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Sweet's Catalogue of Building Construction · 1915
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Sweets's Catalogue of Building Construction, 1915, page 868

Sweets's Catalogue of Building Construction, 1915, page 869
The Mullen "Replaceable Vault Light" was produced and placed on the market to provide a vault light which would not only give the best results in light, strength of construction, pleasing appearance and durability, but would also provide the buyer with a perfect means by which broken glass could be easily replaced, adjusted and made perfectly water-tight in a few moments' time without induring the durability or neat appearance of the walk in which they are installed.
This vault light consists of a circular, threaded glass, with a wire spring screwed into and following the threads that are cast in the circumference of the glass. The wire terminates at each end in an arm, which is given up upward and downward turn in order to make the anchorage in the concrete more secure. The glass with the wire spring around it, as shown by accompanying illustrations, is placed in the walk and the concrete poured in and worked down in the usual way. When a glass becomes broken it can be knocked out, leaving the wire firmly cast in the concrete to form a clean, smooth thread into which the "Replacement" glass may be turned after the sleeve has been coated or buttered with a thin layer of waterproofing paste.
Method of Inserting Glass.
The illustration below, from photograph, is a good example of the light admitted where the Mullen system of "Replaceable Vault Lights" is used. The insert of slab containing four glasses shows how neatly glass can be broken out and replaced. One glass remains in place as originally installed and one has been removed to show how the spiral wire forms a thread to receive "Replacement" glass. The glass to the left has been replaced and the one in the immediate foreground is shown partly in section to illustrate how firmly the wire in imbedded in the slab.
Replacing Broken Glass.
The accompanying illustration shows method of turning the "Replacement" glass into place after the old glass has been removed. When installing a glass in a walk which has become worn own, it can be turned into place until it comes flush with the worn-down surface of the walk and can be left in this position, thus doing away with the heretofore very objectionable fact that the glass replaced in an old walk would project above the other glass that had become worn down so as to be easily kicked out of place or broken.
On the completion of each contract we leave a quantity of "Replacement" glass with the purchaser, and key for turning same into place, so that repairs can be quickly made if necessary.
The glass used is made exceptionally strong and tough to offer the greatest resistance to breakage. It is perfectly transparent, owing to its high quality, and admits the daylight so completely that by its use dark and useless basements are turned into cheerful sun shiny rooms that are often much better lighted than those having windows fronting on the street.
How to Specify.
For vault lights, if the latest and most improved construction is desired, one which will give the maximum amount of light, strength and durability and at the same time provide the owner with a quick and convenient means of replacing broken glass, specify the Mullen "Replaceable Vault Light," stating what type of glass is desired.
Sweet's Catalogue of Building Construction · 1915