3,000 feet. Attention is called to the fact that the costs found per foot of main span are not total for the structures; because the items of costs of deck and floor-system, being the same for both types, have been omitted for the sake of simplicity. The lateral system, though, has been taken

magnify image

into account, because the weights of metal thereof in the two types of structure differ materially. The principal reason for this is that, in the eye-bar type, special wind chords will be obligatory; whilst, in the wire-cable type, the chords of the stiffening trusses serve as wind chords, only a small increase in sections above those needed for live loads being required.