Laigh Milton viaduct
Gatehead, East Ayrshire
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This viaduct was opened in 1812 as the first ever railway(?) viaduct on this planet.
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Built by the Kilmarnock and Troon Railway for the Duke of Portland it worked very well but of
course was a few years earlier than the invention of the steam locomotive.
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As you can see the wagon's flat wheels ran outside the vertical plates of the trackway and
on the flat tracks.
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From that you can see that on bends the wagons were guided by the inside
vertical plate and the outside vertical plate would have had little effect.