After passing both Warburton's tracks and those of Giles, Gosse reached the extreme western point of the Macdonnell Ranges, where another stationary camp was pitched.

The leader made a long excursion to the south-west, and at 84 miles, after passing over sand-ridges and spinifex country, caught sight of a remarkable hill, that on a nearer approach proved to be of singular limestone formation.
"When I got clear of the sandhills, and was only two miles distant, and the hill, for the first time coming fairly in view, what was my astonishment to find it was one immense rock rising abruptly from the plain; the holes I had noticed were caused by the water in some places causing immense caves." This hill, which Gosse made an ineffectual attempt to ascend, he called Ayer's Rock.

He returned to his depot camp, crossing an arm of Lake Amadeus as he did so, and moved the main body on to Ayer's Rock.

Rain having set in heavily for some days, he pushed some distance into Western Australia, but soon reached the limit of the rainfall.

After many attempts to penetrate the sand-hill region which confronted him, the heat and aridity compelled him to turn back.
His homeward course was by way of the Musgrave Ranges, where he found a greater extent of pastoral country than had been thought to exist there.
He discovered and christened the Marryat, and followed down the Alberga to within sixty miles of the Overland Line, when he turned north-eastward to the Charlotte Waters station.
Although Gosse's exploration did not add any important new features, he filled in many details in the central map, and was able correctly to lay down the position of some of the discoveries of Ernest Giles.
William Christie Gosse was the son of Dr.Gosse, and was born in 1842 at Hoddesdon in Hertfordshire.