74 PROCEEDINGS OF THE AMERICAN ACADEMY 



TABLE VI. 



Electrodes, Carbon, Platinum. — Magnification, 700 diameters. 

 Excursion. Character of Sound. 



200 X 10-6 Rough, but pitch discernible. 



80 X 10-« Rough, pitch distinct. 



30 X 10-^ Smooth, witii high overtones. 

 30 X 10-8 



20 X 10-^ Quality good; some high overtones. 



10 X 10-e Good quality. 



25 X 10-6 Smooth, with high overtones. 



30 X 10-6 to 40 X 10-6 piigh overtones prominent. 



80 X 10-« Harsh and rough. 



TABLE VII. 



Electrodes, Carbon, Platinum. — Magnification, 940 diameters. 

 Excursion. Character of Sound. 



1000 X 10-6 to 800 X 10-6 Scratchy, with breaks. 



100 X 10-6 Rough, with higli overtones. 



80 X 10-6 Wheezy, with high overtones. 



40 X 10-6 ' Smooth, but with high overtones. 

 80 X 10-« 



60 X 10-6 Rough, with high overtones. 



50 X 10-6 Harsh, with high overtones. 



40 X 10-6 Smoother. 



30 X 10-6 Smoother, with high overtones. 



20 X 10-6 to 30 X 10-6 Good quality, high overtones present. 



20 X 10-6 Good quality. 



TABLE VIIL 

 Electrodes, Carbon, Platinum. — Magnification, 940 diameters. 



Excursion. Character of Sound. 



1000 X 10-6 Harsh and screamy. 

 2000 X 10-6 



1000 X 10-6 High overtones heard ; no distinct pitch 



transmitted. 



400 X 10-6 High strident overtones present. 



100 X 10-6 High overtones still present. 



60 X 10-6 Sound wheezy. 



30 X 10-6 Sound smooth. 



20 X 10-6 to 10 X 10-6 Quality good. 



The differences in the effects obtained with a microphone in which 

 both electrodes are of carbon, as compared with one in which one of 

 the electrodes is of platinum, are well known to every one who has 



