ATMOSPHERIC ELECTRICITY IN HIGH LATITUDES. 



75 



High values of the ionization accompany low values of the potential gradient and 

 vice versa. 



Here we find that the ratio between positive and negative ionization (r) does 

 increase with the potential gradient over the range from 50 to 300 volts/metre. That 

 there is not the same agreement higher is to be expected from the fact that for 

 values of the potential gradient over 300 volts/metre the ionization is so small as to 

 be only just within the power of the instrument to measure, and so one cannot expect 

 the ratio of the observations to be given with any degree of accuracy ; also the 

 number of observations with the potential gradient over 300 volts/metre is so small 

 that better results could hardly be expected. 



We may, then, take it that the ionization and dissipation have a great determining 

 influence on the potential gradient, and that high values of the potential gradient 

 are, on the whole, accompanied by high values of the ratio r and q. 



Ionization and Dissipation. It has already been stated that the values of the 

 dissipation, as given by ELSTER and GEITEL'S instrument, depend mainly on the two 

 factors ionization and wind strength. It would be of considerable interest to find 

 how the dissipation varies with either of these factors, the other remaining constant. 



When the greater part of my observations of the dissipation were made. EBERT'S 

 instrument was also in use, and gave the true value of the ionization at the time 

 when each observation of the dissipation was taken. In order to find how the 

 dissipation varies with variations of the ionization, the wind strength being constant, 

 I separated out all the results of the dissipation obtained with a given wind strength, 

 then divided these again according to the values of the ionization observed at the 

 same time. The results are given in Table IX., and have been plotted in fig. 4. 



IO N IZ ATI. ON 



Fig. 4. 



L 2 



