The Gorseddau Junction & Portmadoc Railways

Outline History, Route and Visible Remains

While the derelict Welsh Highland trackbed is now being restored to use as a railway, there are many vestiges of other former narrow gauge railways in this part of North Wales which are most unlikely ever to be rebuilt. Perhaps the most striking are those of the spectacularly unsuccessful and long-closed Gorseddau Junction & Portmadoc Railways (as the enterprise was called at its brief greatest extent), which linked Portmadoc (now Porthmadog; this page uses outdated spellings where they seem appropriate) with slate quarries and a metal mine in two valleys to the North, and shared some characteristics with the Croesor Tramway, which was later upgraded to form the southern end of the Welsh Highland. The Gorseddau (or Gorsedda, the spelling used by at least one of the companies involved, and which reflects local pronunciation) never carried any kind of official passenger service, and was dismantled just over a century ago. This page is intended as a general introduction to the Gorseddau line (whose curious history is by no means complete), and to illustrate features that may interest the visitor.

Note: while parts of the Gorseddau route are public rights of way, many others are not. Follow the Countryside Code. Old quarry and mine workings are dangerous places; approach with great care, or stay outside and view from a distance.

The Tramway to Gorseddau Quarry

The history of the Gorseddau is characterised by considerable, misplaced optimism by quarry owners in the mid-19th Century. While fortunes were being made in Blaenau Ffestiniog, the Nantlle Vale, Penrhyn and Dinorwic, there were other ventures that failed miserably - few more so than those served by the Gorseddau, which was no doubt built to follow the model of the successful quarries of the time, which were linked to the sea by narrow gauge railways. For information on the North Wales slate industry, a visit to Dave Sallery's Welsh Slate Quarries site is strongly recommended.

Gorseddau Quarry (slate) is located at the head of the valley of Cwmystradllyn, and is visible in the distance from the A487 Caernarfon-Porthmadog road. It saw massive investment and development in 1855-6, with terraces on nine levels, a slate mill unlike any other in the industry, and a tramway to Portmadoc, the Gorseddau Tramway. This was, in effect, an extension of an existing line linking Portmadoc to small ironstone workings between Tremadoc (now Tremadog) and Penmorfa. Part of its route ran alongside a land drain which had been improved to form a short canal (Y Cyt) to Tremadoc, which remains visible alongside today's WHR (Porthmadog) car park, adjacent to the point where crossing the line would later prove an irritation to the Cambrian Railways (whose standard gauge line was built later and crossed it on the level; the stiles across the Railtrack line today mark the Gorseddau course).

The gauge was three feet, which may seem unusual in view of the gauge of just under two feet of the Festiniog Railway, and later, the Croesor Tramway. However it is less unusual given that the longer-established Nantlle Railway was to 3'6" gauge (and at the time, still ran all the way to the Menai Strait), and that the tramway used for construction of the Cob at Portmadoc may have been to 3' gauge, and some of its materials may have been used in the Tremadoc Tramway.

While the Tremadoc Tramway was virtually level, its extension to Gorseddau required gradients of up to 1 in 23 to climb the escarpment, and a reversal to gain height between Tremadog and Penmorfa. This spot was the Gorseddau Junction of the title, and is now underneath the site for the new community hospital. As on the Festiniog, uphill workings would essentially have comprised empty wagons, and horse traction was used. Wagons were supplied by the Festiniog Railway's Boston Lodge Works, but nothing is known of their detail.

Ynys y Pandy Mill

Six miles from Portmadoc, the route reaches the site of its most distinctive, indeed unique feature - Ynys y Pandy slate mill, or more properly Ty Mawr [Great House] Ynys y Pandy (to confuse matters further, the sign on the gate calls it Pont y Pandy, after the adjacent bridge). Slate mills are, conventionally, more or less windowless single-storey buildings located within a quarry. Ynys y Pandy (the spelling Ynysypandy is more grammatically correct but less commonly used) is utterly different, and is probably the most remarkable ruin in North Wales, striking for its location as well as its design. It was built remote from Gorseddau Quarry for the simple reason that there was no adequate source of water power at the quarry, but this is not enough to explain the character of the building. It had two main floors, each linked directly to the tramway, plus an attic and a basement in one corner, contributing to the impression of height. There was an internal waterwheel, large arched windows, and a (presumably ornamented) slate roof which was said to be the finest in the district. The Company spent ten thousand pounds on the mill machinery alone; to put this into context, its maximum entire capital was 125,500, a very large figure for an undertaking of this scale in the 1850s.

In some ways it is more reminiscent of the textile industry than of slate quarrying, and it must have been very expensive to build. It may well have been intended as a model to serve as an example to others, not unlike the Manufactory (woollen mill) which formed part of William Alexander Madocks' model township of Tremadoc, and also still stands. Visually, the mill recalls a cross between a ruined abbey and a very large nonconformist chapel - indeed it is said to have been used as a meeting hall before its machinery was stripped out and the roof was removed, which is thought to have happened in 1906. The structure is now a Scheduled Ancient Monument, owned and maintained by the Snowdonia National Park.

Dr Michael Lewis has published what may well prove to be the definitive scholarly account of Ty Mawr, modifying numerous previous assertions about it, and providing a credible idea of the internal arrangements, based on an archeological survey in 1995; see the reference to the article in vol.3 of Industrial Gwynedd, in the Bibliography at the end of this page. Lewis ascribes the building's design to James Brunlees (later Sir James), engineer of the tramway, who had already been involved in the creation of comparable buildings for different (engineering) purposes in the Manchester area.

Unlike many of the surviving slate mills in North Wales, Ynys y Pandy was built specifically to process slate slab rather than roofing slate; the industrial production of roofing slates in mills was in its infancy when the Gorseddau line was built, and they were generally produced entirely by hand within the main quarry workings. Slab was extensively used for many purposes, such as flooring, window sills, and gravestones, and its preparation involved sawing, planing, and in some cases polishing. Slab production is perhaps more commonly associated with the type of slate rock extracted further south, for instance around Corris and Aberllefenni, and the generally very high-grade slate found in northern Snowdonia was usually split into roofing slates. It is thus possible that the decision to concentrate on slab production from the Gorseddau Quarry, whose rock was of most inferior quality, was the single apparently sensible element of the plans.

One remaining puzzle about the mill is why, albeit ruined, it was not demolished when it was stripped out. Presumably, while there was profit in the sale or scrapping of the machinery, and in the sale of roofing materials, timbers and even perhaps the windows, there would have been little financial reward for the effort of taking down the walls of such a substantial and solid structure. Or it would be pleasing to think that there may have been some appreciation of the picturesque character of the remains.

Gorseddau Quarry

Beyond Ynys y Pandy, the line to Gorseddau Quarry, slightly more than two miles further on, bears right into the head of Cwmystradllyn, to the left of the lake (now a reservoir, popular with anglers), and is easy to follow. The massive investment in the quarry at this remote spot included the building of eighteen houses for workers, above the line roughly half a mile before the quarry, comprising the village of Treforus (or Treforris, or Treforys), long since abandoned, insofar as it was ever really occupied.

Although comparatively large, Gorseddau Quarry was anything but a success. At the peak of production in 1859/60, it produced no more than seven tons of slate per man per year, and it closed as early as 1867 (though as with many closed quarries, there may have been some later small-scale extraction). Even to the untrained eye, it is clear that the strata are different from what is seen in many slate quarries, and the rock is reputed to have been found either bad, or hard to work, or both. For a quarry closed over 130 years ago, a surprising range of buildings and other features are still to be seen, including the small huts or waliau used for production of roofing slate at this time, before larger mills came into common use for this purpose. The prime feature is however the "Wailing Wall" which overhangs the tramway as it approaches the quarry yard. This appears to have been created as a retaining wall to prevent slate waste engulfing the line. The conventional wisdom in other quarries would probably have been to move the tramway, but clearly the developers of Gorseddau did not think the same way as others did.

Reopening and Extension

With the closure of Gorseddau Quarry, the tramway fell into total, or at least partial disuse (in addition to meagre slate traffic, it transported some goods inland), and would have stayed that was had it not been for the development of the Prince of Wales slate quarry in the nearby valley of Cwm Pennant, to the North. Cwm Pennnant was the site of a considerable number of unsuccessful mining ventures, many with the involvement of the wealthy and somewhat eccentric Huddart family of Brynkir, of whom it was said that they "poured money into holes in the ground and called it mining."

Thus 1872 saw the authorisation by Act of Parliament (the Gorseddau Tramway was built without any statutory authority) of proposals by the recently formed Gorsedda Junction and Portmadoc Railways Company, to regauge most of the Gorseddau Tramway to 2' gauge, and extend it by almost five miles to Prince of Wales. The extension started at a junction with the line to Gorseddau Tramway at a place known as Braich y Bib (or Braich y Big, name of an adjacent farm), half a mile or so beyond Ynys y Pandy. It seems that the remainder of the old route to Gorseddau, if used at all, was not regauged.

The ambitions of the new enterprise seem almost humorous with the benefit of hindsight; certainly all its published claims should be taken with a very large dose of salt, for instance the statement that the GJ&PR's profits would probably be "greater than that upon any railway yet constructed in the United Kingdom." The delusions of grandeur are also suggested by the company crest, showing a Double Fairle locomotive (of odd detail) which could never have been used on the line, and indeed by the company title. The plural form "Railways" suggests a wish to emulate the main line Cambrian Railways more than an intention to reflect the two possible destinations of Gorseddau and Prince of Wales. The grand-sounding "Gorseddau Junction" in fact refers not to Braich y Big (itself surely one of the most modest meetings of railways anywhere), but to the point between Tremadoc and Penmorfa where the previous Gorseddau Tramway joined the still earlier Tremadoc Tramway, and promptly reversed direction to gain height. In all fairness to the Company, it should be pointed out thay it did indeed build the line much as promised, and (1874) introduced steam traction in the form of Pert, one of the small vertical-boilered locomotives built by De Winton of Caernarfon, who also supplied fifteen wagons. However it is believed that Pert did little work, most haulage being by horses.

Prince of Wales Quarry

Prince of Wales Quarry, even more so than Gorseddau, represents the triumph of geology over commercial optimism. It stands at the head of Cwm Pennant, and is connected to the Gorseddau at the site of its own small mill, at a site known as Cwm Trwsgl (the Ynys y Pandy mill was also purchased for Prince of Wales work, but may not have been used). From here an incline (drumhouse in upper centre picture) rises to a reservoir and short tramway leading to the foot of the central quarry incline (upper right), which was clearly extended upwards with the workings. Unlike in many quarries, the terraces which are evident on the hillside (ruins of barracks and offices on one of them, lower left picture) are not themselves slate workings, but were in fact solely for tipping waste, the actual workings being to the right on the left upper picture.

Put simply, Prince of Wales Quarry was a hopeless failure. Following the general principle that a slate quarry produces about ten tons of waste for every ton of roofing slate, the modest amount of waste in its tips shows that total production was at best meagre, despite the extensive investment. The quarry closed in 1886, though as at Gorseddau and elsewhere there was some sporadic later working, with one serious attempt at reopening after World War One.

The Final Straw: Cwm Dwyfor

The slate quarries at Gorseddau and Prince of Wales were not the only hopeless causes served by this most unlucky of railways. The extension to the head of Cwm Pennant brought a railhead within reasonable proximity of Cwm Dwyfor, a striking bowl in the mountains to the North. Although trials for slate were made here (the same is true of almost any hillside in Snowdonia), this became the site of a remarkably unsuccessful metal mine, which did at least attain the distinction of being the only metal mine in the district with a direct rail link to the sea. Vigorous attempts were made to attract investment in the mine from 1868 onwards, with claims that were at best over-optimistic and at worst dishonest, and which led to sufficient fools being parted from their money to see the site developed and a one-mile branch line built from the Prince of Wales mill at Cwm Trwsgl to the mine, arriving there via a final incline. The start of the branch was through a thirty-foot deep cutting (left-hand picture below), which has partially collapsed.

The tonnage of rock removed in the creation of this cutting was surely far greater than the total amount of ore from the mine ever sent out over the railway - a miserable 34.5 tons, enough for perhaps two short trains in total. Closed as early as 1877, the Cwm Dwyfor mine's owners seem even to have been uncertain as what was to be mined - although originally promoted as a copper mine, it produced rather more lead than copper ore.


With the complete failure of the quarries and mine it was built to serve, the Gorseddau ceased working at an indistinct point not later than 1892. The little-used Pert (which may have been out of use from as early as 1878) is believed to have been sold on by a local dealer to a quarry in the Nantlle Vale (Coedmadoc, also known as Cloddfa'r Glai, or Gloddfa'r Glai), which closed in 1908, after which all trace is lost. The Gorseddau line passed almost unnoticed into history - there do not even appear to be any photographs taken during its existence - and had been dismantled by 1898. It is known that the seaward end was dismantled in 1896 by Owen Roberts and Robert Isaac of Portmadoc, who had purchased Ynys y Pandy mill for a mere 100 two years earlier, and were presumably later responsible for stripping it out. The only length to see later use was within Portmadoc, used by a mineral line from Moel y Gest Quarry, and to serve a slate works before making a junction with the Croesor Tramway (later - and future - Welsh Highland) near the tall flour mill building that still stands (now a pottery) in Snowdon Street.


This account is indebted to the following sources, of which first-hand observations are largely confirmations or subjective modifications. Where (as is inevitable with this subject) there are inconstencies between them, a subjective attempt has been made to pick the more credible option! Errors or inconsistencies created from thin air are my own.

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This page is presented as an "extra" to the Welsh Highland Railway Project site, as an item of potential interest to visitors to that site, and NOT with any suggestion that any restoration of the Gorseddau should, or could, form part of that or any other railway restoration initiative. Otherwise, credits, disclaimers and conditions of use are the same as those set out at the foot of the WHR Project homepage.
Authored by Ben Fisher; last modification to this page October 27th, 2006.