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. From a slight rise he looked southwards:-- "The horizon was unbroken; all appeared one slightly undulating plain, with just sufficient triodia and bushes growing on it to hide the red sand when viewed at a distance." Gregory reviewed the problem from a logical standpoint. He decided to follow the northern limit of the desert to the westward, until he should find a southern-flowing watercourse which would afford him the opportunity to make a dash beyond its confines. On the 15th of February he came to a small flat which gradually developed into a channel and ultimately became a creek, running first west, and then south-west. This gave him his desired opening, and he pursued the course of the creek through good open country, finding the water plentiful, though shallow. On February 20th, however, the channel of the creek was lost in an immense grassy plain. The country to the south being sandy and unpromising, Gregory kept westwards, and succeeded in again picking up the channel, now finding the water in it to be slightly brackish. That day he crossed the boundary of Western Australia. The creek now gave promise of continuity, the water-holes taking on a more permanent appearance. It was now pursuing a general south-west course, and Gregory, though still rightly anticipating that it would eventually be lost in the dry interior, determined to follow it as far south as should be compatible with safety. He named the creek Sturt's Creek, after the gallant explorer of that name, who was naturally then often in his mind. The creek maintained its southern course, until, on the 8th of March, it ran out into a mud plain and a salt lake.