RESEARCHES IN SOUND: 



WITH SPECIAL EEFERENCE TO FOG-SIGXALING. 



By Joseph Henry. 



[From the Annual Reports of the U. S. Light-HoCtse Board.] 



PREFATOKY NOTE. 



[The series of inv^estigatious undertaken by the late Professor Henry 

 in the interest of the light-house service, embracing not only observa- 

 tions more than usually laborious and extended, with regard to the 

 atmospheric conditions affecting tlie propagation of sound to a distance, 

 but varied and elaborate experimental inquiries, as well, with reference 

 to the most efficient character and form of sonorous instruments for 

 fog-signaling i)urposes, commenced as far back as the year 18G5, and 

 continued to the last year of his life. 



These important investigations, though in the language of an official 

 report, they " have resulted in giving us a fog-signal service conceded 

 to be the best in the world,"* have liitherto received so little publicity 

 and attention, owing to the purely official character and channel of their 

 presentation, that their collection and republication here (in advance of 

 of a possible edition of Henry's collected works), appears to be called 

 for in the interests of science, as well as of a just appreciation of the 

 value of his prolonged researches. 



The first part, extracted from the Appendix to the LightHouse Re- 

 port for 1874, comprises a preliminary statement and an account of ob- 

 servations and experiments made by the author, from 1865, at New 



* Executive Document No. 94, Forty-fifth Congress, second session, Senate, p. 2. 

 ThivS is a report to the Hon. Secretary of the Treasury, made since Professor Henry's 

 deatli. To a similar effect, may be quoted an ofiicial statement made five years 

 earlier. In 1873, Major George H. Elliot, of the Light-House Board, commissioned to 

 make a tour of inspection of European light-house establishments, presented the re- 

 sults of his observations abroad in a very able and elaborate report, ]>ul)lishcd by the 

 Senate in 272 octavo pages, with numerous illustrations. In his preliminary report to 

 the Board, dated September 17, 1873, he concludes, that while there are "many details 

 of construction and administration which we can adopt with advantage," (from the 

 British and French light-house systems,) "there are many in which we excel. Our 

 shore fog-signals, particularly, are vastly sujierior, both in numbiT and power."' 

 (Executive Document No. 54, Forty-third Congress, lirst session; Senate, p. 12.) 



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