232 SCIENCE IN SHORT CHAPTERS. 



intensitp as it is outwardly dispersed, is enfeebled in the 

 ratio of the squares of distance; thus at twenty feet from 

 the singer the loudness of the sound is one fourth of that 

 at ten feet, at thirty feet one ninth, at forty feet one six- 

 teenth, at fifty feet one twenty-fifth, and so on; that is, 

 supposing the singer or other source of sound is surrounded 

 on all sides by free, open, and still air. 



But this condition is-never fulfilled in practice, except- 

 ing, perhaps, by Simeon Stylites when he preached to the 

 multitude from the top of his column. If Mr. Vernon 

 Eigby had stood on the top of one of his native South Staf- 

 fordshire chimney-shafts, of the same height above the 

 ground as the upper press gallery of the Crystal Palace is 

 above the front of the orchestra, and I had stood on the 

 open ground at the same distance away and below him, his 

 solo of "Comfort ye, my People" would have been utterly 

 inaudible. 



What, then, is the reason of this g-reat difference of effect 

 at equal distances ? If we can answer this question, we 

 shall know something about the acoustics of concert- 

 rooms. 



The uninitiated reader will at one begin by saying that 

 "sound rises." This is almost universally believed, and 

 yet it is a great mistake, as commonly understood. Sound 

 radiates equally in every direction downwards, upwards, 

 north, south, east, or west, unless some special directive 

 agency is used. The directive agency commonly used is a 

 reflecting or reverberating surface. 



Thus the voice of the singer travels forward more abun- 

 dantly than backward, because he uses the roof, and, to 

 some extent, the walls and floor of his mouth, as a sound 

 reflector. The root of his mouth being made of concave 

 plates of bone with a thin velarium of integument stretched 

 tightly over them, supplies a model sound reflector; and I 

 strongly recommend every architect who has to build a 

 concert or lecture-room, or theatre, to study the roof of his 

 own mouth, and imitate it as nearly as he' can in the roof 

 of his building. 



The great Italian singing masters of the old school, who, 

 like the father of Persian!, could manufacture a great voice 



