SstT. XXXV. IDENTITY OF THE ELECTRICITIES. 335 



fied and hot air, and also through flame. Dr. Faraday 

 effected chemical decomposition and a deflection of the 

 galvanometer by the transmission of Voltaic electricity 

 through heated air, and observes that these experiments 

 are only cases of the discharge which takes place through 

 air between the charcoal terminations of the poles of a 

 powerful battery when they are gradually separated 

 after contact for the air is then heated. Sir Humphry 

 Davy mentions that, with the original Voltaic apparatus 

 at the Royal Institution, the discharge passed through 

 four inches of air ; that, in the exhausted receiver of an 

 air-pump, the electricity would strike through nearly 

 half an inch of space, and the combined effects of rare- 

 faction and heat upon the included air were such as to 

 enable it to conduct the electricity through a space of six 

 or seven inches. A Leyden jar may be ^instantaneously 

 charged with Voltaic, and also with magneto-electricity 

 another proof of their tension. Such effects cannot be 

 obtained frojn the other kinds, on account of their weak- 

 ness only. 



The heating powers of ordinary and Voltaic electri- 

 city have long been known, but the world is indebted to 

 Dr. Faraday for the wonderful discovery of the heating 

 power of the magnetic fluid : there is no indication of 

 heat either from the animal or thermo electricities. All 

 kinds of electricity have strong magnetic powers, those 

 of the Voltaic fluid are highly exalted, and the existence 

 of the magneto and thermo electricities was discovered 

 by their magnetic influence alone. The needle has 

 been deflected by all in the same manner, and magnets 

 have been made by all according to the same laws. 

 Ordinary electricity was long supposed incapable of de- 

 flecting the needle ; M. Colladon and Dr. Faraday how- 

 ever have proved that, in this respect also, ordinary elec- 

 tricity agrees with Voltaic, but that time must be allowed 

 for its action. It deflected the needle, whether the cur- 

 rent was sent through rarefied ah-, water, or wire. 

 Numerous chemical decompositions have been effected 

 by ordinary and Voltaic electricity, according to the 

 same laws and modes of arrangement. Dr. Davy de- 

 composed water by the ejfictricity of the torpedo, Dr. 

 Faraday accomplished its decompositToii, ancTTJrTRitchie 



