MOUNTAIN ASH, an urban district of Glamorganshire, south Wales, in the Aberdare valley on the Cynon, a west bank tributary of the Taff, with stations on the Taff Vale and Great Western railways, 18 m.
The ancient commote of Senghenydd (corresponding to the modern hundred of Caerphilly) comprised the mountainous district extending from the ridge of Cefn Onn on the south to Breconshire on the north, being bounded by the rivers Taff and Rumney on the west and east.
The Barry line from Barry dock joins the Great Western and Taff Vale railways at Cardiff, and the Cardiff Railway Company (which owns all the docks) has a line from Pontypridd via Llanishen to the docks.
The Taff is spanned by two bridges, one a four-arched bridge rebuilt in 1858-1859 leading to Llandaff, and the other a cantilever with a central swinging span of 190 ft.
The Taff (40 m.), rising amongst the Brecon Beacons, enters the Bristol Channel at Cardiff.
In 1858 was opened the Rhymney railway from Rhymney to Caerphilly and on to Taff's Well, whence it had running powers over the Taff Vale railway to Cardiff, but in 1871, by means of a tunnel about 2000 yds.
Its station is a terminus on the Barry railway, which starts at Hafod in the Rhondda Valley, where it joins the Taff Vale railway, having also junctions with the same line for Aberdare and Merthyr at Treforest, and for Cardiff and Penarth at Cogan, and with the Great Western main line at Peterstone and St Fagans.
The opening of the Taff Vale railway in 1840 and of the South Wales railway to Cardiff in 1850 necessitated further accommodation, and the trustees of the marquess (who died in 1848) began in 1851 and opened in 1855 the East Bute dock and basin measuring 464 acres.
Under powers secured in 1884, the town obtains its chief water supply from a gathering ground near the sources of the Taff on the old red sandstone beyond the northern out-crop of the mineral basin and on the southern slopes of the Brecknock Beacons.
Still they fell far short of the requirements of the district for in 1865 the Taff Vale Railway Company opened a dock of 26 acres under the headland at Penarth, while in 1884 a group of colliery owners, dissatisfied with their treatment at Cardiff, obtained powers to construct docks at Barry which are now 114 acres in extent.