sound and hear it again 

 several times before passing entirely beyond 

 its range of audibility. Therefore, they now 

 make allowances for the variations of the 

 sound of the fog-signal as they do for the va- 

 riations of the mariner's compass, although 

 the law of the variations of its sound has not 

 yet been fully deduced or completely formu- 

 lated. The board's annual reports show some- 

 thing of its gradual but effective labors to 

 wrest from Nature her carefully guarded se- 

 crets, and to utilize the results of this work as 

 rapidly as they are obtained. 



It was within its plans to have continued its 

 researches into the laws of sound by a grand at- 

 tack with all its available forces. Professor 

 Henry was to have been assisted by several 

 scientists, in addition to those officially con- 

 nected with the board, who were to be sta- 

 tioned in steamers and in captive balloons 

 above, at various heights, all to note simulta- 

 neously the degree of audibility in numerical 

 scale of the sound of a powerful fog-signal in full 



blast on a light-ship more than twenty miles 

 from land, so that they would not be puzzled 

 by shore echoes, on which all the various phe- 

 nomena that could be registered by the ther- 

 mometer, the hygrometer, and the anemome- 

 ter, were also to be noted, on charts previously 

 prepared, and it was expected, when all this 

 field work had been plotted, to deduce some- 

 thing of the law of these variations of audi- 

 bility, and to show what allowance may be 

 made for them. The death of Professor Henry 

 caused the postponement rather than the aban- 

 donment of these experiments. Professor 

 Morton, his successor as the scientific adviser 

 of the board, in doing that duty which laid 

 nearest his hand, has brought out the photo- 

 phone, an instrument by which the mariner, 

 when puzzled as to the location of the fog- 

 signal, which, when heard in snow-storm or in 

 fog, seems to come from anywhere, may de- 

 termine its direction to within a point of the 

 compass 



And at this time, although the board has 

 not brought its fog-signal service up to its own 

 standard, it is of large service to commerce, 

 and has been made the subject of study by 

 commissions sent hither by other countries, es- 

 pecially by Brazil and Great Britain ; and it is 

 not too much to say that it is in advance of 

 that of any other lighthouse establishment. 



The principal fog-signals now used by the 

 board are the trumpet, the siren, the steam- 

 whistle, the whistling-buoy, the bell-boat, the 

 bell-buoy, and bells rung by machinery im- 

 pelled by clock-work. 



The board, in 1854, employed Professor J. 

 H. Alexander, of the University of Maryland, 

 to make a series of researches as to the audi- 

 bility of sound in fog and as to the action of 

 fog-signals, and it published the Professor's re- 

 port and circulated it among scientific mechan- 

 ics. During this time, Mr. C. L. Daboll, of 

 New London, Connecticut, had been experi- 

 menting on his own account. Under the en- 

 couragement of the board, he brought out his 

 trumpet fog-signal. His plan was to employ a 

 reed trumpet, made somewhat like a clarionet, 

 and sounded by air condensed in a reservoir 

 by machinery driven first by horse-power, and, 

 later, by a hot-air engine. In it the trumpet 

 is the resounding cavity, and the necessary 

 agitation of the air is produced by the vibra- 

 tion of the tongue-like reed. The trumpet is 

 vertical, curved at the upper part. A first- 

 class trumpet is 17 feet long, including the 

 curvature, has a flaring mouth 38 inches across, 

 while its throat is 3 inches in diameter. The 

 reed is of steel, 10 inches long, 2f inches wide, 

 1 inch thick at the fixed, and half that at the 

 free end. It is driven by an Ericsson hot-air 

 engine, having a 32-inch cylinder with an air 

 chamber 4^- feet across and 6 feet long, which, 

 at a pressure of from 15 to 20 pounds, could 

 make a five-second blast every minute. While 

 the trumpet is not as far-reaching as some 

 other fog-signals, it has been preferred for 



