Dcferiptlon of an Impro-jed EleBromeier. 26^ 



fe6l;, though no lefs important in eleftric experiments, is a 

 difcharging cleftrometer ; for, as it is believed that the laws 

 of eleftricity can be defined with mathematical certainty *, 

 it muft be of importance to be able to employ, with the fame 

 certainty, the eleftric power which has been excited ; and 

 every infirument tending to promote this objeft, though ftill 

 imperfeft, muft be of fome utility, and be not unacceptable 

 to thofe fond of eleiftrical experiments. All the difcharging 

 eleftrometers hitherto known, perform their effect either by 

 fpontaneoufly difcharging, as that of Lane, or as Henley's 

 general difcharger, &c. and in this cafe are affe6led by the 

 greater or lefs conducing property of the air, which mufl 

 necefTarily be changed on each change of the atmofphere, 

 and therefore mufl render the inflrunlent very imperfed and 

 incorreft ; or the effect is produced by introducing a con- 

 ducing body between two cleAric atmofpheres, and by thefe 

 means uniting them. But as this muft depend on the greater 

 or lefs dexterity of the pcrfon who performs the exi>enment 

 to determine the proper moment for difcharging, and as an- 

 other eledlrometer is at the fame time necefTary, this method 

 of difcharging is as uncertain as the firft. 



I have endeavoured, therefore, to conftruft an inftrumcnt 

 to fupply this d-eficiency ; and I hope it will not be found 

 unworthy of attention. It is an ekftrometer w^lich, though 



imded on the fame principles as that of Brooks, that is, 

 on comparing the efletSL of the repulfivc power of eleftricity 

 between two bodies of a given lize with the known weight 

 requifite to produce that effect, has, in my opinion, fome 

 improvements which arc wanting in the other; for the fiate 

 -m' the barometiir has no influence upon this electrometer, as 

 ■it has on that of Brooks; nor docs friftion, which is far 

 from being miimj)ortant, here take place. But as this iu- 



" Ste'l.orcl Scaiiho{)c'ii Pr/iui/'ks of EleiJi-.city, 3d, 4tli, ami 5tli p:irts ; 

 and Coolomb'k dtfcriptioii of an inllrument by wbtcli it is proved that the 

 effcd of the elcdric matter it in the invcrfc ratio of the Uiuixc of the dif- 

 Mni.c. 



fii'ument 



