| Fig. 2.—Section through Prism Pavement Light, the direction of light rays being indicated by arrows. |
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| Fig. 3.—“British Challenge” Glazing. | Fig. 4.—Mellowes’ Glazing. |
| Fig. 5.—Heywood’s Glazing. |
| Fig. 6.—Helliwell’s “Perfection” Glazing. |
| Fig. 7.—Rendle’s “Invincible” Glazing. |
The system of glazing known as the “British Challenge” (fig. 3), with steel bars encased with a sheeting of 4-℔ lead, is very simple and durable, needs no painting, and can be fixed at as much as 8 ft. clear bearings, with the bars spaced 2 ft. apart. The ends of the bars rest on the wood or steel purlins or plates, and are either notched and screwed down, or simply fitted with a bracket which is screwed. The bar is of T section with condensation grooves, and the lead wings on top are turned down on to the glass after fitting. This lead-covered steel bar is a great improvement on the plain steel bar as it is entirely unaffected by smoke, acids or exhaust fumes from steam engines; this is important in the case of a railway station, where the fumes would otherwise eat the steel away and so weaken the bars that in time they would snap. Another somewhat similar system is known as “Mellowes’ Eclipse Roof Glazing” (fig. 4). It consists of steel T-bars having lead wings on top to turn on to the glass in a similar manner to the last, the top wings being double and the underside of the bar having an additional wing to catch the condensation. The Heywood combination system (fig. 5) is composed of galvanized steel T-bars, sometimes encased in lead and sometimes partly encased. It has a capping and condensation gutters of lead, and the glass is bedded on asbestos packing to get a better bearing edge, so as to be held more securely. Hope’s glazing is very similar, but the bars are either T or cross according to the span. The “Perfection” glazing used by Messrs Helliwell & Co. (fig. 6) is composed of steel shaped T bars with copper capping, secured with bolts and nuts and having asbestos packing on top of the glass under the edges of the capping. Pennycook’s glazing is composed of steel shaped T bars encased with lead and lead wings. Rendle’s “Invincible” glazing (fig. 7) is composed of steel T bars with specially shaped copper water and condensation channels, all formed in the one piece and resting on top of the T steel; the glass rests on the zinc channel, and a copper capping is fixed over the edges of the glass and secured with bolts and nuts. Deard’s glazing is very similar, and is composed of T steel encased with lead; it claims to save all drilling for fixing to iron roofs. There are also other systems composed of wood bars with condensation gutter and capping of copper secured with bolts and nuts, and asbestos packing with slight differences in some minor matters, but these systems are but little used.
Cloisonné glass is a patent ornamental glass formed by placing two pieces flat against each other enclosing a species of glass mosaic. Designs are worked and shaped in gilt wire and placed on one sheet of glass; the space between the wire is then filled in with coloured beads, and another sheet of glass is placed on top of it to keep them in position, and the edges of the glass are bound with linen, &c., to keep them firmly together.
Glass is now used for decorative purposes, such as wall tiling and ceilings; it is coloured and decorated in almost any shade and presents a very effective appearance. An invention Use in building. has been patented for building houses entirely of glass; the walls are constructed of blocks or bricks of opaque glass, the several walls being varied in thickness according to the constructional requirements.
It is certainly true that daylight has much to do with the sanitary condition of all buildings, and this being so the proper distribution of daylight to a building is of the greatest possible importance, and must be effected by an ample provision of windows judiciously arranged. The heads of all windows should be kept as near the ceiling as possible, as well to obtain easy ventilation as to ensure good lighting. As far as is practicable a building should be planned so that each room receives the sun’s rays for some part of the day. This is rarely an easy matter, especially in towns where the aspect of the building is out of the architect’s hands. The best sites for light are found in streets running north and south and east and west, and lighting areas or courts in buildings should always if possible be arranged on these lines. The task of adequately lighting lofty city buildings has been greatly minimized by the introduction of many forms of reflecting and intensifying contrivances, which are used to deflect light into those apartments into which daylight does not directly penetrate, and which would otherwise require the use of artificial light to render them of any use; the most useful of these inventions are the various forms of prism glass already referred to and illustrated in this article.
See L. F. Day, Stained and Painted Class; and W. Eckstein, Interior Lighting.
(J. Bt.)