PIERCE. — A METHOD OF MEASURING THE INTENSITY OF SOUND. 385 



placement along the scale S. The open end of the pipe was placed at a 

 height of 61 cm., and was therefore on a level with the middle of the 

 reflector. 



O .4 



Z 



10 20 30 40 60 60 70 80 80 100 UO 120 130 



OISTANCE FROM wai_L TO PIPE— CM. 



-SO 

 J6 



10 20 30 40 60 80 70 80 80 100 UO 120 130 



DISTANCE FROM WALL TO PIPE — CM. 



10 20 30 40 60 80 70 80 80 100 UO 120 



OISTANCE FROM WALL TO PIPE — CM. 



Figure 5. — Curve 1, stationary wave in terms of current in secondary. 

 Curves 2 and 3, stationary waves in terms of voltage in secondary. 



The distance from the reflector W to the pipe P could be varied and 

 was read off on the scale S. Readings of the galvanometer were taken 

 with the reflector at various stages, 5 cm. apart, along the scale. The 

 values of the current in the galvanometer circuit are plotted against 



VOL. XLIII. — 25 



