Gwynedd Archaeological
Trust Regional Historic Environment Record
Pen yr Orsedd Slate Quarry, Nantlle
Primary Reference Number (PRN) : 20039 Trust : Gwynedd Community : Llanllyfni Unitary authority : Gwynedd NGR : SH5093853949 Site Type (preferred type first) : POST MEDIEVAL SLATE QUARRY
Description : Open pit working, but was originally developed in 1816 as hillside galleries. Mills built on three successive levels, the first in 1860 and the next, their first integrated mill, in 1870, the upper mill followed in 1898. Output in 1882 was 8251 tons with 230 men but in the next decade was much higher. The first connection to the Nantlle railway by incline via Pen y Bryn. When this area was tipped over direct connection was made to the railway. In final form the pits, which extended down to valley floor level were dewatered by a drain. Blondins and incline used. The 3 mills levels were connected by 2 incline pitches, with a third down to the terminus of the Nantlle railway. There were extensive tramways in 2' and 3'62g, locos being used on the former gauge. (De Winton in use until 1960). There was a proposal to form a connection with the N.W.N.G. Rly but it was never built. After closure of the Nantlle line in 1963 road transport was used. As a founder customer of the Cwmdyli Power station it was possibly the first quarry to use off-site generated electric power. In latter days the use of Blondins gradually ceased, a lorry road being built down into the one pit in use in the early 1980s. Immediately prior to closure in 1984 12 men were employed with only the top mill being used. Small scale workings from late 1980s.
Remains - There are the 4 pits (named William, Ellen, New and Eureka), but being partly rubble filled do not now reach their full depth. There are 4 access tunnels and a drainage tunnel. On the upper level are the structures and machine cabins (some with electric winches intact), of six, locally made, Blondins, some with quite complex pulley arrangements, (due to the fact that towers had to be moved while winding houses were fixed). there are various buildings including the mill with an Anderson Saw table, 10 Greaves dressers and a belt conveyor for mill waste. There are numerous artefacts on site including wagons and much trackage.
On middle level there are various offices and other buildings, a ruined mill and one mill virtually intact. This latter, laid out on an unusual back-to-back manner contains unique examples of De Winton saw tables with hydraulic table drive. A separate building, with an adapted shaping machine is laid out as a 'specials' department. There is a workshop with lathes etc.
On the lower level are further buildings including a mill with shafting and other machine remains. Some buildings have signs of late renovation. The drumhouses and inclines in unusually fine condition with track on the ground and hinged wooded crimp sprags. There are pleasing 'sentrybox' type banksman's shelters. Gear is conventional except for the use of pulley and weight counterbalances for the brake levers.
At the Nantlle railway terminus at the foot of the lowest incline are stables etc. associated with the line, including a building with a wheelpit alongside, where horse feed was prepared.
The well-known war memorial that was on site has been removed for safekeeping. (Davidson, Gwyn, Jones & Riley, 1994)
The middle level (Bonc yr Offis) at this site contains the best group of processing, ancillary, administrative and domestic buildings in the industry. The mill exemplifies the sequence of power-types (water-wheel, steam, electricity) and rope-transmission. On the upper level (Bonc Brig) the ropeway systems are already scheduled but the locomotive shed and weighbridge are also considered to be of national importance. (Davidson, Dutton, Flook & Gwyn, 1995)
