New Idria Quicksilver Mining Co. Nos. 10589-592, in circuit court of appeals for 9th circuit, New Idria Quicksilver Mining Company v. commissioner of internal revenue; Klau Mine, Inc., v. [same]; Oat Hill Mine, Inc., v. [same]; Wild Horse Quicksilver Mining Co. v. [same], on petitions for review of decisions of Tax Court; brief for respondent.