STUDIES IN ATMOSPHERIC ELECTRICITY. ]7 



Now the température tit those hours wus: 22°.7 at o p.m. ; 21°.9 

 at 4 p.m. ; 18°. 7 at 5 p.m. ; 17°.7 at G p.m. The thermograph 

 preserved in tlie Central Meteorological Observatory shows a sudden 

 decrease of temperature from 4.00 p.m. to 4.30 p.m. The wind was 

 NNW 4. G at 4 p.m. and E 6.7 at 5 p.m. Thus we see that at about 

 4 p.m. a cold current of air suddenly came from the east. The 

 negative potential at first observed was then the effect of the negative 

 electrification of the previously existing warmer air, and the positive 

 potential afterwards observed, of the positive electrification of the 

 comino; colder air on mixins; with the former. 



Again on Dec. 2G, the potential began to get very high from 



1 p.m. and was quite out of the paper at 1.30 p.m. It began to 

 decrease and crossed the zero line at about 2 p.m., and became 

 negative, and then gradually returned, till at 3 p.m. it had recovered 

 its usual course, though much lower than it had kept before. 



The temperature was 5°.0 at noon ; 5°.3 at 1 p.m.; 11°.7 at 



2 p.m. ; 11°.9 at 3 p.m. The thermograph shows a sudden increase 

 of temperature from about 1.45 p.m. to 2.00 p.m. The wind was 

 NNW 2.0 at 1 p.m. ; WNW 3.0 at 2 p.m. ; SW 7.4 at 3 p.m. 

 Thus we see that at about 1.45 p.m. a warm current of air came from 

 SW. The positive indications at first observed were no doubt the 

 consequence of the positive electrification of the colder air previously 

 existing, and the negative indications afterwards observed, of the 

 negative electrification of the newly arrived warmer air on mixing 

 with the former. 



CONCLUSIONS 



A summary of the principal conclusions obtained from the above 

 considerations is added here. 



