delivered the opinion of the Court:

This is an appeal from a judgment dismissing a petition for writ of mandamus. The petitioners moved for judgment notwithstanding the return made to the alternative writ, which was denied, and, having declined to amend or to traverse the return, their petition was dismissed.

It appears that Walter Scott filed an application, December 15, 1904, for a patent for an improvement in printing machines. Applicant died testate, and petitioners qualified as executors of his will. On May 24, 1909, they filed an application as a division of the earlier application of their testator. In this application they copied certain claims of a patent to Bechman, issued March 6, 1906. March 22, 1910, an interference was declared with Bechman with an issue embodying these claims. Bechman moved to dissolve the interference on the ground that petitioners had no right to make the claims. A stipulation in the record recites that the right to make the claims depends on the disclosure of the earlier application, and that the same is indirectly involved in the interference. Petitioners thereby became the senior parties. The motion was sustained by the several tribunals of the office in succession. The decision of the Commissioner dissolving the interference was rendered July 13, 1911.

After this decision the petitioners moved the Examiner of Interferences to set the case down for hearing, and to take testimony for use at such hearing. This was denied, and on regular appeal to the Commissioner he affirmed the action of the tribunals below, on the ground that the interference had been dissolved, without an award of priority. Claiming that it was the plain, imperative duty of the Commissioner to cause the interference to be set down for hearing before the Examiner of Interferences, and that they have no other remedy, petitioners pray a writ of mandamus to compel the performance of that duty.

The effect of the Commissioner’s decision sustaining the motion to dissolve the interference put an end to it. There was no longer an issue between the parties upon which testimony could be taken.

*42Grant that petitioners had no appeal to this court from the order as entered, because there was no award of priority (Cosper v. Gold, 34 App. D. C. 194-198); yet, as stated in the Commissioner’s decision, on September 26, 1911, had the petitioners requested that the former decision be extended to a formal award of priority, that order would have been entered, as had been done in Gosper v. Gold, supra, after the dismissal of the appeal from the former decision holding that the appellant Gos-per had no right to make the claims of the interference. Had the petitioners pursued that course, an appeal could have been taken from the final award of priority, bringing up for review all the grounds upon which the award was founded. Cosper v. Gold, 36 App. D. C. 302-307.

Having failed to take this action, and obtain a review of the exercise of the Commissioner’s judicial discretion in the manner provided therefor by law, the petitioners now seek a review of his decision by means of mandamus. Mandamus cannot be made to operate as an appeal or writ of error.

The judgment was right, and will be affirmed, with costs.

Affirmed.

An application by the appellants for the removal of the cause to the Supreme Court of the United States, by writ of error, was denied May 30, 1912.