In 1914 experiments were started on the making of optical glass, and in three years the bureau was able to turn out good grades of glass in all the usual varieties. This work has been continued and the bureau regularly supplies the Navy Department with glass for range finders, periscopes, and other optical instruments.
In the experimental paper-mill, a paper on which to print Amer ican currency has been developed which shows a strength twice as great as the paper formerly used. Optimum conditions for the storage of books and documents have been worked out for libra ries, and special attention is (194o) being paid to the durability of motion picture film used for micro-reproduction of records.
During the past few years special attention has been paid to the properties of building materials, including prefabricated units, with special reference to low-cost housing. Heating appliances, ventilating equipment, and thermal and acoustical insulating ma terials have likewise been studied. The results of this work are made available through a new series of publications called "Build ing Materials and Structures Reports."
The bureau is active in the automotive field and has equipment for studying the performance of internal-combustion engines and auxiliary equipment under service conditions. It also has a well equipped hydraulics laboratory where large-scale models of dams and other structures can be built. These facilities are utilized by the Engineer Corps of the Army, Reclamation Service, and many other agencies.
The bureau's publications comprise the Journal of Research of the National Bureau of Standards, reprints from the Journal known as Research Papers, Circulars, Handbooks, Simplified Practice Recommendations, Commercial Standards, Building and Housing, Building Materials and Structures Reports, Miscellane ous, and the Technical News Bulletin. They are obtained from the Superintendent of Documents, Government Printing Office, Washington, D. C. (See STANDARDIZATION.) (L. J. BR.)