53 8 The Smithsonian Institution 



One of these is a paper read by Henry before the American 

 Association for the Advancement of Science in 1856. Its title 

 was " On Acoustics Applied to Public Buildings." He had 

 been required by act of Congress to build a lecture hall in 

 the building which was erected for the home of the Smith- 

 sonian Institution, and he desired to make it acoustically 

 perfect if possible. He had also been consulted, along with 

 Professor Bache, of the Coast Survey, as to the hall of the 

 House of Representatives, which was about to be constructed 

 in the new wing of the Capitol building. With characteristic 

 thoroughness he took hold of the problem, and in its study 

 combined both observation and experiment. He visited the 

 principal halls and churches of Philadelphia, New York, and 

 Boston, and also made an extensive series of experiments 

 upon reflection, resonance, and refraction of sound in rooms 

 and halls of various forms and sizes. 



The results of these investigations were utilized in the con- 

 struction of the Smithsonian hall, which proved to be entirely 

 satisfactory. The paper in which they are embodied is one 

 of the few important and valuable contributions toward the 

 solution of a problem which is still perplexing. 



The Report for 1875 contains a very interesting discussion 

 of the laws of refraction of sound, by Doctor William B. 

 Taylor. It is first shown that the velocity of a sound-wave 

 in passing through a gaseous medium may be disturbed by 

 variation in the density of the medium, or in its elasticity or 

 temperature, and also by relative motion of the parts of the 

 medium ; that is, by the existence of currents. Whatever 

 produces variations of velocity in different parts of the wave- 

 front will cause refraction, as the direction of a sound at 

 any point is perpendicular to the wave-front at that point. 

 Refraction due to variations of density is explained, and the 

 experiments by which Sondhauss demonstrated the existence 



