

PROCEEDINGS OF Till: IMERICAN ACADEMY. 



turned toward the spot marked ".".'" in the elevation drawing of 

 Figure 7. Here again a burly definite stationary system was found. 

 This position is also less favorable for hearing this particular tone 

 than the position I in the rear of the room. 



10 20 30 «0 SO 00 70 SO 80 100 110 120 



DISTANCE FROM WALL — CM 



20 30 40 60 60 70 SO 90 100 UO 120 



DISTANCE FROM WALL — CM 



Figure 8. — Stationary waves in large lecture room. 



The xperiments were made in the large lecture room which is 



immediately over the machine shop of the laboratory, and were 

 apparently not in any way affected by the very considerable vibration 

 and noise of several motors and lathes in almost continual operation. 

 The rectifier is, however, extremely sensitive to electric waves; and 

 elei-trie disturbances, when they happen to be in syntony with the 

 rectifier circuit may prove troublesome. In the course of the present 



