388 Intelligence and Miscellaneous Articles. 



brass sphere 5 inches in diameter. A second thread, similar and 

 parallel to the first, supports a pith ball pendulum, which, when not 

 electrified, is in contact with the brass sphere. 



I usually electrify the sphere with the conducting disk of an 

 electrophorus. The extent of the room and the purity of the air 

 enable me to fill the space about the electrified bodies with a con- 

 siderable quantity of the gas or vapour which I am investigating, 

 without these fluids settling for a time on the long thread. In 

 this way, apart from the small conductivity of the wires, and the 

 losses due to dust in the air, any diminution of the electrical 

 tension observed must have been due to the conductivity of the 

 fluids experimented on. 



I always electrified the sphere almost to the same tension ; I 

 then observed the time in which the deflection fell a cert'ain 

 number of degrees, first in air and then by surrounding the sphere 

 and the pendulum by a dense atmosphere of the gas to be 

 studied. 



I worked thus with air saturated with aqueous vapour at various 

 temperatures from 16° to 100° ; hydrogen and carbonic acid not 

 dried, but as they emerge from the bath in which they are pro- 

 duced; air heated by charcoal or by the flame of a candle, the 

 smoke of an extinguished caudle, the fumes of burnt sugar, incense, 

 &c. None of these substances showed any trace of conductivity. 



In one set of experiments, instead of cocoon-threads I used 

 ordinary sewing-thread stretched horizontally, and with a double 

 pendulum in the centre provided with pith balls. The results did not 

 change, but when I worked with aqueous vapour at high tempe- 

 ratures, the divergence diminished rapidly by a certain quantity 

 and then became again almost constant. 



This effect is due to the vapour which is deposited on the larger 

 and less insulating wire, and to the fact that the small quantity of 

 electricity of the balls becomes divided between the thread and the 

 balls themselves. — Comptes Bendus, Sept. 13. 



AN ELECTRICAL EXPERIMENT. BY M. BUSCH. 



The author calls attention to the curious figures formed when 

 electricity diffuses on a plate previously dusted with lycopodium 

 powder. 



The two balls of a Henley's electrometer are brought in contact with 

 two sides of a dusted glass plate, and a large Leyden jar is dis- 

 charged through the bails. The figure resulting from the discharge 

 has the appearance of a lightning discharge as seen in the photo- 

 graphs of lightning. — BeiU'dtter der PhysiJc, vol. x. p. 302. 



