combinations of elements within the sub-machines, might be capable of
utilization in other situations than that comprehended by the main
machine, it becomes important that the inventor be protected regarding
the sub-machines and the minor useful combinations. Claims may be
drawn for the combination constituting the main machine, other claims
may be drawn for the combinations constituting the operative
sub-machines, and claims may be drawn covering the minor useful
combinations of elements found within the sub-machines. Each claimed
combination must be operative. But secondary claims cannot be made for
sub-machines or sub-combinations which are for divisional matter or
matter which should be made the subject of separate patents.


MECHANICAL EQUIVALENTS.

Where an inventor produces a new mechanical device for the production
of a certain result, he can often see in advance that various
modifications of it can be made to bring about the same result, and
even if he does not see it he may in the future find competitors
getting at the result by a different construction. He analyzes the
competing structure, and determines that "it is the same thing only
different," and wonders what the legal doctrine of mechanical
equivalents means, and asks if he is not entitled to the benefits of
that doctrine, so that his patent may dominate the competing machine.

An inventor may or may not be entitled to invoke the doctrine of
mechanical equivalents, and the doctrine may or may not cause his
patent to cover a given fancied infringement. If an inventor is a
pioneer in a certain field, and is the first to produce an
organization of mechanism by means of which a given result is