Exploitation from the 1st until 12th century:primitive exploitation is done in the most instinctive way. Chunks of rocks lying on the ground are gathered and re-used, and are sometimes rudimentarily cut. To continue meeting the need in stones, the compact stone banks flushing with the ground are then exploited, taking advantage of the stone's natural faults whenever possible to facilitate its extraction. As soon as the 1st century C.E, Romans are exploiting the Bièvre valley. Then trenches are dug deeper and deeper into the stone deposit to extract more stone. A very old circular open quarry can be found in the heart of Paris, which was later transformed into an amphitheatre: Les arènes de Lutèce (Lutece's arenas). From antiquity until the middle age, the open quarry exploitation method requires simple resources but a lot of manpower to be undertaken.

Limestone is easy to extract and offers a fine grain stone very well adapted to constructions; but the extraction trenches prove to be very costly, their exploitation surface becomes quickly pervasive yet does not make it possible to exploit the deposit in its entirety. This deposit is made of stone "beds" of different quality, stacked one on top of the other. They will be exploited in an anarchical way, with no distinction made between the different stone layers until the 12nd century. These stones are used to build monuments, which will later suffer from the lack of knowledge of their builders, being degraded by air and bad weather. Gallo-roman constructions will be taken appart, their best blocks are reused, and extraction will continue non-stop, progressively heeding the various qualities found in the different limestone layers to select those that will offer the best resistances in order to provide for the needs of this important city that will soon become a capital city.

During the 15th century, this underground exploitation method will spread through the Paris suburbs in the surrounding plains of Montsouris and Montrouge. Small new quarries flourish on the surface and underground. New techniques allow to extract stones of better quality, in greater quantities. By spreading far from the quarries entrances, these underground networks will need to be fitted up with vertical wells equiped with lifting wheels to avoid an arduous transportation to the surface. These quarry winches (or squirrel wheel crane) are moved by a worker climbing the ladder rungs and allow to lift blocks every time bigger extracted from the deposit. Sometimes draught animals are used to activate them. In some quarries, galleries are over-dug and enlarged to allow chariots, hauled by oxes or horses, to go around in those networks more and more sophisticated.

Limestone exploitation during the 16th and 17th centuries : the development of towns, then of cities, will progressively increase the population and the number of monuments. Buildings will need more and more stones, those from Paris and its region unable to provide the huge needs of the region, be it in terms of quality or of quantity. The stonemasons confraternities now tidily distinguish every deposit and every stone quality to extract the best stones: the "Liais franc", a very hard limestone with a regular grain that will make them rich until the 19th century. The stone trade is at the time flourishing, and will soon spread over our borders. Valuable freight pass through all Europe to dispatch the "Liais" but also to bring back other stone qualities sought after in France, in particular coming from Italy, known for its famed marbles and dark, veined and colorful limestone: the Carrara marble. 

These huge deposits are still far from being fully exploited: the price of a Carreau (stone tile cut lengthwise) or of a Parpaing (stone parpen, cut widthwise) reaches peaks. The untouched stone pillars created with the "room and pillar" mining method are a financial loss in the deposit, that must be exploited to the maximum. During the 18th century, an italian technique will again improve the exploitation output. Until then, only half of the deposit could be used. By "importing" the exploitation method using "hagues et bourrage", the output will exceed 90%: all the empty spaces will be filled (the bourrage) with earth or low-cost extraction wastes that will be held by walls of interlocked stones:  the Hagues. At regular intervals, many pillars are placed, directly sitting on the rock and composed of cubic stones piled one on top of another to reach the quarry ceiling, creating a very solid structure.

Today note can still be taken that, comparingly, consolidation by the "hague et bourrage" technique is not subject to pressures susceptible of burst the rock of a plain-stone pillar or a modern pillar. Being quit of the stone's characteristic rigidity, it imparts a relative flexibility that allows it to pack down and to distort, holding the quarry ceiling on a great surface.

In case of collapsing, it continues to hold the rock masses without weakening the surrounding parts via the domino effect. These techniques will be used by the Inspection Générale des Carrières from the 18th until the 20th century, and are still acknowledged as durable and efficient consolidation works, less prone to suffer from the effect of time than hardened consolidations, or stone or concrete pillars. Their reach is lesser though; both systems complete each other very well for consolidation work.

The empty spaces are exclusively destined to the intensive production of limestone blocks. Contractors will pay little attention to the future of their deposit, for which they pay a temporary concession that must be made the more profitable possible. Quarrymen are well paid, in comparison of farmers or regular workers. This job, although hard, allows to live throughout all year, with no interruptions due to seasons, bad weather or rain. This explains the great inflow of workforce. The quarry worker is paid with piece wages, which means he cuts blocks and take them back to the surface to be paid by the contractor who will take care of transporting and selling them. More than often a parallel market starts, outside of concessions. Workers, sometimes associated to make their task easier, work for themselves and sell a few extra blocks; the various consessions cohabit together, sometimes confront eachother or become united. This underground world is ruled by rules of its own of sharing, setting of scores and corruption, sometimes participating in local trafficking or smuggling under Paris.

To perform this work, contractors hire stout men, often farmers coming from the north, men from Normandy or Britain, who find in this work a complementary - sometimes principal - income, in exchange of tiring and extremely dangerous work. Traditionnally, quarrymen are hired at dusk and are paid at the end of the day. Each block will receive the mark of the worker - or workers - who will have taken it out of the stone bed and cut it grossly. This block will be transported to the quarry entry or to the nearest hauling well. Work is done in a crepuscular darkness, dimly lit by oil lamps fed  by various sorts of greasy substances. Contractors sometimes provide fuel, carefully deducing it from the workers' salaries. These lights barely provide the light of a candle, but last longer and cost less than wax. There are nonetheless prone to create accidents, provoking by lack of lighting various tragedies, notably during during the extraction and transport of those blocks weighting several tons across the quarry.   Illustration opposite: calculations of masonry left by the workmen of the igc

There are many victims among quarrymen; falls into badly fitted wells, only equiped with wooden ladders, and score settings between workers are part of the risks in this work. Of all the dangers, the most insidious one is without a doubt the "quarryman blindness", also affecting mine workers, which is caused by the poor lightning these workers are using. Year after year, work in the darkness irredeemably damages the sight, leaving those with a life expectancy greater than 30 years completely blind.

The beliefs and superstitions of the quarrymen are numerous. To insure their protection, they entrust their fate to saint protectors, of which traces still can be found. A few chapels, formerly containing statues of "Notre Dame de Dessoubs Terre" (Our Lady from Under Ground), of Saint Vincent de Paul or Saint Clément (also symbolized by a ship anchor) still subsist, particularly on the Rue Saint Jacques axis. They consist of round-shouldered, polychrome niches, often painted like churches with vivid blue and sanguine colors. These beliefs help these workers in their harduous tasks, as much as wine and liquor, used as stimulants and anesthetics for the labour of hercules they have to accomplish: sawing, rock cutting, hauling and transporting blocks sometimes reaching 10 or 20 tons.

The work rythm goes at high pace, the worker (see hierarchy hereunder) works seven days a week, but can rest one day every five weeks, the day following the payment of the monthly salary (this day is always a sunday). These conditions don't seem to be excessive for the time and the workers make do with their "inducements" granted by their employers, who rarely have troubles with their employees, even if those are reknowned for their fierce temper. The best workers and foremans are sometimes allowed to cultivate the lands above the exploitation... if they find the time. out of work hours, the quarry worker is often too tired to do any domestic task, and it's his wife who takes care of the household. The employer can increase his income by providing housing barracks for his employees and deducing, in addition to the general expenses, the lodging he gives to his employees, who in turn become completely dependant on him. In return, the employer guarantees them work, housing and a yearly income which will allow the luckiest among them to feed their children until they are able to take their place.

The stone bank exploitation technique during the golden age of the "master quarrymen" from the 16th until 19th century roughly stayed the same. First, low galleries are dug, from which the first blocks are extracted. In the quarry, well defined work areas are fitted up: the area where the stone will be exploited (the workshop) and the area where it is extracted and that will first be consolidated with pillars then with the "hagues et bourrage" technique described in the precedent chapter.

Souchevage technique in an underground quarry

The Souchevage technique-  Illustrations  © explographies.com

The workshop presents the cutting front (Front de taille), which is the massive limestone deposit where the blocs are extracted from. Blocks are separated by natural separations (geological layers) where each stone quality appears separated by lines, presenting various matters of various density. One of these layers, very soft, is called a “ Souchet ” gives its name to the “Souchevage” technique which consists in digging horizontally between these layers (1). If this term sounds pretty abstract, one can compare it to a big wooden plank that one will cut following the horizontal lines of the wood, then cut it vertically to make smaller plancks.  

The souchevéed then déferméed block will detach itself from the cutting front under its own weight. It will then be grossly cut then transported on wood logs (3) and hauled by chariots to the quarry entrance or extraction well  (4)  where it will be dried and cut into rubble stones by the stonemasons. This is how the underground quarry exploitation takes place: galleries will be dug progressively, rock will be extracted and the empty spaces left will be consolidated to go further into the underground depths.

The last suburb quarries will fade out progressively sometimes recycled in mushroom farms where the white Paris mushroom will be cultivated on the old quarries exploitation embankments. A few former quarrymen will thus find a way to change their profession in these mushroom farms. In 1939, Bagneux closed the very last underground quarry still exploited in the Ile-de-France region.

Gypsum and limestone under Paris :  The underground quarries of Paris have mostly been exploited for their limestone deposits. They represent 770ha of the city’s area, to which 150ha of gypsum quarries can be added. The layout of these exploitations is clearly delimited in the north tier of Paris, leaving the limestone area to the south. This gypsum (called ludian gypsum) is a geological formation, with a completely different composition from the limestone (called lutetian limestone, after its era of formation)

To explain is particular localization in the north of Paris, one must go back to the circumstances of its formation: Without going into technical details, one can say that a long time ago (approx. 50 million years ago) just before the start of limestone formation, a “small” crust fold raised all the south part of the Parisian basin. The sea then covered several times this region, leaving a lot of particles that agglomerated themselves during 15 million years to create the whole limestone bank.

How is gypsum formed ? Immediately after that time, the sea retreated and left behind basins (small lagunas) in which fragile gypsum particles formed, crystallized and accumulated themselves during approximately 10 million years. The successive deposits from this sea coming from the north were then stopped by this geological fold (the Ypresian fold), forming a sort of dam on the upper plateau south of Paris. This is how we obtained subsoil composed of very shallow, high gypsum concentration to the north. To the south, with no covering layers, it’s limestone that can be found almost at ground level. This shallow depth (between 20 and 30m) made it easier to exploit those rocks.

Gypsum’s particularities : Compared to the limestone, gypsum has the particularity to “dissolve” when in contact with water. One will then ask how such heights of rocks are still present yet  and weren’t just simply eroded a few years after being formed. That was the case in a few places: water (sea water, rain infiltration) made everything disappear. What is left of those gypsum deposits only exists because of a thick layer of clay formed on top of it right after, which protected these soluble crystals from infiltrations. This small geological chapter will allow us to better understand immediate applications of gypsum: it dissolves when in contact with water, but also makes an excellent “cement”. This is how some gypsum deposits will naturally become plaster exploitations.

Gypsum exploitation mainly consisted in using the crystals to transform them to obtain a powder which would then serve as mortar. The upper part of the 4 gypsum deposits on the map will be used. On the side drawing is shown the Butte Montmartre and the Sacré Coeur church. Right under, in the subsoil, are the church’s foundations, stretching out deeply into the soil, at almost 40m under the monument’s level, sustained by anchored pillars put into the gypsum deposit, that will of course not be exploited under the church. Those big gypsum deposits will be dug in the same way limestone is, to extract the material. This exploitation will simply be done with greater depths, given the size of the available deposits. Each layer of these 4 deposits representing an height of 50m will receive a colourful name, given by the quarrymen to differenciate them: les fleurs (the flowers), le gros cul (the big ass), les foies de cochon (pig livers), les pots à beurre (butter pot) ou les crottes d’anes (donkey droppings)…

This very old plaster use dates back to the romans, who used the flushing deposits to make certain mortars. In the 18th and 19th century it will undergo an industrialization process that will transform the Montmartre, and buttes-Chaumonts quarries, and soon those in the north of Paris (Cormeilles, Triel, Livry, Gagny…) in gigantic plaster processing plants that will provide 2/3 of the national production, leading to mortar exportations for the United States (giving their new name to the Montmartre quarries, the “America quarries” – les carrières d’Amérique). The deposit will be exploited using explosives; the upper and lower stone banks will then be extracted using manual tools, creating very regular architectures with high, round-shouldered, almost triangular shapes typical from gypsum quarries. The top of the superior gypsum mass will be consolidated with wood timbers, forced inbetween the different cutting fronts, forming some sort of woodwork made with joggled beams.

The mineral will then have to be taken out of the quarry, using ox or horses teams, or pushed on wagons on rails. In the nearby plaster processing plants, blocs are crushed, grounded  then heated at 150°C in furnaces to obtain a whitish powder that will be used pure or sometimes slightly mixed with starsh, or with some retardants for slow drying mortars. Those quarries thus present only one problem, precisely this capability to dissolve into the water used to produce the mortars. Only a small crack or a small water infiltration in the clay layer forming a protective blanket over the gypsum would be enough to transform all the empty spaces left by the quarrymen into a card castle.

The end of the quarries exploitation : At the beginning of the 19th century, the intensive exploitation of the quarries will stop, provoked by the sudden appearance of concrete and the banning of stone extraction. These huge underground cavities will be abandoned from one day to the other by the quarrymen who had been living from this activity for several generations. This useless space will not stay unexploited for long, because a Parisian named Chambry will discover by luck the fortuitous link between the quarries existing in his neighbourhood and the spawning of mushrooms on horse manure…

The discovery of mushroom culture in Paris : Going rapidly from discovery to culture to commercial exploitation, customer demand will never cease to grow, in such a way that our entrepreneur had to buy new quarries in Paris (under the Rue de la Santé) to expand his exploitation, then in the suburbs, so promising as this activity seemed. He would soon be imitated by other operators who rapidly figured out they could make their fortune by growing the Paris mushroom. Those abandoned quarries will soon become as prized as they were at the time of quarrymen, and will be transformed into real underground culture fields. In the 40’s, the production reaches 40 to 50kg of mushrooms produced per year and per fathom. Given that there are around 20 exploitations around Paris, and that each exploitation contains around 20000 fathoms, the total production is around 2000 tons per year which is not inconsiderable.

The biotope of the Paris mushroom :  Mr Chambry’s secret is a completely natural recipe which results from air temperature and humidity, particularly constants in the quarries. The absence of light also favourishes this culture, who only works whimsically with daylight.  The environment being almost ideal, it’s only a matter to add the elements needed for the mushroom culture: it grows only on horse manure with a special quality and origin, after having undergone a particular fermentation.

Manure fermentation : To begin with, haystacks (called parquets) measuring 1,20m are made with manure near the mushroom farm.  This manure will ferment and release a certain heat. According to mushroom growers, if the haystacks are shorter, the manure won’t produce enough heat. If they are bigger, they will produce too much heat.  After three weeks of this alchemy, they hay obtained in the “parquets” will have undergone a chemical fermentation that will form the right component for mushroom culture. The parquets will then be transported into the mushroom farm through the former extraction wells equipped with simple ladders, or directly through the main quarry entrance.

Culture and alchemy of mushrooms : Once it is in the quarry, the manure will be spread evenly in a cord shape , measuring 40cm of height by 40cm of width. This operation is called “montage”. These dimensions were set with time and experience by the mushroom farmers. This  will let the manure ferment once again, to reach a temperature of 18 to 20°C. The second step is called the “lardage” (larding), consisting in sowing the haystacks by punching holes in them and introducing small wafers of dried manure (called “mises”) containing the with part of mushrooms, appearing in the shape of white filaments radiating through the “mises”

The seeds will constitute the most important investment for the mushroom grower, since he’s not cultivating them himself. The haystacks are then smoothed to become very regular in shape, and after waiting 20 days for the germs to take hold in the manure comes the next step: the “goptage”. It “only” consists to cover the haystacks with a 2cm layer of sand, using a wooden plate (“taloche”). This step will give the haystacks their white, smooth aspect. Later on, this sandy layer will be obtained by grinding the quarry stones in a very fine powder called Craon by the quarrymen.

Picking and maintenance of the mushroom farm : 4 to 8 weeks after the goptage, the mushrooms are ripe for picking. Cultures must be maintained in a humid atmosphere during the picking period by being watered regularly. To “breathe” (pick up oxygen and release carbon dioxide), mushrooms will need a constant airflow and a temperature of above 14 °C. Mushroom farmers are thus very watchful about air and ground temperature to maintain their cultures in an ideal atmosphere. To keep this warm and humid environment, some mushroom farmers install boilers atop the ventilation wells, in which they will keep a continuous fire that will help circulating the air in the quarry while keeping it warm.

Some others will move their cultures, depending on the season: close to the entrance during summer to let the warm air enter, and far into the quarry during winter to maintain it inside. At the end of every picking, called “volée”, the same operation will be renewed by sowing the haystacks anew. They can be reused for up to 5 “volées” before the manure becomes depleted of its nutrients and becomes unusable for culture. The manure is then gathered in a special cellar, and sold for market gardening. Its selling price allows to fully compensate its buying price.

After that, the quarry must be cleaned completely

before the whole process can be started again.

Set up of a quarry as a mushroom farm : Most of the area is dedicated to mushroom culture. Some rooms or cellars are kept to store away tools, replenish the stocks after the picking or keep the old manure until it is sold. At the entrance, like in any exploitation, an office along with a deliveries and weighting room can be found, and for the most important mushroom farms, even a lampisterie, which is a room to store carbide lamps. The quarry must be perfectly clean to avoid diseases which could propagate and contaminate all the haystacks at once. The walls are whitewashed from the ground and up to a height of 3 meters, by applying quicklime on them; this is the reason why many quarries have white walls, following upon the whitewashing.

Other foes are watched closely by the mushroom farmers: rats, mice and fieldmice destroying the cultures must be kept under constant surveillance. Insects too are attracted by the “whites”, like ladybugs, and flies who are avid consumers of young mushrooms. They are kept at bay by naphthalene powder, periodically spread around in the quarry; it is used with extreme care as not to affect the cultures. Last but not least, another unexpected “predator” is under a permanent ban to visit some mushroom farms: women :-). Be it an old belief or a well-founded experience (for which we will not look for an explanation), many mushroom farmers fear them: according to books from this time, they are an “irredeemable source of damages while being present, even temporarily, during certain periods of the month”.

Quarrymen and mushroom farms : We can conclude this small chapter on mushroom farms by emphasizing the fact that some mushroom farmers were quarrymen before starting this activity. Their experience in this field will be very useful to fully exploit the natural “resources” of the former gypsum and limestone quarries. By using rock powder (craon) or the embankment materials used to consolidate the quarries for the haystacks goptage, They will literally empty the consolidations done over the past decades to strengthen the galleries. Remnants of those consolidations can be often found by simply observing the presence of “pillar forests”, formerly sourrounded by Hagues containing the embankment materials, now completely isolated. This space emptying also has the advantage to free the ground area in order to extend the exploitation as much as possible.

This is also certainly thanks to their experience from working in the quarries that the former quarrymen will conserve the most important consolidations, keeping a certain logic in their disassembling, without putting the mushroom farm in danger.

The first months of this new service unfold amid a certain puzzlement. A new sequence of collapsings in 1776 adds up to the unease and the panic feelings of the Parisians who fear an unavoidable sequel of global collapsings, or the sinking of the whole city underground. True, a peak regarding danger has been reached, but this sequence of accidents is only a statistic. The “conseillers du Roy” (the king’s advisers) are nonetheless in uproar, and two distinct services will be created at the same time to try and solve the same issues, with a sure rivality contention feeling. The fight for power will soon turn into personal score settings, and will end with a decision disavowing the commission appointed by the finances service and led by M. Dupont, to the benefit of the Inspection des Carrières led by Mr. Charles Axel Guillaumot.

The quarries service must bring a quick and thorough answer to the problem. The immediate imperative will quickly determine the main lines of Guillaumot’s field of action and that of his successors.  Generalized collapsing has seen public roads, buildings, men and horses swallowed into a chasm previously unsuspected by the Parisians. For the gullible citizen living in this part of the city, more than even the catastrophe itself, the damages or the victims, it is the unspeakable terror of superstitions and old beliefs that resurfaces through this geological demonstration, easily blamed on the diabolical spirits living in the entrails of Earth; popular fears to which the king vows to bring order to. The quarries service will then receive four missions: inspect the underground voids, repair and consolidate them, proceed to the mapping of the ground and inform about the outcome of their studying.

The quarries’ inspection will begin by the damages done on the surface, more as a move to show presence on the ground and appease the Parisians than to fill the  voids created under the streets. This inspection mission will become paramount for the IdC that will need to know before all things the extent of the quarries, explore them and identify the various mechanisms and dangers that could affect the cities that jut out over them. This exploration will first start with small teams of sub-inspectors, engineers and surveyors under Guillaumot’s orders.

Geology in the 17th century is barely beginning and Guillaumot must, in order to spot danger, identify its causes and the mechanisms of an unknown world. Geological layers formation and the age of Earth will appear only a century later: this speaks about the difficulty of Guillemot’s work and that of his teams.

Consolidation and repair work : Before the enormity of the catastrophe, adapted works to fill up the crevices and build the streets again must be realized. Guillaumot will have to work under urgency in order to rapidly conceive an action plan to circumscribe the collapsing effects. The former finances commission, still very influential, watches closely all the undergoing operations, infuriated from having been put aside to the favour of the IdC.

New techniques will have to be worked out to consolidate the cave ins, through masonry and landfill, the comforting of former galleries, entrances, inspection stairs, teamwork organization and the choice of the most adapted materials. This titanic operation will have to be partly delegated to private contractors, paid for each task, to accomplish each work part done by dozens of specialized workers, paid by the subsidies granted by the king, then by the city of Paris, to the quarries service. Every work will be traced by a specific historized classification, which will allow the identification on carved stone slabs of the work nature, the realization date and the supervising inspector’s name.

Underground mapping : This mission, following the first two, will inevitably have to be done do give the service a reliable tool, showing in the most precisely possible manner all the inspected voids, all the works done and all the identified dangers or those that were circumscribed by consolidations. Entrances, drilling, wells, everything must accomplished by a few men who will write down, gather and reproduce all their handwritten notes to create the first underground maps of the city and its surroundings.

The most dangerous voids will be immediately filled, blocked or even collapsed with explosives after having been mapped as precisely as possible. All of Guillaumot’s engineers and surveyors team will accomplish this remarkable work in a record time. The maps will be modified, made more precise by their successors, to become 1/500th then 1/1000th scaled maps. They will give in 1855 the first “Paris city underground quarries atlas”, still used today in its modern form (the IGC maps).

The information mission entrusted by the king to report the actions taken and the service’s results to him, will later on be given to the administrations. It will stay a secondary mission as long as the inspections and  above all the most urgent works will stay incomplete in the quarries voids. After a century and a half, they will eventually be over. The IdC will soon become the “memory” of all the underpasses, equipped with archives showing the nature and the localization of the works done in the former underground exploitations.

This is today one of the most important mission of the modern IGC, which settled its activity on informing the general public, professionals and the administration about the dangers linked to the underground world. The general public will then be able to know before buying a house if it is built on “undermined” land. The research departments, architects or public work companies have the obligation to do so; Informations are given based on precise maps of the underpasses, and on the disaster prevention plans realized globally, particularly for the cities surrounding paris as well as in the immediate suburbs.

The first “natural” consolidations where realized by letting in place masses of limestone, to sustain the empty spaces remaining after the stone extraction. These pillars, usually of great size, continue to play they part and provide a good support of the subterranean cavities, as long as they are present in sufficient numbers. Some religious communities, mindful about the durability of their legacy, also realized works under their buildings’ foundations. The Carthusian order possessing 3 quarries under Paris realized a few arrangements of this sort, even if there aren’t many traces of it left. In the same manner, the 18th century consolidations done under the Val de Grâce church by François Mansart and those of the Paris observatory supervised by Perrault, consolidate even more the buildings standing on top of them. There’s no doubt those gigantic piece of works exceed the real needs, but continue to subsist through the centuries in a very remarkable way. They are big-sized brick work with low archs and massive pillars, craftily placed to sustain the whole quarry ceiling, forestalling that way the different geological accidents that could interfere with the masses’ equilibrium. At that time, the works will be regarded with less enthusiasm, given the enormous amount of money needed for their realization, especially those of Mansart who will lose his title of royal architect for having exceeded the credits granted for the entire construction of the church just with the underground works.

1-   worrying about details : The works of the IdC are inspired after older consolidations and the architectural progresses of this period. A remarkable attention for detail and for perfectly realized work will orchestrate in these underpasses a debauchery of financial means, of craftsmanship and engineering. These achievements surpass by far the aesthetical requirements of our time, if we consider them according to our actual appreciation criterias. The quality of stone work, the equipment of masonry and the audacity of the work can be compared on all aspects with the quality of surface work for the building of prestigious monuments. This astounding finishing quality are justified by the perfection mindset found in realisations from the 19th century, guaranteeing the strength and durability of the work.

2-   worrying about effectiveness : The most common void consolidation process includes the use of dirt, sand and rock extraction wastes coming from the quarries themselves. These considerable amounts of material often are brought from the surface, to fill the “unnecessary” voids (those with no practical use by the inspection), the “uncertain” voids (those that could evolve into a collapsing or with faults presenting safety risks) and the “searching” voids (galleries dug into the mass in places where subsoil composition is not known). These embankments constitute the main part of the former voids, filled with mechanically weak materials, but spread on important areas as to limit the impact of a possible subsidence while still continuing to support the quarry ceiling in an even manner.

Those embankments will be associated to other works made to reinforce them. For example, partitioning walls will be used, placed every 5 or 6 meters in filled galleries to reinforce their structure (symbolized on the maps by thin red lines forming hackings with beige background). In more important spaces, a “cobweb” architecture is used with small interlocked walls, interspersed with small spaces filled with material. This technique, which can be qualified as “reinforced landfill”, is quite similar to the “hagues et bourrage” technique used by the quarrymen then by the IdC, consisting in surrounding or containing these embankment masses with strongly interlocked dry stone walls. The “Hague” term supposedly has a Germanic etymology (from khag=enclosure, later used in the Saxon and Viking languages, before being frenchified) and designate several types of constructions, sometimes formed with regular lines, like a classical wall, or an entanglement of rocks assembled according to their shape in order to give them more stiffness. (hagus insertus)

These hagues are regularly interrupted with pillars, formed by blocks of massive stone measuring 60cm to 1m in width, piled one on top of the others then adjusted between the quarry ground and the quarry ceiling. Those pillars aren’t made through masonry and hold in place under their own weight, hence constituting a simple yet very effective work. Sometimes this kind of consolidation is used in a specific place to sustain the quarry ceiling tending to subside or crack.

Some of these pillars reach considerable heights, sometimes 10m and more implying the need, given the size of the blocks used, for scaffolding, pulleys and important lifting means to place the blocks weighting several tons so high. Other pillars, more modest, are simply used to sustain “low” galleries exerting a high pressure, and are constituted by smaller blocks but of equal resistance.

These basic constructions, commonly used by the quarrymen and the IdC workers, will be enriched by a multitude of built structures made of cut rubble stones assembled by different varieties of mortars and limes (Tournay lime, Senlis lime…) which harden with humidity. Those absorbent mortars hold extremely well in the humidity-saturated air and allow building walls that will sustain in priority the inspection galleries located under the streets, creating some kinds of doubles for ancient galleries, right under the front face of the buildings, to guarantee a better stability for the surface constructions. The major part will be in a perfect straight line, sometimes forming a diagonal rib on top or ending up in a corbel, distributing the load on several intercalated floors. In some other parts, liais slabs will be juxtaposed to form a double ceiling, maintaining and protecting the gallery from the quarry ceiling. This same method is used to build massive pillars of 1m50 of cross-section, adjoining galleries and interrupted with regular hagues holding embankments. Some of the walls end up in staggered rows, with no straight border, as if they were unfinished. They are in fact “opening walls” (murs d’ouverture) or “waiting stones” (pierres d’attente), left open-sided to allow the continuation of the work later on.

Ultimately, some truly exceptional works can be found, worthy of belonging to the most beautiful subterranean architectures of this time. Monumental stairs joining one or two different gallery levels, with perfectly set stones, straight or spiral staircase, sequences of arches of gothic inspiration and of course, collapsing consolidations in shapes of domes or massive arches, sometimes reaching up to 10m above the ground. Some of the cave ins are consolidated from the top and need some drilling to reach the summit. Mortar and aggregate material is then poured into it, filling all the spaces compartimentalized by masonry work to keep them in place. These works, sometimes invisible, are all indexed by carved stone slabs précising in this case F.R (Fontis remblayé, filled cave in) followed by an upward arrow (filled from the top down) or a downward arrow (filled from the bottom up).

The methods will of course evolve and continue to be used by the modern IGC, whose mission will more or less stay the same. At the end of 19^th century and beginning of the 20^th century, the collapse with explosives will be largely used. This method, notably used for the gypsum quarries for which the extent and dangerousity is measured, will reveal itself less drastic that what was previously thought. The method, often uncontrollable, leaves behind unreachable but potentially dangerous cavities.

The limits are quickly reached for this system completely at the opposite of the lasting work previously done, that moreover could be inspected regularly based on the maps annoted to keep a trace of each detail. After the explosive collapse the old location of the quarry remains, indeed filled but whose evolution will be unknown and will afterward prohibit any construction on the corresponding area.

Concrete and modern techniques will then be used more regularly afterwards. The IGC standardizes 1,40m cross-section pillars, reaching variable heights, depending of the size of the fractured area presenting a danger of collapsing. They are in fact very similar to the pillars built by Mansart, which proved their solidity for more than 3 centuries. The top of these massive pillars holds the quarry ceiling and stretches on the side to reach the top of the next pillar, where pressure forces meet. The filling method by injection will then be used where, after a well-sized drilling, large-grade dry materials are poured into the cavity. Liquid injections are also used, needing smaller drilling. They can consist of mortars or oil-bearing wastes to fill and impregnate the embankments, hardening material (bentonite) to form a compact mass, or with liquid sands (low cost).

In certain cases, consolidation can be done using concrete pillars, injected in circular cofferings set in important numbers, or through drilling and micro-poles between 110mm and 115mm in diameter closely spaced, that will be fitted in through the drilling. A variation of this method consists in bolting the quarry ceiling by inserting metallic rods, sometimes assorted with a ceiling-sealed lattice, sometimes covered with concrete flocking… these methods are very costly and their long-time durability hasn’t proved itself outside from research departments, projections or theoretical calculations. Note can also be taken that in some places, part of the underground legacy is preserved and that “old fashion” consolidations (rock pillars) are spoken of again.

This tour of underground consolidations would be incomplete without mentioning a specific type of work set in place at the beginning of the quarries inspections and maintained pre-emptively : ventilation shafts, which have almost completely disappeared in Paris. A good part of all these costly operations would have probably been useless by respecting a few simple methods, consisting in keeping good ventilation in the quarries and inspect it regularly to observe its natural evolution. These numerous shafts were meant to let a current of air flow through the galleries to dry the stone and thus prevent the progressive damaging of the limestone masses, weakened by the accumulation of humidity.

illustrations: injection in the Rue Claude Bernard in 2002. (1) Drilling and injection pipes installation (2) Connection with the compressor (3) Drilling seen from underneath just before injection ! (4) Concrete-mixer and injection of the gallery.

This story, started the 4^th of april 1777, will know a succession of inspectors more or less renowned, that will continue during their inspectorate the immense task started by their predecessors. Detailed biographies of each general inspectors from 18^th and 19^th century are available in the Ecole des mines annals. Here we will only keep the principal facts that happened during their inspectorate, linking them to the explanatory carved slabs affixed to their work. After the beginning of the 20^th century, dates will not be specified on these slabs any more; most of the consolidation work had already been done during the previous century. The quarries inspection mission will then evolve considerably toward a technical and consultative role, based on the maps updating work, often updated and sometimes made by surveyors for the uncharted sectors.

We will remember from this brief sum up of the IGC history the setting in place of tools and of the principal organization defined in 1777 by Guillaumot, reaffirmed and optimized under the work of M. Hericart de Thury. The principal inspection mission of the IGC will initially be done with reduced teams of technicians, all lacking experience in this field since nothing comparable existed before. This is therefore based on everyone’s personal capabilities that Guillaumot will manage his service appointing engineers, surveyors and technicians to oversee and do the work. Firstly, the geological mechanisms will have to be observed, at a time when serious theories on geological formation are just beginning to appear. They will need to compose between their sense of observation and their adaptation capabilities to measure the dangerosity of a rock formation and the ways of proceeding with the necessary works.

To complete this technical aspect of the works, a classification system will be set in place by Guillaumot in 1778 showing the year of the works, the inspector’s initials and the consolidation number. Consolidations from 1777 having been done already without being classified with ivory black-colored stone slabs, they will all be classified with a year of delay. An ingenious network of quarry depth measures, indexed on a standard based on the level zero of the river Seine, will be added to the system, allowing to know precisely the galleries’ localisation compared to the ground level and their real altitude. These methods are still used nowadays on modern maps which possess altimetric measures and the same space reference points, more than 250 years later. Finally, and this will represent a small revolution at that time, measurements done so far in inches and feet will all be converted to the metric system. A similar work will be done during the napoleonian empire, with the re-numbering of buildings in each street that will be observable underground and on the maps, since they will be precisely labelled by the quarries inspection.

Guillaumot will test all sorts of consolidation systems, reusing the quarrymen techniques and trying to find innovative ways, like these masonry works resting on series of lowered arches to distribute the weight, that can be found in the south of the 15th arrondissement quarries network and under the old railway axis under the rue Saint Gothard. The same experiences must have been applied to the mapping to come up with an effective survey system, but there are almost no traces left of the measurements made at that time by Guillaumot’s teams. The last phase of the service’s setting up will be the arrangement of the municipal ossuary; this is the work of two inspectors: one will have to find the ways to bring and pour millions of bones in determined sectors, the other the ways to show them off while respecting the memory of these millions of graveless remains.

The table cites every inspector from 1777 until 1909, showing in white their name and their inspectorate period, and in orange the kind of slabs they used to designate the works they realized, as well as a brief sum up of their achievements.

            Antoine Dupont -  1776

            90, 93 ...

This mathematics professor, appointed by the finances bureau will never be named “quarries inspector”. He will nonetheless assume the same functions for a few months and will start the first official works in the Capuchin quarry. Dupont will be deposed and will spend most of the rest of his life trying to discredit Guillaumot, appointed in his stead.

Guillaumot 1777-1791 (first inspection period)

I.G.1777 or I.G.XIIIR

He will be the founding father of the service, to which he will devote 30 years of his life. Guillaumot will become famous through the consolidation works of the Rue Saint Jacques, the reconstruction of the Mansart staircase and the transfer of the bones to the municipal ossuary.

Duchemin 1791-1792  - Demoustiers 1792-1793  - Bralle 1793-1795

I.D.1792 - ID2-1793 - I B1794 

These three sub-inspectors will, one after the other, continue Guillaumot's work and guarantee an interim period of one year each, to enable the continuity of the works started by their former "boss" who will definitely stay as their model. They will be accompanied by the same teams who will do maintenance works for 4 years.

Guillaumot 1777-1791 (second inspection period)

I.G.1777 ou I.G.XIIIR

After some serious politico-judicial adventures, Guillaumot, who had been deposed  in 1777, is reinstated at the head of the service. He resumes his work in the Val de Grâce, the vaugirard quarter, the Rue Dareau as well as in various quarries networks near Paris in the 13th, 14th and 5th arrondissements.

Administrative committee  1807-1808

C Mon 1808

After Guillaumot's passing, no candidate seemed to be able to show the same capability to lead this service. The quarries inspection is then entrusted to a commitee that must take care of the administration and taking care of current affairs. The works of the committee will only be occasionnal and always driven by urgent issues.

H.de Thury 1809-1831

I HT 1815

It is a brilliant 30 years old young man, specialized in drilling wells, who will be appointed to restart the activity of the quarries inspection. The most prolific of all inspectors will realize countless works, monuments, wells, and will realize the arrangement of the ossuary. He will introduce a geological and scientific dimension to the inspectorate and will write two reference books, before ending his career at the science academy.

Trémery 1831-1842

1 T 1840

First sub-inspector of De Thury, he will learn along the same lines. His inspectorate will last more than 10 years, during which he will particularly take care of the Montparnasse, Vaugirard and Tombe Issoire sectors. Trémery will leave his names in the annals for the realization of a square well located in the Capuchins quarry.

Juncker 1842-1851  - Lorieux 1851-1856  - Blavier 1856-1858

1 J 1845 - 1 L 1855 - 1 B 1856

These 3 inspectors will share a period of 15 years of inspection, during which the works will be concentrated on the consolidations located under the Montparnasse cemetery. Slabs with their initials can also be found to the south, near the Voie verte and the Arcueil Aqueduct. Juncker, for his part, will start with Mr. De Fourcy the first drafts of the quarries atlas, presented at the universal exposition in 1855. His successors will afterward dutifully go on working on these drafts.

De Hennezel 1858-1865  - du Souich 1865-1866

1 H 1860 - 1 S 1865

The decade preceding the 1870 war will be a quiet period for the IGC and will give the opportunity to normalize all the different systems used until then. The works will be more modest and less numerous, but counting with consolidations done in the 15th arrondissement and under the Rue Broussais.

 de Fourcy 1866-1870

1 F 1868

Eugène de Fourcy will, for the short duration of his inspectorate, resume the golden age of the IGC; he will notably participate in the consolidation works under the Montparnasse cemetery and of the foundations of the Montsouris reservoir. De Fourçy will also be the supervisor of the [quarries Atlas], still used today in its modern form: the IGC maps.

 Jacquot 1870-1872

1 EJ 1870

André Eugène Jacquot certainly had the most arduous inspectorate, in the middle of the 1870 war and later during the Paris Commune. During this period, the IGC will suspend its activity, go away from Paris  and finally Jacquot will be ordered to cease completely its activities, and surrender all the underground carries maps drawn by his predecessors to the representatives of the insurectionnal government of the Commune.

 - Lantillon -

 -

Named quarries "inspector", this Communard will not exercise any title in the service. His only decision will be the transferring of all the quarries archives to the Hotel de ville (town hall), which will be set to fire the same year, causing the loss of a century's worth of documentation on the underground.

 Descottes 1872-1875  - Tournaire 1875-1878 - Gentil 1878-1879  - Roger 1879-1885

1 D 1874  -  1 T 1876  -  1 G 1879  -  1 R 1880

These four inspectors will work for 15 years on the service reconstruction, and also on the reconstitution of the quarries Atlas, which will be done with the help of De Fourçy. They will do lots of work in the south of Paris, essentially bourrages of search galleries. Roger will also work in the 15th arrondissement and under Montsouris where some of his classification slabs can be found.

 Keller 1885-1896

1 K 1886

Keller will take care of various works in the Sarrette quarter and will distinguish himself with the consolidation of the Montsouris reservoir. He will probably be one of the last inspectors of the quarries' golden age that will end at the beginning of the 20th century and whose consolidation slabs,  tidily cut then blackened, will progressively be replaced by enamelled slabs or numbers hastily painted.

Wickersheimer 1896-1907 - Weiss 1907-1909

554 W 1899

For the last two inspectors having the same initials, their respective works can only be distinguished by the year of their making. During his inspectorate, Paul Weiss will start a friendship with someone named "Emile Gerards", sub-inspector of the Travaux de Paris and a quarry enthusiast who will become the author of the encyclopaedic piece of work: Paris Souterrain (Paris underground)

Since the origin of the Paris city and until the Revolution, all parisians were buried in various cemeteries. initially located around the city, according to an ancient roman law. Century after century, the increase of the city's size will progressively absorb its suburbs, with the result that in 1789 the 200 cemeteries in Paris, depending from as many churches, aren't sufficient anymore to contain the remains of all these former Paris inhabitants. Victims of the black plague, epidemics, starvations, of all the wars since the middle age are resting there, dropped in the cemetaries, piled up on several levels in the mass graves of the churches. Each day, new cadavers join the previous ones. Churches and cemetaries are vast, muddy fields where beggars, salesman, acrobats and prostitutes rub shoulders with each others.

Trenches are dug, dead bodies are left behind the precinct walls, and everyday risks of an epidemy in the city are greater. Paris is flooded by its dead, the odour is unbearable, even the bread and water are contaminated by putrefaction and all reports on public health safety are alarming. Citizens complain, incidents and infections are frequent, and cemeteries continue to be filled a bit more without anything else happening. Reports pile up; the first ones date back from 1554 and are already ominous. The medicine faculty of Paris and doctors from the royal science academy in 1737 only validate these declarations. For the sole Cimetière des Innocents, an estimate of 80000 cadavers were added during the last 30 years of the monarchy.

The architecture of this old church shows in cross-section the various additions that year after year transformed this place of worship into a crypt intended to the monks, then into a burial ground, reserved to the rich ones trying to bring the divine mercy on them by laying by their side.

Then come the Bourgeois who, lacking available space in the church itself will generously pay to be buried in the improvised cemeteries. Courtyards, fields located around the church expand and flourish with graves. Then additional floors niches, arches will need to be built, mass graves will need to be dug out to satisfy the people, from the richest to the poorest, unable to conceive being buried somewhere else than close to God after their death, notwithstanding any consideration for the living. On the alcoves' walls bordering the courtyard of the Saints Innocents cemetery, representations of dances macabres (dances of death), pagan images of dead and living dancing, figuring together the daily

reality of Parisians. (See annexes)

The walls in the cellar of a restaurant owner located  Rue de la lingerie, (at the actual level of  - Les Halles-) ) right next to the Innocents cemetery will break down the 30th of May 1780.  The discovery of what will pour into the building's cellar will cause an unutterable horror: cubic meters of old bones mixed with decomposing cadavers, entangled putrefied mortal remains made the wall give way under their weight. The building is completely contaminated, walls are oozing and it is said that just days after putting his hand on the wall, a mason will catch gangrene. The same happens with the surrounding houses and streets; this cemetery, like all the others in Paris, is a big mass grave located a few meters from apartment buildings, literally placed side-by-side with the cemeteries.

Following this incident, parliament will make a decree on the 4th of September, 1780 to close the Innocents cemetery. For the following 5 years this decision will have no other effect than accumulate more bodies in the surrounding cemeteries. The power in place appears to stay completely helpless against this insolvable problem.

The "solution" will come from police lieutenant Lenoir who for several years has offered to transfer the bones to the old underground quarries. The idea will finally be endorsed by a ruling from the state council. The first quarries inspector will be notified and the Cimetière des Innocents will be disused; the bones will be transferred to the hamlet called the Tombe Issoire*, between the Barrière d'Enfer and the Petit Montrouge.

This is how the history of the capital city's cemeteries and that of the Paris quarries will meet to become the Paris catacombs.

Convoys of black-draped chariots will form each evening funeral processions accompanied by priests and dirges, and will pass through Paris to transfer the mortal remains gathered over the centuries. Thusly, from cemetery to cemetery, these processions will repeat again and again, from 1785 until 1814. After a few years they will lose their sanctity to first become a curiosity then a mere routine. Bones will be poured into wells, shovelled and displaced on wooden carts then heaped up and classified by genre to end up piled up and put in order.

The Viscount of Thury, quarries general inspector from 1808 until 1831 will be in charge of imagining the arrangements worthy of giving the remains a well deserved rest. He will give these anonymous residents a dark and gloomy decorum, with philosophical citations related to death and remembrance. Tablets will indicate the cemetery of origin and the repository date.

Many illustrious figures will be found there pell-mell: Rabelais, Mansart, Charles Perrault, Jean Baptiste Lully, Danton, Robespierre, Colbert, Molière and hundreds of other celebrities, like Hericart de Thury and Guillaumot themselves, great architects of the catacombs who in their turn will find there their last abode.

More than 6 millions Parisians will so be transferred into what will become the biggest necropolis in the world.

Before going down into the dark underpasses of the city, one must take the time to recall the remembrance of the first visits that have been enthralling the Parisians for almost 2 centuries. The passion for this curiosity starts without a doubt with the transfer of the cemeteries' burial places before the eyes of dumbfounded inhabitants. At the beginning of the 19th century, solicitations will be sent to the catacombs management, to the quarries service or directly to Monsieur de Thury to ask for an authorization. Curiosity cabinets, showing samples of rocks discovered in the quarries, are visited from 1815 by a few scientists, researchers or naturalists, but the catacombs also were visited by some renowned guests: Charles X in 1787, the emperor of Austria François the 1st, on 16 of may 1814. Some very rare writings dating from this time and left on the walls by these mundane visitors, countesses or notables can still be found. In 1830 these few privileged ones stroll almost freely into the underground tunnels, more or less guided by representatives of the administration. Some visitors get lost, and bones robbery as well as damages are noted, which leads to the adjournment of the visits from 1833 until 1874. Only the highest personages still have the right to receive rare "invitations": Napoleon III in 1860, Oscar II of Sweden and the chancellor Bismarck in 1867. Then the 1870 war against Prussia will start, during which the Paris Commune will fight fierce combats in these underpasses.

In 1874 it is decided to re-open the "Ossuaire Général de Paris" (General Ossuary of Paris) every first and third Saturday of each month. the visit follows more or less this "catacombs way", traced with a smoke line on the quarry ceiling depending of the fancy of the administration staff across all the underground network, going down the Rue Saint Jacques, the Arcueil aqueduct, and passing of course through the geological and osteological cabinets. Visitors discover Port Mahon, sculptures from Décure and the quarrymen footbath... Everyone hurries up then to enter the catacombs through the Barrière d'Enfer courtyard, provided with an official authorization... and a candle. Then a real frenzy takes hold of the visitors who sometimes will go inside without guides, candles or authorization... on the 2nd of April 1897 and unauthorized concert organized in the catacombs will make a great to-do.

About a hundred guests will receive a mysterious invitation, asking them to present themselves in front of the catacombs entrance on a given day, advising them not to park their "cars" (with horses) in front of this address as not to attract the attention. These particularly precise instructions specify that the invitation is strictly personal and nominative.  Upon entering the catacombs, the guests are literally dumb-founded  discovering an orchestra made of 45 non professional musicians (who came here for their own satisfaction) but nonetheless talented: Monsieur Capet, solo violin, Monsieur Thibaud, first violin, flautists, clarinettists, percussionists led by Monsieur Furet, conductor who will propose the following programme:

1- Chopin's Funeral March

2- Saint Saens' Dance Macabre and Maria, a poem by M. Alla, read by the author

3- Choral et marche funèbre des Perses, under the lead of M. Xavier Leroux himself,

4- Aux Catacombes, a poem by M. Marlit, read by the author

5- Funeral march from Beethoven's Eroica Symphony

At 2.30 in the morning, all these people go back to the surface, not without having cheered the musicians and the conductor for this sacrilegious concert that fueled controversy afterwards in the parisian press and salons. The spot where this concert took placed is marked with a 'M' on the visit map (see hereunder) and can of course be visited.

The visit of the catacombs starts by climbing down a stair leading 20m underground, to the photography exposition room of the ossuary (this exposition periodically changes). A small path will give the opportunity for the eyes to get used to the pallid light, and to the ambient freshness (approx. 14°C). One then follows the underground double of the Avenue du Parc Montsouris, indicated by carved stone tablets, to join the galleries located right under the former Arcueil aqueduct, previously bringing water into Paris. If observed attentively a tablet can be spotted, indicating that one is located right under the aqueduct control peephole N°25, as well as tablets indicating consolidation works by Guillaumot during the revolutionary period. Those are codified in order to identify the work number, the initials of the inspector in charge of the work and the date of making: 13 G 1783 indicate the 13^th  consolidation by Guillaumot made in 1783.   (1)

An old 18^th century gallery dug in the quarry leads to an inferior level of exploitation, whose visit was out of reach from the public from 1995 until 2006 in order to allow renovation works. One enters in a small part of the quarry called "Port Mahon" [O], named so because of sculptures made by a former "veteran of his majesty", converted into a quarryman.

An enthusiast of the place, he sculpted "canvases" recalling his souvenirs of Majorca. These renowned sculptures can look summary but reveal in fact the remains of more than 2 centuries of history and restoring; notably, particularly delicate details can be observed on the sculptures of the "Quartier de Cazerne". On the ground, black and white paving covered by dust is hiding from the visitors' eyes.   (2)

The tour goes on towards the quarrymen's footbath [P], an initiatory place for quarrymen and more recently for students graduating from the Ecole des Mines that get themselves baptized in this fountain, whose water is so pure that one can soak one's feet involuntarily if one does not pay attention. This water flushes from the ground water and previously allowed to measure the variations in the water's height, as well as draw water for the surrounding working sites around. This path will progressively rise towards the upper level to lead up to the "Vestibule" (lobby) [A], an imposing room designating the entrance into the catacombs themselves and with the famous warning "Arrête! C'est ici l'empire de la mort" ("stop! Here lies the empire of death"), a very beautiful tablet summing up the origins of this place and reminds to the visitors the architects of these arrangements.

The path then leads back south toward the oldest arrangement of the catacombs. This room, sided by two imposing black and white pillars enhance the lampe sepulcrale (sepulchral lamp) [E] sitting prominently in the center. The monument was built to replace a similar lamp in which a continuous fire was fueled, allowing watching the air flow in the galleries. This ingenious system, set in place at the beginning of the bones handling work, was afterwards completed by various ventilation wells, drilled from the surface down to renew the air underground. The smoke visible to the eye escaped toward the surface following the natural air current. Bottlenecks were placed on each well to check if air flow was sufficient. In the contrary case, another well was opened.

After that, the visitor passes in front of two of the most unknown places, which are nonetheless on the list of sites particularly prized by visitors in the 19th century. Totally invisibles today, they are waiting for an unlikely refurbishment. The Cabinet Minéralogique des Catacombes (mineralogical cabinet of the catacombs) [H]  is the very essence of the work done by the IdC at that time.

This small masoned room surrounded by stone benches contains the vestiges of two fake stone stairs. On each step was deposited a rock sample coming from the stone deposit constituting the geological layers in the quarries. Scientists and onlookers came here to examine these samples, typical of the parisian subsoil. On this old photography can be seen the remains of the osteological cabinet, containing mummies and bones, as well as the names of the geological layers written on each step. At the far end lies a tablet indicating the discovery of remains of roman cement.

This cabinet, which is filled in, still contains some of theses vestiges.  (3)

After that comes the imposing (yet fake) grave of the poet Gilbert [G] where a citation can be read, before arriving in a gallery going to the right. It is in this direction that the second curiosity cabinet was located, invisible to the eyes of thousands of visitors who visit these galleries each year. The osteology cabinet [F], made by men of science of the 19^th century, was arranged to show the most curious bones found among the remains transferred from the cemeteries, their osteological particularities having justified the building of this curiosity cabinet, very popular during this period. It was vandalized during the 1870 war, and then collapsed in 1892.

This path winding through the oldest galleries of these quarries goes on until a great pillar, showing the date of 1894. During archaeological searches when the municipal ossuary was created the heart of general Campi, more renowned for this anecdote than for his feats of arms, was found in a lead box containing a mysterious parchment. This relic was inserted inside the pillar which became later the Pilier au coeur embaumé (the Pillar with the embalmed heart) of the catacombs [I]. The tour then continues north, to reach the bones of the Saint Laurent church [J], victims of the first combats during the revolution. By observing attentively the plaque of this acroterian grave, in the shape of a small chapiter, it can be seen that the text was chiselled anew. The last letters from the initial text "bones... violated by the federated the 17^th of April (= profanated by the federated during the Commune in 1871) still appear, and were replaced by the less controversial word "deposited" in 1880.

This last part of the tour in the catacombs goes through the grave of Françoise Gellain [K] who devoted her life to get her "companion" out, an adventurer named Jean Henri de Latude, after she found a message from him, thrown through the bars of his jail in Bicètre. A few steps after lies a tablet indicating one of the numerous deposit of bones coming from the Eglise des Saints Innocents [L]. The cemetery of this church is in a way at the origin of the catacombs (4). One can see for that matter that the different tablets dating from 1786 until 1806 are written with a typography much older than the others. Cut on small square slabs, they respect the letterpress from Guillaumot's time.

The Crypte de la passion (Passion's crypt) was also baptized Rotonde des tibias (Rotunda of the shinbones) [M] because of this circular arrangement made only with bones. It is in this small crypt that the famous 1897 concert took place in the catacombs. (See above). One can see a carving from the time, the absence of the rotunda around the typical pillar whose top can be seen, undoubtedly illustrating the personal view of the author to illustrate the scene. A few meters away, the visit of the ossuary itself ends, closed by a heavy metal door. Above the door, the last inscription "Memoriae Majorum" ("in memory of our ancestors") sums up by itself the religious and macabre spirit with which this place was created, to be visited and at the same time to serve as the last burial place for the many generations of Parisians it contains.

The last gallery in the ossuary tour passes straight under the Rue Dareau, formerly called Rue des Catacombes and from which a few tablets or writings on the walls still remain. As the old maps attest, this part of the quarry previously winding was completely rebuilt and consolidated to form this long, straight alley bordered by rectilinear walls. It's probably the presence of old collapsing cavities [N] that led to the securizing of the place with many consolidation works, from which old traces can be seen at the end of the visit. By looking at the ceiling, one can see two spectacular works dating from 1874 and 1875, rising to a height of more than 11m. This visit ends with the last 2 tablets detailing the methods of consolidation of the cave-ins of this quarry.

A stair takes the visitor back to the surface, under the vigilant eye of the ossuary watchmen, who will without a doubt make sure that no dishonest visitor takes back home a macabre souvenir of this visit into the underpasses of Paris.