With the summer winding down, the public library is resuming its Saturday hours. As of Sept. 8, the library is open on Saturdays from 9 a.m. to 5 p.m. through the end of next May, according to library director Diane Giarrusso. Meanwhile, this Tuesday the library is presenting a talk by Roger Tetreault of Boxborough recounting his experience hiking the entire Appalachian Trail. The event, from 7 to 9 p.m., is free and open to all with preregistration requested. It is the second of two talks at the library on hiking adventures, both sponsored by the Friends of the Tewksbury Public Library.