truth, law, property, or quality of matter is appropriated, to the extent of all other applications which a jury, under the guidance of the law, shall consider as a piracy of the former.

In coming to this result, the patent law establishes no monopoly beyond the fair fruits of actual invention. It protects the real inventor in the enjoyment of what he was the first to produce; and it recognizes, as substantive inventions, all changes which may be produced in the same line of experiment, or in the same department of labor, which introduce new characteristics, new results, or new advantages not embraced by the former invention. "As long as the patent law exists at all to afford protection to the labors of ingenious men, it must proceed upon this fundamental principle. It is now too late in the history of civilization to question the policy of this protection, which forms a prominent feature in the domestic polity of every nation which has reached any considerable stage of progress in the arts of civilized life.

It will be seen in the following pages how far these views have prevailed in the administration of the patent law, in England and America, and to what extent they have been developed in particular cases. They have led, in the construction of patents in England, to a somewhat different spirit from that which formerly animated the courts of law; for, formerly, the judges exercised their ingenuity to defeat every patent that came before them, if it could by possibility be defeated. This was done upon the notion, that a patent is the grant of a privilege against common right; and hence some judges were in the habit of saying that they were "not favorers of patents." But within the last forty years a different view has been adopted; the more just and liberal doctrine has been acted upon, that public policy requires the encouragement of the inventive powers of ingenious men, and that this policy is supported by every consideration of justice. The

consequence has been, that the patent law has made greater advances, in England, within the last forty years, towards a consistent and admirable system of justice, than it has ever made before during the whole period that has elapsed since the enactment of the Statute of Monopolies.

In America, the more liberal policy has always prevailed, from the time when patent rights came under the protection of the general government; and the rule has been often laid down by the courts of the United States with a good deal of strength,— as if in obedience to the spirit of the Constitution, that patents ought to be construed liberally. Perhaps the general language which has thus been employed by judges would lead to the conclusion, that the leaning of the courts is, systematically, in favor of the patentee and against the public; but this tendency has not been exhibited so strongly, in practice, as to derange the administration of the law.

The truth is, a patent should be construed as, what it really is, in substance, namely, a contract or bargain between the patentee and the public, upon those points which involve the rights and interests of either party. These points relate to the extent of the claim, and to the intelligibility of the description for the purposes of practice. The first is universally a question for the court; the last is generally a question for the jury, under the direction of the court. As to the first question, the extent of the claim presents at once the relations between the patentee and the public; for it involves, among other things, the inquiry, whether the patentee has claimed anything beyond what was really his own invention. If, in representing himself as the inventor of the thing for which he has asked and received a patent, the inventor has included in his claim anything that existed before, he has made a representation untrue in point of fact; and whether he has made this representation intentionally or unintentionally, the grant of the patent proceeds upon it,

and, if it is not true, the grant is not supported by an existing consideration, such as the inventor has represented it to be. In determining this question whether the patentee has really included in his claim something which he did not invent, two things are to be ascertained; first, whether he makes use of anything not new; and second, whether that thing, according to the fair import of ⚫ his language, is represented to be a part of the invention which he claims to have made. The fact of whether he makes use of anything not new, is a question depending upon evidence, if it is not manifest on the face of the description. It is upon the second branch of the inquiry, whether the old thing is really included in the claim of invention, that the true principles of construction have to be applied. Recollecting, on the one hand, that if the public have been misled, the patent ought not to stand, because of the false representation; and, on the other hand, that a construction, which will destroy the patent, ought not to be adopted lightly, it would seem to be the true rule, to construe the patent fairly, and so as to arrive at the just import of the language in which the claim is set forth. But if, after applying this rule, the question remains doubtful whether the claim is not broader than the invention, then the rule should be adopted, in favor of the patent, that the patentee is to be presumed to have intended to claim no more than he has actually invented. Every patentee is presumed to know the law, and to know that if he includes in his claim something which he has not invented, his claim is void. Such a claim is a kind of fraud upon the public, with whom the applicant offers to enter into a contract, when he asks for his patent; and fraud is never to be presumed, but is always to be proved. The rule, therefore, which presumes, in doubtful cases, that the patentee intended to claim no more than his actual invention, is founded in a maxim of general application to contracts; and it will be seen, in

practice, that it has no tendency to support patents which ought not to be supported, or to encourage loose and sweeping claims. In all cases which are not doubtful, where it is manifest that the claim admits of no construction but that which makes it too comprehensive to be valid, this rule will have no application. The imposition attempted will be apparent, and the fraud-so far as it is a fraud-will not require to be presumed, but will stand proved.

This rule, although not distinctly announced by any of our courts, has much to support it, in several authorities. Judges would seem to have had a rule of this kind in view, when they have construed patents under the guidance of the maxim, ut res magis valeat, quam pereat. The use of this maxim, which has often furnished the spirit of construction in particular cases, implies that the claim is to be supported, if it can be done without a violation of principle. But the rule has been distinctly applied, in England, by the Court of Common Pleas, that the patentee is not to be presumed to have intended to claim things which he must have known to be in common use, although, in describing his invention, he has not expressly excluded them from the claim. There are also cases, in this country, where it has been held not to be necessary to use words of exclusion, in reference to details, where it appears from the whole description of the invention that the new is capable of being distinguished from the old.

The same rule, in cases of doubt, should be applied to the construction, where the question is, whether the patentee has claimed as much as he has invented; that is to say, the specification should be so construed as to make the claim coextensive with the actual invention, if this can be done consistently with principle.

But beyond this rule it is not necessary or wise to go, in the construction of patents. By giving the patentee

the benefit of this presumption, in cases of doubt, the doubt will be removed, and the patent will remain good for the real invention. But where there is no room for doubt, and no occasion for the application of the rule, but the claim is manifestly broader or narrower than the real invention, there can be no hesitation about the judgment to be pronounced, especially since the provisions of our law, by which a patent may remain valid pro tanto, after the real invention of the party has been judicially ascertained.