Saturation of Coil

—In gas engine ignition, an interval of time is required to saturate the coil, make the break and discharge the core, producing the jump spark. The average duration of these operations is about.005 second, which, although quite negligible at low speeds, requires progre ive advances of the time as speed increases, The movement of the vibrator also consumes a fraction of a second, its speed being indicated by the pitch of its buzz, but unle the speed be very high, the time for occurrence of the spark is changed. If the vibrator be leaving contact with the core at the moment of cireuit-making in the commutator, the time of one vibration must elapse before the occurrence of the spark; if the vibrator be in contact at this moment, the spark follows almost immediately. In a multiple-cylinder engine using a separate coil for each cylinder, unle the vibrators be tuned as nearly as po ible to the same pitch or rate of vibration, the sparks will occur at different points of the several respective piston strokes.