delivered the opinion of the Court:

It is well settled that the duty imposed upon the Commissioner of Patents by sec. 4904, Rev. Stat., Comp. Stat. 1916, secj 9449, to declare an interference, involves the exercise of his judgment upon the facts presented, and cannot be controlled by mandamus. Ewing v. United States, 244 U. S. 1, 61 L. ed. 955, 37 Sup. Ct. Rep. 494. In that case, where it was sought by mandamus to compel the Commissioner to declare an inter*451fercnoe, the court said: “It is to be remembered that the law gives the Commissioner both initial and final power. It is he who is fo cause tlie examination of an asserted invention or discovery and to judge of its utility and importance; it is he who is to judge (be of opinion) whether an application will interfere with a pending one; and it is he who, after an interference is declared and proceedings had, is the final arbiter of its only controversy, — priority of invention. The contentions of petitioner put these powers out of view', put out of view the fact that the so-called (judgment of record’ is, as the action of the Commissioner may be said to be, but a matter of administration.”

Hut relator seeks to escape the general rule that the want of mandamus will not issue to control the discretion of a public officer by invoking the doctrine of estoppel. It is insisted that the dissolution of tlie original interference is res judicata as -to the present interference. It is unnecessary to consider the merits of this contention, since his position is not improved in so far as liis right to relief by mandamus is concerned. The. question of res judicata can be raised and preserved at all stage's of the proceeding's in the prosecution of the present interference. It may be availed of by relafor in the various tribunals of the .Patent Office, through which appeals in interference cases may bo prosecuted, and finally in this court on appeal from the decision of the Commissioner of Patents. Gold v. Gold, 34 App. D. C. 229.

It follows that relator’s right to have the question of former adjudication finally decided by this court on appeal in the interference proceeding forecloses its right to substitute mandamus for the legal, statutory remedy thus provided.

The judgment is affirmed with costs. Affirmed.