Cast SteeL 
415 
it with a mixture of equal parts of lime and scoriae. Mr. 
Mushet says that 875 grains of cold short iron when melt- 
ed by itself in a covered crucible formed a perfect button 
covered by a thin film of brown glass. The metal weigh- 
ed only 805 grains, and instead of being cold-short, was 
now found to have acquired the opposite fault of being 
hot- short, it was extremely soft and ductile. In these ex- 
periments it may be said that the metal being brought to 
a state of quiet fusion, the phosphat of iron either entirely 
or at least for the most part separated in the form of glass 
from the reguline portion. But as all the above pheno- 
mena may be accounted for equally well upon the suppo- 
sition that the cold-short quality is owing simply to the 
mixture of oxyd of iron with the metal, it would be use- 
less to speculate further on the subject till a sufficient 
number of accurate analyses have been performed to di- 
rect our investigations. The hot- short quality appears to 
be occasioned by the admixture of some substance which 
enters into fusion at a low red heat, and thus destroys 
the tenacity of the iron through which it is diffused : 
hence this variety of iron cannot bear the hammer at a 
red heat, though when the temperature is raised to the full 
welding point, the effect of this unknown substance is 
counteracted by the tenacity which the particles of iron 
then acquire. This substance has been by some suppos- 
ed to be carbon, but this is inconsistent with the e treme 
softness which always characterises hot- short iron : for 
the same reason it cannot be phosphorus. The effects 
are more like those of a metallic body ; and lead, arse- 
nic, copper, and zinc may be each suspected with almost 
equal probability. In some varieties of hot-short iron, 
especially those made with coke, the fragility increases 
with the increase of temperature, and they are whollv in- 
capable of welding : this probably arises from a large ad- 
mixture of the same substance, whatever it be, to which 
