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foooooooo ^h co ooj ooo + fj 1J ; = :la'l ; ; :&! The localities of the samples furnishing the above analyses, and their description as far as given, are as follows: White iron. 1. Maria- zell, Styria; charcoal; sp. gr. 7'729. 2. Re- schitza, Hungary ; charcoal. 3. Cleveland, Eng- land; coke. 4. Medellin, Colombia, used for stamp heads ; sp. gr. 7'45. 5. Primor, Tyrol ; spiegeleisen. 6. Sava, Carniola, Austria. 7. Froschnitz, Styria. 8. Bieber, Prussia. 9. Mil- sen, Prussia, Mottled iron. 10. Cleveland, England. 11. Styria: a, white portion, sp. gr. 7'069 ; }, gray portion, sp. gr. 6-928. Gray iron. 12. No locality; analysis by Fresenius. 13. Cleveland, England. 14, 15, 16. Bessemer iron : Reschitza in Hungary, Neiiburg in Sty- ria, and English (hematite). 17. American gun iron. 18. Austrian gun iron. 19. "Glazy" iron, English. The influence which each of these elementary substances exerts on the physi- cal properties of pig iron cannot be stated with precision. The subject is one of great com- plexity, and has not been thoroughly investi- gated. The following comprises what is kno wn about it. When iron is fused in the presence of carbon, in a reducing atmosphere condi- tions which obtain in the blast furnace it combines with a portion of carbon, forming a readily fusible compound. The condition of the carbon in the molten iron is not certainly known, but it is probably in chemical combi- nation. When, however, this carburetted com- pound solidifies, the carbon may either remain in combination, giving the iron a white color; or it may assume the form of graphitic scales, mechanically disseminated throughout th mass, giving it a black color ; or both conditions of the carbon may coexist, imparting to the iron a shade of gray. So far as is known, these conditions are determined by the rate of cool- ing of the iron. When the iron is quickly cooled, as on being cast in iron moulds or poured into water, the carbon will remain in combination ; when the iron is cooled slowly, the carbon has time to separate, and a part at least will appear as graphite. Snelus (" Jour- nal of the Iron and Steel Institute," vol. i., p. 28) has proved conclusively the separate exis- tence of graphite in pig iron. Bell's experi- ments (" Chemical Phenomena of Iron Smelt- ing ") seem to show that there is no difference in the amount or condition of the carbon in gray and white pig iron made at the Clarence furnace in the Cleveland district, England; and he considers the difference of color to be due to the fact that in the white varieties the graphitic scales are so minute as to be no longer visible. His experiments contradict results ob- tained by investigators in other localities, and have not as yet been confirmed. The highly raphitic variety of pig iron is usually pro- uced at a higher temperature than the white; and it has been noticed that when white iron is exposed to the temperature of a furnace making gray iron, it is changed into gray. This has led to the opinion that the tempera- ture of production is the sole cause of the
