for Currents of Frequencies in Wireless Telegraphy, 93 



On the other hand, with the same ideal approximation i x 

 takes the values: 



a : for L 2 = L 1? 



i^-^E cos cot, (4) 



and 

 B : for L 2 = 0, 



i 1= - C ~ 2 Ecoscot--coCE sin cot. ... (5) 



The latter expression (5) approaches the former one (4) as 



soon as ~— is small, this being the case in the experiments, 

 K 2 



and i x becomes proportional to the resistance of the shunt, 

 the value to be measured. 



This fact at once suggested the insertion of the thermo- 

 galvanometer in the main branch of the oscillatory circuit, 

 instead of in the shunt ; and as R : in the experiments was 

 kept very low, it follows at once that the deflexions of the 

 thermo-galvanometer being proportional approximately to ij 2 , 

 and therefore to the second power of R 2 , furnish a very 

 exact means of comparing the high-frequency resistances 

 of different shunts. Moreover, (4) and (5) prove the 

 approximate independency of i x on the value of the self- 

 inductance L 2 of the shunt, within the limits L 2 = and 

 L 2 = L l5 this fact being confirmed experimentally. The 

 insertion of an extra self-inductance of a coil of six adjacent 

 turns of diameter 15 centimetres in the shunt circuit did not 

 alter the galvanometer deflexion, while, on the other hand, a 

 variation of the length of the path of the current through 

 the tube filled with the electrolyte of 1 millimetre, already 

 gave a considerable variation of deflexion. 



The results of the measurements of the conductivity of sea- 

 water, taken from a sample obtained from Hastings, are as 

 follows. When the conductivity for very slowly alternating 

 currents is called a x and <r x represents the conductivity for a 

 current of a frequency corresponding to a wave-length of x 

 metres, it was found (each a being taken as the mean of 

 several observations) 



o- 34 oo= 1*001 Coo 



c im = 0-999 <r m 



cr im = 1-002 o^ 



0"6oo — 1*003 cr x 



0"275 = 1*005 Coc . 



