Variation with Temperature of the Thermal Conductivity of Soft Gray Cast Iron, 195° to 542° $C$.—The sample used contained 3.5, 2.2 and 0.64 per cent. of C, Si and Mn respectively, and was cast into the form of a cylindrical shell 3 cm. thick, joined with a hemi-spherical bottom. The temperature differences between the liquids inside and outside the shell, which amounted to from 3° to 6° with an input of from 0.24 to 1.6 kw, were measured with thermo-couples silver-soldered in the ends of brass tubes. Since even though these tubes were pressed against the iron surfaces, the temperatures thus measured differed more or less from the actual temperatures of the surfaces, the absolute values found for the conductivity are too low; but the results indicate that the conductivity at 542° is between 2 and 3 times its value at 195° C.

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