GRADING PIG IRON BY ANALYSES. ' ^55
percent, in silicon and the sulphur ranging from .onto .10 per cent., as shown by Table 22, that any furnaceman should be compelled to fill orders from any one., particular grade or number of iron. It is intended that the number ordered should indicate the grade of iron the consumer desired, and to fill the order the furnaceman could ship any number of grades from which an average might be obtained which corresponds to the grade order. If, for example, in following* tlie method of grading advanced in Table 22 one should desire a No. 4 iron, he can accept irons ranging from No. i to No. 8 to make an average which would give the grade No. 4 desired, provided he knew the g-rade of every car delivered at his yard. There is surely sufficient margin in this method to permit the furnace-man to fill an order for any particular grade of Iron for the great majority of purchasers.
When foundry men, as a rule, desire to produce ca.st= ings that are to be of some particular softness or hardness, and we know that a change of twenty-five points in silicon and two points in sulphur can cause them to vary from the best grade which should exist in tlieir castings, the author fails to perceive the impracticability of any furnaceman accepting orders for foundry, bessemer, gray forge, mill, or basic pig irons by tlie method of numbering the grades from i to 10, wliicli he has advanced in Table 22. In fact, any greater margin would fail to denote the true character of tlie iron desired and could cause such misunderstanding as to result seriously for both furnaceman and founder. What is required is a method of numbering that will denote 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 "