280 Mr Buchanan's Report on the Bridge of Suspension 
Main Chains. — One compound chain on each side of the bridge, consisting of 
36 single chains, running parallel to each other, and ranged in a compact 
square, 6 broad and 6 deep. Each single chain is 1 4 inch diameter ; each 
compound chain has thus a thickness or cross section of 63^ square inches, 
and both together 127 inches. The single chains are formed of bolts 15 
feet long, upset and shouldered at each end, and coupled together with 
cast iron coupling blocks 4 inches diameter ; the strength of each bolt and 
coupling being carefully proved to eight or ten tons on the square inch. 
Roadway — 30 feet wide ; 28 feet clear of chains and side rails ; and 20 feet clear 
of footpaths, each of which is 4 feet wide. Roadway laid with gravel or 
metal 4 or 6 inches deep ; this laid on cast iron-plates | inch thick ; these 
supported on malleable irony listing frames, crossing under the bridge at 
every 5 feet in its length, each 3| feet deep in the middle, and well trussed 
in every part : These frames united and strengthened by malleable iron 
plates, 2 feet deep, running longitudinally the whole length of the bridge 
standing upright, and by their depth giving stiffness to the roadway. 
Suspending Rods These are formed of fth inch bolts, and are placed two to- 
gether on each side of the bridge, and at every 5 feet in its length, attached 
to a socket in the suspending frames below, and to a coupling above, which 
is attached to the chains, and binds them all into one mass. Similar rods 
run horizontally from the chains to the pillars, and thence to the descend- 
ing chains : these serve to keep the arch of the chains steadily in its place, 
and, interweaving with the upright rods, they communicate a remarkable 
strength and steadiness to the whole structure. 
Pillars These are four in number, two at each end of the bridge; each consists 
of a pyramid, 4 feet square at top, 8 feet at bottom, and 50 feet high, rest- 
ing on a pedestal 1 1 feet square and 1 1 feet high, and the bottom of which 
is Jevel with the roadway of the bridge. This pedestal rests on a pier 
of stone, 12 feet square at top, and 20 feet square at bottom, built on the 
site of the present pier : the bottom is on a level with low water-mark, 
and founded on a strong basis of planking and piles. The pyramid is com- 
posed of iron-plates 4 inch thick, cast with flanches, and bolted and rusted 
together into one mass, the hollow within being built up with stone. The 
pedestal is either formed in the same manner, or wholly of stone. The 
base or pier below is built of ashler, and put together in the strongest 
manner. The pyramid is bolted to an iron plate or frame resting on the 
top of the pedestal, this to a similar plate below the bottom of the pedestal, 
and this again to the platform on the top of the piles, — so that one con- 
nected chain of iron runs from top to bottom of this compound pillar, and 
binds the whole into one mass. 
Fastenings. — The chains are made fast at their extremities, each to a cast iron 
bracket, which is bolted to the top of a wooden platform, 20 feet square, 
and resting and firmly attached to a series of piles, driven deep and firmly 
into the soil below. The 36 bolts of the main chain, as they approach this 
platform, are spread out from their compact square of 2 feet to cover the 
above platform of 20 feet square, and each is then attached to its bracket. 
The platform is then loaded with sand, or gravel, till the incumbent 
