The first part of this paper is occupied by a description of two forms of constructing the magnetic electrical machine, which the author has adopted ; and the second, with the particulars of some experiments made with a view to determine the respective powers of these machines as compared with the common voltaic battery. In the first form of the instrument, a reel, round the periphery of which 200 feet of copper wire, one 20th of an inch in diameter and covered with stout sewing-silk, are coiled, is made to revolve on a spindle, placed in the axis of a system of horse-shoe magnets, so as to remain within the branches of the latter during its whole revolution. The electric currents produced in the copper wire by magnetic induction, while the coil is moved at right angles to the plane of the magnets, are conducted by means of four semicircular metallic flanges attached to the spindle, into cisterns of mercury, the one being positive, and the other negative; and which consequently act as the two poles of the battery. In the second form of the apparatus, a piece of soft iron, of which the ends are bent into the shape of two arms, and which is surrounded with a coil of 300 feet of copper wire, is made to revolve in front of the poles of a horse shoe magnet; its axis of motion coinciding with that of the magnet; and the electrical currents determined in the wire by this rotation, being collected in the same manner as in the former instrument. The author next details several series of experiments which he made for the purpose of ascertaining the relation observable between different velocities of rotation in these instruments and the corresponding effects: first, with regard to the deflection of a magnetic galvanometer ; secondly, with regard to chemical decompositions; thirdly, with regard to the production of sparks; and lastly, with regard to the intensity of the shock communicated to the human body. He compares the effects produced by the magnetic electrical battery, first, when the coil consisted of one continuous length of wire ; secondly, when the coil was doubled upon itself so as to constitute two sets of conductors of half the length of the former ; thirdly, when, upon being again doubled, it composed four conductors of one quarter of the length of the first; and lastly, when, on being doubled a third time, the electric current was made to pass through eight wires, each one eighth of the original length of the single wire. It was found that by thus multiplying the channels of conduction, although both the magnetic and the luminous effects continue to be produced with scarcely any sensible difference of intensity, the power of effecting chemical decompositions becomes more and more impaired, and the physiological influence is weakened in a still more remarkable degree. In the four-stranded coil, in deed, no shock whatever could be produced, however rapidly the instrument was made to revolve. The author endeavours to account for these variations of effect by the diminution of velocity in the electric current, its quantity remaining unaltered, consequent on its division into several streams by the multiplied channels offered to its progress. He also tried the effects of conjoining the magnetic electrical machine with ordinary voltaic combinations; sometimes acting in cooperation, and at other times in opposition to one an other; and notices the corresponding results, which were sufficiently accordant with theory.
A Feasibility Study of Heat Pipes for Thermal Management of Electrical Machines
