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     He was three years old when he lost his father while at the Jesuit School in Alicante. He began to learn how to read and write under the tutorship of his uncle, don Antonio Juan, a Canon at the Collegiate Church. A little later the other uncle on his father's side, don Cipriano Juan, a Knight of the Order of Malta, who was Bailío* de Caspe at the time, took charge of his education and sent him to Saragossa to study grammar which then was preparatory education for other higher studies.

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La ciencia matemática era una de las materias más importantes en la educación de un guardiamarina del siglo XVIII. Madrid, Museo Naval Real Colegio de Guardias Marinas de San Fernando de Cádiz

      In 1729, at the age of sixteen, he returned to Spain to apply for the entry of the Royal Company of Marine Guards, the military naval school founded by Patiño in Cadiz in 1717. After a six month wait attending as an occasional student, he entered the Academy in 1730, where modern technical and scientific studies were taught with subjects such as geometry, trigonometry, astronomic observations, navigation, estimate calculation, hydrography, cartography, etc., during which time he completed his education in the humanities with further classes of drawing, music and dancing. He soon earned the reputation of being a privileged student and among his fellow students he was known by the sobriquet of Euclid.

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     All this must have influenced the education of young Jorge Juan who at the age of 21 finished his studies as a Marine Guard in 1734 after having sailed around the Mediterranean for three years participating in numerous expeditions for the punishment of pirates, in the campaign of Oran and in the squadron which went to Naples to set the then infant don Carlos on the throne, later to be Carlos III of Spain. Among other masters in the art of navigating was the Marquess of Mari, his captain from the Academy in Cadiz, and as his commanders, the Count of Clavija, the famous don Blas de Lezo, and don Juan José Navarro, later to become the Marquess of La Victoria.

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     An arc corresponding to a minor radius would logically be smaller than that of another larger radius, while their angles would be the same. These measurements would produce different values for the different arcs measured which would determine with precision the shape of the Earth.

     In the eighteenth century this problem, which had been the subject of study since the time of the Greeks, turned into a bitter controversy lasting for almost a century. It reached the point of determining whether it had the form of a melon, as academicians such as Cassini claimed, who in addition were supporters of Cartesian mechanics, or of the spherical watermelon, as was defended by Maupertius and others, such as Newton, Halley and Huygens who based this on the universal gravitation theory (the bodies weighed less at the Equator) or the experiences of the pendulum (it did not swing with the same frequency in different places). Almost the whole world, including Feijóo's enlightened Spain, was against the latter, and it would be this famous expedition that would settle the controversy in their favour.

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Medida de los tres primeros grados del meridiano en el hemisferio austral. Madrid, Museo Naval

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     Las tareas encomendadas eran muy diversas: llevar diario completo del viaje y de todas las medidas físicas y astronómicas, cálculos de longitud y latitud, levantar planos y cartas, descripción de puertos y fortificaciones, análisis de costumbres, estudios de botánica y mineralogía, y elaboración de un informe secreto sobre la situación política y social de los virreinatos, además de un control policíaco sobre los académicos franceses, dado que su paso por las colonias suponía obtener datos que caerían en manos de los ministros de Luis XV.

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     With all these instructions, on May 26, 1735 they left Cadiz in the company of the Marquess of Villagarcía, who had just been appointed Viceroy of Peru. Jorge Juan was on board the ship El Conquistador and Antonio de Ulloa on the frigate Incendio. They reached Cartagena de las Indias on July 7, but the French academicians did not arrive until November15, and via Guayaquil they set out together for Quito.

     It took them from 1736 until 1744 to measure the meridian degree due to the great difficulties which had to be overcome. They became known as "Los caballeros del punto fino"*. The system used consisted of a series of triangulations which required signs to be placed at chosen points or bases on plains and high peaks of 5,000 metres. The cities of Quito and Cuenca, three degrees apart, restricted the limits of the geometric measurement or triangulation; between the two the choice of vortices on either side of the great valley joining them was made easy by a parallel double chain of mountains.

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     Later, in 1748, Ulloa describes many of the difficulties and sufferings they had to overcome in his "Relación Histórica del Viaje a la América Meridional …"**: "Our common residence was inside the hut because the extreme cold and violent winds did not allow anything else since we were continuously enveloped in such a dense cloud that there was no freedom of vision … when the clouds engulfed us, our breathing was made difficult by a greater density, continuous fall of thick snowflakes or hail, violent winds and a feeling of continuous fear that either our living quarters would be uprooted throwing it and us into the nearby precipice or that the weight of ice and snow which accumulated on it in little time would cave in and bury us … and the mind was terrorised by the rocks which came crashing down when they became loose, and in their precipitation and fall they did not only cause the entire peak to shudder, but to sweep along with it all that happened to be in the way of the race …" (4).

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     Their prolonged stay was also affected by other incidents, such as those which occurred with President Araujo y Río regarding the delay of their pay and the delivery of the instruments, a matter giving rise to a prolonged controversy which the Viceroy Villagarcía endeavoured to smooth over. But the venture merited such sacrifices. From then on, with the exact knowledge of the form and magnitude of the Earth, it was possible to establish longitude and latitude correctly. In fact, Jorge Juan and Antonio de Ulloa prepared forty out of the one hundred modern maps of the world. Juan established 56,767,788 toesas as the value of the Meridian degree alongside the Equator in a calculation which was the most approximate of all. The metre became the measurement unit and as a result a decimal metric system was adopted universally.

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     After nine extremely hard years, they decided finally to return on different ships to make sure that at least one of the copies of the notes and calculations would reach its destination. At the port of El Callao they embarked on the French frigates Liz and Deliberance on October 22, 1744. Jorge Juan reached Brest on the Liz on October 31, 1745. Thence he made his way to Paris to talk about his work and verify some particularities observed by himself and Godin in their astronomical observations. He met the famous astronomers Marian, Clairaut and La Caille, authors of the formulae which he had employed so often. He also met Réaumur, who invented the thermometer, and other famous academicians who, together with La Condamine and Bourguer now back at their work, voted him in as corresponding member of the Royale Academie des Sciences.

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     When they both returned to Madrid, Felipe V had died, and they were received with indifference in the Admiralty and in the Foreign Ministry. Jorge Juan was tempted to ask for a posting with his Order of Malta, but Pizarro, general of the Armada and an old friend from Chile, presented them to the Marquess of La Ensenada who recognising their merits found them to be the ideal choice for the development of his naval and armament policy. This was the beginning of a period of fertile work and of friendship with the Marquess, which was to last to the end of their lives and remain unaltered even after Ensenada's fall.

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     The Observations by Jorge Juan raised certain objections as he accepted the Copernican system as evident while it was still rejected to a certain extent in Rome. But Padre Burriel, the Jesuit, defended his writings, and it was agreed that a preamble by Jorge Juan under the title of Estado de la Astronomía en Europa should appear in the second edition of 1773 to avoid censure.

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     The letters exchanged between Juan and Ensenada were written in a numerical code. Just as Ulloa before him, Jorge Juan became a member of the Royal Society in London shortly after his arrival for which his secret activity of industrial espionage was no obstacle. At the end of 18 months he was obliged to flee and reached the French coast disguised as a sailor, but not without managing to bring 50 naval technicians to Spain.

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     1749 is also the year in which the Disertación Histórica y Geográfica sobre el Meridiano de Demarcación entre los dominios de España y Portugal*by Ulloa and Juan was published. As a consequence of the knowledge acquired on his journey to America and the fact that the size of the earth was now known, it was possible scientifically to settle the question of determining the meridian indicated by Alexander VI as the demarcation for the discoveries of both nations* and still in the process of negotiation since the Treaty of Tordesillas.

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Fachada principal del Observatorio Astronómico de Cádiz

     In 1752 the King appointed Jorge Juan Director of the Academy of Marine Guards, a post of great responsibility, where he introduced the most advanced teaching of his time, appointing competent teachers and relegating those he did not consider capable. He founded the Astronomical Observatory in Cadiz,, which he equipped with the best devices of the period, and he maintained correspondence about his observations with the Academies of Paris, Berlin and London.

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     At this time his activity never flagged, and this is also a little known fact. He made over thirty journeys around Spain to gather information about subjects of all kinds. In addition to directing the construction of docks and organising arsenals, he supervised the felling of trees for the construction of ships and solved problems in the mines of Almadén and Linares, in the irrigation channels of Murcia and Aragón and at the cannon foundries in Santander; he established the bases for a modern cartography of Spain and his intercession was even required for setting up a Chair of Mathematics in Alicante. In June 1754 the King appointed him to the Junta General de Comercio y Moneda and he was put in charge of examining and adjusting various weights and values of the coinage.

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     At this time Jorge Juan founded the Asamblea Amistosa Literaria** in Cadiz, which he brought together at his home on Thursdays, where subjects of interest were discussed, in which scholars, such as Luis Godín, José Aranda, Gerardo Henay, Diego Porcel, José Infante, Francico Canibell, José Nájera, Francisco Iglesias, Pedro Virgili and José Carbonell participated. This was an attempt at forming a future Academy of Sciences, where Jorge Juan himself gave an account of his observations.

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    He analyses the dynamics of the ship, its stability, its relationship with the thrust of the waves, the stress to which the spars are subjected, etc., and all of this based on experience, because as he acknowledges: "The sailor, totally occupied by the risk, work and fatigue, has no rest for such a long, detailed study; and the scholar, who requires peace for contemplation, does not adapt to effort and extreme fatigue, the only masters which easily teach the results which would be almost impossible to discover in theory alone" (7). As soon as it was published, it was known and translated throughout Europe.

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     With the authority and independence of spirit characteristic of him, shortly before his death Jorge Juan wrote a harsh letter to Carlos III for his blind submission to the French model which he had rejected from the start. He forecast grave losses, which occurred at Trafalgar 32 years later when the light English ships, probably inspired by Juan's studies, eliminated the heavy, ancient Hispano-French fleet.

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     After completing his work in Cadiz, when he finally prepared his return to Madrid in September 1766, he was appointed Ambassador Extraordinary to the Court of Morocco by King Carlos III for a difficult political mission.

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     On his return to Madrid with the experience gained, he devoted himself to studying all kinds of matters at the request of the Ministries and the Council of Castile. As he was unanimously considered infallible, his opinion was required for the solution and study of arduous political questions. But in June 1768 he again had to find relief for the biliary colic in the waters and baths of Trillo. In 1770, finally, he was appointed Director of the Royal Seminary of Nobles, his last posting.

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     Jorge Juan died, it is said, of an epileptic attack on June 21, 1773 at the age of sixty years and six months. He was buried in the church of San Martín on the night of the 22nd. The news of his death appeared in the Gazeta de Madrid in its edition of Tuesday, the 6th of July. Six years later Benito Bails, a distinguished disciple of his, described him as follows:

     Don Jorge Juan was of medium height and strong build, of a pleasant and placid countenance, neatly dressed without affectations of person or lineage, ate frugally and, in short, his habits were those of a Christian philosopher. When he was asked a scientific question, he appeared to behave as if it were he himself who was looking for the explanation. When he was asked for a report about some matter, he sought the information first, then he meditated and finally he replied. He maintained his opinion as a consequence of his mature thoughts. He did not judge men in view of the place from where they came; he was the champion, almost the agent of all useful men.(8)