WILKES-BARRE —If time travel were possible, history teacher Clark Switzer would like to visit just about every era he’s researched. “Not that I’d want to live there, but to visit would be a great idea,” he said. “I’m just thinking about Judge Jesse Fell’s tavern and sitting around as people came in off the stagecoach and you could listen to their stories about life on the road.” If you could manage a February 1808 visit to Fell’s tavern, which once stood at the corner of South Washington and East Northampton streets in Wilkes-Barre, you might even feel the heat as Fell burned anthracite for the first time in an open grate. But not every scene from the past is so cozy. During the past several years that Switzer worked on the documentary “Scratching the Surface: 300 Years of Wyoming Valley History 1675-1975,” he came across images that speak to the hardships of men, women and children whose lives revolved around the coal industry. “Obviously the men had a dangerous job working in the mines, but the women had another story, which I think is largely untold.