DEVELOPMENTS IN GLASS INDUSTRY 145 



observing certain precautions, it is possible to prepare 

 silicate glasses of much greater transparency to ultra-violet 

 light than common glass. A special product of this char- 

 acter made by the Jena works and marketed under the 



/O 



/O 



J 



CaO 



11 Curve of equal stability 

 ....-.-. Curve of equal devitrifying temperature 



FIG. 2 



name of "uviol glass" has found application especially in 

 astro-photography and in the manufacture of the uviol 

 mercury lamp. This latter, as our readers may remember, 

 is used for medical purposes in the treatment of skin 

 diseases, and in certain chemical industries, especially in 

 the production of linseed oil products. 

 10 



