that the defendant was not entitled to set up such a defence, the contract having been executed, and no fraud being alleged. But one of the judges thought that if the defendant had given notice that he disputed the validity of the patent, and would in future use the invention in his own right, such notice would change the position of the parties; for after it, the patentee might sue the defendant for an infringement of his patent for any subsequent user; and, perhaps, in an action on the agreement for the price of such subsequent user, the invalidity of the patent might be a defence.

It is prudent to insert a clause giving the patentee power to render the licence void, in case of non-payment of royalties or other sums reserved, or on nonperformance of any of the covenants. Power is sometimes reserved to place the royalties in the hands of a stakeholder during litigation affecting the patent.

It seems that a licence is not assignable to a third person in the absence of an express or implied power to assign, such as where the licence is granted to the licensee, his executors, administrators, or assigns.

In the case of an exclusive licence, it is desirable that the licensee should covenant to pay a certain minimum sum at stated periods in the shape of royalty; and it is the usual practice to insert covenants on the part of the patentee to proceed against persons infringing the patent (see Henderson v. Mostyn, L. R. 3 C. P. 202), or to permit the licensee to proceed in the patentee's name. In the absence of such a stipulation, the licensee would be without any remedy at law for an infringement. The Court will, however, grant an injunction at the suit of exclusive licensees (Renard v. Levinstein, H. & M. 628).

It has been decided that money paid in consideration of a licence cannot be recovered by action when

the patent turns out to be void (Taylor v. Hare, 1 Bos. and Pul. N. R. 260); except where fraud is proved (Lovell v. Hicks, 2 Y. and C. 472). To meet this case, it will be prudent to have a covenant in the licence, under which the parties may re-adjust their accounts in the event of the patent proving void or voidable.

When a patent is granted to two or more persons, each may use the invention without being liable to account to the other (Mathers v. Green, 1 Law Rep. Ch. Ap. 29, before Lord Cranworth, C.). See, however, the earlier case of Hancock v. Bewley (Johns. 601), as to the rights of parties where letters patent are vested in trustees for two or more persons as tenants in common.

The assignee of part of a patent separate from other parts may bring his action for an infringement of such part without joining as plaintiffs those persons who have distinct interests in the other parts, but have no interest in the damages sought to be recovered (Dunnicliff v. Mallet, 7 C. B. N. s. 209). This decision was mentioned with approval by the Court when delivering judgment in the case of Walton v. Lavater (8 C. B. N. s. 184), where it was unsuccessfully contended that the assignee of two several moieties of a patent had not a sufficient legal interest to sue for its infringement.

A simple licence, not containing covenants, need not be under seal (Chanter v. Dewhurst, 12 M. and W. 823); nor, it seems, if it be not a deed, does it require a stamp (Chanter v. Johnson, 14 M. and W. 408). Otherwise a stamp of 10s. must be impressed in ordinary cases, and an ad valorem stamp on the consideration-money when a fixed sum is paid.

The 35th section of the Patent Law Amendment Act, 1852, requires all assignments of letters patent, and of any interest therein, and all licences to be registered,

and provides that until such registration, the grantee of the letters patent shall be deemed the sole proprietor of the exclusive privileges thereby given.

Under this clause it has been held that an assignee cannot bring an action for an infringement against third parties until his assignment has been registered (Chollett v. Hoffman, 7 E. & B. 636). But an assignee of a patent may maintain a suit against the assignor and subsequent licences of the assignor with notice of the assignment to restrain them from using the patent, although at the time of the institution of the suit the assignment had not been registered (Hassall v. Wright, L. R. 10 Eq. 509). And from the same case it seems that registration relates back to the date of the assignment, so as to enable the assignee to maintain a suit to restrain infringement instituted between the dates of the assignment and registration. When the executors of a patentee obtained probate of their testator's will and assigned his patent, but the probate was not registered till after the assignment, it was held that the assignment was valid (Ellwood v. Christy, 10 Jur. N. s. 1079; S. C. 11 L. T. N. s. 342).

The Master of the Rolls under this section ordered the registry of a second assignment of a patent to be expunged on the application of the assignees under a prior assignment, which had not been registered until after the second, as it appeared that the second assignment had been executed for a fraudulent and improper purpose (Re Green's Patent, 24 Bea. 145). In another case, the Master of the Rolls said, that if there were two deeds assigning the patent simpliciter to two different persons, and the second was registered before the first, and if it were clearly proved that the second deed was executed with full and complete notice of the prior one, though subsequently registered, he conceived he should have power to direct

an entry to be made upon the register, stating the facts. It is the duty of the Court, under this section of the Act, to insert on the register any facts relating to the proprietorship, but not the legal inferences to be drawn from them (Re Morey's Patent, 25 Bea. 58). One of two joint patentees assigned by deed his interest in the patent to a third person, and released him from all claims on the part of both patentees. At the instance of the other patentee the Master of the Rolls ordered the entry of the assignment to be expunged (Re Horsley and Knighton's Patent, L. R. 8 Eq. 475).

In the matter of the same patent (L. R. 4 Ch. 784) it was decided that there was no appeal from such an order of the Master of the Rolls. But the jurisdiction having now been transferred to the High Court of Justice (Re Morgan's Patent, 24 W. R. 245), it would seem to be subject to appeal.

It is the practice of the Patent Office to register all instruments presented to them relating in any manner to patents which have been completed, on payment of a fee of five shillings upon each instrument; but the office declines to register any instrument relating to inventions only provisionally protected.

The office will register deeds of trust if presented for that purpose; but it is not the general practice to register such documents.

CHAPTER XIV.

INFRINGEMENTS.

THE question of infringements has already been touched upon in a preceding chapter in connection with the question of the novelty of an invention. In this chapter the first section will treat of the practice connected with the proceedings in actions for infringements in the High Court of Justice; and the second will be devoted to a discussion of the substantive law and the decided cases.

§ 1. The Practice.

When a patentee's rights had been infringed, it was formerly matter for consideration whether he should proceed at Law, or in Equity, or in the Courts both of Law and Equity at the same time. If his object was only damages for past infringements, his course was to bring an action at Common Law; but if he required an injunction to restrain future infringements, or an inspection, or an account of profits, he was compelled to proceed in a Court of Equity. Recent legislation, and especially the Judicature Acts of 1873 and 1875, have, however, abolished the distinction between the Courts of Law and Equity, and a patentee may now obtain an injunction, an inspection, and an account, or damages, in any division of the High Court of Justice.

The power to order an injunction, inspection, or account was first conferred on the old Courts of Common Law by the Patent Law Amendment Act (15 & 16 Vict. c. 83), the 42nd section of which enacts that