March 1869: The Tower Subway

Occasionally, digging back through The Engineer archives, we come across glimpses of forgotten infrastructures and technologies — brief flashes of things that have been superceded, which make landscapes and activities now familiar to us seem strange and alien.

Consider, for example, London’s iconic Tower Bridge. It’s such an instantly recognisable landmark that it seems to us that it’s always been there: that as long as the Tower itself — a medieval castle, don’t forget — has been there, people have crossed the river between its two square pinnacles.

That’s not the case, of course; the bridge is relatively recent, finished in 1894. Before that, the question of how people should cross the river was tackled differently, as described in a particularly crumbly and fragile bound volume of The Engineer.

An engineer named Peter Barlow proposed that a subway should be built under the river bed, as it was the only way that a river crossing could be achieved: an attempt to bridge the river had failed in 1863, because of ‘the great height required for the passage of ships’ (a problem solved by Tower Bridge, of course, by allowing the roadway to rise). Steam-ferries across the river wouldn’t work either, because they would disrupt shipping too much.