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through the bulb, a much higher potential is needed if a conductor, especially of much surface, be present.
For the sake of clearness of some of the remarks before made, I must now refer to Figs. 18, 19 and 20, which illustrate various arrangements with a type of bulb most generally used.
Fig. 18.—Bulb with Mica Tube and Aluminium Screen.
Fig. 19.—Improved Bulb with Socket And Screen.
Fig. 18 is a section through a spherical bulb L, with the glass stem s, containing the leading-in wire w, which has a lamp filament l fastened to it, serving to support the refractory button m in the centre. M is a sheet of thin
