One of the greatest disappointments in the last 300 years of Western history: the discovery that the entire Australian interior was actually a desert
"The Desired Blessing"
This Hyperaustralian vision is based on an 1827 map by Thomas Maslen, an officer of the East India Company. After Oxley's 1817-18 expeditions discovered west-flowing rivers beyond the Dividing Range, the public imagination was captured by the idea of an Inland Sea. Maslen extrapolated these rivers as the headwaters of a vast "Great River" flowing across Australia's interior, and imagining the poorly-explored inlets at Derby to be a large delta, emptying the river into the Indian Ocean - he dubbed this "the desired blessing" of Australia. The necessary hydrocycle for such a drainage was supported by similarly imagined highlands along the Great Australian Bight, and a drainage basin that covered almost the entirety of the continent. Had it existed, it would have supported enormous fertile tropical regions, as well as inland shipping for trade and communications.
Sadly for this vision, reality was otherwise. As Maslen's book was being published in 1830, Charles Sturt's second expedition was returning with proof that Oxley's inland rivers in fact drained south, into the Murray, Lake Alexandrina and the Southern Ocean. Belief in the inland sea persisted until well into the second half of the century, until multiple north-south crossings of the continent had proved definitively that it did not exist, apart from the permanent salt pan of Lake Eyre. Maslen's supposed "Dead Level" of the interior was confined to parts of South Australia, with the northwest of the continent divided by a vast inland plateau. Therefore, rather than reliable orographic rainfall, the interior was dependent on southward extension of the Australian Monsoon - an unreliable pattern, and further hampered by a rain shadow effect from the northwestern highlands.
Yet there is now evidence that that pattern is beginning to shift. Long-term rainfall trends for the Lake Eyre basin show a sustained increase - some 100mm higher (50%!) since 1980. Partial fillings of Lake Eyre, once rare, now occur every few years. If the trend continues, it's conceivable that within a few decades, the lake may be permanently full, perhaps even begin to grow...
Now that would be a blessing.