delivered the opinion of the Court:

The tribimals of the Patent Office agreed that Collins Avas at least entitled to June 13, 1911, as his date of conception, and that he exercised due diligence in reducing to practice. The contention of Cheatham, who has appealed, is that the structure conceived by Collins prior to July 29, 1911, was inoperativo and that he should be limited to that date for his conception. There Avas no motion to dissolve on the ground of inoperativeness, and each tribunal of the Patent Office to AA’hioh it Avas presented as an incidental question has decided in favor of Collins. The question of inoperativeness must be regarded as settled. Duryea v. Rice, 28 App. D. C. 423, 431.

It is apparent from the evidence that the drawings of Collins Avere embodied in a construction that was tested irpon cars in Brooklyn on July 24 and 25, 1911. While the test was sufficient to demonstrate the efficiency and utility of the invention, there Avere some minor mechanical defects which Avere afterwards cured. The device reasonably met the requirements of the specifications, and the changes aftenvards were such as ¡my skilled mechanic Avould have made to remove the minor defects in operation. Burson v. Vogel, 29 App. D. C. 388, 394; Pool v. Dunn, 34 App. D. C. 132, 137.

The evidence on behalf of Collins is carefully and fairly reviewed in the decisions of the Patent Office tribunals, who concluded that he had conceiA-ed the invention at least as early *20as' June 13, 1911, and bad been diligent in reducing to practice before Obeatbam’s'application was filed.

We find no error, and being fully satisfied with tbeir conclusions, tbe decision is affirmed.

' Tbe clerk will certify tbis decision to tbe Commissioner of Patents as required by law. Affirmed.