DISCOUESE OF W. B. TAYLOR. 345 



feeble tone continuing for 88 seconds, against a lath and plaster 

 partition it gave a sound considerably louder but continuing only 

 18 seconds. On a large block of soft india-rubber resting on the 

 marble slab, the vibration was very rapidly extinguished, but with- 

 out giving any sensible sound. This anomaly required an explana- 

 tion. By means of a compound wire of copper and iron inserted 

 into the piece of rubber, and having the extremities connected with 

 a thermo-galvanometer, it was found that in this case the acoustic 

 vibrations were converted into heat. Sheets of india-rubber there- 

 fore are amon^ the best absorbers and destrovers of sound. A 

 series of experiments was also made on the reflection of sound, to 

 determine the materials least adapted, and those best adapted^to this 

 purpose. A resume of these researches, having reference to the 

 acoustic properties of public halls, was read before the American 

 Association in August, 1856.* 



In 1865, as Chairman of the Committee of Experiments of the 

 U. S. Light-House Board, Henry commenced an extended series of 

 observations on the conduct and intensity of sound at a distance, 

 under varying meteorological conditions. Well aware that for the 

 practical purposes of giving increased security to navigation, the 

 experiments of the laboratory were of little value, he undertook a 

 number of experimental trips on board sailing vessels, and on 

 steamers, in order to make his observations under the actual con- 

 ditions of the required service. As many of his investigations 

 demanded intelligent co-operation, and sometimes at the distances of 

 many miles, he associated with him at diiferent times, among mem- 

 bers of the Light-House Establishment, Commodore Powell, Com- 

 modore Case, Admiral Trenchard, Commander Walker, Captain 

 Upshur, General Poe, General Barnard, General Woodruff, Mr. 

 Lederle, and other engineers of diiferent Light-House Districts, 

 and outside of the establishment. Dr. Welling and others. 



At the outset of his experiments, he found that sound reflectors, 

 which play so interesting a part in lecture-room exhibitions, were 

 practically worthless (of whatever available dimensions) for the 

 purpose of directing or concentrating powerful sounds to any con- 



* * Proceed. Am. Assoc. Albany, Aug. 1S56, pp. 128-131. 



