International Library of Technology · Scranton, International Textbook Co. · leaf 207
§16 ELECTRIC LIGHTING. 9 … plunger in conjunction with valves, are not capable of pro-ducing a sufficiently high degree of exhaustion. They are,however, used to exhaust the greater part of the air, andthe final exhaustion is then accomplished either by meansof a mercurial air pump orby the chemical method. The principle of…
Electrical engineering
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