534 Bicplanatkn of the EffeB of hreathiug ittto EUBrk Jays. 



difcharge with the firft corufcation, the one being fo quickly followed by the other that it is 

 imperceptible. 



A.jar will fometimes, while it is charging, give a great many fmall corufcations, quickly 

 fuccecding each other, which afterwards ceafe without having caufed a fpontancous explofion^ 

 though the aft ion of the machine be continued. This happens when the uncoated part is 

 nearly clean and dry, but not perfectly fo ; its furface ftill containing fome conducing par- 

 ticles, but not fo connefted, that the eleftric fluid can pafs from one to the other without 

 leaps, or fmall corrufcations on the outfide, which permit the eledric fluid to fpread gradu- 

 ally over its inflde furface, and prevent the undulations from being fo ftrong as to caufe a 

 difcharge. 



After this explanation of the caufe of the flafhes, or corufcations, which are feen upon 

 the uncoated part of a jar while charging, and alfo that fuch corufcations produce undu- 

 lations, which terminate in a fpontaneous explofion ; it remains now to explain how a jar 

 is charged when the corufcations are prevented by breathing upon the uncoated part. 



When a coated jar is breathed into, and then fubjedled to the procefs of chargino-, the 

 ele£lric fluid is forced into it, along the wire in the infide to the coating, where it infl:antly and 

 equally fpreads itfelf over the whole coated part, and at the fame time, though with difficulty, 

 and confequently gradually. It fpreads itfelf over the uncoated part, taking the condenfed film 

 of humidity for its conduftor, as it proceeds from the edges of the coating upwards towards 

 the month of the jar, according to the arrangement of the particles of moifture, and rifes 

 Jiigher or lower, depending entirely on their arrangement, and the force with which it is re- 

 belled from the machine. If the conducing particles be almoft uniformly diffufed over the 

 uncoated part, the v/hole jar, in the infide, will become charged, though the uncoated part 

 ■will be charged in a much kfs degree than the coated, on account of the imperfeftiori 

 of the conducting particles which has adhered to its furface ; no corufcations will be 

 perceived, on account of the gradual and equal difFufion of the eleftric fluid over its infide 

 furface : and though the charging be continued, yet, if the exhaled conducting particles be 

 favourably diffufed, no fpontaneous explofion will happen from one coating to the other, 

 along the uncoated furface, but the jar will either be perforated, or, if it be of fuihcient ftrength 

 to refifl that eifeft, the eleftric fluid will be feen to run in a ftream over the mouth of the 

 jar, as quickly as the machine fupplies it. Whenever a fpontaneous eledlric explofion 

 happens, it muft be from a body of fufficient bulk and conducing property to con- 

 tain that quantity of ele£tric fluid at that point from which it explodes, otherwife no explo- 

 ijon ever happens. But the humid conducing particles are juft fufhcient merely to admit the 

 cleftric fluid, by the aftion of the machine, to be fpread over the furface of the glafs, but in 

 no part of fufficient denfity, either to receive, or contain an explofion. If, therefore, a 

 fpontaneous explofion do happen, it muft either proceed from the infide coating, or the wire 

 which is connected with it to the outfide ; and, if we examine the ftate of the coating, we 

 Ihall underftand, that the edge of the coating (from which part only it is ever poffible to 

 explode), and alfo above it, to a fhort diftance upwards, is as flrongly charged as the coated 

 part ; and by the aCtion of the machine it is fo ftrongly loaded with eleCtric fluid, that it is 

 repulfive in all directions, which keeps back, or entirely (tops, a fpontaneous explofion from 



the 



