The achievements which combined to perfect the tungsten lamp to the point where it has become the mainstay of electric lighting are not attached to names in the Hall of Fame.  Organization of scientific research in the industrial laboratories is such that often many persons contribute to the development of an improvement.  Furthermore, time is usually required for a full perspective of applications of scientific knowledge.  In the early days organized research was not practised and the great developments of those days were the works of individuals.  To-day, even in pure science, some of the greatest contributions are made by industrial laboratories; but sometimes these do not become known to the public for many years.  The whole scheme of scientific development has changed materially.  For example, the story of the development of ductile tungsten, which has revolutionized lighting, is complex and more or less shrouded in secrecy at the present time.  Many men have contributed toward this accomplishment and the public at the present time knows little more than the fact that tungsten filaments, which were brittle yesterday, are now made of ductile tungsten wire drawn into the finest filaments.

The earlier tungsten filaments were made by three rival processes.  By the first, a deposit of tungsten was “flashed” on a fine carbon filament, the latter being eliminated finally by heating in an atmosphere of hydrogen and water-vapor.  By the second, colloidal tungsten was produced by operating an arc between tungsten electrodes under water.  The finely divided tungsten was gathered, partially dried, and squirted through dies to form filaments.  These were then sintered.  The third was the “paste” process already described.  These methods produced fragile filaments, but their luminous efficiency was higher than that of previous ones.  However, in this country ductile tungsten was soon on its way.  An ingot of tungsten is subjected to vigorous swaging until it takes the form of a rod.  This is finally drawn into wire.

Much of this development work was done by the laboratories of the General Electric Company and they were destined to contribute another great improvement.  The blackening of the lamp bulbs was due to the evaporation of tungsten from the filament.  All filaments up to this time had been confined in evacuated bulbs and the low pressure facilitates evaporation, as is well known.  It had long been known that an inert gas in the bulb would reduce the evaporation and remedy other defects; however, under these conditions, there would be a considerable loss of energy through conduction of heat by the gases.  In the vacuum lamp nearly all the electrical energy is converted into radiant energy, which is emitted by the filament and any dissipation of heat is an energy loss.  A high vacuum was one of the chief aims up to this time, but a radical departure was pending.