416 



F. Dellmaun on Atmospheric Electricity. 



We see that the ratio of the minimum in May to the maximum 

 in December is about 1 : 2, aud therefore much smaller than that 

 deduced from many years' observations at Brussels. But even 

 the observations at 2 o'clock, which can be best compared vi^ith 

 those at Brussels, since in Brussels observations are made at 12 

 o'clock, furnish a far smaller ratio, — being equal to 2 : 7 nearly. 

 The morning means diflPer most from the Brussels means, the 

 cause of which is that the atmospheric electricity increases 

 greatly soon after sunrise, when it reaches its principal maximum 

 for the day. For the most part the atmospheric electricity in 

 its variation, on the whole as well as throughout the day, agrees 

 tolerably well with the variation of the barometer. The most 

 remarkable fact is the diminution of atmospheric electricity with 

 a south-west wind ; and this is particularly the case in winter, 

 when the mean with a south-west wind is not much higher than 

 in summer. With respect to this fact, which Quetelet has 

 already proved from the Brussels observations, more accurate 

 infoi-mation must be sought in the second Year's Report of the 

 Royal Meteorological Institution. The principal remaining 

 results are as follows. 



The air is almost always electric, generally positively electric ; 

 for it is only in rain, or rather when rain commences, that it 

 becomes strongly negatively electric. On the approach of a 

 storm, too, the air is negatively electric, even when the storm is 

 still at a distance, so that the clouds of the same are far from 

 floating over the place of observation. In clear weather the air 

 is almost always positively electric ; it is only very rarely, as with 

 a strong north-east wind (twice), that it becomes negatively 



tions, than with those of the Brussels observations ; though, in mentioniug 

 the fact, no doubt is intendeil to be cast upon the trustworthiness of the 

 Brussels observations. 



