1250 



This does not become obvious unless one draws the cliaracleristics 

 of rectification representing the relation between the E.M.F. applied 

 to the contact and the current passing through. 



^ 4. The observations for the characteristics. 



As the iiitensitv of the current passing through is not only a 

 function of the applied E.M.F. but also depends upon the time the 

 current has already passed, the characteristic curve will be found 

 to alter with time. One must therefore deternune the curve by means 

 of a sufficient number of observations, all of them taken within as 

 short a time as possible. As mirror-galvanometers are generally too 

 "slow", "Prazisionsinstrumente" of Sikmens and Halskk were used, 



10-* AMR 



100 / n 



60 VOLTS 



Fig. 1. 



which indicate the exact intensity of the current instantaneously 

 and, as they are pointing instruments, are easy to read. 



The connections are shown in Fig. 1. The crystal K usually 

 floated on mercury which formed at the same time the one electrode. 



