NOMOS. 53 



carried over bodily, one electrode being hollowed out 

 as the other is elongated, just as was the case with 

 the silver electrodes in fused chloride of silver. 

 How, then, is the charcoal carried over? Is it by 

 progressive combinations with the intervening mole- 

 cules ? The premises certainly warrant this conclu- 

 sion, and there is no other explanation to be offered. 

 When a voltaic current is discharged from zinc 

 electrodes, across an exhausted receiver, or a receiver 

 full of nitrogen, the discharge is luminous, and the 

 zinc is deposited as a fine black powder of metallic 

 zinc upon the sides of the receiver. The light of this 

 discharge appears to be that of common combustion ; 

 but this it cannot be, for there is no oxygen to enkindle 

 it. The black powder, moreover, burns in the open air 

 when it is touched by a lighted match, and by this 

 means is converted into white oxide of zinc a plain 

 proof that it could not have burnt previously in common 

 combustion. Again, when the current is discharged 

 between iron electrodes under the same circumstances 

 as the last, the results are similar. Metallic iron 

 distils, and may be detected as Prussian blue upon 

 the sides of the receiver by washing them with a so- 

 lution of ferrocyanide of potassium, and therefore 

 the luminosity of the discharge in this case could 

 not have been owing to common combustion. What, 

 then, is the nature of the electric flame in the ex- 

 hausted receiver and in nitrogen ? What is it in the 

 exhausted receiver? Is it the result of chemical 

 changes among the molecules of the metal itself, such 

 as those into which Dr. Graham has initiated us? 

 What is it in nitrogen ? Is it the sign of chemical 



