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156                       METALLURGY   OF   CAST   IRON.
change from one number to another would make a mixture which would vary so greatly as to make castings so unfit for their use that they would be condemned ; and this some of the methods that have been advanced would do.
One objection made to the author's method of grading, seen in Table 22, is that errors in analysis could make a difference of .25 per cent, silicon and .01 in sulphur. Granting this to be true, as has often been the case, does this offer any just cause for the consumer not defining as closely as he may the grade he desires to correspond with any range in numbers from one to ten in Table 22? If such difference in analysis continued to exist they could injure the consumer as much as if grades were divided by one per cent, of silicon, instead of .25 per cent, as shown. To the author's view, this is a factor that should have no weight in deciding the division of grades. However, by the use of the American Fotindrymen's Association standardized -drillings, and the adoption of more uniform methods of making analyses  which is sure to come and for which work the author is chairman of a committee appointed by the American Foundrymen's Association in 1901 to advance such improvement  there will be little excuse for any great difference in the chemical analysis of one sample of drillings by different chemists. There is much more that might be said on the subject of this chapter, but the author trusts that the principles herein advanced will aid the work of bringing about the reform in grading or buy-ing pig iron by analysis which this chapter advocates, and which almost all now concede should be accomplished. when the character of iron is noticeably changed, and not something that is so flexible that anyne 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     "