2Y4 Mr Buchanan’s Report on the Bridge of Suspension 
which is only in that case Jth of a ton or less on the inch, and 
which even the iron alone would bear with safety. 
Lastly, the pillars will be in no danger of oversetting ; for as 
the chains are carried over the top of them, and bent downwards 
towards the ground, at the same angle at which they hang na- 
turally in the curve, the weight resting on the top of the pillars 
has no tendency to draw the pillars either to the one side or the 
other. There will be no strain, therefore, excepting from the 
weight pressing the pillars directly downwards, and this weight, 
instead of tending in any degree to overset the pillar, will tend 
rather, and in a remarkable degree, to keep it steady. So that 
although the pillar were not fastened at the base at all, it would 
still require a great force to bend it over, the enormous load at 
the top keeping it down. It is quite a different thing, as I can 
easily shew the Commissioners by a simple experiment, from a 
similar weight of stone or iron resting on the top of the pillars, 
which would undoubtedly render it top heavy, and liable to be 
overset by the slightest touch. There the weight acts on the 
pillars by a pressure or thrust from above ; here it acts by a 
draw from below : the one is the unstable equilibrium which 
can scarcely at all be preserved, the other is the stable equili- 
brium which can scarcely at all be overturned ; and this is the 
reason which has made me prefer, as a prop for the chains, a 
slender pillar of iron in place of stone-work, which, owing to 
the loose connection of its parts, is less fitted to withstand any 
undulation in the bridge, and would require, therefore, in or- 
der to form a durable support, a much larger mass than what is 
now proposed, and such as would lead to greater expence. 
The foundation of the pillars are to be laid on the site of the 
present piers, and with their centres within two or three feet of 
the line of the outside of the roadway, which may be done with- 
out taking down much of the present arches. These founda- 
tions to be laid at the level of low-water, and on a strong body 
of piles and planking. By finishing each pier separately, the 
pillars may be built, the chains suspended, and the whole work 
go on nearly to a close, without interrupting the usual passage 
of the bridge. On the northern side of the river these pillars 
can be built so as rather to strengthen than endanger any far- 
ther the present north pier; at the same time I cannot help 
