In the early 20th century glass for the optical systems of telescopes, microscopes, field glasses, navigation and surveying instruments, cameras, and similar instruments was expensive to make and had a limited market. Therefore, American optical firms imported their quality glass. World War I, however, abruptly cut off the supply of optical instruments and optical glass to the U.S. In 1914, The director of the National Bureau of Standards (NBS) ordered furnaces and apparatus for the field laboratory in Pittsburgh, and set it to work studying the manufacture of optical glass. [From: Measures for Progress by Rexmond C. Cochrane, p. 187]. This collection of photos depicts glass operations at NBS from the 1920s to the 1940s, and beyond.
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