Saturday's trip leaves Baltimore's Camden Station at 8:30; Laurel at 9 and Silver Spring at 10, and arrive in Harpers Ferry at 12:45. It leaves Harpers Ferry at 4:15, stopping in Silver Spring at 6 and Laurel at 7 and arriving in Baltimore at 7:30.

Sunday's run is via the Patapsco Valley. Instead of getting off at Harpers Ferry, passengers may continue to Martinsburg, where the engine will be turned around, coaled and watered. Fares for each excursion are $23 for adults, $20 for children five to 12. Parlor-cars seats cost $35 and the observation-lounge seats cost $50.

Friday, May 12, the train will go from Baltimore to Cumberland, for a series of trips in the Cumberland area. Passengers who don't want to go all the way to Cumberland may take the train between intermediate points. Laurel to Silver Spring, for example, cost $3 for adults and $2 for kids.

From Cumberland, the Chessie steam special will go west for a tour of duty, returning to the Baltimore and Richmond areas for more excursions in September and October. For further information, call 301/237-3737 or, after 6, 301/485-1555.

Southern Railways will run steam excursions to Charlottesville July 22-23 and 29-30, leaving from Alexandria and Manassas. For details write to: Piedmont Limited/610, P.O. Box 456, Laurel, Md. 20810.