109. The multiple, or series, system of gas lighting is used in large halls where many lights are installed in groups. A fixed spark gap is used at each burner, both of the points being insulated from each other and from the gas pipe, except the last point of a series, which is grounded. The style of burner used is shown in Fig. 87, in which a and b are the points of the spark gap. To complete the connection between consecutive burners, a fine, bare copper wire, about No. 26 gauge, is stretched across, being secured through the small holes at the lower ends of the strips a, b. The body of the burner is made of some insulating substance, and a flange of mica m is added to give further protection. Since one circuit may consist of a large number of burners, it will be seen that the E. M. F. must be very high to force a current across so much air space, and to insure success, the wiring must be installed with the greatest precautions. The wire should nowhere be nearer to the gas pipe than 1 1/4 inches; if, however, it is necessary to approach more closely, the wire should be inclosed in glass tubing.

Apparatus For Multiple Lighting System 540

Fig. 87.

Apparatus For Multiple Lighting System 541

Fig. 88.

The apparatus required for this system of gas lighting consists of an induction coil i, Fig. 88, operated by a battery B, and used with a condenser c across the spark gap of the primary p. The condenser cuts down the spark at the circuit-breaker, for this spark would be very destructive in the case of a large coil. The fine-wire secondary s is grounded at G, and the other terminal is connected to the line wire l passing to the burners.

110. Frictional machines are also used in the multiple-lighting system, and generate static electricity, such as is produced when a rubber comb is passed through the hair. One form of this machine is shown in Fig. 89. One of the terminals l is to be connected to the switch handle s, and the other g to ground. The machine is rotated by means of the handle h, and the switch is moved from one contact to the next, lighting the gas on each circuit 1, 2, 3, 4 in rapid succession.

Apparatus For Multiple Lighting System 542

Fig. 89.