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XXX. On the ElecU'ical Phcenomena exhibited in Vacuo. By 

 Sir Humphry Davy, Bart. P.B.S.* 



X H E production of heat and light by electrical discharges ; 

 the manner in which chemical attractions are produced, de- 

 stroyed, or modified by changes in the electrical states of bodies; 

 and the late impoitant discovery of the connexion of magnetism 

 with electricity, have opened an extensive field of inquiry in 

 physical science, and have rendered investigations concerning 

 the nature of electricity and the laws by which it is governed, 

 and the properties that it communicates to bodies, much more 

 interesting than at any former period of the history of philo- 

 sophy. 



Is electricity a subtile elastic fluid? or are electrical effects 

 merely the exhibition of the attractive powers of the particles 

 of bodies? Are heat and light elements of electricity, or merely 

 the effects of its action ? Is magnetism identical with electricity, 

 or an independent agent, put into motion or activity by electri- 

 city ? — Queries of this kind might be considerably multiplied, 

 and stated in more precise and various forms : the solution of 

 them, it must be allowed, is of the highest importance ; and 

 though some persons have undertaken to answer them in the 

 most positive manner, yet there are, I beheve, few sagacious 

 reasoners, who think that our present data are sufficient to 

 enable us to decide on such very abstruse and difficult parts 

 of corpuscular philosophy. 



It appeared to me an object of considerable moment, and 

 one intimately connected with all these queries, t/ie relatio7is 

 of electricity to space, as nearly void of matter as it can be 

 made on the surface of the earth ; and, in consequence, I un- 

 dertook some experiments on the subject. 



It is well known to the Fellows of this Society who have 

 considered the subject of electricity, that Mr. Walsh believed 

 that the electrical light was not producible in a perfect torricel- 

 lian vacuum ; and that Mr. Morgan drew the same inference 

 from his researches ; and likewise concluded that such a va- 

 cuum prevented the charging of coated glass. — Now it is well 

 known, that in the most perlect vacuum that can be made in 

 the torricellian tube, vapour of mercury, though of extremely 

 small density, exists; I could not help, therefore, entertaining 

 a doubt as to the ))erfect accuracy of these results, and I re- 

 solved not only to examine them experimentally, but likewise, 

 by using a comparatively fixed met;d in fusion lor makinjr the 

 vacuum, to exclude, as far as was possible, the presence ot any 

 volatile niatter. 



* From tlic Transactions of the Philonophical Society for 1822, Part I. 

 Z2 The 



