The largest producer of army optical instruments, the Bausch & Lomb Optical Company, of Rochester, held contracts amounting to more than $6,000,000 in value and produced before the armistice materials worth over $3,000,000. The War Department obtained no machinery from this plant when the contracts were terminated, but it received and shipped to Frankford Arsenal large quantities of finished parts of instruments. The present optical shop at Frankford was largely equipped with machinery originally procured by the Recording & Computing Machines Company of Dayton. This company, which had never built optical instruments before the war, took contracts worth $4,000,000, built and equipped a complete optical plant, and became a producer, among other things developing a mechanical method of milling glass for prisms. Similar methods of demobilization were followed at all the war factories making sights and fire-control instruments: desirable machinery and unfinished components were collected at Frankford Arsenal, and the excess materials were sold. This plan put thousands of instruments into the war reserves, enough of some sorts to maintain the military establishment for years to come. Of certain important classes of instruments the quantities obtained from the war industry are deficient. Between the year 1914, when war broke out, shutting off the export of optical glass from Germany, and 1917, when the United States went into the war, five American organizations--the Bureau of Standards, the Pittsburg Plate Glass Company, Keuffel & Esser, the Spencer Lens Company, and Bausch & Lomb--developed the manufacture of optical glass on a small scale, but in quality the glass was not up to the European standard. In the spring of 1917, scientists of the Carnegie Institution of Washington stepped in to help the manufacturers with their glass problems, and complete coöperation all along the line resulted in a successful industry before many months had gone by. The four commercial producers eventually turned out optical glass more rapidly than both the Army and Navy could use it. Some of this glass was the equal of any ever made in Germany, and much of it, though of “war quality,” was still good enough for many uses. The army ordnance contracts were entirely with Bausch & Lomb and the Pittsburg Plate Glass Company at its Charleroi (Pennsylvania) plant. The production of glass on the war contracts was terminated immediately after the armistice. A large quantity of glass not yet formed into sets of optics was stored at Frankford. The Pittsburg Plate Glass Company did not resume any production, but Bausch & Lomb continued to make optical glass for their own uses.