Dava Sobel’s nonfiction book “Longitude” — 18th-century clockmaker John Harrison’s obsession with building the chronometer — is under discussion at 3 p.m. Saturday, Aug. 10, at the Sequim Library, 630 N. Sequim Ave. Copies are available at the Sequim Library and on audio CD and download. Call 683-1163 or e-mail Sequim@nols.org.