|  Sandy Hook Searchlight 
The Sandy Hook proving ground, off the coast of New Jersey, may have seen a large carbon arc searchlight at one time before it closed in 1919.* “A BIG SEARCHLIGHT—To be Mounted at Sandy Hook for Army Experiments” is the title of an interesting article published by The New York Times on December 31, 1893. The piece reads as follows:
“One of the biggest electric searchlights in the world is to be mounted at Sandy Hook. Gen. Flagier, the army Chief of Ordinance, will purchase a monster light for experimental purposes. The apparatus desired, including the light proper, the dynamo, the steam engine and boiler, will cost between $6,000 and $10,000.
 “The workings of the big electric searchlight at Chicago on the roof of the Liberal Arts Building suggested that experiments with another large light would be valuable. It is likely that the German firm which constructed the Chicago light will make the light for Sandy Hook. The bid of that company was $5,900, while the next lower bid was that of the General Electric Light Company of this city, $11,500 in amount. The searchlight has by its use on shipboard become an important part of torpedo warfare. It is absolutely necessary in the operations at night, and the more powerful the light the less will the attacking party be able to do. “Gen. Flagier believes that the searchlight will be very useful in the coast-defense forts at the large ports, and it is with the view of ascertaining utility of these lights that the present apparatus is to be bought and experiments conducted at Sandy Hook proving ground. The system comprises the light proper, with mirror about 60 inches in diameter, furnished with a horizontal arc lamp. The mechanism must be capable of giving the light a rotation in a horizontal and vertical plane, and a governor must be provided to permit of electrically training the apparatus from a distance. The dynamo must produce an intensity of light of about 200,000,000 candle power, while the energy consumed in the lamp must not exceed 150 amperes by 60 volts. The makers of the light must keep it in operation for eight successive nights at Sandy Hook before it is accepted by the Government, and must instruct the force of operators who are chosen by the Ordinance Office.”  The carbon arc light projector above was the largest searchlight exhibited at the Chicago Columbian Exposition of 1893. The 6,000 pound projector operated on a current of 200 amperes and consumed 10 kilowatts of power. Its two carbons were cored, the upper carbon was 1 1/2 inch in diameter, and the lower was 1 1/4 inch in diameter. 
In the 1896 edition of Electric Arc Lighting, a volume in the Elementary Electro-Technical Series, Drs. Edwin J. Houston and A. E. Kennelly tell us that "The dioptric reflector is a glass mirror of special form, called a Mangin reflector. It consists of a spherical mirror, whose inner and outer surfaces are of different radii. The outer surface is silvered, so that the rays coming from the lamp pass outward through the substance of the glass before being projected outward in parallel rays. Some idea of the form of the projector can be obtained from an inspection of the illustration above. It will be seen from this figure that the light is not allowed to pass directly from the arc into the beam, but is thrown from the arc, back to the Mangin reflector, partly with the aid of a small mirror placed in front of the arc, and then from the Mangin reflector outward."
For more on old carbon arc searchlights, read The Electric Mirror on the Pharos Lighthouse and Other Ancient Lighting. *The Sandy Hook proving ground, used to test equipment for the Coast Artillery Corps, was established in 1874.
This page was last modified on Wednesday, August 18, 2010
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