THEMATIC ROUTES

RT- 6
GREEN MERIDIAN ROUTE
(Ruta del Meridià Verd)


Dunkerque - Paris - Barcelona

Introduction

In 1998, the 200th anniversary of the creation of the metre was commemorated. The length chosen for it was the length of a section of an arch of a terrestrian meridian, specifically the meridian 002º20'14'', then called meridian 0 (or of Paris), that begins in Dunkerque and ends in Barcelona (although the real end is in the village of El Masnou).

It is obvious that, in order to take this decision, the French parliament estimated different possibilities and several ways to determine this new measure ("metre" from the Greek word "metron").

But the idea of creating what lately was called "Decimal Metrical system" was much older. It was by the end of the previous century, in 1670, when the vicar of the parish of Sant Pau of Lyon, Gabriel Montou, ideated a universal measure, unique and based in nature. He proposed a decimal system based in the length of an arch of a meridian, that is an angle of a minute.

When looking for antecedents of this decision, there must be taken into account the Benedictine monk Gerbert d'Orlhac, who became the Pope Silvestre II. His contribution, in the 10th century, was the assumption and broadcasting of the number zero in the numerical European system.

It is obvious that this contribution was not intentionally related with the determination of the length of the metre, but it helped that mathematicians had enough knowledge in order to realise those measures. In the same way, it is also evident that, without this contribution, the binary system (1-0) could not exist about a thousand years later, and computers and any other software systems could not exist.

Gerbert d'Orlhac (938 [?]-1003) was born in Auvergne, Aquitania, and was a monk of the monastery of Saint-Géraud d'Orlhac. But he studied mathematics, astronomy, and other sciences, in Vic, Ripoll and Barcelona, thanks to the relationship that the Spanish culture had with the Moslem culture, because they were who really introduced the concept of number zero, as well as many other things, especially those related with agriculture, medicine, etc.

Green Meridian Route

In the year 2000, several French and Catalan civic-minded associations, with the support of the administrations of both countries, organised several activities to commemorate the 200th anniversary of the establishment of the Decimal Metrical System and the measurement of the longitude of the meridian Dunkerque - Paris - Barcelona.


Altimetrical plaque in the façade of the CEC.
(Photography by: J.M. Jerez)
Among those activities, it is necessary to emphasize the planting of thousands of trees along this imaginary line in France and several walkings organised by the Centre Excursionista de Catalunya lin the most significative points of the geography of Catalonia that were used as geodesical vertex of the measurement. They put up several commemorative plaques in several places (Montjuïc castle, Rellotge tower in the Pescadors harbour, and in the central office of the CEC in Barcelona, Alella, Tarragona, in the peak of the Puigsacalm, etc). See the magazine "Muntanya" of the CEC, number 797 (February 1995).

In order to give a future prospection to this event, as well as to a reunion perspective with nature, several authorities accorded to rename it as Meridià Verd (Green Meridian). One of the proposals was to arrange and mark a route as close as possible to the historic meridian of Paris that was able to be integrated in the net of mountain routes of the country.
The route in Catalonia begins in Coll de Pal, next to the peak of the Costabona, in the Pyrenean crest, and ends in Masnou, next to the sea. The beginning and ending places are very specific, but the route has to follow paths and roads, what makes almost impossible to follow exactly the straight line by which the meridian goes on, although this was the main aim when designing the route.

In some specific places, because of the characteristics of the land, it is not possible to go by mountain bike. Those users have some alternative routes called special variants (not marked).

Historical origins

Nowadays, to measure lengths we use the metre and its dividings (decimetres, centimetres, and milimetres). It seem that those measures have existed for ever, but they are only 200 years old.
By the Desember 10th, 1799 Act, the measure called "metre" was born but, from where does its length come from? The history of the determination of this length is as complex as exciting, and an important part of it happened in Catalonia.
In the past, other measures were used, as the stick, measures that had different lengths according to the different places. In front of this confusion, different governments and monarchies tried to unify them.
The scientific advances in the 18th century, especially in the fields of geography, optics, geometry and astronomy, motivated the serious study in order to search a universal unit of measurement based in a geographical dimension, like the terrestrial meridian.
Everything began in 1790. In the framework of the radical changes that the French revolutionaries wanted to introduce in laws and usages of the ancién régime, the bishop Carlos Mauricio of Talleyrand proposed in front of the French National Assembly a really revolutionary proposal.
In France, there was the constant request of an estate unification and control of the different measurements used in every city and region of the country. The several abuses and scandals, more than the diversity of measurements, made unbearable a chaotic measure system, but only a revolution could change the ancient feudal order.
Talleyrand, an skilfull politician, proposed a measure system absolutely new, based in nature in order to be against nobody, an standard that could be accepted by any nation (especially England), and perfect to become a universal measure. The chosen pattern was the length of a pendulum oscillating at intervals of one second at 45 degrees.
His proposal was approved by the French National Assembly in May 8th, 1790, and the king Louis XVI formally invited the king of England to collaborate in the determination of this new measure.
England did not answer. France was alone in its trying to create the universal measure and tried another way. In March 19, 1791, the Science Academy of Paris proposed the substitution of the pendulum by another measure from nature. The metre could be the ten-million part of the quadrant of a terrestrial meridian. In March 26th, the National Assembly approved the change and the new measure project, that need the help of almost all the members of the institution.

The new unit was called METRE (from the Greek metron, that means "measure") and was parted in decimal fractions: the decimetre (the tenth part of the metre), the centimetre (a hundreth part of the metre) and the milimetre (a thousandth part of the metre).

In front of the impossibility to measure a quarter part of the meridian, from the North Pole to the equator, the answer was to measure a part and to calculate the total value. The arch tried was the one between Dunkerque, near the North sea, and Barcelona, in the Mediterranean coast of the Iberian peninsule.

Why Barcelona?

The March 19th report widely explains the convenience of placing the inferior end of the arch in Barcelona. The most important reasons are scientific: to choose as the basic meridian the one that passes by the observatory of Paris, repeteadly measured in France, both ends were at the sea level, and the meridian of Paris touched the sea in Barcelona. Barcelona, in addition, was far enough of the Pyrenees in order that its high could not affect the direction of the vertical. The mid point of the arch was placed near the parallel 45 if the measurement was inside France, what gave several advantages in the final reckoning.
But, as some important scientific said, those reasons were mere non-scientifical justifications. The expected mistakes in such a complicated calculation prevented from the pretended exactitude. There were other extra-scientific reasons behind. As several journals said, this operative hided an attempt of the Sciences Academy to show its validity as the real basic scientific entity in a country where its dissolution was planned from a long time ago. Another use of the measure of this arch was that to include Barcelona will give internationality to the new measure, it would not be only French. Spain, apart from England, was a really important nation in Europe, and its participation would be determinant.
The decision had been taken. March 30th, 1791, a dispossessed of power Louis XVI signed the project of the Science Academy and encharged the topographers Pierre François André Méchain and Jean Baptiste Joseph Delambre to measure the meridian.
Delambre measured from Dunkerque to Rodez, and Méchain measured the rest.

The used technique was the geodesical triangulation. They drew several triangles (its vertexs were some of the mountains placed along the meridian) and calculated their dimensions by measuring 2 basis (or lengths between 6 and 10 km), by using the called "Academy toesa", the measure that had to be substituted by the metre.
They had to decide which mountains they had to use, climb to those mountains and measure from there the angles made by the neighbour peaks. Méchain began by the Spanish side. In April 22nd, 1792, Charles IV, king of Spain, accepted the French proposal and appointed two civil mathematicians: José Chaix, vice-director of the observatory of Madrid, and Juan de Peñalver, together with the sailors José González, the captain of the brig "Corzo", and Francisco Planes, Miguel Bueno and Miguel Alvarez.

The measurement in Catalonia

Méchain arrived to Barcelona in July 10th, 1792. He and Gonzáled stablished the work methodology. They chose the necessary mountains between Barcelona and the Pyrenees that had to be the vertexs of the Catalan triangles and discussed a new project that the Spanish members proposed to the French astronomer: if the arch ended in Majorca instead of Barcelona, its mid point was much more exactly on the parallel 45. To accept this proposal meant to go down to the South, chose more mountains and draw new triangles, and to go to Majorca to make an internal triangulation in the Balearic islands.
This lengthening idea was proposed by the sailor and astronomer José de Mendoza, who was in Paris and who went with the members of the Academy who were preparing the new metrical system.
Méchain did not have the authorization for this enlargement when he arrived to Spain. But he received it by letter of the French National Convention by October 27th, 1792. Until then, France and Spain had approved the triangles and began to measure them. Those triangles were in the peaks of the Calmelles, Mare de Déu del Mont, Puigsacalm, Rocacorba, Puig Rodó, Matagalls, Montserrat, Mont Mates, Vallvidrera, Santa Creu de l'Olorde and Montjuïc, the most eastern point of the first projects, in the outskirts of Barcelona, where Méchain arrived by October 29th.


Castle of Montjuïc in Barcelona. (Photography by: J. M. Jerez)

Méchain arrived to Barcelona in July 10th, 1792. He and Gonzáled stablished the work methodology. They chose the necessary mountains between Barcelona and the Pyrenees that had to be the vertexs of the Catalan triangles and discussed a new project that the Spanish members proposed to the French astronomer: if the arch ended in Majorca instead of Barcelona, its mid point was much more exactly on the parallel 45. To accept this proposal meant to go down to the South, chose more mountains and draw new triangles, and to go to Majorca to make an internal triangulation in the Balearic islands.
This lengthening idea was proposed by the sailor and astronomer José de Mendoza, who was in Paris and who went with the members of the Academy who were preparing the new metrical system.
Méchain did not have the authorization for this enlargement when he arrived to Spain. But he received it by letter of the French National Convention by October 27th, 1792. Until then, France and Spain had approved the triangles and began to measure them. Those triangles were in the peaks of the Calmelles, Mare de Déu del Mont, Puigsacalm, Rocacorba, Puig Rodó, Matagalls, Montserrat, Mont Mates, Vallvidrera, Santa Creu de l'Olorde and Montjuïc, the most eastern point of the first projects, in the outskirts of Barcelona, where Méchain arrived by October 29th.
Méchain began measuring the azimuth of one of the last triangles' side, and the latitude of one point, in the moat of the castle of Montjuïc, the eastern side of the arch. After those first measurements, he came back with González, who was the virtual operations director in the Spanish side, and with the rest of the scientifics to the northern stations in order to finish the measure of the angles between the vertexs of the established triangles.
Once all expeditionaries had come back, in Desember 1792, González went to Majorca in his ship in order to decide which mountains had to been used and to put light in them (a combination of mirrors and fire), in order than Méchain could check if the measure was possible.
From the top of the Puig Major of Majorca, in Desember 16th, González lighted a fire towards Montjuïc, a light that Méchain could see with his telescope but not with the glasses to measure angles. Méchain decided that, with his instruments, it was not possible the geodesical union of the Balearic islands and the Catalan coast, in the north of Barcelona. The astronomer finished all the operations of determining the latitude of Montjuïc, and he prepared himself to go back to France.
But an unexpected event altered his plans. In January 21st, 1793, Louis XVI was guillotined in Paris, and the war was going to start between France and Spain. The General Captain of Catalonia allowed him to continue his studies in Catalonia but he could not go near the border, in order than his activities at the tops of the mountains could not be interpreted as espionage.
Méchain could do nothing, so he diverted himself by doing several astronomical observations, like the lunar eclipse of February 25th, 1793, and by visiting several Catalan intellectuals. He sent one of his most trustful collaborators, Tranchot (a geographical engineer) to the southern mountains in order to look for a better place to unite with the Balearic islands. It was during one of this visits to a doctor's house (maybe Francesc Santpons i Roca), in order to wacth how a machine worked, that Méchain suffered a serious accident that obliged him to rest in bed for five months.
The war against France, declared in March 7th, went on; but Méchain got permission to finish the border stations, but not to go back to France. Meanwhile, Tranchot, risking his life, crossed the border in order to prepare the French stations to connect all the triangulations.
In November 3rd, 1793, the last measurements in Catalonia finshed. In this year, the provisional pattern was built, using incomplete data. Two years later, in 1795, France took oficially the measure system based in the metre.

Once back to Barcelona, and in front of the impossibility to go back to his country nor having access to the castle of Montjuïc (a militar area in war time), Méchain entertain himself calculating the latitude of his balcony in the Fontana d'Or, placed in the Escudellers street. By means of a small chain of geodesical triangles, he tried to connect his balcony with his first observation point in Montjuïc and try to check the lately determined latitude. The discrepancy between both measures, about 3 seconds of arch, was not notified by Méchain to the comission, and his decision was severely criticized.

By the end of 1794, the appointment of a new General Captain, much more favorable, allowed Méchain to leave Catalonia towards Italy, from where he came back to France. The astronomer stopped in Marseille, where he stayed for about half a year because of several excuses. From there, and before going back to Paris, deeply affected by revolution and terror, Méchain went to the French side of the Pyrenees in order to finish the chain of triangles. He spent almost three years in his measurements from the tops of the Puig de Calmelles and the Puy de l'Estella, last Spanish stations and the first French one, until Rodez. Finally, even Delambre had to travel to the south in order to measure a comprovation base in Perpignan. Finally, Méchain and Delambre met in Carcassone and, together, they came back to Paris by the end of August, 1798, with several data of the measures made between Barcelona and Dunkerque. In November, the delegations of the countries that accepted Talleyrand's invitation met for the very first time in order to help in the needed calculations in order to determine the new metrical system. Among those delegates, there could be found Gabriel Ciscar and Agustín de Pedrayes. For six months, those calculums were made in order to mathematically determine the exact measure, as well as measures for capacity and weight (litre and kilogramme). Finally, in June 22nd, 1799, the representant of Holland, Van Swinden, read in front of the rest of the delegates the final conclusions. After long sessions and some not very justified decisions, they decided that a metre will measure 3 feet, 11 lines and 296 thousandths of line, almost 0.32 milimetres less than the one calculated in 1795. A French "toesa" will measure 1, 9490366 metres.

An Act passed by Frimario 19th of the year 8 of the French Republic (Desember 10th, 1799), signed by the French first consul, Napoleon Bonaparte established it with the following lema "For all the people, for any time". The definitive measure for the metre, and the new Metrical Decimal System were born.

Verification of the accuracy of the metre

In Van Swinden's report, there cannot be seen than the Catalan operations have finished. According to Méchain's plans to enlarge the measure until Cabrera, Van Swinden said: "... We expect that more favourable circumstances allowed the execution of what could not be done by now."
Those circumstances came in 1802. In the minutes of the Bureau des Longitudes, the French organization in charge of astronomy and geodesics, in August 31st, 1802, there can be found the news that one of its members, not identified, wants to continue the geodesical operations in Spain. Méchain, who was capitain concierge (or responsible of the observatory of Paris) by that time, was invited to give his opinion. In a report addressed to the Home Secretary, there was the proposal of arriving to Ibiza, going down by the Catalan mountains until Tortosa in order to find the points from where it was possible to find this island. This proposal was justified by the intention of being as much exact as possible. By the same time, and although the reticences of other astronomers (who wanted a younger man), Méchain asked to lead this expedition.
In October 13th, 1802, Méchain received the order to travel to Barcelona and to the Balearic islands. He asked for the permission and collaboration of the king of Spain. Once this permission was achieved, Méchain prepared himself to travel to Barcelona. In May 1803, after a pleasant trip, he arrived to Barcelona with three companions and was ready to compliment the General Captain of Catalonia, the Count of Santa Clara.


Observatory of Paris, 18th century

If his first trip was full of favourable conditions, in this one everything was delays. The General Captain did not received orders from Madrid; the promised ship (under the orders of Enrile) was in Cartagena, and the good weather for shipping was going by. Méchain, desperate, wrote to his ambassador in Madrid to ask him if he could facilitate all the procedures. In August 17th, 1803, Méchain could observe from Tortosa a solar eclipse. He climbed all the highest southern mountains in order if he could see the Balearic islands.
He did not have enough means to go to the Balearic islands, so he began a series of measurements of triangles during September and October 1803. From the area of the Montsià, in south side of the river Ebro, he went to Llaberia (north of Tortosa), Sant Joan (near Altafulla), the Puig de la Morella (in the massif of the Garraf) and, finally, at the top of Montserrat, an old station that allowed the connection of measurements with the ones made in the last expedition.
Meanwhile, Enrile's ship, who was near Barcelona, was turn aside to Menorca in a quarantine of the yellow fever. Méchain tried to get a new ship, but he could not. Chaix, tired, came back to Madrid, and the French astronomer accepted the help of a friar Mathematics professor from Barcelona, called Agustí Canelles, as well as the help of a noble man from Valencia, astronomer amateur, called Faust Vallés i Vega, 12th Baron of the Pobla Tornesa and la Serra d'en Galceran.
Méchain could do anything, so he decided to go to Valencia in order to know if, from its mountains, it was much easier to see the Balearic islands. With the Baron, they both climbed to one of the Baron's properties, the massif of the Desert de les Palmes, in the north side of Castellón, from where Ibiza can be seen. Méchain rested in the Baron's houses until he got another ship. Méchain came back to Barcelona, and in January 8th, 1804, he shipped to Ibiza, where he arrived in January 15th.
When he climbed to the Ibizan mountains, he confirmed the high dificulty to see the Catalan coast. He had two options: on one hand, to link the Balearic islands through Majorca in a big triangle based in Montsià, Desert de les Palmes and Puig Major and, from there, draw an internal triangle in the islands; on the other hand, to go by Ibiza, down the coast of Valencia until Cullera and Dénia. When he climbed to the Puig Major, he finally decided to proceed according to the first option.
But, answering his requests, the Bureau des Longitudes ordered him to proceed according to the second option.
Méchain, exhausted, did not dare to contradict his partners of Paris, so he ship to Valencia, where he arrived by the end of April 1804. He rested in the Baron's house, measure several latitudes, and searched for the perfect place in the Albufera to measure the base of the triangle. Later on, he climbed to several other mountains trying to find the perfect place.
Once those stations were decided, Méchain came back to Cullera in order to begin with the measurements, but he discovered that from the highest place near the village, it was really difficult to see Ibizan mountains. He began to measure the coast crest, where he contracted the malaria because of the mosquitos. In Espadan he fell ill, and he was descended to Castellón, in the Baron's house, where Méchain died in the Baron's arms in September 20th, 1804.
Méchain, one of the most glorious French astronomer, is buried in the cemetery of Castellón. A scientific trip, transformed in an impressive and unlucky adventure, finished in this moment. His helpers went back to France with most of the instruments and notes, leaving others if a reprisal was possible.


Continuation of Méchain's works

If, in 1802, it was quite interesting to check the metre's exactitude, in 1806 this problem was irrelevant. The problems of the metre were more of implementation than of exactitude. The scientific world had assimilated that the Earth was not a perfect ellipse, that not all meridians are not the same and that the legal metre was just the distance between two lines.
The scientific problem of those days was to measure correctly the arches of the Earth. In this environment, Laplace, the most influent scientific of France, directly asked to the Emperor Napoleon the continuation of the measurements of Méchain in Catalonia in order to enlarge the meridian of Paris

This proposal was accepted, and the Emperor appointed Jean Baptiste Biot, an important scientific, and Jean François Dominique Aragó, from Estagel, a young secretary of the observatory of Paris, who could speak Catalan, in order to continue Méchain's works. In September 20th, 1806, two years after Méchain's death, they arrived to Barcelona, together with a Spanish Mathematician who was in Paris called José Rodríguez González. They interviewed with the count of Santa Clara, they received the necessary permissions and continued travelling to Tarragona and Valencia.



Mola de s'Esclop (926 m) serra de Tramuntana (Mallorca)



Ruins of a hut used by François Aragó at the top of the Mola de s'Esclop

In Valencia, they met José Chaix, reassigned to this operation, who, for about two years, covered the southern Catalan mountains, as well as in Valencia and in the Balearic islands, in another really interesting scientific and human adventure that will be explained by Aragó, by the end of his life, in this book "History of my Youth". They wanted to enlarge the meridian of Paris from Barcelona to the island of Formentera and to check that there was only 2 milimetres of difference with the previous measure.
During the 19th century, several countries implemented the new Metrical System, but few of them adopted it in the real life. In Spain, the Metrical System was legally implemented by the April 15th, 1848 Act, and was compulsory from January 1860. But, although all those acts, almost everybody used the same measure units as before.
For the second half of the 19th century, both systems lived together and, slowly, mainly because of education and of the unifying advantages of the new system, it was definitively used in almost all fields.

Barcelona, Montjuïc, the Catalan, Valencian and Balearic mountains, and most of its most characteristic places belong to the metre's history. For most of the Catalan people, the only memory are the names of two streets: Meridian avenue and the Parallel.



Information about some of the Catalan collaborators of the French scientifics who measure the meridian.

Canelles i Carreres, Agustí
Ciscar i Ciscar, Gabriel
Chaix Isniel, Josep
de Martí i Franquès, Antoni
Salvà Campillo, Francesc
Santponç i Roca, Francesc
Vallés i Vega, Faust


Commemorative acts of the measure of the meridian of Paris

By the foot of the geodesical vertex placed at the top of the Puigsacalm, there is a commemorative plaque of the 200 anniversary of the measure.


In Ocata beach, in El Masnou, in September 23rd, 2003, commemorative sign that places the meridian of Paris in this point.

Also in September 23rd there was the presentation of the Green Meridian route's guide there.
Photos: J.M. Jerez

 



In the Torre del Rellotge, in the Pescadors harbour of La Barceloneta (Barcelona) there is a commemorative plaque from 1999 of the 200 anniversary of the measure. (Photography by: J. M. Jerez).


Castle of Montjuïc (Barcelona)

There is a commemorative plaque of the 200 anniversary of the measure in the tower that was the base for the flag. (Photography by: J. M. Jerez).

The work of Valérie Berjeron "La talla mètrica de la natura" ("The metrical woodwork of nature"), that links the lineal metre to its natural time.
In the north-eastern side of the moat of the castle, with a wonderful view over the sea, around a concrete tower of 9 metres high, there are three different kinds of trees: an ilex (Quercus suber), an apricot-tree (Prunus armeniaca) and a white poplar (Populus alba bolleana). (Photography by: J. M. Jerez).


In the centre of the Plaça de les Glòries Catalanes there is a memorial to the meridian, a work of the French sculptors François Scali and Alain Domingo, that represent the most significative lengths and highs of the meridian of Paris. (Photography by: J. M. Jerez).

In the village of Vallfogona de Ripollès, there is a parade with a monolith dedicated to the Green Meridian. (Photography by: J. M. Jerez).

Marks of the route of the Green Meridian



Explicative soffit of the meridian placed in the south of the Serra Cavallera.
(Photography by: Jordi Embodas)
 


Vertical mark of the route.
(Photography by: J.M. Jerez)



Horizontal mark of the route. (Photography by: J.M. Jerez).


Marks in stickers in urban places.

Links related with the meridian of Paris

The metre in Catalonia
http://www.uv.es/~ten/metro.htm

The metre in Barcelona
http://www.astrogea.org/ipa/galeria/bcnmetro/index.html

The Green Meridian in France
http://www.icilacreuse.com/carte/meridien/
http://www.ville-rungis.fr/corps_merid.htm#paris
http://www.apgi.net/andouque/nouveaut.htm
http://www.ac-clermont.fr/actualit/pedago/2000france/piquenique.htm
http://www.chez.com/t3m/doc-douzet-meridien-zero.htm
http://saint.martin95.free.fr/lameridienneverte.html
http://smdsi.quartier-rural.org/meridiv/meridiv.html
http://perso.wanadoo.fr/arverne.03/huriel/meridienne.html
http://www.espace-ecoles.com/animation/info/la_meridienne_verte.htm
http://www.aude.pref.gouv.fr/actualite/act-br-meridienne.htm
http://www.obs-nice.fr/bijaoui/Arago/sld082.htm
http://gallica.bnf.fr/anthologie/notices/00414.htm

A metre of history
http://www.el-mundo.es/larevista/num184/textos/metro1.html

Department of Metrology
http://www.metrologia.csic.es/defmetro.HTML

Records of the metre
http://www.culturaclasica.com/cultura/sistema_metrico.htm









Introduction

Historical origins

Why Barcelona?

The measurement in Catalonia

Verification of the accuracy of the metre

Continuation of Méchain's works

Information about some of the Catalan collaborators of the French scientifics who measure the meridian

Commemorative acts of the measure of the meridian of Paris

Marks of the route of the Green Meridian

Links

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