_Starting and stopping._—Starting is an operation requiring a little practice. First of all the igniting burner must be lit, and time allowed for it to red-heat the ignition-tube; if electricity is used this wait of a few minutes is obviated. The lubricating arrangements are then attended to, so as to make sure of them being in satisfactory working order. If no self-starting arrangement is provided, the supply of gas to the cylinder is partly turned on, and a few quick turns of the fly-wheel by hand are sufficient to set the engine in motion. Having attained the normal speed the gas can be turned full on. If the motor refuses to start, the tap regulating the gas supply should be examined as it may be too full on; the ignition apparatus must then be inspected. Sometimes the reason of the refusal to start lies in the exhaust-valve which leaks; in this case no compression takes place. This can easily be verified by turning the fly-wheel backwards, and seeing whether the piston tends to resist the motion, which it would do if the compression was taking place properly. When running it is a mistake to flood the engine with oil; a barely sufficient quantity of good mineral oil is all that is required. If the valves require cleaning, then of course plenty of oil should be used to wash away the deposit, but they should be well wiped before starting. Many persons have become erroneously imbued with the idea that a gas engine requires a skilled mechanic to attend to it. As a matter of fact any person without previous knowledge is, with a few days’ practice, competent to take charge of a motor provided that he is intelligent and careful. Under these conditions a gas engine will last as long as a steam engine, and will be generally found much more satisfactory.