to the south is White or Berw Bridge, designed by Pontypridd Urban District Council's surveyor, P R A Willoughby. It was built in 1907, aided by L G Mouchel & Partners, who pioneered the use of reinforced concrete, and the span over the river was the longest arch in Britain using this material when it was constructed. The next crossing is Pontypridd Bridge, a high-arched single span of . It was built in 1756 by an Independent minister and self-taught civil engineer called William Edwards, and was his third attempt, after his two earlier bridges collapsed. It features three round openings in its spandrels, a device he used to relieve the pressure on an unusually wide arch. It was repaired by Edward David and Thomas Evan in 1798, and is attached to the newer Victoria Bridge on its south side. On the east bank is Ynysangharad Park, where there is an Arts and Crafts lido, designed in the 1920s and opened in 1923. It is now disused, but is grade II listed, as it is one of the earliest outdoor lidos in South Wales. On the west bank, the river is joined by the Afon Rhondda, before it sweeps to the east in a large bend. The A4058 dual carriageway crosses the bend at an angle, and as the river resumes its southward course, it is crossed by Machine Bridge, which is also known as Pont y Doctor, as it was built by Dr Richard Griffiths in 1809, as part of a tramway to carry coal from the Hafod Uchaf pit to the Glamorganshire Canal. It has three arches, and was widened around 1910, in an early use of reinforced concrete. Some of the 19th century fabric remains, and is thought to be the earliest multi-span railway bridge still in existence in the world. Two more modern road bridges are located on its south side, and further downstream is Castle Bridge, a narrow structure with three arches dating from the early 19th century. It formerly carried a road, but is now only used by pedestrians. Next there is a large, crescent-shaped weir, which was built in 1834–5 to provide water power to the Treforest tinplate works. The sluice to control the flow of water to the works is at the western end of the weir, and probably dates from a little later. The works continued in operation until 1939, and