PIERCE. — CRYSTAL RECTIFIERS FOR ELECTRIC CURRENTS. 325 



the writer can judge, equal in sensitiveness with the most sensitive 

 detectors heretofore employed in wireless telegraphy. Also the mo- 

 lybdenite rectifier, giv- 

 ing comparatively large 

 values of direct current 

 for small values of ap- 

 plied alternating volt- 

 age, affords a sensitive 

 method of measuring 

 the small alternating 

 voltages arising in 

 telephony and in experi- 

 ments on sound. Appli- 

 cation of the rectifier 

 to the measurement of 

 sound has been made 

 in a paper entitled "A 

 Simple Method of Meas- 

 uring the Intensity of 

 Sound." 10 



Referring again to 

 Figure 4, attention is 

 called to the dotted 

 curve C. This curve 

 is calculated from the 

 curves A and B by sub- 

 traction of correspond- 

 ing abscissas. The curve 

 C, therefore, represents the excess of voltage required to force the 

 current from the molybdenite to the copper above that required to 

 send an equal current in the opposite direction. The numerical values 

 for curve C are given in Table II. 



The current- voltage values for the molybdenite rectifier differ for 

 different specimens and for different adjustments of the same specimen. 

 The results of another set of experiments, in which larger values of the 

 current and voltage are employed, are given in Table III. These values 

 were obtained with a specimen mounted somewhat differently from the 

 mounting of Figure 3, in that, in order to eliminate any possible un- 

 certainty from the use of the clamp holder K (Figure 3), the tight con- 

 tact terminal was soldered to a copper-plated area on the molybdenite, 



1.4 1.8 



3p 2£ 



VOLTS 



Figure 4. Current-voltage curves of the molyb- 

 denite rectifier. A, current from copper to molyb- 

 denite; B, current from molybdenite to copper; 

 C, excess voltage. 



10 G. W. Pierce : These proceedings, 43, 337 (Feb., 1908). 



