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M'K !'.\< , I II     IN    Sl'l-.ri Al.'l Y     M t \TI: UKS.                     .{7!
carbon evolve uniformly in the graphitic form, by the use of the round test bar, hence, ai^ain showing this to be the best form which we eould adopt for obtaining knowledge of the relative strength, etc., of east iron. It will be seen that by a use of the one-half square bar with weak irons, the carbons remain mostly in the combined state, and. when used for strong iron, its body becomes "white.'" or crystalline. In the one-inch square bars the corners, as may be seen, are much deeper in combined carbon or dense in i^rain than on .the flat surface, as seen at A !>, Pii^s. 97 and 98, and instead of its skin or shell bein^ an even thickness or of a uniform texture, as seen in the round bars at D and R, Pii^s. 97 and 98, it is very irregular. Furthermore, although the square bars arc of about the same area as the round bars, still we find the latter has the greatest body of metal in the ^ra-phitic form.
Complete analyses of all the specialties here exhibited in combinat ion with others are presented in Chapter XI,IV. These will assist in delining the percentage of ehemieal proper! ies best lo exist in an iron or mixtures to s<weure the various physical conditions and qualities dt'siivd in eastings at the present day. N'os. -,!<; and 30, Fi-j;'. iu.!, illustrate t he affinity of iron for sulphur, bein^" the bars described in Chapter XXXM in which sulphur oi" brimstone was plaeed in the ladle after No. 30 had been poured. The* whit<* rin# at II, No. 29, shows the hardening effect of sulphur.aragraph.