Naval surgeon and settler Charles Throsby was convinced in 1821 that the Murrumbidgee River ran north, not south

He saw that this substantial river, which had been on his mind since he had heard about it from the Aborigines, flowed in a northerly direction away from the coast. He had desperately wanted this river to flow to the south - towards the sea and to the bays on the east coast of New South Wales.

He reasoned that if it did indeed flow south it would provide a navigable water highway, carrying produce from the potentially rich grazing plains he had just crossed, to the sea and thence to the growing settlements of the colony. He may also have reasoned that if he was the first colonist to discover this route he would gain the high favour of Governor Lachlan Macquarie and gather the financial benefits, which he desperately needed. It was not to be.

Determined to find the (Murrumbidgee) river, he despatched his 22-year-old nephew, Charles Throsby Smith, recently arrived in the colony, along with Joseph Wild and James Vaughn, to press on further south.

In the heat of December, the small group started out from Lake George, following the route of Charles Throsby and crossing the Yass River. They headed in a southerly direction, approximately along what is now the route of the Federal Highway, to encounter the open grassy plain of the Molonglo River. They erected a rough hut and Throsby Smith recorded large quantities of limestone around the margins of the plain. The name ''Limestone Plains'' was to be given to this area. Their campsite on the bank of the Molonglo was probably in what is now Commonwealth Park or the West Basin of Lake Burley Griffin.

Young Throsby Smith, along with Vaughn, then climbed the slopes of Black Mountain. From the top they had an extensive view all around and saw that the river they had just found continued in a south-west direction then turned to the north-west. From their vantage point they would also have seen further plains to the south (Woden and Tuggeranong) and looming in the distance, the forbidding heights of the Brindabellas. They returned to camp and stayed the night, the first Europeans to dwell, albeit briefly, on the land that is now the national capital.

It seems that Throsby Smith was convinced that the river his uncle had been seeking was a fantasy and decided to go no further. He and his group turned back towards Lake George, giving up the quest without following further the course of the river.

Uncle Charles was mightily displeased at his nephew's unwillingness to press on. If Throsby Smith and his group had proceeded on from the Limestone Plains and followed the downstream course of the Molonglo River they would have reached the Murrumbidgee in a day or two - the first Europeans to do so - and seen that the river flowed to the north and inland. But he had returned to his uncle without this knowledge.

Charles Throsby still held to the vision of this large river flowing south towards the sea and providing the transport route for the new agricultural lands. He knew well the profits that could be made by those who first utilised the routes. His young nephew may have lacked the determination to go further into unknown lands in search of the river but Uncle Charles was made of sterner stuff.

The next year Throsby was again at Lake George with the reliable Joseph Wild at his side. He followed the shoreline around the base of the Cullarin cliffs to where Bungendore now stands, and then headed towards where he suspected the fabled river would be flowing. They were now crossing country familiar to Wild. In May 1821 Throsby and Wild reached the Limestone Plains. Wild would surely have pointed out to Throsby his nephew's former campsite by the Molonglo and then taken him to the mountain his companions had climbed just a few months before and looked towards the distant mountains in the west. By now Throsby's health was failing, but his vision of a highway to the sea was still as strong as ever, and he would have known that he was close to reaching his destination. They pressed on, following a route through the low hills, finally reaching his fabled river.

We can never know the full extent of Throsby's disappointment at finally reaching his river and seeing it flowing strongly to the north-west away from the sea. He would have had to finally reconcile to himself that his vision of a navigable route connecting the inland to the sea had come to nothing - it was, as his nephew had hinted, all in his imagination.

Throsby returned to his home near Moss Vale with a heavy heart. Governor Macquarie granted him 700 acres (283 ha) of land to adjoin his property of Throsby Park, or any part of the new country he desired. In 1825 Throsby was appointed to the Legislative Council of the colony, but continued ill health, financial difficulties, drought and the falling price of wool drove him to take his own life on April 2, 1828. He was just 51.

Charles Throsby, Joseph Wild and John Vaughn were the first Europeans to reach the Murrumbidgee River, but their names are seldom mentioned in the history of Australian exploration. A new suburb in north Canberra is named after Throsby and urban streets in the ACT and Queanbeyan bear their names in recognition of their contribution to the exploration and prosperity of the colony.