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272                       METALLURGY   OF   CAST   IRON.
being used. As an example, a mixture of 100 pounds of old horseshoes or any kind of light wrought scrap, mixed with 1,000 pounds of stove plate scrap, has been used to make mould boards for plowrs and which gave a chilled or white iron in the casting. This'mixture was originally given in The Foundry, March, 1898. A study of this chapter in connection with the preceding one should permit founders to obtain mixtures for almost any line of chilled castings, but it must be borne in mind that to obtain the experience to successfully make chilled castings has cost founders more money, labor, and anxiety than any other line of castings.les 47 and 48 than in Tables 45 and 46. Sulphur from .08 to .15 is now considered by many to give long life to car wheel chills. At the same time, it is also considered necessary to have manganese range from .30 to .80 in order to stand the thermal test described in Chapter LVIL This chapter also treats of methods of testing mixtures, car wheels, and annealing them. The depth of chill reqtiired in wheels ranges from )4 to /& of an inch in the throat and y% to i inch at the middle of the thread. Then again, there should not be over % of an inch variation in the depth of chill in like sections of the rim. In making the mixtures, it must be remembered that Tables 45 to 50 show analyses of the iron after it is remelted or in the castings, so that the iron before being charged' must be higher in silicon and manganese and lower in sulphur, after the principle described in Chapter 45.