This appeal is from the decision of the Commissioner of Patents, awarding priority of invention to appellee, Holslag, for an apparatus and method of arc welding with alternating current. The case turns entirely upon questions of fact. The record consists of about 1,850 printed pages. The three tribunals of the Patent Office, in most elaborate opinions, have concurred in awarding priority to Holslag. After a careful examination of the evidence, and review of the analysis thereof in the opinions of the tribunals below, we are convinced that a proper conclusion has been reached. The decision of the Commissioner of Patents is therefore affirmed.