96 HISTORY OF GALVANISM, 



charcoal, and plumbago, in small portions, disap- 

 peared, and seemed completely evaporated. A 

 singularly beautiful effect was produced by placing 

 pieces of charcoal at the two ends of the wires in 

 the interrupted circuit ; when they were brought 

 within the thirtieth or fortieth part of an inch of 

 each other, a bright spark was produced, above 

 half the volume of the charcoal, which was rather 

 more than an inch long, became ignited to 

 whiteness ; and by withdrawing the points from 

 each other, a constant discharge took place through 

 the heated air, in a space equal to at least four 



PLATE ii. inches, producing a most brilliant arch of light ; 

 this light constituted the sphere of activity of the 

 instrument. When the communication between 

 the two wires was made in air so far rarefied as to 

 support only one quarter of an inch of mercury in 

 the barometric gauge of the air-pump, the spark 

 passed through a space of nearly half an inch ; and 

 by withdrawing the points from each other, the 



t electric fluid was discharged through six or seven 



inches, producing a most beautiful coruscation of 

 purple light, while the charcoal itself became in- 

 tensely ignited, and some platina wire attached to 

 it fused with brilliant scintillations, and fell down 

 in large globules. All the effects of chemical de- 

 composition were rapidly and powerfully produced ; 

 various substances submitted to the action of the 

 apparatus were instantly resolved into their ele- 

 mentary gases ; and so intense was the action, that 



