Guest speaker Sal Manna will present a slide program about famed naturalist Alfred Russel Wallace at the inaugural Discovery Day at Calaveras Big Trees State Park on Saturday, July 20. The presentation, based on the historian’s book “Glorious Trees: Alfred Russel Wallace in California,” will focus on his 1887 visit to the Big Trees as well as his reunion with brother John Wallace, after whom the town of Wallace was named. The program will take place at 11:30, 12:30 and 1:30. Also featured during the new all-day event, which requires only regular admission to the park in Arnold, will be a gold miner’s camp recreated by Columbia State Park and docents stationed throughout the visitors’ area offering stories about the park’s history. For more information, visit bigtrees.org.