ELECTRICITY. 



ELECTRICITY is the operation of a subtile fluid, generally invisible, which ap- 

 pears to be diffused through most bodies. 



If a stick of sealing-wax or a watch-glass be rubbed upon a dry piece of 

 woollen cloth, it will be found, while warm by the friction, that they have 

 acquired the property of attracting small light bodies, as feathers, &c. Some of 

 these will adhere to the surface of the wax or glass, and others will be thrown off 

 from the body, as if they were repelled from it. This phenomenon may be 

 strikingly exemplified by the small apparatus represented at fig. 1. A, is a stand 

 with a bent wire, to which, at the hook, B, a fine silk thread is attached, having at 

 its extremity a small pith ball, c. If the glass rod, 0, be rubbed and presented to 

 the ball, this will be immediately attracted to the glass, and will remain in con- 

 tact with it for a few seconds ; if the glass be now withdrawn, and again pre- 

 sented to the ball, the latter will be repelled (fig. 2). If, instead of the glass, a 

 piece of sealing-wax, rubbed in the same way, be employed, the same effect is 

 produced. Both these electrics have, therefore, in the first place, the power of 

 attracting another body before they have communicated to it any of their own 

 electricity; and, secondly, having communicated a portion of their electricity, 

 they repel it. But a very remarkable circumstance takes place, if we, after 

 having conveyed electricity to the ball, c, by means of excited glass, should pre- 

 sent to it, after the former was withdrawn, excited sealing-wax : the ball, instead 

 of being repelled, as it would be were the ball again applied, is attracted by the 

 wax. If the experiment be reversed, and the excited wax first presented to the 

 ball, and then the excited glass, the latter will be found to repel the ball. Hence, 

 we conclude, that there are two opposite electricities ; namely, that produced by 

 excited glass, to which the name of vitreous, or positive electricity, has been given, 

 and that produced by excited wax, to which the name of re&inous, or negative 

 electricity, has been given. 



Fig. 3 represents the Cylindrical Electrical Machine, consisting of a hollow 

 cylinder of polished glass, c c, revolving upon an axis. Two hollow metallic 

 conductors, D E, are placed parallel to the cylinder on each side, upon two 

 insulated pillars of glass. To one of these conductors, E, a cushion is attached, 

 and held close to the cylinder ; from the upper edge of the cushion there proceeds 

 a flap of oiled silk, which extends over the upper surface of the cylinder to 

 within an inch of a row of metallic points, proceeding from a hollow rod fixed to 

 the side of the opposite conductor. When the cylinder is driven round by the 

 handle, the friction of the cushion upon it produces a transfer of the electric 

 fluid from the latter to the former ; that is, the cushion becomes negatively, and 

 the glass positively, electrified. By the revolution of the cylinder, the fluid 

 adhering to the glass is carried round, and its escape prevented by the silk flap, 

 until it arrives near to the metallic points, which absorb most of the electricity, 

 and convey it to the prime conductpr, i>, which thus becomes positively electri- 

 fied, while the other conductor, having parted with this electricity, is negatively 

 electrified. 



Fig. 4 represents the Plate Electrical Machine. The plate is turned by the 

 handle through the rubber, which is coated with a metallic amalgam, and 

 diffuses the excitement over the glass, the points carrying off a constant stream 

 of positive electricity to the prime conductor, upon the principle already 

 described. 



Fig. 5 represents the Hydro-Electric Machine, an apparatus of recent date 

 and construction, and of immense power. It consists of a steam boiler, A, in- 

 sulated on stout glass pillars. The steam is made to issue through a great num. 

 ber of bent iron tubes, B B, terminating in jets of wood. An insulated projecting 

 eonductor, c, is placed in connexion with the boiler, for the purpose of col'lecling 

 the excited electricity ; and another conductor, D, formed of a metallic case 

 having several rows of points, is placed immediately in front of the jeta, to re- 

 ceive and carry off the opposite electricity of the steam, and prevent ita return to 

 the boiler, by which the excited forces would be neutralized. The electricity 

 thus produced is the result of the friction of condensed particles of water, whilst 

 teing driven by the still issuing steam through the jets, these watery particles, 

 performing the office of the glass plate, or. cylinder of the common machine, and 

 giving out vitreous electricity. The wood jets and pipes act as the rubfcei, and 

 give out resinous electricity. . ' r ; 



