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From Cyfarthfa (Merthyr Tydfil) to Cardiff, 25.5 miles, with 50 locks
The canal head at Cyfarthfa was 568 ft above O.S. datum, and the canal joined the Bristol Channel via the Sea Lock.
The canal was joined by the Aberdare Canal at Abercynon.
1790 Construction started; Thomas Dadford was engineer. An extension from Merthyr Tydfil to Richard Crawshay's Cyfarthfa Ironworks was also built, although payment for it had to be settled by arbitration. Plans to build a branch to the Dowlais Ironworks and Penydarren Ironworks, which would have risen 411 feet in only 1.75 miles was dropped, to be replaced by two tramroads.
1792 The Merthyr to Newbridge (Pontypridd) section was completed
1794 Fully opened.
1794 December: The canal breached but Thomas Dadford refused to start repairs without payment. The canal company attempted to recover £17,000 from the Dadfords, and had them arrested. Two independent surveyors largely supported the Dadfords; only £1,512 was refunded
1798 A southern extension was opened giving direct access to the Bristol Channel - it was known as the sea pound.
1809 The Doctor's Canal branched off from Denia to Treforest
1885 Control of the Glamorganshire and Aberdare Canals passed to the Marquis of Bute.
1898 From this time, the Merthyr to Abercynon section was closed; the canal closed progressively as a result of subsidence and competition from the railways.
1915 Abercynon to Pontypridd closed
1942 Pontypridd to Cardiff closed
1951 Cardiff sea pound closed.
1951 Completely shut. Much of the canal had been built over by realignments of the A470 trunk road.
Melingriffith Water Pump: It quickly became apparent that the canal was short of water below Melingriffith. A waterwheel-driven pumping engine was built in 1795, with the agreement of the Melingriffith Tinplate Works, to pump water back into the canal after the water had been used to drive the machinery in the works. The pump is preserved in situ.
'The Glamorganshire and Aberdare Canals' Volumes 1 and 2 provide a superb source of information about the canal, with numerous maps and excellent illustrations