DISCOURSE OF W. 11. TAYLOK. 345 



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

 partition it gave a sound considerably louder but continuing only 

 L8 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. Bv 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 among the best absorbers and destroyers of sound. A 

 series of experiments was also made on the reflection of sound, (<> 

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

 purpose. A risume 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 different 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 different 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. Atti. Assoc. Albany, A.ug. 1856, pp. 128-131. 



