At present the _United States_ has the largest potential supply of molybdenum ores of any country in the world. In addition it has three of the largest and most modern mills that are handling ore from any molybdenum deposit. It is in a favorable position to equal or surpass, for some time, any other country, in output of molybdenum concentrates. Before the war _Great Britain_, through political control of the Australian and Canadian deposits, was the world’s leading producer. Some molybdenum came from _Norway_, but the amount was small as compared to the output of Australia, Norway producing in 1913 only 13 short tons and Australia 162.6. In both Canada and Australia the known deposits have not been worked to capacity and new deposits will probably be discovered with proper prospecting, so that the future molybdenum production under British control promises to increase. The Canadian and British governments are much interested in the development of the molybdenum resources of the dominion. _France_ is entirely dependent upon England and the United States, although it might be able to get a small amount of concentrates direct from Norway. _Germany_ was much interested in molybdenum before the war. During the war it probably did not import any molybdenum concentrates at all, and as the world production before that time was small it is not likely that there was any reserve on hand in the empire in 1919. _Japan_ has no molybdenum deposits as far as is known, and probably is not specially interested at present in the use of this metal. The distribution of the chief molybdenum deposits of the world is shown in Plate VII. [Illustration: PLATE VII.--Geographical distribution of the molybdenum deposits of the world. By R. B. Moore.] SUMMARY Molybdenum commands attention because of its growing importance as a steel alloy metal. Although the metallurgy and properties of molybdenum steels are not thoroughly understood and their use is not widespread, especially in this country, accumulating evidence indicates that molybdenum will eventually become one of the common alloy metals. It is used in the form of wire as supports for incandescent light filaments and in electrical apparatus, and may become essential in the manufacture of special steels. It cannot be easily replaced in chemistry, and for its other applications it is better and cheaper than other materials.