1859.] Mr. Grave^ on the Electrical Discharge. 5 



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1859. 



WEEKLY EVENING MEETING, 



Friday, January 28. 



Sir Henry Holland, Bart. M.D. F.R.S. in the Chair. 



W. R. Grove, Esq. Q.C. F.R.S. V.P.R.I. 



On the Electrical Discharge, and its Stratified Appearance in 

 Rarefied Media. 



Few subjects of physical investigation possess greater interest than the 

 electrical discharge ; its brilliant effects and mysterious characteristics 

 offer powerful stimuli to curiosity and enquiry. The speaker proposed 

 first shortly to state the extent of knowledge we possess respecting it ; 

 then to pass to certain peculiar phenomena first discovered by him in 

 1852, and subsequently experimented on by others, and most elabor- 

 ately by Mr. Gassiot ; and then to offer an opinion as to their cause 

 or rationale. 



The best mode of examining and attempting to explain the electrical 

 discharge is to compare it with its nearest analogue flame, to which one 

 form of the discharge, viz. the Voltaic arc, has much seeming resem- 

 blance. The flame of a common candle results, as is well known, from 

 the chemical combination of carbon and hydrogen with the oxygen of 

 the air ; and the combustion is most brilliant where the heated gases 

 and particles are in proximity to the oxygen. It forms a hollow cone, 

 as the oxygen of the air, being consumed or combined into water and 

 carbonic acid at the exterior portion, cannot reach the interior : the 

 course of the currents of heated air, and the particular form of this 

 hollow cone of flame, are beautifully shown by the refraction it pro- 

 duces on a more brilliant light, such as that of the electric lamp ; the 



