3:6 ObjeBiom to [Book IV. 



Ic is evident, that it is only in paffmg from one body 

 to anpther, that the effects of the electrical fluid are 

 apparent. When all the adjacent bodies therefore are 

 equally charged with electricity, no effects whatever 

 will appear. The equilibrium mud, according to the 

 principles of Dr. Franklin, be deftroyed, that is, the 

 fluid muft be made rarer in fome one part, before any 

 of the phenomena will be exhibited. In that cafe the 

 denfe fluid rufhing in to fupply the deficiency in that 

 part where it is rarer, produces the flafh of light, the 

 crackling noife, and the other effects of electricity. 



The different effects on rough and fmooth bodies, 

 when excited, have been previoufly remarked. The 

 Franklinean theory is, if a rough and fmooth body are 

 rubbed together, the fmooth body will generally be 

 electrified plus, and that with a rough uneven furface, 

 minus. Thus, in the ordinary operation of the com- 

 mon machine, the cylinder is pofitively electrified, or 

 plus, and the rubber negative, or minus. The redun- 

 dance of the pofitive electricity is fent from the cylin- 

 der to the prime conductor, and may be communicated 

 from it to any conducting body. If, however, the 

 prime conductor is made to communicate with the 

 earth, which- has a great attraction for the electrical 

 matter (and which, being one great mafs of conduct- 

 ing fubftances, will not permit the accumulation of the 

 fluid in a particular part) and if at the fame time the 

 rubber is in an infulated ftate, fupported for inftancc 

 by glafs or any electric, thefe effects will be reverfcd, 

 for the prime conductor will then be negatively elec- 

 trified, and the rubber will be plus or poficive. 



This theory is, it muft be confeffed, not without its 



difficulties, and jt is much to be feared, that we have 



as yet no complete theory of electricity. The fact moil 



difficult to be explained on the Franklinean fyflem is, 



8 that 



