Abstract :
OF all the possibilities which beckon the scientist outside the narrow range of pressure and temperature in which we live, none has shown more alluring results than the family of vacuum or low-gas-pressure tubes. Incandescent lamps, X-rays, mercury rectifiers, radio tubes, photoelectric devices, and hyper-sensitive relays are among the substantial things which have already been summoned forth from the nothingness left by the vacuum pump. Other very practical developments are following; nowadays tangible results follow close upon the heels of theory.
