The owner of a patent, whether he be the original inventor and patentee, or an assignee, may himself assign and transfer his right, in whole or in part. (y) Conditions or limitations, which

(x) A mechanical equivalent has been defined as "such an equivalent as a mechanic of ordinary skill in the construction of similar machinery, and having the plaintiff's specification and machine before him, could substitute in the place of the mechanism described, without expensive experiments, and without the exercise of his inventive faculties." Hall, J., in Burden v. Corning, 2 Fish. 492, and in Johnson v. Root, 1 Fish. 163. Sprague, J., says: "The term 'equivalent' has two meanings, as used in this class of cases. The one relates to the results that are produced, and the other to the mechanism by which those results are produced. Two things may be equivalent, that is, the one equivalent to the other, as producing the same result, when they are not the same mechanical means. Mechanical equivalents are spoken of as different from equivalents that merely produce the same result A mechanical equivalent, I suppose, as generally understood, is where the one may be adopted instead of the other, by a person skilled in the art, from his knowledge of the art." In Foster v. Moore, 1 Curt 291, Curtis, J., says: "I do not think the doctrine respecting the use of mechanical equivalents is confined by the patent law to those elements which are strictly known as such in the science of mechanics. In the present advanced state of that science there are different well-known devices, any one of which may be adopted to effect a given result, according to the judgment of the constructor. And the mere substitution of one of these for another cannot be treated as an invention. It does not belong to the subject of invention, but of construction." See also Smith v. Downing, 1 Fish. 64; Cahoon v. Ring, 1 Clif. 692; Tatham v. Le Roy, 2 Blatchf. 486. As to the application of the doctrine of mechanical equivalents where the invention is only an improvement on a known machine, see McCor-mick v. Talcott, 20 How. 402; Singer v. Walmsley, 1 Fish. 558: Seymour v. Osborne, 11 Wall. 555. The same principle applies to the use of "chemical equivalents "in patents for a process or a composition of matter, but it is held that the substituted article must have been known as an equivalent for the other at the date of the original invention. Byam v. Farr,

1 Curt 263; Allen v. Hunter, 6 McLean, 803; Unwin v. Heath, 6 H. L. C. 505.

(xx) Aiken v. Manchester Print Works,

2 Clif. 435.

(y) Act 1870, § 86: "Every patent, or any interest therein, shall be assignable in law. by an instrument in writing

♦ 257 qq form a part of the contract of sale or transfer, are obligatory on both parties, and may be such as the parties agree upon. But questions have arisen as to the rights of a purchaser where they are not limited or restrained by specific agreement.

One of these is as to the right of the purchaser to profit qq by * the renewal or extension of the patent. The weight of authority leads to the conclusion, that he who holds the whole interest in the patent, by assignment, before the extension, will not hold it after the extension, unless something in the instrument of assignment, or in the special act granting the extension, gives to the purchaser this right. (z) and the patentee, or his assigns or legal representatives, may, in like manner, grant and convey an exclusive right under his patent to the whole or any specified part of the United States; and said assignment, grant, or conveyance, shall be void as against any subsequent purchaser or mortgagee for a valuable consideration without notice, unless it is recorded in the Patent-Office within three months from the date thereof. There are three classes of persons in whom the patentee can vest an interest of some kind in the patent. They are an assignee, a grantee of an exclusive sectional right, and a licensee. An assignee is one who has transferred to him in writing the whole interest of the original patent, or an undivided part of such whole interest in every portion of the United States. And no one, unless he has such interest transferred to him, is an assignee. A grantee is one who has transferred to him in writing the exclusive right under the patent, to make and use, and to grant to others to make and use, the thing patented, within and throughout some specified part or portion of the United States. Such right must be an exclusive sectional right, excluding the patentee therefrom. A licensee is one who has transferred to him in writing, or orally, a less or different interest than either the interest in the whole patent, or an undivided part of such whole interest, or an exclusive sectional interest." Per Ingersoll, J., in Potter v. Holland, 1 Fish. 333. So Brooks v. Byam, 2 Story, 525; Suydam v. Day, 2 Blatchf. 20; Blanchard v. Eldridge, 1 Wall. Jr. 839. An assignment may be made before the issuing of the patent. Gayler v. Wilder, 10 How. 493; Rathbone v. Orr, 6 McLean, 131; and may cover future improvements. Nesmith v. Calvert, 1 Wood. & M 41. The provision as to recording a transfer does not apply to a mere license. Brooks v. Byam, 2 Story, 542; Stevens v. Head, 9 Vt. 177. As to the rights of joint owners of a patent, it is settled that such joint owners are not ipso facto partners. Kinsman v. Parkhurst, 18 How. 289; affirming s. c. 1 Blatchf. 72. And it has been held that each has the right to make and use, and to license others to make and use, the thing patented, without accountability to the other. Cleem v. Brewer, 2 Curt. 234. And such appears to be the law at this day, notwithstanding the case of Ritts v. Hall, 3 Blatchf. 201, where it was held that one joint owner might sue another for infringement in respect of the former's undivided interest in the patent for the articles sold by the latter. See an able criticism of this case in Curtis on Patents, §189.

(z) The Act of 1836, § 18, re-enacted in Act of 1870, § 67, provides that "the benefit of the extension of a patent shall extend to the assignees and grantees of the right to use the thing patented to the extent of their interest therein." The constructions given to this clause have been very conflicting; and perhaps the true meaning cannot be deemed fully settled even now. In the Circuit Court it was held by Story, J., that this clause did not enlarge the rights of the grantee or assignee to use the thing patented, beyond the interest originally granted; that if that interest was by its nature, or by a just interpretation of the terms of the as signment, limited to the original term, the assignee could have no interest in the renewed term; but that if, by the original assignment or grant, any interest in the renewed term had been conveyed to the assignee or grantee, the statute carried into effect the intent of the parties, and turned the equitable right of the assignee to an interest in the renewed patent into a legal title. Wood worth v. Sherman, rr

Another question is, how far the exclusive right to use or sell to be used the article within a specified territory extends. On this point it is held, that an assignee holding may sell the articles within the territory, to persons who buy to sell it * abroad. Under this ruling, a limitation of the territory rr would seem to be of less effect than it was intended to have. If a man in a county in New York bought the right to make and sell a patented hay-cutter in that county, he could not himself sell them elsewhere. But he might establish his manufactory, and make them in any quantities, and sell them to any persons who bought to sell them again in any part of the country. It would, however, undoubtedly, be within the power of the parties to restrain or suppress this right as they chose, by specific agreements to that end. (a) l

If a note be given for a patent, proof that the patent was void or the invention wholly ineffectual is a good defence. But if it can be used and effectually applied to useful purposes, it is no

3 Story, 171, A similar view was expressed by McLean, J., in Brooks v. Bick-nell, 4 McLean, 66. But in Wilson v. Rousseau, 4 How. 682, a majority of the Supreme Court held that the benefits of the renewal were extended by this section to such assignees or grantees of the right to use the patented machine as were in the use thereof at the date of the renewal, and that such persons had the right to continue the use of such patented machine during the renewed term to the extent of their interest, whether one machine or more; but that the right thus conferred was only the right to use, not to make or sell, or license others to make or sell; and that such right was not exclusive, no matter bow broad or how exclusive the assignment had been under the original term. See also Bloomer v. McQuewan, 14 How. 650; Chaffee v. Boston Belting Co. 22 How. 217; Bloomer v. Millingen, 1 Wall. 340. In R. R. Co. v. Trimble, the assignment was, "for all alterations and improvements on the same from time to time." And it ran, "to the full end of the term for which letters-patent are or may be granted." Held, by the Supreme Court of the United States (Bradley, J., dissenting), that the legal title of a patent the patentee obtained for an improvement, which was extended, passed to the assignee, with the extension. In Wilson v. Rousseau, the patent in question was for a machine; but in Day v. Union Rubber Co. 3 Blatchf. 497, it was held, that the terms of this section permitted the assignee to continue the use of "the thing patented," whether the patent were for a machine alone, or for a process, or a machine to be used in such process, or for a process alone, and whether the identical machinery used by such assignee was in existence before the renewal of the patent or not. But see Wood v. Mich. South. R. R. 3 Fish. 464; Jenkins v. Nicholson Pavement Co. 1 Abb. U. S. 567; Chase v. Walker, 3 Fish. Pat. Cas. 120; Hodge v. Hudson River R. R. Co. 6 Blatchf. 85. That a general assignment of an interest in a patent gives the assignee no interest in the renewal beyond the right to use the thing patented, unless the terms of the assignment embrace the renewed patent, see Phelps v. Comstock, 4 McLean, 356; Gibson v. Cook, 2 Blatchf. 146; Clum v. Brewer, 2 Curt. 520. By § 63 of the Act of 1870, extensions are to be granted hereafter only on patents issued prior to March 2, 1861.

(a) See post, next section and cases there cited, especially in notes (d) and

(f).

1 Where the owner of a patent-right in a machine assigned it for a royalty on each machine sold by the assignee, the latter was held compelled to pay the royalty on all machines covered by the patent the use of which was allowed by him, though such machines were not sold by him. Rodgers v. Torrant, 43 Mich. 113.

•257 ss defence that the use is not profitable from the excessive consumption of power by the machine. (aa) l