Brass . 107 
guishable from silver. The inferior kinds are still white, 
but with a brassy yellow. 
The Chinese Petong is another fine, white, malleable 
alloy of copper, the composition of which is not exactly 
kno wn, but it contains a small portion of silver. Neither 
of the above metals are imitable by the common pro- 
cesses. 
According to Di2e, when the iron forms only of the 
mass it is still magnetical, but not so when it is only a* 
bout™. Iron does not whiten copper so much, in equal 
quantities, as tin does, and still less than arsenic. 
[1 Aikin^ 346. 
Bronze , the name of a mixed metal, which the ancients 
employed for casting statues and other ornaments. Ac- 
cording to Vasari, the bronze of the Egyptians consisted 
of two-thirds of brass, and one of copper; and Pliny in- 
forms us, that the Greeks added to the brass one-tenth 
part of lead, and one-twentieth part of silver. 
In casting bronze figures, particular attention must be 
paid to the formation of the mould. The pattern from 
which the cast is to be made must have a mould made up- 
on it, with a mixture of one third of plaster of Paris, and 
two-thirds of brick- dust. Its thickness should be pro- 
portioned to the weight of the figure and small air-holes, 
opening upwards, should be made in the joints, to give 
free passage to the air, which is thrust out by the entrance 
of the metal. Over the interior surface of the mould there 
should be spread neatly a layer of clay of the intended, 
thickness of the metal. When this is done, the concavi- 
ty, which is bounded by the layer of clay, is to be filled 
with the composition of plaster of Paris and brick- dust al- 
ready mentioned, which will form the core. When the 
figure is long, strong bars of iron must be laid in the 
mould as a support to the metal figure, and round these 
the core must be ca^t The mould is then opened, the 
