The Aeolus Waterwheel – Merthyr’s Great Wonder

When Rev Sir Thomas Cullum (8th Baronet Cullum) visited Merthyr Tydfil in 1811, one of the sights he was most taken with was the mighty Aeolus Waterwheel at the Cyfarthfa Ironworks, and he even called it ‘the wonder of the place’. Some contemporary accounts actually refer to it as ‘the Eighth Wonder of the World‘. I wonder how many people in Merthyr have actually heard of it nowadays?

‘Cyfarthfa Works and Waterwheel’ by William Pamplin. The Aeolus Waterwheel can clearly be seen at the centre of the illustration. Photo courtesy of Cyfarthfa Castle Museum & Art Gallery

When Richard Crawshay became sole owner of the Cyfarthfa Works in 1791, he began making plans to extend the works and come up with innovative ways to increase iron production. In 1792, he made the engineer Watkin George a partner in the firm, and the latter began making significant progress in maximising the potential of the works.

His major contribution was the construction between 1793 and 1797 of a huge overshot waterwheel to provide the air for the four blast furnaces.

According to volume 5 of Rees’s Manufacturing Industry (1819-20):

“…..the water-wheel is 50 feet in diameter and six feet wide: it is chiefly made of cast iron, and has 156 buckets. The axle is a hollow tube, and is strengthened by twenty-four pieces of timber applied around it. On each end of the axis is a cog-wheel of twenty-three feet diameter, which turns a pinion. On the axis of these are two cranks, and fly-wheel twenty-two feet diameter, and twelve tons weight; each of the cranks gives motion to a lever, like that of a large steam-engine, and works the piston of a blowing cylinder or air-pump 52½ inches in diameter, and five feet stroke, which blows air into the furnace, both when the piston goes up and down. The work on the other side being the same, it actuates in the whole four of these double cylinders; the wheel makes about two and a half turns per minute, and each cylinder makes ten strokes.”

At the time, it was the largest waterwheel of its kind in the world and was named Aeolus after a character in Greek Mythology. Aeolus, as mentioned in the Odyssey and the Aeneid,  was the keeper of the winds and king of the island of Aeolia, one of the abrupt rocky Lipara islands close to Sicily. Later classical writers regarded him as a god.

The wheel was operated by water fed from streams across the river and transported by a massive iron and wood double aqueduct mounted on stone piers between 60 and 70 feet high. This was the famous Gwynne Aqueduct. Sir Charles Manby (later Secretary of the Institution of Civil Engineers) visited Merthyr and commented that the aqueduct:

“…..maintained an apparent lightness of the whole that contrasted with the massy [sic] boundary of the river, has not only a singular, but also a very interesting and pleasing appearance.”

Gwynne Aqueduct from a painting by Penry Williams

This is the same aqueduct that was mentioned in the previous post about the Pont-y-cafnau (

The Aeolus Waterwheel continued to power the blast furnaces until the 1820’s when it was replaced by a steam powered engine, and was subsequently demolished.