ELECTRICITY AND MAGNETISM 



tion between the points positively and negatively elec- 

 trified was made in the air rarefied in the receiver of the 

 air-pump, the distance at which the discharge 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 decomposition were 

 produced with intense rapidity by this combina- 

 tion." 1 



But this experiment demonstrated another thing 

 besides the possibility of producing electric light and 

 chemical decomposition, this being the heating power 

 capable of being produced by the electric current. 

 Thus Davy's experiment of fusing substances laid the 

 foundation of the modern electric furnaces, which are 

 of paramount importance in several great commercial 

 industries. 



While some of the results obtained with Davy's 

 batteries were practically as satisfactory as could be 

 obtained With modern cell batteries, the batteries them- 

 selves were anything but satisfactory. They were 

 expensive, required constant care and attention, and, 

 what was more important from an experimental stand- 

 point at least, were not constant in their action except 

 for a very limited period of time, the current soon 



235 



