£50 Mr Stevenson’s Description of Bridges of Suspension. 
80 years. Here we have perhaps, again, been taught the 
more extensive application of this speedy and convenient method 
of crossing ravines and rivers, by the practice of our friends 
across the Atlantic. 
To what extent this mode of bridge-building may be carried 
is very uncertain, and he who has the temerity to advance scep- 
tical or circumscribed views on this subject, would do well to 
reflect upon the history of the Steam-Engine. When the Mar- 
quis of Worcester first proposed, by the boiling of water, to 
produce an effective force, no one could have conceived the in- 
calculable advantages which have since followed its improve- 
ment, by our illustrious countryman, the late James Watt. 
Every one must also see the effect progressively produced on 
the public opinion, by the several propositions brought forward, 
and the bridges already executed upon the catenarian principle. 
When, for example, we pass from the slender wire-bridges on 
the Gala, the Etterick and the Tweed, and consider the ad- 
vancement of chain-bridges from the Tees in 1741, to the 
Tweed in 1820, we look with confident expectation to the exe- 
cution of the bridge over the Menai Strait, both from the well 
founded deductions of theory and practice. 
The theorems on this subject, from the pen of Mr Gilbert 
Davies, (published in the London Quarterly Journal of Science, 
Yol. x., p. £30.), are equally satisfactory as they are elegant 
and simple ; and although we may not be prepared, in prac- 
tice, to go the lengths which theory would lead us, yet, we 
have no hesitation in stating it as our opinion, that the practical 
extent to which bridges of suspension may be carried on the ca- 
tenarian principle, is by no means exhausted. 
Edinburgh, 19 th July 1821. 
