Thomas Edison and others considered element number 6, carbon, ideal for lamp filaments in part because it has the highest melting point of any element. Element number 74, tungsten, has the next highest melting point but it then existed only as a powder. Attempts to make it into a workable form failed until early in the 1900s when a burst of invention occurred in Europe. A pressing technique called "sintering" (squeezing a material into a dense mass) was adopted by several inventors.
The most commercially successful design proved to be that of Dr. Alexander Just and Franz Hanaman of Austria. Their work on sintering tungsten was based on a prior sintering process developed by Carl Auer von Welsbach for his filament made of osmium. Just and Hanaman made a tungsten and organic paste, squirted it through a die, baked out the organic material, then sintered the tungsten in a mix of gasses. The resulting filament gave about 8 lumens per watt and lasted 800 hours.
Another Austrian, Dr. Hans Kutzel, used an electric arc to make a tungsten and water paste. He then pressed, baked, and sintered the tungsten in a manner similar to Just and Hanaman's procedure. Yet another pair of Austrians, Fritz Blau and Hermann Remane, adapted the osmium lamp process (they worked for Welsbach) by making a filament from an osmium and tungsten mix. They soon changed their "Osram" lamp filament to tungsten only. (The German word for tungsten is wolfram.)
All three filaments were brittle and collectively known as "non-ductile" filaments. Individual filaments could not be made long enough to give the proper electrical resistance, so lamps needed several filaments connected end-to-end. U.S. companies quickly licensed rights to all of the non-ductile patents. This particular lamp was made under license by General Electric and sent to the National Bureau of Standards for use as a standard lamp.
Lamp characteristics: Medium-screw base with glass insulator. Five single-arch tungsten filaments (in series) with 5 upper and 8 lower support hooks. The stem assembly features soldered connectors, Siemens-type press seal, and a cotton insulator. Tipped, straight-sided envelope with taper at neck.
Irving Langmuir received a Ph.D. in physical chemistry in 1906 from the University of Göttingen. He studied under Walther Nernst, who had invented a new type of incandescent lamp only a few years before. In 1909 Langmuir accepted a position at the General Electric Research Laboratory in Schenectady, New York. Ironically, he soon invented a lamp that made Nernst's lamp (and others) obsolete.
Langmuir experimented with the bendable tungsten wire developed by his colleague William Coolidge. He wanted to find a way to keep tungsten lamps from "blackening" or growing dim as the inside of the bulb became coated with tungsten evaporated from the filament. Though he did not solve this problem, he did create a coiled-tungsten filament mounted in a gas-filled lamp—a design still used today.
Up to that time all the air and other gasses were removed from lamps so the filaments could operate in a vacuum. Langmuir found that by putting nitrogen into a lamp, he could slow the evaporation of tungsten from the filament. He then found that thin filaments radiated heat faster than thick filaments, but the same thin filament–wound into a coil–radiated heat as if it were a solid rod the diameter of the coil. By 1913 Langmuir had gas–filled lamps that gave 12 to 20 lumens per watt (lpw), while Coolidge's vacuum lamps gave about 10 lpw.
During the 1910s GE began phasing-in Langmuir's third generation tungsten lamps, calling them "Mazda C" lamps. Although today's lamps are different in detail (for example, argon is used rather than nitrogen), the basic concept is still the same. The lamp seen here was sent to the National Bureau of Standards in the mid 1920s for use as a standard lamp.
Lamp characteristics: Brass medium-screw base with skirt and glass insulator. Two tungsten filaments (both are C9 configuration, mounted in parallel) with 6 support hooks and a support attaching each lead to the stem. The stem assembly includes welded connectors, angled-dumet leads, and a mica heat-shield attached to the leads above the press. The shield clips are welded to the press. Lamp is filled with nitrogen gas. Tipless, G-shaped envelope with neck.
The original device, consisting of an electromagnet arranged to ring a bell, was demonstrated in 1831 by Joseph Henry to his classes at the Albany Academy in Albany, N. Y. By closing a circuit, Henry energized the electromagnet with current from a battery. The magnet attracted a lever arm that rang the bell. This demonstrated electrical action at a distance and laid the foundation for later telegraph devices. This replica was made for the museum in 1897 by John Schultzbach.
Model of Joseph Henry's electromagnetic motor of 1837. A straight electromagnet is mounted horizontally and supported on knife edges at its center. A permanent bar magnet is placed below the electromagnet. A double set of terminals is provided for the electromagnet coil, one pair at each end of the horizontal bar. A battery was placed under each set of terminals. An arrangement for reversing the flow of current as each terminal pair dipped into a battery, established the principle of commutation. Reference: MacLaren, Rise of the Electrical Industry in the 19th Century, pages 21-22.
The original device, consisting of an electromagnet arranged to ring a bell, was demonstrated in 1831 by Joseph Henry to his classes at the Albany Academy in Albany, N. Y. By closing a circuit, Henry energized the electromagnet with current from a battery. The magnet attracted a lever arm that rang the bell. This demonstrated electrical action at a distance and laid the foundation for later telegraph devices. This replica was made for the museum in 1897 by John Schultzbach.
Telegraph keys are electrical on-off switches used to send messages in Morse code. The message travels as a series of electrical pulses through a wire. The operator pushes the key’s lever down briefly to make a short signal, a dot, or holds the lever down for a moment to make a slightly longer signal, a dash. The sequence of dots and dashes represent letters and numbers. This is a replica of an early type of lever key used by Samuel Morse and Alfred Vail.
Alfred Vail made this key, believed to be from the first Baltimore-Washington telegraph line, as an improvement on Samuel Morse's original transmitter. Vail helped Morse develop a practical system for sending and receiving coded electrical signals over a wire, which was successfully demonstrated in 1844.
Morse's telegraph marked the arrival of instant long-distance communication in America. The revolutionary technology excited the public imagination, inspiring predictions that the telegraph would bring about economic prosperity, national unity, and even world peace.
Marked: "Signal Corps U.S. Army / Test Set Type 1-52 / Designed at Radio Laboratories / Fort Monmouth, New Jersey / Order No. W-457-SC-740 / Date 5/31/28 / Serial No. 89 / Made by: / National Electric Supply Co. / Washington, D.C." Hinged top cover missing from specimen. Unit is a mutual conductance tube checker with a 3 ma. DC meter. Tubes checked are WD-12 and VT-5 types. Controls include grid current and mutual conductance tests with a scale setting to 500 microhoms. A filament rheostat regulates filament current, and binding posts are provided for plate voltages of 45 and 67 volts, also filament potential of 6 volts. Meter unit is a model 301 Weston.
Name Plate: "Radio Detector / Type S.E.183B / Serial No. 141N / Made for Navy Dept. (BU.S.E.) / By / Nat. Elec. Sup. Co. / Wash. D.C. 1920". A three turret crystal detector with a 4-position sweep switch, two connecting screws. Switch taps marked: "1", "2", "3", and "Off". Left turret ("1") has a short pointed contact and an empty crystal holder. Center turret ("2") has a pointed contact, crystal holder missing. Right turret ("3") has a Cat's Whisker holder (whisker missing) and an empty crystal holder. Slate base. metal; plastic.
