5234

 

II*  

Designated  

22/02/1991  

23/08/2002  

The Cob  

 

Gwynedd  

Penrhyndeudraeth  

Porthmadoc  

Boston Lodge  

258021  

338037  

 

The Cob crosses the Traeth Mawr and the mouth of the Afon Glaslyn in Tremadoc Bay estuary and carries both the A487 and the Ffestiniog Railway from Boston Lodge to Porthmadoc. Spans District and Community boundaries.  

Transport  

 

The Great Embankment or Cob was conceived by William Madocks MP and built in 1808-11 under his energetic direction; it was an ambitious successor to the bank of 1800 higher up the estuary and the difficulties that occurred during construction make this one of the most dramatic achievements in early C19 transport history. The need for this crossing was closely linked to Madocks' creation of Tremadoc and his plans for a new harbour at Porthmadoc as well as his involvement in the proposed route to Ireland from Porthdinllaen; a further purpose was to create agricultural land on the W bank of the Afon Glaslyn. Madocks relied principally upon his own knowledge to design the embankment, but various professionals, including John Loudon, were briefly involved. Barracks were built at both ends (Towyn and Boston Lodge) to accommodate the large workforce. The major problem in construction was that the force of the tide and the river was so great that the stones were washed away almost as soon as they were laid; another difficulty was that the course of the river was not diverted until after construction. It was opened in July 1811 and had cost approximately £60000; it quickly became a major attraction for artists and tourists. A severe storm in 1812 breached the embankment and major repairs had to be undertaken despite tremendous financial difficulties. In 1836 the lower Cob was added on the inland side to carry the new road while the original embankment was converted to carry the new Ffestiniog narrow-gauge railway - a slate transporting line from Blaenau Ffestiniog to Porthmadoc, constructed 1832-6. Prior to his death in 1828 Madocks had unsuccessfully submitted a Bill for a railway to the harbour. The railway was closed in 1946 but now operates again as a tourist line.  

Substantial rubble-built embankment approximately 1.5 km long, consisting of a lower (road) section and a higher (rail) section. The higher part of the embankment is approximately 6m tall with single track railway and flanking footpath; the later and much lower 1836 embankment has narrow twin-track roadway. The seaward (S) side is heavily buttressed by boulders gradually sloping down to the water; the buttressing on the (N) landward side is less substantial and is predominantly a grassed bank. Rubble slate-stone parapets, approx 0.5m to 1m high (except to the seaward side where it is concrete) - masonry breaks and changes in the coping indicated that the wall between the higher and lower sections has been heavily repaired. At the Porthmadoc end the parapet of the higher embankment terminates opposite No. 6 Tros Y Bont Terrace and beside the curve into the railway station. On both sides of the higher embankment at the eastern end there are steps down to the shore and the roadway. Beyond, the railway tracks curve NE or continue into the Boston Lodge Workshops. Beneath the curve is a semicircular arched recess, now blocked but originally serving as a passage beneath the railway; portal like entrance with coursed masonry and voussoirs. At the Boston Lodge end the list terminates at the gated steps between the railway line and the road. The western part of The Cob is in Dwyfor District and Porthmadoc Community.  

 

Listed Grade II* for its special interest as a recognised historic engineering achievement and for its visual contribution to the landscape, together giving The Cob a major place in the history of this area. Group value with the Tollhouse.