_Siemens' Patent Electric Lamp._--The lamp here described is actuated without clockwork; it also automatically separates the carbons after they have approached too closely or touch, and, by this combined action of approaching and separating, the carbon points are kept at a proper distance apart, and a steady light is obtained. The working parts are represented in the diagram Fig. 169, and at Fig. 170 is shown the size employed on board ship. _E_ is the horse-shoe magnet with the armature _A_ placed in front of its poles a short distance from them. A regulating screw _b_ with the spiral spring _f_ is attached to the lever _A'_, forcing it against the stop _d_, and withdrawing the armature from the poles of the electro-magnet. When a current traverses the coils of the latter of sufficient strength to attract the armature and overcome the tension of the spring _f_, contact is made at _c_, which diverts the current from those coils. The consequent release of the armature breaks contact at _c_, the armature is again attracted, and this action is repeated, producing a vibrating motion of the lever and armature, which continues as long as there is sufficient current to overcome the tension of the spring. [Illustration: Fig. 169.] The spring pawl _s_ at the upper end of the lever _A'_, and oscillating with it, actuates a ratchet-wheel _u_, which is in gear with a train of wheels and the carbon holders; it thus opposes their tendency to approach by pushing them apart, tooth by tooth, until the current is so much weakened by the increased length of electric arc that the armature and lever cease to oscillate enough to move the teeth of the ratchet-wheel, and it rests near the stop _d_. While in this position the spring pawl is released from the ratchet-wheel and the preponderating weight of the upper carbon holder causes the carbon points to approach again. Increase of current follows decrease of resistance, the armature again oscillates, and this cycle of action is continuously repeated. When in action the movements of the carbons are scarcely perceptible, but when, by any external cause, the carbons are separated so as to extinguish the light, they immediately run together until they touch, when they ignite and separate to a proper working distance by means of the electro-magnet above described. The only operation requiring attention in the use of this lamp is the adjustment of the tension of the spring _f_. When this tension is once regulated to the current at disposal, the lamp will continue to give a steady light as long as the current remains uniform. The relative rate of consumption of the two carbon points differs. The positive carbon burns away rather more than twice as quickly as the negative carbon. [Illustration: Fig. 170.] The duration of the light depends mainly on the lengths and sizes of the carbons.