BRID&ES 



491 



feet on each Jiier, On the top or circumference of 

 these sections and wing arches, beams or ties and 

 diagonal braces, are laid and let into each other, in 

 the form of lattice work, and the whole firmly con- 

 nected with the arches, by iron bolts with screws, 

 going through them at the distance of every eight 

 feet.... thus they are made to form one entire con- 

 nected arch, which can neither admit of any side- 

 way or intestine motion between the sections, nor be 

 readily injured or endangered by high winds. 



The platform on which the travelling is performed, 

 is suspended from these arches, by means of iron 

 chains or links, which hook into the eye bolts, firmly 

 fixed through the arches, at the distance also of 

 every eight feet, in the three middle sections, and 16 

 feet in the two exterior ones. To the lower ends of 

 these chains is appended a stirrup^ in which the 

 beams lay, which sustain the joists and flooring. To 

 prevent the platform from having any swinging mo- 

 tion, wing chords and diagonal braces are again in- 

 terposed, which effectually perform this service. 



The expansion of the arches (were not the solidity 

 and weight of the piers and abutments of themselves 

 sufficient) is completely guarded against by the intei'- 

 vention of wooden chords which embrace and connect 

 the several feet of these arches together. These 

 serve also a further important purpose, to wit... .of 

 stiffening and strengthening the arches, by means of 

 upright bracing, which takes place between them and 

 the chords ; so that by the application of great weights, 

 to either end of the arch, no vibratory motion can 

 ensue, as the pressure is by this means distributod 

 throughout the whole extent of the segment. 



