. Locomotive text for engineers and firemen; a complete treatise on the engine, electric head-light and standard code of train rules . he lamp returns to thearmature, but its pressure or voltage is dissipated inthe arc produced at the lamp. If this were not the case,and if the carbon were held on the point of the elec-trode when the dynamo is in operation, the effect on theturbine would be similar to that which would be pro-duced in the cylinder of a locomotive, if the steam afterdriving the piston to one end of the cylinder were un-able to escape to the atmosphere. This might be called a shor
. Locomotive text for engineers and firemen; a complete treatise on the engine, electric head-light and standard code of train rules . he lamp returns to thearmature, but its pressure or voltage is dissipated inthe arc produced at the lamp. If this were not the case,and if the carbon were held on the point of the elec-trode when the dynamo is in operation, the effect on theturbine would be similar to that which would be pro-duced in the cylinder of a locomotive, if the steam afterdriving the piston to one end of the cylinder were un-able to escape to the atmosphere. This might be called a short circuit through the lamp,as there would be no resistance offered to the flow ofcurrent. The circuit would be closed and the. pressureor voltage could not be dissipated. 3i8 THE ELECTRIC HEADLIGHT. If the dynamo were run in this manner for any lengthof time the coils would become hot enough to char theinsulation of the wires, and the current would leakthrough from layer to layer, producing what is called aburned out armature. To form the arc and so produce the light, the carbonsmust be pulled apart a short distance. This is ac-. PLATE 139. complished by means of solenoid 65, the coil on the an electric current flows through a coil ofwire, this coil becomes an electromagnet. The solenoidis an electromagnet, and provides the automatic mechan-ism, which feeds the carbon down as fast as it is con-sumed and maintains the arc at the proper length. The THE ELECTRIC HEADLIGHT. 319 mechanism becomes weaker as the length of the arc in-creases, and when the arc reaches a certain length themagnet becomes weak enough to release the clutch,which allows the carbon to drop, through gravity, to-ward the electrode. Before the carbon can drop to theelectrode the magnet is strengthened and the downwardmotion of the carbon is arrested. ■ ■ ^ sSB w?**w • 1 _-:..;::— 1 M . *«,*- N PLATE 140. When the dynamo is stopped for any considerablelength of time, the small particles of carb
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