Injured when a hydraulic drill malfunctioned with a boom and sprayed hot oil into his face and eyes, Danny R. Ruark relied on res ipsa loquitur to prove negligence in a tort case against his employer, Union Pacific Railroad, under the Federal Employers’ Liability Act. The crucial question of law for the 7th U.S. Circuit Court of Appeals was whether Ruark — a track worker who was using the device to drill holes in …