Watson's writings now carried the field of active discovery across the Atlantic, and for the first time an American scientist appeared—a scientist who not only rivalled, but excelled, his European contemporaries. Benjamin Franklin, of Philadelphia, coming into possession of some of Watson's books, became so interested in the experiments described in them that he began at once experimenting with electricity. In Watson's book were given directions for making various experiments, and these assisted Franklin in repeating the old experiments, and eventually adding new ones. Associated with Franklin, and equally interested and enthusiastic, if not equally successful in making discoveries, were three other men, Thomas Hopkinson, Philip Sing, and Ebenezer Kinnersley. These men worked together constantly, although it appears to have been Franklin who made independently the important discoveries, and formulated the famous Franklinian theory.
Working steadily, and keeping constantly in touch with the progress of the European investigators, Franklin soon made some experiments which he thought demonstrated some hitherto unknown phases of electrical manifestation. This was the effect of pointed bodies "in DRAWING OFF and THROWING OFF the electrical fire." In his description of this phenomenon, Franklin writes:
"Place an iron shot of three or four inches diameter on the mouth of a clean, dry, glass bottle. By a fine silken thread from the ceiling right over the mouth of the bottle, suspend a small cork ball, about the bigness of a marble; the thread of such a length that the cork ball may rest against the side of the shot. Electrify the shot, and the ball will be repelled to the distance of four or five inches, more or less, according to the quantity of electricity. When in this state, if you present to the shot the point of a long, slender shaft-bodkin, at six or eight inches distance, the repellency is instantly destroyed, and the cork flies to the shot. A blunt body must be brought within an inch, and draw a spark, to produce the same effect.
"To prove that the electrical fire is DRAWN OFF by the point, if you take the blade of the bodkin out of the wooden handle and fix it in a stick of sealing-wax, and then present it at the distance aforesaid, or if you bring it very near, no such effect follows; but sliding one finger along the wax till you touch the blade, and the ball flies to the shot immediately. If you present the point in the dark you will see, sometimes at a foot distance, and more, a light gather upon it like that of a fire-fly or glow-worm; the less sharp the point, the nearer you must bring it to observe the light; and at whatever distance you see the light, you may draw off the electrical fire and destroy the repellency. If a cork ball so suspended be repelled by the tube, and a point be presented quick to it, though at a considerable distance, 'tis surprising to see how suddenly it flies back to the tube. Points of wood will do as well as those of iron, provided the wood is not dry; for perfectly dry wood will no more conduct electricity than sealing-wax.
"To show that points will THROW OFF as well as DRAW OFF the electrical fire, lay a long, sharp needle upon the shot, and you cannot electrify the shot so as to make it repel the cork ball. Or fix a needle to the end of a suspended gun-barrel or iron rod, so as to point beyond it like a little bayonet, and while it remains there, the gun-barrel or rod cannot, by applying the tube to the other end, be electrified so as to give a spark, the fire continually running out silently at the point. In the dark you may see it make the same appearance as it does in the case before mentioned."(3)
Von Guericke, Hauksbee, and Gray had noticed that pointed bodies attracted electricity in a peculiar manner, but this demonstration of the "drawing off" of "electrical fire" was original with Franklin. Original also was the theory that he now suggested, which had at least the merit of being thinkable even by non-philosophical minds. It assumes that electricity is like a fluid, that will flow along conductors and accumulate in proper receptacles, very much as ordinary fluids do. This conception is probably entirely incorrect, but nevertheless it is likely to remain a popular one, at least outside of scientific circles, or until something equally tangible is substituted.
FRANKLIN'S THEORY OF ELECTRICITY
According to Franklin's theory, electricity exists in all bodies as a "common stock," and tends to seek and remain in a state of equilibrium, just as fluids naturally tend to seek a level. But it may, nevertheless, be raised or lowered, and this equilibrium be thus disturbed. If a body has more electricity than its normal amount it is said to be POSITIVELY electrified; but if it has less, it is NEGATIVELY electrified. An over-electrified or "plus" body tends to give its surplus stock to a body containing the normal amount; while the "minus" or under-electrified body will draw electricity from one containing the normal amount.
Working along lines suggested by this theory, Franklin attempted to show that electricity is not created by friction, but simply collected from its diversified state, the rubbed glass globe attracting a certain quantity of "electrical fire," but ever ready to give it up to any body that has less. He explained the charged Leyden jar by showing that the inner coating of tin-foil received more than the ordinary quantity of electricity, and in consequence is POSITIVELY electrified, while the outer coating, having the ordinary quantity of electricity diminished, is electrified NEGATIVELY.
These studies of the Leyden jar, and the studies of pieces of glass coated with sheet metal, led Franklin to invent his battery, constructed of eleven large glass plates coated with sheets of lead. With this machine, after overcoming some defects, he was able to produce electrical manifestations of great force—a force that "knew no bounds," as he declared ("except in the matter of expense and of labor"), and which could be made to exceed "the greatest know effects of common lightning."