The questions of law presented in this case may be conveniently considered in a somewhat different order from that in which they, arose at the trial and are stated in the bill of exceptions.
1. The extent of the invention claimed by the defendant in ais patent must be determined by the specification of the patent .tself. It is a question of construction, which in the case of letters patent, as of all other written contracts, is a question for the court. If any part of the invention thus claimed is not new, the patent may be invalid as claiming too much. Minter v. Mower, 1 Nev. & P. 595 ; S. C. 6 A. & E. 735 ; 1 Webst. Pat. Cas. 138, 142. But the testimony of the expert called as a witness for the defendant was not introduced to show a want of novelty, affecting the validity of the patent, but only upon the question of construction, to limit the meaning of the language of the specification. It was therefore rightly disregarded by the court. Winans v. New York & Erie Railroad, 21 How. 88,
*752. The defendant, at the beginning of his specification, describes the nature of his invention as consisting in a seat, set and moving upon “ a cross shaft or hinge ” in such a manner that the front part of the seat can be raised to afford room in passing in, out or by, and form a lever that, when brought to a level, strikes and is supported by a stop in the rear of the fulcrum. In the further description given to enable others to use the invention, he shows that the fulcrum or centre of motion, by which the seat is suspended on or attached to the standards or frame of the chair, may consist either of a shaft extending across the seat or of a pin on each side. And what he finally claims as new and useful is “a swinging or lever seat, set and moving upon a cross shaft or hinges, and sustained when in use by a stop or stops so disposed as that the rear portion of the seat comes in contact with said stop or stops when the seat is turned down, substantially as herein set forth.”
In short, the invention, as claimed by him, consists in a tilting seat, supported on each side upon a pivot, and which is kept in place, under the weight of the sitter upon the front, by one or more stops bearing down upon the seat behind the pivot; and this whether the pivot or fulcrum on either side is or is not part of a continuous shaft. The instruction given to the jury as to the extent of the invention claimed by the defendant was therefore correct.
Such being the legal construction of the defendant’s patent, it was not limited to any particular form or arrangement of the several parts; and the jury were rightly instructed that a chair by which the same or substantially the same results were accomplished in the same manner or by the same means, or substantially so, was an infringement, notwithstanding differences in the form, appearance and arrangement of the parts. Minter v. Wells, 1 Webst. Pat. Cas. 127 ; S. C. 5 Tyrwh. 163 ; 1 C., M. & R. 505. Winans v. Denmead, 15 How. 330. Odiorne v. Winkley, 2 Gallis. 51. Blanchard v. Beers, 2 Blatchf. C. C. 411.
3. The further instruction, that if the later patent embraced, as an essential part of its device, that for which the first patent was issued, it would be not less an infringemónt, even if it contained something additional which was itself patentable as an improvement, was equally correct. Foster v. Moore, 1 Curtis, 279, 292. McCormick v. Talcott, 20 How. 402, 405.
*764. The question whether the Koechling patent was an infringement of the defendant’s was rightly submitted as a question of fact to the jury. Hawkes v. Remington, 111 Mass. 171, and cases there cited.
5. By an indenture of March 23, 1869, the defendant granted to the plaintiffs “ the exclusive liberty, license, power and authority to make, use and sell within and for the United States, for and during the unexpired term of said patent, the said improvement as patented under and by said letters patent, excepting only the adaptation of said improvement to camp chairs and school furniture; ” and covenanted that he would not grant licenses to any other person to make and sell chairs of the character included in the license to the plaintiffs; and that he would at his own expense institute or cause to be instituted legal proceedings. against all infringers of said letters patent, and exercise due diligence in' such proceedings so as to restrain them as promptly as possible, in order that the plaintiffs might enjoy the exclusive privilege of making and selling the chairs in question without competition.
The declaration in the present case alleges two breaches of the covenants of the defendant in the indenture; the one by granting a license to Koechling, and the other by neglecting to sue him as an infringer.
The agreement of May 7, 1869, by which the defendant, in consideration of the payment of a certain sum annually by Koechling, agreed not to make any claim on him for any alleged infringement, was essentially a license. Its character is not affected by the false recital therein that the previous action against Koechling had been decided in his favor on the merits ; it appearing that the entry of judgment in that action was made by an arrangement between the counsel of the parties thereto, and without any assént, knowledge or control of these plaintiffs. It was therefore rightly ruled that if the Koechling chair was an infringement of the defendant’s patent, the agreement between the defendant and Koechling constituted a breach of the first covenant sued on.
6. The grant from the defendant to the plaintiff, contained in the indenture of March 23, 1869, not amounting to an assignment, either of the whole patent or of an undivided part thereof, *77for the territory described therein, was a mere license, and gave the plaintiffs no interest in the patent itself, and no right to sue in their own names for any infringement thereof. Gayler v. Wilder, 10 How. 477. It might authorize the licensees to assert, by action in the name of the licensor, any right which he had in respect to the subject of the license, and prevent him from releasing any action so brought by them. Goodyear v. McBurney, 3 Blatchf. C. C. 32. Goodyear v. Bishop, 4 Blatchf. C. C. 438. But after he had executed the release under seal to Koeehling, neither he, nor his licensees in his name, could institute or intervene in an action against Koeehling. Upon this point, therefore, the rulings at the trial were correct.
7. This indenture contains no express covenant that the patent is valid, nor even a recital that the defendant is the inventor of the subject thereof. The recital is only of the issue of letters patent to the defendant, and the plaintiff’s desire of obtaining a license to use the improvement so patented. The grant is of a license to make, use and sell “ the said improvement as patented under and by said letters patent.” The covenants are, 1st, not to license other persons; and 2d, to institute and prosecute legal proceedings against all who infringe the patent. The words “ in order that the said James L. Jackson & Brother may enjoy the exclusive privilege of making and selling the chairs in question without competition” do not constitute an independent covenant, and are not declared on as such. They are inserted by way of stating the purpose of the covenant to which they are annexed. Reading them in connection with that covenant and with the rest of the instrument, we are all of opinion that they do not amount to a warranty by the licensor that the licensees shall enjoy the privilege of making the chairs in question against persons not claiming rights under the licensor.
The cases of Bowman v. Taylor, 2 A. & E. 278 ; S. C. 4 Nev. & Man. 264 ; and Bliss v. Negus, 8 Mass. 46, cited by the learned counsel for the plaintiffs, do not appear to us to support the opposite conclusion. In Bowman v. Taylor, the action was by the licensor against the licensee, the indenture contained a distinct recital that the licensor had invented the improvements in question; and the decision was put upon that ground, and, by the earlier and the later English authorities, could hardly be *78sustained upon any other. Hayne v. Maltby, 3 T. R. 438 ; Smith v. Scott, 6 C. B. (N. S.) 771, 782. In Bliss v. Negus, the deed from the plaintiff recited the issue of a patent securing to the patentee the exclusive right to the improvement in question, and its assignment to the plaintiff, and purported to assign to the defendant all the right and privilege so conveyed, with a covenant to warrant and defend the same against the claims of any other persons; and yet the court was of opinion that this deed contained no covenant which could sustain an action by reason of the invalidity of the patent for want of novelty, and held that, if the patent was invalid for that cause, the deed to the defendant constituted no consideration for a promissory note.
8. Upon the question of the correctness of the ruling excluding the evidence offered by the defendant to show that his patent was invalid, there is a difference of opinion among the judges, and the court desires the assistance of a further argument of counsel upon that question, as well as upon the instructions to the jury on the question of damages, before deciding the case.
Case to stand for further argument accordingly.
The case was reargued on these points by the same counsel in November, 1875.
Gray, C. J.The question to which the strength of the second argument has been directed is thus stated in the bill of exceptions : “ The defendant offered evidence tending to show that his patent was invalid on the ground of want of novelty, for the purpose of showing that he was not obliged to prosecute Koechling, or that, if he did do it, it could be of no benefit to the plaintiffs, because such suit could not be maintained. This evidence was excluded by the court, for the reason that it was incompetent for the defendant to prove his patent invalid.”
Upon the first argument of this question, the very able and learned judge who presided at the trial adhered to the opinion which he had expressed to the jury, and one of the other judges was inclined to concur with him. But upon further consideration all the surviving judges are of opinion that the evidence should have been admitted, as affecting the measure of the dam ages which the plaintiffs were entitled to recover.
*79The ruling at the trial evidently proceeded upon the ground that the defendant was estopped, either by deed or in pais, to show that his patent was invalid.
But to constitute an estoppel by deed, a distinct and precise assertion or admission of a fact is necessary. Right v. Bucknell, 2 B. & Ad. 278. Wight v. Shaw, 5 Cush. 56, 64. Miller v. Ewing, 6 Cush. 34. Campbell v. Knights, 24 Maine, 332. Pike v. Galvin, 29 Maine, 183. Pelletreau v. Jackson, 11 Wend. 110, 117 ; S. C. nom. Jackson v. Waldron, 13 Wend. 178. Brown v. Jackson, 3 Wheat. 449. Van Rensselaer v. Kearney, 11 How. 297, 325. We have already decided that the indenture contains no warranty or covenant that the defendant is the inventor of the improvement in question. It does not state that an exclusive privilege is owned by the defendant or conveyed to the plaintiffs. The defendant merely covenants that he will diligently proceed against infringers, so that the plaintiffs “may enjoy the exclusive privilege of making and sélling the chair in question without competition,” and that he will not grant inconsistent licenses’. If he does grant such licenses, or fails to bring such suits, it is a breach of contract, for which he is liable in damages. But proving that his patent was invalid does not deny anything that he has ever asserted.
Nor does the case show any estoppel in pais. The defendant does not appear to have made any representation as to the validity of the patent, otherwise than as expressed in the indenture. To constitute an estoppel in pais, it is essential that the defendant should, by word or act, have represented the fact to be different from what he now attempts to show it to have been. Mere disappointment in expectation, or breach of promise or covenant relating to the future, cannot constitute an estoppel in pais. Langdon v. Doud, 10 Allen, 433. Jorden v. Money, 5 H. L. Cas. 185.
It was argued that this case was analogous to those in which it has been held that a licensee, continuing to enjoy the privilege of his license, is estopped to deny the validity of the patent, when sued for the royalty. Kinsman v. Parkhurst, 18 How. 289, 293. Lawes v. Purser, 6 E. & B. 930. Noton v. Brooks, 7 H. & N. 499. Crossley v. Dixon, 10 H. L. Cas. 293. But the distinction is obvious. In those cases, the licensee is held to pay *80the exact compensation stipulated for. In the present case, the licensor does not undertake to avoid the payment of anything which he has agreed to pay; but, the damages for the alleged breaches of his covenants not being ascertained or liquidated by the terms of the contract, he offers to prove the invalidity of the patent, , as bearing upon the question what the amount of such damages really is.
So far as the plaintiff relied upon the covenant to prosecute infringers, the evidence offered was admissible, because, if the patent was invalid for want of novelty, no damages could have been recovered for infringing it, and the attempt to recover such damages could have produced no beneficial result, either to the patentee or to any one claiming rights under him, and therefore the plaintiffs would suffer no injury from the failure of the defendant to prosecute Koechling.
Upon the other breach of covenant, by licensing Koechling, the evidence of the invalidity of the patent would not be equally conclusive, but we are of opinion that it was competent. It would be for the jury to determine its weight, and, taking it into consideration with all the other evidence in the case, to decide whether and to what extent the defendant’s act in licensing Koechling had excited competition injurious to the plaintiffs’ business under their license from the defendant.
Upon either branch of the case, the plaintiffs can recover ' damages only for the injury which they prove that they have suffered by the defendant’s acts in violation of his covenants. The fraudulent character of those acts, and the difficulty of proving such damages, cannot change the burden of proof or the measure of the defendant’s liability.
Exceptions sustained.