The Frame of the machine is composed of two strips twenty-five inches long, three inches wide, and an inch and one-half in thickness, and two cross-pieces of the same thickness and width fifteen inches long. [Illustration: Fig. 37.—The Frame.] Notches are cut at both sides of the base to admit the feet of the uprights. *The Uprights* are seventeen inches long, three inches wide, and one and one-half inches thick. [Illustration: Fig. 38.—The Upright.] The notch at the foot is cut the same width as the thickness of the long members of the frame and is arranged so that when fitted in place, the foot of the upright will rest on the table in line with the bottom of the cross-pieces. *The Driving-Wheels* are turned out of wood on a lathe. They are seven inches in diameter and seven-eighths of an inch thick. A groove should be turned in the edge to carry a small round leather belt. The wheels are mounted on a wooden axle made from a round curtain-pole. They are glued to the axle and arranged so that the grooves will fall directly underneath the pulleys turned in the bosses. [Illustration: Fig. 39.—The Driving-Wheels and Axle.] The ends of the axle pass through the uprights, five inches above the bottom. The front end of the axle is fitted with a crank and a handle. [Illustration: Fig. 40—The Boss and Axle. For sake of clearness, the Plate is not shown.] The plates are mounted on short iron axles passing through the top of the upright into the brass bushings. One end of each of the axles is filed flat where it passes through the wood upright so that it may be firmly held by a set-screw and prevented from revolving. Fasten a small fiber washer to the center of one glass disk so that it will separate the plates and prevent them from touching when revolving. The collectors, quadrant rods, etc., are mounted on glass rods one inch in diameter. The bottoms of the rods fit in holes (_H H_) bored in the cross-pieces of the base, Figure 37. The upper ends are each fitted with a brass ball two inches in diameter. The balls are mounted on the rods by soldering a piece of brass tubing to the ball and slipping it over the rod. The rods should be of the proper length to bring the center of the balls on a line with the center of the plates. [Illustration: Fig. 41—Showing how the Ball, Comb, etc., are mounted on the Glass Rod.] Make two forks as shown in Figure 42 out of brass rod, three-sixteenths of an inch in diameter and solder brass balls at the ends. The forks are eleven inches long. A number of small holes must be bored in the "prongs" and pins made by cutting ordinary dressmakers’ pins in half and soldering them in place. These pins, mounted on the forks, form the combs or collectors. Bore a horizontal hole through each of the brass rods on the top of the glass rods and pass the shanks of the forks through and solder them in place.