Most Australians are aware of Dutch visits to the west coast of Australia in the 1600s, with a number of the Batavia (Jakarta)-bound vessels involved famously being wrecked there. The visit by William Dampier, an English buccaneer and explorer, in the same century is also generally known. Hardly anyone, though, has ever heard of the early Portuguese discovery of the east coast of Australia between 1521-24, some 250 years before Captain James Cook made his renowned 'discovery'.
How could this remarkable achievement of the Portuguese have slipped out of the history books? The reason is simple: it was arguably the most secret intelligence mission of its day. And it was not the first or last such mission to go publicly unrecorded.
In the latter part of the 1400s, the two Iberian powers – Spain and Portugal – were in hot contention over discoveries in the 'new world'. Pope Alexander VI was called upon by both parties to arbitrate and a demarcation line was settled on that ran north-south down the middle of the Atlantic, and on the other side of the globe, down through the middle of what was then the unknown continent of Australia (later adopted as the border between Western Australia and the other states). This created Spanish and Portuguese Hemispheres, with an amended line being formally written into the Treaty of Tordesillas between the two in 1494. In 1500, the Portuguese discovered and claimed Brazil, but the Spanish largely had free rein in Central and South America.
Things worked reasonably well and substantial amendments were made to the agreement in the Treaty of Saragossa in 1529, which was dishonourably breached by Spain in1562 when it seized the Philippines inside the Portuguese Hemisphere. Before all that, the Portuguese Viceroy of the key colony of Goa on the west coast of India was ordered to send out a secret mission into the Spanish Hemisphere to check whether a rumoured great south land did indeed exist.
He chose a naval captain of notable achievement and background, Cristovão de Mendonça, who left in 1521 with a fleet of three ships. He tracked across northern Australia, south of the chain of Indonesian islands – watchful for Magellan, who worked for the Spanish and was in the area at the time – and eventually passed through the treacherous waters of Torres Strait.
What happened next remained largely unknown for centuries. One key reason was that the Great Earthquake of 1755 that destroyed Lisbon also carried away with it the treasures of the Casa da India, the repository of all maritime records. The captains of all Portuguese vessels had long been obliged by law to lodge all of their charts and maritime journals in the Casa. Fortunately, French spies, who were among the most adept purloiners and copiers of secret Spanish and Portuguese charts of the day, managed to get their hands on Mendonça's map of the east coast of Australia not long after it was deposited in the Casa.
Why we know all this now is due to the outstanding endeavours of a great but little-known Australian, Kenneth Gordon McIntyre (1910-2004), who meticulously researched and pieced together the story. McIntyre, who was born in Geelong, graduated from and lectured in English at the University of Melbourne. He later went into the law and was for twenty-eight years Government Legal Adviser on the law relating to housing and building societies. He was also Mayor of the City of Box Hill. Throughout his life he had a profound interest in Portuguese literature and colonial history, stimulated by visits to Timor and to Portugal itself. He even taught himself to read Old Portuguese. After his retirement, he devoted himself entirely to the paradox of why the Portuguese had seemingly stopped at Timor, and not gone the further 285 miles to colonise Australia. The result of his labour was a remarkable book, "The Secret Discovery of Australia: Portuguese ventures 200 years before Captain Cook", published in 1977.
Mendonça's primary map of Australia, stolen by the French and known as the Dieppe May, bears little resemblance to the shape of the east coast that we're well acquainted with today. That's because of various navigational discrepancies that were commonplace in the early 1500s. The Portuguese customarily drew up a new 'portolan', or chart, whenever they sailed beyond a major coastal feature like a cape, which exacerbated the inconsistencies each time this was done. McIntyre studied calculus, navigation and cartography in order to 'decode' Mendonça's map and to equate certain features on it to well known points on our coast today. When run through a university computer program, which allowed for the early Portuguese navigational shortcomings, it produced a near-perfect map of the actual coastline.
Mendonça stayed safely away from the Great Barrier Reef, marking it as a Dangerous Coastline, though he did note a gap in the reef near the Endeavour River where Cook repaired his vessel. He clearly didn't enter Sydney Harbour, though just to the south, in a place later known as Botany Bay, he marks the spot as the Coste des Herbaiges.
It seems fairly certain that the British Admiralty had a copy of the Dieppe Map and provided it to Cook for what it was worth at the time. McIntyre believed that Cook had a copy, and if so, with Cook being such a highly skilled navigator and cartographer, it would not have taken him long to make the mathematical calculations required to render Mendonça's map useful.
A common feature or all Portuguese exploratory voyages was to establish a 'wintering post' or some sort of temporary settlement with a fort and storage facility, close to the next geographical segment of their mission. They did this at Bittangabee Bay, just below Eden on the south coast of NSW, beyond which they surmised they were about to enter very different seas. Early British settlers in that area in the 1820s came across the ruins of the blockhouse, with its carefully squared stone walls, and found no explanation for its existence. One fallen stone, probably the lintel stone across the main entrance, bore the numerals '15?4'. McIntyre took a rubbing of this and sent it to Portugal, where calligraphers confirmed the numerals were of Iberian form from that period. The blockhouse might have been used again on Mendonça's return voyage and the numerals carved then.
It is possible that Mendonça left the smallest of his three vessels there when tracking south-west, with orders to seek out the other two if they failed to return in a certain period of time.