he invents, is not affected by the fact that he is at the time in the employ of another;' for persons employed, as much as employers, are entitled to their own independent inventions. The original title of a patentee to a patent issued to him, is presumed to continue till he is shown to have parted with it; and the grantee named in a reissue patent is presumed to be the lawful owner of that patent, until he is shown not to have owned the patent which he surrendered in order to obtain that reissue, or is shown to have parted with the title to the reissue after that date.*

5

§ 274. An assignment of a patent is an instrument in writing, which, in the eye of the law, purports to convey the entire title to that patent, or to convey an undivided share in that entire title, or at least the entire title, or an undivided share, in the invention covered by a particular claim." Such assignments usually purport to convey the entire right secured by the patent; and therefore they cover the exclusive right to make, to use, and to sell the patented invention throughout the United States. It has, however, been held that an assignment which purports on its face to convey the exclusive right to make and sell the invention covered by the patent, is a full assignment of that patent, because an expressed exclusive right to make and sell, carries with it an implied exclusive right to use, the subject-matter of the patent,' and the same result follows with still more force, from an assignment of the exclusive right to make, use and sell, and to vend to others to use and sell." Assignments of legal titles to patents must be in writing, because the statute provides no other method of effecting such an assignment;' and because since patent

1 Hapgood v. Hewitt, 119 U. S. 226. 1886; Whiting . Graves, 3 Bann. & Ard. 222, 1878; Hapgood v. Hewitt, 11 Fed. Rep. 422, 1882. Agawam Co. v. Jordan, 7 Wallace, 583, 1868.

1881.

Fischer v. Neil, 6 Fed. Rep. 89,

4 Washburn & Moen Mfg. Co. v. Haish, 4 Fed. Rep. 900, 1880.

5 Gayler v. Wilder, 10 Howard, 477, 1850; Potter v. Holland, 4 Blatch. 211, 1858.

6 Pope Mfg. Co. v. Mfg. Co. 34 Fed. Rep. 894. 1888.

Nellis v. Mfg. Co. 13 Fed. Rep. 451, 1882.

Pickhardt v. Packard, 22 Fed. Rep. 530. 1884.

Revised Statutes, Section 4898.

rights are creatures of statute and not of common law, the transfer of the legal title thereto cannot be regulated by the rules of the latter system.' It seems, however, that an equitable title may be created by parol,' and if such a title can be created by parol, it may, perhaps, by parity of reasoning, be transferred by the same method. But a recital in a writing, that a particular person is an owner with the subscriber of a patent granted to the latter, is not even an equitable assignment.'

Titles conveyed by assignments are usually unconditional; but they may also be held upon special tenures. One instance of such a tenure is presented where the assignment contains a condition that the assignee shall pay a specified royalty to the assignor during the life of the patent assigned. And other estates than a complete one may be created in patents by assignments. An estate for years, and an estate in remainder, are examples of these."

$275. The patent assigned ought to be described in the assignment by its number and date, and by the name of the patentee, and by the name of the invention which it purports to cover; but an assignment will be valid though it is lacking or erroneous in one or more of these particulars, if the description which it contains excludes doubt as to the patent intended to be conveyed. The designation of the assignee in an assignment is also sufficient where the person intended can be identified, even where evidence outside of the assignment is required for that purpose.' An assignment of an invention or patent for a machine, will not convey any patent for a process in the performance of which

'Gayler v. Wilder, 10 Howard, 498, 1850.

2 Whiting v. Graves, 3 Bann. & Ard. 225, 1878.

3 Kearney v. Railroad Co. 27 Fed. Rep. 701, 1886.

4 Littlefield v. Perry, 21 Wallace, 220, 1874.

5 Solomons v. United States, 21 Court of Claims, 481, 1886.

Case v. Morey, 1 New Hampshire, 349, 1818; Holden v. Curtis, 2 New Hampshire, 63, 1819; Harmon v. Bird, 22 Wendell (N.Y.), 113, 1839; Hill v. Thuermer, 13 Indiana, 351, 1859.

Fisk Clark & Flagg v. Hollander, MacArthur & Mackay, 360, 1883.

that machine finds its only utility.' An assignment by a natural person requires no other authentication than the assignor's signature; and where such an assignment is executed by an attorney in fact, it must be executed in the name of the assignor, and cannot lawfully be executed by the attorney in his own name. Assignments are sometimes acknowledged before magistrates; but if such an acknowledgment is of any value, it is so merely because it obviates the necessity of proving the signature of the assignor, and if it obviates that necessity, it does so by virtue of the law of the particular State in which it is acknowledged. An assignment by a corporation needs not to be authenticated by its corporate seal, but is properly executed, if executed in the name and by the authority of the corporation, and by a proper officer, who signs for the corporation, and signs as an officer thereof. An assignment to a corporation confers no title upon any stockholder therein; and an assignment to a corporation which is not organized till after the date of the assignment will, at least by way of estoppel, inure to its benefit when organized, and will be good as against the assignor."

A married woman, an infant, or a person under guardianship may be the assignee of an invention or of a patent. Such persons may also assign their inventions or patents by complying, not only with the United States law which requires assignments of patents to be in writing, but also with those laws of their particular States which govern analogous acts of such persons.'

$276. An assignment for which the consideration was never paid, and which was never acted upon by either of

the parties thereto, conveys no title to the assignee;' but no assignment which has been acted upon by the parties thereto can be revoked on the ground of a partial failure to pay the promised price."

$277. Rights of action for past infringements of a patent are not conveyed by any mere assignment of that patent;' but they may be conveyed by any assignment which purports to convey them, whether that document purports also to convey the patent,' or purports to convey the rights of action alone."

§ 278. The construction of assignments depends primarily upon the meaning of all the language in which they are composed, rather than upon that of any particular words they contain; and if that language is clear in the eye of the law, its effect cannot be varied by any parol evidence;' but if that language is ambiguous, it may be construed in the light of certain classes of parol proof. The parties will never be permitted to testify what they intended to signify by the language they used, because if they were, assignors might narrow, and assignees might widen, the scope of the rights conveyed, by simply making oath to alleged former states of their own minds. Perjury could seldom be detected in such a case; and such & rule would put property at the mercy of avarice. Nor is any evidence admissible which merely shows that one of the parties to an assignment made such declarations, or did such acts, in pursuance of that assignment, as indicate that he understood the document in a sense most favorable to himself. If such evidence were admissible, the honest mistake of an assignor, in con

'Railroad

Co. v. Trimble, 10 Wallace, 380, 1870.

2 Hartshorn v. Day, 19 Howard, 222, 1856; Mackaye v. Mallory, 12 Fed. Rep. 328, 1882.

3 Moore r. Marsh, 7 Wallace, 515, 1868; May v. County of Juneau, 30 Fed. Rep. 245, 1887; Koalatype Co. . Hoke, 30 Fed. Rep. 444, 1887; May . County of Saginaw, 32 Fed.

Rep. 629. 1888.

Hamilton v. Rollins, 3 Bann. & Ard. 160, 1877.

5 Hayward. Andrews, 12 Fed. Rep. 786, 1882.

6 Washburn v. Gould, 3 Story, 122, 1844.

1 Railroad Co. v. Trimble, 10 Wallace, 367, 1870.

struing his contract, would often deprive an assignee of rights which he had honestly bought; and the honest mistake of an assignee would often deprive an assignor of rights which he never had sold. But parol evidence is admissible to construe an ambiguous assignment, if that evidence shows the existence of such collateral documents, or surrounding circumstances, attending the execution of that assignment, as throw light upon the meaning of its words;' or shows that both parties to that assignment, practically construed it, after its execution, and in so doing construed it alike.' If ambiguities still remain in an assignment after all other recognized methods. of solving them have been employed, they are to be solved against the grantor, as he is supposed to have written the document, and therefore to be chargeable with the obscurity.'

§ 279. Reformation of an assignment may be had by means of a bill in equity filed for that purpose, if that assignment does not conform to the mutual intention of the parties to its execution; but neither party can secure such reformation on proof of what his intention was, unless he also proves that the intention of the other party was the same. But no reformation of an assignment can affect the right of any innocent purchaser, for a valuable consideration, who had no notice, at the time of his purchase, that the mutual intention of the parties was different from the assignment which passed between them." § 280. No extension of a patent is conveyed by an assignment of the first term thereof.

Read v. Bowman, 2 Wallace, 591, 1864; Phelps v. Classen, 1 Woolworth, 212, 1868; Wetherell v. Zinc Co. 6 Fisher, 50, 1872.

Toplif v. Toplif, 122 U. S. 131, 1886; Wilcoxen v. Bowles, 1 Louisiana An'l, 230, 1846; Parrott v. Wikoff, 1 Louisiana An'l, 232, 1846; Coleman v. Grubb, 23 Penn. St. 409, 1854.

3 Smith . Selden, 1 Blatch. 475,

Nor is any extension, which

1849; May v. Chaffee, 2 Dillon, 385, 1871; Falley v. Giles, 29 Indiana. 114, 1867.

Downton v. Allis, 9 Fed. Rep. 771, 1881.

5 Gibson v. Cook, 2 Blatch. 149, 1850; Woodworth v. Cook, 2 Blatch 151, 1850.

6 Wilson v. Rousseau, 4 Howard 646, 1846.