304 
MINUTES OF PROCEEDINGS OF 
General Results. 
It will be seen by an inspection of the figures that the general effect is a 
maximum contraction of the metal about one inch above the water-line; and 
that this is the same whether the metal be immersed one-half or two-tliirds 
of its depth, or whether it be nine, six, or three inches deep. With wrought- 
iron the heatings and coolings could be repeated from fifteen to twenty times 
before the metal showed any signs of separation; but with cast-iron after the 
fifth heating the metal was cracked, and the hollow cylinder separated all 
round just below the water-line after the second heating. Cast-steel stood 
twenty heatings, but was very much cracked all over its surface. As respects 
the change of form of cast-iron and steel, the result was similar to that in 
wrought-iron, but not nearly so large in amount. The cast-iron did not 
return to its original dimensions, but the smallest diameter was about one 
inch above the water-line. 
Tin showed no change of form, there being apparently no intermediate 
state between the melting-point and absolute solidity. Brass, gun-metal, and 
zinc showed the effect slightly; but instead of a contraction just above the 
water-line, there was an expansion or bulging. 
The effect on wrought-iron is best seen in the solid cylinder (figs. 9 and 
10), where the displacement of particles just above the water-line appears to 
be compensated by the bulgings at the two extremities. 
The specimens of wrought-iron were submitted by Mr Able (Chemist to 
the War Department) to chemical analysis, and he informs me that he found 
nothing noteworthy in the composition of the metal; nor was there any 
appreciable difference in the specific gravity of the metal taken from different 
parts of the specimen. It appears therefore to be simply a movement of the 
particles whilst the metal is in a soft or semifluid state. 
The following is an account of the experiments, which were carried out 
under the superintendence of Mr Butter, draughtsman of the Boyal Carriage 
Department, to whom also I am indebted for the accompanying diagrams. 
The exact dimensions of each specimen before and after heating are given in 
a tabulated form at the end of the paper, to facilitate comparison. 
In figs. 22 and 23 the changes in form of the 9" cylinders (one immersed 
one-half, the other two-thirds its depth) are shown in section after every five 
heatings (half the full size). 
Experiment 1 . A 4ft. 2 in. hoop-tire of 3 inches breadth and fths 
inch in thickness (fig. 1) was heated and cooled by being immersed to half 
its depth in cold water five times, by which the effect shown in fig. 2 was 
produced. 
Fig. 1. 
One-eighteenth of full size. 
