Light Bulbs

Two much-publicized electrical companies--General Electric and Westinghouse--supply most of the U. S. with lamp bulbs. In Europe that function is performed chiefly by potent Philips Glow-lampworks of Holland, which also boasts one of the finest physical research laboratories east of the Atlantic. Last week it appeared that all three companies were working independently on the same thing --a new sodium vapor bulb to be used primarily for street lighting. In Manhattan, 100-odd members, of the New York Electrical Society sat like jaundiced mummies in an auditorium suffused with the yellow sodium light while their president described the particular bulb of the Dutch company. In Andover, N. J., Westinghouse was demonstrating the uses of the strange light in interior illumination. In Schenectady, General Electric installed 22 of its own sodium vapor lamps on a section of the Balltown Road, watched startled motorists gape at the lights as they sped down the saffron-colored highway.

The light of the bulb is monochromatic, i.e. it glows in but one color. Such light is useful in highway illumination because it reveals the details of objects at low levels of illumination, casts almost no shadow. The yellow glow of the sodium eliminates the offensive glare of white light, and, although the average motorist would probably find the bulb dim at first sight, it actually gives three to four times more light than the ordinary street lamp. The Philips bulb is credited with increasing seeing power at night from 12 to 20 times. Already installed in a dozen places in Holland, England, Denmark, Switzerland and Norway, it has lighted highways so brightly that automobiles can speed at 60 m.p.h. without headlights. European police are delighted with it, automobile clubs indorse it, insurance officials grin broadly at the thought of reduced risks from night accidents.

The bulb itself has four terminals, two for the filament, and is filled with neon gas and metallic sodium. When the current is switched on, an arc light springs from the filament, takes on a red glow from the neon gas, then a yellow glow from the evaporation of the filament. The bulb consumes 80 watts of electricity, but because it produces so much more light than the ordinary lamp of that wattage, its sponsors claim that it is not only more efficient but, once installed, is more economical. Chief problems have been that sodium attacks ordinary glass and that the intense heat of the light destroys the bulb. These flaws have been corrected by the development of a special glass for the bulb. Heat developed in the lamp and necessary for its operation is maintained by an evacuated double-walled glass jacket (like a thermos bottle) placed around the bulb.

The General Electric bulb, also intended chiefly for highways, is equipped with a reflector resembling a "floppy bonnet" to concentrate the light downward, prevent it from being diffused in all directions. It consumes between 80 and 90 watts; its light output is equivalent to that of a Mazda lamp consuming 215 watts.

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