542 M. W. HankePs Account of some Experiments 



will be increased. Traces of an effect of this kind are perceptible 

 in M. Regnault's experiments on the vapour of mercury, in 

 which air was present. 



(38.) I have already referred to the property ascribed by Pro- 

 fessor Faraday to various substances, of attracting, and retaining 

 at their surfaces, layers of gas and vapour in a high state of 

 condensation. Supposing a solid body to acquire, in this man- 

 ner, a mixed atmosphere, consisting partly of its own vapour and 

 partly of foreign substances, the total elasticity of that atmo- 

 sphere at any point will be equal, or nearly equal, to the sum 

 of the elasticities which each ingredient would have had sepa- 

 rately ; and thus solid metals, glass, charcoal, earthy matters, 

 and other substances, may acquire a great power of resisting co- 

 hesion, although producing no perceptible vapours of their own. 

 at ordinary temperatures. 



LXXVII. An Account of some Experiments upon the Electricity 

 of Flame f and the Electric Currents thereby originated. By W. 

 Hankel*. 



IT is known that by the combustion of bodies free electricity 

 is generated ; all investigations on the electric deportment 

 of flame have hitherto been limited exclusively to the examina- 

 tion of the free electricity which the flame contains. A deeper 

 consideration of the entire electric deportment in such cases con- 

 ducted me to the idea, that the electric opposition which different 

 portions of the flame exhibit, not unlike the relation which sub- 

 sists between a copper and a zinc plate, ought, like the latter, to 

 be capable of developing an electric current. This proves to be 

 the case. I have succeeded in establishing, in a manner which 

 excludes all doubt, that a flame when properly closed in a con- 

 ducting circuit is the origin of an electric current. 



During the experiments three lamps were made use of. The 

 parts of the lamps No. 1 and No. 2, which immediately sur- 

 rounded the flame, were of the same dimensions ; in other re- 

 spects, however, the lamps were very different. The diameter of 

 the outer brass cylinder which encompassed the wick was 32*5 

 millims., and the diameter of the inner cylinder was 22*7 mil- 

 lims. Between these two cylinders No. 1 carried a new double 

 wick, while No. 2 held a single wick which had been for some 

 time in use. The chimney of No. 1 was of sheet-brass, that of 

 No. 2 was of sheet-iron ; both chimneys were 52 millims. high, 

 and reached about 10 or 11 millims. below the rims of the cylin- 

 ders from between which the wick protruded. The lamp No. 2 



* Abridged from Poggendorif' s Annalen, vol. Ixxxi. p. 213, and com- 

 municated by Dr. J. Tyndall. 



