EXPERIMENTS ON ELECTRICITY. 1ST 



The foregoing experiments were frequently repeated, but When the plate 



as the charge had hitherto been negative, he was defirous of ^^tw, &c. 



knowing, whether a variation of the nature, of the furface and dried, its 



might not alter it. He therefore covered the furface of the electricity be- 

 e> ... came poutive* 



copper plate with a mixture of gum water and minium, and 



alio with gum water and wheat flour, and he found that this 



fubftance when dried upon the furface of the copper, changed 



the nature of the charge communicated to the plate to which it 



was applied. 



Laftly, to render what he called the electricity of the ap- The condenfer 

 proximating plates more confpicuoufly fenfible, he ground a afturds ele&n- 

 brafs plate three inches diameter with emery, till it would 

 adhere to the furface of a piece of black marble. This plate 

 and marble therefore conftituted a condenfer in its original 

 ftate. The marble being moderately warmed, he preffed the 

 brafs plate upon its furface with the point of a brafs wire ; 

 then lifting it up with its infulating handle he applied it to the 

 cap of the electrometer, which caufed the gold leaf to ilrike 

 the fide negatively. 



Hence he thinks it mail appear evident, from the precau- Enumeration of 



iions and experiments he has ftated, and from the known laws re ' u ts * ** A ^ e 



r . doubler cleared 



.of electricity. 1. That the doubler may be deprived of acci- of eleaiicity. 



dental or communicated electricity. 2. That the principal *• Caufe °* 

 r r-. r i • 1 o- r 1 n • • fpontaneous 



cauie or its ipontaneous charge, is the attraction ot electricity charge. 3. and 



by the approximation of its parallel plates. 3. That this charge > ts nature. 4. 



may be pofitive or negative, according as the plates or touch- conc j en fers. c. 



ing wires are compofed of fubflances which have a greater The doubler pre- 



or lefs adhefive affinity with the eledric fluid. 4. That the ferable * 



caufes of fpontaneous electricity are common to the condenfer, 



both in its original and improved ftate, and the doubler, and 



jequal in them all, as far as they are equal in their dimenfions 



and powers. 5. That fince the doubler may be compofed of 



very fmall plates, and yet its power be equal to that of a very 



large condenfer, its fpontaneous electricity will be more eafily 



overcome by a communicated charge than that of a condenfer 



of equal power, and therefore experiments performed with it 



will be lefs liable to equivocal refults. 



This author proceeded to make other experiments, on Other experl- 



the fo termed adhefive elearicity of metals, and other con- mcnts . °l*^ c ~ 



J n . Z live electricity j 



jducting fubftances. He deprived the doubler ot its fponta- with iron and 



pcous charge, and placed the two plates A and B oppofite ftcel > 



each 



