Contribution of Thomas A. Edison to Thermionics Available to Purchase

A brief summary is given of the steps in the development of the thermionic vacuum tube. This leads back to the experiments of various people in the early 1880's, and particularly to the attempts by Thomas A. Edison to find the cause of the blackening of his newly developed incandescent lamps. Edison discovered during this work that substantial electric currents could flow between a hot carbon filament and another electrode across a high vacuum. Along with his contemporaries he wrongly ascribed the current to the flow of molecular ions rather than electrons. He, nevertheless, invented and built devices making use of these currents, the first applications of thermionics. The work received wide publicity at the time. Extracts from Edison's notebooks and other sources serve as illustrations.