The other end of each is provided with a small insulating handle. A No. 8003 Electrose Knob is just the thing. These knobs are provided with a threaded bushing so that they may be screwed onto the rod. The proper position for the discharge rods is shown in Figure 1. By sliding the rods back and forth in the balls on the ends of the collectors, the distance between the balls on the ends of the rods may be varied. The spark discharge from the machine, when the latter is completed, takes place between these balls. The machine still remains to be fitted with the "neutralizers" and a set of Leyden jars. *The Neutralizers* are illustrated in Figure 14. Two are required. They consist of a piece of one-eighth inch brass rod, six inches long, having the ends bent over at right angles so as to form a shallow U. The distance between the ends when bent should be about three and five-eights inches. A tuft of tinsel should be soldered to the ends of each of the neutralizers. [Illustration: FIG. 10.—The Collector with the Discharge Rods, etc, in position. A is the Brass Ball forming one terminal of the gap across which the sparks jump. B is another Brass Ball screwed onto the end of the Collector Rod and having a hole in it, through which the Discharge Rod slips. CC are two threaded Washers used to clamp the Discharge Rod in place.] Each neutralizer rod is supported by a hard rubber washer three-quarters of an inch in diameter and five-sixteenths of an inch thick. In the centre of the washer a hole should be drilled, which will fit snugly onto the rods upon which the plates are mounted and revolve. The neutralizer rod passes through a hole in the upper part of the washer as shown in the illustration. Before the neutralizers can be put into position it will be necessary to pull out the rods which support the plates so that the plates can be removed. The hard rubber washers supporting the neutralizers are then slipped over the rods so that one will come between each support and plate when the latter is put back into position. The rods should be turned so that the tinsel tufts touch the sectors. The rubber washers should fit snugly on the rods so that the neutralizer will stay in any position in which it is placed. The proper position for the front neutralizer is a little less than half way between vertical and horizontal as shown in Figure 1. The neutralizer behind the rear plate should be at right angles to that in front. [Illustration: FIG. 11.—Showing how Binding Posts may be substituted for Round Balls on the Collector Rods.]