Rhas Las Drift Mine on Twyn-y-Waun common was driven between 1823 and 1827 and started to supply coal in large quantities from 1830. However, the early coal mining methods meant that as much as two thirds of the coal was left untouched, in fact the lower 4 foot seam was not mined at all.
A Dowlais Iron Company report dated 10 July 1863 compiled by a W Jenkins, advises that the average length of underground haulages from pit bottom to the collier’s working faces was 380 yards.
Another D.I.C report dated 21 August 1863 advises that the vertical height of the drift was 24 yards (72 feet)
Further information required
Rhas Las Pit was sunk to a depth of 181 yards in 1851. (operational on OS map dated 1884 and OS map dated 1901 2nd Edition)
As previously stated, the early coal mining methods meant that as much as two thirds of the coal was left untouched and this led, in 1853, to Lady Charlotte Guest negotiating the installation of winding engines at Rhas Las Pit and a change in the method of working the coal to the "longwall" system. For expert advice she had brought in Nicholas Wood, F.R.S., a mining engineer from Newcastle "who is considered the highest authority" and he was commissioned to survey and report on the Dowlais coal deposits which included the Rhas Las seam.
At this time the Dowlais Iron Company received a large order for rolling stock from the Russian Government and the opportunity was taken to bring the Grand Duke of Constantine to Dowlais as guests of Sir John and Lady Charlotte Guest. On the second day of their visit they were taken on an underground visit of Rhas Las Colliery. Comfort was minimal and the coal drams were fitted with seats and lined with calico.
Rhas Las Pit appears in Hunts Mineral Statistics from 1856 to 1870 but there is no entry thereafter or in the List of Mines )
The following is a letter from the Dowlais Papers from Iron in the Making. Dowlais Iron Company Letters 1782 - 1860 edited by Madeleine Elsas, Glamorgan County Archivist (1960)
John Habakkuk to George Thomas Clark [1857(1) f.284]