It is interesting to contrast the differences between C&S and D&RGW/RGS trestle construction.
The D&RG/RGS used 6 stringers per span, the C&S evidently 8 stringers (but smaller?).
The D&RG/RGS used 8"x8" bridge ties spaced 4" apart. The C&S appears to use 8x8 ties spaced further apart, likely 8 inches.
The D&RG/RGS bolted the outside guard timbers to every 5th or 6th tie. The C&S evidently bolted the timbers to every tie, with bolts offset every other tie.
Great detail photos for bridge building!
Jim Courtney
Poulsbo, WA