Electricity in the Service of Man by Alfred Urbanitzky, Richard Wormell 1886 Bohm's Lamp. Bohm constructed his lamp with a view of saving the glass vessel when the carbon had become useless (Fig. 448). r is a tube for exhausting the glass vessel g g. The well-ground stopper has a groove cut in it at c to correspond with the tube r. After the vessel has been exhausted the stopper need only be turned to prevent the air from entering. The wires with the carbon are fused into the portion s s of the stopper. To replace a worn-out carbon filament the stopper is simply taken out, and a new carbon fixed to the wires.