480 RESEARCHES IN SOUND. 



would have shown a much greater divergency. It should be observed 

 however that the mouth of the trumpet in this case was 38 inches, which 

 is unusually large. 



From the experiments made near New Haven, and also from those at 

 this station, it appears that the actual amount of ijower to produce sound 

 of a given i)enetration is absolutely less with a reed trumpet than with a 

 locomotive whistle. This fact ijrobably finds its explanation in the cir- 

 cumstance that in each of these instruments the loudness of the sound 

 is due to the vibration of the air in the interior of the trumpet and in 

 the bell of the whistle, each of these being a resounding cavity; and 

 furthermore that in these cavities the air is put in a state of sustained 

 vibration by the undulations of a tongue, in the one case of metal, in 

 the other of air ; and furthermore it requires much more steam to set 

 the air in motion by the tongue of air than by the solid tongue of steel, 

 the former requiring a considerable portion of the motive power to give 

 the current of which it consists the proper degree of stillness, if I may 

 use the word, to produce the necessary rapidity of oscillation. But what- 

 ever may be said in regard to this supposition, it is evident, in case reli- 

 able hot-air engines cannot be obtained, that the Daboll trumpet may be 

 operated by a steam-engine, although at an increased cost of mainte- 

 nance, but this increase we think will still not be in proportion to the 

 sound obtained in comparison with the whistle. 



Another question which naturally arises, but which has not yet been 

 definitely settled by experment, is whether both the siren and the whis- 

 tle would not, equally with the trumpet, give more efficient results when 

 worked by condensed air than by steam. 



From hypothetical considerations this would appear to be the case, 

 since the intensity of sound depends upon the density of the medium in 

 which it is produced ; and as the steam is considerably lighter than air, 

 and as the cavities of all of these instruments are largely filled with steam, 

 the intensity of sound would, on this account, seem to be less than if 

 filled with air. 



At the conclusion of the experiments at Sandy Hook, the siren was 

 adopted as a fog-signal, in addition to the reed-trumpet and the locomo- 

 tive-whistle, to be applied to the more important stations, while large 

 bells were retained for points at which fog-signals were required to be 

 heard at but comparatively small distances. These instruments of the 

 first class being adopted, it became of importance to determine, in actual 

 practice, the cost of maintenance, the best method of working them, and 

 any other facts which might have a bearing on their use. 



But as investigations of this kind would require much time and pecu- 

 liar advantages as to location and mechanical appliances, this matter 

 was referred to General Duane, the engineer in charge of the 1st and 

 2d light-house districts, who had peculiar facihties near his residence, 

 at Portland, Me., in the way of workshops and other conveniences, and 

 who, from his established reputation for ingenuity and practical skill 



