274 PHILOSOPHICAL TRANSACTIONS. [ANNO 1782. 



sible electrometer of Mr. Cavallo's construction, it did not affect it. In this 

 case, when the metal plate, thus weakly electrified, was made to touch the 

 other small plate properly situated, and that was afterwards brought near an 

 electrometer, the electricity was then generally stronger than what would have 

 been sufficient to ascertain its quality. Now, if by the help of both condensers 

 the intensity of the electricit)' has been augmented J 000 times, which is by no 

 means an exaggeration, how weak must then be the electricity of the body 

 examined ? how small must that electricity be which is produced by rubbing a 

 piece of metal with one's hand, since when this electricity is condensed by both 

 condensers, and then is communicated to an electrometer, it can hardly affect 

 that instrument ? Yet it is sufficient to afford conviction, that the metal can be 

 electrified by the friction of a person's hand. Some years ago, viz. before the 

 discovery of our condenser, and of Mr. Cavallo's sensible electrometer, we were 

 very far from being able to discover such weak excitations ; whereas at present 

 we can observe a quantity of electricity incomparably smaller than the smallest 

 observable at those times. 



appendix. — I mentioned, that after various attempts I at last succeeded in 

 obtaining undoubted signs of electricity from the simple evaporation of water, 

 and from various chemical effervescences; but as this is a fact not less interesting 

 than new, it seems proper to subjoin in this place a faithful account of the expe- 

 riments made for that purpose. The first set of experiments were made at Paris, 

 in company with Mr. Lavoisier and Mr. De la Place, two intelligent philosophers 

 and members of the Royal Academy of Sciences. After I had shown them my 

 experiments with my condenser, they, as well as myself, began to entertain hopes 

 of succeeding in the experiments on the evaporation, &c. Accordingly Mr. 

 Lavoisier ordered a larger condenser with a marble plane to be made. The first 

 experiment I attempted with this instrument, in company with Mr. De la Place, 

 proved unsuccessful ; but the weather at that time was bad, the room was narrow 

 and full of vapours, and the apparatus was not quite in proper order. Mr. De 

 la Place and Mr. Lavoisier repeated those experiments in the country, and then 

 they were attended with success, which incited us to repeat and diversify the ex- 

 periments, by which means the discovery was completed ; having obtained une- 

 quivocal signs of electricity from the evaporation of water, from the simple com- 

 bustion of coals, and from the effervescence of iron filings in diluted vitriolic 

 acid. This observation was made the 13th of April of the present year 1782, 

 and the experiments were performed in the following manner. In an open gar- 

 den a long metal plate was insulated, which, by means of a large iron wire, was 

 made to communicate with the metal plate of the condenser laid on the piece of 

 marble, which was kept continually warm by some lighted coals set underneath. 

 This done, some chafing dishes, containing burning charcoal, were placed on 



