“The application in this case is for a mandamus directed to the District Judge of the Northern District of this state, requiring him to vacate a rule which had been granted, allowing certain amendments of the record in this cause, and also to vacate and annul such amendments. If it was proper to enter into an examination of the regularity of such amendments, or the authority of the District Court, to allow them under the circumstances disclosed in the affidavits, the propriety of the amendments would at least be very questionable.”