322 ELECTRICITY. 



about ten inches in diameter, and is furnished with 

 two caps, either of wood or brass, into which its 

 two short necks are firmly cemented. Each of 

 those caps has a pin, or pivot, which turns in a 

 hole through a wooden piece that is cemented on 

 the top of a glass-pillar, as at E and F, on the glass- 

 pillars EG, F H, which are firmly fixed to the 

 bottom board A B. One of those pins passes 

 quite through the wooden piece at E, and has a 

 square termination to which the winder I is ap- 

 plied, and secured on by means of a screw-nut. 

 By this winder the cylinder is turned round ; part 

 of it is made of glass, in order the more effectually 

 to prevent the escape of the electric fluid from the 

 cylinder. K is the rubber, which is made of silk, 

 or leather stuffed with hair, and L is a flap of silk 

 fastened to it, and covering part of the cylinder, to 

 prevent the dispersion and escape of the electric 

 fluid. This rubber or cushion is fastened to a 

 spring which proceeds from a socket cemented on 

 the top of the glass- pillar M. The lower part of 

 the pillar is fixed into a small board which slides 

 upon the bottom board of the machine, and by 

 means of a screw-nut and a slit, maybe fixed more 

 or less forward, in order that the rubber may press 

 more or less upon the cylinder. N is a glass-pillar 

 which is fixed upon the bottom-board, and sup- 

 ports the prime conductor O P, of hollow brass or 

 tin-plate, which has the collector or pointed wires 

 at Q, and a knobbed wire at P. From this brass 

 knob R, a longer spark may be drawn than from 

 any other part of the conductor. But this knob- 

 bed wire is only screwed into the conductor, and 

 may be easily removed from it. 



The simple rubber, such as has been described, 

 will produce a very slight excitation of the cylin- 



