904 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



there being ip disconnected pieces, as their manner of construc- 

 tion allows. The chains are secured to its ends by passing through 

 a cast-steel saddle (against which the chords abut) where they are 

 pinned, the centre of the pins being in the axis of the chords. 

 The chains and chords are sepaT-ated and kept in position by 

 means of verticals acting either by thrust or tension, and diago- 

 nals break the panels thus formed into triangles. These verticals 



are formed of plates of steel and angle irons of I 1 section, 



connected by a lattice weighing — the whole properly rivetted 

 together. The sectional area of each street is eight square inches, 

 and they are so proportioned as not to be greater than eighteen 

 diameters in length. The diagonals are rods one and a quarter 

 inches in diameter, grasping the chain pins at one end, and at the 

 other secured between the lips of the horizontal members. Their 

 tension is adjusted b}^ means of turn-buckles. In this consists the 

 vertical stiffening, and the arrangement for keeping innumerable 

 points. The lateral sway bracing is simihirly heated ; the tresses 

 being separated from each other by means of light open work 

 webbed steel streets and rods, the rods at their intersection meet- 

 ing in a ring where they are screwed to their bearing and thus 

 adjusted. The support for the roadway is now completed, and 

 you have the whole sustaining power before you. The roadway 

 itself is swung from the chains by means of streets, which, in con- 

 nection v.-ith the diagonals, form the stiffening element required to 

 absorb undulations, or in fact keep them out. The Wiliiamsport 

 suspension l)ridge consists of no more than this ; the suspenders 

 being posts (hung upon the ware cables) every twenty feet, the 

 panels thus formed being tied diagonally with inch rods (Franklin 

 Institute Journal, May 1866). This is the third suspension bridge 

 erected with suspender streets. Mr. Murphy, C. E., having the 

 credit of introducing the modification, which experience shows pos- 

 sesses a remarkable degree of stiffness. These suspension streets 

 are similarly constructed as those of the trussed chains only lighter, 

 the phitcs being but | inches thick, and the angle irons 3x|. 

 I speak of suspension struts, a seeming incongruity, but they act 

 positively with reference to the load, and negatively with reference 

 to the absorption of vibrations. Two continuous steel plate I-beams 

 clasp the bottom of the suspenders, represented by the lower 

 horizontal line in the diagram. These beams are 16 inches deep, 

 their bearing points being, of course, at ever}' panel 14' 09' apart. 

 Diagonal truss rods, with turn buckles for adjustment, break up 



