3 1 6 Large Eleftrical Machine. [Book IV. 



lar manner, by rubbing a flick of fulphur or fcaling 

 wax. 



Thefe tubes being but fmall, the electric fluid pro- 

 duced by thefe means is but feeble in its effects. We 

 have feen that a method was contrived to turn a globe 

 of glafs upon its axis, by means of a machine with a 

 winch or multiplying wheel ; this method admitted of 

 a larger furface, and the friction was performed with 

 greater eafe, by means of a rubber being placed clofe 

 to the revolving globe. 



To conflruct a machine fufficiently large for all the 

 purpofes of electrical experiments, M. Briffon directs 

 that the wheel RO (fee Plate XXVI. Fig. i.) fhould 

 be at leaft four feet in diameter, and be turned round 

 in a ilrong and folid frame H I C D. He directs fur- 

 ther, that there mould be two handles M, m, fo that 

 two men may be employed at once in certain cafes, to 

 give a fufficient friction to the globe to augment the 

 effects. The globe S ought to be carried round be- 

 tween two fmall ports N, which ought to be ib placed 

 that they may be drawn farther from or nearer to the 

 wheel, in order to admit the cord to be moved com- 

 modioufly whenever it is contracted or extended. It 

 is allb neceffary that one of thefe fmall polls mould be 

 moveable, that it may be placed either nearer to or 

 farther from the other, fo that globes of different dia- 

 meters may be placed in the machine; the cord of the 

 wheel R O mould communicate immediately with the 

 pulley P of the globe S. 



When this machine is ufed for the purpofes of elec- 

 tricity, the globe S fhould be turned according to the 

 order of the cyphers i i 3, and its equator rubbed 

 with a leathern cufhion fluffed with horfe hair, this 

 may alfo be done by the hands when they are clean 



and 



