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l86                      METALLURGY   OF   CAST   IRON.
etc., would be found in the casting when the skin was removed by a drill, lathe, or planer. Again, the fact that the metal drops from the top of the mold besides entering at the bottom, causes the top body of the rising metal to be as fluid as that at the bottom, which is also beneficial in causing all scum and dirt to float upward with the metal to the top of the mold or *c riser head.'' Where metal fills a mold all from the bottom it becomes rapidly duller in rising to fill the mould and can leave dirt scattered throughout the casting, an evil which will be readily seen. Fig. 45 shows a section of the casting obtained from the mould, with the exception of four lugs cast on to assist in holding the cylinder or casting in the lathe while it is being turned. It will be well to state that there is no difficulty in obtaining castings weighing tons which might serve for standardizing purposes, if cast upon the principles herein described. Before starting to make these castings, investigations were made as to the variations in metalloids most likely to be demanded by the trade in general. It was found that samples high, medium, and low in silicon, sulphur, manganese, and phosphorus would satisfy most of our country's laboratories as far as iron standards were concerned. To obtain this variety of standards called for the making of three distinct castings of different grades of iron. These were cast with iron melted in a small cupola, under the direction of the author, at the Thos. D. West Foundry Co., after the plan herein described.
To obtain the turnings or drillings, which had to be fine enough to pass a 2o-mesh sieve, was no easy matter and rather a costly affair. To get one pound of drillings per hour was thought to be good work. Thepen or close grained iron in connection with exacting any certain specified analyses from blast furnaces, as the slight difference possible in the most radical cases of open and close grained iron can be regulated by a slight variation in silicon when making a mixture, and which anyone can easily do, if they so desire,  "