Electricity. The word Electricity denotes a peculiar state, of which all bodies are susceptible, and which is supposed to depend upon the presence of a substance called the electric fluid. Some of its phenomena were known to the ancients, particularly those attractions and repulsions which a piece of amber, alter being rubbed, exhibits, with regard to hairs, feathers, and other light bodies; and it was from its power of drawing light substances to it when rubbed that the Greeks gave amber the name Elek-tron, which is the origin of the word Electricity. Thales, who lived six centuries before the Christian era, was the first who observed the electrical properties of amber; and he was so struck with the appearances, that he supposed it to be animated. Mr. Boyle is supposed to have been one of the first persons who got a glimpse of the electrical light, or who seems to have noticed it, by rubbing a diamond in the dark. Sir Isaac Newton was the first who observed that excited glass attracted light bodies on the side opposite to that on which it is rubbed.

An electric is any substance, which being excited or rubbed by the hand, or by a woollen cloth, or other means, has the power of attracting light bodies. If a piece of sealing-wax be rubbed briskly with the sleeve of your coat, a silk handkerchief, etc, for some time, and then held near hair, feathers, bits of paper, or other light bodies, they will be attracted; that is, they will jump up, and some of them will adhere to the wax. If a tube of glass, or small phial, be rubbed in a similar manner, it will answer much better. If this operation be performed in the dark, something luminous will be seen, which is called the electric matter or fluid ; and all bodies that we are acquainted with have more or less of it in them ; though it seems to lie dormant till it be put into action by rubbing. The air, and everything, is full of this fluid, which appears in the shape of sparks; the rubbing of the glass with the hand collects it from the hand; and the glass, having now more than its natural share, parts with it to any body that may be near enough to receive it. The substance rubbed and that with which it is rubbed are always found to be oppositely electrified- the one body having more and the other less than its natural share; indeed, one kind of Electricity is never obtained without, at the same time, the productions of the other. Those bodies which have been called Electrics, will not convey electricity from one body to another, and therefore they are termed Non-Conductors. The most remarkable are - glass, and all vitreous substances, precious stones, resins, amber, sulphur, baked wood, wax, silk, cotton, wool, hair, feathers, paper, white sugar, air, oils, metallic oxides, all dry vegetable substances, and ail hard stones. Those bodies, which, when rubbed ever so much, do not exhibit electricity, are called -Non-Electrics. They convey electricity from one body to another, and therefore are denominated Conductors; they are as capable of having electricity developed upon them by friction as those bodies which have been called "electrics," but it is conducted away as fast as it is produced. Some of them conduct electricity much better than others. The principal conductors are the metals, charcoal, all fluids except dry airs and oils, most saline substances, and stony substances. Woollen and silk, when wet, will, by means of the water, conduct electricity.

When a body has more than its natural quantity of this fluid, it is said to be electrified positively, or plus; and when it has less than its natural quantity, it is sa d to be electrified negatively, or minus. When bodies are electrified either of these ways, they repel each other; but if some be electrified plus, and others minus, they mutually attract; or if one body be electrified plus, and the other not electrified in either way, they also attract each other. There are some fishes which possess the extraordinary faculty of being able, at pleasure, to communicate shocks like those of an electric battery or galvanic pile, to any animal that comes in contact with them. They are called the torpedo, the gymnotus electricus, and the silurus Indicus. The most remarkable of these is the Gymnotus Electricus, or Electric Eel, which is frequently found in the marshes and stagnant pools of Guiana, and other countries of South America. The shocks they give are exceedingly severe; and Humboldt mentions a road which has been totally abandoned, because the mules, in crossing a wide ford, were, by these violent attacks, often paralysed and drowned. Even the angler on the bank was not exempt from danger, the shock being conveyed along his wetted rod and fishing-line. The Electric Eel is sometimes twenty feet long. The electricity of all those fishes is exerted by them only when they please, and of course only while they are alive. After the animal has discharged its electrical matter, the next shock is weaker; and when the animal is exhausted, it has lost the power of producing any effect for Come time.

Then is no longer any doubt that the cause of thunder is the same with that which produces the ordinary phenomena of electricity. The resemblance between them is indeed to great, that we cannot believe thunder itself to be any other than a grander species of electricity.