Coloured lithograph of the Col-des-Roches by Johann-Friedrich Wirz and Samuel-Ferdinand Gallot, circa 1820. Animation by Klaas Kaat. Musée d’histoire du Locle

Powered by water, driven by ambition

Jonas Sandoz acquired the concession to operate mills in the caves of Col-des-Roches thanks to his political acumen. It was a successful venture – until he ran into financial difficulties.

Caroline Calame

Caroline Calame is a historian and curator at the Fondation des Moulins souterrains du Col-des-Rochesthe, editor of the Nouvelle Revue Neuchâteloise and president of the Institut Neuchâtelois.

In August 1660, Jonas Sandoz informed the authorities in Neuchâtel that he wanted to put an old mill on the Col-des-Roches close to Le Locle back into operation. It had been signed over to him by his father Daniel Sandoz on 6 December 1659. To be more precise, Daniel had passed down to his son his water concession, spanning from Le Chastelard to the gates of Le Locle. This granted Jonas Sandoz the right to utilise the water flow, and to use the surrounding land to build a grain and scutching mill. The right to use water resources was subject to tight regulations at the time. To build or operate a mill, you needed a concession from the Cantonal Council, which governed the Principality of Neuchâtel on behalf of the Orléans-Longueville family. In return, the mill owner was obliged to pay a tax calculated on the basis of the number of machines and on the mill’s expected profitability.

The work Theatrum machinarum molarium, or ‘Showcasing the art of mill construction’ from 1735 explained and illustrated various mill types. The underground mills at Col-des-Roches comprised a grain mill, an oil mill to produce oil from nuts, as well as a scutching mill for hemp and flax, and machinery to press fruit. — The work *Theatrum machinarum molarium*, or ‘Showcasing the art of mill construction’ from 1735 explained and illustrated various mill types. The underground mills at Col-des-Roches comprised a grain mill, an oil mill to produce oil from nuts, as well as a scutching mill for hemp and flax, and machinery to press fruit. e-rara

The mill acquired by Jonas Sandoz had been built by brothers Pierre and Jacques Descombes in 1549, but was quickly abandoned as it was located in the middle of the Le Locle valley where the River Bied flowed sluggishly. The location was not suitable for harnessing the power of the water, so Jonas Sandoz asked the Cantonal Council for permission to relocate it and to give it a new base and location. Moving the mill downriver in a westerly direction brought it to a much more suitable – if unlikely – location: the cave at Col-des-Roches, a natural cave extending 20 metres underground. The water from Le Locle valley accumulated there, before plunging to depths of 10 metres. It was therefore an ideal spot from which to utilise the power of the water. However, building the mill there meant working underground in the cold, damp and dark for decades.

**The location of the mills was originally a large marshy area. Engraving from 1803.** Musée d’histoire du Locle

Three local men from Le Locle had already set about this task – eight years before Jonas Sandoz. On 23 November 1652, Isaac Vuagneux, Balthazard Calame and Daniel Renaud had been granted permission to utilise the flow of the River Bied and to build a mill with two waterwheels on the Col-des-Roches. In view of Jonas Sandoz’s claims, they braced themselves to defend their rights. But it was not a fair fight: Jonas Sandoz held prestigious offices as tax administrator for the district of Montagnes neuchâteloises and later, in 1678, as governor of the Civil Division of Le Locle. On top of that, he was a strong-willed, authoritarian and abrasive character who liked nothing better than a good quarrel, filing lawsuits against many people over the course of his life. On 2 August 1660, the Cantonal Council granted him the concession for the River Bied from the mouth in Le Locle – in other words, all the concessions from 1549 to 1652 rolled together – and the right to build four waterwheels for grain mills and two for oil mills and scutching mills. The founders of the mill were forced to leave, but received financial compensation.

Expansion within the caves saw the mills evolve into a subterranean factory. Animation by Klaas Kaat. Musée d’histoire du Locle

While we don’t know how Jonas Sandoz pulled off this victory, we do know the lengths he went to in another case, twenty years later. In 1682, he discovered an iron mine on Mont-Sassel (now known as the ‘Chapeau de Napoléon’) in Val-de-Travers and decided straight away to make use of it. Here, too, a concession had to be requested. But Jonas didn’t contact the Neuchâtel Cantonal Council, instead he went straight to the Duke of Enghien who was one of the two guardians representing the feeble-minded princes of Neuchâtel. The Duke of Enghien passed the application on to the Cantonal Council with a glowing endorsement. The fact that Jonas was willing to pay hefty tax of 3,500 pounds a year, probably worked in his favour. The concession deed was issued on 20 January 1683 and concluded for 20 years.

**The map from 1694 shows the Principality of Neuchâtel.** e-rara

In the case of Mont-Sassel, Sandoz made a mistake: he had failed to grasp that the metal industry in Val-de-Travers was in decline, in particular due to the excessive wood consumption. Without a secure supply of wood, the iron mine couldn’t be operated profitably. Sandoz’s finances were poor by this point and in 1684 he had to ask the Duke of Enghien for deferral of payment of his taxes. Meanwhile, however, his work at Col-des-Roches was a roaring success. He installed five waterwheels in the cave – fewer than the six to which he was entitled under the operating concession. He had the cave dug out to make space for wheels, but also channels so that water could flow from one wheel to the others, as well as passageways and steps for workers. It was a herculean task, which was done using rudimentary means, and was said to be completed in just three years. In February 1663, in recognition of “the major work and large sums he had spent on building the said wheels” the Cantonal Council granted Jonas Sandoz permission to install all the machinery he deemed necessary and to operate it using his waterwheels. This was surprisingly liberal given that a concession would usually describe the permitted machines in detail and set the tax according to the mill’s revenues.

The underground mills, with a constant temperature of seven degrees, are the only ones of their kind in Europe and can be visited all year round. Animation by Klaas Kaat. Guillaume Perret

In the late 1680s, the failure of the Mont-Sassel iron mine caught up with Jonas Sandoz. He was forced to hand over the mills at Col-des-Roches to his creditors ‘Buisson et Jandin’ in Geneva and ‘Couvreur, Hartner et Compagnie’ in Lyon. But his creditors had no interest in retaining the property in Le Locle valley. In December 1691, they sold the mills, which changed hands very frequently in the years that followed. The new owners consistently upgraded the mills. Around 1830, they were installed above ground, leaving only the waterwheels in the cave. And then, in 1845, a large building was constructed to house more modern, so-called English mills. Two turbines replaced the waterwheels in 1854. In the late 19th century, the advent of electricity made harnessing the power of water redundant. The mills were shut down and the buildings assigned to the Col-des-Roches abattoir close to the French border. After it closed in 1966, the site was restored and opened to the public in 1987.

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