. Nature . rons it isassociated with the ferrite and pearlite; but grey iron isthe final result of the decoinposition of carbide of ironand possibly silico-carbides, which primarily form duringsolidification, .and although the silicon in the decomposedproduct may be entirely associated with the iron, it is noproof that initially some of it may not have crystallisedwith the carbides. In the white Cleveland iron, previously referred to, itis probable that the several constituents are present in thefollowing proportions :— Silico-pearlite, the residue of the original austenite octahedral crystall
. Nature . rons it isassociated with the ferrite and pearlite; but grey iron isthe final result of the decoinposition of carbide of ironand possibly silico-carbides, which primarily form duringsolidification, .and although the silicon in the decomposedproduct may be entirely associated with the iron, it is noproof that initially some of it may not have crystallisedwith the carbides. In the white Cleveland iron, previously referred to, itis probable that the several constituents are present in thefollowing proportions :— Silico-pearlite, the residue of the original austenite octahedral crystallitesIron carbide in platesIron, phospho-carbide eutecticManganese sulphideIron sulphide Per cent. 42-5033-6623-100-380-36 100-00When fractionally dissolving the powdered metal inacid, it was the iron and associated silicon of the pearlitewhich passed into solution, and the carbide and phosphidewhich remained insoluble, and as these contained only0-I2 per cent, silicon, or about o-o6 per cent, on 100 parts. KlG. 5.—.Same as Fig. 4. Section cut parallel to thesurface of a massive carbide ground mass is carbide of iron,the white dots are sulphide of iron. of the original metal, it is evident that the pearlite musthave contained 1-89 — 0-06=1-83 per cent, of the silicon, or on 100 parts of it =4-3 per cent., and that about 42-597 per cent, of the total silicon had crystallised with theaustenite. A little reflection will lead to the conclusion that if thecarbon in the Cleveland white iron were to be graduallyincreased, the proportion of primary austenite crystalliteswould decrease ; there would be less and less of them tocarry the silicon, and this element would be concentratedin the diminishing solid austenite. It also follows that ifthe carbon \Yere to be so increased that no primaryaustenite would form, the silicon would have to crystallisein some other constituent. In the , referred to above, of the chilled cast-ing, the carbides contained only 0028 per c
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