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LIII. E.^say 07A the Phcenomcva of the Electrophorus \ with 

 (til Attempt to reconcile them ivilh the Principles of the 

 Franklinian Theoiij. By Samuel Woods, Esq. Read 

 lefore tlie Askesian Society in the Session 1803-4. 



An the paper which during the last sessions I submitted 

 to the society*, I endeavoured lo offer a general view of the 

 pha:noniena occasioned by the passage or accumulation of 

 the electric fluid, arranging and comparing them with cer- 

 tain propositions which appeared to me to combine and in- 

 clude the leading principles of what is usually termed the 

 Franklinian theory of negative and positive electricity. In 

 ihis essay an examination into the appearances exhibited 

 by the electrophorus was purposely omitted, both because 

 the experiments recited by different observers were not 

 perfectly consistent with each other, and involved the sub- 

 ject in considerable obscurity, and because the singularity 

 of those appearances, in v/hich all concurred, seemed to 

 merit and demand a separate investigation : the present 

 attempt, therefore, to colloc^ arrange, and explain them, 

 may be deemed a supplement to the former paper. 



The electrophorus is an instrument invented by an Italian 

 philosopher, M. Volta, of Como, and consists of three 

 parts ; of two plates and an electric substance. 



1st, The inferior plate ; which at first was made of glass, 

 but is now usually of metal or wood, covered with tinfoil, 

 of a circular form, and carefully freed from points or edges. 



2d, The electric substance f; which may be constructed 

 of glass, or varnish laid on the inferior plate, or sealing- 

 wax, or sulphur, or mixed substances yielding the negative 

 electriciiy. Resinous electrics are best adapted for this pur- 

 pose, because they are less rapidly affected by the humidity 

 of the air, and retain their electricity much longer than glass. 

 This substance most commonly is made to adhere to the 

 surface of the plate; but it is much more convenient to 

 have an independent cake, capable of entire separation. 



* See Philosophical Maj^azine, vol. xvii. p. 97. ^ 



+ The composition is usually equal parts of resin, shell-lac, aiid sul- 

 phur. M. Cavallo recommends the second sort of sealing-wax : others 

 prefer a coatinc of sealing-wax dissolved in spirits of wine, or resin dis- 

 ujlved in oil of turpentine. The one I use is a cake about half »n inch 

 ;i thx.lcness and twelve in diameier, m.ide principally of shtll-lac.vvith 

 ,1 imiii portion cf Venice turpentine to assist its fusion, which is elVected 

 in an e,irthcn vessel over a slow fi-.eor sand heat, and then poured into 

 an irrn h'K>p resting upon a perfectly flat surface. This lias" the advaii- 

 T4'^e of hu-^v very inui^h. and net easily broKn. 



Vol. £1. No. 84. May 1805. T ■^<i, An- 



