ord _aes_ signifies either pure copper or bronze,
not brass, but the Romans comprehended a brass compound of copper and
zinc under the term _orichalcum_ or _aurichalcum_, into which Pliny
states that copper was converted by the aid of cadmia (a mineral of
zinc).

In England there is good evidence of the manufacture of brass with zinc
at the end of the 16th century, for Queen Elizabeth by patent granted to
William Humfrey and Christopher Schutz the exclusive right of working
calamine and making brass. This right subsequently devolved upon a body
called the "Governors, Assistants and Societies of the City of London of
and for the Mineral and Battery Works," which continued to exercise its
functions down to the year 1710.

When a small percentage of zinc is present, the colour of brass is
reddish, as in _tombac_ or red brass, which contains about 10%. With
about 20% the colour becomes more yellow, and a series of metals is
obtained which simulate gold more or less closely; such are _Dutch
metal, Mannheim gold, similar_ and _pinchbeck_, the last deriving its
name from a London clockmaker, Christopher Pinchbeck, who invented it in
1732. Ordinary brass contains about 30% of zinc, and when 40% is
present, as in _Muntz, yellow_ or _patent_ metal (invented by G.F. Muntz
in 1832), the colour becomes a full yellow. When the proportion of zinc
is largely increased the colour becomes silver-white and finally grey.
The limit of elasticity increases with the percentage of zinc, as also
does the amount of elongation before fracture, the maximum occurring
with 30%. The tenacity increases with the proportion of zinc up to a
maximum with 45%; then it decreases rapidly, and with 50% the metals are
fragile. By varying the proportion between 30 and 43% a series of alloys
may be prepared presenting very varied properties. The most malleable of
the series has an elongation of about 60%, with a tensile strength of
17.5 tons per sq. in. Increase in the proportion of zinc gives higher
tensile strength, accompanied, however, by a smaller percentage of
elongation and a materially increased tendency to produce unsound
castings. The quality of copper-zinc alloys is improved by the addition
of a small quantity of iron, a fact of which advantage is taken in the
production of Aich's metal and delta metal. Of the latter there are
several varieties, modified in composition to suit different purposes.
Some of them possess high tensile strength and ductili