Having resigned his clerkship, he pursued a bush life, and in 1872 made his first effort in the field of exploration.  His party was a small one, the funds being found by contributions from S. Carmichael, one of the party, Baron von Mueller, Giles himself, and one of his relatives.  The members of the expedition were Giles, Carmichael, and Robinson; 15 horses and a little dog were included in the equipment.  They started from Chambers Pillar, and it was on this journey that Lake Amadeus and Mount Olga were discovered, the two most enduring physical features whose discovery we owe to Giles.  The lake is a long narrow salt-pan of considerable size, but without any important affluents; Mount Olga is a singular mountain situated about 50 miles from the lake.  On this trip Giles went over much untrodden country, but the smallness of the party at last convinced him that it was beyond their frugal means to force their way through the desert country to the settlements of West Australia.  Giles was fortunate on this his first trip in having two able and willing bushmen for his companions; otherwise he would not have progressed as far as he did and returned in safety.  But most untiring endeavours will not compensate for the lack of numbers, and Giles was forced to return beaten from his first attempt.

His second expedition took place about the same time as that undertaken by Gosse.  In consequence of a stirring appeal by Baron von Mueller, he had now the advantage of both substantial private help and a small sum from the South Australian Government.  The party numbered four:  W.H.  Tietkins, who afterwards made an honourable name as an independent explorer; the unfortunate Alfred Gibson; and a lad named Andrews, in addition to the leader.

Giles left the settled district at the Alberga, and made several determined efforts to push through the sandy spinifex desert that had baffled so many.  It was during one of these forlorn hopes that Gibson died.

Anxious to reach a range which he had sighted in the distance, and where he hoped to find a change of country, Giles made up his mind to make a determined effort to reach it, carrying a supply of water with him on pack-horses.  As usual, Tietkins was to accompany him, but as Gibson complained of having been always previously left in camp, he was allowed to go instead.  The two kept doggedly on, the horses, as they gave in, being left to find their way back to the main camp.  At last, when several days out, they had but two horses left.  Giles sent Gibson back on one, with instructions to push on for the camp, taking what little water he wanted out of a keg they had buried on their outward way, leaving the remainder for his use.  He himself intended to make a final effort to reach the range.

Giles’s horse soon gave in after they parted, and he had to start to return on foot.  On his weary way back he saw that one of the abandoned horses had turned off from the trail, and that Gibson’s tracks turned off too, seemingly following it.  When he reached the keg, he found that the contents were untouched.  Fearing greatly that the unfortunate man’s fate was sealed, Giles dragged himself on to the camp.  A search was at once instituted, but it was fruitless.  Neither man nor horse was ever seen again; and the scene of his fate is known as Gibson’s Desert.