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154                       METALLURGY   OF   CAST   IRON.
desirable to know the manganese, phosphorus, and total carbon contents are such as stove plate, light work, and the general run of chilled castings. From the above it can be seen that it would generally be advisable for furnacemen in advertising their irons to state, together with the numbers of the grades or brands they make, what percentage or range of manganese, phosphorus, and total carbon their irons generally contain, as there are conditions demanding varying percentages of these elements met with that would the greater enhance the sale of the irons were these points made known. As, for example, a founder making very thin castings would require higher phosphorus, which gives more fluidity to iron than is available in some regular No. i grades. Then again, it is often necessary to know what manganese an iron contains, as when it is more than .50 its influence is to harden. With regard to the carbon, the " total" is all that is generally required. Giving the percentage of what is combined or free carbon in pig iron generally tells nothing further than the melting qualities of the metal. In this, the more the carbon is combined the easier or quicker the iron melts  a fact discovered by the writer several years ago, and confirmed by Dr. R. Moldenke by further experiment. If a knowledge of the combined or graphitic carbon contents of pig iron was of any real value in grading pig iron by analysis, grading could be done effectually by fracture or hardness, and the only determination required would be that of the total carbon, phosphorus, or manganese, according as information might be desired of one or all of these ingredients. It is not the author's idea, that because the grades are divided at every quarter of one castings. analysis which may be given is simply an average of the whole, generally taken from the two ends andith the uncertainty of furnace workings when in urgent need of ten hundred             jon of iron; and Sir........................    2,720     "