Fig. 46.
[Figure 46], represents a top view of the instrument. A is the case containing the armatures and coils, and H the band wheel. N, S and N, S, are the north and south poles of the permanent magnets. S′ and S′ are the yokes by which the magnets are secured to the platform, and the screws near the poles of the magnets are for the purpose of setting the magnets to any required position, laterally, and securing them in it. M and M are the tops of the two pilliars, which support the shaft of the armatures and coils. The bearings are so made as to allow the apparatus to revolve with as little friction as possible: 3 and 3 represent the set screws against the ends of the shaft, for adjusting the ends of the permanent magnets; by which means, the armatures may be allowed to pass very near the ends of the magnets without touching. 6, 7, 8, and 9 are the receiving studs, by which the wires from any other instrument may be connected with the machine. The wire, a, in contact with the unitrep, as before stated, is continued and soldered to the receiving stud, 6; in the same manner, c, also in contact with the unitrep, is connected with 7; and also 3 with 8; and a with 9. The manner in which these wires, a, c, 3, and a, form their contact with the shaft, is seen at N and P, [figure 45], of which 5 and 5 represent a section of the shaft and unitrep.
Fig. 47.
[Figure 47] represents the revolving armatures and coils, with the case taken off. C and C are the two coils of insulated copper wire, surrounding two straight bars of soft iron, represented in the end view by D and D. E is the shaft. The two armatures and coils are secured to the two brass straps F, which are themselves fastened upon the shaft. The armatures are allowed to project through the straps about the sixteenth of an inch.
On each end of the shaft is attached an unitrep, consisting of two cylindrical segments of silver, as seen at 5 and 5, [figure 45]; insulated from each other, and secured to a cylinder of ivory or wood, upon the shaft, so as to revolve with it. The terminations of the coils of wire upon the armatures, are soldered to the segments of silver, and as the unitrep turns, it brings opposite ends of the wires, alternately, upon the stationary wires or conductors, P and N: (in [figure 46] they are represented by a and c, and 3 and a.) The opposing currents of the coils, in each half revolution, are, by this contrivance, made to form one continuous current. Hence, the name unitrep (to turn together.) There being two unitreps, and corresponding conducting wires, and screw cups, the induced currents from the two coils may be combined in several ways, after the manner of combining separate batteries.
Let the wires below the base board be all properly connected with the receiving cups, as heretofore described. Then let the wire from 6, (represented by dots,) to k, be connected with the wire 9 and m; and also the wire 7 and l, with the wire 8 and 0. Let one of the united wires be connected with one wire leaving the coil of an electro magnet; and the other united wire be joined to the other wire of the electro magnet of the telegraph, or any other instrument designed to operate by a galvanic battery. When this preparation is finished, if the armatures and coils are made to revolve rapidly, a powerful current is formed in the induced coils, C and C, [figure 47], capable of performing all the experiments generally made by means of the galvanic battery.