an officer of the Army of the United States, engaged in the duty of making or causing to be made guns or gun carriages for the Army of the United States. This, it is contended, is demonstrated to be the case by considering that the right to enjoin the officer of the United States, which the court below upheld, virtually asserts the existence of a judicial power to close every arsenal of the United States. On the other hand, the plaintiff insists that the act of the officer in wrongfully attempting to take its property cannot be assumed to be a governmental act, but must be treated as an individual wrong which the courts have the authority to prevent. The exertion of the power to enjoin a wrong of that nature in order to prevent the illegal conversion of private property is, it is urged, a manifestly different thing from using the process of injunction to interfere with property in the possession of the Government and which is being used for a public purpose. But we do not think, under the conditions which presently exist, we are called upon to consider the correctness of the theory upon which the Court of Appeals placed its decision or the soundness of the contentions at bar by which that theory is supported on the one hand or assailed on the other. We reach this conclusion because since October 7, 1908, when the decision of the Court of Appeals was rendered, the subject to which the controversy relates was dealt with by Congress by a law enacted on June 25, 1910, 36 Stat., c. 423, p. 851, as follows: "An Act To provide additional protection for owners of patents of the United States, and. for other purposes.

"Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled, That whenever an invention described in and covered by a patent of the United States shall hereafter be used by the United States without license of the owner thereof or lawful right to use the same, such owner may recover reasonable compensation for such use by suit in the Court

of Claims: Provided, however, That said Court of Claims shall not entertain a suit or reward [sic] compensation under the provisions of this Act where the claim for compensation is based on the use by the United States of any article heretofore owned, leased, used by, or in the possession of the United States: Provided further, That in any such suit the United States may avail itself of any and all defenses, general or special, which might be pleaded by a defendant in an action for infringement, as set forth in Title Sixty of the Revised Statutes, or otherwise: And provided further, That the benefits of this Act shall not inure to any patentee, who, when he makes such claim is in the employment or service of the Government of the United States; or the assignee of any such patentee; nor shall this Act apply to any device discovered or invented by such employé during the time of his employment or service."

The text of this statute leaves no room to doubt that it was adopted in contemplation of the contingency of the assertion by a patentee that rights secured to him by a patent had been invaded for the benefit of the United States by one of its officers, that is, that such officer under the conditions stated had infringed a patent.

The enactment of the statute, we think, grew out of the operation of the prior statute law concerning the right to sue the United States for the act of an officer in infringing a patent as interpreted by repeated decisions of this court. United States v. Palmer, 128 U. S. 62; Schillinger v. United States, 155 U. S. 163; United States v. Berdan Fire-Arms Mfg. Co., 156 U. S. 552; Russell v. United States, 182 U. S. 516; Harley v. United States, 198 U. S. 229. The effect of the statute was thus pointed out in the last cited case. (198 U. S. p. 234.)

"We held in Russell v. United States, 182 U. S. 516, 530, that in order to give the Court of Claims jurisdiction, under the act of March 3, 1887, 24 Stat. 505, c. 359,

defining claims of which the Court of Claims had jurisdiction, the demand sued on must be founded on 'a convention between the parties—a coming together of minds.' And we excluded, as not meeting this condition, those contracts or obligations that the law is said to imply from a tort. Schillinger v. United States, 155 U. S. 163; United States v. Berdan Fire-Arms Mfg. Co., 156 U. S. 552."

In other words, the situation prior to the passage of the act of 1910 was this. Where it was asserted that an officer of the Government had infringed a patent right belonging to another-in other words, had taken his property for the benefit of the Government-the power to sue the United States for redress did not obtain unless from the proof it was established that a contract to pay could be implied that is to say, that no right of action existed against the United States for a mere act of wrongdoing by its officers. Evidently inspired by the injustice of this rule as applied to rights of the character of those embraced by patents, because of the frequent possibility of their infringement by the acts of officers under circumstances which would not justify the implication of a contract, the intention of the statute to create a remedy for this condition is illustrated by the declaration in the title that the statute was enacted "to provide additional protection for owners of patents." To secure this end, in comprehensive terms the statute provides that whenever an invention described in and covered by a patent of the United States "shall hereafter be used by the United States without license of the owner thereof or lawful right to use the same, such owner may recover reasonable compensation for such use by suit in the Court of Claims." That is to say, it adds to the right to sue the United States in the Court of Claims already conferred when contract relations exist the right to sue even although no element of contract is present. And to render the power thus conferred efficacious the statute endows any owner of

a patent with the right to establish contradictorily with the United States the truth of his belief that his rights have been in whole or in part appropriated by an officer of the United States, and if he does so establish such appropriation that the United States shall be considered as having ratified the act of the officer and be treated as responsible pecuniarily for the consequences. These results of the statute are the obvious consequences of the power which it confers upon the patentee to seek redress in the Court of Claims for any injury which he asserts may have been inflicted upon him by the unwarranted use of his patented invention and the nature and character of the defences which the statute prescribes may be made by the United States to such an action when brought. The adoption by the United States of the wrongful act of an officer is of course an adoption of the act when and as committed, and causes such act of the officer to be, in virtue of the statute, a rightful appropriation by the Government, for which compensation is provided. In substance, therefore, in this case, in view of the public nature of the subjects with which the patents in question are concerned and the undoubted authority of the United States as to such subjects to exert the power of eminent domain, the statute, looking at the substance of things, provides for the appropriation of a license to use the inventions, the appropriation thus made being sanctioned by the means of compensation for which the statute provides.

This being the substantial result of the statute, it remains only to determine whether its provisions are adequate to sustain and justify giving effect to its plain and beneficent purpose to furnish additional protection to owners of patents when their rights are infringed by the officers of the Government in the discharge of their public duties. This inquiry may be solved, under the conditions here involved, by taking the most exacting VOL. CCXXIV-20

aspect of the well established and indeed elementary requirements in favor of property rights essential to be afforded in order to justify the taking by government of private property for public use.1 Indisputably the duty to make compensation does not inflexibly, in the absence of constitutional provisions requiring it, exact, first, that compensation should be made previous to the taking— that is, that the amount should be ascertained and paid in advance of the appropriation-it being sufficient, having relation to the nature and character of the property taken, that adequate means be provided for a reasonably just and prompt ascertainment and payment of the compensation; second, that, again always having reference to the nature and character of the property taken, its value and the surrounding circumstances, the duty to provide for payment of compensation may be adequately fulfilled by an assumption on the part of government of the duty to make prompt payment of the ascertained compensation-that is, by, the pledge, either expressly or by necessary implication, of the public good faith to that end.

Coming to apply these principles and confining ourselves in their application, as we have done in their statement, strictly to the conditions here before us, that is, the intangible nature patent rights of the property taken, the great possibilities in the essential operations of government that such rights may be invaded by incorporating them into property of a public character, of the vital public interest involved in the subject-matter of the patents in question and the grave detriment to the very existence of government which might result from interference with the right of the Government to make and use

1 United States v. Russell, 13 Wall. 623; Cherokee Nation v. Southern Kan. Ry. Co., 135 U. S. 641; Sweet v. Rechel, 159 U. S. 380; see Lewis' Eminent Domain, 3d ed., vol. 2, §§ 675, 679, and Cooley Cons. Lim., 7th ed., p. 813.