96 



Dr. Balth.van der Pol on the Production of 



abscissas are again as in fig. 3, and the resonance wave-length 

 is not far from that in fig. 3. 



The dissymmetry is here well marked, and strongly suggests 

 the presence of two vibrations of slightly different period.. 



Fig. 3. 



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As the mutually coupled grid and plate circuits 

 be considered to be tuned, the generation by the 

 lator of currents of two frequencies at the same 

 is not altogether surprising. In no case, however, 

 two separate maxima observed. 



If the energy dissipated in the galvanometer is neglected, 

 the symmetrical curve of fig. 3 enables us to find the natural 

 logarithmic decrement for the fundamental vibration of a 



ir of Lecher wires. From the breadth of the curve 



pan 



be 



halfway up its maximum the decrement is found to ^ 

 £ = 0*0046, showing on the one hand the considerably in- 

 creased resistance due to the skin effect. On the other hand. 



