If an invention is old, it is old regardless of any new purpose to
which it is put. It is no invention to put a machine to a new use. If
an inventor contrives a meritorious machine for the production of
coins or medals, his invention is lacking in novelty if it should
appear that such a machine had before been designed as a soap press,
and this fact is not altered by any merely structural or formal
difference, such as difference in power or strength, due to the
difference in duty. The invention resides in the machine and not in
the use of it. If the soap press is covered by an existing patent,
that patent is infringed by a machine embodying that invention,
regardless of whether the infringing machine be used for pressing soap
or silver. And it is no invention to discover some new capacity in an
old invention. An inventor is entitled to all the capacities of his
invention.