The huge water wheel still turns, though the great rollers of the crushing mill now stand silent. Beside the wheel there is a pointed reminder that machines are often dangerous. In 1879, the notice says, a lad called Thomas Heslop, who had been ordered to oil the bearings, got caught up in the rollers and was killed. Only fragments of his body were recovered. The nine-year-old primary school pupil who is standing beside me - he must be about the age that Thomas Heslop was - looks up at me, profoundly impressed. "Cor!" he says.
We are at Killhope, high in the deserted Pennine hills, close to where the counties of Durham, Cumbria and Northumberland meet. This area was the heart of Britain's lead industry: wherever you look you can see traces of the old mine workings and in neglected fields the remains of the miners' cottages and gardens. There has been lead mining here since medieval, and probably, Roman times. In the middle of the 19th century, before foreign competition forced prices down, it made the mine owners, and a handful of the miners too, rich.
Traditionally, the mined ores were hauled out of the level by sturdy ponies and then had to be crushed and finely separated by hand. Much of the work was done by boys like Thomas Heslop, but as the demand for lead rose so did the need for new investment and mechanisation. That was how, in 1876, the Killhope Wheel and Crushing Mill came to be built.
In its heyday it was one of hundreds. Now, restored and still driven by water, it's the sole survivor. With the rest of the equipment of Park Level Mine, also carefully restored, it forms part of the Killhope Lead Mining Centre.
A Year 5 group from Newker primary school in Chester Le Street, County Durham, is among many to discover that the learning experience it offers is enthralling. Worksheets are not needed on this tour; children need both hands free. They are encouraged to dress in period style (all costumes are provided) and they can cook on the lodging house peat fire, test the wooden bunks ("three to a bed and one across the bottom") and try their hands at the miners' diversions such as carpentry, draughts or knitting.
Outside, they work as crusher boys ("I liked smashing open the rocks and getting the crystals") and as washers, seeing for themselves how the repeated wahing cycle leaves even the tiniest grains of ore behind. They are allowed, indeed encouraged, to pocket any ores they find. They cheerfully get wet and learn that only when it froze so hard that washing was impossible could the children who worked here ever go to school.
They learn about trommels and jiggers and buddling and much, much more besides. They study the great iron wheel and learn about drives, gears and water power. And then they draw on their boots and lamps, hand in their tallies and go underground - the highlight of the tour.
After the first long tunnel, which is lined with masonry, much of what they see is skilful reconstruction but the authenticity - the water underfoot, the tallow candles, the tell-tale traces of lead sulphide ores - is convincing. The children, even the timorous ones, are fascinated. "It was fun," says Staci Jamfrey, "splodging in the mines and the water filling our boots and falling while exploring."
"But what a tiring, hard and exhausting life it was," exclaims Anna Peak. "When I got home I would have just flopped down on my bed."
The basic tour - with one excellent guide for each group of 12 children - lasts two hours or so, and the time goes quickly.
There is a visitors' centre and a meeting room that groups can hire. The excellent teachers' pack outlines not just the story of mining and mine-owning, but the stories of the miners and their families as well. There was a proud tradition of skill and independence among these self-taught people and the suggestions for drama follow-up reflect it well. And whatever your children ask you (about schools, health, earnings, accidents, geology, smelting) can be answered from these pages. Throw in the links to national curriculum attainment targets at key stages 2 to 4 and you are ready for an enjoyable learning experience.
Outside, there is a network of signposted trails above the site for groups who want explore a wider area or to picnic. The landscape, spare and remote as it is, is strikingly beautiful. But be warned: Killhope is over 450 metres above sea level. Warm clothing and stout footwear are essential.
* Killhope Lead Mining Centre, Cowshill, Upper Weardale, County Durham D43 1AR. Tel: 01388 537505.
www.durham.gov.ukkillhope Open from Easter to the end of October and at other times (for educational groups only) by apppointment. School parties pound;2.50 per child; teachers free 1:14.