Page:Motors and motor-driving (1902).djvu/194

162 removable plug is fitted to complete and break the circuit, should be looked at. If it should be very rainy weather, a drop of water may possibly get between the contacts, which are seen held apart when the plug is in place, and so complete the short circuit arranged to take place only when the plug is removed. This can be dried, or a drop of oil as an insulator squirted in between the contacts.

If at starting, one or even two cylinders can be heard missing fire, a few revolutions at a good speed will generally set them going again: if not, it may be necessary to remove and examine the ignition plugs of the defaulters.

The magnetic ignition has been found to work extremely well; and to give very little trouble, if these points are attended to. The magneto machine itself seems, and is, inexhaustible; and the space otherwise required for batteries and cells is all saved. It also gives a fine 'fat' spark, which adds to the efficiency of the explosion. It probably gives a little more noise, if the motor-car is standing still and the engine running very slow on the throttle valves, owing to the firing being always so much advanced; but many of these engines have now the ordinary hit and miss exhaust governor as well, so that the throttles need not be closed so much, and a higher speed allowed. It is, after all, a question of which kind of noise is preferred.

The button on the steering-wheel is arranged to produce a short circuit when pressed, and so stop the firing of the charges in the cylinders. This system in practice is in many ways a great convenience. It can be used in many cases instead of the clutch, and with much less labour, always remembering that the car must not be brought to a standstill by the button, or the motor is stopped. As a brake downhill, it may be used as a slight, or if the gear be on the lower speeds, as a strong compressing brake, and without heating anything; or on a long hill, the engine may be unclutched and stopped altogether and only restarted at the bottom by letting the clutch gently in again. This is not important