Chapter 3 – Debate with experts and general discussion
p. 81-89
Texte intégral
1Moderator : Michel Clément
2Experts : Jean Clottes, Marc Gauthier, Jean‑Michel Geneste
3[ The interventions in italic were translated from French to English ]
4Mr. Michel Clément
5It is 11.35 a.m., you may ask questions until midday. Everyone on the platform is in a position to answer these questions. Would anyone like to speak?
6Mr. Ralph Mitchell
7My name is Ralph Mitchell. I am a microbiologist at Harvard University in the United States. I have a question concerning the relationship between the digital simulator and the growth of the mold. I am always concerned about computer models of biological activity. My question is: has your simulator been able to detect or predict the growth of the black mold, and if not, can you obtain sufficient data to go into your simulator so that you could protect and prevent future mold growth?
8Mr. Jean‑Michel Geneste
9At present, and in its current design and operating state–but subject to the interventions of this afternoon’s specialists–I can respond that the climatic simulator might one day be able to answer your questions and operate at the microscopic scale, meaning at the level of colonizations. At present, it functions in a global manner, with a degree of precision that permits us to observe only the global metric or, more particularly, decimetric, movements of convections in the atmosphere. It currently functions more on the basis of climatic compensation and human presence attenuation models. I don’t know if I have answered your question precisely. Nor do I know whether it will be possible to have information that is sufficiently precise to allow us to work specifically on the black fungi colonies. That is not the main goal for the moment.
10Mr. Paul‑Marie Guyon
11Hello. I am an honorary Directeur de Recherche at the CNRS and a physics researcher. My name has been mentioned because I was fortunate enough to be invited to Lascaux in the 1960’s to take part in the first climatological studies and then in the installation of this famous machine. I am not here to make a major presentation, but to propose some ideas that could orient future actions. I am thus going to be critical, but in the scientific sense of the word, in a constructive spirit. For a long time, certain researchers and I have addressed those responsible for the cave, in the administration of the Ministry and with the members of the committee. What I had hoped would be a collaboration, in the end proved to be extremely difficult. I hope that we will now be able to evolve, because our goal is to move forward.
12We have brought people together and presented a project to discuss these questions within a small working group called LIST. We have talked a lot about climatology and methods, and my question more precisely concerns these methods. In the sixties, we had a very specific program relative to the climate of the cave.
13Dr Bauer had observed calcic modifications, precipitations and attacks. The chemists on the committee affirmed that it was a question of the carbon cycle–which by the intermediary of CO2 disolves calcium carbonate which then precipitates in the form of calcite–and that the climate was involved. It was therefore necessary to restore the climate that existed before the discovery and we thought about how this could be achieved.
14Once the cave had been closed, we saw that there were still periods of condensation in the Hall of the Bulls. The idea of a possible compensation on the basis of natural currents then arose, hence the suggestion of installing a system of climatic assistance in order to create equilibrium conditions with parameters as close as possible to the natural ones, and with a manual control system to ensure perfect stability and to avoid any possibility of water condensation loaded with carbon dioxide attacking the paintings.
15No precipitation and no modification of the calcic support, this was the problem at that time. And what is it now? Mr. Gauthier has indeed explained that a new machine will be developed and that the studies will be pursued. What is the primary goal? No calcic precipitations? And is the second goal to achieve the microbiological stability of the biofilm? How and why? What are the valid conditions for this? What is the program for this machine?
16Mr. Jean‑Michel Geneste
17I will try to answer your questions. This is why I once proposed a synthetic diagram of the functioning of the cave with the old climatic assistance system and with the current one.
18Treating the biological problems will require greater efficiency and better control of the parameters that you have just described, extending beyond the few meters in which this system is functioning today inside the Hall of the Bulls.
19We must be able to control and completely eliminate the risk of condensation on the walls in the Axial Gallery zone—which is problematic— and in the right‑hand gallery. Hence the need to work more on a macroscopic scale, with a reconsideration of this machine and of the additional cold spots that would make it possible to project, so to speak, the system that you designed further than its current effective operating zone, within the context of changing elements. This would likely contribute to restoring a natural equilibrium in the cave, but in this respect we are back in the realm of hypotheses. What is the precise link with microbiology? We start from the principle that by improving the hygrometry and temperature criteria, we are taking far fewer risks. For the moment, this is the only way I can answer you and it is only my point of view, which is very global, following the presentation that I have just given.
20Mr. Paul‑Marie Guyon
21It seems to me that there are alternatives in terms of the ventilation of the cave. I perceive a hypothesis behind the idea you are proposing. The cave will have to be ventilated since due to temperature changes, the simulator seems to indicate that the ventilation is not as rapid as it was in the past. This must be verified in place with precise measurements. And that has not been done…
22Mr. Jean‑Michel Geneste
23That is part of the system.
24Mr. Paul‑Marie Guyon
25There are alternatives to this system. When I was working there, the Shaft had not been closed and the cave’s natural ventilation had not been stopped. Whenever the atmospheric pressure fell because of storms, the CO2 level increased, sometimes as high as 6%. I even had a dizzy spell…
26Mr. Jean‑Michel Geneste
27This phenomenon still exists in the cave.
28Mr. Paul‑Marie Guyon
29This phenomenon still exists. At the time, with a CO2 detector that was provided by a member of the committee, we were able to measure, go down into the well, go back through the course of the depression, gradually as the weather settled, and see how the CO2 gradient evolved until we got to the entrance. At the same time, the instruments that had been placed in the cave (little boats with floats) all moved in the same direction. We were no longer in a convection system, but in a natural ventilation system within the developing karstic network. A pressure variation of 10 mbar equals a 1% increase of volume flows toward the exterior.
30Mr. Jean‑Michel Geneste
31What you are proposing and the system that you have described are also in accordance with the work carried out by the simulator study group. Beyond my somewhat simplistic outline, which, in the introductory presentation, presented only one solution, there are other studies and analyses of the parameters being conducted by teams from the scientific committee and various laboratories. At the same time, several solutions are being tested: the cold spots that I mentioned, the opening of the original oculus that has been considered, the re‑installation of a double‑partition “Bauer airlock”, the opening of the Shaft, as well as other possibilities that could be considered.
32At this time, we are not working on a limited solution, but for the management of a complex situation. Once again, I think that this debate will be more fruitful once we have heard more in‑depth interrogations. May I remind you that in my introduction, I presented only summaries, which are perhaps rather simplistic.
33Mr. Michel Clément
34There will thus be presentations this afternoon that will go into greater detail on what you are saying. You indicate that, as far as the machinery is concerned, different scenarios and different possible utilizations are being studied. There are thus various possibilities still being examined.
35Mr. Jean‑Michel Geneste
36Yes. Furthermore, we are conducting many additional analyses to allow us to argue our case and measure the speeds and temperatures at different locations in the cave. These analyses are in progress.
37Mr. Marc Gauthier
38That is the utility of the simulator, to allow us to test these different solutions without doing anything in the cave.
39Mr. Michel Clément
40Madam, you have a question?
41Ms. Laurence Léauté‑Beasley
42I am the President of the International Committee for the Preservation of Lascaux. My question concerns this famous new machine dating back to 2000. Can you tell me what scientific principles dictated your decision to change the operating mode of a machine that had proven its efficacy for 40 years, to replace it with another system operating according to totally different and opposing principles?
43Mr. Jean‑Michel Geneste
44I am going to have to clarify and reformulate what I said. The design consultants and engineering consultants with whom the head architect in charge of the operations, in liaison with the State bodies, placed the order to adapt a machine, had indeed been instructed to develop a machine that would function according to the same principles as those developed by Paul‑Marie Guyon
45What they delivered does not function, in practice, with the same degree of flexibility, but the principle of water condensation on aerial batteries is exactly the same. I cannot say that it is a different system. The form, equipment and technique mean that other types of apparatuses were presented, but the principle remains the same. They are positioned in the same place, have larger volumes and are encased. They suffered from a certain number of anomalies that posed problems for us.
46Ms. Laurence Léauté‑Beasley
47Thank you for your answer. I would like a small additional clarification. The Guyon machine, from what I have understood, functioned using a convection current assistance model. So you are saying that the new 2000 machine did not function using forced air?
48Mr. Jean‑Michel Geneste
49The new machine was encased, and so that the air could go and cool down and make it possible to recover the condensation water, there was indeed a fan, which operated at very low speed to pump the air on to these batteries. In the past, it was simply the air that went there naturally.
50We do indeed have a different operating method in this sense, but it is based on the same principle. I agree that, with respect to the specifications, this is not exactly the machine that was requested. It is not an identical replacement.
51Mr. Philippe Malaurent
52I would like to make some clarifications concerning this machinery that we keep talking about. Its operating principle was strictly identical to that of Paul‑Marie Guyon’s machine. The problem was due to the ambiguities with regard to this forced convection. What was forced in the machinery was the change from static batteries to dynamic batteries. The fans, which have practically never been used, were only designed to combat the load losses and make the fluid pass through the batteries. The best proof–and I am almost ashamed of this–is that I had hot wires purchased, as controls="true" in the chutes, to measure the air currents. Nonetheless, the orders given were to not measure anything; in no event did we want to have the possibility of measuring the speeds, because we could not manage to do this naturally. These hot wires were therefore installed as a precaution, should anyone accidentally activate the fans that we did not want to use. Once again, the term “forced” applies to the internal operation of the machine, and in no way to a forced convection inside the cave, which itself remained static.
53Mr. Jean‑Michel Geneste
54I believe it was you, Philippe, who asked for the fans to be disconnected immediately. They have never been operational.
55Mr. Philippe Malaurent
56The main problem with this machinery is that it is not very flexible. Its utilization poses a problem for us, not its actual principle. Why remove these fans? Because the machine’s performance diminished automatically. Because there were biological problems that had not been taken into account and which, for example, led to the formation of condensation water pockets in the honeycombs that composed the exchange surface of the batteries, which easily trapped spores and bacteria. The padding of the CTAs (air treatment enclosures) also posed a problem because it insulated them, thus creating an ideal home for these unwanted guests.
57Mr. Michel Clément
58Sir, do you have a question?
59Mr. Michel Goldberg
60I am an Honorary Professor at the Institut Pasteur and member of LIST. My question concerns the simulation models. These simulation models that we can build can be considered valid only when they have been tested experimentally. Can you tell me what experimental methods were used to verify the predictions made by the model?
61Ms. Delphine Lacanette
62My paper this afternoon will perhaps shed more light on this. What I can say for the moment is that instruments have been in place in the cavity for many years and that we use the data they provide to verify the results given by the simulator.
63Furthermore, additional instrumentation is planned for the coming months, which will allow us to validate the simulator to an even greater extent.
64Mr. Michel Goldberg
65If I understand this correctly, you are trying to render your simulator compatible with what you are measuring nowadays. In this case the simulation model does not have any predictive value.
66Ms. Delphine Lacanette
67That is not what I meant. In a simulation approach, you validate the tool with respect to measured data and then use it to predict what you cannot measure in any way. The validation has thus been done and will be further improved. The tool is used to travel through time, either into the past or to project us into the future. It has a definite predictive value.
68Mr. Jérôme Glaize
69I work on the Sud Ouest newspaper. It was said earlier that the decisions made are followed up by protocols. It is on this point that I would like you to enlighten me. Whether concerning the replacement of the machine in 2000, or the photographic survey mentioned earlier, we have indeed seen in your respective presentations, Mr. Geneste and Mr. Gauthier, that there were a certain number of problems relative to the implementation of these decisions, particularly during the installation of the machine–Mr. Geneste mentioned the introduction of wood planks and the appearance of mold on those planks.
70What was the protocol applied for the photographic survey? How was the time quota or the light exposure defined, given that we speak today of the melanin produced by this fungus to protect itself from light.
71Legitimate questions can be asked concerning the implementation in the cave of the decisions taken over time. Whatever the solutions envisaged for the future, if they are implemented under the same conditions as your earlier decisions, the result might be the same, or even worse.
72Mr. Jean‑Michel Geneste
73Your question is perfectly legitimate from a methodological point of view. I did indeed say that there had been collective reflections. And it is true that the definition of specifications takes into account all the constraints of the realization of a project and under what conditions. The list of specifications included the sanitary conditions, the number of workmen and the number of working hours per day. I did nevertheless admit that, in the initial phase of the work, we were certainly less vigilant than we should have been, considering the introduction and use of planks–which were immediately removed. When I spoke of “wood” in my presentation, what I meant to convey is that Lascaux Cave is located in the middle of woods and crops. That is what I was alluding to for the Fusarium, and not necessarily to the introduction of materials. I did nevertheless cite the presence of other materials, such as the organic insulation material that was placed around the machine. Concerning the surveys and photographs in particular, the impact that this human presence could have was assessed in the framework of the meetings of the Scientific Committee, and cold lighting systems, based on neon lights, were chosen. Obviously the teams working on the surveys were not asked to work in the dark, nor were the photographers asked to work without a flash. When I told you that we had accepted responsibility for this risk because we believed it was important to obtain these decision‑making, communication and archive management tools, we were obviously not aware at that time of the risk of the development of fungi with melanin, which in the process of melanization, could increase due to the greater amount of light.
74With hindsight, we can now analyze things differently. At the time, I think that we operated with as much foresight as possible in the accomplishment of the work and the presence of the survey team. The end of the survey phase was cut short and a later phase of that survey was not resumed, once we had become aware of the consequences of human presence.
75The question of human presence poses many problems and we are using, also with hindsight, the time spent in the cavity by humans since 1972 to evaluate this presence, which was managed as well as possible but, it is true, without anticipating the fact that black fungi were going to develop. This development is perhaps linked to the light, but their original color was definitely black.
76Mr. Marc Gauthier
77I must emphasize the fact that we did not launch the survey phase without a very precise working protocol. On the contrary, the limits imposed on the work were lower than what would normally be tolerable. As a precaution, we stayed below the security limits. There was indeed the phenomenon in the right‑hand section, but not only for the reasons just given by Jean‑Michel Geneste, but also because we still did not know that the air was completely inert, and perhaps even more so in the right‑hand part than in the Hall of the Bulls and in the Axial Gallery.
78Mr. Michel Clément
79We will take one last question.
80Ms. Christine Chaumeil
81I am a microbiologist. I have a question concerning the history that you have summarized. I believe that at some point there was a phase when acarids were used to destroy the fungi. Was this before the appearance of the black fungi?
82Mr. Jean‑Michel Geneste
83Before you go any further, no! There was never any question of that. Studies are currently being conducted on the role played by acarids in dissemination, but acarids have never been used.
84Ms. Christine Chaumeil
85Okay, I must have been misinformed. Furthermore, it was a question of Fusarium oxysporum and then of Fusarium solani. Are they both present?
86Mr. Jean‑Michel Geneste
87Tomorrow’s papers will address to this issue.
88Mr. Michel Clément
89I will take one last question and then we will stop there.
90Mr. Michael Petzet
91I am a member of ICOMOS. I do not understand why the machine was changed. Before the change, the system was in equilibrium. If nothing had been done, this meeting would not be taking place–regardless of the honor it is for me to be here. This was a terrible mistake. This disaster would have been averted if this machine had not been replaced. You are now saying that it is the same machine, but this does not seem to be the case. The new apparatus is highly active, unlike the one that was in operation over the last forty years. What should have been done was to safeguard the equilibrium produced by the old machine.
92Mr. Jean‑Michel Geneste
93The intention was to replace this machine with an identical one because it functioned well. However, even if the new machine was perhaps dynamic in its components, it was not more active, on the contrary. This is not an easy issue.
94The reason why I, as the Curator, made this decision with my colleagues was that at this moment, the entrance of the cave was filled with metallic installations–including this machine, the pipes, the stairways and all the grills on the floor–that were in a state of alteration and corrosion to the extent that this equipment was hardly still standing. It was a matter of sanitary urgency which, due to the relative environmental stability, led us to consider, authorize and gradually advance towards this modification phase, whose planning began in 1994 and which was completed in 1999.
95We attempted to obtain assurances, but we were in a situation that required us to replace the machine bit by bit. We consulted numerous colleagues and moved in this direction because after more than 40 years, this equipment was in a truly awful state, so much so that we no longer dared to let anyone into the cave. The metallic parts were simply corroded.
96I perfectly understand your remark. We attempted to design a machine adapted to modern standards and we followed the advice of the consultants who proposed this type of equipment and created it for us.
97Mr. Michel Clément
98Thank you Jean‑Michel Geneste.
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