Chromolithograph advertisement produced by the Berlin Iron Bridge Company of Connecticut, with artwork by Gies & Co. An engine drawn by six horses is crosing this lenticular bridge, with a steamboat with pasengers pasing beneath the bridge. The steamboat is flying the American flag. Lenticular bridges, so named because of the lens shape, used a parabolic trus to transfer weight from the centre out to the ends. This design was developed by William O Douglas of Binghamton, New York. Douglas' Berlin Iron Bridge Company constructed many such bridges which were cheaper than conventional truses as they used les steel. Dimensions: 380mm X 610mm.
© Science Museum / Science & Society Picture Library