I see small platforms with steel barrels, placed at intervals along the far side. What purpose do the barrels serve?

[Fire extinguishers. - Dave]

I seem to have Ophir of heights.

How 'bout that for a clever title for my comment?

The outer rails are there to keep the trucks traveling relatively straight over a trestle, viaduct, or bridge during a derailment. A rough ride but better than the alternative.

The smaller section rails outside the running rails are intended to keep derailed cars from going completely off the trestle deck. Additionally, there are guard timbers at the ends of the ties as a last resort.

On a standard gauge railroad, the guard rails would be between the running rails, with the guard rails brought together at a point at the end. Not so good with tippy narrow gauge cars.

With modern welded rails, and very few bolted joints, the chance of a spontaneous derailment is greatly reduced, and the guard rails are now frequently omitted, especially if passenger trains do not use the line.

Also note the extended timbers on the near side, presumably to allow laying down planks to make maintenance work easier.

Is that standard gauge also on the trestle?

**********

Thanks to both Steamcrane and Wormy for the guard rail information. I knew of standard gauge guard rails, but not the narrow gauge type.

As always, Shorpy is informative as well as artistic and entertaining.