For information on Special Expeditions’ Columbia River cruises, call it at 800-762-0003. YachtShip CruiseLine also runs a boat through these waters (206-623-4245), and Clipper Cruise Line follows a similar route (800-325-0010). The Sea Lion is a small vessel (twenty-three times around the deck equals one mile), offering correspondingly snug but comfortable cabins and pleasant dining. It is rich, however, in the things that matter most: in its questing staff of historians and naturalists and in its well-traveled passengers, who share surprising funds of knowledge with one another. Good background reading includes Stewart Holbrook’s 1956 volume The Columbia ; Dayton Duncan’s Out West (1988), in which the author follows Lewis and Clark’s route; and, of course, the published journals of the two great adventurers.