Suspenders or hip verticals and two or more panel lengths of bottom chord at each end of each span shall, preferably, be made rigid members, excepting that in "A" trusses the bottom chords and centre verticals are to be of eye-bars.

All floor-beams are to be riveted to the truss-posts in truss-spans, excepting in the case of Petit trusses when the suspenders are of eye-bars. In these, floor-beam hangers may be used, provided they be made of plates or shapes, and that they be stayed at their upper ends against all possibility of rotation.

CONTINUOUS SPANS.

Except in the case of swing-bridges or cantilevers, consecutive spans are not to be made continuous over the points of support.

TRESTLE TOWERS.

As a general rule, each trestle-bent shall be composed of two columns battered from one and a half (1 1/2) to two and a half (2 1/2) inches to the foot, the bents being united in pairs to form towers. Each tower thus formed shall be thoroughly braced with rigid bracing on all four faces, and shall have four horizontal struts at the base. In each intermediate horizontal plane of division, formed by the panels of the tower bracing, there is to be a pair of diagonal adjustable rods to bring the columns into proper position and to retain them there.

The feet of the columns must be attached to anchorages capable of resisting twice the greatest possible uplifting; and the details of the metal-work connecting the anchor-rods to the columns must be such as to make the metal-work and pedestals act as a single piece, so that, if tested to destruction by overturning, the bent would not fail between the superstructure and the substructure.

While it is desirable to have sufficient base to prevent any tension from coming on the anchor-bolts, it is not advisable on this account to make the batter of the columns too great, especially in very high trestles.