St. John, Thomas M. (Thomas Matthew), b. 1865 · New York, T. M. St. John · leaf 135
Fig. igS. pumped from the bulb or globe. This is donewith someform of mercury pump, and the air is so thoroughljre-moved from the bulb that about one-millionth only of the 132 LIGHT PKODUCKU BY INCANDESCENT LAMP. … Fig. 199. original air remains. Before sealing off the lamp, a cur-rent is passed through the filament to drive out absorbedair and gases, and these are carriedaway b} the pump. By proper treat-ment the filaments have a uniformresistance throughout, and glow uni-formly when the current passes. 150.…
Electricity
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