delivered the opinion of the ■Court:
But two questions for determination are presented by the •elaborate statement of the reasons of appeal: 1. Is the device described in Pice’s application an operative one? 2. Is Rice the senior party in interference; or, in other words, is he entitled to date back to the filing of his original application on ■June 8, 1895 ?
The question of the operativeness of the device described in the application of the senior party to an interference has been presented to this court twice in different appeals in the same •case. Dodge v. Fowler, 11 App. D. C. 592; Fowler v. Dodge, 14 App. D. C. 411. In the first of those appeals the Commissioner awarded priority to Eowler, and that decision was reversed on the ground that Eowler, though the first to conceive the invention, had failed to exercise due diligence in the matter of reduction to practice prior to the time that Dodge entered the office. Dodge was given the benefit of the application as a *430constructive reduction to practice, but, as the Commissioner had incidentally expressed the opinion that Dodge’s disclosed device was inoperative, the opinion of the court concluded with these words: “We do not desire it to be understood by our decision that Dodge is entitled to a patent for his alleged invention. AVhat we decide is simply that, assuming that Fowler and Dodge have made the same invention independently of each other, and that Dodge has been the first to reduce it to constructive practice by his first application for a patent, we think the question of due diligence should be settled in his favor as against Fowler. From the statements of the Commissioner and the Board of Examiners, the inference to be drawn would seem to be that Dodge’s device is found to be wanting in patent-ability, and therefore that the declaration of interference was based upon mistake or inadvertence. It is true that no motion was made on behalf of Fowler to dissolve the- interference; but if, under the law and the rules of the Patent Office, it is not improper, after adjudication of priority of invention, to refuse a patent to the successful party in the interference proceedings upon grounds that have first been developed in those proceedings, or upon grounds manifested at any time after the declaration of interference, we are not to be understood by this decision as precluding such action by the Office.”
Upon the return of the case to the Patent Office a motion was made by Fowler to dissolve, the interference on the ground that Dodge’s device was inoperative. The Commissioner referred the question to the determination of the expert Primary Examiner in the department to which the art belonged, who decided that -the device was operative. This decision was treated by the Commissioner as finally settling the question of operativeness in Dodge’s favor, and in obedience to the determination of the court on the first appeal, he awarded priority to Dodge. On Fowler’s appeal therefrom the question of operativeness was again raised. In its consideration we then said: “Under the special circumstances of this case we will assume that the appeal fully brings before us for determination * * * the whole question of the operativeness of the Dodge device and its *431patentability.” Patentability, it is obvious, bad reference solely to tbe matter of operativeness. The decision was then affirmed.
Whether a device is operative is a question that necessarily presents itself in every application for a patent referred, in due course of proceeding under the rules of the Office, to the expert examiner of the class to which the alleged invention belongs. Por that reason he is required to be skilled in the particular art. The decision of this examiner in respect of operativeness and other questions affecting patentability, if favorable to the applicant, is subject to the supervising power of the Commissioner only. It is only where the application is rejected for any reason, that an appeal regularly lies to this court in the last resort.
When an application has been allowed as patentable, and an interference declared, each party may raise the question of the operativeness of his opponent’s device by a motion to dissolve the interference, as was done in this case. The question goes again to the Primary Examiner for his reconsideration, but no appeal from his decision, at the time it was rendered in this case, lay to the Examiners-in-Chief. The Commissioner alone could review it. The Examiners-in-Chief have the power, under rule 126, to report to the Commissioner, in the course of their decision in an interference case, that the device of either party is, in their opinion, inoperative, or unpatentable for any other reason. The Commissioner may then, and his general practice has been to, refer the question back to the Primary Examiner for further inquiry and determination. As the statement of the case shows, that practice was followed in this proceeding.
In adopting the conclusion of the Primary Examiner in respect of the operativeness of Dodge’s device in Fowler v. Dodge, supra, the question was merely assumed as being before the court by reason of the peculiar conditions of the case.
As the question of the operativeness of one of the devices of the application now in interference is directly presented to us as an incident of the main question, of priority, we hold that it is not one for our consideration. It is, as we have before in*432•dicated, a preliminary question determinable, in tbe first instance, in tbe case of every application for a patent, and, when determined in favor of tbe applicant, is not appealable. "When determined in bis favor, and an interference is declared thereon with another similarly allowed application, tbe same rule applies. Priority of invention is tbe issue to be determined in an interference proceeding, tbe final decision of which is appealable to this court. The question of operativeness, having been settled in accordance with tbe practice of tbe Patent Office, cannot again be raised as incidental to tbe issue of priority, and brought up therewith for review.
This brings us to the consideration of the remaining question: Is Pice entitled to date back to June 8, 1895, when his original ■application was filed, and thereby become the senior party to the interference ? If so entitled, the decision in his favor must be affirmed on the record.
Duryea and White filed no preliminary statement, and are therefore confined by the record to the filing of their application, on March 21, 1902. It is stated by the Primary Examiner in his decision upon the motion of Duryea and White to dissolve the interference and shift the burden of proof, that Pice’s original application contained claims to both an igniter and an engine, and that “the disclosure therein is identical, so far as the issue is concerned, with that of the pending case.” Neither of these statements has been controverted. We adopt the following extract from his decision as stating correctly the proceedings had in regal’d to that application, and the con-elusions dedueible therefrom:
“Pice’s original application was filed June 8, 1895, No. 552,-163, and contained claims both to the engine and to the igniter, a fact at that time not regarded as necessitating division. The engine claims were rejected, erroneously, it must be held in view of the subsequent decision by the Examiners-in-Chief on the appeal taken by Duryea and White, allowing certain claims now in issue. After prosecution in the usual course, Pice’s application was passed for issue June 18, 1891, was allowed to forfeit, and was renewed July 16, 1898, with additional claims to the *433engine, winch, as is not denied, it was entirely within the applicant’s legal right to present. These additional claims were overlooked by the Office, and the case passed for issue, July 22, 1898, but almost at once, July 27, 1898, withdrawn, and the engine claims were then rejected on references after several actions. On December 30, 1898, the engine claims were rejected, and for the first time division was required between them and claims to the igniter. In responding to this action on March 28, 1899, Nice canceled the engine claims, not, it is to be observed, as anticipated, but in response to the requirement of division; and upon the case so limited, the Office took action April 25, 1899. It was by acceptance of this action only that Nice completed his election of the igniter, and not, as stated by Duryea & White, by his cancelation on March 28, 1899. Ex parte Preston C. D. 1880, p. 125; Johnston C. D. 1887, p. 64; Zabel C. D. 1888, p. 35; Maxim, C. D. 1888, p. 27. At any time up to April 25, 1899, Nice could have reinstated his claims to the engine as a matter of course, and for prosecution by appeal if necessary; after that date he could not do so, unless, perhaps, by clear showing of mistake in the cancelation, or by such acquiescence of the Office as actually occurred. He did, in fact, again present claims to the engine in his amendment of September 28, 1899, responding to the Office action of April 25, 1899. In the Office action (of November 2, 1899) upon the amendment of September 28, 1899, Nice was erroneously informed that he might elect whichever invention he chose, and it was not until October 25, 1900, in the Office letter replying to his amendment of October 12, 1900, that he was informed to the contrary. Upon being so informed, he promptly complied wih the Examiner’s ruling, vie., October 31, 1900, by canceling the engine claims. It is to be observed that this action by Nice was less than two years from the date of the Office action of April 25, 1899; so that, even if he be held to have been concluded by his election in accepting the action of that date, he nevertheless took such proper action as the case required within two years from the date of the last Office action thereon. In other words, he prosecuted his case in good faith by doing all that the *434law and the rules required up to October 30, 1900, and, in view of the Office actions, it was on that date only that he was finally concluded by his election from reinserting claims to the engine. Duryea and White are therefore wholly in error,, as well as obscure, in their statement that ‘since December 30,. 1898, John V. Nice has had no right to include in his original or renewed application any claim to the engine structure/ since on December 30, 1898, the original application was no-longer in being, having been superseded by the renewal, and as to the latter no final election took effect until October 30,. 1900.
“Although Nice’s action of October 30, 1900, canceled the claims to the igniter, certain formal defects remained uncured,, and, being noted in the Office letters of October 31, 1902, and May 13, 1903, were disposed of by amendments April 30, and May 18, 1903, putting the ease in condition for allowance, and it matured into the patent No. 749,324, above referred to.”
There is nothing in the foregoing recital tending to show an abandonment of the claim of invention of the engine of the issue, disclosed in Nice’s original application.
When the claims therefor were rejected, for the reasons-given, he had his election to insist thereon and appeal from a second rejection, or to accept the action of the Patent Office, take his patent for the igniter, and then file another application for a patent for the invention of the engine. Electing to pursue the latter course, he filed the new application, which is substantially a division of the former application, on which the interference was declared with Duryea and White, and while that original application was still depending in the Office awaiting final action. There is no express limitation in respect of the time within which a divisional application shall be filed, in order to relate to, and constitute a continuation of, the original application. The rule that seems to prevail in the Patent Office is that, to maintain-this continuity, it must be filed while the original is depending in the Office. When filed within that time, it has been repeatedly held by different Commissioners of Patents, that the second application stands in lieu of the first to *435the extent of the matter subtracted from the other. Forbes v. Thompson, 51 Off. Gaz. 297, and cases cited, C. D. 1890, pp. 61, 63; 53 Off. Gaz. 2042, C. D. 1890, pp. 185, 186; Bundy v. Rumbarger, 92 Off. Gaz. 2002, C. D. 1900, pp. 143, 145; Hopfelt v. Read, 106 Off. Gaz. 767, C. D. 1903, pp. 319, 321. In the decision last cited, Mr. Commissioner Allen, after stating the rule that a complete application warranting the issue of a patent, and unabandoned, is in law a constructive reduction to practice, said: “This is so when two applications are pending contemporaneously and the first is not abandoned, whether the claims are presented in the original application itself, or in a later application filed as a division or a continuation of the original application, as in the second case the later application dates back to the earlier one. It is only necessary that the description in both applications shall be sufficient to support the claims. The fact that the Office practice may prohibit the prosecution and allowance of the claims in an earlier application does not prevent the applicant from availing himself of the earlier date of filing as his date of constructive reduction to practice, when he files a later application containing the same description and the claims based upon the same.”
This court has heretofore held that where an application had been forfeited for failure to pay the fee on allowance of the claims, and the applicant had filed a new application within the prescribed period permitted in such cases, he was entitled to the benefit of his original application as a constructive reduction to practice of the invention set forth therein and after-wards embodied in the second ^application. Cain v. Park, 14 App. D. C. 42, 46.
For a stronger reason, we think that a divisional application filed while the original application is depending in the Office must be held a continuation of the latter, and therefore to relate back to its filing date.
The situation is not governed by sec. 4894, U. S. Eev. Stat. U. S. Comp. Stat. 1901, p. 3384, as contended on behalf of the appellants. That section requires that all applications for patents shall be completed within two years after filing, “and in *436default thereof, or upon failure of the applicant to prosecute the same within two years after any action therein, of which notice shall have been given to the applicant, they shall be regarded as abandoned by the parties thereto, unless it be shown to the satisfaction of the Commissioner of Patents that such delay was unavoidable.”
The section has been held to apply to a case where more than two years had been permitted to elapse between the final rejection of the application and the date of filing a bill in equity to compel issue under sec. 4915, U. S. Rev. Stat. U. S. Comp. Stat. 1901, p. 3392; Gandy v. Marble, 122 U. S. 432, 440, 30 L. ed. 1223, 1224, 1 Sup. Ct. Rep. 1290.
let it be granted that the section applies, likewise, in a case where the divisional application shall have been filed after the lapse of two years from the time of final action in the Office upon the original; still, the facts of this case do not warrant its application. Two years did not elapse after such final action on the original application before the divisional application was filed. Until all the objections to the final application had been met and overcome, and the same had been finally allowed for patent, Pice was not put finally upon his election to accept the action necessitating the division of his application. When the time arrived for him to take final action, he filed the divisional application with the required diligence, and thereby preserved the continuity of the first for his protection as the inventor of the engine of the issue.
We are of the opinion that the decision appealed from was right, and it will be affirmed. It is so ordered, and the clerk will certify this decision to the Commissioner of Patents as the statute provides. Affirmed.