DESCRIPTIVE ELI:Am:Herm Electricity, is that branch of the science which describes all the various phenomena which are either produced, or supposed to be produced, by the same cause as the phenomena of excited amber. It na turally divides itself into three heads : 1. The p:ienome na of electricity produced by friction ; 11. The phenome na of electricity produced without friction ; and III. The effects of electricity, comprehending its mechanical, chemical, and magnetical effects, and its influence upon animal and vegetable bodies.
On the Phenomena of Electricity produced by Friction As friction is the mean which has almost al%%.,)s been employed for the production of electrical phenomena, and as the various discoveries which have been made respecting the communication, the distribution, and the dissipation of the electric matter, have been made by electricity excited in this manner, we shall introduce into the present Chapter an account of these important results, although they are equally deducible when the electricity has been either excited by heat, or obtained from any other source.
IF we rub a piece of amber -.vith dry fur, or woollen cloth, and then hold the amber over any light substances, such as small pieces of paper, or the down of a feather, the light body will be attracted by the amber. The same effect will be produced, by rubbing the glass of a watch against the sleeve of the coat; and still more powerfully, by rubbing a glass tube with a piece of dry silk. In this latter case, when the tube is rubbed in the dark, sparks of brilliant light, accompanied with a crackling sound, will be emitted as long as the friction is continued. In like manner, if a dry black silk rib bon, about two feet long, be laid upon a white one of the same length, and be drawn over woollen cloth, or silk velvet, or even between the finger and the thumb, they will be found to adhere strongly to each other. When separated, they will attract one another, and rush together with considerable velocity. In a dark room, the separation of the ribbons will be accompanied with a flash of light ; and any one of the ribbons, when sepa rated from the other, will attract light substances like the amber and the glass already mentioned.
Now in these three simple experiments, the amber, the glass, and the silk ribbons have obviously received new properties, which they did not possess before they were rubbed, viz. the property of attracting light bodies, and the property of emitting light in the dark. These properties arc called electrical. The anther, the glass, and the ribbons, are said to be excited by friction. The power of drawing to themselves light bodies, is called electrical attraction, to distinguish it from the attractions of cohesion, of gravity, and of magnetism. The light emitted in the dark, is named the electric spark, or elec tric light..; and the body which is capable of acquiring these properties is called an electric.
By rubbing a great number of other bodies with woollen cloth, fur, silk, &c. they arc found to exhibit the same properties as amber and glass ; while another lass of bodies exhibit no such properties, with what ever substances, and in whatever manner, they arc rub bed. Hence bodies are divided into two great classes, viz. electrics, or those which acquire by friction the fa culty of exhibiting electrical properties ; and non-elec trics, or those which are incapable of acquiring electri cal properties by friction. The following is a list of electrics arranged in the order of their perfection, those being regarded as the most perfect which produce the most powerful electricity by the least friction.
Glass, and all vitrifications, even those of metallic sub stances.
The precious stones, such as diamonds, garnets, rubies, topazes, emeralds, sapphires, the most transparent of which are generally the most perfect.
Amber.
The substances in the above list which are marked in italics, are evidently such as cannot be excited by fric tion ; but they are inserted in the table, from their pos sessing, like the other electrics, another property, which we shall soon have occasion to notice. All bodies r.ot contained in the preceding enumeration, cannot be con sidered as non-electrics. Those only are properly en titled to that name, which have been found incapable of electrical excitation. A list of them will be introduced with more propriety under another head.