To reduce the friction between the bosses and the uprights it would be well to place a fibre washer between them. A few drops of oil on these washers will lubricate them properly, and allow the machine to run easier. An end view of the apparatus, as so far assembled, will appear as shown in Fig. 9, A being the disks, bosses, and axles, B B the uprights supporting them, C the hub, and D D the driving-wheels. The handle and crank (E) extends out far enough from the side to allow a free swinging motion without hitting the upright or base. Having arranged these disks and wheels so as to revolve freely, it will now be necessary to construct and add the other vital parts and the connecting links in the chain of the complete working mechanism. From a supply-house obtain two solid glass rods an inch in diameter and fifteen inches long. These fit in the holes (B B) bored in the end-pieces of the base, Fig. 4. Procure two brass balls, two or two and a half inches in diameter, such as come on brass beds, and two short pieces of brass tubing, one inch inside diameter, that will fit over the ends of the rods. These tubings are to be soldered fast to the balls so that both tubes and balls will remain at the top of the glass rods. From brass rod three-sixteenths or a quarter of an inch in diameter make two forks, as shown at Fig. 8, and solder small brass balls at the ends of the rods. The prongs of the fork are six inches long and the shank four inches in length. Along the inside of the forks small holes are bored, and brass wires, or “points,” are soldered fast. These extend out for half an inch from the rods, and are known as the “comb,” or collectors. The forks should be so far apart that when mounted with the glass disks revolving between them the points will not touch or scratch the tin-foil sectors, and yet be as close to them as possible. A hole should be bored in the brass balls, and the shank of the fork passed through and soldered in place, as shown in Fig. 10. A three-eighth-inch hole is bored directly in the top of each brass ball to hold the quadrant rods, which extend over the top of the disks. In the illustration of the complete machine (Fig. 12) the arrangement of the glass pillars, balls, combs, and quadrant rods is shown. The rods are three-eighths of an inch in diameter and are loose in the holes at the top of the balls, so that they can be moved or shifted about, according as to whether it is a left or a right handed person who may be turning the crank.