[ 79 3 
VII. EleSirtcal Experiments by Mr. Edward 
Nairne, of London, Mathematical In - 
firument-maker , made with a Machine of 
his own TVorhnanfhip, a Defcription of 
which is prefixed. 
Redde, Dec. 9>TT' I G. Ift. [Tab V. and VI.] is are- 
1 773 * prefentation of the machine, with 
its apparatus, as was ufed when electrical fparks 
were drawn from the conductor, in a pofitive ftate. 
The glafs cylinder, of this machine, is 12 inches 
diameter, and the cylindrical part 19 inches long, 
exclufive of the necks j the cufhion or rubber is 
14 inches long, and 5 inches broad, fupported by 
two wooden fprings ; which lprings are fixed oft 
two glafs rods, which lie horizontal under the cy- 
linder, and ferve to infulate the cufhion. The 
conductor to this machine is 5 feet long, and 12 
inches diameter ; at the end of it is a fiiort brafs 
rod, with a ball j it is fupported on two ftands, with 
folid glafs rods or pillars. The ball, which is re- 
prefented as receiving the eleCtrical fpark from 
the conductor, is of brafs, and fixed to the end of 
a brafs tube, which tube is moveable, in a hole in 
the top of the receiving ftand ; from the bottom 
of this ftand a chain paffes along the floor, till it is 
in 
