ple of
ingenious talent, with the understanding that the results of such
talent developed during the employment shall inure to the benefit of
the employer, there is only one safeguard, and that is to found the
employment on a contract unmistakably setting forth the understanding.

NEW PURPOSE.

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.

COMBINATION CLAIMS.

Many people have an erroneous notion regarding patent claims, and
consider the expression "combination" as an element of weakness. The
fact is, that all mechanical claims that are good for anything are
combination claims. No claim for an individual mechanical element has
come under my notice for many years and I doubt if a new mechanical
element has been lately invented. All claims resolve themselves into
combinations, whether so expressed or not. Combination does not
necessarily imply separateness of elements. The improved carpet tack
is after all but a peculiar combination of body and head and barbs.
The erroneous public contempt for combination claims is based upon the
legal maxim, that if you break the combination you avoid the claim and
escape infringement, and this legal maxim should be well understood in
formulating the claims. If the claim calls for five elements and the
competitor can omit one of the elements, he escapes infringement.
Therefore, the claim is good only when it recites no elements which
are not essential.

Many inventors labor under the delusion that a claim is strong in
proportion to the extent of its array of elements. The exact opposite
is the truth, and that claim is the strongest which recites the
fe