sible to prove the identity or diversity of machines in principle, yet after all it is but matter of opinion, and its weight must be judged of by all the other circumstances of the case. It is infinitely more satisfactory to ascertain, if we can, the precise differences and agreements; and, when these can be subjected to the eyes, they almost supersede all the evidence of mere opinion. In all my experience, I can scarcely recollect a single instance, in which the general question, whether the principles of two machines were the same, or different, has not produced from different witnesses, equally credible and equally intelligent, opposite answers. This would result only from the different meanings attached to the word, and from confounding its various senses. And this has been completely shown, when the same witnesses came to explain the precise agreements and differences, in which they have almost uniformly agreed. The case now before the court is a perfect proof in point. The witnesses differed as to the identity or diversity of the principles of the machines, but they all agreed in what were the precise differences and agreements in fact. There seemed, then, nothing left for the jury to decide, but whether these differences were substantial or formal; if substantial, then the machines were not alike; if formal only, then they were alike. And the question, whether the principles were the same in both machines, was, in reality, when all the facts were given, rather a matter of law, than of the opinion of mechanics; at least matter of law was necessarily mixed up with it, which mechanics could not be presumed to be acquainted with."27 So Mr. Justice Washington remarks, that the opinions of such witnesses, in relation to the materiality of apparent differences, are always entitled to great respect, but that, after all, "the jury must judge for themselves, as well upon the information given, as upon their own view, where the articles, or models of them, are brought into court."'28 Sec. II.-ON THE PART OF THE DEFENDANT. The defendant, in action for an infringement, must, under the general issue, if the plaintiff has made out a prima facie case, show, either that the plaintiff is not entitled to an exclusive privilege claimed, or that he has not violated it. The essential requisites to the validity of the patent, have already been stated in the preceding chapters, and it is unnecessary to enumerate them here. If the defendant can render the plaintiff's title defective in any of these, the action for an infringement must fail; for there can be no violation of a privilege which is shown not to exist. 27 Barrett v. Hall, 1 Mason, 470, 471. On the subject of the novelty of the invention, if this is contested, the evidence must come mostly from the defendant, since that introduced by the plaintiff is necessarily of a negative character; and Sir Vicary Gibbs, C. J. says "fifty witnesses, testifying that they never saw the invention before, would be of no avail, if one were called who had seen it. and practised it.""29 This rule of evidence has, it seems, been subject to abuse in England by means of perjury. In the course of the examination, before the committee of the House of Commons, in 1829,0 on the subject of patents, Mr. Benjamin Rotch makes a very striking statement as to the subornation of witnesses in trials of patent causes in England. He is objecting to the rule of law whereby a patent is held to be void if the alleged invention, or any part of it, had ever been known or practised at any former period, though dropped from use and not publicly known at the time of the new invention. He says he found, from experience, that the result of this rule is, that "if a clothier in the west of England has a patent, one single man is called from the north of England, who comes down into court, and having read the man's specification, stands up like a parrot, and will 29 Manton v. Manton, Dav. Pat. Cas. 250. 30 P. 114. I be found to swear, fourteen or twenty years ago, did so and so, and so and so, exactly verbatim, repeating the specification; the patent is upset ; nobody can provide against such evidence as that: and I do not hesitate to say there is more perjury in that one particular than could be believed by a committee who have not experienced what we have. It is always the interest of the whole trade against the patentee combined; they combine their money in the first place, and then fight away and procure witnesses at any rate." Mr. John Farey, in his affidavit, reported by the same committee," states that Durivel's patent, though his invention was a good one, was defeated by the testimony of one witness. Mr. Justice Johnson was of opinion that such testimony may be rebutted by circumstantial evidence. In a case for an infringement of Whitney's patent for his cotton-gin, to prove that it was known before the invention by the patentee, two witnesses were produced, one of whom testified that he had seen a similar machine in England, seventeen years before, called a "teazor or devil;" the other testified that he had seen a similar machine in Ireland. Upon this point Mr. Justice Johnson remarked: "There are circumstances within the knowledge of all mankind, which prove the originality of this invention 31 P. 211. more satisfactorily to the mind, than the direct testimony of a host of witnesses. The cotton plant furnished clothing to mankind before the age of Herodotus. The green seed is a species much more productive than the black, and by nature adapted to a much greater variety of climate; but by reason of the strong adherence of the fibre to the seed, without the aid of some more powerful machine for separating it, than any formerly known among us, the cultivation of it could never have been made an object. The machine, of which Mr. Whitney claims the invention, so facilitates the preparation of this species for use, that the cultivation of it has suddenly become an object of infinitely greater importance than that of the other species ever can be. Is it then to be imagined that, if this machine had been before discovered, the use of it would ever have been lost, or could have been confined to any tract of country left unexplored by commercial enterprise?"'"2 The provision in the act of Parliament, 5 and 6 W. 4, c. 83, s. 5, that in an action for an infringement, the defendant shall give notice of the objections to the patent which he intends to rely on at the trial, was intended probably to remedy such abuses. But the provision of the act of Congress of 1836, s. 15, is more effectual to prevent any such abuse, namely, 32 Whitney v. Fort, 1807; Fessenden on Patents, Ed. 1822, p. 134. |