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charge is as the total charge ; exploding distances, as the quantity or 

 very nearly ; intensities and thermo-electric effect of discharge as 

 square of the quantity or number of measure accumulated. 



The author finds that for every metal-coated jar, whether large or 

 small, of thick or thin glass, exposing from T5 to 6 feet of coating, 

 the residual charge or quantity left undischarged, varies between the 

 limits of -^jth and ^th of the total charge. 



Experiment 2 investigates the effect of thickness of glass. Two 

 jars, exposing 2*5 square feet of coating, were employed, their rela- 

 tive thickness being as 1:2, that is, ^ths and ^%ths of an inch ; 

 100 measures were accumulated and discharged at their respective 

 exploding distances. The following results appeared : exploding 

 distance directly as thickness of glass ; intensity or attractive force in 

 direction of electrometer as square of the thickness ; residuary charge 

 in each case the same, being about ^L-th part of the total charge ; ther- 

 mo-electric effect of discharge very nearly the same ; so that whether 

 discharged from thick glass or thin, under intensities of very different 

 degrees the same quantity of electricity produces the same effect. 

 The intensities in this case were as 4 : 1, yet the thermo-electric effect 

 did not differ more than one or two degrees, one being 1 2, the other 

 13. The author finds, by numerous experiments on a series of jars, 

 that the intensity indication has no influence on the force of discharge, 

 the quantity discharged being the same. In a series of jars of dif- 

 ferent magnitudes, and in which the intensity of a given charge of 

 100 measures varied between the limits of 100 and 1000 degrees, 

 there did not appear a difference of more than a few degrees amongst 

 the whole ; the effects varied between 8 and 1 1 degrees. Some little 

 difference will generally arise in favour of electricity accumulated on a 

 small area of coated glass ; in consequence of the greater facility of dis- 

 charge the accumulation has greater freedom of operation through the 

 external circuit, as is shown by its greater effect on the electrometer. 



A celebrated electrician, the late Mr. Brooke of Norwich, in a con- 

 ference with Cuthbertson about the year 1 800, stated that a Leyden 

 jar coated with strips of metal f ths of an inch wide, leaving intervals 

 of the same width between the strips, was equally efficient as a full 

 coating in the ordinary way. Two equal and similar jars, about 

 1 foot in diameter and 1 9 inches high, were prepared accordingly ; 

 one fully coated to about 4 square feet, the other coated in strips 



