Starting point: Southern entrance - Rue Duburcq-Clément. Climb the stairs to a sign "Sentiers des Meuliers". Turn left and make your way to the information board "transporteur aérien". Behind you, a square where monolithic and "English-style" millstones are exhibited. Continue the path to the sign "la découverte", on your right, a huge gritstone rock. Follow the path to "Colorado". Turn right and walk down the wooden steps along the path's loop. Turn right and continue until you reach the explanations on the theme "l'eau et la boue". Continue along the dirt track until you see the sign "Sentier des Meuliers" again. Walk down to the car park.
Information: dogs are authorised on a lead - Remove your waste - Camping and campfires are forbidden.
A fragile and evolving natural environment. La Barre wood is marked by tree varieties which have naturally colonised this environment transformed by humans during its use for quarrying millstones. Therefore, trees characteristic of these types of changes can be found there, such as black locust mainly in the northern part of the wood, and a few less common species, such as the red elderberry. In the rest of the sector, there is a varied selection of trees with a strong presence of sessile oak and penduculate oak, as well as ash, wild cherry, lime, maple, hornbeam, hazel and, more occasionally, beech and silver birch. Near the roads, the strong light favours the development of shrubs, such as hawthorn, blackthorn, and European spindle. The woods offer 165 plant species and a wide range of spring plants: bluebells, lesser celandine, yellow anemone, wood anemone. The exposed lime sections of the slope provide a home to early purple orchids.
It is also possible to see mammals there, such as roe deer, boar, marten, and the more discreet badger. In the marshes, it is also possible to find a species which is protected in France: the fire salamander. The badger lives in territorial groups and tends to be nocturnal, not being very well adapted to hunting prey, it feeds on worms, insects, plants and sometimes, small mammals. Its prints, with a clear heel print and five toes, is large and ends with long claws. Their trails are wider than those of the fox and are similar to paths which radiate out around the set. The set is generally used from generation to generation and is often extended; its entries can be recognised by the volume of surrounding debris, often with several cubic metres of earth and stones.
The wood's ecological diversity also offers plants which are characteristic of wetlands: bulrush, sedge, horsetail. The project to develop the site initiated by the department has offered the opportunity to restore a series of small marshes which provide a home for salamander. The fire salamander measures 10 to 20 cm and has large venomous glands, and is glossy black with yellow spots. It secretes a toxic product which may cause rashes. Most of the time, it can be found in the forest, swims only very rarely but needs wetlands in order to lay its larva in the water. It is ovoviparous. The ponds are fragile environments, please respect the tranquillity of their inhabitants.
At the heart of the Paris Basin: A genuine interest for what we now call geology emerged in the eighteenth century. Stratigraphy, the science that aims to describe geological layers, was born in the Paris Basin with the work of Georges Cuvier and Alexandre Brongniart. Jean-Etienne Guettard, physician and botanist to the Duke of Orleans (1715-1780), was the first to identify the Puys d'Auvergne as extinct volcanoes and the pioneer of mineralogical mapping. The very first geological map known is his mineralogical map, which shows the nature and location of the grounds that run through France and England. In 1758, he presents before the Royal Academy of Sciences a memoir on the millstone based on his observations in the quarries of Houlbec (Eure) and La Ferté-sous-Jouarre (Seine-et-Marne). He foresees the potential role of rainwater weathering in the formation of millstone deposits. In 1811, publication by Georges Cuvier and Alexandre Brongniart of their memoir "Essay on mineralogical geography around Paris", which lists ten "types of grounds" represented in a geognostic map. With its colour ranges showing the outcrop of the various grounds, it is the prototype of modern geological maps. Brongniart visits the quarries of La Ferté-sous-Jouarre and gives a remarkable description. The Paris Basin is one of the largest sedimentary basins in Europe. In this vast basin surrounded by crystalline massifs, seawater intrusions and continental episodes have succeeded each other for 220 million years. The Marne valley intersects an immutable overlay of strata that illustrate the Tertiary. 45 million years ago, the region was occupied by the sea. The climate is hot. Coarse limestones form at the bottom of a calm sea. Then the deposit of marl announces a containment trend and the associated coastal landscapes. 42 million years ago, after a brief emersion, the Auversian Sea leaves behind sands and sandstones. Alternating stages of emersion and minor marine recurrences take place where the marine domain is progressively isolated. A series of limestones and lacustrine-lagoonal marls establishes itself. During the Upper Eocene, a very brief marine transgression is soon followed by the establishment of a brackish environment where evaporitic conditions promote the formation of gypsum. 34 million years ago, during the Oligocene, the shallow basin sees a new marino-lagoonal episode and the deposition of clay sediments. Then again comes a lacustrine regime where the deposit of Brie limestone forms. A final and significant marine transgression, the Stampian Sea, ends this long sedimentary series with the deposition of Fontainebleau sands. For 25 million years, the region has been continental. Erosion causes the removal of Stampian sands and the clearing of the Brie and Multien plateaus. The current landscape is emerging.
The millstone: The millstone is a fine-grained siliceous rock, cellular and cavernous. It does not form a continuous bed and appears only in scattered blocks within a sandy-clay formation called Millstone clay. This is a surface geological formation linked to a limestone weathering phenomenon. The process that led to its formation is called "meulerization". In the early nineteenth century, the millstone is an important topic of debate within the brand new French Geological Society. The greatest thinkers in emerging geology, Cuvier, Brongniart, Prévot, Dufrenoy and d'Orbigny describe its deposits and try to understand the mechanism of genesis: Hot springs inspired by the geysers of Iceland, "silica seepage in the sea floor", residue of a siliceous limestone... are all solutions that oppose the "weathering" hypothesis suggested by Guettard and taken up by Dolfus in 1885: "atmospheric waters seeping into the Brie limestone dissolve it slowly, then migrate and deposit the silica they are loaded with in the lower parts." Based on that principle, Gosselet introduced the term "meulerization" in 1896. In the twentieth century, geomorphologist Cholley associates meulerization to tropical paleoclimatic conditions (1938). Millstone deposits would be interspersed in ancient erosion surfaces. The last quarter of the twentieth century is marked by the fundamental role of geologists Grisoni and Menillet. In 1988, the latter interprets millstone deposits as products of desilicification and silicification in his karsts and determines precisely the age and conditions of their establishment.
An alchemy of time: Millstone clay can only be found as cover of the plateaus without ever running deep into sedimentary layers. It is observed on the surface of the Brie, Beauce or Hurepoix plateaus in connection with Brie or Beauce limestones. 35 million years ago: The Brie limestone forms through sedimentation in lagoons and lakes. 30 million years ago: The Stampian Sea floods the entire region and deposits a thick layer of siliceous sand. 27 million years ago: The Stampian Sea retreats from the Paris Basin for good, leaving behind several tens of meters of sand that cover the limestone. The region has become continental and is subjected to erosion for 20 million years; the sands are weathered by the rain and removed by the wind, revealing limestone outcrops in places. 2 million years ago: The limestone surface is almost completely laid bare and a plateau emerges, where the wind deposits clayey silt. Limestone is in turn subjected to erosion, depressions form on its surface, soon occupied by a residual sandy clay fill. Rainwater seeps into these basins, sandy clay is leached, sand grains undergo dissolution. Free silica (sio2) is transported by water and will become fixed further in the voids of the limestone, masses of siliceous rocks form. These are the millstone deposits.
La Barre quarries: Since the Antiquity, siliceous sandstones and limestones have been used in Brie to shape millstones. It was in La Ferté-sous-Jouarre that a hard and alveolar variety of stone was noticed, which is suitable for their making. In the sixteenth century, quarries called "meulières" or "molières" multiply there, together with millstone maker workshops. The hill of Tarterel, on the left bank of the Marne river, is one of the largest millstone centres in La Ferté-sous-Jouarre. While on the right bank, the quarries of Justice and Bois de la Barre supplied various grades of stone. A layer called "bastard sandstone" of little interest was covering a hard, blue-veined stone, more conducive to the making of millstones. In the early nineteenth century, the millstone activity in La Ferté is becoming industrialized and the quarries of Bois de la Barre are expanding. The making of millstones from a single block, called "monolith", is abandoned and turns towards the production of so-called "English" millstones. This innovation introduces a method for the assembly of several pieces: the tiles, set around a central piece: the guide bearing. In 1837, the companies Gaillard, Petit & Halbou, Vieille-Gatelier founded the Société du Bois de la Barre.
From millstones to suburban house: In 1881, establishment of the Société Générale Meulière at the foot of the hill of La Barre. Its large workshops are located near the quarries, between the railway and the Marne river, and a harbour and a train station are attached to it. Around 1900, the millstone trade is on the decline. The quarries of La Barre go through one final reconversion thanks to the extraction of stone intended for the building industry. This is the time for the growth of the suburbs of Paris and their "millstone" houses. But another use is less visible: The works of the new Paris underground! Millstone rubble are conveyed from the quarries to the bank of the Marne river thanks to an ingenious aerial carrier, much like a ropeway. From there, barges carry the stone to the capital.
The millstone industry of La Ferté: After the French Revolution of 1789, the egalitarian legislation encourages craftsmen to create societies. Many millstone makers come together to exploit the quarries. In 1853, there were 23 companies employing 1381 workers in La Ferté-sous-Jouarre. Gueuvin-Bouchon alone, the biggest of them, employs between 500 and 600 workers. The annual output reached 1000 to 1200 millstones and 80 to 100,000 tiles. Meanwhile, the Roger firm produces 600 millstones per year thanks to the work of more than 300 workers. The millstones of La Ferté-sous-Jouarre benefit from a good reputation. They are exported throughout Europe, but also in America, Australia... Around 1860, large industrial mills appear. Very modern, they no longer use the ancient millstones but a new milling system fitted with a cylinder made of china. Hit hard by the competition, many small mills close. The millstone trade collapses slowly but inexorably. In 1880, a wave of panic swept across La Ferté-sous-Jouarre: it is the end of position revenues for the industrialists of la Ferté. In 1881, out of the crisis arises the Société Générale Meulière. It is formed by the merging of nine companies, the biggest of which are Roger & Fils and the Société du Bois de la Barre. In 1910, a long strike, soon followed by the "Great War", undermines this pillar of the millstone industry. After the liberation, in a context of harsh competition, the SGM tries to modernise its activity; it manufactures sophisticated equipment for the sectors of agriculture and milling. Despite these efforts, it does not recover from the Second World War.
In the country of "blue hands": When working the stone, flint flakes or pigette (pickaxe of the quarry worker) metal splinters would lodge themselves under the skin, which would then turn a blue colour, hence the nickname "men with blue hands and faces." The fine dust produced by the cutting of "tiles" enters the lungs of millstone makers. Tuberculosis and silicosis lead to a high mortality rate. Workshops are installed under well-ventilated sheds in an attempt to preserve the workers. The SGM, while maintaining the production of traditional millstones, tries to adapt to the demands of the new milling industry. Its workshops manufacture roller mills, screeners, cleaners... And yet, the industries of La Ferté never ceased to promote the millstone. The SGM and the company Gueuvin-Bouchon-Dupety-Orsel search for new deposits: They operate quarries and open branches in Épernon (Eure).
Discovering the Bois de la Barre: The Marne river cut through the sedimentary Brie plateau, thus revealing a set of geological formations on the foothills of the valley. One of them, the millstone clay, covers the plateaus and slopes. The millstone has been exploited since the Antiquity, by craftsmen first, then industrially, and reached its peak activity in the nineteenth century. This exploitation was the wealth of La Ferté-sous-Jouarre, thanks to the quality of its stones, particularly those intended for the manufacture of millstones. After the exploitation closed down, nature reclaimed its rights. It is in this environment that the Conseil Général de Seine-et-Marne invites you to discover the remains of La Ferté's industrial heritage through an educational trail.