Captain Sturt had seen what he felt confident was the junction of the river Darling with the Murray, but as there remained a portion of its lower course yet unexplored, room was left for a doubt whether this was the Darling after all. There were persons who entertained such doubts, and amongst them was Major Mitchell himself. “I began to entertain doubts on that subject. It seemed probable, from the divergent courses of the Macquarie and Lachlan, that these rivers might belong to separate basins, and that the dividing ridge might be ‘the very elevated range’ which Mr. Oxley had seen extending westward between them. It was obvious that this range, if continuous, must separate the basin of the river Darling from that of the river Murray.”

To determine this point, Mr. Dixon was sent as a preliminary measure in October, 1833, to trace the ranges between the rivers Lachlan and Macquarie, by proceeding westward from the Wellington Valley. Mr. Dixon descended that valley, and followed the Macquarie to where it crossed the northern extremity of Hervey's Range; thence he crossed to the river Bogan, and followed it down 67 miles to a little beyond the 32° of south latitude, and to the commencement of the ranges seen by Mr. Oxley afar off, stretching north-west of him, where he was compelled to turn back.

A more effective party was therefore fitted out in March, 1835, under Major Mitchell, to prosecute, if possible, the course of the Darling, from the point at which Sturt had abandoned it to where he saw it issuing into the Murray, in 1830.