358 



Tvfts — Transmission of Sound 



experiments for 'determining the variations in the resistances 

 offered by these same materials to the to and fro motion of the 

 air particles of a sound wave will be given. 



Fig. 1 



Flow of air through granular materials. 



The apparatus employed in studying the flow of air through 

 the three sizes of shot is shown schematically in fig. 1. It 

 consists essentially of a tube, T, about 75 centimeters long 

 and 2*5 centimeters inside diameter, provided at p with a 

 partition of wire gauze the meshes of which are fine enough 

 to prevent the smallest shot from falling through. Near 

 either end of this tube are connected side tubes, t and t', to 

 which are attached respectively the two arms of a water 

 manometer, M. The upper end of the tube, T, is connected 

 though a cock, S, with a source of compressed air, and the 

 lower end of the tube is connected to a gas-meter, G. In 



