delivered-the opinion of the Court:

Assuming that the officers -and tribunals of the Patent Office were correct in holding that the appellee, Appert, was limited to the date of January 12, 1894, as the date of the communication of his invention to the public — a point, however, upon which we do not deem it necessary here to pass — it is very plain that if the appellant were limited to the date of January 20, 1894, stated in his original preliminary statement as that of his communication of his alleged invention to others, Appert would beyond question be entitled to judgment of priority of invention. It is only by the reformation of his preliminary statement, after the discovery of his adversary’s position, and the reference backward to the month of December of 1893 of his communication of his invention to others, that the appellant seeks to overcome the otherwise manifest priority of the appellee. Whether, in the face of the suspicion of tergiversation fairly engendered by the inconsistency of his two statements and the peculiar explanation which he has given of his now assumed mistake in the original preliminary statement, he has satisfactorily substantiated by proof the allegation of his amended statement, that he first made sketches of his alleged invention and explained the same to others on or about December 20, 1893, is the question upon the determination of which the controversy before us depends. The question is purely one of fact, and under the decision in the case of Hisey v. Peters, 6 App. D. C. 78 : 71 O. G. 892, we might very well decline to disturb the conclusions reached by the board of examiners and the Commissioner of Patents.

In that case we said: “ Upon the case coming into this court on appeal, after, the question of fact has been examined and ruled upon as in this case, what is the rational presumption to be indulged as to the conclusion of fact ? *276We think it is established beyond controversy that, in a case so presented, the decision of the Patent Office must stand unless the evidence shows beyond any reasonable doubt that the appellant was the first inventor.” But, as we also said in that case, so we may say in this: “Irrespective of this onus cast upon the appellant of showing clearly the existence of error in the conclusions arrived at by the officials in the Patent Office as to the facts of the case, we have no difficulty in arriving at the same conclusion on the question of priority of invention, upon the evidence in this record.”

We think that, upon the- record as made in this case, the appellant more correctly stated his dates in the original than in the amended preliminary statement. Undoubtedly cases not infrequently occur wherein it is proper to amend a preliminary statement, even in the vitally important matter of the date of the conception and communication of an invention ; and to further the ends of justice amendment will always be allowed in proper cases. Yet it is always a suspicions circumstance in a case of interference that, after the claim of one of the parties has been fully disclosed and fixed as of a specified date, the other should then seek by amendment of his preliminary statement to show, a date of invention different from that in the original statement and prior to it and to the date of his opponent. Amendment upon so important a point should not be allowed in such a case unless it is .'shown that the interests of justice plainly demand it; for upon the determination of these dates it depends, in the majority of cases, which party is entitled to the patent, and a change of memory is comparatively easy when self-interest dictates a different date. The Commissioner of Patents, in his opinion in this case, plainly intimates that the office was to some extent imposed upon in the allowance of the amendment in this instance; and he seems to have had good reason for His animadversion on the matter. The amendment was not made, or sought to be made, nor was there anything whatever to indicate the *277propriety or expediency of its being made, until the appellee’s case had been fully disclosed and the date of his invention, arbitrarily fixed as of the date of the issue of his French patent, had been irrevocably determined. Then, and not till then, did the appellant deem it expedient to amend. He shows no good reason for his delay.

The appellant’s preliminary statement, as originally made, had set forth an alleged disclosure of the invention in controversy and the making of a sketch by him to illustrate the same on January 20, 1894 ; and the sketch there referred to, which bore the date specified and which appears on its face to have been of an exceedingly crude character, was produced in evidence, and a copy of it is found in the record before us. But when it became apparent that an earlier date than January 20, 1894, would be required in order to overcome Appert’s patent of January 12, 1894, six other sketches were discovered and produced, and the preliminary statement was amended. The story of these six sketches, as told by the appellant in his testimony, following therein his amended preliminary statement, is that they were made by him on December 20, 1893 ; that he knows they were made on that day because they bear date on that day; that it has been his custom for several years, in common with the majority of Patent Office draftsmen, to date all sketches on the day on which they were made ; that three of the six sketches (numbered in the record as 1, 2, and 3) were used to illustrate an application executed on January 10, 1894, and filed in the Patent Office on January 18, 1894, for a patent of a process for the manufacture of glass different from the process in controversy here ; that sketches numbered 4, 5 and 6, of which No. 4 is claimed to illustrate the process now in issue in tliese proceedings, were put aside to be submitted to some person familiar with the practical manufacture of v'ire-glass, which the appellant, who is merely a draftsman, does not claim to be ; that accordingly they were pinned together in such manner as that sketch No. 1 would appear first to anyone taking up the papers *278and the other sketches would be covered by that one ; and that they were then put away with the files of the papers relative to the application for patent made on January 18, 1894, whence they were exhumed on February 22, 1895, to be used for the amended preliminary statement of February 28, 1895.

The appellant further testified that he had different places or different files in his office for pending applications and for allowed cases ; that the application of January 18, 1894, had been allowed by the Patent Office on May 3,1894, but had been temporarily withdrawn from issue for a purpose, and the papers relative to it were in one file in .his office ; and that the papers relative to the pending application, that of April 25, 1894, upon which arose the present proceedings in interference, were in another and different file. Some action had been had by the Patent Office in this latter case also on May 3, 1894, when the former application was allowed; and there was occasion at that time to handle the papers in both cases. Again on September 28, 1894, and again on October 4, 1894, there was occasion' to take out and handle the papers in the allowed application ; and yet it is claimed that the sketches Nos. 4, 5 and 6, among those papers, were not discovered until February 22, 1895. It was also testified by the appellant that probably on or about March of 1S94 he submitted to a manufacturer of glass some sketches practically identical with sketches Nos. 4, 5 and 6, and made in his presence, but not those sketches themselves. But it does not appear what the manufacturer thought of them, nor were these reproduced sketches produced in evidence, nor was the manufacturer called as a witness to corroborate the statement. And he further testified that, “ during all that period of time from December of 1893 to the date on which the interfering application was filed, the process was borne in mind and very many different sketches of different forms of apparatus for carrying such process into effect were made.”

It is also a singular fact in the case that, while the appel*279lant, apparently with the sketches before him, testified that he knew that the six sketches in question were made on December 20, 1893, because they bore date on that day, and it wras his custom to date his sketches, yet the record shows sketch No. 1 to be without any date ; sketch No. 2 alone to bear the date of December 20, 1893, and the other four sketches to bear the date of December 25, 1893 ; and there is in the record no explanation of the discrepancy.

These are the salient points of the appellant’s testimony. The testimony of his two associates in corroboration of it is too vague and insufficient to justify much consideration of it.

The inherent improbabilities and inconsistencies of this story are palpable. It is not reasonable to suppose that the appellant, expert draftsman as he apparently was, would pin together and put away in one file sketches appertaining to radically distinct and different matters. It is not reasonable to suppose that he would have forgotten them at the time at which they were most needed, when the present application was filed on April 25, 1894, within the month following the time when he reproduced them to the manufacturer of glass whom he consulted, as he claims, and again when the original preliminary statement was filed on July 27, 1894. It is not reasonable to suppose that he did not see them or that he ‘would not necessarily have been reminded of them on May 3 or 4, or September-28, or October 4, 1894, on all which occasions he handled the papers in which they were contained. If there was here the element or the indication of a valuable invention, valuable enough to induce him to make application for a patent for it in April of 1894, and important enough to induce him to consult a practical manufacturer about it in March of that year, as he pretends, and to reproduce the sketches for the benefit and information of that manufacturer, it is simply incredible that he should wholly have forgotten his original sketches, claimed to have been made, by him on December 20, 1893, and to have forgotten them during all the subsequent *280months until February 22, 1895, when he'admits that on three several occasions, at least, he had the sketches actually in his hand, and must necessarily have been reminded of what they were, even if he did not actually see them. If these sketches were actually made in December of 1893, as it is now claimed they were, the conclusion is inevitable either that they refer solely to the apparatus or process for which a patent was sought under the application of January 18, 1894, or else that they amounted to nothing more than mere fancy sketches, which have never been reduced to practice, either actual or constructive, and were, in fact, abandoned almost as soon as made.

There is, perhaps, one other alternative, and that is, that they may have been made in December of 1894, under the stringency of the appellant’s need to counteract in some way the otherwise conclusive- case of the appellee against him ; but this alternative need not be considered.

We are entirely satisfied from -the testimony that the appellant has failed to show any date for his alleged invention earlier than January 20, 1894; that his proof is wholly insufficient to show any discovery or communication by him of the issue of invention herein December of 1893, or atany other time prior to January 20, 1894; that his amended preliminary statement was without foundation in fact; that his original preliminary statement more correctly stated his claim, and that he has failed to overcome the appellee’s case as made by French patent issued to the latter on Janu-uary 12, 1894.

The decision of the Commissioner of Patents in this case will, therefore, be affirmed, and priority of invention will be awarded to the appellee, Leon Appert. A certificate of the proceedings and decision of the case in this court will be returned to the Commissioner of Patents to be entered of record in the Patent Office, as directed by the statute. And it is so ordered.