Frictional electricity may be removed by attaching to the machine a device called a neutralizer, which is really a transformer.

This device may be bolted to the wall or ceiling in any convenient place and serves to deliver the electric current in the proper form to the various machines where the static electricity is to be neutralized. A single line of heavily insulated wire leads from the transformer to the various points of treatment. This line may be run along the ceiling over the machines or under the floor on which the machines are set. On each machine is placed one or more inductors connected to the line wire. The inductor is a steel tube of 1 1/2 in. outside diameter and of suitable length to reach across the machines. This tube is also slotted on one side from end to end and has a series of porcelain blocks in the slot. These blocks contain the active points from which the influence is radiated to the charged material. The tube itself is grounded, but the line wire is connected directly with the cable inside of the tube. The connection is made through a convenient form of removable socket at the end of each inductor. The inductor is placed at some point in the machine where the charged material may pass by it at a distance of from 1 to 3 in., and the material becomes instantly neutralized thereby, even when running at a speed of 1000 ft. per minute. On a printing press, the inductor is placed across the press so as to treat the paper just after it leaves the cylinder or at least before it goes into the pile.

Fig. 82. Leyden Jar.

Fig. 82. Leyden Jar.

Electricity may be detected in some substances, such as cotton, glass, and wool, better than in a metal like silver, because the first-named substances are non-conductors and do not allow the electricity to escape easily while the reverse is true in the case of conductors. Moist air is a far better conductor than dry air; hence, electricity shows itself on cotton when the air is dried. In order to keep the air moist, humidifiers (apparatus for discharging moisture in the air) are distributed throughout cotton mills.