3 02 WINDOWS AND SKYLIGHTS 



panes of windows. Where the skylight area is very small, the light is 

 obstructed, or a very superior light is desired, use prisms. Wire glass 

 should be used where there is danger from fire and in skylights, where 

 it removes the necessity of stretching wire netting under the glass to 

 protect it and to prevent it from falling into the building when broken. 

 Placing the Glass. Factory ribbed glass is somewhat more ef- 

 fective if the ribs are placed horizontal, but the lines of light deflected 

 from the horizontal ribs may become injurious to the workmen's eyes 

 and it is now the custom to set the ribs vertical. Ribbed glass should 

 have the ribs on the inside for ease in keeping it clean, and where double 

 glass is used the ribs should face each other and be crossed. Care should 

 be used in setting thick wire glass in metal frames ; the lower edge 

 must bear directly on the frame, but the top and sides should fit loosely 

 so that the differential expansion of the glass and frame will not crack 

 the glass. Plane glass and small panes of other kinds of glass are 

 set with glaziers' tacks and putty. In skylights and large windows 

 some method must be used that will allow the glass to expand and con- 

 tract freely and at the same time will be free from leakage. Several 

 methods of glazing skylights without putty are shown in Fig. 148. 

 Skylight bar (a) manufactured by Vaile & Young, Baltimore Md., is 

 made of heavy galvanized iron and lead. 



(a) (b) (0 id) (e) 



Bars (b) and (c) are made of zinc or galvanized iron, supported by 

 a steel bar. Bar (c) is adapted to small panes of glass and is made 

 of galvanized iron; it is made water tight by the use of putty. The 

 skylight bars in Fig. 148, all have condensation gutters to catch the 

 moisture that leaks through or forms on the inner surface of the glass. 



