594 MR. T. WRIGHTSON ON IRON AND 
motion of the pencil, when combined with the horizontal motion of the paper on 
the revolving cylinder, produces the curve of volume. 
The first operation is to hang a rod on the spring balance with a piece of wrought 
iron at the end, which is an exact facsimile of that part of the shank of wrought 
iron fixed in each ball which will eventually protrude above the molten iron when 
the ball is submerged. ‘This weight brings down the spring balance to indicate from 
1 to 2lbs. The cylinder is then thrown out of gear and moved round, the pencil 
making a straight zero line, which represents the position when the cold and molten 
iron have the same specific gravity. The smal] piece of iron representing the upper 
part of the shank is then removed, and the actual ball put in place. This ball has 
been accurately weighed before, and its specific gravity also taken. Hanging it 
on the spring balance brings the index below the zero or equilibrium line. The ball 
is now lowered into the metal, the clockwork having been previously put in action. 
A diagram is thus drawn during the heating and melting of the ball, of which the 
vertical ordinates represent change of volume in ounces of increased displacement, and 
the horizontal element represents time in minutes. 
A number of diagrams were taken with 3-inch and 4-inch diameter balls, the specific 
gravities of which had previously been ascertained. The general character of these 
is shown on fig. 1, which is one of the numerous diagrams taken, in which B, F 
represents the liquid volume, and A, B, C, D, E, F the changing volume in passing 
from the solid to the liquid state. 
Fig. 1. 
o 3 
[x (4 8 
3 
~ is) 
~ 
as) 
2 
3 
vy 
SESE ck ae LTS a EM oe NR NN 1 1 
6 Min. 6 5 3 7 

4-inch ball of No. 4 foundry iron (Cleveland) ; poured from very hot 
metal; immersed in No. 4 foundry iron. 

Weight of ball and immersed part of stalk . . . . 132 on. 
Specific gravity of ball, and immersed part of stalk . 6:95 
Maxcimumysiniin pet ec teases. eae een OZ 
Maximimyt oabinovetiect amir) ii-tieetna enlist aemnLe HA 
Specific gravity of fluid iron = eee = 6°84. 
Specific gravity of plastic metal = a = 6°32 
Between A and B, fig. 1, the average density of the ball changes, until at B it has 
