The plaintiffs in error were plaintiffs in the Circuit Court in an action for an infringement of the patent of A. B. Wilson, for a deeding device in sewing-machines. They recovered a judgment for one hundred and twenty-five dollars, but insist that they were entitled to a much larger judgment, of which they were deprived by the rulings of the court in the progress of the trial.
The objections to these rulings will be considered by us under three heads, to which all the assignments of error relate.
1. As to the measure of damages.
Evidence was given tending to prove that plaintiff had advertised to sell their machines, and had actually sold a shopright to use one of them for twelve dollars and fifty cents, and had given a verbal license to another person to use an old machine in his house for five dollars, but afterwards refused to sell or license for Franklin County, and told defendants they desired to retain the use of the machine as a close monopoly. Evidence had also been given as to profits made by defendants. On this testimony they asked the court to instruct the jury that 'this testimony was not sufficient to change the rule of damages from the profits which plaintiffs would have made if they had not been embarrassed by the interference of the defendants, to a mere license-price, because they do not establish a customary charge for the right to use the invention in Franklin County,' which the court refused.
There are two sufficient objections to this prayer:--
First, In cases where profits are the proper measure, it is the profits which the infringer makes, or ought to make, which govern, and not the profits which plaintiff can show that he might have made.
Second, Profits are not the primary or true criterion of damages for infringement in an action at law. That rule applies eminently and mainly to cases in equiry, and is based upon the idea that the infringer shall be converted into a trustee, as to those profits, for the owner of the patent which he infringes,-a principle which it is very difficult to apply in a trial before a jury, but quite appropriate on a reference to a master, who can examine defendant's books and papers, and examine him on oath, as well as all his clerks and employees.
On the other hand, we have repeatedly held that sales of licenses of machines, or of a royalty established, constitute the primary and true criterion of damages in the action at law.
No doubt, in the absence of satisfactory evidence of either class in the forum to which it is most appropriate, the other may be resorted to as one of the elements on which the damages or the compensation may be asertained; but it cannot be admitted, as the prayer which was refused implies, that in an action at law the profits which the other party might have made is the primary or controlling measure of damages. Packet Company v. Sickles, 19 Wall. 617.
2. A paper was introduced in evidence by defendants, signed Sarah Burdell, authorizing H Crary, for the full term of four years, to sell, use, and grant to others the right to use, in said county of Franklin, A. B. Wilson's sewing-machines. It was agreed that the paper should have the same effect as if signed by William Burdell and the other plaintiffs in whom the title was when it was executed. It is too long a paper to insert here, but will be given verbatim by the reporter; and its true construction is the foundation of the alleged error of the court in admitted it, and also in admitting a receipt given to the defendants by said Crary for the use of four of the machines for which they were sued.
It is claimed that the instrument is but a power of attorney revocable at the pleasure of the maker, and that it was so revoked before the receipt given in evidence was executed by Crary.
But we are of a different opinion. We think the instrument is a contract. That Crary acquired rights under it for four years, which, whether he may have so acted or not as to enable plaintiffs to have it rescinded or set aside in a suit in chancery, could not be revoked at their mere volition; and that these rights were such that his receipt for the use of the four machines mentioned in it was a valid acquittance of any claim for the same thing by plaintiffs in this suit.
It is said that the court erred in admitting the receipt in bar of the action, because it was executed after the suit was brought, and could not be so used without a special plea setting it up.