EI^ECTRICAL-MA-Clt'lTIS^ I2j' 



k coated on both fides with a fufficient thicknefs of v'arnifli *. 

 , The bow of the conduaor, which confifts of a hall fix J"ches J^'j.e^c^^^^u^or 

 in diameter, to which is added a moveable tube with feveral 

 fitting pieces that terminate in balls of different fizes, had at 

 firil, at each of its extremities, as in Van-Marum's machine, 

 a brafs cylinder three inches long and one inch thick, with 

 an hemifphere at each end. But as condu6tors of this corii'" 

 Aruflion are liable to difcharge themfelves, on account of thaf 

 faiall diameter of their hemifpheres, even before they have 

 received their full charge, I have preferred putting one Ixafs 

 ball three inches in diameter on the upper end of the fupqrior 

 condudor ; and another on the lower end of the inferior con- 

 ductor. Thefe balls likewife ferve the purpofe of collecting 

 the fluid excited at the extreme parts; for the balls, both 

 above and below, projedl confiderably beyond the thicknefs 

 of the plate, and prevent the efcape of the fluid as much as is 

 poflible, particularly in a machine lefs high in proportion than 

 that of Van-Marum. The conductor is only 4f inches diflant 

 from the table, confequently only half the difiance of Van- 

 Marum's ; yet the fluid does not efcape, till the conductor is 

 overcharged. The efcape ot the fluid is prevented likewife The efcape of 

 by an infulating fquare of glafs 42 inches, niade rough and gj^Cs piji^e pigeed 

 eoated with copal varnifli, which is placed on the table beneath on the table be- 

 the lower conduaor, its three fliort feet being let into the ^^'^^j."^*^*^ '^'"'' 

 table. This fquare of glafs may be ofed on feveral occafions 

 as an infulating fi:and. 



The four rubbers are made of dry walnut wood foaked in The rubbers 

 amber varnifli, and are 5^ inches long, If broad, and a little ^ "-" ^ * 

 more than | of an inch thick. The metallic plate that com- 

 municates with the leather covered with amalgam, is only an 

 If inch broad, and is fixed externally to the centre of the piece 

 of wood. The rubbers are preflfed toward the glafs by means of 

 a fpring. They are covered with a piece of thick woollen, 

 upon which is a piece of fine neat's leather. After the leather 

 is faftened to the wood, it is wetted, and prefixed between 



• This varnifli is compofed of copal, two ounces; gura fanda- Amber varnifli 

 rac, one ounce j white amher, one -ounce 3 olibanum, half an ^Y,''°^'"'^ '^^ 

 ounce J powdered and diflblved in one pound of alcohol by digef- 

 tion in a glafs matras. When the folution is perfeilly cold, it is 

 pafled through the filter, 



two 



