delivered the opinion of the Court:

This is an interference case involving priority of invention of a mechanism for stopping a hydraulic plunger elevator at the upper and lower limits of its run independently of the operator.

The following is the issue declared:

“1. In combination with an elevator car and a stop mechanism therefor, of a rope connected to run with the elevator car, and stationary means for causing a deflection of said rope t) actuate said stop mechanism.

“2. In combination with an elevator car and a stop mechanism therefore, of a rope connected to run with the elevator car, and stationary means unattached to the rope for causing a gradual deflection of said rope to gradually actuate said stop mechanism.

“3. In combination with an elevator car and a stop mechanism therefor, of means for actuating said stop mechanism, a pair of running ropes for actuating said means, and means for causing a deflection of one or the other of said ropes as the car approaches the end of its run.

“4. In combination with an elevator car and a stop mechanism therefor, of means for actuating said stop mechanism, a pair of ropes connected to run with the elevator car for actuating said means, and means for causing a deflection of one or the other of said ropes as the car approaches the end of its run.

“5. In combination with an elevator car and a stop mechanism therefor, a pair of ropes connected to travel with the car, and means for causing a deflection of each of said ropes to actuate said stop mechanism.”

*206Thure Larsson first filed an application on March 7, 1903, which became abandoned through oversight of his solicitor. H& filed the application in interference on July 5, 1904. The drawings and specifications and all of the claims but one were-copies of the former application. The change in the single-claim was to avoid an objection that had been raised by the Examiner, Karl E. Ossian. Jansson’s application was filed April 19,1904, and patent issued to him December 13,1904. Through inadvertance in the Patent Office the patent issued without regard to Larsson’s application then pending. This interference was brought about by Larsson, who, for that purpose, inserted certain claims of the patent. The patent, having been issued under these circumstances, does not add to the burden of proof of the junior applicant.

The three tribunals of the Patent Office concurred in awarding priority to Larsson upon the testimony.

A preliminary question arose over the contention of Jansson that Larsson was estopped to embody the claims of the former’s patent, under the principle enounced in Bechmam, v. Wood, 15 App. D. O. 484. We agree with the Commissioner that the facts do not bring the case within the principle, but are analogous to-those in eases decided since Bechman v. Wood. McBerty v. Cook, 16 App. D. C. 133, 138; Luger v. Browning, 21 App. D. C. 201, 206; Furman v. Dean, 24 App. D. C. 277, 281; Seeberger v. Dodge, 24 App. D. C. 476, 483.

Another question earnestly pressed on the argument relates to the refusal of Larsson, upon the advice of counsel, to answer certain questions propounded on cross-examination. It is true, these questions related to whether other instalments of elevators had been made than those in Pittsburgh and Alleghany buildings, which Larsson relied on for reduction to practice. It is to be remembered that Larsson was a party to the proceedings; wherefore wider range of cross-examination was allowable. We think that the general question should have been answered. Then, if followed up by further questions clearly showing an intention to elicit information relating to the business of Lars-son and his assignee, not relevant to the questions at issue, the *207witness might well refuse to answer under the advice of counsel. As counsel for the appellant did not undertake to point out the relevancy of these questions by stating what he expected to elicit, and the case was otherwise so plainly made out, we do not think there was error in refusing to suppress or exclude the deposition.

The questions of the dates of conception of the invention by the respective parties, and its actual reduction to practice by Larson, were of fact exclusively. The tribunals of the Patent Office were unanimous in the conclusion, from the evidence, that Larsson conceived the invention as early as February 19, 1903, and reduced it to actual practice as early as November 14, 1903, by introducing it into elevators in several buildings. It is unnecessary to add anything to their satisfactory review of the evidence supporting that finding. We find nothing in it to justify a different conclusion. They also agreed in finding that Jansson conceived the invention as early as January 28, 1903. We agree with them, also, that Jansson lost the benefit of his earlier conception through want of diligence in seeking to perfect his invention. He did practically nothing during the fourteen months that elapsed between his conception and the filing of his application. Meanwhile Larsson had conceived the invention and followed it diligently to actual reduction to practice in a satisfactory manner, more than four months befoi’e Jansson showed any activity.

The decision is right, and will be affirmed; and this decision will be certified to the Commissioner of Patents. It is so ordered.

Affirmed.