[Illustration: DRILLING THE SAMPLES No oil or other lubricant is allowable and the drillings are taken up with a magnet that no sand or other impurity may get into the sample for analysis. ] While some foundries still attempt to accomplish this difficult and sometimes impossible feat, the majority are now applying more scientific methods to their manufacture of cast iron. Though the eye cannot tell surely from the fracture the composition or quality of the iron which is used in making up the charges, chemical analysis does definitely give this information. Therefore, every car of pig iron purchased by this firm is sampled and analyzed, the composition of all other materials used in its mixtures is determined, and, irrespective of fracture, which may or may not tell the truth regarding their composition, the raw materials are charged with respect only to their actual content of the metalloids. The resulting molten iron each day is analyzed to confirm the correctness of the mixture and to furnish analysis of the “sprues” which next day are to be used as a part of the day’s charge. Physical test bars, too, are cast each hour or so, and the tensile, transverse strengths, hardness, shrinkage, etc. are accurately determined in testing machines and recorded. In this way absolutely nothing is left to chance or to guess work, and, as you may surmise, any slight deviation from the composition desired is shown at once and the mixture immediately changed to the extent necessary to bring the iron back to normal. It is surprising within what narrow limits of variation compositions and physical properties can be held, with furnace operations continually under such surveillance. [Illustration: WEIGHING OUT PORTIONS FOR ANALYSIS The finely divided mixed drillings are shaken from a thin-bladed spatula on to the balance pan. Drillings are added or taken off until the long needle attached to the beam of the balance swings over an equal number of divisions on each side of the center mark of the white scale in the middle. Accuracy is 1/453,000 of an avoirdupois pound; this is approximately the weight of the lead of a “pencil mark” one inch long. ] As the basis for its cast iron, many thousands of tons of pig iron are each year used direct from the blast furnaces. The raw materials come in railroad cars or by boat. The inspector who represents the metallurgical department enters each car and inspects the materials, taking from each a representative sample for analysis. In the case of pig iron this will be from four to eight half pigs, it having been found by experience that these represent very well the contents of the car. So each car of material is held without unloading until it has been determined by inspection and analysis that it is fully up to the specifications upon which the iron was purchased.