Cassie leaned forward on the wagon seat, squinting anxiously into the incandescent sunrise.
If a loop of very fine platinum wire, prepared by the Wollaston process, is included in an exhausted glass bulb like an incandescent lamp, then when electric oscillations are sent through it its resistance is increased.
Fleming invented in 1904 a detector called an oscillation valve or glow lamp detector made as follows: 1 A small carbon filament incandescent lamp has a platinum plate or cylinder placed in it surrounding or close to the filament.
Fleming discovered that if the filament is made incandescent by the current from an insulated battery there is a unilateral conductivity of the rarefied gas between the hot filament and the metal plate, such that if the negative terminal of the filament is connected outside the lamp through a coil in which electric oscillations are created with the platinum plate, only one half of the oscillations are permitted to pass, viz., those which carry negative electricity from the hot filament to the cooled plate through the vacuous space.
This phenomenon is connected with the fact that incandescent bodies, especially in rarefied gases, throw off or emit electrons or gaseous negative ions.