or by the office must be paid in specie, treasury notes, national bank notes, certificates of deposit, or post-office money-orders. (Patent Office Rules, July, 1870.) 431. MONEY PAID BY MISTAKE.-Money paid by actual mistake will be refunded; but a mere change of purpose after the payment of money will not entitle a party to demand such return. (Patent Office Rules, July, 1870; Act of July 8, 1870, § 70.) 432. RevenUE STAMPS must be attached as follows: 1st. A stamp of the value of fifty cents is required upon each power of attorney authorizing an attorney or agent to transact business with this office relative to an application for a patent, reissue, or extension. 2d. No assignment directing a patent to issue to an assignee will be recognized by this office, nor will any assignment be recorded, unless stamps shall be affixed, of the value of five cents, for every sheet or piece of paper upon which the same shall be written. 3d. The person using or affixing the stamp must cancel the same by writing thereupon the initials of his name and the date. (Patent Office Rules, July, 1870.) 1. PATENT MAY ISSUE TO ASSIGNEES.-Patents may be granted and issued or reissued to the assignee of the inventor or discoverer, the assignment thereof being first entered of record in the Patent Office; but in such case the application for the patent shall be made and the specification sworn to by the inventor or discoverer; and also, if he be living, in case of an application for reissue. (Act of July 8, 1870, § 33.) 2. ASSIGNMENTS, GRANTS, AND CONVEYANCES.-Every patent, or any interest therein, shall be assignable in law by an instrument in writing; and the patentee, or his assigns or legal representatives, may, in like manner, grant and convey an exclusive right under his patent to 623 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. (Act of July 8, 1870, § 36.) (As to right of assignee in cases of reissue, vide supra, p. 556. In cases of extension, p. 603.) 3. INTERESTS WHICH MAY BE CONVEYED.-A patent may be assigned, either as to the whole interest or any undivided part thereof, by any instrument in writing. No particular form of words is necessary to constitute a valid assignment, nor need the instrument be sealed, witnessed, or acknowledged; and a patent will, upon request, issue directly to the assignee or assignees of the entire interest in any invention, or to the inventor and the assignee jointly, when an undivided part only of the entire interest has been conveyed. When the patent is to issue in the name of the assignee, the entire correspondence should be in his name. The patentee may grant and convey an exclusive right under his patent to the whole or any specified portion of the United States, by an instrument in writing; or he may convey separate rights under his patent to make or to use or to sell his invention, or he may convey territorial or shop rights, which are not exclusive. Such conveyances are mere licenses, and need not be recorded. (Patent Office Rules, July, 1870.) What if Congress provides for three kinds of assignments: first, as to the whole interest; second, as to an undivided part; and, third, an exclusive right in any district, (Blanchard v. Eldridge, 1 Wall., 330;) but the stat |