THE BANISHMENT OF NIGHT 



mond and points of charcoal and plumbago seemed to 

 evaporate in it, even when the connection was made in 

 the receiver of an air-pump ; but there was no evidence 

 of their having previously undergone fusion. When 

 the communication between the points positively and 

 negatively electrified was made in the air rarefied in the 

 receiver of the air-pump, the distance at which the dis- 

 charge took place increased as the exhaustion was made ; 

 and when the atmosphere in the vessel supported only 

 one-fourth of an inch of mercury in the barometrical 

 gauge, the sparks passed through a space of nearly 

 half an inch ; and, by withdrawing the points from each 

 other, the discharge was made through six or seven 

 inches, producing a most brilliant coruscation of purple 

 light; the charcoal became intensely ignited, and 

 some platina wire attached to it fused with brilliant 

 scintillations and fell in large globules upon the plate 

 of the pump. All the phenomena of chemical decom- 

 position were produced with intense rapidity by this 

 combination." 



It will be seen from this that as far as the actual 

 lighting-part of Davy's apparatus was concerned, it was 

 completely successful. But the source of the current 

 the most essential part of the apparatus was such 

 that even the wealthy could hardly afford to indulge in 

 it as a luxury. The initial cost of two thousand cells was 

 only a small item of expense compared with the cost of 

 maintaining them in working order, and paying skilled 

 operators to care for them. So that for the moment no 

 practical results came from this demonstration, con- 

 clusive though it was, and the introduction of a com- 



[221] 



