Very pure manganese oxide is used in making the common dry battery, the production of which has greatly increased with the wide use of the internal-combustion engine. About 25,000 tons is used annually in the United States for this purpose. The manganese oxide thus used is not consumed, but becomes exhausted through the loss of oxygen. Under stress of high prices, the oxide may be regenerated by treatment or by mixture with new refined material. Small quantities of manganese ore are used in making many chemical products and pigments. CHANGES IN PRACTICE Any consideration of the need for manganese ore and ferromanganese and of dependence upon foreign sources of supply should take account of the degree to which low-grade ore and spiegeleisen may be used as substitutes for high-grade ore and ferromanganese. Thus, although both Germany and the United States have only insignificant resources of high-grade ore, both possess unusually large reserves of low-grade ore. Under recent conditions in the United States the percentage of total manganese used as spiegeleisen increased in three years from 10 to about 18 per cent. Competent authorities have estimated that this substitution may be further increased to nearly 70 per cent. with slight modifications in practice and modest addition of equipment. Some competent engineers further contend that by other modifications of practice a large part of the manganese now needed as alloys may be eliminated by the addition of low-grade manganese ore during early stages of the smelting and refining process. GEOLOGICAL DISTRIBUTION Although concentrated masses such as are useful in the arts are rather uncommon, manganese is widespread throughout the earth; it forms a part of about 100 minerals and most of the common rocks, igneous as well as sedimentary, contain 0.1 to 2 per cent. Present requirements as to grade are such that manganese ores are largely oxides. The carbonate, rhodochrosite, contains enough manganese to permit its use in making 80 per cent. ferromanganese, but only in a few places are the masses large enough to be the basis of extensive mining. The common silicate contains 43 per cent. manganese, but the silica content is so high (23 per cent.) that it can not be used alone in making the ordinary alloys. The common oxides of manganese are deposited under many conditions which are found near the surface of the earth. Large masses of oxides were deposited in shallow marine waters, in shallow fresh-water basins and under many other conditions in the relatively thin mantle of weathered rock that is found over the entire world. Although most of these large masses were formed in the surface zone where the underlying unweathered rocks are unusually rich in manganese, some large masses of oxides accumulate under peculiarly favorable conditions by the concentration of small quantities of manganese disseminated through the common rocks.