§ 517. The tenth defence is more likely to be successful in the proof, than the ninth; because it may not only be based on the counterpart of the circumstances which underlie the latter, but also on other circumstances, where those do not exist. It has sometimes happened that an inventor, having sold an undivided half interest in his invention, has joined with his vendee in applying as joint inventor for a patent therefor. Such errors have been known to result from ignorance of the law; and such an error has been said to have occurred in one case, on account of a desire to give an important patent the benefit of the name of a more distinguished scientist than he who was the real producer of the subject of the claim. But in any case, it is certain that very clear and unequivocal evidence is necessary to support this defence.'

§ 518. The eleventh defence calls for proof that the letters patent contains less than the whole truth relevant to the invention, or that it contains more than is necessary to produce the desired result, and that the fault arose from intention to deceive the public. But positive and direct evidence is not required on the latter point. It is sufficiently shown by proof of any circumstances which satisfy the jury that such intention existed."

§ 519. The twelfth defence can be supported by no evidence except that of persons skilled in the art to which the invention pertains, or with which it is most nearly connected. A patent for a chemical composition or process cannot be overthrown, on the ground of an insufficient description, by the testimony of a mechanical expert; nor can a patent for an improvement of a loom be overthrown, on that ground, by the testimony of a machinist skilled only in printingpresses. If a description is sufficiently full, clear, concise,

1 Gottfried v. Brewing Co. 5 Bann. & Ard. 4, 1879; Butler v. Bainbridge, 29 Fed. Rep. 142, 1886; Consolidated Apparatus Co. v. Woerle, 29 Fed. Rep. 449, 1887; Schlicht & Field Co.

v. Sewing Machine Co. 36 Fed. Rep. 585, 1888.

2 Gray v. James, 1 Peters' Circuit Court Reports, 394, 1817; Dyson v. Danforth, 4 Fisher, 133, 1865.

and exact, to be effectually understood by any person skilled in that kind of machinery, or other subject of a patent, it is sufficiently so to meet this defence.'

§ 520. The thirteenth defence may sometimes succeed without any evidence outside of the letters patent themselves. It will, however, always be prudent to fortify the defence by the testimony of an expert who can show that the outward embodiment of the terms of the claim is uncertain in character or in extent.

§ 521. The fourteenth defence requires several items of evidence for its support. It requires proof, that one or more of the claims of the patent are void for want of embodying a subject-matter of a patent,' or for want of invention, or for want of novelty; and that the patentee has long known the facts which make it invalid in that behalf. No disclaimer is ever necessary, in the absence of all of the first three of these circumstances; and no delay to file one is unreasonable in the absence of the fourth. Indeed, proof of a necessity for a disclaimer, and of long-existing knowledge of the facts out of which that necessity arose, will not always sustain this defence; because delay to file a disclaimer is not unreasonable, so long as there is any reasonable doubt whether the known facts constitute a necessity for such a document.*

§ 522. The fifteenth defence can seldom be supported by evidence that the original patent was neither inoperative nor invalid by reason of a defective or insufficient specification; because inoperativeness, from one of these causes, exists whenever the patent does not secure and cover all the inventions which it indicated, suggested, or described, and which might lawfully have been claimed in it; and because, when not granted on account of such inoperativeness, re

1 Loom Co. v. Higgins, 105 U. S. 580, 1881.

O'Reilly v. Morse, 15 Howard,

121, 1853.

3 Revised Statutes, Section 4922.

4 Silsby v. Foote, 20 Howard, 290, 1857; Matthews t. Flower, 25 Fed. Rep. 834, 1885.

5 Wilson v. Coon, 18 Blatch. 532, 1880.

issues are generally granted on account of invalidity which arose by reason of a defective or insufficient specification, or by reason of a too extensive claim.' This defence therefore generally requires to be sustained by evidence showing that; whatever inoperativeness or invalidity on account of defective or insufficient specification, or on account of too extensive claims, is to be found in the original patent; the error arose otherwise than by inadvertence, accident, or mistake. The absence of all three of these mishaps from the history of the preparation of any original specification, may be proved by evidence which shows that the statements or claims alleged to have been omitted in one or another of these ways, were in fact omitted with deliberation or with care, or were omitted because they had to be, in order to secure the original patent,' or were disclaimed in order to secure an extension thereof. Evidence to show either of the last two of these circumstances, if it exists at all, may generally be found among the correspondence on file in the Patent Office, and may be introduced in the form of certified copies of the letters which contain it.*

§ 523. The sixteenth defence can be supported by the introduction of the original patent, if when it is compared with the reissue, the latter appears to claim something which the original did not, and appears to have been applied for a long time after the original was granted. How long this space of time must be in order to sustain this defence, depends largely upon the particular circumstances of particular cases. Different spaces of time which have been held to be sufficient for the purpose, are collated in the chapter on reissues,' and the burden is on the plaintiff to excuse delay for more than two years."

$524. The seventeenth defence always requires to be

' Revised Statutes, Section 4916. James 7. Campbell, 104 U. S. 356, 1881.

05 Leggett v. Avery, 101 U. S. 256, 1879.

4 Revised Statutes, Section 892.

5 Section 227 of this book.

6 Wollensak v. Reiher, 115 U. S. 101, 1884; Hoskin v. Fisher, 125 U. S. 222, 1887.

supported by the introduction of the original patent;' and generally requires expert testimony showing that the outward embodiment of something claimed in the reissue, is substantially different from anything described in the original patent and apparently intended to be claimed therein. The judge will not reject such expert testimony, unless the case is so clear that he would have decided the question on a demurrer, if it had been presented to him by that pleading.

§ 525. The eighteenth defence requires evidence that neither the inventor,' nor any executor or administrator of the inventor, made any proper application in writing for the extension of the patent. It will not be enough to produce a certified copy of an application filed out of due time, by the proper person, or one filed in due time, by an improper person; because the presumption is, that the Commissioner would not have granted the extension without a proper application therefor; and because the production of an improper application does not negative the existence of a proper one.

6

§ 526. The nineteenth defence would require to be supported by the introduction of an officially attested copy of the record of the court repealing the patent, or if that record is proved to have been destroyed by fire,' or rendered illegible by wear or time, and not restored by the court to which it pertains,' it may be proved by a witness who examined and copied it when it was still unharmed. But parol evidence will not be admitted of a record of which only a part is lost. The part which still exists, must be produced or proved by an officially attested copy.'

1 Seymour v. Osborne, 11 Wallace, 516, 1870.

2 Revised Statutes, Section 4924. 3 Wilson v. Rousseau, 4 Howard, 673, 1846.

4 Revised Statutes, Section 905. 5 United States v. Delespine's Heirs, 12 Peters, 654, 1838.

Little v. Downing, 37 New Hampshire, 355, 1858.

Revised Statutes, Sections 899 and 900.

8 1 Wharton on Evidence, 135. Nims v. Johnson, 7 California, 110, 1857.

§ 527. The twentieth defence calls for the introduction in evidence, of a properly certified copy of the foreign patent which is relied upon to curtail the term of the patent in suit; and if the parties offer no testimony to aid the court in determining whether the foreign patent, so proved, is for the same invention as the United States patent upon which the action is based, then the court will determine that point from an inspection of the two documents.' But if expert evidence on that subject is offered, it will doubtless be received.❜

$528. The twenty-first defence is supported by proof that the plaintiff has made or sold one or more specimens of the patented article without marking it "patented," together with the day and year whereon the patent was granted.' When such evidence is introduced, the burden is shifted to the plaintiff, to show that before suit was brought the defendant was duly notified that he was infringing the patent, and that he continued to infringe after such notice.*

$529. The twenty-second defence may sometimes be sustained by means of pointing out faults in the plaintiff's proof of title. Where that proof is apparently complete, it can be attacked only by the introduction of assignments or grants in writing, which intervene between some of the links of the plaintiff's chain of title in such a way as to destroy or impair its continuity. The numerous points of law relevant to title are explained in the eleventh chapter of this book. It is enough to say in this connection that no title will be recognized in a court of law, unless it is evidenced by instruments in writing, and that such instruments may probably be proved by duly certified copies of their record in the Patent Office."

§ 530. The twenty-third defence may be sustained by

1 De Florez v. Raynolds, 17 Blatch. 439, 1880.

Bischoff v. Wethered, 9 Wallace,

812, 1869.

Revised Statutes, Section 4900.

4 Goodyear v. Allyn, 6 Blatch. 36, 1868.

5 Revised Statutes, Section 4898. 6 Section 495 of this book.