Historical sketch of the Mines and Saltworks of Bex
Mr. Ch. GRENIER, deputy, president of the Board of Directors of the mines and saltworks, in Bex.
At the entrance of our Bex Salt Mines, we could engrave this inscription, the appropriateness of which no one would dispute:
Necessity is the mother of industry.
The salt deposits in the lias are generally so poor in salt that they are no longer exploited. The mines of Moutiers in Tarentaise have been abandoned. Ours, which belong to the same formation, still exist.
Their existence in ancient times was due to the lack of communications, and their preservation in the present time, to various circumstances that we will discuss, which have been for them a compensation to the extreme poverty of the salt rock.
Our saltworks will not offer you, Gentlemen, any other interest than that which is attached to a thing that still exists, whereas at first sight it seems that it should no longer exist.
The mines and salt works of Bex have gone through three successive phases, each of which appeared at a time when they were threatened with complete abandonment.
These three distinct periods, which logically follow each other, are briefly described below:
The first one is the exploitation of the salt springs, evaporated at first as they were, and later after having been graded.
The second, includes the extraction of the salt rock and its leaching in special rooms.
The third one, which we are going through today, is characterized by the leaching of the salt rock in place.
The first salt spring was discovered in the middle of the 16th century (1554), on the banks of the Gryonne, in a meadow belonging to Victor Croset, at the place where the Puits-du-jour (day-well) opens out today. It provided 40 to 45 cubic feet of water of 3° to 4° of saltiness, that is to say approximately 100 pounds of salt, per hour.
The archives of Gryon tell us of a pastor of this parish, named Gaultier, who drowned in the Gryonne at that time, on his way to the village of Arveyes, where the salt water from this spring was evaporating in simple copper boilers. After having had several owners, it was bought by the State of Bern in 1680. Some research galleries had already been dug. However, it was not until this time that the underground work became important.
In 1684, a Savoyard miner named Lombard, suspecting that the salt spring was rising from the depths of the earth and was partially lost in its upward march, proposed to cut it off by a gallery. He found it 50 feet lower, more abundant and with 11° of salinity instead of 4. This encouraging result was the starting point of the lowering theory. It led to the numerous works that followed in quick succession in the mine, with the aim of discovering more and more salty and abundant springs, by cutting them at a greater depth.
The restricted framework of this sketch does not allow us a detailed description of these works. It will suffice to know: that the main gallery of the Coulât, completed in 1707, in 13 years, has a length of 2800 feet; that in 1726, on the plans of M. the director Gamaliel de Rovéréa, one undertook the main gallery of the Bouillet and the great staircase of 454 steps which connects the two mines; that, along the way, a certain number of salty springs were discovered; but that the hopes, which had given rise to the first successes obtained by the system of the lowerings, gradually faded away. Several springs lost their saltiness partially, others entirely. Thus the spring of Providence, the first one exploited, the one that gave rise to so much work, flows today, still abundant, but entirely desalinated, in the gallery of Bouillet. One of these springs is an exception to the rule; it is the Bon-succès spring, called Ansermet spring, after the miner who took care of it. This brave and old servant died a few years ago in the village of Fenalet, at a very advanced age. This spring has maintained its initial salinity of 22 to 23°. The spring of Augure, of lesser importance, is in the same case.
There are two facts here, to which we call your attention. We see first of all salted springs losing gradually, then completely their salinity; and beside them, other springs, which still preserve their initial salinity. This leads us to say a few words about the two theories, formulated at the time, on the salty springs of Bex.
The first shows rainwater and freshwater springs encountering in their course salty massifs, located at various heights, and then flowing into a space occupied by a schistose and spongy rock that has been described as a cylinder. The cylinder is a kind of pocket surrounded by a solid and impermeable rock. By digging this wall lower and lower, the water had to be ever more abundant and ever more salty. The first successes obtained by the lowering seemed to give reason to this theory.
The other theory also admits the cylinder as a reservoir of salt water, but it places the salt massif at a great depth below the gypsum formation. It would happen there something similar to what takes place in the artesian wells. The fresh waters, after having penetrated in the bowels of the earth and having been saturated with salt by their contact with this salty massif, would go back to the surface and would thus give rise to the salty springs. The gradual salting of most of our springs seems to confirm the first of these theories, while the constant salting of the Ansermet and Augure springs would give reason to the second.
The great Haller, who directed the mines of Bex about 1750, admitted the existence of a salt lake, situated at a considerable depth, whose water pushed upwards by natural forces, gives rise to salt springs. We do not know what these natural forces, which are resting today, may be; but we would be happy if we could one day arrive at the salt lake of M. de Haller.
The bouquet of the theory of the abaissements was the proposal made to LL. Excellences of Berne by M. de Beust, to produce a plan whose execution was to result in a much more considerable yield from the mines, a plan which he would reveal only on the promise that a sum of 80,000 livres would be counted to him beforehand. The acceptance of this condition led to the drilling of the Providence well, and to the loss of the spring of that name, which instead of responding to the forecasts of M. de Beust, gradually lost its saltiness. He was also the one who had the large Bouillet well dug to 80 feet below the level of the lake. He was to receive, as a share of the profit, a quarter of the product of the salty springs that would be discovered. As these springs were insignificant, the business was not as good for him as that of the Providence well. In both cases, the State of Berne paid for it. We can see that M. de Beust was not a great supporter of unproductive and disinterested science. He was also the one who inaugurated the graduation buildings, begun on his plans in 1729, which completed the system of exploitation of the salt springs.
The number of these springs, as well as their saltiness, having considerably decreased, Mr. Jean de Charpentier, who was attached to the direction of the Mines since the year 1813, proposed in 1823 the extraction and the leaching of the salted rock, of which he had just discovered important heaps.
Here begins the second mode of exploitation of the mines of Bex.
Towards the end of the last century, shafts of a certain depth were dug in the salty rock at the Vaux mine. They were filled with fresh water, which was brought out more or less salty after a month's stay. But this water, without movement, would deteriorate, as is still the case today when salt water stays too long in the reservoirs. The salt rock was also found in 1705 at the so-called Graffenried mine, where you can still see the chambers that were used to wash the salt rock and still contain the residues.
However, the regular exploitation of the salted rock and its leaching in rooms, dug ad hoc in the non-salted rock, dates only from 1823. This new method of exploitation made two important advances. It allowed to increase considerably the production of salt, which was no longer dependent on the variable yield of the sources. Then the leaching of the salted rock, producing saturated water, made useless the buildings of graduation, the purpose of which was to increase, by the spontaneous evaporation in the air, the degree of salinity of water. The defect of this mode of exploitation was to be expensive. The first costs of the establishment, consisting in digging desalters at Coulât and Bouillet, were considerable. Those concerning the exploitation were also very high. They consisted of blasting the rock with powder, transporting it to the desalters and trucking the tailings out of the mine. Nevertheless, the price at which the state could pay the salt to the salt works left the latter with a sufficient profit. This was no longer the case when the construction of the railroads brought about a significant drop in the cost price of foreign salt in our country. The struggle became all the more difficult as wood, the only fuel used at the time, had become so expensive that, in the last years of the exploitation of the salt works by the State, it was paid for at about three times the price at the beginning of the century. So there came a time when the salt works, far from giving a profit to the State, constituted a big loss. From then on, their abandonment was claimed, each year with more insistence, by the parts of the canton which were not directly interested in their conservation.
The commune of Bex, threatened to see the disappearance of an exploitation, which, for so long, gave a secure job to its citizens, while producing annually a movement of money of a certain importance, was moved by this state of affairs.
Steps were taken with M. d'Alberti, director general of the Wurtemberg salt works. A correspondence begun with him on June 21, 1863, was brought to the attention of the Waldensian government. Mr. d'Alberti was invited by the government to visit the salt works in Bex, and he did so. Back home, he wrote a very detailed report, which he sent to our government. His conclusion was that the evaporation apparatus had to undergo a complete reform, of which he provided the plans. But he could not, he said, make a final judgment on the mines, which required a study, which, to be complete, would be long and meticulous. The State Council invited Mr. Braillard, the architect, and Mr. Colomb, then director of the salt works, to go to Friedrichshall to examine with Mr. d'Alberti the installations of this line, which had given rise to the proposed plans. The report of these gentlemen having been favorable, the State Council mandated to the Grand Council the funds necessary for the execution of the work. The commission charged with examining the project made its report through M. Eytel on 17 May 1865.
In the discussion which opened on this occasion, M. Demiéville, deputy of Yverdon, one of the most ardent champions of the abandonment of the Bex salt works, gave a most remarkable speech. Using the eloquence of figures, he proved, by calculations of overwhelming logic, that the Bex salt works caused the State an annual loss of 74,567 fr. 40. He claimed that by paying as a pension, to the 112 workers employed at the time in the salt works, half of their salary, the State would still earn, by closing the mines, an annual sum of 35,606 fr. 30. On the proposal of the commission, the Grand Council postponed the definitive solution of this question to the autumn session.
This postponement was nothing more than a death sentence for the Bex salt mines. There was still only one way to preserve them, namely their continuation by private industry. A few citizens met and then approached the State Council in order to examine with it the conditions under which this resumption could take place. Following numerous conferences, an agreement was concluded on September 8, 1866, and ratified by the Grand Council on the 24th of the same month. A society, composed for the most part of citizens of the region and workers of the Saltworks, was constituted by act of November 23, 1866.
It immediately set to work, built at Le Bévieux, on the plans of M. d'Alberti, new evaporation equipment and began to operate on its own account in the autumn of 1867, the operation having ceased on July 1 on behalf of the State.
The new society could only succeed by making great savings, and therefore profound changes, to the system followed by the state.
To reduce the cost price of salt water and, once this result was obtained, to evaporate this water at a lower cost, such was his program.
We have now arrived at the third mode of exploitation of the Bex salt mines, that of the leaching of the salt rock in place.
This method was not entirely unknown to M. de Charpentier. Some words pronounced by him in the last years of his life, concerning what was practiced on this subject in the mines of Austria, came back in our memory. He doubted, however, given the poverty and nature of our rock, that the same system could be applied in our mines. The question was of such importance to us that a visit to the Salzkammergut mines was decided upon. This visit soon brought us to the knowledge of the simple and practical procedures followed there. To dig a room at a certain depth, to introduce fresh water so as to immerse its ceiling on a thickness of 20 to 30 centimeters; then, this quantity having been diluted and desalted, to raise again of as much the level of water; and finally, to receive in a lower gallery the saturated salted water gathering at the bottom of the room; such is the series of very simple operations which is followed in Austria
In the Salzkammergut, however, the salt is bound to a crumbly marl, into which it enters to the extent of 60 to 80 percent. The water washes away this marl, the residue of which is deposited on the floor of the room, and the salt dissolves. Things do not happen in this way at Bex, where we are dealing with a compact rock, containing only 20 to 25 per cent salt. The question was how this rock would behave in the presence of water. A fortuitous event facilitated our research and gave us good hope of success. A filtration occurred in the lower room of the Graffenried mine and the water reached the ceiling and gradually submerged it. A simple pumping soon put it back to dryness, and allowed us to realize the state in which it was. We noticed that this ceiling, more than three meters thick, was as solid as before, but that it no longer contained any salt. This experience showed us that the desalting of our rock, by fresh water acting from the bottom to the top, was perfectly practicable, on a thickness of 3 meters at least. Our works were then directed in the direction of the leaching of the rock in place.
The first works of this nature were undertaken at Bouillet, in a small room that we arranged in tiers. The result was so satisfactory that before it was exhausted, we built a second one at the Coulât. This is the
The latter provides us today with almost all the salt water that we evaporate at Le Bévieux. Before sending it there, we pass it through the desalters, in order to be sure of complete saturation. Used for this purpose, the desalters receive today hardly more than 1/6 of the quantity of salted rock which was introduced there formerly.
A turbine, established at Bouillet, pumps salt water and raises the stones. Later, an oscillating machine was installed at the Coulât to draw salt water. These two machines significantly reduced our operating costs in the mine.
It is in the large room of Bouillet that the most considerable work undertaken up to now in view of the leaching of the rock in place is to be found. You will be able, gentlemen, to appreciate the importance of this work in the visit you propose to make to the mines, a visit in which we shall be happy to see you take part in large numbers. A trench 20 feet wide by 30 feet long was opened in 1870. It was dug entirely in the salt rock, its two edges reaching the non-salt rock. It is therefore an exact representation of the salt pocket. This trench, having reached in April 1875 a depth of 142 feet, reasons of prudence and economy committed us not to push it further down, and to continue the descent by means of shafts. Shafts, parallel to the trench, and touching the unsalted rock at both ends, were drilled at unequal intervals, in order to know always exactly the width and configuration of the pocket. At a depth of 242 feet we encountered the unsalted rock. Wanting to be sure that we had reached the bottom of the pocket, we drilled 2 galleries in the opposite direction. The first one stayed in the unsalted rock; but the second one, directed to the north, soon entered the salted rock, and stayed there for 48 feet. The pocket had thus undergone a total deviation on the north side; but its length, instead of decreasing, had increased appreciably.
We have now reached a depth of over 270 feet, without any reduction in length. When we have reached the bottom, or when we deem it advisable not to push our work any further, we will establish, under the salt massif, a network of galleries which we will fill with fresh water. This water, by gradually rising, will gradually desalinate all the salt rock.
While working to produce cheaper salt water in the mine, we did not lose sight of the question of evaporation. During our first installations at Bevieux, in 1866, Mr. Bridel, the engineer, whom we asked for his opinion on the means to be used to make better use of the products of combustion, proved to us that there was little to hope for on that side. Direct all your efforts," he said, "to a better use of the vapors. They carry with them in the air most of the caloric developed by the fuel. Later, having obtained for us the excellent work of Mr. Bruno Kerl, professor in Berlin, on saltworks, we found in it a description of Mr. Rittinger's tests on the use of steam. By using a pump to suck in the vapors coming from a heated salt water in a closed vessel, and then pumping them back into a double bottom enveloping the same vessel, he had succeeded in salting with a fuel saving of 75 %- But if his device confirmed the principle on which it was based, the difficulty of extracting the salt made it impractical. In a correspondence with Mr. Bruno Kerl, we informed him of our views on the use of vapors by means of the driving force we could dispose of.
He urged us to persevere in the path we had embarked upon, not doubting that our trials would eventually lead to a satisfactory result. He advised us to obtain the work of Mr. Waerth, where we would find new data on this question. We
We found there, in fact, the complete description of apparatuses, in which a suction and delivery pump was also used as the main engine for the use of the vapors. But, instead of discharging them into a double bottom, enveloping the vessel from which they were sucked, the discharge was made into another vessel, which made the extraction of salt easy in both devices.
We were about to establish something similar; our intention was to discharge the vapors sucked by a compressor, in a series of tubes arranged in the shape of a lyre, at the bottom of several stoves, until complete condensation. Our colleague, Mr. Payot, the engineer, had already drawn up plans and estimates in this sense, when Mr. Piccard, thinking that by combining suction and compression in the same apparatus, he would succeed in avoiding a large part of the loss of heat that occurs when separate vessels are used, proposed a system of boilers of a special construction. Our company, fearing the trial and error which are the ordinary companions of innovations, decided to deal with him, all the more easily because he guaranteed the performance and the good working order of his apparatus.
We must say, to his praise and that of Messrs. Weibel and Briquet, with whom he associated for this object, that these devices were built with meticulous care, that each part is well worked, and that they leave nothing to be desired in terms of good execution. The announced salt yield has been exceeded. Circumstances related to the phenomena that occur during the salination process have not yet allowed these devices to be used in a regular production. We hope that these engineers will succeed in overcoming the difficulties that they face, as they have already overcome those they have encountered on their way.
Professor Piccard himself will give you details about his devices that will certainly interest you.
The accounts of the Vaud government show how little the calculations of M. Demiéville deviated from the truth, when he told the Grand Council, in 1865, that the Bex salt mines caused an annual loss of 74,567 fr. 40 to our canton.
The salts produced to the State in 1865 Fr.280,312 25.
The salts produced for the Company in 1868 Fr.335,850 95
After the first year of operation of the present Company, i.e. December 31, 1868, the proceeds from the sale of salt had thus increased by Fr.55,838 70.
In 1875, the salts yielded 360.337 25, which compared to the 1865 yield of 280.312 25 shows that in ten years the annual product of
The total amount of salts increased by 80,025 as a result of the handing over of the salt mines to the private industry.
Thus, from their creation, our mines and saltworks have gone through three distinct periods. Twice they have been saved from complete abandonment; and, if they still exist today, to whom do they owe it? To science; to your
To those men of all ages who, in the silence of the cabinet, wrest from nature its secrets, and deliver to industry the materials with which it builds its monuments.
Honor therefore to science, and to you, Gentlemen, who cultivate it for the glory and prosperity of our dear country.
Bex, August 20, 1877.
Gypsum, anhydrite...and wines: the other resources of the Bex region
The Bex region has been known for centuries for its main natural resource, salt. Originally discovered by salt springs, this essential raw material was first extracted by evaporation of brines, then by drilling, water injection and precipitation by thermo-compression. But the region also produces another derivative of evaporites, gypsum (from the Greek "emplatein", coating) by calcination of gypsum, both rock and mineral testifying with the salt, anhydrite and sulfur of Sublin of a rich geological and mining heritage (Fig.1). This gypsum, visible at the outcrop unlike the anhydrite (and salt!) is also the mother rock of particular soils giving the vineyard, and even the wines, a specific terroir character.