surrounding Media on Voltaic Ignition. 



121 



with the poles of another battery, a delicate galvanometer 

 being interposed in the circuit. Not the slightest effect on 

 the galvanometer needle could be detected, and a similar 

 negative effect took place when the tube was filled with atmo- 

 spheric air. 



2nd. Parallel portions of platinum wire were now arranged 

 in close proximity {see fig. 3.), and so that each might be 

 ignited to a full incandescence by separate insulated batteries. 

 When surrounded by atmospheres, both of atmospheric air 

 and of hydrogen, and fully ignited, not the slightest conduc- 

 tion could be detected, across the interval between the wires, 

 with ten cells of the nitric acid battery, and being enabled by 

 the kindness of Mr. Gassiot to repeat this experiment with 

 his battery of five hundred well-insulated cells of the nitric 

 acid combination, air did not conduct when the ignited wires 

 were approximated to the one-fiftieth of an inch; on ap- 

 proaching them nearer they came within striking distance, 

 were instantly fused, and the galvanometer needle, which had 

 up to this time been perfectly stationary, was whirled rapidly 

 round. 



I think I am entitled to conclude from this, that we have 

 no experimental evidence that matter in the gaseous state con- 

 Fig. 3. 



ducts voltaic electricity; probably gases do not conduct 

 Franklinic electricity, as the experiments which would seem 

 prima facie to lead to that conclusion, are explicable as re- 

 sulting from the disruptive discharge. 



In Faraday's experiment two wires were approximated in 

 the flame of a spirit-lamp, and a slight conduction across the 

 interval in the flame was observed. This conduction might 

 have been due to certain unconsumed particles of carbon ex- 

 isting in the flame, or possibly to the flame itself; according 

 to Dr. Andrews, flame, even that of pure hydrogen gas, con- 

 ducts voltaic electricity*. 



I now endeavoured to ascertain whether any specific inductive 

 effect of the hydrogen might have an influence : parallel wires 

 of platinum and parallel coiled copper wires were placed in 

 atmospheres of hydrogen and of atmospheric air, one of which 

 parallel wires conveyed the current, and the other wire was 

 connected with a delicate galvanometer. I could detect no 



* Phil. Mag, vol. ix. p. 176. 



