João de Castro
Encyclopedia
Dom
João de Castro (February 7, 1500 – June 6, 1548) was a Portuguese
naval officer and fourth viceroy of Portuguese India. He was called Castro Forte ("Strong Castro") by poet Luís de Camões
. Castro was the son of Álvaro de Castro
, civil governor of Lisbon
. His wife was Leonor de Coutinho.
, and studied mathematics
under Pedro Nunes
, in company with Louis, Duke of Beja, son of king Manuel I of Portugal
, with whom he contracted a lifelong friendship. At eighteen he went to Tangier
, where he was dubbed knight by Duarte de Menezes
the governor, and there he remained several years.
. Returning to Lisbon, he received from the king the small commandership of São Paulo de Salvaterra in 1538.
Soon after this he left for India in company with his uncle Garcia de Noronha, and on his arrival at Goa
went off for the relief of Diu
. In 1540 he served on an expedition to Suez
under Estêvão da Gama (the son of Vasco da Gama
and them viceroy of Portuguese India), by whom his son, Álvaro de Castro, a child of thirteen, was knighted, out of compliment to him. Died D. Garcia, succeeded him in the government D. Estevao da Gama, and D. João de Castro was found with him in the expedition to the Red Sea. D. Estevão da Gama went with 12 large galleons and carracks, and 60 galleys, on December 31, 1540, being D. João de Castro captain of a galleon. This expedition to Suez was truly remarkable, and João de Castro made a detailed roadmap of it, with maps, calculations, pictures and detailed notes from the coasts of the Arabian Peninsula
as of those of the countries of today Somalia
, Eritrea
, Ethiopia
, Sudan
and Egypt
, as far to Suez and to several ports in the shores of the Sinai Peninsula
, all included in the Roteiro do Mar Roxo, which offered to the Prince Louis. Eight months later he returned to Goa on August 21, having acquired by the experiences made during the expedition, the name of the philosopher. "I pay great attention to eclipses of the moon," he writes, as also to longitudes and latitudes, fishes, seaweeds, currents, winds,the colour of the Red Sea, and every detail that might concern the art of navigation, to the delight of his friends Pedro Nunes and Prince Louis, who had furnished him with special instruments and other assistance for his voyage.
D. João de Castro called for the need of the coordination between the observation and reason, in the case of the navigation: "This science of navigation is poorly distributed among the men, or because they act like idiots, which for a long time and continuous exercise they reach many particulars, though with all their works are never to gain authority in their office, or those who have no experience, but with much learning and great practice in the science of mathematics, reached the shadow of this art but not the true science."
It is in overcoming this divorce that rooted the ways of science, which reaches an understanding with no epilogue, an open knowledge, in constant motion approach, not compatible with the spirit of the system. João de Castro tell us that the knowledge of science is "come to the truth", that science is "closer to the truth and not the absolute truth": "We need to consider how much we owe for teaching us how not to ignore the fact that we can be closer to the truth, as are human things that men can learn (...). Not only to be expected by virtue of reaching the truth, but also get close to her."
an seas of pirates; and in 1545 he was sent, with six sail, to India, to assist Martim Afonso de Sousa
, who had been dismissed of the viceroyalty. Seconded by his sons (one of whom, Fernão, was killed before Diu) and by João Mascarenhas, João de Castro achieved such popularity by the overthrow of Mahmud, king of Gujarat, by the relief of Diu, and by the defeat of the great army of the Adil Khan
, that he could contract a very large loan with the Goa merchants. These deeds were followed by the capture of Broach
, by the complete subjugation of Malacca
, and by the passage of António Moniz into Ceylon; and, in 1547, by the appointement as viceroy by king John III of Portugal
.
After the victory of his Armada in the refief of Diu, he besought the King not to prolong his term of office beyond the ordinary three years, and to allow him to return to the Serra de Sintra
, and in his will he says: "I have near Cintra a quinta, called the Quinta of the King's Fountain, which I made, and to which I am greatly devoted because I made it and because it is in a country where my father and ancestors were born". After his victory over the overwhelming odds of Mahmud and of the Adil Khan, D. João de Castro set about rebuilding Diu, and to obtain money sent an appeal to the citizens of Goa with some hairs of his beard in pawn since it was impossible to send the bones of his son, as he had first intended, his death being but recent. The citizens of Goa responded nobly to the appeal, and when the Governor returned to Goa in the spring of 1547. they received him with great rejoicing. His triumph ceremony has been often described in the chronicles and tapestry.
He addressed the chief officials and magistrates of Goa: "I am not asham'd, gentlemen, to tell you that the Vice Roy of India wants in this sickness those conveniences the meanest souldier finds in the Hospitals. I came to Serve not to traffick in the East, I would to your selves have pawn'd the bones of my Son and did pawn the hairs of my beard to assure you I had no other plate or hangings in the house to buy me a hen, for in the fleets I set forth the souldiers fed upon the Governour's salary before the King's pay, and 'tis no wonder for the father of so many children to be poor. I request of you during the time of this sickness to order me out of the king's revenue a proportionable maintenance and to appoint a person of your own who may provide
me a moderate allowance."
He did not live long to fill this charge, dying in the arms of his friend, Saint Francis Xavier
, on 6 June 1548. He was buried at Goa, but his remains were afterwards exhumed and conveyed to Portugal, to be reinterred under a splendid monument in the convent of Benfica
. The chronicler Diogo do Couto
ends his portrait of the Viceroy thus: "And for his great charity, temperance, disinterestedness, exceeding love of God, and other qualities of a good Christian, it may be affirmed that he will be receiving in glory the prize and guerdon of all his trouble and toil." And for the author Aubrey Fitz Gerald Bell: "by his energy, vigour of thought and action, by his splendid character, humane and resolute, he closed the most briliant half-century of Portugal's history with a key of gold."
. At the time of the great sailing, the navigators could not find a ship at sea by the two coordinates, latitude and longitude, the determination of this required a clock on board to indicate the exact time at the meridian of reference, and the astronomical determination of longitude gave unacceptable errors. During the trip to India, D. João de Castro has carried out a series of experiments that succeeded in detecting the phenomena, in particular related to magnetism and the magnetic needle on board. It should be assumed that such knowledge comes from Pedro Nunes
, of course the direct inspiration of all the observations he has done in his travels. When on August 5, 1538, D. João de Castro decided to determine the latitude of Mozambique, found the cause that dictated the astonishing uneasiness of needles; noted the deviation of the needle, discovering it 128 years before Guillaume Dennis (1666) of Nieppe, which is recorded in history of sailing as if he were the first to know about this phenomenon. His observation near Baçaim, on December 22, 1538, of a magnetic phenomenon, for which there were variations of the needle because of the proximity of certain rocks, confirmed four centuries later, called local attraction. D. João de Castro refuted the theory that the variation of magnetic declination is not formed by geographic meridians.
To the words of Pedro Nunes expressed in De Crepusculis, which refers the things he had discovered, meditating and investigating, that nowhere he had read before and wouldn't have credit if they were not shown, we can associate the words of D. João de Castro in its Roadmap (Roteiro) of Lisbon to Goa: "in this written script many things that will seem strange and impossible, which I wrote fearfully, not because of them were not very certificate, but for fear that I had to out of the common opinion. "
The comments made by João de Castro are the most important record of values of magnetic declination in the Atlantic and Indian
oceans, in the sixteenth century, and useful for the study of terrestrial magnetism. He made 43 determination of magnetic declination through rigorous measurements of geomagnetic declination over the entire circum-Africa route. The instrument used by him was the Bussola de Variacão, also developed by Felipe Guillen a decade earlier in Seville. João de Castro undertook many observations and can in a way be considered as one of the discoverers of crustal magnetism. He discovered spatial variations of Declination in that Bay of Bombay (near Baçaim), which he attributed to the disturbing effects of underwater rock masses (this is near where the large basaltic and rather strongly magnetized Deccan traps outcrop).
In the 1890s, G. Hellman, quoted by Chapman and Bartels (1940), considered Castro to be the most important representative of scientific maritime investigations of the time, and the method he tested was universally introduced on ships and was used until the end of the sixteenth century. It was one of the personalities of this century of European experimental science, linking the importance of this study with the sailing. His name was linked to science for his works which showed a trend for modern scientific spirit.
Don (honorific)
Don, from Latin dominus, is an honorific in Spanish , Portuguese , and Italian . The female equivalent is Doña , Dona , and Donna , abbreviated "Dª" or simply "D."-Usage:...
João de Castro (February 7, 1500 – June 6, 1548) was a Portuguese
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
naval officer and fourth viceroy of Portuguese India. He was called Castro Forte ("Strong Castro") by poet Luís de Camões
Luís de Camões
Luís Vaz de Camões is considered Portugal's and the Portuguese language's greatest poet. His mastery of verse has been compared to that of Shakespeare, Vondel, Homer, Virgil and Dante. He wrote a considerable amount of lyrical poetry and drama but is best remembered for his epic work Os Lusíadas...
. Castro was the son of Álvaro de Castro
Álvaro de Castro
Álvaro Xavier de Castro was Prime Minister of Portugal from November 20 to November 30, 1920 and from December 18, 1923 to July 6, 1924.-Early career:...
, civil governor of Lisbon
Lisbon
Lisbon is the capital city and largest city of Portugal with a population of 545,245 within its administrative limits on a land area of . The urban area of Lisbon extends beyond the administrative city limits with a population of 3 million on an area of , making it the 9th most populous urban...
. His wife was Leonor de Coutinho.
Early life
A younger son, and destined therefore for the church, he became at an early age a brilliant humanistHumanism
Humanism is an approach in study, philosophy, world view or practice that focuses on human values and concerns. In philosophy and social science, humanism is a perspective which affirms some notion of human nature, and is contrasted with anti-humanism....
, and studied mathematics
Mathematics
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
under Pedro Nunes
Pedro Nunes
Pedro Nunes , was a Portuguese mathematician, cosmographer, and professor, from a New Christian family. Nunes, considered to be one of the greatest mathematicians of his time , is best known for his contributions in the technical field of navigation, which was crucial to the Portuguese period of...
, in company with Louis, Duke of Beja, son of king Manuel I of Portugal
Manuel I of Portugal
Manuel I , the Fortunate , 14th king of Portugal and the Algarves was the son of Infante Ferdinand, Duke of Viseu, , by his wife, Infanta Beatrice of Portugal...
, with whom he contracted a lifelong friendship. At eighteen he went to Tangier
Tangier
Tangier, also Tangiers is a city in northern Morocco with a population of about 700,000 . It lies on the North African coast at the western entrance to the Strait of Gibraltar where the Mediterranean meets the Atlantic Ocean off Cape Spartel...
, where he was dubbed knight by Duarte de Menezes
Duarte de Menezes
Dom Duarte de Menezes , was a 16th C. Portuguese nobleman and colonial officer, governor of Tangier from 1508 to 1521 and 1536 to 1539 and governor of Portuguese India from 1522 to 1524.- Background :...
the governor, and there he remained several years.
Voyages to India and the expedition to Egypt
In 1535 he accompanied Dom Louis to the siege of Tunis, where he had the honor of refusing knighthood and reward at the hands of the great emperor Charles VCharles V, Holy Roman Emperor
Charles V was ruler of the Holy Roman Empire from 1519 and, as Charles I, of the Spanish Empire from 1516 until his voluntary retirement and abdication in favor of his younger brother Ferdinand I and his son Philip II in 1556.As...
. Returning to Lisbon, he received from the king the small commandership of São Paulo de Salvaterra in 1538.
Soon after this he left for India in company with his uncle Garcia de Noronha, and on his arrival at Goa
Goa
Goa , a former Portuguese colony, is India's smallest state by area and the fourth smallest by population. Located in South West India in the region known as the Konkan, it is bounded by the state of Maharashtra to the north, and by Karnataka to the east and south, while the Arabian Sea forms its...
went off for the relief of Diu
Second Siege of Diu
The Second Siege of Diu was a siege of the Portuguese Indian city of Diu by the Gujarat Sultanate in 1546. It ended with a major Portuguese victory.- Background :...
. In 1540 he served on an expedition to Suez
Suez
Suez is a seaport city in north-eastern Egypt, located on the north coast of the Gulf of Suez , near the southern terminus of the Suez Canal, having the same boundaries as Suez governorate. It has three harbors, Adabya, Ain Sokhna and Port Tawfiq, and extensive port facilities...
under Estêvão da Gama (the son of Vasco da Gama
Vasco da Gama
Vasco da Gama, 1st Count of Vidigueira was a Portuguese explorer, one of the most successful in the Age of Discovery and the commander of the first ships to sail directly from Europe to India...
and them viceroy of Portuguese India), by whom his son, Álvaro de Castro, a child of thirteen, was knighted, out of compliment to him. Died D. Garcia, succeeded him in the government D. Estevao da Gama, and D. João de Castro was found with him in the expedition to the Red Sea. D. Estevão da Gama went with 12 large galleons and carracks, and 60 galleys, on December 31, 1540, being D. João de Castro captain of a galleon. This expedition to Suez was truly remarkable, and João de Castro made a detailed roadmap of it, with maps, calculations, pictures and detailed notes from the coasts of the Arabian Peninsula
Arabian Peninsula
The Arabian Peninsula is a land mass situated north-east of Africa. Also known as Arabia or the Arabian subcontinent, it is the world's largest peninsula and covers 3,237,500 km2...
as of those of the countries of today Somalia
Somalia
Somalia , officially the Somali Republic and formerly known as the Somali Democratic Republic under Socialist rule, is a country located in the Horn of Africa. Since the outbreak of the Somali Civil War in 1991 there has been no central government control over most of the country's territory...
, Eritrea
Eritrea
Eritrea , officially the State of Eritrea, is a country in the Horn of Africa. Eritrea derives it's name from the Greek word Erethria, meaning 'red land'. The capital is Asmara. It is bordered by Sudan in the west, Ethiopia in the south, and Djibouti in the southeast...
, Ethiopia
Ethiopia
Ethiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...
, Sudan
Sudan
Sudan , officially the Republic of the Sudan , is a country in North Africa, sometimes considered part of the Middle East politically. It is bordered by Egypt to the north, the Red Sea to the northeast, Eritrea and Ethiopia to the east, South Sudan to the south, the Central African Republic to the...
and Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
, as far to Suez and to several ports in the shores of the Sinai Peninsula
Sinai Peninsula
The Sinai Peninsula or Sinai is a triangular peninsula in Egypt about in area. It is situated between the Mediterranean Sea to the north, and the Red Sea to the south, and is the only part of Egyptian territory located in Asia as opposed to Africa, effectively serving as a land bridge between two...
, all included in the Roteiro do Mar Roxo, which offered to the Prince Louis. Eight months later he returned to Goa on August 21, having acquired by the experiences made during the expedition, the name of the philosopher. "I pay great attention to eclipses of the moon," he writes, as also to longitudes and latitudes, fishes, seaweeds, currents, winds,the colour of the Red Sea, and every detail that might concern the art of navigation, to the delight of his friends Pedro Nunes and Prince Louis, who had furnished him with special instruments and other assistance for his voyage.
D. João de Castro called for the need of the coordination between the observation and reason, in the case of the navigation: "This science of navigation is poorly distributed among the men, or because they act like idiots, which for a long time and continuous exercise they reach many particulars, though with all their works are never to gain authority in their office, or those who have no experience, but with much learning and great practice in the science of mathematics, reached the shadow of this art but not the true science."
It is in overcoming this divorce that rooted the ways of science, which reaches an understanding with no epilogue, an open knowledge, in constant motion approach, not compatible with the spirit of the system. João de Castro tell us that the knowledge of science is "come to the truth", that science is "closer to the truth and not the absolute truth": "We need to consider how much we owe for teaching us how not to ignore the fact that we can be closer to the truth, as are human things that men can learn (...). Not only to be expected by virtue of reaching the truth, but also get close to her."
Later life
Returning to Portugal, João de Castro was named commander of a fleet, in 1543, to clear the Atlantic EuropeAtlantic Europe
Atlantic Europe is a geographical and anthropological term for the western portion of Europe which borders the Atlantic Ocean. The term may refer to the idea of Atlantic Europe as a cultural unit and/or as an biogeographical region....
an seas of pirates; and in 1545 he was sent, with six sail, to India, to assist Martim Afonso de Sousa
Martim Afonso de Sousa
Martim Afonso de Sousa was a Portuguese fidalgo and explorer.Born in Vila Viçosa, he was commander of the first official Portuguese expedition into mainland Brazil...
, who had been dismissed of the viceroyalty. Seconded by his sons (one of whom, Fernão, was killed before Diu) and by João Mascarenhas, João de Castro achieved such popularity by the overthrow of Mahmud, king of Gujarat, by the relief of Diu, and by the defeat of the great army of the Adil Khan
Adil Shahi
The Adil Shahi or Adilshahi dynasty ruled the Sultanate of Bijapur in the Western area of the Deccan region of Southern India from 1490 to 1686. Bijapur had been a province of the Bahmani Sultanate , before its political decline in the last quarter of the 15th century and eventual break-up in 1518...
, that he could contract a very large loan with the Goa merchants. These deeds were followed by the capture of Broach
Bharuch
Bharuch , also known as Broach, is the oldest city in Gujarat, situated at the mouth of the holy river Narmada. Bharuch is the administrative headquarters of Bharuch District and a municipality of more than 1,50,000 inhabitants. As Bharuch is a major seaport city, a number of trade activities have...
, by the complete subjugation of Malacca
Malacca
Malacca , dubbed The Historic State or Negeri Bersejarah among locals) is the third smallest Malaysian state, after Perlis and Penang. It is located in the southern region of the Malay Peninsula, on the Straits of Malacca. It borders Negeri Sembilan to the north and the state of Johor to the south...
, and by the passage of António Moniz into Ceylon; and, in 1547, by the appointement as viceroy by king John III of Portugal
John III of Portugal
John III , nicknamed o Piedoso , was the fifteenth King of Portugal and the Algarves. He was the son of King Manuel I and Maria of Aragon, the third daughter of King Ferdinand II of Aragon and Queen Isabella I of Castile...
.
After the victory of his Armada in the refief of Diu, he besought the King not to prolong his term of office beyond the ordinary three years, and to allow him to return to the Serra de Sintra
Sintra
Sintra is a town within the municipality of Sintra in the Grande Lisboa subregion of Portugal. Owing to its 19th century Romantic architecture and landscapes, becoming a major tourist centre, visited by many day-trippers who travel from the urbanized suburbs and capital of Lisbon.In addition to...
, and in his will he says: "I have near Cintra a quinta, called the Quinta of the King's Fountain, which I made, and to which I am greatly devoted because I made it and because it is in a country where my father and ancestors were born". After his victory over the overwhelming odds of Mahmud and of the Adil Khan, D. João de Castro set about rebuilding Diu, and to obtain money sent an appeal to the citizens of Goa with some hairs of his beard in pawn since it was impossible to send the bones of his son, as he had first intended, his death being but recent. The citizens of Goa responded nobly to the appeal, and when the Governor returned to Goa in the spring of 1547. they received him with great rejoicing. His triumph ceremony has been often described in the chronicles and tapestry.
He addressed the chief officials and magistrates of Goa: "I am not asham'd, gentlemen, to tell you that the Vice Roy of India wants in this sickness those conveniences the meanest souldier finds in the Hospitals. I came to Serve not to traffick in the East, I would to your selves have pawn'd the bones of my Son and did pawn the hairs of my beard to assure you I had no other plate or hangings in the house to buy me a hen, for in the fleets I set forth the souldiers fed upon the Governour's salary before the King's pay, and 'tis no wonder for the father of so many children to be poor. I request of you during the time of this sickness to order me out of the king's revenue a proportionable maintenance and to appoint a person of your own who may provide
me a moderate allowance."
He did not live long to fill this charge, dying in the arms of his friend, Saint Francis Xavier
Francis Xavier
Francis Xavier, born Francisco de Jasso y Azpilicueta was a pioneering Roman Catholic missionary born in the Kingdom of Navarre and co-founder of the Society of Jesus. He was a student of Saint Ignatius of Loyola and one of the first seven Jesuits, dedicated at Montmartre in 1534...
, on 6 June 1548. He was buried at Goa, but his remains were afterwards exhumed and conveyed to Portugal, to be reinterred under a splendid monument in the convent of Benfica
Benfica (Lisbon)
Benfica is a Portuguese parish, located in the municipality of Lisbon. It has a population of 38,523 inhabitants and a total area of 7.94 km².The biggest park of Lisbon, Monsanto Forest Park, is located in Benfica.-20th century:...
. The chronicler Diogo do Couto
Diogo do Couto
Diogo de Couto was a portuguese historian.-Biography:He was born in Lisbon in 1542 and studied Latin and Rhetoric at Saint Antão College and philosophy at the convent at Benfica...
ends his portrait of the Viceroy thus: "And for his great charity, temperance, disinterestedness, exceeding love of God, and other qualities of a good Christian, it may be affirmed that he will be receiving in glory the prize and guerdon of all his trouble and toil." And for the author Aubrey Fitz Gerald Bell: "by his energy, vigour of thought and action, by his splendid character, humane and resolute, he closed the most briliant half-century of Portugal's history with a key of gold."
The Terrestrial Magnetism in the Roteiro from Lisbon to Goa: the experiences of João de Castro
The ancient Greeks had discovered that a dark stone metal could attract or repel objects of iron. Was the origin of the study of magnetismMagnetism
Magnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...
. At the time of the great sailing, the navigators could not find a ship at sea by the two coordinates, latitude and longitude, the determination of this required a clock on board to indicate the exact time at the meridian of reference, and the astronomical determination of longitude gave unacceptable errors. During the trip to India, D. João de Castro has carried out a series of experiments that succeeded in detecting the phenomena, in particular related to magnetism and the magnetic needle on board. It should be assumed that such knowledge comes from Pedro Nunes
Pedro Nunes
Pedro Nunes , was a Portuguese mathematician, cosmographer, and professor, from a New Christian family. Nunes, considered to be one of the greatest mathematicians of his time , is best known for his contributions in the technical field of navigation, which was crucial to the Portuguese period of...
, of course the direct inspiration of all the observations he has done in his travels. When on August 5, 1538, D. João de Castro decided to determine the latitude of Mozambique, found the cause that dictated the astonishing uneasiness of needles; noted the deviation of the needle, discovering it 128 years before Guillaume Dennis (1666) of Nieppe, which is recorded in history of sailing as if he were the first to know about this phenomenon. His observation near Baçaim, on December 22, 1538, of a magnetic phenomenon, for which there were variations of the needle because of the proximity of certain rocks, confirmed four centuries later, called local attraction. D. João de Castro refuted the theory that the variation of magnetic declination is not formed by geographic meridians.
To the words of Pedro Nunes expressed in De Crepusculis, which refers the things he had discovered, meditating and investigating, that nowhere he had read before and wouldn't have credit if they were not shown, we can associate the words of D. João de Castro in its Roadmap (Roteiro) of Lisbon to Goa: "in this written script many things that will seem strange and impossible, which I wrote fearfully, not because of them were not very certificate, but for fear that I had to out of the common opinion. "
The comments made by João de Castro are the most important record of values of magnetic declination in the Atlantic and Indian
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
oceans, in the sixteenth century, and useful for the study of terrestrial magnetism. He made 43 determination of magnetic declination through rigorous measurements of geomagnetic declination over the entire circum-Africa route. The instrument used by him was the Bussola de Variacão, also developed by Felipe Guillen a decade earlier in Seville. João de Castro undertook many observations and can in a way be considered as one of the discoverers of crustal magnetism. He discovered spatial variations of Declination in that Bay of Bombay (near Baçaim), which he attributed to the disturbing effects of underwater rock masses (this is near where the large basaltic and rather strongly magnetized Deccan traps outcrop).
In the 1890s, G. Hellman, quoted by Chapman and Bartels (1940), considered Castro to be the most important representative of scientific maritime investigations of the time, and the method he tested was universally introduced on ships and was used until the end of the sixteenth century. It was one of the personalities of this century of European experimental science, linking the importance of this study with the sailing. His name was linked to science for his works which showed a trend for modern scientific spirit.