PIERCE AND EVANS. 



CAPACITY OF CARBORUNDUM. 



815 



The conclusion is that the droop of the several curves of Figures 10 

 and 1 1 may be reasonably explained as due to incompleteness of charge 

 and discharge. On this assumption it will be seen that the capacity of 

 the crystal, obtained by dividing the coefficients of the equations of 

 Table VIII. by the corresponding values of ^, are functions of the applied 



TABLE VI. 

 Data of Experiment II. Compared with Equation (30). 



e. m. f. and of the direction of charge, while the product of R by C, as 

 given by the exponent, is constant. These quantities are collected in 

 Table IX., and plotted in the curves of Figure 12. 



The curves of Figure 12 show that the capacity, as given by equation 

 (30), is changed by a mere reversal of the direction' of charge. The 

 capacity is the greater when the point electrode is negative, and with 

 this orientation the capacity increases with increase of applied e. m. f. 

 With the opposite direction of application of e. m, f. the capacity is less 

 and decreases with increasing applied e. m. f. 



Whether this result is evidence of a unilateral dielectric constant of 

 the carborundum — which seems improbable — or whether the result is 

 due to an imperfect comprehension of the various factors that may 

 enter into the phenomenon and appear in the final coefficient as capac- 

 ity, we are at present unable to say. 



Among the various factors neglected in the mathematical discussion 

 of the data there is the possibility that heat effects may be important. 

 It looks at first glance as if a thermoelectromotive force at the junction 



