1822.] 
great platform is suspended at the 
height of twenty-seven feet above the 
surface of the summer water of the 
river. Itis also made to rise abouttwo 
feet in the centre, and is finished on 
each side with a cornice of fifteen 
inches in depth. 
_ The roadway is suspended from the 
catenarian or main chains by circular 
rods of iron, which measure one inch 
in diameter. These perpendicular 
rods are wedged into caps or pieces of 
cast-iron, called saddles, which are 
placed at the distance of five feet 
apart, and are made to rest upon the 
shackles or joints of the chains. The 
attachment of the lower ends of these 
rods to the beams of the platform which 
they pass through, is by their em- 
bracing a bar of iron which runs along 
the whole extent of the bridge under 
the beams of the roadway, on each 
side. These bars measure three inches 
in depth, and they are connected with 
the suspending rods by a spear or bolt, 
which, in a very simple manner, com- 
pletes the connexion of the roadway 
with the perpendicular suspending 
rods, and chains. 40) 
The chains of this bridge are twelve 
in number, ranged in pairs ; the one 
pair being placed over the other, be- 
tween the points of suspension on each 
side of the bridge. These chains, and 
indeed the whole of the iron-work, is 
made of the best Welch iron. The 
chains are worked into a circular 
form, and measure about two inches in 
diameter. The links, as they may be 
termed, consist of rods of fifteen feet 
in length, and have bolt-holes, which 
are strongly welded, and neatly 
finished at each end. These links or 
rods are connected together by strong 
shackles, and a bolt is passed through 
them, which is of an oval form, mea- 
suring 24 by 2! inches. At each joint 
of the three tiers of the catenarian 
chains respectively, one of the saddle 
pieces of cast-iron are introduced. 
The first saddle-piece, with its sus- 
‘pending rod, for example, on cither 
side of the bridge, may be conceived 
as resting on the upper pair of chains; 
the next saddle-piece in the longitudi- 
nal direction of the roadway, rests upon 
the middle pair of chains, and the third 
upon the lower pair, and so on alter- 
nately, throughout the whole extent of 
the bridge. By this means all the 
‘chains bear an equal strain, and the 
Joints are arranged in so precise and 
orderly a manner, that a saddle-piece 
Montuty Mac, No. 371. 
New Patents and Mechanical Inventions. 
65 
and perpendicular suspending-rod oc- 
curs at every five feet, so that the dis- 
tance between each pair of suspending- 
rods forms a space of five feet. The 
spacesof five feet between the suspend- 
ing rods are formed into meshes of six 
inches square, to the height of five 
feet on each side of the bridge, and 
answer the purposes of a parapet wall 
for the safety of passengers. ‘ 
Though the timber roadway is only 
about 361 feet in length, yet the chord- 
line of the main-chains measures no 
less than 482 feet between the points 
of suspension, with which they make 
an angle of about 12°, and in forming 
the catenarian curve-drop, at the rate 
of one perpendicular to about seven 
feet in the length of chain, the versed 
sine of the middle pair of chains being 
about twenty-six feet. The twelve 
main-chains, with their apparatus, 
weigh about five tons each, and the 
weight of the whole bridge, between 
the points of suspension, has been esti- 
mated at 100 tons. 
On the Scotch side of the river, the 
catenarian chains pass over a pillar of 
aisler masonry, which measures sixty 
feet in height, is about thirty-six feet 
in its medium width, and seventeen 
and a half feetin thickness. The sides 
of the lower ten feet of the walls of this 
pillar are square, but at this height the 
walls begin to slope at the rate of one 
perpendicular to twelve horizontal. 
The archway in the masonry of this 
pillar, which forms the immediate ap- 
proach to the roadway, measures twelve 
feet in width, and seventeen feet in 
height. Each pair of main chains, 
being suspended horizontally, pass 
through corresponding apertures in the 
masonry, at the distance of about two 
fect above one another, and go over 
rollers connected with the building. 
The links of the main chains at these 
points are made as short as the 
strength or thickness of the iron will 
permit of their being welded, in order 
that they may pass over the rollers, 
without distorting or unduly straining 
the iron. After going through the 
masonry of the pillar, the chains are 
continued in a sloping direction to the 
ground. Here they are sunk to the 
depth of twenty-four feet, where they 
pass through great ballast-plates of 
cast-iron, into which they are stopped 
by a strong iron spear or bolt, of an 
oval form, measuring three inches by 
three and a half inches in thickness. 
The cast-iron ballast plates measure 
K Six 
