In N.L.R.B. v. Indiana Michigan Electric Co., 318 U.S. 9, at page 28, 63 S.Ct. 394, at page 405, 87 L.Ed. 579, the Supreme Court stated the general fundamental principles with respect to findings of fact by the Board, saying that the reviewing court is given discretion to see that before a party's rights are foreclosed his case has been fairly heard, and "Findings cannot be said to have been fairly reached unless material evidence which might impeach, as well as that which will support, its findings, is heard and weighed."