There's a coming-out party for John Bull this Tuesday from 11 to 4 along the C&O. The old geezer's getting an airing from the National Museum of American History. It was 150 years ago on September 15 that the John Bull, the world's oldest operable steam locomotive, made its first trial run. To celebrate this, old John will steam back and forth on the track between Key Bridge and Chain Bridge, a band will play and balladeers will sing railroad songs. To add a 19th-century tone to the occasion, there will be banjo players, high-wheel cyclists, horse- drawn vehicles, old-fashioned games and an operating telegraph station, near Fletcher's Boat House. Museum staff members get to ride the train in period costume, but the rest of us -- train buffs and photo buffs alike -- must be content to take pictures of it. The Smithsonian suggests the following places for photo opportunities: FLETCHER'S BOAT HOUSE, where the locomotive will begin its trips. ACROSS THE CANAL FROM FLETCHER'S at the Abner Cloud House. 90 YARDS WEST OF FLETCHER'S, at a wooden platform marked No. 19. This for photos of a locomotive passing through a wooded area. NEAR A SMALL STONE BRIDGE 100 feet west of Fletcher's. Stand 20 feet from the bridge and look back to take pictures of the locomotive passing over it. AT JACK'S BOAT HOUSE in Georgetown under the Whitehurst Freeway. Here you can see the locomotive passing under a massive stone bridge. THE SIDEWALK AREA along Key Bridge. Good for just watching. After its first trial run, the John Bull operated on the Camden and Amboy Railroad in New Jersey for 35 years as a middle link connecting Philadelphia and New York. In 1876 it was displayed at the Centennial Exposition in Philadelphia, and nine years later was donated to the Smithsonian, where it will return after its outing.