Static and Dynamic Electricity during rain. 255 



equilibrium at 5° A* ; the needle commenced to move at 12^ 35™, 

 and oscillated between 19° B and 1° A ; at 12^ SS-^ its oscilla- 

 tion extended througb an arch comprised between 1° B and 

 3J,° B, then between 30° B and 10°-5 A. At 12^ 36'"-5 the 

 rain ceased, and the needle oscillated round its ordinary position 

 of equilibrium from 0° to 10° A; afterwards from 2°-5 to 9° A; 

 and finally came to rest at 5°"5 A, 



A descending current was thus exhibited, but only during the 

 descent of the rain, and the needle was brought to a state of 

 repose at the moment when the electricity changed its sign in 

 such a remarkable manner. The oscillations recommenced at 

 12^ 48"", contempoi'aneous with the second rain, which was very 

 light and of very short duration ; the first impulsion carried the 

 needle from 8° to 12° A, it then oscillated round its position of 

 equilibrium from 1° to 8° A, then from 3° to 7° A ; the direction 

 of the current had changed, it was now ascending. A new change 

 took place afterwards ; the needle oscillated from 5° B to 4° A, 

 then from 2° B to 4° A up to 1 o'clock, when it was again 

 arrested at 5° A. 



I was particularly astonished to learn that the watch of 

 M. Bouvjf had stopped almost at the same instant as my own, 

 that is at 12'^ 37™, at the moment when the sudden change of 

 sign of the atmospheric electricity took place. Was it accidental, 

 or an effect of the electricity ? This it will be difficult to decide ; 

 I confine myself to the statement of facts. 



Setting out from 1^ 15™, the galvanometer was continually 

 observed, but it did not forsake its position of equilibrium ; I 

 returned to my electrical observatory and found the electrometer 

 always indicating + 75°. The clouds continued to move in dif- 

 ferent directions ; they were obsei'ved to advance towards each 

 other, to stop, to attract each other, and then mingle together. 

 The rain-clouds which came from the S.E. united themselves 

 insensibly with others from the N.W., the electrometer marked 

 -I- 72°. The zenith became overcast, some drops fell, + 73° ; 

 then at V" 24™ the rain turned towards the E. -h72°. The 

 clouds towards the zenith and the S.W. were so thin as to per- 

 mit of the solar disc being seen through them, + 64°. 



At 1"^ 28™ a little rain ; the clouds were directed from the 

 S.W. to the N.E. in the sense indicated by the weathercock. 

 The electrometer indicated +61°; we continued to have glimpses 

 of the sun. At I*' 34™ the sun reai)peared, the zenith became 

 clear, and the electrometer marked zero ; the rain had turned to 

 the east. 



At 1'' 56™ the zenith became again charged ; the electrometer 



* When the head of the needle points towards B, the current is de- 

 scendiug ; when towards A, the current ascends. 



