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XVIII, Observations on Mr. Donovan's Reflections on the In- 

 adequacy of thepri?icipul Hypotheses to account for the Phce- 

 nojnena of Electricity . By G. A. Deluc, Esq. F.R.S.&'c. 



To Mr. Tilloch. 



Sir, — 1. JL Hrs paper of Mr, Donovan will, I hope, be very 

 useftil in Settling the doctrine of electricity, against which he 

 finds the objections detailed in his paper, upon its true foun- 

 dation. 



2. The doctrine of positive and negative electricities, first 

 published by Franklin, is true in itself; but by the manner in 

 which he had expressed it it was involved in many difficulties 

 which he had not foreseen. I shall have occasion hereafter to 

 relate the opportunity which I had, long after, to demonstrate 

 to him personally, by an experiment, what kind of influence the 

 air has in the propagation of the electric fluid. 



3. Franklin's theory was first attacked by Dr. Peart, who 

 pointed out some phaenomena of electric viotions absolutely in- 

 consistent with his statement of his own system. I shall not 

 eiiter into that discussion, but point out directly the source of 

 an insurmountable difficidty in that theory, -as it was first ex- 

 pressed by its author, which circumstance (as I shall successively 

 prove) has been the only cause of its rejection by Mr. Donovan. 

 The error was this : Dr. Franklin considered as the standard of 

 plus ?LiAminus, or middle point between them, a certain natural 

 qjiantily of electric matter belonging to all the bodies of the 

 earth : he called negative the bodies from which some part of 

 that qjianlity was abstracted, and positive those to which a new 

 quantity was added. 



4. This error of Franklin has created all the just objections 

 of Mr. Donovan; but from this circumstance I may judge that 

 the latter has not had the opportunity of knowing two works 

 which I have pul)lishcd, one in England in 1787, in two volumes, 

 under the title of Idees sur la Meteorologie : the other was 

 published at Paris in 1804, also in two volumes, under the title 

 of Traite elcmentaire sur le Fli/ide electro-galvanique. In 

 both these works I have applied Volta's system to the motions 

 of a pair of balls, which motions are the most immediate test 

 of electrical theories. 



5. The essential and characteristic difference of Volta's theory, 

 compared to that of Franklin, consists in the standard between 

 plus and minus. Volta has demonstrated that there is no other 

 standard, or middle point between these two opposite clectrio 

 Slates, than the actual electric state of the air, wliich possesses 



Vol. 45. No. 202. Feb. 1815. G electric 



