Underground relics from 18th century Llansamlet

It appears that in the 1870s there was some sort of literary circle in the coal-mining community of Llansamlet. Edward Hughes, presumably the secretary of this group, submitted a letter to The Cambrian (22 March 1878) on coal working in the area in the previous century, based on two 'treatises' submitted at" ... our last literary meeting at the Cwm ..." One section of this letter is particularly interesting:

There are aged colliers now living at the Cwm, who, more than fifty, years ago, came across old workings underground that were entirely unknown to anyone then alive. In these workings were found several of the implements used by the colliers of old, such as mandrels, shovels, sledges, &c .... Little cars have also been found, which were used in hauling the coal from the headings to the bottom of the pit. The frames and wheels of these were of wood, the boxes of plaited willows, and they ran along wooden rails formed of three pieces of wood nailed together like a water-trough. It appears that these cars were pushed or pulled from place to place by men and boys, but in one old working a windlass was found, which had been used to draw the cars from the headings ...

If these abandoned workings were broken into in the 1820s, and nobody was alive at the time who remembered them, that indicates that at the latest they must date to the third quarter of the eighteenth century, which is the period when the coal in this district was being worked by Chauncey Townsend (1750-70).