316* New Eletlrical Experiments 



the fides of the veifel. The quantity of air produced, how-* 

 ever, was fo fin all, that it could not he examined. 



1$, Experiments for examining the quality of the air in tbc 

 hall in which the machine ivas worked. — For this purpofe 

 Sauifure's electrometer was employed, but, infiead of a 

 pointed piece of metal, the flame of a wax taper was em- 

 ployed to receive the electricity, according to Volta's expe- 

 riment. The air in this hall was of moderate drynefs ; and 

 it was obferved that, for the fpace of five minutes, during 

 which the electricity was continued, the whole air was elec- 

 tric, though the hall was 60 feet in length, 30 in breadth, 

 and 40 in height. The balls feparated from each other at 

 the remote!! places half an inch ; the conductor was pofi- 

 tively electrified, and the air of the hall was electrified in the 

 fame manner. 



14. Volta entertained an idea that the ftrength of the 

 conductor would be inereafed if its length were increafed. 

 Experience, however, proved the contrary. Sparks drawn 

 from a conductor 60 feet in length and 4 inches in dia- 

 meter, were five inches fhorter than thofe drawn from a 

 common conductor. The fparks feemed to be a little 

 ttronger, but they followed each other more (lowly. 



15. In repeating the experiments on the communicating heat- 

 to bodies by electricity, Dr. Van Marum conceived the idea 

 of tranfmitting the fparks through femi-conduftors, in order 

 to give them more energy. For this purpofe he placed a 

 wooden rod, one inch in thicknefs and 11 inches in length, 

 between the ball of the conductor and the conducting wire. 

 The confequence was what he expected ; for a rod of red fir, 

 after being electrified three or four minutes, gave fenfiblc 

 figns of heat; and a thermometer, funk into a hole made in 

 it, rofe in three minutes from 61 to 88 degrees, and, in five 

 minutes, to 1 1 % degrees. As the fparks, however, often pe- 

 netrated under the furfiice of the rod, it at length fplit at the 

 end, and continually threw out rays fideways, fo that it imi- 

 tated the effects of lightning!. 



16. Phofphorus electrified in vacuo produced a eas by 

 which the column of mercury in half an hour fell four 



inches ; 



