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224                    METALLURGY OF CAST IRON.
one-half ounces  of pulverized   brimstone.     The  20 pounds of metal was allowed to stand in the hand ladle about forty seconds, when two test bars were poured, both of which, when broken,   agreed very closely in strength.    The stronger one of these is recorded as test bar No. 19.     All of these test bars are of the round form and cast on end.    It will be seen by a comparison of the analysis of these two test bars, Nos. 18 and  19, that the latter absorbed or contains .096 more sulphur than the bar which was poured direct from the cupola, and .160 more than the iron charged. In breaking these bars it will be seen that the high sulphur bar No. 19 stood 540 pounds more than the direct bar No. 18, thereby asserting that sulphur will strengthen iron.    But whether or not such an increase in strength in test bars could be beneficial to castings will depend largely upon  the internal strains which the addition of sulphur causes in increasing the contraction.    This can be seen by Table No. 31, in which the sulphur bar will be  seen to have contracted 1-32 inch more than the direct bar.    I have conducted a number of experiments in adding sulphur to the molten metal with iron ranging from one per cent, to two per cent, of silicon,  and   have   found  it  to  increase  the strength of the test bars.     This is to be expected simply from  the   fact   that   sulphur increases   the combined  carbon.    With two per cent, in silicon in testing   one-and-one-eighth-inch   round    bars,    I    have found it to increase the strength only from 150 to 200 pounds,   thus   showing that the   higher   the silicon, the less effect the sulphur has in strengthening the iron to the limit of its absorption.    Views of the fracture of the  above  bars, described in Tables 31   andthe so-The philosophical explanation of this extraordinary effect i my opinion, to be found in the fact that the f erro-manganesu .R. C. Hindiey, M. Hoskins, Harvard College, Havemeyer University, Henry Hiels Chemical Co., Isabella Furnace, Iron Gate Furnace, Iroquois Iron Co., Illinois Steel Co., Jefferson Iron Co., Kittan-ning Iron & Steel Co., C. A. Kelly Plow Co., Lebanon Furnace, Longdale Iron Co., Lackawanna Iron & Steel Co., Logan Iron........................   16,720     "                                     t-