462 EESEAECHES IN SOUND. 



Experiments by Professok Alexander, in 1855. 



The Liglit-House Board was not content with the employment alone 

 of the fog-sig^nals in ordinary use, but directed a series of experiments 

 in order to improve this branch of its service. For this purpose the 

 board employed Prof. J. H. Alexander, of Baltimore, who made a 

 report on the snbject, which was published among the documents. The 

 investigations of Professor Alexander related especially to the use of 

 the locomotive steam- whistle as a fog-signal, and in his rejiort he details 

 the results of a series of experiments in regard to the nature and adjust- 

 ment of the whistle, the quantity of steam necessary to actuate it, with 

 suggestions as to its general ecouoray and management. He found, 

 what has since been fully shown, that the power of the sound dei)ends 

 upon the pressure of the steam in the boiler, and the pitch upon the 

 distance between the circular oritice through which the steam issues, 

 and the edge of the bell. He appears however to be under an erro- 

 neous impression that the sound is produced by the vibrations of the 

 metal of the goblet or bell, while in fact this latter portion of the appa- 

 ratus is a resounding cavity, which, as I have shown in subsequent 

 experiments, may be constructed of wood as well as of brass, in order 

 to produce the same efl'ect. Mr. Alexander also mentions the effect of 

 the wind in diminishing the penetrating power of sound when in an 

 adverse direction, either directly or approximately. He also recom- 

 mends the adoption of an automatic pump to supply the boilers with 

 water, and also to open and shut the valves at the proper intervals for 

 blowing the whistle. He states that the location of a sound can be 

 determined more j)recisely in the case of loud, high sounds than in that 

 of feebler or lower ones. On this point I am not prepared to concur 

 with him in experiments of my own. In all cases however loud sounds 

 are more desirable than feebler ones, in order that they may be heard 

 at a greater distance above the noise of the surf and that of the wind 

 as it passes through the spars and rigging of vessels. 



The board however at this time were not prepared to adopt these 

 suggestions, and an unsuccessful attempt to use a steam-boiler, rendered 

 aborti\'e by the incapacity of the keeper to give it proper attendance, 

 discouraged for a time efforts in this line. 



Previous to the investigations of Mr. Alexander, at the expense of the 

 Light House Board, Mr. DaboU, of New London, had for several years 

 been exi)erimenting on his own account with reference to a fog-signal. 

 His plan consisted in employing a reed trumpet, constructed after the 

 manner of a clarionet, and sounded by means of air condensed in a res- 

 ervoir, the condensation being iiroduced by horsepower operating 

 through suitable machinery. Although the sound of this was more pene- 

 trating than that of bells, still the expense and inconvenience of the 

 maintenance of a horse, together with the cost of machinery, prevented 

 its adoj)tion. Mr. DaboU however after this i)resented to the board a 



