226 Gold Coinage. (April, 
weighed by automatic machinery, which separates those 
which are of wrong weight from those which come within 
the limit of error permitted by law, and the former are sent 
back to the melting-pots to go all through the processes 
again. At various stages in these operations the gold has to 
be assayed by the Chemist of the Mint. The melting and 
rolling processes are of much the same character as making 
rails for railways, only the process with regard to gold is 
more delicate and exact; there are also special precautions 
to prevent loss of metal. 
The ingots are assayed when they first reach the Mint, 
and then the amount of fine gold or of copper to be added to 
them, to bring them to the standard required by law, is cal- 
culated by a rule-of-three sum. Copper is used as the alloy. 
About 1200 ozs. of gold and alloy are sent to each melting- 
pot, and this operation is called ‘‘ potting the ingots.” It is 
advisable to consider the various processes in greater detail, 
and commencing with the operation of melting, it may be 
observed that there are seven furnaces at the Mint which are 
used for the fusion of the gold, each 1 foot square and 2 feet 
deep to the top of the bars. The melting-pot is made of a 
mixture of Stourbridge clay and plumbago ; it is 9+ inches 
deep and 7 inches in inside diameter at the top. The potis 
placed in the furnace on a bottom which rests on two bars, 
then it is covered by its muffle and lid, and surrounded by 
fuel, which gradually heats the pots to redness; the ingots 
are then placed in it, and the alloy added through a funnel. 
When the whole mass is melted, the foreman stirs it witha 
rod made of plumbago and clay, and can tell by the feel 
when the metal reaches that particular state of viscosity 
which causes it, when moulded, to form a workable bar. 
The firing is then poked out, the muffle and lid of the pot 
removed, the pot lifted out with a tongs, and by suitable 
means supported by a loop of iron and a cord hanging from 
the ceiling. Before the melting, pieces of charcoal are 
placed in the bottom of the pot, for the purpose of reducing 
any oxide which may be present in the alloy, for copper will 
dissolve oxide of copper, and oxide of copper often makes the 
gold very brittle. This charcoal afterwards floats on the 
top of the melted gold, and a piece of stick held at the 
mouth of the pot whilst pouring into the moulds, stops the 
charcoal but not the gold. Each pot of gold forms seven 
bars. The moulds are made of cast-iron, and a large 
number, about twenty, of these moulds are mounted on a 
tram, which can be moved from one part of the building to 
another on rails. Each bar is marked to show from what 
