168 



by him in the explication of some of the phenomena of atmospheric 

 magnetism, and especially of the annual and daily variation. 



A paper was also read, entitled, " On the Electro-chemical Polarity 

 of Gases." By W. R. Grove, Esq., M.A., F.R.S., &c. Received 

 January 7, 1852. 



The author refers to the experiments of Faraday on dielectric 

 induction, to those of Gassiot on the increase of electrical effects of 

 tension, according as the chemical intensities of a voltaic battery 

 are increased, and to other results, which, though supporting the 

 view of a physico-polar state of gaseous substances intervening be- 

 tween oppositely electrified surfaces, have not hitherto shown any 

 change in the arrangement of the gaseous particles dependent upon 

 their chemical characteristics. 



The electric or voltaic disruptive discharge has hitherto presented 

 only one phenomenon which offers any analogy to electrolysis, viz. 

 that observed by Mr. Gassiot and others, of the positive terminal 

 being more intensely heated than the negative, when the voltaic 

 discharge passes between metals. With the voltaic arc the effects 

 of heat and the destruction of the terminals so interfere with any 

 effects properly due to the transmission of the electric current, that 

 it is next to impossible to eliminate the latter ; on the other hand, 

 with the electric spark from an ordinary machine, the quantity of 

 matter acted on is too minute to give satisfactory evidence of the 

 changes taking place. My. Grove sought an intermediate degree 

 of electrical action, and by the aid of an apparatus of Ruhmkorf for 

 producing a powerful secondary current, the results detailed in this 

 paper were mainly obtained, 



A polished silver plate is laid on the pump plate of a good air- 

 pump, and a metallic point is attached to the rod passing through a 

 collar of leathers at the top of the receiver, the point being adjusted 

 at from one-eighth to one-fourth of an inch distance from the plate. 

 Caustic potash is kept suspended in the receiver, and a mixture of 

 oxygen and hydrogen, or atmospheric air and hydi'ogen, allowed to 

 enter it, and then attenuated until the barometer stands at half an 

 inch; the discharges from the secondary coil ai'e now made to pass 

 between the point and the plate, when if the latter be positive it is 

 oxidated, if negative the spot of oxide is reduced. 



If there be excess of oxygen and little or no hydrogen, oxidation 

 takes place, whether the plate be positive or negative, though in 

 different degrees; and if the gas be wholly or mainly hydrogen, 

 reduction takes place whether the plate be positive or negative. 



At certain intermediate states of mixture rings or zones of alter- 

 nate oxidation and reduction are shown, quite distinguishable from 

 the ordinary succession of colours of thin plates, and showing 

 alternations or periods of interference of electrical action. 



The author then gives the results of experiments with several 

 other metals, of which bismuth was the only one he found to produce 

 effects anything like equal to the silver, though other metals showed 

 them in some degree. 



He also varied the gas or gases employed, and details the results 



