inlet, controllable by the driver, is generally added, unless the carburetter be of a type which automatically maintains constant proportions of air and vapour. The jet chamber is often surrounded by a jacket, through which part of the hot exhaust gases circulate. In cold weather especially this is a valuable aid to vaporization.
IGNITION OF THE CHARGE.
All petrol-cars now use electrical ignition. There are two main systems—(1) by an accumulator and induction