392 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



turned toward the spot marked " 8 " in the elevation drawing of 

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

 This position is also less favorable for hearing this particular tone 

 than the position 1 in the rear of the room. 



30 40 60 60 70 80 



DISTANCE FROM WALL — CM 



30 40 50 60 70 80 



DISTANCE FROM WftLL — CM 



Figure 8. — Stationary waves in large lecture room. 



These experiments 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 

 electric disturbances, when they happen to be in syntony with the 

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



