232 



Royal Society : — 



vity, in the liquid state, of a body having so high a fusing tempe- 

 rature as cast iron is attended with many difficulties. By an in- 

 direct method, however, and operating upon a sufficiently large 

 scale, the author has been enabled to make the determination with 

 considerable accuracy. A conical vessel of wrought iron of about 

 2 feet in depth and 1*5 foot diameter of base, and with an open 

 neck of 6 inches in diameter, being formed, was accurately weighed 

 empty, and also when filled with water level to the brim ; the 

 weight of its contents in water, reduced to the specific gravity of 

 distilled water at 60° P., was thus obtained. The vessel being 

 dried was now filled to the brim with molten grey cast iron, addi- 

 tions of molten metal being made to maintain the vessel full until 

 it had attained its maximum temperature (yellow heat in daylight) 

 and maximum capacity. The vessel and its content of cast iron 

 when cold were weighed again, and thus the weight of the cast 

 iron obtained. The capacity of the vessel when at a maximum 

 was calculated by applying to its dimensions at 60° the expansion 

 calculated from the coefficient of linear dilatation, as given by La- 

 place, Riemann, and others, and from its range of increased tem- 

 perature ; and the weight of distilled water held by the vessel thus 

 expanded was calculated from the weight of its contents when the 

 vessel and water were at 60° F. 



We have now, after applying some small corrections, the ele- 

 ments necessary for determining the specific gravity of the cast iron 

 which filled the vessel when in the molten state, having the absolute 

 weights of equal volumes of distilled water at 60° and of molten 

 iron. The mean specific gravity of the cast iron which filled the 

 vessel was then determined by the usual methods. The final result 

 is that, whereas the specific gravity of the cast iron at 60° P. was 

 7*170, it was only 6-650 when in the molten condition; cast iron, 

 therefore, is less dense in the molten than in the solid state. Nor 

 does it expand in volume at the instant of consolidation, as was 

 conclusively proved by another experiment. Two similar 10-inch 

 spherical shells, 1*5 inch in thickness, were heated to nearly the 

 same high temperature in an oven, one being permitted to cool 

 empty as a measure of any permanent dilatation which both might 

 sustain by mere heating and cooling again, a fact well known to 

 occur. The other shell, when at a bright red heat, was filled 

 with molten cast iron and permitted to cool, its dimensions being 

 taken by accurate instruments at intervals of 30 minutes, until 

 it had returned to the temperature of the atmosphere (53° F.), 

 when, after applying various corrections, rendered necessary by 

 the somewhat complicated conditions of a spherical mass of cast 

 iron losing heat from its exterior, it was found that the dimen- 

 sions of the shell, whose interior surface was in perfect contact 

 with that of the solid ball which filled it, were, within the limit 

 of experimental error, those of the empty shell when that also was 

 cold (53° E.), the proof being conclusive that no expansion in 

 volume of the contents of the shell had taken place. The central 



