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.