Statement of the case. forming the subject-matter of this invention relating to the following particulars: First, the posts, instead of being made of two rolled plates of iron of semi-polygonal transverse section united by rivets passed through the center of the polygon and sprung apart by distance-plates, are made of two or more plates of wrought-iron with flanges at the edge, the plates being so united as to make hollow posts by rivets passed through the flanges, and each plate being arched longitudinally by means of ferrules placed at intervals between the flanges and around the rivets, and instead of casting the bases and capitals onto the ends of the posts we use bases and capitals connected by rivets to the post; second, instead of making the upper chords of hollow castiron sections or short tubes, we construct our upper chords of a combination of wrought-iron I-shaped beams or channel-bars, or both, connected by wrought-iron plates, so as to form cellular chords of great strength and capacity of resisting either transverse strain or longitudinal compression; third, the use of bottom chords of thin wrought-iron plates, the eye of which, at each end, instead of being cut out of a rolled plate and drilled or forged into shape, is upset under strong compression, so as to give at the eye of the bar a degree of strength equal or superior to that of the bar at any point between the eyes. To enable others skilled in the art to construct and use our improvements, we will proceed to describe them more particularly. In our bridge the upright posts AA are placed at regular intervals at each span, and opposite to each other on each side, so that the transverse struts G may be placed across and at right angles to the roadway, between the upper chords immediately above the capitals of the opposite posts, and transverse struts H similarly placed between the bases of the opposite posts, the ends of the struts G and H being attached to the connecting-pins M and N, which pass through the upper chords immediately above the capitals and through the bases of the posts respectively, as shown in Fig. 2. |