In Figure 45, representing a side view of the machine, B and B are the compound permanent steel magnets, composed of six bars each of the U form, mounted upon the brass pillars, P, P, P, P, which are fastened into the common platform of the whole machine. Through the platform there pass stout rods, R and R, and upwards through two brass straps, above the magnets, B and B. These straps or yokes secure the magnets from any motion by means of the screw nuts. A is a circular case of pasteboard, containing the armatures and coils. H is a band wheel surrounding the case, for mechanical connection with any source of power that may be used to keep the machine in motion. I′ and I are two metallic studs, with an aperture passing vertically from the top, to the depth of an inch, for the reception of connecting wires, and then, by means of a screw at its side, to make a perfect contact. There are two other studs directly behind them. G and J are the two pulley wheels, with their band and crank, by which a rapid rotary motion is given to the armatures and coils. These pulleys are supported by the standard. From the bottom of the studs I′ and I, as also from those directly behind them, proceed wires which are carried along below the platform, and pass up through it between the pilliar, P, and the revolving armatures, to the shaft; there being one on each side of the axis. [Illustration: FIG. 45.] [Illustration: 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. [Illustration: FIG. 47.]