PART I

FIRST PHASE OF ELECTROMOTORS.

CHAPTER I.

HISTORICAL SUMMARY.

To whom belongs the honour of having first applied electricity to work a mechanical motor? This is a question which it is very difficult to answer correctly. From the electric whirligigs constructed to demonstrate the action of the electric fluid, either by its flow from points, like the whirligigs worked by static electricity, or by the effect of successive attractions, as in Zamboni's dry pile tourniquet, many scientists have endeavoured to utilise in some such way the dynamic actions of currents; especially when the powerful force of magnetisation developed by these currents was learnt. If we may believe the story given in the Electrician' of Sept. 9th, 1882, Dr. Schulthess promulgated the first idea in a lecture at the Society of Engineers of Zurich in 1832, in which he asked "if a force, such as we obtain by interrupting the current and establishing it again,

could not be advantageously applied to mechanics." This idea must have borne fruit, for in January of 1833 he brought before the notice of the same Zurich society a machine, in which the principle enunciated by him was successfully applied. In November, 1832, Salvator dal Negro, Professor of Natural Philosophy at the University of Padua, also published an account of means employed by him to apply electro-magnetism to the motion of machines. Also in 1834, Professor Jacobi, well-known to the scientific and industrial world by his discovery of electro-plating, published the arrangement of an electro-magnetic motor which, afterwards tried on a larger scale, enabled him to accomplish on the Neva those grand feats which created so much wonder in 1838. The following is what he said in the account he published of his experiments: "I had the honour, in 1834, to present to the Académie des Sciences of Paris, a paper on a new electro-magnetic apparatus. This paper was read at the meeting of December 1st, and an extract was printed in 'L'Institut' of December 3rd, 1834.* Since that time Botto and dal

*The following is the extract referred to:-"M. Jacobi, of Koenigsberg, presented to the Académie a paper on a magnetic engine of his invention, in which magnetism is employed as a motive power. The following is the description he gives of it: The apparatus consists of two systems of eight bars of soft iron, 7 in. long and 1 in. in diameter. These two systems are placed at right angles, and so arranged on two discs that the ends or poles of the bars are opposite one another. One of these discs is fixed, while the other revolves on its axis, and the movable bars are thus made to pass as close as possible before the fixed ones. The sixteen bars are wound with 320 ft. of copper wire, 1 line in diameter, and the ends were in contact with a voltaic apparatus. The whole mass,

Negro have claimed priority of invention, and my ideas coinciding with those of such distinguished men forms a further proof of the importance of this new motive power."

After his first experiments Jacobi continued his researches, and in 1838, with funds provided him by the Emperor of Russia, he constructed a large machine which we will describe further on, and undermoving with a speed of 6 ft. per second, gives about 50 lbs., being a considerable vis viva. The work thus furnished, measured by an apparatus similar to the Prouy brake, is equal to a weight of 10 or 12 lbs. lifted 1 ft. per second. This success is principally due to a novel construction of the commutator, by which are worked the changes of polarity, which take place eight times in each complete revolution; that is to say, eight times in half or three quarters of a second, the ordinary speed of the machine, when the water in the cell is so little acidulated that the development of gas is hardly appreciable."

* The following is the description of Botto's motor, as published in the Institut of December 3, 1834, p. 400:-"The mechanism of which he makes use consists in the first place of a lever worked, like that of a metronome, by the alternate action of two fixed electromagnetic cylinders acting on a third movable cylinder attached to the lower arm of the lever. The upper arm imparts a continuous circular movement to a metal fly-wheel in the ordinary manner. The apparatus is so arranged that, the axes of the three equal cylinders being in the same vertical plane perpendicular to the axis of movement, the oscillating cylinder places alternately each of its extremities in contact with one or other of the two cylinders placed on each side of it; and each time at that instant the direction of the magnetising current in the helix is changed, the rest of the circuit maintaining the same direction, so that poles of the same name are produced in the fixed magnets and the movable one. The change of direction is worked by means of a lever operated by the movement of the machine itself. In consequence of this arrangement the movable cylinder undergoes simultaneous alternate attraction and repulsion, whereby the apparatus sets itself in motion, which motion is maintained by the magnetic force of the electric current."

took his great experiment of electric navigation. The boat employed by him was a ten-oared rowingboat, fitted with paddle-wheels rotated by his electromagnetic machine, shown in Fig. 31. The boat generally carried ten or twelve people, and the runs sometimes lasted the whole day. However, the difficulties that he met with in the electric generator and the imperfections in the construction of the motor often caused break-downs which it was difficult to remedy on the spot. However, when they were overcome, Jacobi was able to estimate the work produced, and he showed that a battery of platinum plates of 20 square feet surface could, by this means, be made to develop one horse-power; but he always hoped to obtain the same result with half this battery surface. The boat, according to report, went about four miles an hour, being a better result than that obtained at the first trials of small steam-boats. According to Jacobi, the boat was 28 feet in length, 7 feet 6 inches in beam, with a draught of water of 2 feet 9 inches. At the experiments in 1859, the machine, which occupied a small space, was worked by a battery of 64 platinum cells, each having 36 square inches of surface, and charged on the Grove system with nitric acid and acidulated water. When the boat, with twelve or fourteen people on board, went against stream, she could make three miles an hour. If we compare these results with those obtained in 1838, it will be seen that already great progress had been accomplished, for in the first trials it was necessary to use a battery nearly

five times as large. These details were mentioned in a letter written by Professor Jacobi to Faraday on June 21st, 1839, which may be read in the 'London and Edinburgh Philosophical Journal' of September, 1839.

The publication of this letter brought out a letter from Professor Forbes, of King's College, Aberdeen, to Dr. Faraday, dated October 7th, 1839, in which, wishing to obtain the honour for his own country, he gave the detailed account of the experiments undertaken in the same direction by Mr. Robert Davidson, an inhabitant of Aberdeen.

According to this letter, it appeared that at the time of Jacobi's experiments, i. e. in 1839, this Robert Davidson had a lathe and a small locomotive capable of being worked by electricity. His carriage, when running on rough planks, was able to carry two people, and it was said that it could easily be proved that the work at these machines had been in hand two years before the date in question. However that may be, it appeared that Davidson had not confined himself to the invention of his motor; he had also brought out several improvements in Daniell .batteries for their application to electromotors, and he had determined the best kind of iron for this sort of application. Although Forbes at this time was in communication with the authorities of the railway companies to obtain from them for Mr. Davidson, pecuniary assistance in his very important and costly experiments, it was he who in the first instance defrayed all the expenses, and he was able to show