tfXFLRIMENTS ON ELECTRICITY. J$5 



fcientific world, than if the book had appeared in the ufual 



mode of publication. At all events, as the work is now 



fcarce, and the fubject of fbme interefl fo far as it may be 



thought connected with the theory of galvanifm, 1 think it will 



not be unacceptable to my readers to relate what he did at 



that early period. The fame reafons will in part apply in 



favour of a concifc account of the experiments of Mr. Cavallo. 



Soon after the publication of Bennet's doublcr in the Philo- Uncertainty *f 



fophical Tranfa&ions for 1787, he found that the inflrument the dearical 

 • j k_cn • • -i « •• ii doubler j from 



produced electricity without previous communication, and that fpontaneous 



it always retained that property, whatever care might be electricity, 

 taken to deprive it of any adhering charge. When he was 

 afterwards engaged in a courfe of experiments facilitated by 

 the mechanifm I applied to the doubler in 1788, he found 

 that a very great portion of this adhering electricity might be removed by 

 removed, by turning the handle of the doubler a confiderable wo * ing . *j 

 number of times, while all the plates were connected with lated. 

 the earth, and that by virtue of this provifion the inflrument 

 might be trufted to indicate the nature of communicated elec- 

 tricity, to a degree of accuracy far exceeding that which could 

 be afforded by any Ampler inflrument. 



By reafoning upon this phenomenon, he was induced to Capacity of bo- 

 conjecture, that this fpontaneous electricity was not owing to d ! es J° r ele & r »- 

 accidental friction, but to what he called the increafed increafe by in- 

 capacity of approximating parallel plates, which might at- proximation, 

 tract and retain a charge, though neither of them were infu- 

 Jated. The experiments he made in fupport or proof of this 

 bypothefis were the following : 



He repeatedly tried the effect of depriving the doubler of Experiments, 

 r ,.V . ., \ . it/* i . , : r , The doubler 



fpontaneous electricity, by turning the revolving plate forty fooner exhi y tc4 



times, with brafs wires hooked to all the plates, and he electricity when 

 found that if he took of the wires while the revolving plate ^^SjJJ 

 flood at a diflance from the two flationary plates, it was more oppofite, than 

 completely deprived of electricity, than if the wires were when at adlf ~ 

 taken off when the revolving plate flood parallel to the plate other. 

 A. That is to fay, it required 21 revolutions to exhibit fpon- 

 taneous electricity after the provifion in the firil cafe, and 16 

 revolutions in the fecond cafe. Whence it feemed to him, 

 that the two plates {landing parallel to each other, had by an 

 increafe of capacity acquired a certain finall charge, which 



foonor 



