294 TRANS. OF THE ACAD. OF SCIENCE. 



morning. But even the present defective observations seem 

 to prove the causal connection of the daily two maxima and 

 two minima of electricity with the equilibrium or divergence 

 in temperature and relative humidity. 



Is there, besides the daily and monthly, also an annual pe- 

 riodicity of atmospheric electricity? To determine this ques- 

 tion, observations must be continued for a long series of years, 

 and not in one single locality, but in many different parts of 

 our globe. It may also be needed, for that purpose, to meas- 

 ure the negative atmospheric electricity developed through- 

 out the year ; to accomplish which is a far more difficult task, 

 on account of the sudden appearance and disappearance and 

 the great qualitative fluctuations of negative electricity. No 

 instrument but a self-registering one could acccomplish that; 

 but since, to my knowledge, no practical instrument of the 

 kind has been invented for the observation of the more regu- 

 lar positive electricity, the invention of one for negative elec- 

 tricity is still more doubtful. 



The yearly mean of positive atmospheric electricity during 

 the four years was in 



1861. 1862. 1863. 1864. 



8.4 .... 8.4 .... 9.2 .... 6.8 



The number of thunderstorms was in 



1861. 1862. 1863. 1864. 

 32 .... 50 .... 40 .... 26 



We see, therefore, that the first two years were entirely equal 

 in quantity of positive atmospheric electricity, the third some- 

 what higher, and the fourth considerably lower. What is the 

 cause of this diminished electricity in 1864? The number of 

 thunderstorms in 1864 was less than in the three previous 

 years. This seems to indicate also a diminution of negative 

 electricity during the year. The number of observations by 

 which no electricity whatever was found has been on the in- 

 crease every year. In 1861 it amounted only to 59, in 1862 

 to 225, in 1863 to 461, and in 1864 to 709. To some small 

 extent this may be owing to my mode of observation. Before 

 I was well acquainted with the delicate motions and notions 

 of the instrument, I may perhaps have sometimes noted one 

 or two degrees of electricity which in later observations I 

 rejected; but this trifling discrepancy could not account for 

 the wide difference in zero observations between the first and 

 last year. It seems to me more likely that there was in 1864 

 a considerable falling off in electricity, both positive and neg- 

 ative, manifesting itself by a less quantity of positive electri- 

 city, by a less number of thunderstorms, and by a greater 

 number of zero observations. 



What other meteorological phenomena may stand in causal 

 connection with this diminished electricity ? There was no 



