1255 



teristic D. The particular shape of the curve, especially in the first 

 quadrant can hardly be explained in an other way than by a counter 

 E. M. F. with a maxiinnin of about 12.5 Volt. 



Zincite-bornite. The characteristic (r of a zincite-bornite contact 

 corresponds exactly to curve F\. Exactly the same characteristics 

 belong to the combinations zincite-copperpy rites and zincite-copper- 

 glance. The straight parts cut the axis at — 0,4 and -f- 5 Volts. If 

 further a succession of current impulses is sent through, the straight 

 parts of the characteristics undergo parallel displacements. The same 

 shifting is found in (lie characteristics obtained by bringing every 

 one of the components into contact with a platinum point. 



Zincite-platinum. If a succession of current impulses was passed 

 through, the curve CI gradually changed into the straight line IV. 

 The slope of the straight part of curve I consequently gives the 

 real resistance and further proves, in the way shown above, the 

 existence of a counter E.M.F. of 0,4 Volt. Hence it follows that in 

 the other direction a counter E.M.F. must be found as well. Indeed, 

 with some characteristics a straight part did occur in the first 

 quadrant, cutting the axis at about -\- 3 Volts. The following cha- 

 racteristic e.q. was obtained. 



From zincite to platinum 



0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25 2.5 Volt 

 13 4 5 6.5 7 8 8.5 9 9.5 X 0.0001 Ampere 



2.75 3.0 3.25 3.5 3.75 4.0 4.25 4.5 4.75 Volt 

 10 11 14 20 31 42 52 63 74X00001 Ampere. 



From platinum to zincite 



0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0 Volt 

 1.5 9 16.5 24 33 45 56 67X0.0001 Ampere 



2.25 2.5 2.75 3.0 3.25 3.5 3.75 4.0 Volt 

 77 86 98 108 118 129 140 150 X 0.0001 Ampere. 



Bornite-platinum. This combination shows the greatest resistance 

 when the current passes from metal to crystal, see B I. A very 

 slight impulse already causes the straight line B II to appear. The 

 same curve is obtained by the combination copperglance-platinum 

 and chalcopyrites-platinum. The straight jtart points to a counter 

 E.M.F. of 0,4 Volt. It is remarkable that after reversal of the applied 

 E.M.F., the current usually remains steady for about three seconds 

 and then falls in a discontinuous way. The same phenomenon also 

 occurs in other crystal contacts, but was most frequently observed 

 with the electrolytic defector. 



If we compare curve B\ and C I, it is clear why the zincile- 



