16 SCIENCE IN SHORT CHAPTERS. 



intensity as it is outwardly dispersed, is enfeebled in the ratio 

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

 the Joudness of the sound is one fourth of that at ten feet, at 

 thirty feet one ninth, at forty feet one sixteenth, 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, excepting, 

 perhaps, by Simeon Stylites when he preached to the multitude 

 from the top of his column. If Mr. Vernon Rigby had stood 

 on the top of one of his native South Staffordshire chimney- 

 shafts, of the same height above the ground as the Upper Press 

 Gallery of the Crystal Palace is above the front of the orches- 

 tra, 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 great difference of effect at 

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

 know something about the acoustics of conceit rooms. 



The uninitiated reader will at once 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 downward, upward, north, south, 

 east, or west, unless some special directive agency is used. 

 The directive agency commonly used is a reflecting or rever- 

 berating surface. 



Thus the voice of the singer travels forward more abundantly 

 than backward, because he uses the roof, and, to some extent, 

 the walls and floor of his mouth, as a sound reflector. The 

 roof of his mouth being made of concave plates of bone with a 

 thin velarium of integument stretched tightly over them, sup- 

 plies 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 out 

 of average raw material, studied the physiology of the vocal 

 organs, and one of their first instructions to their pupils was 

 that they should sing against the roof of the mouth, then 

 throw the head back and open the mouth, so that the sound 

 should reverberate forward, clear of the teeth and lips. For 

 the first year or two the pupil had to sing only " la, la," for 



