ELECTRICAL APPARATUS. 257 



ten inches in diameter, and from eight to fourteen inches in 

 length, supported on a rectangular base by two upright 

 turned columns, by means of caps on the ends of the cylinder, 

 the one having a short pivot, the other a long one, passing 

 through the column, and terminated by a winch and handle 

 by which the cylinder is turned on its axis. The upper part 

 of the 'column is divided horizontally at the centre of the 

 pivot, or axle, and secured by screws each side of the axle ; 

 by this arrangement the cylinder may easily be taken out 

 and put in the frame. Before the cylinder is a cushion, 

 which extends in length to within an inch of either end of 

 the cylinder, which should be soft and yielding ; the cushion 

 is supported by a glass pillar where negative electricity is 

 required, but more commonly by a turned mahogany pillar, 

 having at its base a slide to move backwards and forwards, 

 with a stout screw to clamp it fast, whereby the pressure on 

 the cushion can be regulated ; the conductor is a cylinder 

 of metal from fourteen to eighteen inches in length, and 

 about four inches diameter, with rounded ends, usually 

 japanned black, and is supported on the side of the cylinder 

 opposite the rubber, having a row of brass points on the side 

 towards the cylinder for collecting the fluid ; there are 

 sockets with holes at each end of the conductor, and also 

 on the top for attaching apparatus, wires, &c. To the up- 

 per edge of the cushion is attached a piece of black silk, of 

 the width of the rubber, which extends over the cylinder to 

 within an inch of the row of points. 



Price, 4 inch, $ 8.00 ; 5 inch, $10.00. 



" 6 " $12.00; 7 " $14.00. 



" 8 " $16.00; 9 " $18.00. 



10 " $22.00. 



The Small Cylinder Electrical Machine. This plate (Fig. 

 273, next page) represents the cylinder electrical machine, 

 in the simplest and one of the most convenient forms in 

 which it can be constructed. The base is a rectangular 

 piece of wood, having upright pieces of wood firmly attached 

 at the base, and supporting the caps attached to the cylin- 

 der ; to one of which is a handle, by which the cylinder is 

 turned. On one side is a cushion of leather fixed to a pillar, 

 and having a screw at the base to regulate the degree of 

 pressure on the cylinder. On the other side of the cylinder 

 i*i R metal cylinder with rounded ends, supported by a ghiss 



