And the next image is the Britannia Bridge which was originally built in 1850 and was the pioneer of tubular construction. So many bridges and buildings are constructed out of tubular steel these day that we tend to take it for granted. Stephenson's problem in constructing the bridge was how he could span the supporting towers, a suspension bridge could not cope with the weight and the vibration of a train so another way had to be found and it was discovered that tubular steel was both lighter and stronger than solid steel so huge rectangular steel sections were bolted together and hauled into position. This was the first tubular steel section construction in the world. Well, no it wasn't actually because his engineers experimented the theory with the railway bridge at Conway Castle so that must have been the first.
This one mile stretch of water is very important in engineering terms as we shall see when we talk about
Telford's Menai Bridge later.