268 abstracts: technology 



MINERALOGY. — Glauberite crystal cavities in the Triassic rocks of 

 eastern Pennsylvania. Edgar T. Wherry. American Mineralo- 

 gist, 1: 37-43. 1916. 

 The crystal cavities in the sedimentary rocks, previously mentioned 

 in connection with announcement of the character of lozenge-shaped 

 cavities in zeolite deposits (Journ. Wash. Acad. Sci., 6: 181-4. 1916) 

 are described in detail. They are shown to agree crystallographically 

 with the mineral glauberite. Pseudomorphs of calcite after glauberite 

 are also described. It is believed that the glauberite formed as the 

 result of evaporation of lake waters of Triassic times. E. T. W. 



TECHNOLOGY. — Glasses for protecting the eyes from injurious radia- 

 tions. W. W. Coblentz and W. B. Emerson. Bureau of Stand- 

 ards Technologic Paper No. 93. Pp. 14. 1917. 



The object of the present paper is to give the general characteristics 

 of certain newly developed glasses sometimes used for protecting the 

 eye from radiant energy, especially from the infra-red or so called heat 

 rays. Because of the difficulty in reproducing the same color in dif- 

 ferent melts, no attempt is made to give specific data on the transmis- 

 sion for a given thickness of glass. The data given are representative 

 of an extensive group of glasses available for protecting the eye from 

 (1) the ultra-violet, (2) the visible, and (3) the infra-red rays. 



For protecting the eye from ultra-violet light, black, amber, green, 

 greenish-yellow, and red glasses are efficient. Spectacles made of 

 white glass afford some protection from the extreme ultra-violet rays. 

 For shielding the eye from infra-red rays deep black, yellowish-green, 

 sage green, gold plated, and bluish-green glasses are efficient. For 

 working near furnaces of molten iron or glass if considerable light is 

 needed, a light bluish green or sage green glass is efficient in obstruct- 

 ing the infra-red rays. For working molten quartz, operating oxy- 

 acetylene or electric welding apparatus, or other intense sources of 

 light, it is important to wear the darkest glasses one can use whether 

 black, green (including gold plated glasses), or yellowish-green, in order 

 to obstruct not only the infra-red but also the visible and the ultra- 

 violet rays. Of the infra-red rays emitted by a furnace heated to 

 1000 to 1100°C about 99 per cent are obstructed by gold plated glasses, 

 about 95 per cent by sage green or bluish green glasses, about 80 per 

 cent by very deep black glasses, and about 60 per cent by greenish 

 yellow glasses. W. W. C. 



