TRANSACTIONS OF SECTION G. 



507 



and gives way to a floating effect. From this it appears evident that cold cast 

 iron sinks when first put in a bath of molten iron, and that therefore its specific 

 gravity is higher than that of the liquid metal, and that its rapid expansion dis- 

 placing the liquid metal, and causing it so quickly to come to the surface, has led 

 to the widespread but erroneous belief in the anomaly described. This has been 

 proved by the writer in a more direct way, by making a number of spheres of cast 

 iron, 1, 2, 3, 4, and 5 inches in diameter. These when cold were lowered (not 

 thrown) into the molten iron by means of a bent iron fork, the ball resting freely 

 on the two prongs of the same. 



In every case the ball went down with the fork, rested under the metal for a 

 few seconds, and then rose to the surface, the experiments being confirmatory of 

 the results obtained with the apparatus already described. 



The diagrams also show that the line showing change of volume continues to 

 rise in a somewhat irregular curve until it reaches its maximum above the line 

 of equilibrium. The further increase of heat then appears to have little effect in 

 changing the volume of the ball, as the line of volume remains in its maximum 

 position until melting commences, when the ball rapidly subsides. 



The table accompanying this shows the maximum variations of sinking or float- 

 ing effect in percentages of the actual weight of the balls, also the actual floating 

 or sinking effect in ounces avoirdupois. 



From the above it will be seen that the volume of the ball in the first expe- 

 riment varies from 3-4 per cent, below, to 12-8 per cent, above the volume of 

 equilibrium, being a total change between the extremes of 16'2 per cent. This is 

 the highest result ; for the lowest it will be found that the 4£ inch ball (fourth 

 experiment) has a variation of 7 - 5 per cent, above, and 1*2 per cent, below, or a 

 total variation of 8 - 7 per cent. 



The diagrams read the reverse way should furnish an indication of the change 

 in passing from the liquid to the solid; and the author describes phenomena 

 observed in the cooling of iron castings, which confirm this view. 



The following conclusions may be inferred from these experiments : 



That when in the solid state cast iron is at its greatest density. 



"When in the plastic state, immediately before liquefaction, it is at its least 

 density. 



That the liquid state is intermediate in density, being much nearer in degree to 

 the solid than to the plastic condition. 



The writer is now completing the construction of a more elaborate instrument 

 to effect the object he has in view. The index of the spring balance is made to 

 move vertically in a straight line. A pencil attached to the index presses on a 

 piece of paper coiled round a cylinder five inches in diameter, which revolves on a 

 vertical axis by means of clockwork, arranged so that the surface of the paper on 

 the cylinder moves at a uniform speed, while the pencil follows the change of 

 volume in the ball of metal under examination. A much more accurate diagram 

 should by this means be formed than has been possible by the means at first 

 adopted by the author. 



Note. — For a more complete account of these experiments see a paper by the 

 same author on ' Some Physical Changes in Iron and Steel at High Temperatures/ 

 read before the Iron and Steel Institute at Liverpool, September 1879. 



