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53 The Manufacturer and Builder. [January, 1891]

Improved Vault and Sidewalk Lights.

    We exhibit in Figs. 1 and 2 herewith printed, an ingenious novelty in the form of a vault light, with ventilating cover, manufactured by J. C. French & Son, 155 West Broadway, New York. Fig. 1 represents a top view of this cover, and Fig. 2 a vertical section through the center, showing it laid on the walk. French's ventilating cover (section)
Fig. 2
Fig. 1
French's ventilating cover (top view)
The collar which forms the top section of the vault space, upon which the cover rests, is cut away at intervals all about its upper edge, and a series of angle pieces joined to the under side of the cover, and connected with the collar, holds the cover firmly in place. The edge of the cover, projecting beyond these angle pieces, does not come down flush with the sidewalk, but leaves a slight vacant space there all around its circumference, so that there can be at all times a free passage of air from the vault to the sidewalk.
There is thus insured constant ventilation, while the construction of the cover is such as to prevent the access of dirt and water. Furthermore, the cover is not raised sufficiently about the walk to become an obstacle to travel. The invention seems well adapted for its intended service.
    In Fig.3 is shown a view of an improved form of concrete light, which is novel and useful. It is claimed by the manufacturers to be the only form of concrete light that can be relied on to be durable in service, owing to difference in the rate of expansion of glass and other materials, which, if a rigid joint is employed between them, will be sure sooner or later to crack the glass by expansion and contraction from differences in temperature. In this form of tile, an elastic joint is employed, which is claimed very effectually to guard against this cause of trouble. There are twenty-nine glasses to the square foot in this tile, and they are set in taper metallic rings larger than the glass, the space between being fill with an elastic cement. They are then placed in the casting and concreted. The concrete covers both ring and joint, so that they are not visible. Extensive and prolonged use of tiles provided with lights thus cemented, have demonstrated their ability to stand the severest test of changes of temperature--frost and heat-- remarkably well.
French's improved concrete vault light
Fig. 3
Manufacturer and Builder, Vol. XXIII, No. 3, March 1891; Cornell