either viva voce or by deposition, according to the practice of the court, on behalf of either or any of the parties to the said action or other proceeding: Provided, That nothing herein contained shall render any person who is charged with any offense in any criminal proceeding competent or compellable to give evidence for or against himself or herself, or shall render any person compellable to answer any question tending to criminate himself or herself, or shall in any criminal proceeding render any husband competent or compellable to give evidence for or against his wife, or any wife competent or compellable to give evidence for or against her husband, or in any proceeding instituted in consequence of adultery; nor shall any husband be compellable to disclose any communication made to him by his wife during the marriage, nor shall any wife be compellable to disclose any communication made to her by her husband during the marriage. Approved July 2, 1864." 355. COMPETENCY OF WITNESSES.-It was also formerly held that the testimony of a witness directly or indirectly interested was not admissible in an interference, (Marshall v. Mee, MS. Appeal Cases, D. C., 1853,) however small the amount of the interest might be, (Arnold v. Bishop, MS. Appeal Cases, D. C., 1841;) but by the act of July 2, 1864, the disabilities of such witnesses were removed, and they are now competent and compellable to testify. If no objection is made to the competency of a witness on his examination, and both parties examine him, it will be too late to take the objection afterward. (Allen v. Alter, MS. Appeal Cases, D. C., 1860.) In determining what credit is to be given to the testimony of witnesses, every circumstance affecting their veracity should be taken into calculation, (Evans v. Hettick, 3 Wash., 423,) and weight should be given to it in proportion to the competency of the witness to judge of the matter sworn to. (Allen v. Hunter, 6 McLean, 310.) The presumption of law is, that a witness on oath testifies honestly until the contrary is known. (New England Screw Company v. Sloan, MS. Appeal Cases, D. C., 1853.) The testimony of witnesses otherwise incompetent may be received and considered by the agreement of the parties. (Warner v. Goodyear, ib., 1846.) 356. EXPERTS.-To determine the question of the mechanical difference of machines, the law permits the opinions of men called experts to be given in evidence, and when such men are qualified, and free from bias, their testimony is entitled to great respect. (Morris v. Barret, 1 Fish., 461.) The patent act contemplates two classes of persons as peculiarly appropriate witnesses in patent cases, namely: 1st, practical mechanics, to determine the sufficiency of the specification as to the mode of constructing, compounding, or using the patent; 2d, scientific and theoretic mechanics, to determine whether the patented thing is substantially new in its structure and mode of operation, or a mere change of equivalents; and the second class is by far the higher and more important of the two. (Allen v. Blunt, 3 Story, 742.) The opinions of professional men are evidence only as to matters which relate to their profession, (Brooks v. Bicknell, 3 McLean, 447;) thus, in medical science a phy sician is an expert; in navigation, a sailor. (Page v. Ferry, 1 Fish., 298.) The statute defines the character of an expert as one "skilled in the art or science" to which his opinion appertains, (ib.;) and one not so skilled is not a fit person to testify as to whether a specification contains a sufficient description. (Poppenhausen v. New York G. P. C. Company, 4 Blatchf.; Allen v. Hunter, 6 McLean, 307.) The testimony of experts is useful to show the operation of devices; but when experts undertake to tell what a patent is for, they assume the duty of the court; and when they undertake to say what is or is not a violation of the patent, they not only assume the duty of the court, but the jury. (Waterbury Brass Company v. New York and Brooklyn Brass Company, 3 Fish., 43.) Experts may be examined to explain the meaning of terms of art on the principle, Cuique in sua arte credendum, (Corning v. Burden, 15 How., 270; Winans v. New York and Erie Railroad Company, 21 How., 100,) or as to whether a patent is void for uncertainty, (Washburn v. Gould, 3 Story, 138,) or to explain the difference between an original and reissued patent, (Philadelphia and Trenton Railroad v. Stimson, 14 Pet., 462,) or as to the identity of different mechanical structures, (Parker v. Stiles, 5 McLean, 64,) or the state of the art at any given time, (Winans v. New York and Erie Railroad, 21 How., 100,) or to explain machines, models, and drawings exhibited, (ib.;) but their opinion cannot be dignified with the mantle of authority, even on questions of science. (French v. Rogers, 1 Fish., 133.) SEC. XXI. Reissues. 357. Résumé of the law. 360. Application made by inventor 361. Concurrence of parties. 365. Defects cured by reissue. 367. Use under defective patent. SEC. 370. Through fault of applicant. 374. Specification and claim subject 375. Surrender does not take effect until reissue is granted. 376. Rights conferred by reissue. 377. Petition for reissue by inventor. 378. Petition for reissue by assignee. 379. Oath by applicant for reissue by inventor. 380. Oath by applicant for reissue by assignee. 357. RÉSUMÉ OF THE LAW CONCERNING REISSUES.-Before the British act of 5 and 6 Wm. IV. c. 83, 1835, the consequence of a defect in the specification, in England, was an absolute loss of the privilege of the patent right. By the first section of that act the patentee or his assignee "may, with the leave of the attorney or solicitor general, enter a disclaimer of any part of either the title of the invention or of the specification, stating the reason for such disclaimer, or may, with such leave, enter a memorandum of any alteration in the said title or specification, not being such disclaimer, or such alteration as shall extend the exclusive right granted by the patent;" and such disclaimer or memorandum is thereafter to be considered a part of the title or specification. In the early American cases, after the act of 1793, it appears to have been supposed that the law had by that act been varied from the English; so that the patent right was forfeited and lost only in case of the defects specified in the sixth section being designed and fraudulent. It is provided by that section that, in a case for an infringement, the defendant may give in evidence, in his defense, "that the specification does not contain the whole truth relative to his discovery, or that it contains more than is necessary to produce the described effect, which concealment or addition shall fully appear to have been made for the purpose of deceiving the public." Mr. Justice Story, in giving an opinion in the circuit court, in 1813, on an examination of this section, remarked: "We think that the manifest intention of the legislature was not to allow any defect or concealment in a specification to avoid the patent, unless it arose from an intention to deceive the public." (Whittemore v. Cutter, 1 Gall., 429.) In the same year, Mr. Justice Washington, instructing the jury in the circuit court of the United States for Pennsylvania, said on the subject of concealment, "the matters not disclosed must appear to have been concealed for the purpose of deceiving the public, in order to invalidate the patent." (Park v. Little, 3 Wash., 196.) In 1817, again, these judges appear still to have entertained the same opinion. (Lowell v. Lewis, 1 Mass., 182; Gray v. James, 1 Pet. C. C., 401.) But it was, at the same time, remarked by Mr. Justice Story, that the doctrine was liable to grave objections on the score of expediency. (Whittemore v. Cutter, 1 Gall., 429.) And it was subsequently abandoned, and the English doctrine adopted, that a defect in the specification, from want of com |