be so stiffened that the unsupported length shall never exceed twelve (12) times the width of flange.

Rigid diagonal bracing of angles is invariably to be used between the top flanges of stringers, and rigid bracing-frames are to be employed near all expansion points. If the panel length exceed thirty (30) feet, there shall be a bracing-frame at mid-length between the contiguous stringers of each track; but for all shorter panels the rigid lower lateral diagonals which are riveted to the bottom flanges will stiffen the latter sufficiently.

In respect to stiffening angles for stringers, the rules governing those for plate-girder spans are to be followed; but the end stiffeners are to be faced or otherwise treated so as to make the stringers of exact length throughout, and so as to effect a uniform bearing of the end stiffeners against the webs of the cross-girders.

In respect to proportioning of flanges and number of rivets required, the rules given for plate-girder spans are to apply also to stringers. The said rules are to apply also to cross-girders, as shall also those relating to stiffeners, splices, coverplates, and size of compression-flanges, that are given for plate-girder spans. Wherever it is necessary to notch out the corners of the cross-girders to clear the chords, the greatest care must be taken to provide an adequate means for transferring the shear to the posts without impairing either the strength or the rigidity. If necessary, in through-bridges the web of the cross-girder can be divided into three parts so as to let the end portions project above the top flange and form brackets that will afford opportunity for using an ample number of rivets to connect to the posts, and will strengthen properly the otherwise weakened cross-girder.

In order to carry the thrust of trains from the stringers to the posts through the lower lateral diagonals, the latter and the stringers are to be made to form complete horizontal trusses by running angles between stringers at the level of the bottom flanges. In single-track bridges two pieces of angles per panel running transversely between stringers at the intersection  of   the   latter   with   the  diagonals  will  suffice;  but  in