In 1817, Mr.Oxley directed his attention to the former river, and continued to follow its windings, until it appeared that its waters were lost in successive marshes and it ceased to be a river.

In the following year he turned towards the Macquarie, and traced it, in like manner, until he was checked by high reeds that covered an extensive plain before him, amidst which the channel of the river was lost.
From what he observed of the country, on both these occasions, he was led to infer that beyond the limits of his advance the interior had a uniform level, and was, for the most part, uninhabitable and under water.

Its features must have been strongly marked to have confirmed such an opinion in the mind of the late Surveyor-General.

It stands recorded on the pages of his journal, that he travelled over a country of many miles in extent, after clearing the mountains, which so far from presenting any rise of ground to the eye, bore unequivocal marks of frequent and extensive inundation.

He traced two rivers of considerable size, and found that, at a great distance from each other, they apparently terminated in marshes, and that the country beyond them was low and unbroken.