Peter Cooper Hewitt, American electrical engineer, who invented the mercury-vapour lamp, a great advance in electrical lighting. Peter Cooper Hewitt was the grandson of the famous Peter Cooper, a great American engineer and industrial pioneer. Hewitt inherited his ancestor’s inventive mind. One biographer thus described Hewitt: “Those who knew him, watching him work, felt that a part, at least, of Hewitt’s thinking apparatus was in his hands.”
While Edison and others struggled with incandescent filaments, someinventors approached the concept of making light by using electricaldischarges. Hewitt began developing mercury-filled tubes in the late 1890s for lightening.
His work was based on the mid-19th century work of German physicist Julius Plucher and glassblower Heinrich Geissler. By passing an electric current through a glass tube containing tiny amounts of a gas, Plucker and Geissler found they could make light. Although the seals leaked and soon let in too much air to allow the effect, glowing Geissler Tubes became a scientific novelty.
Hewitt found that electrical current in his mercury-filled tubes gave light. These early mercury lamps had their limitations. The light was blue-green and colours seen under it were distorted. The lamp was also prone to flickering as the arc ‘danced’ on the pool of mercury.
The amount of light, however, was startling. Hewitt refined the lamp, reducing the flicker and claimed a much higher efficacy than that of carbon filament lamps. However, Hewitt realized that few people would want his lamps in their homes, and so concentrated on developing a product for other uses.
Peter Cooper Hewitt wrote in 1902: “When it is considered that this light, when obtained with mercury gas, has an efficiency at least eight times as great as that obtained by an ordinary incandescent lamp, it will be appreciated that it has its use in places where lack of red is not important, for the economy of operation will much more than compensate for the somewhat unnatural color given to illuminated objects.”
One century ago, on September 17, 1901, Peter Cooper Hewitt received a patent for his vapor lamp – an important forerunner of today’s fluorescent lights. He developed a mercury tube that used series-wired carbon filament lamps as the ballast. This converted the resistive byproduct, heat, into light and the resultant configuration was the forerunner of today’s self-ballasted or mercury blended lamp.
Hewitt’s lamps were clumsy by today’s standards. They consisted of a thin glass tube, about a metre long, with an electrode at each end and a bowl at one end. The lamp contained a pool of mercury, enough to make contact with both electrodes when the tube was level.
The lamp operated in a tilted position and was started by levelling it so the mercury touched both electrodes, started the arc inside the tube and then collected in the bowl at one end. As the mercury in the bowl was close to the hot electrode, it gave off vapour, through which the arc was sustained. Later versions of Hewitt lamps had an electrical tilting mechanism rather than a manual system. The lamps needed ballasts in series with them to limit the current to the arc. These were usually resistive devices that gave off a lot of heat, but Hewitt also perfected a solution to this.
Photo studios made extensive use of Cooper Hewitt lamps. In an age ofblack and white film, the color of a photographer’s light made little difference, there just needed to be lots of it. Industrial uses for the lamp were also many. In 1902 the Cooper Hewitt Vapor Lamp Company (backed by the money of George Westinghouse) was established to make and market the lamps.
Ultimately, Cooper Hewitt lamps proved cumbersome to use. The necessary ballast was heavy, and the lamps each contained as much as a pound of mercury.
Development of tungsten filament incandescent lamps in the 1910s provided almost as much efficiency as the mercury tubes, but with a much better color. General Electric bought the Cooper Hewitt Company in 1919, and in 1933 began marketing a new mercury vapor lamp. Designed in Europe, this mercury lamp and the fluorescent lamps that followed, used only a fraction of the mercury Cooper Hewitt lamps did, but produced light much more efficiently.
In 1902 Peter Cooper Hewitt also invented the mercury arc rectifier used for converting alternating current into direct current.
During the World War I Peter Cooper Hewitt was appointed to work on the development of an aerial torpedo or explosive-laden, pilotless aircraft.
Peter Cooper Hewitt died on August 25, 1921 and buried on Green-Wood Cemetery, Brooklyn, Kings County, New York, U.S.A.