Electricity as known to the Moderns.
Having seen, in the preceding section, the very limited knowledge of electricity possessed by the ancients, we now come to give an account of what may properly be called its real origin, and to trace its progress to the present day. In doing this, we shall be careful to note all the original authors who have touched upon this subject; and to exhibit most of their discoveries.
We believe it to be generally the case, that, in the earlier periods of a science, the mind is curious to observe the gradual developement of principles, and the gradual increase of facts, however unimportant these facts may afterwards appear. But as the science progresses, as the ground widens and observations multiply, this curiosity proportionably abates, and we require of the historian selection rather than detail.
However minute, therefore, the history of the first stages of this branch of philosophy must be, the after periods will exact only a careful selection of those more prominent discoveries, which show the advances of the science and mark its gradations.
During the sixteenth century, the phenomena of magnetism having engaged the study of philosophers, they were naturally led to bestow some attention on substances which appeared to possess similar properties with the load-stone. Indeed, it was not till after 1729 that the idea was entertained, that electricity was a distinct fluid, or any thing else than a certain property of bodies, resembling magnetism; nor was any other meaning affixed to the word, than a power of attracting and repelling.
Fifteen centuries having elapsed from the time of Theophrastus, William Gilbert, physician to king James I, in 1600 published a latin work, entitled, De Magnete, magnetesque corporibus, in which, having discussed the phenomena of magnetism, he, towards the close, relates a great variety of electrical experiments.
The principal merit of this philosopher is, that he greatly augmented the list of electrical substances, noted the bodies on which electrics can act, and remarked several circumstances relating to the manner of their action.
He enumerates, as having the power of attracting light bodies, Diamonds, Saphirs, Carbuncles, Iris, Opals, Amethysts, Beryl, Crystal, Bristol-stones, Sulphur, Mastick, Hard Wax, Hard Rosin, Arsenic, Sal-gemm, Rock-Alum, common-glass, Stibium, or glass of Antimony. He also observed that the influence of these substances extended, not only to leaves and straws, but to all matter which was not extremely rare. Friction, he says, is, in general, necessary to excite the virtue of these substances; and the most effectual friction, he affirms, is that which is light and quick. Electrical appearances, he asserts, were strongest when the air was dry, and the wind north or east, at which time electrics would act ten minutes after excitation.
The simple experiments of this philosopher were mostly made with long thin pieces of metal, and other substances freely suspended on their centers, to the extremities of which he presented the electrics he had excited.
The phenomena of magnetism were accounted for, in the time of Gilbert, by means of emanating effluvia, and he applies the same theory to the explanation of electrical attraction, imagining it to be performed in the same manner as the attraction of cohesion. Two drops of water, rush together when they are brought into contact, and electrics, he says, are virtually brought into contact by means of their effluvia. Effluvia illa tenuiora concipiunt et amplectuntur corpora, quibus uniuntur, et electris tanquam extensis brachiis, et ad fontem propinquitate, invalescentibus effluviis, deducuntur. “Those subtle effluvia continually embrace certain bodies, to which they are united, as it were by their extended electric arms; and the effluvia prevailing, the bodies are drawn to the contiguous source of the effluvia.”