Exp. 9. If the circular ring, in the preceding experi ment, is insulated, and stands about an inch and a half from the flat surface of a table, and if a ball of glass, about two inches in diameter, is placed upon the table, and within the ring, it will first be attracted towards the ring, and after touching the ring and becoming elec trified at the point of contact, this point will recede and be attracted by the table, while the ring attracts another part of the ball. Hence the hall will 'evolve about its axis, and move round the circumference of the ring.
.Exp 10. Fix a piece of scaling-wax at the end of a wire, and insert it into one of the holes of the prime con ductor. When the sealing-wax is softened by heat, turn the cylinder, and fine waxen fibres will be sepa rated from the wax, and if received on a sheet of paper, will cover it with threads like red wool. By receiv ing it upon paper, and afterwards gently heating it, the result of the experiment will be rendered perma nent.
If the melted scaling-wax is held in the hand, at a distance from the conductor, the waxen filaments will dart from the wax to the conductor, and be condensed into a kind of red wool as before.
Exp. 11. Place a piece of lighted camphor in a me tallic spoon which communicates with the prime con ductor. NVhen the conductor is electrified, the cam phor will throw out numerous ramifications, and will shoot forth like a growing vegetable.
Exp. 12. Take a capillary tube of such a diameter, that water will not drop from it, but be retained in vir tue of the attraction of cohesion. Bring this tube near an electrified prime conductor, and the water will be drawn out of it and discharged in a continued stream. The electrified jet sometimes divides into several streams, and is accelerated in proportion to the small ness of the bore. In this experiment, the capillary at traction of the tube is overcome by the more powerful attraction of the conductor.
In all these various cases of attraction and repulsion, and in every other case of electric action, two bodies electrified positively repel each other, and also two bodies electrified negatively, while a body electrified positively always attracts a body possessing negative electricity.
Tun electrical effects which we have hitherto been considering are of the most transitory kind, and exist only during the excitation of the electric. Although the electricity developed by the friction of a glass tube, or of a glass cylinder, was sufficiently strong for exhi biting many interesting experiments, and for the pur pose of investigating the nature and properties of the electric Ihtid, yet it was not till the method of accumu lating electricity was discovered, that philosophers be came acquainted with the overpowering energy of this extraordinary agent.
This great step in the proa,Tess of the science was made by the celebrated Muschenbroek, in his invention of the Leyden phial or jar. This instrument is repre sented in Plate Fig. 5, where a b is a cylin drical glass vessel, having the lower part b c coated with tinfoil all around, the inside being coated in a si milar manner, and to nearly the same height. Through a perforation in the piece of wood or cork which fills the mouth of the jar, is inserted a brass rod d e, ha ving a small ball of brass d at one end, and two or three inches above the top, and communicating by its other end with the inside coating, by means of a chain or wire.
If the jar thus constructed is held to the conductor of an electrifying machine, so that the knob d may he about half an inch from it, a number of sparks will pass from the conductor to the knob d, and after grow ing weaker and weaker, they will at last cease. The electricity from the conductor has now been accumu lated in the jar, and the jar is said to be charged. If any person now holds the jar in one hand by the out side coating, while with the other he touches the knob d, he will hear a sharp sound, accompanied with a bril liant flash of light, and will experience a severe and most disagreeable concussion in his wrists, elbows, and breast, the accumulated electricity of the jar having passed through his body. This sensation is called the electric shock, and the jar is said to be discharged.
The electric shock may also be experienced by any number of individuals, provided they take one ano ther by the hand, and form the line of communication between the inside and outside coatings of the If the person at one end of the line touches the outside coating, then the shock will be felt by every individual that composes it, the instant that the person at the other extremity touches the knob of the phial. In this manner the Abbe Nollet electrified 180 of the French guards in the king's presence ; and, at the Carthusian convent in Paris, the whole of the religious formed a line of 5400 feet by means of iron wires between every two persons, and were all simultaneously electrified upon the discharge of the phial.