596 MR. T. WRIGHTSON ON IRON AND 
spherical moulds of dried loam were made 15°09 and 15°28 inches diameter 
respectively. Into these, molten iron was poured, in the former case, Cleveland white 
iron, and in the latter, Cleveland grey iron. A few minutes after the iron was run, 
the top of the mould was raised and the diameter of the congealed surface measured 
with callipers. This was continued at intervals of time, and the diagram, fig. 2, 
shows the gradual increase of diameter of the grey and white iron balls as they cooled. 






Fig. 2. 
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Diagram showing progressive increase of diameter and final contraction of grey and white balls, 
15 inches diameter. 
The large size of the balls made the cooling a slow process, and the horizontal 
line representing time could not conveniently be extended in a diagram, but the final 
diameter, when the balls, after ten or twelve hours, became cold, is shown. The 
general result is a qualitative confirmation of the previous experiments, although not 
quantitative, as the early consolidation of the outer layers of metal prevents the 
free expansion of the interior. 
These experiments were made in 1879-89, and proved that grey iron and white iron 
possessed the property of expanding when cooling, and contracting when heating, 
within a range of temperature approaching the melting points, and to an extent 
near that found in the case of water, which in solidifying expands in volume 9°3 per 
cent., while grey iron expands nearly 6 per cent., and white iron even more; the 
approximation appearing to indicate that the phenomena were of the same order. 
These facts led me to suggest that the phenomena of regelation and welding 
