Statement of the Case. 244 U. S. THIS writ is directed to a judgment of the Court of Appeals of the District of Columbia which affirmed a judgment of the Supreme Court of the District of Columbia in mandamus commanding the Commissioner of Patents "to declare or direct to be declared an interference between the application of William E. Fowler, Sr., filed May 22, 1915, for Improvements in Car Floor Construction, and the application for a similar invention" of an unnamed applicant "pursuant to the statute and rules in such cases made and provided." The judgment was rendered upon motion of petitioner's attorney upon the petition, rule to show cause and answer. It was affirmed by the Court of Appeals. As the Fowler Car Company and Ewing, Commissioner of Patents, were petitioner and respondent, respectively, in the court below, we shall so designate them here. The facts as stated by the petition are as follows: William E. Fowler, Sr., was the first and original inventor of certain new and useful improvements in car floor construction. On May 22, 1915, he applied for a patent in the usual form and manner and his application was accepted and became known and designated as application serial No. 29794. On May 19, 1915, he duly assigned his right, title and interest in the invention to the Fowler Car Company, which company appointed Charles C. Linthicum its attorney. On November 18, 1915, the Commissioner of Patents wrote to Linthicum stating that "there is another application pending, claiming substantially the same invention as that defined" in certain of the claims which were set out. He further stated: "In order to determine whether it is necessary to declare an interference you are requested to obtain a statement from Fowler setting forth when he conceived the invention defined in the above quoted claims, when he disclosed it to others, and when he re 244 U. S. Statement of the Case. duced it to practice. This statement will not be made a part of the record and will be returned to you." Fowler replied that he had conceived the subject-matter of the claim quoted in the Commissioner's letter on or about April 16, 1915, disclosed the same to others and made drawings on or about the same date but had not reduced the same to practice by constructing any fullsized devices. On November 23, 1915, Linthicum filed an amendment to Fowler's application in which all of the claims suggested by the Commissioner were inserted. Of these claims Linthicum said: "It is thought that these claims appear in a co-pending application and they are inserted at this time with the request that, if such claims do appear in a co-pending application an interference be declared." To this communication the Commissioner replied as follows: "Sir: Enclosed please find the statement of William E. Fowler, Sr., made in response to the request in my letter of November 18, 1915. "The dates of invention claimed by Fowler are subsequent by several months to the filing date of the application of the other party. The other party's case will be passed to issue as soon as possible and when patented will be cited as a reference against such claims in Fowler's application as it may be found to anticipate. An interference will not be declared." Section 483, Rev. Stats., provides: "The Commissioner of Patents, subject to the approval of the Secretary of the Interior, may from time to time establish regulations, not inconsistent with law, for the conduct of proceedings in the Patent-Office." Pursuant to this authority regulations known as "Rules of Practice in the United States Patent Office" have been established by the Commissioner by and with the approval of the Secretary of the Interior and now govern Statement of the Case. 244 U. S. the declaration of interferences between pending conflicting applications and have the force and effect of law, binding as well upon the Commissioner as upon the applicant for patents. It is further alleged that it clearly appears from the correspondence recited and under the statute and rules that an interference exists between the Fowler application and that of the applicant unknown to petitioner, which applications disclose and claim the same patentable invention and it is the duty of the Commissioner to declare an interference and to call upon each applicant for the sworn preliminary statement required by Rule 110. That if the unknown applicant receive a patent and thereafter petitioner's (Fowler's) application is put in interference with it and petitioner afterwards be awarded priority over the unknown applicant and receive a patent, in order to get rid of the menace of the outstanding patent to such unknown applicant petitioner will have to file a bill in equity under the provisions of § 4918, Rev. Stats., for the cancellation of such patent or the owner of the outstanding patent may file such bill against petitioner, all of which possibility of litigation may be prevented if the Commissioner be required to discharge his plain duty under the statute and rules and declare an interference when the rights of both parties are in the application stage and before either party receives a patent. That conduct of the Commissioner is a matter of public concern and for over a quarter of a century his predecessors have, without exception, regarded the interference rules as imposing upon them the legal duty of declaring an interference under the circumstances detailed. And petitioner is advised and believes that unless the Commissioner be restrained a patent in due course will be issued to the unknown applicant and petitioner is without remedy unless the court by writ of mandamus shall interpose in its behalf. A rule to show cause was issued and the Commissioner's action stayed until the determination of the cause. The Commissioner in his answer admitted the filing of the applications as alleged and the correspondence with Linthicum, but denied the legal conclusion drawn by petitioner therefrom. He alleged that an interference as defined by the rules of the patent office is a proceeding for the purpose of determining the question of priority of invention and that when an applicant informs the office that the invention shown in his application was made at a date which was subsequent to the date upon which another application for the same invention was filed, the statute does not require that an interference be established between his application and the prior application. That in asking the later applicant to inform the office of the date of its invention the Commissioner was only asking for information upon which he might form, as required by § 4904, Rev. Stats., an opinion whether a situation existed where the statute required that the later application should be put into interference with the earlier application, and that the rules do not require or contemplate a declaration of interference where it is known that the later applicant made his invention subsequently to the filing of the earlier application; in other words, they do not contemplate the declaration of an interference except where there is a possible conflict in the dates of invention. The answer further denied that petitioner had shown injury or threatened injury and alleged that the only injury averred in the petition was that if the application of petitioner be put in interference with the patent granted upon the other application, and if priority should be awarded to petitioner and a patent granted to it a bill in equity under § 4918, Rev. Stats., would be necessary to get rid of the menace of the outstanding patent. Tha. the date of Fowler's invention being subsequent to the filing date of the other party, there would be no ground of awarding priority to Fowler. That even if interference should be declared, "a litigation to be conducted between the application owned by the petitioner and the patent issued to the other party would be no longer or more expensive than a litigation to be conducted between the two applications. No suit could be brought under section 4918 of the Revised Statutes either by or against this petitioner, unless it were proved that Fowler was the first inventor and a patent issued to him; but, as above stated, the date upon which Fowler states he conceived the invention is subsequent to the date upon which the other application was filed." There was detail of the business of the Patent Office and of the inconvenience to its administration if the right insisted upon by petitioner were allowed. A discharge of the rule was prayed. The Solicitor General, with whom Mr. Assistant Attorney General Warren and Mr. R. F. Whitehead were on the brief, for petitioner. Mr. George L. Wilkinson, with whom Mr. Melville Church was on the brief, for respondent. MR. JUSTICE MCKENNA, after stating the case as above, delivered the opinion of the court. The case is not in broad compass. It depends upon a few simple elements. Section 4904, Rev. Stats., provides: "Whenever an application is made for a patent which, in the opinion of the Commissioner, would interfere with any pending application, or with any unexpired patent, he shall give notice thereof to the applicants, or applicant and patentee, as the case may be, and shall direct the primary examiner to proceed to determine the question |