In 1630, Nicolaus Cabœus at Terrara, repeated Gilbert’s experiments and made some progress, increasing the list of electrics; as also did Mr. Boyle in the year 1670. He made some discoveries which had escaped the observation of those who preceded him. Cotemporary with Mr. Boyle, Otto Guericke, burgomaster of Magdeburg, (the inventor of the air pump,) made some advances. He constructed a sulphur globe, which he mounted upon an axis, in a wooden frame, and causing it to revolve, at the same time rubbing the globe with his hand, performed a variety of electrical experiments. He was the first to discover, that a body once attracted by an excited electric, was repelled by it, and not again attracted until it had touched some other body. He observed the light and sound produced by the electric fluid, while turning his electrical machine. Dr. Wall about the same time observed the light and sound produced by rubbing pieces of amber with wool, and also experienced a slight shock. He compared the sound and light of the electric fluid so produced, to thunder and lightning.
Sir Isaac Newton also engaged in similar electrical experiments, and gave an account of them to the Royal Society in 1675. Mr. Hauksbee, whose writings are dated 1709, distinguished himself by experiments and discoveries in electrical attraction, and repulsion, and electric light. He constructed an electrical machine, adopting the glass, instead of the sulphur globe. He experimented upon the subtilty and copiousness of the electric light, and likewise upon the sound and shocks produced by the fluid. After the death of Mr. Hauksbee, the science of electricity made but slow progress, and few experiments were made for twenty years. In the year 1728, Mr. Stephen Grey, a pensioner at the Charter House, commenced his experiments with an excited glass tube. He and his friend, Mr. Wheeler, made a great variety of experiments in which they demonstrated, that electricity may be communicated from one body to another, even without being in contact, and in this way, may be conducted to a great distance. Mr. Grey afterwards found, that, by suspending rods of iron by silk or hair lines, and bringing an excited tube under them, sparks might be drawn, and a light perceived at the extremities in the dark. He electrified a boy suspended by hair lines; and communicated electricity to a soap bubble blown from a tobacco pipe. He electrified water, contained in a dish, placed upon a cake of rosin, and also a tube of water. He made some curious experiments upon a small cup of water, over which, at the distance of an inch, he held the excited tube. He observed the water to rise in a conical shape, from which proceeded a light; small particles of water were thrown off from the cone, and the tube moistened.
Mr. Du Fay, intendant of the French king’s gardens, repeated the experiments of Mr. Grey in 1733. He found that by wetting the pack-thread he succeeded better with the experiment of communicating the electric virtue through a line 1256 feet in length. He made the discovery of two kinds of electricity, which he called vitreous and resinous; the former produced by rubbing glass, and the latter from excited sulphur, sealing wax, &c. But this he afterwards gave up as erroneous. Mr. Grey, in 1734, experimented upon iron rods and gave rise to the term metallic conductors. He gave the name pencil of electric light to the stream of electricity, such as is seen to issue from an electric point. He suggested the idea that the electric virtue of the excited tube was similar to that of thunder and lightning, and that it could be accumulated.
Dr. Desaguliers commenced his experiments in 1739. He introduced the term conductor to that body to which the excited tube conveys its electricity. He called bodies in which electricity may be excited by rubbing or heating, electric per se; and non-electric when they receive electricity, and lose it at once upon the approach of another non-electric. In the year 1742, several Germans engaged in this subject. Mr. Boze, a professor at Wittemburg, revives the use of Hauksbee’s globe, instead of using Grey’s glass tube, and added to it a prime conductor. Mr. Winckler substituted a cushion instead of the hand, which had before been employed to excite the globe. Mr. P. Gordon, a Benedictine monk and professor of philosophy at Erford, was the first who used a cylinder instead of a globe. With his electrical machine he conveyed the fluid through wires 200 ells in length and killed small birds. Dr. Ludolf of Berlin, in the year 1744, kindled by electricity the ethereal spirit of Frobenius, by the excited glass tube; the spark proceeding from an iron conductor. Mr. Boze fired gunpowder by electricity. Mr. Gordon contrived the electrical star. Mr. Winckler contrived a wheel to move by the agency of the same fluid. Mr. Boze conveyed electricity from one man to another by a jet of water, when both were placed upon cakes of rosin, six paces apart. Mr. Gordon fired spirits, by a jet of water; and the Germans invented the electrical bells.
Mr. Collinson in 1745 sent to the Library Company of Philadelphia, an account of these experiments, together with a tube, and directions how to use it. Franklin, with some of his friends, immediately engaged in a course of experiments, the results of which are well known. He was enabled to make a number of important discoveries, and to propose theories to account for various phenomena, which have been universally adopted, and which bid fair to endure for ages.
In the year 1745, such was the attention given to the subject of electricity, that experiments upon it were publicly advertised and exhibited for money in Germany and Holland. Dr. Miles, of England, in the same year fired phosphorus by the application of the excited tube itself without the intervention of a conductor. It was at this period that Dr. Watson’s attention was given to this subject. He fired air, made inflammable by a chemical process, and discharged a musket by the electric fluid. He made many experiments, some of which will be described as we proceed.
The year 1745 was made famous by the discovery of the Leyden Phial by Mr. Cuneus a native of Leyden. It appears also to have been discovered by Mr. Von Kleist, dean of the Cathedral in Camin about the same time. By this discovery, electricity could be accumulated and severe shocks given. Mr. Gralath, in 1746, gave a shock to twenty persons at once, and at a considerable distance from the machine. He constructed the electrical battery by charging several phials at once. Mr. Winckler, and also M. Monnier, in France, transmitted the electric fluid through several feet of water as a part of the circuit. M. Nollet, in France, killed birds and fishes by the discharge of the Leyden jars. Improvements were made by Dr. Watson, and others, in the Leyden phial, by coating the inside and outside of it with tin foil. Abbé Nollet gave a shock to 180 of the guards in the king’s presence; and at the grand convent of the Carthusians in Paris, the whole community formed a line of 3600 feet in length, by means of wires between them. The whole company upon the discharge of the phial, gave a sudden spring at the same instant. The French philosophers tried the same experiment through a circuit of persons, holding wires between them, two and a half miles in length. In another experiment the water of the basin in the Tuilleries was made a part of the circuit.
M. Monnier, the younger, to discover the velocity of electricity, discharged the Leyden phial through an iron wire 4000 feet in length, and another 1319 feet, but could not discover the time required for its passage. Dr. Franklin communicated his observations, in a series of letters, to his friend Collinson, the first of which is dated March 28, 1747. In these he shows the power of points in drawing and throwing off the electrical matter. He also made the grand discovery of a plus and minus, or of a positive and negative state of electricity. Shortly after Franklin, from his principles of plus and minus state, explained, in a satisfactory manner, the phenomena of the Leyden phial. Dr. Watson and others in July 18, 1747, conveyed the electric fluid across the Thames at Westminster bridge; the width of the river making a part of the circuit. On the 24th of July, he tried the experiment of forcing the electric fluid to make a circuit with the bend of the river, at the New River at Stoke, Newington. He supposed that the electric fluid would follow the river alone, through its circuitous windings, and return by the wire. He suspected from the result of this experiment, that the ground also conducted the fluid. On the 28th, he proved the fact by supporting a wire 150 feet in length upon baked sticks, using the ground as half of the circuit. On the 5th, of August, he tried another experiment of making the dry ground a part of the circuit for a mile in extent, and found it to conduct equally as well as water. The last experiment was tried at Shooter’s Hill, on the 14th of August of the same year. But one shower of rain had fallen for the five preceding weeks. The wires, two miles in length, were supported upon baked sticks, and the dry ground was used for the return two miles of the circuit. They found the transmission of the electric fluid to be instantaneous. Dr. Watson made many other experiments which we must pass over.
Mr. Ellicott constructed an electrometer for measuring the quantity of electricity. Mr. Maimbury, at Edinburgh, electrified two myrtle trees, during the month of October, 1746, when they put forth small branches and blossoms sooner than other shrubs of the same kind, which had not been electrified. The same experiment was tried upon seeds, sowed in garden pots with the same success. Mr. Jallabert, Mr. Boze and the Abbé Menon principal of the College of Bueil, at Angers, tried the same experiments upon plants, by electrifying bottles in which they were growing. He proved that electrified plants always grew faster, and had finer stems, leaves and flowers than those which were not electrified.
In the year 1748, Dr. Franklin, and his friends, held an electrical feast[17] on the banks of the Schuylkill near Philadelphia, and as the account is amusing, as well as scientific, we will give an account of it as related by Franklin, in a letter to his friend Collinson, dated Philadelphia, 1748. (1 vol. of Franklin’s Works, p. 202.)