In the crowded southern Illinois coal fields, the Old Ben Coal Corp.'s No. 8 mine had a good record of safety. State mine inspectors had checked and okayed it on May 29. The night of July 23 1947, the large, 37-year-old mine had as usual been rock-dusted to localize possible gas explosions. But the next afternoon, while a full shift of 264 miners worked underground, a crushing blast shook one of No. 8's 500-ft.-deep galleries. Near the source of the explosion, 27 miners died, five were injured. The cause: "Ignition of methane gas."