donment of the invention by the inventor, and his dedication of it to the public, and it is not incumbent on the plaintiff to prove, in the first instance, that he has not abandoned or so dedicated his invention, unless he incurs that burthen by incidentally proving such delay, or other circumstances, as require explanation in order to rebut the inference of such an abandonment and dedication.

Under the act of congress of 1836, the citizenship of the patentee is material only in relation to the amount of the fee he is liable to pay; and as the payment of the fee is a matter which the court does not take into consideration, this being subject to the superintendence of the executive officer who issues the patent, it seems to follow that no evidence of citizenship need be given by the plaintiff.

16

The fact of the grant and its extent are proved by the production of the patent. It was contended in one case that where the invention is described in the affidavit of the patentee, he will be limited to the invention so described, however extensive may be his specification; but this point was not decided by Mr. Justice Washington, before whom the case was pending, who only decided that the affidavit might be resorted to for an explanation of the ambiguity in the

16 Whittemore v. Cutter, 1 Gall. R. 429.

patent, and this met the object of the defendant." But the position assumed by the defendant in that case, seems not be tenable, for though ambiguities in the patent, of some descriptions, at least, may be cleared up by evidence aliunde, this is quite a different thing from holding that the obvious construction and meaning of the instrument may be controlled by such evidence.

The specification will, generally, also show prima facie, whether it is sufficient or defective.

The utility, as distinguished from the frivolity or perniciousness, and legality of the invention, will also, generally, appear from the specification.

18

The invention must be proved to have been reduced to practice; and the plaintiff must show that it effects what the specification professes. In a case that occurred in the English court of Common Pleas in 1834, this is confounded with the utility of the invention. It was the case of a patent for a machine for spreading calicoes to be dried, and taking them up when dried. It was proved by the plaintiff that it would spread and take up calicoes, excepting those stiffened with clay for deceptive purposes. The jury found that it was "not useful in some cases for taking up goods;" meaning, as it seems, that it would not

17 Rattibone v. Derringer, 4 Wash. C. C. R. 215.

18

Supra. ch. vii. s. 8; see also Evans v. Eaton, 1 Pet, C. C. R. 341.

take them up. Tindal J. Tindal J. "We think we are not warranted in drawing so strict a conclusion from this finding of the jury, as to hold that they have intended to negative, or that they have hereby negatived, that the machine was useful in the generality of cases which occur for that purpose. If the jury think it useful in general, because some cases occur in which it does not answer, we think it would be much too strong a conclusion to hold the patent void."19

Finally, to make out his case, the plaintiff must prove an infringement, in respect to which, the presumptions are in favor of the defendant. What is an infringement has been already considered.20

A patent right cannot be infringed until after the grant of the patent; it is, therefore, necessary to prove acts of infringement done subsequently to its date.21

It must be proved that the defendant has made, used or sold the same machine, or other subject for which the plaintiff has a patent. It is not enough that he has sold one that merely resembles it. The law does not require proof that it is precisely the same in form and proportions; it is sufficient if the distinguishing characteristics are the same.22 "Machines are the same," says Mr. Justice Washington,

19 Howorth v. Hardcastle, 1 Bing. N. R. 182.

20 Supra. c. xvii.

21 Dixon v. Moyer, 4 Wash. C. C. R. 68; S. C. Coxe's Dig. 583. 22 Dixon v. Moyer, 4 Wash. C. C. R. 68; S. C. Coxe's Dig. 532.

"if they operate in the same manner, and produce the same results, upon the same principles."2

It is upon this question of identity that patent cases very often turn. But as to the results, the most perfect similarity of products is not alone sufficient to establish the identity, since precisely similar products may be made by different machines and different processes. But where the products were precisely similar, Lord Tenterden ruled that this circumstance, taken together with acts of the defendant, may be ground to presume that the machines are the same, as where the defendant refused to permit his manufactory to be inspected.24 In an action for an infringement of a patent for making ropes, in which it was proved that those of the defendant precisely resembled those made by the plaintiff's method, and that the defendant had refused to permit his manufactory to be examined for the purpose of furnishing evidence in the case, Lord Ellenborough remarked to the jury, "when one sees the rope of the defendant agree, in all its qualities, with a rope actually made upon the plaintiff's plan, it is prima facie evidence, till the contrary is shewn, that it was made upon his method."25

On this question the machines themselves, or re

23

Gray and Osgood v. James, 1 Pet. C. C. R. 394.

24 Hall v. Gervas and Boot, Gods. sup. 67.

25 Huddart v. Grimshaw, Dav. Pat. Cas. 288.

duced models of them, are most frequently produced in court, so that the jury may themselves determine by inspection, whether they are the same, or different. In England the practice has been, in some cases, first to apply to a court of equity to appoint persons to inspect the manufactories, in order to prove the identity of the machines or processes.2 The Circuit Court of the United States is presumed to have authority under the general equity powers given by the act of 1836, to appoint commissioners for the inspection of manufactories in a patent cause, on the application of a party for that purpose, where it should be made to appear that a comparison of the manufactures could not be satisfactorily made by models or samples, or other testimony. No instance has, however, been reported of the appointment of persons for this purpose, by our courts.

It is a frequent practice to call in witnesses skilled in the art or manufacture to which the invention relates, to testify as to the identity or diversity of the machines or methods in question. On this practice Mr. Justice Story remarks: "As to the opinion of skilful witnesses, whether the principles of two machines are the same, no person doubts that it is competent evidence to be introduced into a patent cause. But although the testimony of witnesses be admis

26 Bovil v. Moore, Dav. Pat. Cas. 361, 182.