“The Wagner Act provided: ‘The findings of the Board as to the facts, if supported by evidence, shall be conclusive.’ Act of July 5, 1935, § 10(e), 49 Stat. 449, 454, 29 U.S.C. § 160(e). This Court read ‘evidence’ to mean ‘substantial evidence,’ Washington, V. & M. Coach Co. v. Labor Board, 301 U.S. 142, and we said that ‘[s]ubstantial evidence is more than a mere scintilla. It means such evidence as a reasonable mind might accept as adequate to support a conclusion.’ Consolidated Edison Co. v. Labor Board, 305 U.S. 197, 229. Accordingly, it ‘must do more than create a mere suspicion of the existence of the fact to be established. [I]t must be enough to justify, if the trial were to a jury, a refusal to direct a verdict when the conclusion sought to be drawn from it is one of fact for the jury.’ Labor Board v. Columbian Enameling & Stamping Co., 306 U.S. 292, 300.” J. Frankfurter, Universal Camera Corp. v. National Labor Relations Board, 340 U.S. 474 (1951).