OP ARTS AND SCIENCES. 73 



Whenever the excursion of the hammer was greater than 100 X 10~® 

 the sound was very scratchy and harsh. 



TABLE III. 



Electrodes, Carbon, Carbon. — Magnification, 160 diameters. 



Excursion. Character of Sound. 



350 X 10-6 to 300 X 10-6 Loud, noisy, liarsh. 



250 X 10-« to 200 X 10-6 Very scratchy. 



120 X 10-6 to 80 X 10-6 Scratcliy, but less than before. 



150 X 10-6 to 100 X 10-6 Scratchy, but with high overtones. 



At the lowest amplitude given in Table III. the quality of the sound 

 of the pipe was first heard, but a still less amplitude was necessary for 

 its satisfactory reproduction. 



TABLE IV. 

 Electrodes, Carbon, Platinum. — Magnification, 160 diameters. 

 Excnrsion. Character of Sound 



250 X 10-6 Constant sparks and breaks. 



120 X 10-6 Scratchy ; occasional sparks and breaks. 



70 X 10-6 Raspy. 



80 X 10-6 . Quality distinct, but high squealing over- 



tones present. 

 20 X 10-s Quality better ; fewer high overtones. 



Less than 20 X 10-6 Quality better ; some high overtones still 



audible. 



The pipe had to be carried twice as far away from the transmitter 

 as in last measurement, to a distance of eighteen inches, before the 

 quality became really excellent. 



TABLE V. 



Electrodes, Carbon, Platinum. — Magnification, 150 diameters. 



Excursion. Character of Sound. 



120 X 10-6 Very scratchy ; occasional sparks. 



60 X 10-6 Squealing, high overtones. 



40 X 10-6 Fair qu.ality ; high overtones prominent. 



< 20 X 10-6 Good quality ; a little rough. 



400 X 10-6 Constant breaking. 



60 X 10-6 Very raspy. 



40 X 10-6 High overtones strong. 



20 X 10-6 Quality good. 



