Note the flags and marker lamps on the 2519. The flags are dirty, but don't appear to be white which would denote an "extra" train (not shown in the timetable). They are likely green, indicating that another section of this train will be following. The lack of flags or markers on the 2637 suggest that it will not be leaving the yard, and is in fact engaged in switching duties, as noted by Steamin.

If you've never been in the presence of mighty locomotives such as these, you don't realize how massive they are. I went to see the Norfolk & Western 1218 arrive in Salisbury, North Carolina in 1989. I stood at the edge of the ballast of the track along with many other people and had to look almost straight up to see how tall she was. I've ridden behind the 1218 and the Southern 4501 in passenger cars with the windows down and boy did my face get dirty. Good times.

Engine 2519, on left, listed as a road engine, wheel arrangement 2-8-2, C&NW J-A class, builder: Schenectady Locomotive works.

Engine 2637, on right, listed as switching type, wheel arrangement 0-8-0, C&NW M-4 class, number two in the (2636 was first). builder: Richmond Locomotive works. Maybe it was pressed into road service at this time. In addition to the wheel arrangement, this engine gives a clue to its switching role as you see the footboard on the front bumper of the engine, (instead of the 'cowcatcher' seen on #2519) where a switchman would stand as the engine moved around the yard and assembled the train cars from the yard into a train for a road engine to haul away.