$(')& ELECTRICITY. 



sufficiently. In this case the best expedient is to 

 connect the chain of the rubber, by means of a 

 long wire, with some moist ground, or with the 

 iron-work of a water-pump, by which means the 

 rubber will be supplied with as much electric fluid 

 as is required. 



When a sufficient quantity of amalgam has been 

 accumulated upon the leather of the rubber, and 

 the machine does not work very well, then, instead 

 of putting more amalgam, it will be sufficient to 

 take the rubber off, and to scrape a little off 

 that which is already upon the leather. 



It will be often observed, that the globe or cy- 

 linder, after being used some time, contracts black 

 spots, occasioned by the amalgam, or some foulness 

 of the rubber, which grow continually larger, and 

 greatly obstruct its electric power. These spots 

 must be carefully taken off, and the cylinder must 

 be frequently wiped, in order to prevent its con- 

 tracting them. 



In charging electric jars in general, it must be 

 observed, that every machine will not charge them 

 equally high. That machine, whose electric power 

 is the strongest, will always charge the jars highest. 

 If the coated jars, before they are used, be made a 

 little warm, they will receive and hold the charge 

 the better. 



If several jars be connected together, among 

 which there is one that is apt to discharge itself 

 very soon, then the other jars will also be soon dis- 

 charged with that; although they may be capable 

 of holding a very great charge by themselves. 

 When electric jars are to be discharged, the elec- 

 trician must be cautious, lest, by some circumstance 

 not adverted to, the shock should pass through any 

 part of his body; for an unexpected shock, though 



