[74] Unless otherwise noted, the short ton of 2,000 pounds is used throughout this chapter and “tungsten ore” means materials carrying 60 per cent. WO₃. The essential uses of tungsten are as an alloy in high-speed tool steel, for the making of filaments for incandescent lamps, for targets and cathodes of Roentgen (“X”) ray tubes, and for electric contacts for explosion engines or wherever an intermittent electric contact is needed. Other uses are in saw and some other steels, as a constituent of stellite, in a tungsten-iron alloy for valves in automobile and airplane engines, for kenotrons and similar instruments, in a manganese-chromium-tungsten-iron alloy for wire-drawing dies, in wire cloth, luminescent screens for Roentgen (“X”) rays, mordants and minor chemicals. =Substitutes.=--The use of tungsten in high-speed steels is as standard as the use of yeast in bread, and, though assiduously sought, no substitute is known that satisfactorily takes its place. According to report, in England and France molybdenum has been used to replace about half of the tungsten in some high-speed tool steels, but this is seemingly not a preferred method, being used only when the obtaining of tungsten is difficult. In the United States the practice has had few sponsors. The following quotation from the _Mining Journal_ (London) for May 25, 1918, p. 318, shows that this sentiment is not unknown abroad: The manufacture of ferromolybdenum is stated to have been commenced in Sweden, where the lack of ferrotungsten has forced the employment of this substitute. During 1917, 104 (metric?) tons of molybdenite was shipped from Norway to Germany, where it probably was used as in Sweden. Henry E. Wood reported finding molybdenum in the steel of a German helmet. When tungsten was at the excessively high price of early 1916, many experiments were made to find a substitute, but apparently without full success, although lately several substitute steels containing cobalt and chromium and especially intended for cast milling-cutters and other multiple-edged tools have been placed on the market and a cobalt-chromium-molybdenum steel and a uranium steel have been offered for lathe tools. Stellite, the cobalt-chromium-tungsten alloy, in which there is only one-third to one-half as much tungsten as is used in high-speed steel, has grown in favor, and cooperite, a nickel-zirconium alloy, is also a competitor, but the trade in the combined list has made no appreciable impression on the demand for tungsten steels. A change in the manner of using tungsten steel, by which a thin plate of high-speed steel is cemented to a more ordinary steel bar so as to form the cutting edge of a lathe tool, has made the demand for tungsten less than it would have been had the old practice been followed of making the whole tool of high-speed steel. CHANGES IN PRACTICE