Mr Stevenson's Description of Bridges of Suspension. 2:4% 
1'ormed into links of from five to six feet in length. The screw- 
bolts are 1 inch in diameter, and are in all 42 in number, by 
which the whole of the suspending rods and wires may be 
tightened, and set up at pleasure. When thus braced, the 
roadway of the bridge is found to have little or no vibration, 
having only such a tremor as rather tends to convey the idea of 
firmness and security. As a proof of the strength of this 
bridge, when newly finished, it was completely crowded with 
people, without sustaining any injury. 
Thirlstane Wire-Bridge. — The only other wire-bridge 
which we shall notice, is that erected by the Hon. Captain Na- 
pier, over the Etterick, at Thirlstane Castle. A foot-bridge of 
ropework had originally been thrown across here ; but a wire- 
bridge is now erected, and measures about 125 feet span. 
Dryburgh Chain-Bridge.— The wire-bridges of Galashiels, 
Kingsmeadows, and Thirlstane, above described, are suspended 
by diagonal braces, as shewn in Fig. 2. The same plan was also 
followed in the first erected bridge at Dryburgh Abbey, where 
the suspending rods were also made to radiate from their points 
of suspension on either side, towards the centre of the roadway, 
for as yet the catenarian principle had not been introduced upon 
the Tweed. The bridge at Dryburgh is 260 feet in extent 
between the points of suspension, and is 4 feet in breadth. It 
was executed by Messrs John and William Smith, builders 
and architects near Melrose, at the expence of the Earl of Bu- 
chan, as proprietor of the ferry, and has altogether cost his 
Lordship about L. 720. This bridge is constructed for foot pas- 
sengers and led horses. It was originally begun on the 13th of 
April 1817, and was opened to the public on the 1st day of 
August following, having required little more than four months 
for its erection. 
It is observed by Mr John Smith, one of the gentlemen above 
alluded to, that when the original bridge of Dryburgh was finish- 
ed, upon the diagonal principle like Fig. 2,, it had a gentle vi- 
bratory motion, which was sensibly felt in passing along it ; the 
most material defect in its construction arising from the loose 
state of the radiating or diagonal chains, which, in proportion to 
their lengths, formed segments of catenarian curves of different 
radii. The motions of these chains were found so subject to ac- 
