phrases.' The judges are not however obliged to blindly follow such testimony. They may disregard it, if it appears to them to be unreasonable.' While the testimony of experts, relevant to the meaning of particular words or phrases in letters patent, is to this extent admissible; such testimony is wholly inadmissible relevant to the construction of the letters patent as a whole.'

§ 190. In the absence of contrary evidence, the invention covered by a particular letters patent, is presumed to be identical with that covered by the application on which those letters patent were granted.*

$191. All persons are bound to take notice of the contents. of all letters patent of the United States, because those letters patent are matters of public record."

§ 192. THE statutory provisions relevant to disclaimers originated in 1837, and have never been substantially changed. Sections 7 and 9 of the Patent Act of that year,' embodied those provisions; and those sections continued in force till July 8, 1870, when they were substantially reenacted as Sections 54 and 60 of the Consolidated Patent Act of that date.' In 1874, the latter sections were, in their turn, re-enacted, without any material change, as Sections 4917 and 4922 of the Revised Statutes. It would have been better statute writing, if those two sections had always been blended together into one clear and comprehensive paragraph. Referring to the same subject, and standing, as they always have, in the same statute, they must undoubt

15 Statutes at Large, Ch. 45, Sections 7 and 9, p. 193.

216 Statutes at Large, Ch. 230,

Sections 54 and 60, p. 206; Taylor v. Archer, 8 Blatch. 318, 1871.

edly be construed together;' and the law they embody must be set forth, by extracting from both sections, all the material meaning of both, and by incorporating that meaning, together with the case law of the subject, into one systematic explanation. Let that therefore be the present attempt.

§ 193. Whenever, through inadvertence, accident, or mistake, and without any fraudulent or deceptive intention, a patentee has, in his specification, claimed materially more than that of which he was the first inventor, his patent shall be valid for whatever is justly his own; and every such patentee, his executors, administrators, or assigns, whether of the whole or any sectional interest in the patent, may maintain a suit at law or in equity, for the infringement of such part, if it is a material and substantial part of the thing patented, and is definitely distinguishable from the parts claimed without right. But in every such case, in which a judgment or decree shall be rendered for the plaintiff, no costs shall be recovered, unless the proper disclaimer was entered in the Patent Office, before the commencement of the suit. But no patentee shall be entitled to maintain any such suit, if he has unreasonably neglected or delayed to enter a disclaimer. And any such patentee, his heirs or assigns, whether of the whole or of any sectional interest therein, may, on payment of the fee required by law, make disclaimer of such parts of the subject-matter of the patent, as he shall not choose to longer claim, stating therein the extent of his interest in such patent. Such disclaimer shall be in writing, attested by one or more witnesses, and recorded in the Patent Office, and shall thereafter be considered a part of the original specification, to the extent of the interest possessed by the claimant and by those claiming under him after the record thereof. But no such disclaimer shall affect any action pending at the time of its being filed, except so far as may

1 Hailes v. Stove Co. 123 U. S. 588, 1887.

relate to the question of unreasonable neglect or delay in filing it.'

§ 194. The primary fact which brings the law stated in the last section into play, is the claiming by a patentee of materially more in his patent than he was entitled to claim." Such errors may spring from inadvertence. That is to say, they may spring from failure, on the part of the writer of the claims, to exercise proper care in penning them. So also, they may arise from accident: from chances against which even diligent care cannot always guard. But mistake is the most common source of such errors; and such errors may arise from mistake of fact or from mistake of law.

§ 195. Mistakes of fact, relevant to how much of a described process, machine, or manufacture was first invented by its patentee, frequently follow from lack of full information touching what was previously invented by others in the same department of the useful arts. Litigation may alone disclose the fact that the patentee's claims are too numerous or too broad to be consistent with novelty. Whenever this occurs, it is clear that the patentee ought no longer to appear to hold an exclusive right to anything which he was not the first to invent. To this end, the statute provides that he must disclaim that part, within a reasonable time, or, in default thereof, must suffer the statutory consequences. On the other hand it is equally clear, that if the patentee is willing to eliminate from his claims, everything which later information shows had been invented before him, he ought to be allowed to retain his exclusive right to the residue. To this end, the statute provides, that if within a reasonable time, he disclaims what was another's, he shall be enabled to enforce his patent as far as it covers what was his own invention. But a disclaimer cannot confine a claim to ground which does not appear in the patent to constitute an invention; even where that ground is narrower than that which was originally claimed in the patent.

1 Revised Statutes, Sections 4917 and 4922 blended together.

Hailes v. Stove Co. 123 U. S. 588, 1887.

§ 196. A mistake of law, which consists in claiming something not patentable, may also be remedied by disclaimer.' The law which requires and permits a patentee to disclaim, is not penal but remedial. It is intended for the protection. of the patentee, as well as for the protection of the public. The evil to be remedied is the same, where a patentee has claimed more than he ought, whether that result sprang from the fact that another invented it before him, or sprang from the fact that what he produced was not an invention at all. For this reason, the Supreme Court held that the eighth claim of Morse might be disclaimed, after having been held void for want of patentability, with the same effect as though it had been held void for want of novelty. The same reason would also permit a patentee to disclaim any claim which is void for want of invention. Indeed the statute expressly applies to such a case, for no man can be the first inventor of anything which is not an invention. He may be its first discoverer, if it is a law of nature, or its first constructor, if it is a product of mere mechanical skill, but its first inventor he cannot be.

$197. There appears to be no warrant in the statute, for disclaiming any claim which is void for want of utility, and for no other cause. An inventor of a new thing may generally ascertain its character in point of utility before applying for a patent. If he can do so, he ought to do so, and thus shield the public from the waste of time involved in examining and judging useless contrivances. Where a

patent has but one claim, and where the matter covered by that claim is useless, no disclaimer could make that patent valid. Where a part only of the claims of a patent are void for want of utility, and for no other cause, the void claims are not injurious to the valid ones, and therefore no disclaimer is needed in any such case. Where a claim purports to cover a thing constructed in either of several ways, and where that thing is useless if constructed in one of those ways, and useful if constructed in another, the claim

1 O'Reilly v. Morse, 15 Howard, 120, 1853.