The Slate Industry of North and Mid Wales

Cornish Beam engine, Dorothea Quarry, Dyffryn Nantlle.

At the beginning of the 20th Century, Dorothea quarry was urgently in need of a long term solution to the ongoing problem of keeping the workings, by then over 500 feet deep, free of water.  It was decided to purchase a Cornish beam engine.  An old but reliable technology.  The engine was built by Holman Brothers and was the last but two ever built.  It is also believed to be the newest Cornish beam engine still in existence.  The engine was able to pump 10 gallons of water per second from a depth of over 500 feet.   The engine started work in 1906 and served until 1951 when it was replaced by a 60hp electric pump.    Apart from a brief period in 1956 the engine has been disused ever since.

 Following closure of the quarry in 1969, the site has been owned by several companies, each with its own priorities and plans - none of which have included the engine.  This has made the restoration and maintenance of this important artifact extremely difficult.  In fact, grants have been made available towards its restoration but have subsequently been withdrawn because of the problems of access.  The enginehouse is a Grade 1 listed structure which is the same as Caernarfon Castle.  Despite this, and despite the valiant efforts of the engine's custodian, it continues in a state of limbo.  What should be one of North Wales finest examples of industrial heritage is now a forgotten link to a golden age.

This view of the engine house and quarry was taken in the early 1950's.

Michael Bishop took this photo in the early 60's.

This commemorative stone is at the base of the structure.

One of the two Lancashire boilers which supplied the steam for the engine.

View from above of part of the two massive boilers, much of the piping is still intact although the boiler house roof has been removed.

The huge 68" diameter single cylinder.

The main beam is a steel casting and weighs over 23 tons.  Half the beam is seen here - the rest is outside beyond the wooden wall.  The bearings on which the beam pivots are next to the wall.

The engine pumped water from a shaft 155 yards deep, this a view of what remains of the pumping rod.   It is attached to the end of the beam.  As the beam rotated back and forth, it activated the pump.

Next page: Dwr Oer Quarry, near Blaenau Ffestiniog

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