From Atlas Obscura by Eric Grundhauser
Did a secret search for Marco Polo’s islands of gold lead Portuguese explorers to be the first Europeans to discover Australia?
According to some theories, the Dieppe maps, a series of artful 16th century maps say yes.
Operating in the mid-1500s, the Dieppe mapmakers created elaborate, hand-made world maps for wealthy patrons and royals.
The French artists who created the maps were just that, leaving the actual exploration to others and simply translating more utilitarian nautical charts into things of beauty.
The surviving maps are beautifully rendered, although their exact cartographic sources seem to have been lost to time.
This becomes most problematic in the case of "Java la Grande", a giant landmass unique to the maps that was drawn between Antarctica and what we would today consider to be Indonesia.
According to some modern researchers, this mystery island is actually the first record of Europeans seeing Australia.
The names and script on the charts are written out in a mix of French and Portuguese, giving rise to the theory, which was popularized in Kenneth McIntyre's 1977 book, The Secret Discovery of Australia, that the mapmakers of Dieppe were getting their view of the world, at least in part, from Portuguese expeditions.
In particular, one of the maps that came out of Dieppe, (and is survived by a faithful recreation) depicts the east coast of the fabled Java la Grande with place names almost exclusively in Portuguese.
Given the vagaries of the Dieppe map sources, this has led to the theory that it was the Portuguese who were the first Europeans to spy the Australian coast.
Wealthy Portuguese explorer Cristóvão de Mendonça is recorded as having been tasked by King Manuel with sailing out in search of Polo’s treasure islands, but actual record of this voyage has been lost, if there ever was one.
Manuel was notoriously secretive about the findings of his exploration teams.
According to popular history, Australia was first visited by Europeans when Dutch explorer Willem Janszoon “discovered” the continent in the early 17th century, and later fully explored by Captain Cook.
On the left, first Portuguese chart designed in Dieppe by Jean Rotz in 1542.
On the right, Australia seen by Dutch in 1628...
While no direct evidence of Portuguese discovery exists, there have been other findings that seem to support the theory of their early Australian discovery.
Various ruins, cannons, and other archeological artifacts have been found on the Australian continent that believers say point to Portuguese discovery, but the Dieppe maps remains the prime source of speculation.
- Wikipedia : Theory of the Portuguese discovery of Australia
- The Stradbroke Island Galleon and Java La Grande
- GeoGarage blog :Capt. James Cook raised an ocean of knowledge / Controversial 400-year-old Australian map exhibited / The man who invented the Admiralty chart and nearly discovered Australia and Antarctica