Tesla's Inductive Lights

In his experiments before the American Institute of Electrical Engineers, Mr. Tesla used a machine having 400 poles, and giving, at full speed, 20,000 alternations per second. He believes that electro-magnetic waves cannot produce luminous effects unless they have the frequency of true light waves, although electrostatic waves or thrusts excite luminous radiation at any frequency. He exhibited a lamp with a filament consisting of a single rod, to which the energy was transferred entirely by condenser action through the coatings in the base of the lamp. He also showed how exhausted tubes can be made to glow in an electrostatic field, so that if such tubes are merely hung up in a room in such a field, they will be lighted up, and can be moved about at will.