delivered the opinion of the Court:

The tribunals of the Patent Office held that appellate, Benjamin W. Givens, conceived the invention in March, 1909, but accorded him his filing date, October 11, 1910, as the date of reduction to practice. Appellee, Warren, was awarded the date of January 10, 1910, for conception, disclosure, and reduction to practice. These findings are amply supported by the evidence.

Warren built and fully tested a lubricator embodying the invention in January, 1910, by using it for two months on an elevator in Fairfax Hall, at Cambridge, Massachusetts, a dormitory for students in connection with Harvard College. This construction and test constituted a complete reduction of the invention to practice. Warren, however, did not file his application until January 4, 1912. In the meantime, on June 27, 1911, a patent was issued to Givens.

The evidence fully supports the finding of the Commissioner that Givens was lacking in diligence when Warren came into the field and reduced the invention to practice, and that Warren’s test in January, 1910, was so open and notorious that his failure to file for almost two years thereafter did not amount to concealment or abandonment of the invention within the rule announced in Mason v. Hepburn, 13 App. D. C. 86.

The decision of the Commissioner of Patents is affirmed, and the clerk is directed to certify these proceedings as by law required. Affirmed.