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146                       METALLURGY   OF   CAST   IRON.
his practice based upon correct principles, or he cannot expect the results he desires in making mixtures of iron. An ill-mixed cast of pig iron can, generally, mislead any founder in determining the cause of failure to obtain the grade of iron he felt so confident of securing.
A thorough mixing of a cast of pig iron is not a difficult task; it requires but a recognition of its necessity, and means can be readily devised to accomplish the end. One plan, practicable of adoption by most furnaces, would be when loading cars for shipment to consumers to have every other buggy load, or pig if handled by men, placed at the opposite ends of the car. When the foundryman unloads the car he should follow the plan pursued in loading, which means to take a pig from each end of the car alternately and load onto buggies or in piles. By such a method a cast or car of iron should be pretty well mixed by the time it was charged into a cupola.
Where a founder has yard room, a good plan is to load several cars of the iron closely alike in analysis, or for one mixture, on top of each other in a long pile, being careful to have each car load distributed evenly in height the whole length of the pile, and in taking the iron from the car take a pig from each end alternately as near as practicable. A pile of any certain grade or brand of this character can be made to hold 'six or more cars of iron, and then when using the iron from the piles it is taken from the two ends as uniformly as practicable. A little study of this method will show that drillings taken from four to six pieces of pig, pulled from a fair division of the two ends would, when thoroughly mixed and analyzed, give an light castings, can change the character of the carbons orhe one 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     "