Tonnerre Patrimoine

Dionne Pit

Fosse Dionne, from the Old French Fons Divina (divine spring), is a Vaucluse spring permanently fed by seepage from the limestone plateaus above and by the flow of one or more rivers. Even in times of drought, the flow remains constant at around 100 liters per second.

Dye tests have shown that the Laignes River, which flows into a chasm 40 km to the east, is only slightly present in the water of the Fosse Dionne, and that over 80% of the dye poured into the underground river near Athée was also found there. However, it cannot be said that the latter river alone feeds the Tonnerroise spring.

Explorations

And it's this aura of mystery that has always fuelled legends and exploration ventures. From the end of the 19th century until 1908, scuba dives were carried out, but they didn't take us beyond the basin from which the spring emerges. It wasn't until technical progress and a new dive in 1962 that the -28 metre mark was reached. The following year, the same team reassembled and continued the expedition. But the expedition went badly wrong and two divers were killed. Further attempts were made, but the Le Guen brothers were responsible for the most complete exploration to 360 meters from the entrance. It lasted over 3 hours, including 1h40 in decompression stops. The main difficulty of this operation lay in the fact that the natural conduit of the Fosse is "saw-toothed", forcing the divers to chop up their advance. Ten years later, P. Jolivet extended the exploration and reached -70 meters (370 meters from the entrance). It's the ultimate record, which stands to this day.
There have been many other visits since then, but the main aim has been to prove the ancient use of the spring. In 1996, after another fatal accident, the town council decided to ban all diving.
Today, even taking into account the existing equipment, we can say that the human limits to the discovery of the spring have been reached. Firstly, because of the famous decompression stops, which require the diver to take numerous breaks and use a special gas mixture. To go further, in theory, he would have to carry greater reserves, but these would not allow him to cross the many narrow passages. To this main constraint, we can add others. The divers' movements, for example, stir up large quantities of clay, clouding the water and reducing visibility. In some places, you have to pass through areas where the walls are unstable and close to collapse. Last but not least, you have to defy the water's current, which is all the more dangerous at the narrows. The Fosse Dionne has not yet revealed all its secrets.

The legends of Fosse Dionne

Historically speaking, the spring was slow to be exploited because the surrounding area was swampy and unhealthy. At the time, it aroused as much fascination as it did fear in the people of Tonner, as evidenced by the terrible legends that have endured to this day.

Saint-Jean l'Abbé and the Basilisk

The oldest, or at least the most ancient, dates back to the 5th or 6th century AD. It refers to a snake, the basilisk, which terrorizes the inhabitants of Tonnerre. When it emerges from its hiding place, the snake kills anyone in the vicinity by the sheer force of its gaze.
Saint Jean l'Aumonier, secluded in a nearby hermitage, is alerted to the affair. He decided to confront the beast and, equipped with a shovel and pickaxe, went to the spot where the snake had last been seen. He finds its lair and digs to dislodge it. While he was digging, water invaded the cavity, overflowing and flowing in an uninterrupted stream down the Armançon.
The snake was drowned thanks to the efforts of the holy man who, after a short retreat in Tonner, retired to found a community in the desert of Réôme (later named Moutiers-Saint-Jean), where he died at the respectable age of 120, in 545!

The Devil's Pennies

There's another, slightly later story. In July 700, a little boy named Pierre was walking near the spring. That's when he heard a cavalcade. Looking for the source of the noise, he saw a rider coming towards him, dressed in clothes as dark as his horse's, and dominated by a red plume.
The rider stopped at his side and asked where he could get his horse to drink; Pierre pointed to the Fosse Dionne. The knight immediately heads for it and, in his rush, drops a well-filled purse. The boy seizes it, and gazes in wonder at the glittering pennies. After a quick glance around, he stuffs the coins into his pocket and returns home. The next day is a feast day in Tonnerre.
Pierre strolls briskly through the fairground, playing the coins between his fingers. On a whim, he buys a cage full of fledglings, but they mysteriously manage to escape. Although saddened, the boy continues on his way and gets caught up in the festive atmosphere of the town. He buys a bouquet for his mother, but the flowers wither immediately on contact with his hand. A little further on, he deposits a coin in the palm of a blind man begging for alms, but the latter refuses it.
On the way home, Pierre meets up with some friends and together they enjoy the cakes and sweets bought with the rider's money. Some time later, however, they are all taken by violent stomach aches that nothing can relieve. Added to this are uncontrollable fits of demonic laughter. Pained, ill and remorseful, Pierre decides to find the mysterious stranger and return his property. But in front of the Fosse Dionne, he obviously finds no one.
In a gesture of despair, he throws the coins into the water and is about to throw himself in when a bishop, Saint Pallade, stops him. The child, crying, tells him the whole story. The man consoles him and grants him his forgiveness. Then, knowing that the child's terrible pain was caused by the diabolical coins, he throws his cloak into the clear water of the spring, to cover the purse lying at the bottom.
The dark horseman, lurking in the thicket, had observed the scene and, above all, the failure of his plan. Mad with rage, he sprang from his hiding place and furiously threw his mount into the spring. The water bubbled for a long moment, then gradually subsided. The bishop and the child probed the water for the rider, only to find that the sandy bottom had given way to a gaping, dark hole through which the man, who was none other than the Devil, had escaped.

The Virgin with the Emerald Cloak

The last legend is just as disturbing, but closer to home, since the Bourbérault district had already been built. On a moonless night, a young girl hurries home. Her shoes hit the pavement in a hurry, and she probes the surrounding streets and alleyways with worried eyes. As she nears what used to be a swamp, she senses a presence at her back. Whether she speeds up or slows down, she hears her pursuer doing the same.
Seized by fear, she starts to run as fast as she can, but the Devil behind her - for it is Devil - runs much faster and catches up with her in a few strides. She feels his quick breath on the back of her neck and, in a fit of desperation, begs the Virgin Mary for help. Immediately, the night seems to be torn apart, giving way to a Lady of striking beauty, dressed in an emerald robe and cape. The latter, in order to shield the young girl from her assailant, lays her cloak on the ground, which is transformed into a vast circular pool of transparent water, the Fosse Dionne, into which she throws herself and the girl.
These ancient legends, handed down from generation to generation, and in which Evil and Good do battle, reflect first and foremost an ancestral fear of the Tonnerrois people towards their source. The reason is simple: for centuries, the area around the spring was damp and marshy, ideal conditions for the development of malaria. And Tonnerre is not an isolated case: many legends featuring the Basilisk actually deal with this disease, which they portray as a malignant snake. The paradox comes from the fact that it was once worshipped, as evidenced by its name: Source Divine.
It was probably not until the 17th century that the spring was developed. In 1758, the Chevalier d'Éon's father had the washhouse built as we know it today, comprising a circular basin with emerald-colored water 14 meters in diameter, surrounded by a trough in which the washerwomen washed their clothes, and a semicircular lean-to with tall chimneys to heat the water. Washing days were an opportunity for the washerwomen to exchange news from the neighborhoods, among other things. And some prying ears, notably those of curious children, liked to follow these conversations thanks to the chimney flues, the tops of which overlooked the street above the washhouse.