KINDS OF GLASS 



299 



able in the former case. The roughened surface of the glass prevents 

 the . entrance of direct sunlight and does away with the use of sun- 

 shades. The only value of rough plate glass is in softening the light, 

 the loss of light in passing through it being very great. 



(3) Ribbed or Corrugated Glass. Ribbed or corrugated glass is 

 usually smooth on one side and has 5, 7, n or 21 ribs on the other side, 

 (a) Fig. 146. It varies in thickness and shape of ribs. "Factory 

 ribbed" glass with 21 ribs to the inch is distinctly the most effective of 

 the ribbed glasses. 



RIBBED FIGURED SHEET PPISM 



(a) (tn (c) 



FIG. 146. 



(4) Maze Glass. Maze glass has one side smooth and has a 

 raised pattern on the other side roughening practically the entire sur- 

 face, (b) Fig: 146. It is quite effective. 



(5) Wire Glass. Wire glass is made by pressing wire netting 

 into the molten glass. It is made either plane or with ribs or prisms 

 on one side. Wire glass is injured but not destroyed by the action of 

 fire and water, and is now accepted by insurance companies as fire- 

 proof construction. 



(7) Prisms. Prisms are made in small sections which are set 

 in a frame of lead or other metal, or are made in sheets as shown in (c) 

 Fig. 146. Luxfer sheet prisms, manufactured by the American Luxfer 

 Prism Co., Chicago, will be cut in any size desired up to 84 inches wide 

 (parallel with the saw teeth) by 36 inches high. 



Diffusion of Light.* The light entering a room through a win- 

 dow or skylight comes for the most part from the sky and has, there- 



Mass. 



*Report No. III. Insurance Engineering Experiment Station, Boston, 



