Mr. Justice Shepard
delivered the opinion of the Court:
1. This is an appeal from a judgment of the Supreme Court of the District of Columbia dismissing a petition for a writ of mandamus to the Commissioner of Patents.
The relator, Alfred L. Bernardin, and William H. Northall were parties to an interference proceeding in the Patent Office declared on their respective applications for a patent for an improvement in bottle-sealing devices.
The Commissioner of Patents being of opinion that Bernardin was the first inventor rendered a decision in his favor. [71 O. G. 1159.] On appeal to this court by Northall the decision of the Commissioner was reversed. 7 App. D. C. 452. Bernardin, denying the jurisdiction of this court to entertain an appeal from the decision of the Commissioner, demanded the patent to which he was entitled thereunder. This demand was refused because of the reversal of that decision by this court and the award of priority to North all. [75 O. G. 1853.]
The sole question to be determined is the jurisdiction of this court to entertain appeals from the Commissioner of Patents, for without setting out the pleadings, it is sufficient to say, that they make a case in which the mandamus ought to issue, if Congress had not the power to confer that jurisdiction, under the rule laid down in Butterworth v. Hoe, 112 U. S. 50.
[304]*304The argument against the constitutionality of the act of Congress is founded in the complete separation and independence of the powers of government declared in the Constitution.
In the language of Mr. Justice Miller: “It is believed to be one of the chief merits of the American system of written constitutional law, that all the powers entrusted to government, whether State or national, are divided into the three grand departments, the executive, the legislative, and the judicial. That the functions appropriate to each of these branches of government shall be vested in a separate body of public servants, and that the perfection of the system requires that the lines which separate and divide these departments shall be broadly and clearly defined. It is also essential to the successful working of this .system that the persons entrusted with power in any one of these branches shall not be permitted to encroach upon the powers confided to the others, but that each shall, by the law of its creation, be limited to the exercise of the powers appropriate to its own department and no other.”
After noting several exceptions to the general rule expressly provided in the Constitution, he says again: “In the' main, however, that instrument, the model on which are constructed the fundamental laws of the States, has blocked out with singular precision, and in bold lines, in its three primary articles, the allotment of power to the executive, the legislative, and the judicial departments of government. It also remains true, as a general rule, that the powers confided by the Constitution to one of these departments can not be exercised by another.” Kilbourn v. Thompson, 103 U. S. 168, 190.
The contention on behalf of the appellant is therefore that the Commissioner of Patents is an officer of the executive department, clothed with functions and charged with duties, executive in their character, and that the exercise of his judgment and discretion therein is beyond the control [305]*305of the judiciary and cannot be conferred thereon by act of the legislative department with the approval of the President.
The question as presented is one of importance, and its rightful determination is a matter of grave doubt. If resolved against the exercise of the jurisdiction, there will doubtless be some embarrassing, if not injurious, consequences, for it has been constantly exercised by the courts of this District since the year 1839, and of late years especially many decisions of the courts upon appeal from the Commissioner of Patents have been carried into effect and accepted as conclusive and final. Notwithstanding the grave doubt that we entertain of the soundness of our judgment, we . are not convinced that it is our duty to declare against the validity of the statute conferring the jurisdiction.
The very fact that we entertain doubt is of itself sufficient ground for our action in upholding the power of Congress to enact the law. “It is our duty, when required in the regular course of judicial proceedings, to declare an act of Congress void if not within the legislative power of the United States; but this declaration should never be made except in a clear case. Every possible presumption is in favor of the validity of a statute, and this continues until the contrary is shown beyond a reasonable doubt. One branch of the government cannot encroach on the domain of another without danger. The safety of our institutions depends in no small degree on a strict observance of this salutary rule.” Sinking Fund Cases, 99 U. S. 700, 718. See also Powell v. Pennsylvania, 127 U. S. 678, 684.
The concluding sentences of the foregoing quotation show that the rule therein enounced is founded on the very same principle that lies at the base of the appellant’s contention here.
The first act conferring jurisdiction on the court of this District of appeals from .the Commissioner of Patents was approved March 3, 1839, and the same has been exercised [306]*306with some changes in procedure only continuously since that time. During nearly sixty years of existence the validity of the law remained unassailed and unquestioned. Moreover, the validity^ of this legislation was unmistakably assumed by the Supreme Court of the United States in the very case of Butterworth v. Hoe, supra, wherein it was held that the express grant of an appeal from the decisions of the Commissioner to the courts precluded 'the exercise of the appellate jurisdiction claimed by the head of the department to which the Patent Office is attached — namely, the Secretary of the Interior.
In consideration of the importance of the question and the points made in the able argument upon which it has been submitted we think it proper to offer some additional reasons in support of our conclusion.
The Constitution of the United States confers upon Congress the power “to promote the progress of science and useful arts by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries.” Art. 1, Sec. VIII.
Vested with this power it became the duty of Congress to carry it into execution by appropriate legislation. To that end it was vested with discretion to adopt any means or plan suitable for the purpose not inconsistent with the letter or spirit of the Constitution. McCulloch v. Maryland, 4 Wheat. 316; Interstate Commerce Commission v. Brimson, 154 U. S. 447, 472, 473.
The first act of Congress, A. D. 1790, conferred the power to issue patents upon the Secretaries of State and War and the Attorney General or any two of them. The act of 1793 authorized them to issue by the Secretary of State upon a certificate of the Attorney General that they conformed to the act, and the parties in cases of interference were authorized to select arbitrators for the determination of the controversy. By the act of 1836 the Patent Office was created in the Department of State and given in charge of an [307]*307officer called the “ Commissioner of Patents.” Appeals from him were given to a board of examiners, and by Section 16 of the same act a remedy by bill in equity was given, as now provided in Revised Statutes, Sections 4915, 4918.
By the act of March 3, 1839, an appeal was given from the Commissioner to the chief justice or either of the associate judges of the Circuit Court of the District of Columbia. By the act of 1849 the Patent Office was transferred to the Department of the Interior. Amendments were from time to time made in the law,' and several tribunals were provided in the office for examination and inquiry into the merits of claims for inventions, with appeal from one to another and then fmalty to the Commissioner. The appeal from the Commissioner in all cases of refusal of patent was continued in the courts of the District of Columbia, with such changes as were necessary through the changes made in the judicial system thereof. Finally, by the act approved February 9, 1893 (27 Stat. at Large, 434), creating the Court of Appeals of the District of Columbia, the determination of appeals from the Commissioner of Patents as formerly vested in the General Term of the Supreme Court of the District was vested therein, and in addition it was provided that “ any party aggrieved by a decision of the Commissioner of Patents in any interference case may appeal therefrom to said Court of Appeals.” Sec. 9.
It was under this clause that the appeal was taken in Northall v. Bernardin, that is now the subject of discussion.
Under the law the functions of the Commissioner of Patents are both executive or administrative and judicial, the latter preponderating in importance. In matters administrative merely he is under the supervision of the Secretary of the Interior, but when acting judicially, so to speak, his decisions can only be reviewed by the court. Butterworth v. Hoe, 112 U. S. 50, 66, 67. In that case Mr. Justice [308]*308Matthews, after a review of the provisions of the patent law, said:
“It thus appears, not only that the judgment and discretion of the Commissioner, as the head of the Patent Office,, is substituted for that of the head of the Department, but also, that that discretion and judgment are not arbitrary, but are governed by fixed rules of right, according to which the title of the claimant appears from an investigation for the conduct of which ample and elaborate provision is made; and that his discretion and judgment, exercised upon the material thus provided, are 'subject to review by judicial tribunals whose jurisdiction is defined by the same statute. . . . It is not consistent with the idea of judicial action that it should be subject to the action of a superior, in the sense in which that authority is conferred upon the head of an executive department in reference to its subordinates. Such a subjection takes from it the equality of a judicial act. That it was intended that the Commissioner of Patents, in issuing, or withholding patents, in reissues, interferences and extensions, should exercise quasi-judicial functions, is apparent from the nature of the examinations and decisions he is required to make, and the modes provided by law, according to which, exclusively, they may be reviewed.”
In the cases of issuing or withholding patents, reissues and extensions, the judicial function is exercised in investigating the proofs and determining the right as between the claimant, on one hand, of what may be a valuable right of property, and the public, on the other, interested in defeating what may be an unlawful monopoly. In interference cases the proceeding is distinctly judicial. The controversy is waged between adverse claimants of the same right of property, and the public has no interest therein. It contains “ all the elements of a civil case — a complainant, a defendant and a judge — actor, reus et judex.” Fong Yue Ting v. U. S., 149 U. S. 698, 729.
[309]*309In this view of the most important of the duties devolved upon the Commissioner of Patents there would seem to be no convincing reason why Congress might not have established the Patent Office as a separate and independent special judicial tribunal for the investigation of the claims of inventors and the adjudication of their rights as against the public at large or adverse claimants of the same invention. Had it seen proper so to do, it might then have given or denied the right of review to any of the courts of general jurisdiction created by or under Section 1 of Article III of the Constitution. In Murray v. Hoboken Land and Imp. Co., 18 How. 272, 284, which was a case involving the validity of a sale of land made by a United States marshal under a distress warrant issued by the solicitor of the United States Treasury against a collector of customs for a debt due the United States, Mr. Justice Curtis, speaking for the entire court, said:
“To avoid misconstruction upon so grave a subject, we think it proper to state that we do not consider Congress can either withdraw from judicial cognizance any matter which, from its nature, is the subject of a suit at the common law, or in equity, or admiralty; nor, on the other hand, can it bring under the judicial power a matter which, from its nature, is not a subject for judicial determination. At the same time there are matters, involving public rights, which may be presented in such form that the judicial power is capable of acting on them, and which are susceptible of judicial interpretation, but which Congress may or may not bring within the cognizance of the courts of the United States, as it may deem proper.”
The court of private land claims established for a limited period by the act of March 3, 1891 (26 Stat. 854), is a special tribunal of the kind referred to above, and the act creating it and giving the right of appeal therefrom to the Supreme Court of the United States has been upheld by that court. United States v. Coe, 155 U. S. 76, 85. In that case it was [310]*310said by the Chief Justice: “It must be regarded as settled that Section 1 of Article III does not exhaust the power of Congress to establish courts.”
Before the creation of the Court of Claims in 1855 there was no way in which the justice of a claim against the United States could be judicially ascertained and established. Congress might recognize and pay them or not, according to its own view of justice and legality in the premises. It could and did also submit claims to investigation, allowance and payment by the officers of the executive departments. Recognizing the justice and expediency of providing a regular tribunal wherein claims against the United States might be investigated, heard, and determined in accordance with the forms of law, the Court of Claims was created and vested with jurisdiction in certain cases of the kind, the scope of which has been increased from time to time. The claims submitted to adjudication were such as no court could take jurisdiction of without the express consent of Congress, because the controversy was with the Government. The forms of procedure excluded trial by jury. Appeals taken to the Supreme Court of the United States were determined upon questions of law arising on the findings of fact made by the court. At the same time by special enactment any appeal could be made determinable upon both facts and law, as in equity cases. Harvey v. United States, 105 U. S. 671, 691.
Referring to a provision of the act of March 3,1863, conferring power on the Courf of Claims to render judgment against a claimant upon any plea of set off, counter claim, and so forth, offered by the United States without trial by jury, Mr. Justice Harlan said: “There is nothing in these provisions which violates either the letter or spirit of the Seventh Amendment. Suits against the Government in the Court of Claims, whether reference be had to the claimant’s demand, or to the defence, or to any set off, or counter claim which the Government may assert, are not controlled by the [311]*311Seventh Amendment. They are not suits at common law within its true meaning. The Government cannot be sued, except with its own consent. It can declare in what court it may be sued, and prescribe the forms of pleading and the rules of practice to be observed in such suits. It may restrict the jurisdiction of the court to a consideration of only certain classes of claims against the United States.” McElrath v. United States, 102 U. S. 426, 440.
In Gordon v. United States, 2 Wall. 561; S. C. 117 U. S. (Appendix) 697, which is one of the cases strongly relied on by the appellant, the majority of the court refused to entertain an appeal from the Court of Claims. The appeal was dismissed on the ground that Congress could not authorize or require the Supreme Court “to express an opinion on a case where its judgment would not be final and conclusive upon the rights of the parties, and process of execution awarded to carry it into effect.”
In re Sanborn, also, 148 U. S. 222, 226, the court held that it had no jurisdiction to entertain an appeal from the Court of Claims, because the act authorizing the transmission of the claim for investigation by that court required its report to be made to the head of the department transmitting the claim for his information, but without being binding upon him. Finding this to be the meaning of the act, the court said: “ We regard the function of the Court of Claims, in such a case, as ancillary and advisory, merely. The finding or conclusion reached by that court is not enforceable by any process of execution issuing from the court, nor is it made, by the statute, the final and indisputable basis of action either by the department or by Congress-It is therefore within the scope of the decision of Gordon v. United States.”
After referring to the cases of United States v. Yale Todd and United States v. Ferreira, 13 How. 52, wherein the action required of a district j udge in certain cases amounted not to a judgment, but to a mere award, subject to be reviewed by [312]*312the Secretary of the Treasury, Mr. Justice Shiras, speaking for the court in the same case, p. 225, said: “Afterward, and perhaps in view of the conclusion reached by the court in those cases, on March 17, 1866, Congress passed an act giving an appeal to the Supreme Court from judgments of the Court of Claims, and repealing those provisions of the act of March 3, 1863, which practically subjected the judgments of the Supreme Court to the re-examination and revision of the departments, and since that time no doubt has been entertained that the Supreme Court can exercise jurisdiction on appeal from final judgments of the Court of Claims. United States v. Alire, 6 Wall. 573; United States v. O’Grady, 22 Wall. 641; United States v. Jones, 119 U. S. 477.”
In an article by Mr. Edward B. Whitney in the Yale Law Review, October, 1896, entitled “Federal Judges and Quasi-Judges,” to which we are much indebted, the various phases of this vexed question as suggested in the acts of Congress and decisions thereunder are discussed in an interesting and instructive manner. After quoting from the opinion of Chief Justice Taney in Gordon v. United States, he says: “A hearing and decision by such a court is strictly judicial in its nature when Congress does permit the United States to be sued; and when its decision is unreviewable by the executive it may be made feviewable by the superior courts. Hence, although the Chief Justice rightly said that the Supreme Court’s power ‘is exclusively judicial, and it cannot be required or authorized to exercise any other,’ nevertheless that court for thirty years past has had and constantly exercised power to review decisions of the Court of Claims when appealed; and by the recent Tucker act (March 1, 1887) the circuit and district courts of the United States now exercise a jurisdiction concurrent with that of the Court of Claims.” Turning to later legislation concerning controversies between the Government and private persons, he says: “Another quasi-judicial tribunal, passing upon questions as to which the United States [313]*313are parties interested, is the board of general appraisers sitting at New York. The decisions of this board as to the valuation of imported goods are final. Upon questions of classification they are subject to review by the courts. Their opinions are printed in the Treasury publication entitled ‘Synopsis of Decisions.’”
In the recent case of Interstate Comm. Comm. v. Brimson, 154 U. S. 447, where the majority of the court sustained the validity of the twelfth section of the interstate commerce act authorizing the circuit courts to use their process in aid of inquiries before that commission, the question as to how far Congress, in the execution of other express powers, can go in imposing upon the courts of the United States duties in aid of an executive or administrative body, was again exhaustively discussed in both the opinion of the court and the dissenting opinion of Mr. Justice Brewer. Mr. Justice Harlan, delivering the opinion for the majority, after a careful statement of the doctrine of the cases of Hayburn, Yale Todd, Ferreira and Gordon, upon which the appellant here relies, said: “The views we have expressed in the present case are not inconsistent with anything said or decided in those cases.” 154 U. S., p. 485.
Again he says, referring to the aid of the court as therein invoked (p: 487): “The present proceeding is not merely ancillary and advisory. It is not, as in Gordon’s case, one in which the United States seek from the circuit court of the United States an opinion that‘would remain a dead letter and without any operation upon the rights of the parties.’ The proceeding is one for determining rights arising out of specified matters in dispute that concern both the general public and the individual defendants.”
Discussing the nature of this determination he says: “It is none the less the judgment of a judicial tribunal dealing with questions judicial in their nature, and presented in the customary forms of judicial proceedings, because its effect may be to aid an administrative or executive body in the [314]*314performance of duties legally imposed upon it by Congress in execution of a power granted by the Constitution.”
Under the authority of that case a district judge has been compelled by mandamus to compel the attendance of witnesses before special examiners of the Pension Bureau in aid of an investigation of a claim therein. In re Lochren, 163 U. S. 693.
It cannot be claimed that the decision invoked by appeal from the Commissioner of Patents to this court is not final and conclusive in the matter. “The Commissioner cannot question it. He is bound to record and obey it. His failure or refusal to execute it by appropriate action would undoubtedly be corrected and supplied by suitable judicial process. The decree of the court is the final adjudication upon the question of right; everything after that depending upon it is merely in execution of it. It is no longer matter of discretion, but has become imperative and enforceable. It binds the whole department, the Secretary as well as the Commissioner, for it has settled the question of title, so that a demand for the signatures necessary to authenticate the former instrument and evidence of grant may be enforced.” Butterworth v. Hoe, 112 U. S., p. 60.
Then, if Congress, which seems clear, could have created a distinct special tribunal, proceeding after the manner of a court of law or equity, for the adjudication of claims to patents of inventions, there would seem to be no convincing reason why it could not, without violating the Constitution, make it a branch or bureau of an executive department, subject to supervision in matters administrative only by the head of that department and subject to review in matters judicial in their nature by a court of competent jurisdiction.
The Constitution simply declares that “The executive power shall be vested in a President of the United States of America.” By act of Congress certain executive depart: ments have been created to aid the President in the performance of his duties and to act by his authority. That [315]*315there may be a distinct line of separation between the duties with which an executive department is charged is clearly stated by Chief Justice Marshall in Marbury v. Madison, 1 Cranch, 137, 166, from whom we quote :
“In such cases their acts are his acts; and whatever opinion may be entertained of the manner in which executive discretion may be used, still there exists and can exist no power to control that discretion. The subjects are political. They respect the nation, not individual rights, and being entrusted to the Executive, the decision of the Executive is conclusive. . . . But when the legislature proceeds to impose on that officer other duties; when he is directed peremptorily to perform certain acts; when the rights of individuals are dependent on the performance of those acts; he is so far the officer of the law; is amenable to the laws for his conduct; and cannot at his discretion sport away the vested rights of others. The conclusion from this reasoning is, that where the heads of departments are the political or confidential agents of the Executive, merely to execute the will of the President, or rather to act in cases in which the Executive possesses a constitutional or legal discretion, nothing can be more perfectly clear than that their acts are only politically examinable. But when a specific duty is assigned by law, and individual rights depend upon the performance of that duty, it seems equally clear that the individual who considers himself injured has a right to resort to the laws of his country for a remedy.”
The propriety then of judicial interference seems determinable “ not by the office of the person, but the nature of the thing to be done.” Id. 170. It was in view of such a distinct division between the two classes of duties imposéd upon the Commissioner of Patents by the acts of Congress that the conclusion was reached in Butterworth v. Hoe. The supervision of the Secretary of the Interior was held in that' case to be limited to matters purely administrative. Matters judicial in their investigation and determination were [316]*316declared to be under the supervision of the courts. '“It is not consistent,” said Mr. Justice Matthews, “with the idea of judicial action that it should be subject to the direction of a superior, in the seuse in which that authority is conferred upon the head of an executive department in reference- to his subordinates.”
Without further prolonging the discussion of this interesting question, and admitting that we are not without doubt in respect of the soundness of our judgment, we repeat that we have not been able to see our way to the conclusion urged upon us — namely, that the act conferring the right of appeal to this court from the decisions of the Commissioner of Patents is beyond the power of Congress to enact, for the reason that it oversteps the boundaries erected by the Constitution between the three great departments of the Government.
The judgment will therefore be affirmed, with costs; and it is so ordered. Affirmed.