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ordinary arcs than by either incandescent lamps or flaming arcs. The ice would reflect the white light better than the yellow.
The following is a brief summary of tests made by the Electrical Testing Laboratories in the Harlem branch office of The
New York Edison Company, 27 East 125th street, illuminated by means of cove lighting and Holophane clusters, and the
drafting-room of The New York Edison Company at 55 Duane street, lighted by diffuser-arc lamps:
Approximate dimensions: front section, 37 feet long, 23 feet 8 inches wide, 28 feet 6 inches high; rear section (Figure 5), 51 feet 4 inches long, 23 feet 8 inches wide, 23 feet 3 inches high. Ceiling and walls, light cream color; lower walls in front of
room, dark finish. Ceilings broken by skylights, and front and rear walls by window.
The cove, of special type, is placed 4 feet 9 inches below the level of the ceiling, on the side walls, and contains 280 16-cp clear lamps, 140 on each side.
The wiring is in conduit, with condulets every 8 inches. supplying the lamps, which are placed horizontally. This conduit is in sections, and may be lifted entirely out of the cove to facilitate repainting or cleaning.
Six Holophane clusters of a special type, two of which were
equipped with 100-watt GEM lamps and four with standard 16-cp lamps, were installed, not so much with the idea of increasing the illumination as to give direction to the light.
In order to make a comparison of the cove lighting with one of the most efficient forms of incandescent lighting known, two rows of incandescent lamps, 42 in each row, were strung temporarily along the ceiling in the rear part of the office. The following table is reproduced from the report of test:
Figuring the ceiling lighting as 100 per cent, the cove lighting therefore would have an efficiency of about 32 per cent and the cluster lighting an efficiency of about 69 per cent. As the ceiling and cluster lamps are not centred as well as could be desired, the figures showing sacrifice in efficiency by the use of cove lighting are naturally conservative.
Duane Street Drafting-Room
Dimensions: approximately 24 feet 4 inches wide, varying from 52 feet 4 inches to 71 feet long; 13 feet 6 inches high (Figure 6). Height of diffuser level above floor, I feet.
Room finished in cream color; windows covered by shades of similar tint.
The diffusion is good, and although the ceiling is low and the illumination high, the light is not at all objectionable.
A comparison between the average foot-candles per watt of the arc-lamp installation and the average foot-candles per watt of the ceiling installation, in the Harlem office, is interesting. It would hardly be fair to make a direct comparison, however, on account of their different environments.
The extent to which various types of lighting units are avai!.. able to the illuminating engineer is shown in the following illustrations:
Figure 7 shows the Moore tube lighting in the lobby of Madison Square Garden. This tube is 162 feet long. Total watts, 2950. The lobby is 22 feet 6.5 inches wide by 93 feet 10.5