312 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



To insure success in this experiment, it is necessary to 

 pass the charge from the jar, through a few inches of water, 

 disconnecting the metallic wire or chain, dipping it in the 

 water, or pass it through a few inches of wet linen thread 

 connected with the wires or chain through which the dis- 

 charge passes. Price, $6.00. 



Cylinder Electrical Machine, with detached Conductor. 

 (Figure 372.) A is a glass cylinder, having at each end of 

 it a cap of wood or brass, and supported by a stand, with 

 two uprights. The end of one cap is turned with a pivot, 

 which fits into a hole near the top of one of the uprights. 

 The other cap is turned with a similar pivot, and has beyond 

 this a flange and a square gudgeon upon which a handle 

 fits. This end of the cylinder is supported in a similar man- 

 ner to the other end, but instead of a hole merely being 

 bored in the upright leg, a portion is cut away, that the 

 cylinder may be the more easily taken out, and put up again 

 in its place ; it may be secured, when there, by a pin run 

 through the upright just above the axis of the cap. Be- 

 hind the cylinder is a cushion, which extends in length to 

 within an inch of either end of the cylinder ; it is from one 

 to two inches in width, according to the size of the cylinder. 

 On the lower part of the cushion is glued a flap of leather, 

 the rough side outwards ; and on the edge of the leather 

 the silk flap which passes over the cylinder when in action. 

 The cushion is supported sometimes by a thick rod of glass 

 with a wooden spring at the top of it, as in the figure ; at 

 other times a springy piece of wood alone is used. It is 

 fastened at the top to the cushion by a hand-screw, which 

 passes through the support, and is fixed by a thread in the 

 back of the cushion itself. The lower end of the support for 

 the cushion is made so as to slide backwards and forwards, 

 either on the top, or, still better, underneath the stand, and 

 is held in its position by a thumb-screw. 



B represents the prime conductor, formed either of wood 

 covered neatly with tin foil, or of metal. It has round and 

 smooth ends, at one of them a ball and wire for the suspend- 

 ing of various apparatus, at the other a projecting wire fur- 

 nished with a row of points to collect the fluid when disturbed 

 by the cylinder. It is necessarily supported upon a glass 

 pillar, sometimes attached at the lower end to the same 

 stand as the rest of the machine, in which case the conductor 



