hello everyone tonight
Well DL I do not feel comfortable working modern thought into this conversation, we all know that cables only work under tension, and were slowly adapted as the technology improved in certain instances
The early wooden bridges used wooden trusses, and cross members of wood as bracing, wrought iron rods were used as needed for additional strength, I don't really remember cables being used during that period
The 18"sills would have needed quite large trees to have remained 18" square or rectangular at 40 feet or longer, I know from experience that to square 12" at 36 feet takes quite a tree indeed,--I am guessing 4.5 to 5 feet on the butt ends or larger for those 18" timbers--just to move them around would have been a chore, unless they hewed them where they fell
NH