witnesses who knew of his production of the art or article in a form available for immediate practical use. His diligence in perfecting the invention may be proved by any evidence establishing his perseverance in the effort to render it available as far as his health, his means, and his command of his own time and energies reasonably permitted. The plaintiff, in rebutter, may show that the date of the inventive act performed by his inventor preceded that of his patent or his application, and was in fact earlier than its performance by his rival, offering for this purpose the same class of evidence by which the date of his rival's inventive act might have been established. Or failing in this he may attack the diligence of his rival by testimony proving that his opportunities for perfecting the invention were unreasonably neglected, and that his rights as first conceiver were thereby forfeited in favor of the prompt reducer to whom the patent has been issued. Where this question of priority of invention has already been decided in an interference proceeding, the record of that judgment is admissible in favor of the then successful party, and though not conclusive on the jury is entitled to grave consideration. But the defendant must establish his position be

That actual use proves reduction to practice, see Coffin v. Ogden (1869), 3 Fisher, 640; 7 Blatch. 61.

6 For rules concerning diligence in reduction, see §§ 383-387, and notes,

ante.

That if the patentee temporarily abandoned his efforts and then resumed them after another inventor had applied for a patent, he cannot show that he invented before the date of his resumption, see Johnson v. Root (1862), 2 Fisher, 291; 2 Clifford, 108.

That where the later inventor first reduced to practice and applied for and obtained a patent, and the earlier inventor applied for a patent before he had reduced to practice, and was not diligent, the later inventor does not infringe the earlier inventor's patent, see Electric R. R. Signal Co. v. Hall R. R. Signal Co. (1881), 6 Fed. Rep. 603.

VOL. III.-17

7 That when the defendant proves that he invented the device before the plaintiff filed his application, the burden is on the plaintiff to show that he invented before the defendant did, see Thayer v. Hart (1884), 20 Fed. Rep. 693; 28 O. G. 542; 22 Blatch. 229.

That a foreign inventor cannot carry the date of his invention back by showing acts done in a foreign country, see Boulton v. Illingworth (1888), 43 O. G. 508.

That the fact that an alleged prior inventor, though patenting other kin dred inventions, did not patent this one is competent evidence against his invention of it, see Frink v. Petry (1874), 11 Blatch. 422; 1 Bann. & A. 1; 5 O. G. 201.

8 That a patent is increased in weight as prima facie evidence of priority by the success of the patentee in interference § 1024

yond reasonable doubt; otherwise the presumption arising in favor of the patentee from his own oath as to priority, confirmed by the issue of the patent, will prevail. The question involved in this defence sometimes presents itself in a modified form, as where the plaintiff's inventor was the first conceiver of the invention but is alleged by the defendant to have forfeited his right to a patent in favor of a later inventor, by his unreasonable delay in its reduction. The attitude of the parties toward certain of the issues raised by this defence are thus reversed, the defendant now attacking and the plaintiff supporting the diligence of the first conceiver; but the evidence applicable to these issues remains the same, and the burden of proof still rests on the defendant to overcome the presumptions created by the plaintiff's patent. This burden is not removed by the fact that the defendant has himself received a subsequent patent for the same invention.10

proceedings, see Ayling v. Hull (1865), mew v. Sawyer (1859), 1 Fisher, 516; 2 Clifford, 494. 4 Blatch. 347.

That the burden of proof as to priority rests on him to whom the decision of the Patent Office on an interference is adverse, see Wire Book Sewing Mach. Co. v. Stevenson (1882), 11 Fed. Rep. 155.

That the decisions of the Commissioner as to priority are not conclusive, though entitled to very great weight, see Gloucester Isinglass & Glue Co. v. Brooks (1884), 19 Fed. Rep. 426.

That the defendant's evidence of prior invention must remove all reasonable doubt, see Donoughe v. Hubbard (1886), 27 Fed. Rep. 742; 35 O. G. 1561; Worswick Mfg. Co. v. City of Buffalo (1884), 20 Fed. Rep. 126; 22 Blatch. 157; 27 O. G. 1239; Gottfried v. Phillip Best Brewing Co. (1879), 17 O. G. 675; 5 Bann. & A. 4.

That the presumption that the patentee is the first inventor arises from his oath, and remains till the contrary is proved, see Elizabeth v. Pavement Co. (1877), 97 U. S. 126; Union Sugar Refinery v. Matthiesson (1865), 2 Fisher, 600; 3 Clifford, 639; Bartholo

10 That the introduction of the defendant's subsequent patent does not change the burden of proof as to priority of invention, see Goodyear Dental Vulcanite Co. v. Gardner (1870), 4 Fisher, 224; 3 Clifford, 408.

That when the plaintiff first applied for a patent and the defendant obtained his by disclaiming the plaintiff's invention, but after the plaintiff's patent was granted re-issued his to cover the matter before disclaimed, the burden of proof is on him to show that his inventive act was the earliest, see Smith v. Allen (1865), 2 Fisher, 572.

That the testimony of a defendant that he was the first inventor of the article is overcome by proof that after the date of his alleged invention he applied for a patent relating to the same subject but based on an essentially different principle, see Lamson Cash Railway Co. v. Osgood Cash Car Co. (1886), 29 Fed. Rep. 210; 38 O. G. 1490.

That inferences drawn by the court

§ 1025. Evidence under the Fourth Defence: the Alleged Inven

tion not within the Protected Classes.

The fourth defence raises the question whether the patented invention is embraced within either of those six classes of inventions which are made patentable by the Acts of Congress. Though this is a question for the jury, the court may take judicial notice that the invention is not among those thus protected, when that fact is evident from the patent, and may then, without testimony, direct a verdict on this issue for the defendant.1 The plaintiff's patent furnishes prima facie evidence that the invention described and claimed therein is patentable. The defendant may contradict this evidence by expert and other testimony that the alleged invention does not possess the essential characteristics either of an art, a machine, a manufacture, a composition of matter, a design, or an improvement. If the alleged invention purports to be a combination, he may prove by similar evidence that its elements do not co-operate for the production of a unitary result, and that it is, therefore, a simple aggregation. In his rebutter, the plaintiff offers evidence of the same nature to

from the conduct of a party may outweigh the direct testimony of any number of witnesses, see the Telephone Cases (1888), 126 U. S. 1 ; 43 O. G. 377.

That the fact that one who now claims to have been the first inventor made no protest against the use of the invention or against the claims of another to be its inventor, but patented an improvement on it without attempting to cover the original, is strong proof against his present claims, see Hutchinson v. Everett (1885), 35 O. G. 1110; 26 Fed. Rep. 531.

Upon the subject of priority as between rival inventors, see §§ 370-391, 961, and notes, ante.

§ 1025. That the court may order a verdict for the defendant if it is apparent on the face of the patent that the invention is not within the protected classes, see Blessing v. Copper Works (1888), 34 Fed. Rep. 753; West

v. Rae (1887), 33 Fed. Rep. 45; Slawson v. Grand St., Prospect Park, & Flatbush R. R. Co. (1882), 107 U. S. 649; 24 O. G. 99; Everett v. Thatcher (1878), 16 O. G. 1046; 2 Flippin, 234; 3 Bann. & A. 435. These were cases in equity, but the same principles there applied would compel the court to protect the defendant against an adverse verdict at law. See also § 962, and notes, ante.

2 That the patent is prima facie evidence of the patentability of the invention, see Fraim v. Keen (1885), 25 Fed. Rep. 820; 34 O. G. 1048; Strobridge v. Lindsay (1880), 18 O. G. 62; 2 Fed. Rep. 692; 5 Bann. & A. 411.

That the presumption of patentability arising from the patent is not repelled when the device, though needed, is not shown to have been in use before, see Patterson v. Duff (1884), 20 Fed. Rep. 641.

controvert these positions of the defendant. The effect of such evidence, on either side, must be confined to the conformity of the invention claimed in the patent with the legal definition of these patentable classes of inventions. What the necessary attributes of the patented invention are is settled by the court through its construction of the patent, and cannot be affected by extraneous evidence. What the essential characteristics of each of the six classes of patentable inventions are is matter of determinate law, and equally beyond the sphere of testimony. Evidence is admissible to show that the attributes of the invention, as ascertained by the court, correspond with the essentials of a patentable art or article as defined by the law; but this evidence must consist almost entirely of the opinions of persons skilled in the detection of resemblances and differences, rather than of observers and narrators of specific facts. In many cases, indeed, the field of evidence is so narrow that the whole question must be practically treated as a question of law, the jury being required to follow the instruction of the court in reference to its decision.

§ 1026. Evidence under the Fifth Defence: Novelty of the

Patented Invention: Prior Use.

The fifth defence raises an issue as to the legal novelty of the patented invention. This issue embraces three questions: (1) Whether the invention had been used in such a manner in this country as to render it accessible to the public at the date of its alleged invention by the patentee or his assignor; (2) Whether it had been patented anteriorly to that date; (3) Whether it had been described in any printed publication which, before that date, had been placed within reach of the public. An affirmative answer to either of these three questions is equivalent to a denial of the legal novelty of the pat

3 That the patented invention is what the court construes the patent to cover and cannot be varied by other evidence, see §§ 731, 1019, and notes, ante.

4 For the essential attributes of each

class of inventions, see §§ 159–220, and notes, ante.

For the characteristics of a patentable combination, see §§ 153-156, and notes, ante.

ented invention, and, therefore, of the validity of the patent in which it is described and claimed.1 The patent answers all these questions in the negative, and thus throws upon the defendant the burden of proving the affirmative, in reference to at least one of them, beyond a reasonable doubt in order to maintain this defence.2 The question of prior use is