250 



BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE. 



right angles through its centre. It is rubbed by two pair 

 of cushions, fixed at opposite parts of the circumference by 

 elastic frames of thin mahogany, which are constructed so 

 as to press the glass plate between them with the requisite 

 force, by means of regulating screws. A brass prime con- 

 ductor, supported by a stout glass rod, is fixed to the frame 

 of the machine, terminated at one end by a wire, with a 

 brass ball, and having branched extremities opposite each 

 other, and near the extreme diameter of the plate, in a 

 direction at right angles to the vertical line of the opposite 

 cushions. The branched extremities of the conductor are 

 furnished with pointed wires, that serve to collect the elec- 

 tricity from the surface of the excited plate. This form of 

 ihe* plate electrical machine is now little used, the more 

 modern style being preferable. Price, 12 inch, $25.00. 



15 " $30.00. 



18 " $38.00. 



F^ 269 - Plate Glass Electrical 



Machine (French Plan). 

 This arrangement (Fig. 269) 

 represents one of the French 

 forms of mounting the plate 

 glass electrical machine, 

 having but one pillar sup- 

 port, made very stout, to 

 the axis of the machine. 

 Two pairs of rubbers at- 

 tached to large brass balls, 

 are supported by insulated 



lass P illars > the balls be - 

 m & connecte d together by a 

 brass tube, in the form of 

 an arch, extending over the 

 plate, forming the negative conductor to which the rubbers 

 are attached. The positive conductor with circular arms, 

 having rows of brass teeth at the ends, is mounted on a sepa- 

 rate movable insulated stand. 



Price, with 20-inch plate, $50.00. 



Plate Electrical Machine, for positive and negative Elec- 

 tricity. This electrical machine, having a frame of maho- 

 gany or rosewood, in the form of a cross, is represented in 



