The Thomas Viaduct or Latrobe’s Folly

Today, we look at a small pen and ink drawing which I came across this past week. It is a landscape in which the focus is a viaduct but amazingly this viaduct is not found here in England but in the USA.

The #ThomasViaduct crosses the #Patapsco River and Valley and its’ construction was finished in 1835. At that time, it was the first and largest multi-span masonry railroad bridge in the US – to be built on a curve!! It now is the world’s oldest multiple arched stone railroad bridge still in use.

The viaduct is 612 feet (187 m) long with each individual arch roughly 58 feet (18 m) in span. The top of the arches are roughly 59 feet (18 m) from the water below. The width at the top is a little over is 26 feet (8 m). The bridge is built of Maryland granite ashlar (finely dressed/worked stone) – also known as Woodstock granite – sourced from local quarries. It also has an added pedestrian wooden floored footpath supported by cast iron brackets.

In the drawing , you can see a 15 foot (5m) obelisk (left side between trees) which names the builder, the architect, the directors of the railway and others, as well as the dates of commencement (1833) July 4th and completion(1835) July 4th.

At the time of construction, many doubted that it would even hold its’ own weight. Thusly its’ nickname of #Latrobe’sFolly (after Benjamin Latrobe II the designer) but it proved all doubters wrong and since has survived the great flood of 1868 as well as Hurricane Agnes in 1972 (two floods which wiped out the Patapsco valley and nearly everything in their paths).

This magnificent structure was critical in the American Civil War as it was the only supply line into Washington DC and therefore heavily guarded against sabotage.

This little drawing might be the oldest image of the viaduct existing. I have seen online an etching done in 1858 which shows a view from much the same perspective (I date mine earlier than the engraving only by the size of the tree in the top left corner of the images). I have not found any information regarding an American – W H Radford. I have seen information regarding a William Radford (1817-1897) and his son William Harold Radford, engineer-bridge masters , specialists in bridge construction who lived in England but they seem to have no connection to bridges in the US.

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