892 
ME. HOD&KIXSOiS^’S EXPEEBIEXTAL EE.SEAECHES 
To obtain some additional information as to the distribution 
of the metal in a large casting, one was formed 9 inches square 
and 12 inches long, or upwards. It was cast erect from Der- 
went iron. No. 1, and was then placed upon a slotting machine, 
and cut directly across in the middle. It was found, however, 
that there was a hole in the centre, about f inch or 1 inch in 
diameter ; transverse slices were therefore cut, one from above 
and one from below the central defective piece ; these two 
slices, each 9 inches square and 1 inch thick nearly, were 
divided from one side to the other, passing through the centre 
of each, into nine equal parts, and from each part cy lin ders were 
cut, all of the same diameter, | inch, and length 1^ inch, four 
on each side of the central one. See figure annexed. 
TOP 
Upper Slice of Mass. Lower Slice of Mass. 
Mark on 
Cylinder. 
Diameter of 
Ditto. 
Crushing weight 
of Ditto. 
Mark on 
Cylinder. 
Diameter 
of Ditto. 
Crushing weight j 
of Ditto. 1 
inch. 
lbs. 
inch. 
Ihs. 
8 
•748 
31512 
8 
•748 
30571 
6 
•747 
32923 
6 
•748 
31512 
4 
•748 
31042 
4 
•749 
32924 
2 
•747 
37157 
2 
•748 
30571 
A 
•748 
37627 
B 
•748 
29160 
1 
•748 
39980 
1 
•748 
30101 
3 
•748 
39039 
3 
•748 
32924 
5 
•748 
35275 
5 
•749 
32924 
7 
•748 
31983 
7 
•749 
33394 
The iron in this mass seems to have been extremely irregular, particularly in the upper 
part of the casting. In the part marked B, which was cast under the greater head of 
metal, the iron from three divisions near the centre, or one-third of the distance across, 
was crushed with somewhat less weight than that from the external part, the greatest 
difference being from 29160 at the centre, to 33394 at the side. The mean resistance 
of the three central cylinders in this slice is 29944 lbs., and of the six external ones 
32375 lbs., the difference being much less than in the iron of the smaller castings tried. 
The iron in the upper part, marked A in the figure, being cast under a less head of 
metal than the former, and floating at the top of the softer metal below, was con- 
siderably stronger than the other. The central portion of this was, contrary to all our 
preUous experience, much harder than the rest, and varied from 3I5I2 and 31983 at 
the sides, to. 37627, 39039 and 39980 near to the middle. To explain this strange 
anomaly in the absence of other knowledge, it seems not improbable that some addi- 
tional heavier metal had been poured into the top part of the mould, when that in the 
lower part had in some degree solidified. 
From the experiments upon the two last castings, which are on a larger scale than 
those which precede them, it appears that the difference of hardness between the 
external and internal parts of a large casting is much less than in a small one, and may 
frequently be neglected. 
