32 W. B. Taylor— Recent Researches in Sound. 



son of different instraraents, the character and value of the im- 

 provements made in them and especially an examination of a 

 new fog- signal made under the direction of the Board by Mr, 

 Brown, of New York —the steam siren (p. 194), an inctru- 

 ment which has since played an important part in fog-signal- 

 ing. Employing 1st a large Daboll trumpet. 17 feet long, (its 

 steel tongue being 10 inches long), and operated by a hot air 

 engine, 2nd, a siren operated by a tubular steam boiler, and 

 3rd, a steam whistle, 8 inches in diameter, — an elaborate series 

 of experiments was made as to their penetrating power, as to 

 the most efficient pitch or tone, (p. 95), the effect of varying steam 

 pressure from 20 pounds per square inch to 100 pounds per 

 square inch, (p. 97), the material and shape of the trumpets, 

 &c. (p. 98.) 



[6.] During this series of experiments in 1867, attention was 

 called by General Poe, of the Light House Board, to the cir- 

 cumstance that the sound of the paddle-wheels of a steamer 

 some four and a half miles distant from the shore could be dis- 

 tinctly heard by bringing the ears near to the surface of the 

 beach. This fact had previously been noticed on the northern 

 lakes. The desirability of experimenting with large hearing 

 trumpets placed near the surface of the water is suggested by 

 Professor Henry, (p. 98.) 



[7.] Experiments on the divergence of acoustic beams, while 

 indicating a considerable reduction of sound toward the rear of 

 the trumpet, showed also very strikingly, the increasing ten- 

 dency of sound to spread on' either side of the axis of the 

 trumpet, (p. 98.) This corresponds with the observations [IJ on 

 the employment of sound reflectors. 



An important suggestion is made, requiring experimental 

 determination, namely, that condensed air would prolaably give 

 more efficient results to both the fog-whistle and the siren, 

 than steam. " Prom hypothetical considerations this would ap- 

 pear to be the case, since the intensity of sound depends on 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 

 these instruments are largely filled with steam, the intensity of 

 sound would on this account seem to be less." (Rep., p. 99.) 



In the absence of Professor Henry in England in 1 870, ex- 

 periments were continued by General Duane, one of the Light 

 House District engineers. These will presently be noticed. 



[8.] In 1872 Professor Henry observed from a steamer in the 

 harbor of Portland, Maine, that while approaching an island 

 from which a fog-signal was audible, — at the distance of two 

 or three miles, the sound was lost for nearly a mile, and then 

 slightly regained at nearer approach. This was partly in the 

 rear of the signal ; and from its position on the farther side of 



