The Iron and steel magazine . olutions of heat. It is Avorth noticing thatthe stop or retardation in the fall of temperature often extendsover an interval of only io° C, and it will be reserved for laterinvestigations to throw light on its exact meaning by extendingthe interval as much as possible. * Carpenter and Keeling, Journal of the Iron and Steel Institute,May, 1904. t Revue de Metallurgie, July, 1904, p. Heyn: Article already cited. Iron ( ai bon . \ Hoys i pn The further course of the cooling brings at 7000 anotherconsiderable delay; as we shall sec from the metallographicinvesti
The Iron and steel magazine . olutions of heat. It is Avorth noticing thatthe stop or retardation in the fall of temperature often extendsover an interval of only io° C, and it will be reserved for laterinvestigations to throw light on its exact meaning by extendingthe interval as much as possible. * Carpenter and Keeling, Journal of the Iron and Steel Institute,May, 1904. t Revue de Metallurgie, July, 1904, p. Heyn: Article already cited. Iron ( ai bon . \ Hoys i pn The further course of the cooling brings at 7000 anotherconsiderable delay; as we shall sec from the metallographicinvestigation, this point corresponds to the temperature wh< carbide is insoluble1 in iron and consequently the entire massof solid solution is divided into an intimately mechanical mix-ture of carbide and iron, cementite and ferrite. This intimatemixture bears the name of pearlite. In the curves given, thispoint is plain for both white and gray iron, corresponding tothe considerable quantities of pearlite which are contained in. Fig. 16. Magnified 500 diameters both (photographs 12 to 17). The location of this point likewisevaries, as is apparent from the following table: Material number 8 19 6 14 18 17 16 Per cent carbon 404 Evolution of heat 702 710 700 708 716 719 692 710 Curve number 1 2 3 4 5 6 7 8 The variations lie outside of the possible errors in the meas-urement of the temperature; since, however, slight differencein the rapidity of cooling plainly alters the location of this point,the difference shown here might perhaps be traceable to suchchanges in the rapidity of cooling. 200 The Iron and Steel Magazine It is now a pleasant task to support or extend the knowl-edge gained from the thermal investigation of the material byan independent method. The microscope is an indispensableaid in the study of metals and alloys and could give more valu-able information still if it were possible to observe the structureof a cross section at any
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