Chester and Holyhead Railway

In the parliamentary process, Stephenson was naturally challenged as to the feasibility of his tubular bridge, but succeeded in convincing sceptical members, and the (8 & 9 Vict. c. xxxiii) received royal assent on 30 June 1845.

After some experimentation, rectangular tubes (as opposed to circular or elliptical) were decided on, and a one-sixth scale model was tested to destruction. This gave Stephenson confidence in the concept, and auxiliary support chains earlier thought necessary were dispensed with. The erection would be performed by hydraulic jacks. Provided by Wikipedia