Stage 11: Albi – Toulouse

Coming back after the first rest day, we had from Albi, home of the pigeon-eating catfish, to Toulouse, capital of Occitània. A ford of the Garonne at Toulouse, known as the Bazacle, from the Latin vadaculum, “little ford,” lies just down the road from today’s finish line.

The mills at the Bazacle as seen in 1642. (source)

The first mills at the Bazacle, built in the 11th century, floated in the river. These were replaced by standing mills and a dam was constructed across the river during the 12th century. The mill owners founded the Société des Moulins du Bazacle in the 13th century. The owners received shares in the company and a percentage of the future revenue while the company took ownership of the mills at the Bazacle, making the Société des Moulins one of the first examples of a joint-stock company in the world. Supported by the wealth of the mill’s, Toulouse’s industrial district grew up around the Bazacle. At the end of the 19th century, the mills were converted into a hydroelectric power plant that still operates to this day.

Stage 10: Saint-Flour – Albi

Stage 10 takes us into Albi where the shallows of the Tarn River are stalked by “freshwater killer whales,” a population of European catfish that have developed a taste for pigeon.


European catfish hunt pigeons in the shallows of the Tarn (source: Cucherousset et al. 2012, PLOS ONE)

Catfish were introduced to the Tarn in 1983 and have firmly established themselves in the river. It has been suggested that the growth of the catfish population depleted the populations of prey fish, pushing the catfish to seek out a new food source. An excellent and abundant prey for any urban predator are the pigeons that inhabit major cities around the world. But how is a bottom-feeding catfish supposed to catch a flying pigeon? This video, taken by the authors of the PLOS ONE paper that reported on this behavior, shows how they manage it.


The pigeons of Albi frequent a small island where they drink and wash up in the Tarn. The catfish have learned that they can thrust themselves out of the water, beaching themselves on the sandy shore, and catch an unsuspecting bird. This behavior looks a lot like a killer whale or a crocodile, but it doesn’t appear to have been learned by catfish populations outside of Albi. The combination of an urban river, an abundant pigeon population that comes close to the water’s edge, and an introduced predator — all of which are direct consequences of human influences on the environment — has created a novel ecological interaction that reveals the tremendous potential for evolution in the built environment.

Stage 9: Saint-Étienne – Brioude

This hilly stage took us from Saint-Étienne, near the Loire, to one of that river’s main tributaries, the Allier, home to “l’ombre de la rivière,” the “shadow of the river” — the grayling.

A grayling (source)

The grayling is related to salmon and is found across northern Europe, where it is a popular target for fly fishers. The Allier hosts one of the southwesternmost populations of grayling on the continent. This population is disconnected and genetically distinct from those in the rest of the continent, including that in the Rhône.

Stage 8: Mâcon – Saint-Étienne

A thrilling stage took us from Mâcon on the Saône, which is thus in the watershed of the Mediterranean Sea across the European continental divide to Saint-Étienne on the Loire, which flows into the Atlantic Ocean. Along the way, we passed by Villefranche-sur-Saône home to the church of Notre-Dame-des-Marais, Our Lady of the Marshes.

The church of Notre-Dame-des-Marais. (source: Andrzej Harassek, CC-BY-SA 3.0)

Local legend has it that in the 13th century or thereabouts, some shepherds were tending their flocks in the wet meadows surrounding the Saône when they stumbled across a statue of Mary sunk in the marsh. They pulled it out and decided to build a new church near the location, which became Notre-Dame-des-Marais.

A painting in the church depicting the discovery of the statue in the marsh. (source: Quintius, CC-BY-SA 4.0)

Stage 7: Belfort – Chalon-sur-Saône

A long and flat stage took us past the twin saltworks of Salins-les-Bains and Arc-et-Senans, home to a long history of salt production.

The Jura region was underwater some 200 million years ago, and as those seas dried up, they left behind extensive deposits of salt. This salt dissolved in groundwater and bubbled to the surface in salt springs. Since at least the 8th century, the inhabitants of Salins-les-Bains starting collecting this brine and boiling it over an open fire using wood from the nearby forests.

The saltworks at Salins-les-Bains (source: Jean Housen, CC-BY-SA 4.0)

By the 18th century, the salt content of that brine was starting to drop, and the forests arounds Salins-les-Bains were depleted, slowing the production of salt. The French monarchy was heavily dependent on salt production through the tax known as the gabelle, so the Ferme Générale, the king’s personal tax service, started investigating means of improving salt production. In 1771, King Louis XV appointed the architect Claude-Nicolas Ledoux the Inspector of Saltworks in Franche-Comté, and Ledoux set about designing his dream salt factory. The site chosen for the new Royal Saltworks was the town of Arc-et-Senans on the Loue River and, more importantly, south of the great Forest of Chaux that would provide a seemingly unlimited supply of wood for the burners. A 21 km pipeline would be built from Salins-les-Bains to carry the brine to the new factory.

The Director’s Building at the Royal Saltworks at Arc-et-Senans (source: Rolf Süssbrich, CC-BY-SA 3.0)

Ledoux was not content with building any old saltworks. He was determined to make the Royal Saltworks the center of an Ideal City built to Enlightenment principles of order and rationality. In his plan, the saltworks occupy the center of a circle consisting of outbuildings for the factory workers while outside the circle lies the planned city. The factory was constructed by 1779 and started producing salt. However, the French Revolution in 1789 put a halt to Ledoux’s plans for the city.

Ledoux’s plan for the Royal Saltworks at the heart of his Ideal City (source)

The Royal Saltworks continued production until 1895, when rail travel made it easier to bring sea salt into the interior of the continent and evaporating brine was no longer worth the cost. The Salins-les-Bains managed to hang on until 1962, when it was shut down after nearly 1200 years. The two sites were inscribed on the UNESCO World Heritage list in 1982 and are open to the public today.

The underground gallery at Salins-les-Bains dates to the 13th century (source: Jean Housen, CC-BY-SA 4.0)

Stage 6: Mulhouse – La Planche des Belles Filles

Last time we came up to La Planche des Belles Filles, Fabio Aru won atop the mountain after passing through the Plateau des Mille Étangs. This year, we approached the mountain from the east, starting at Mulhouse, upstream from Colmar along the Ill in the Rhine Valley, so we only skirted the southern edge of the Mille Étangs. We did catch some glimpses of a few tiny lakes and reservoirs tucked away in the little valleys, such as the lac de la Lauch on the way up the Grand Ballon and the lac d’Alfeld and its smaller sibling, the lac de Sewen up to the Ballon d’Alsace.

The Lac de la Lauch (source)

The Lauch is the same river that runs through Colmar’s Little Venice, but before it gets there, it runs out of the Vosges Mountains through a valley called the Florival. Industrialists in the valley decided that they needed to supplement the water supply coming from the lac du Ballon, which lies just beneath the summit of the Grand Ballon, so they financed surveys for a new dam out of their own pockets. Construction on that dam began in 1889 and was finished by 1894, impounding eleven hectares to form the lac de la Lauch

The lacs d’Alfeld (foreground) and de Sewen (background). (source: Espirat CC-BY-SA 4.0)

The lacs d’Alfeld and Sewen sit on the Seebach, a tributary of the Doller two valleys southwest from the Lauch. The Germans built the dam at Alfeld around the same time at the one on the Lauch. The lac de Sewen, however, is a natural glacial lake and is surrounded by peatlands that are slowly encroaching on the lake, shrinking it from around thirty hectares to just six today.

A view from the peat bog surrounding the lac de Sewen (source)

Stage 5: Saint-Dié-des-Vosges – Colmar

A hilly stage took us through the Vosges and into the great valley of the Rhine. We stop before we get to that river in the picturesque town of Colmar. In the center of town, the old tannery row has been turned into “la Petite Venise,” where today we’ll take a relaxing gondola ride along the river before we head to the first mountain stage of the Tour tomorrow.

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These images and more of Colmar’s Little Venice can be found at Wikimedia Commons.

Stage 4: Reims – Nancy

The last kilometer of the stage took us along the Meurthe River in Nancy. Like other urban rivers in industrial regions, the Meurthe has a significant history of pollution. The Meurthe’s big problem is salt, a byproduct of the soda ash factories established upstream of Nancy.


The Solvay Plant at Dombasle. (source)

Soda ash is another name for sodium carbonate, which is an important industrial chemical. It is used, for instance, to make soda-lime glass, which is made into glass bottles. Soda ash was originally made by burning a plant called saltwort. But demand for soda ash incentivized several efforts to manufacture soda ash that culminated in the work of the Belgian chemist Ernst Solvay. His process combines sodium chloride, in the form of a brine solution, with carbon dioxide, generated by heating limestone, in the presence of ammonia. In 1864, Solvay built a factory just outside Charleroi to make with his process. By 1874, the Solvay company was looking to expand, and they decided to situate their new factory in Lorraine, where extensive salt deposits could be mined to supply the brine they needed. They chose Dombasle for their new location, right on the Meurthe upstream of Nancy.

The first reaction in the Solvay Process produces ammonium chloride as a byproduct. This ammonium chloride is then reacted with the lime (calcium oxide) left over from heating the limestone to make ammonia, which is reused in the first step, and calcium chloride, which is disposed of by discharging it into the river through a set of settling basins, which are the most visible aspect of the soda ash production along the Meurthe.

Production site for sodium carbonate near Dombasle-sur-Meurthe,

Settling basins along the Meurthe. (source: Jeroen Komen, CC-BY-SA 2.0)

There was initially some opposition to the Solvay factory, as some were concerned about the effects of the calcium chloride discharges into the Meurthe, which supplied Nancy’s drinking water. However, Nancy found other sources of drinking water and began to discharge sewage into the Meurthe in the 1880s (Garcier 2007), so that the chloride discharges were no longer of much concern to the citizens of Nancy.

Salinization of freshwater rivers is a global issue that significantly affects the integrity of these ecosystems (Cañedo-Argüelles et al. 2013). The salinity gradient along the Meurthe formed by the accumulation of chloride from the soda ash plants has been shown to decrease the diversity of macroinvertebrate communities (Piscart et al. 2005).

Stage 3: Binche – Épernay

The peloton left Belgium today and headed south into the Champagne region of France. Along the way they traversed many rivers like the Aisne, the Vesle and the Marne. These rivers are connected by an extensive canal network that ultimately stretches all the way to the Rhine at Strasbourg. Almost all of these canals are at least 5.2 meters wide because of an aggressive public works minister of the Third Republic, Charles de Freycinet.


A map of French canals prepared during the lead up to the Freycinet Plan. (source).

Freycinet was the child of noted explorers Louis and Rose de Freycinet, who had circumnavigated the world on the Uranie. He was given the best technical education around at the École polytechnique and entered the Corps des Mines, a prestigious technical branch of the French civil service. By 1877, he was the Minister for Public Works, and it was here that he and his Republican colleagues devised a plan to revolutionize the infrastructure of France. They intended to spend around 4.5 billion francs on railways, canals and ports throughout the country.


Charles de Freycinet. (source)

The canal improvements focused on standardizing the waterways to what came to be called the Freycinet gauge. Canals would be widened to 5.2 meters, and all locks had to be 39 meters long. These dimensions fit a 300 ton Belgian barge called the péniche, and they still form Class I of the EU’s Classification of Inland Waterways.


A péniche on the Saône river. (source: G CMP, CC-BY-SA)

The Freycinet Plan was not popular in all quarters. Emile Marché, speaking before the Société des ingénieurs civils de France in 1883, worried that the engineers had “impoverished the country by wanting to enrich it, by building in our ports magnificent basins where ships do not enter, canals without boats, railroads without travellers…” and lamented the ballooning costs of the project. The waterway improvements eventually fizzled out as costs spiked, and it became increasingly clear that canals, especially the relatively small Freycinet gauge ones, were not competitive with railroads.

Stage 2: Brussels Palais Royal – Brussels Atomium

With the exception of a crossing of the Willebroek Canal, which continues the Charleroi Canal on to Antwerp, and some artificial lakes such as those in the Bois de la Cambre and the Royal Estate at Laeken, there was very little water on display during today’s team time trial. However, the name “Brussels” comes from the Old Dutch for “Home on the Marsh.” What marsh does that refer to, and where did it go?

A map of Brussels in 1837. (source)

Brussels was founded around a chapel built by Saint Gaugericus on an island in the Senne River. The Senne River was never a great river, dwarfed in Belgium by the Meuse and the Scheldt. Navigation on the Senne was difficult enough that the Willebroek Canal was built as early as 1561, and that canal was expanded and connected to the Charleroi Canal in the 1830s, becoming a major transportation corridor from the rich coalfields of the Sambre Valley to the port of Antwerp. The Senne, meanwhile, became a dumping ground for the refuse of the city.

The quality of the Senne was so degraded by the mid-19th century that historian John Lothrop Motley, writing in an 1853 letter to Oliver Wendell Holmes, Sr., described it as “the most nauseous little river in the world.” Baudelaire was even more forthright, calling it “a dung that flows.”

Slums built out over the Senne. (source)

The recently independent Belgians decided to do something about the cesspool that was their capital’s river. In the 1860s Mayor Jules Anspach led efforts to cover the river. The Senne was diverted into underground channels, and by 1873, the Senne had disappeared from the inner city of Brussels. Anspach used the opportunity to implement his own form of Hausmannization, replacing the river with massive boulevards, including one named after himself. The Brussels Stock Exchange building, designed by Léon Suys, who also drew up the plans for the covering, is one of the more important buildings constructed during the urban renewal.

The Brussels Stock Exchange. (source)

In the early 20th century, the river was diverted out of downtown tunnels to run around the city, and the old tunnels under the boulevards became subway tunnels and storm drains. It was not until 2007 that water treatment plants were finally constructed on the Senne, to purify the water that eventually makes it to the Scheldt.