An attempt had previously been made to ascend the river in the portable boat with which the expedition had been supplied, but it was not successful, as the boat could not navigate the rocky bars in safety.
Gregory left camp accompanied by his brother, Dr.von Mueller, and Wilson, taking seven horses and twenty days' rations, his object being to examine the country through which the exploring party would have to travel on their route to the interior.

On this preliminary trip, he penetrated as far as latitude 16 1/2 south, whence, finding the tributaries flowing from fine open plains and level forest country, all well-grassed, he returned to the main camp.
On the 4th of January, 1856, Gregory started with a much larger party on an energetic dash into the interior.

He had with him six men besides his brother, Dr.von Mueller and Baines the artist, and thirty-six horses.

He retraced his steps along his preliminary route, and on the 30th of January, thinking it wise judging from the rapid evaporation of the waterholes, to make his means of retreat secure, he formed a temporary camp, leaving there four men and all the horses but eleven to await his return, whilst he, his brother, Dr.Mueller, and a man named Dean, rode ahead to challenge the desert to the south.

On the 9th of February, having run the Victoria out, he crossed an almost level watershed, and found himself on the confines of the desert.