In the close of 1817, the _Mermaid_, under the command of Captain, afterwards Admiral, King, was preparing to leave Port Jackson on a voyage of discovery on the western coast of Australia. Cunningham, to his intense satisfaction, received a letter from Sir Joseph Banks, directing him to join this expedition, in the interest of botanical science. Sailing through Bass' Strait the _Mermaid_ came to anchor in King George's Sound and other harbours, which proved to be well suited for the botanist's purpose, and yielded 300 species of new plants. With this spoil he came home fully satisfied. His next essay in this field was an excursion to Illawarra, which was always a favourite district with him. But this ramble was only an interlude. In 1819 he again joined Captain King in an expedition to the Macquarie Harbour, on the western coast of Van Diemen's Land (Tasmania), where also he collected many valuable specimens for the Kew Gardens. Soon after he was again associated with the same navigator on another voyage to the north-western coast. Still two more expeditions to the same coast were undertaken and successfully carried out within the next two years. The results in every case were highly successful, and the boundaries of science gained further extension from these enterprises. Having spent four years on these voyages with King, Cunningham became inoculated with the spirit of adventure, and thirsted for an exploit on his own account. The feat he proposed to himself was to open a practical route from Bathurst to the Liverpool Plains. This splendid district, as already narrated, had been discovered by Oxley three years previously; but he had entered it from the western side--so to speak, by the back door--on his journey from the marshes of the Macquarie. The discovery had, consequently, been useless, and the Liverpool Plains were as yet known only by name. Sir Thomas Brisbane, the Governor of the day, entered heartily into Cunningham's scheme, having clearly understood the importance of the object in view. Orders for an equipment were issued to the full extent of the explorer's requirements. All things being ready by the 31st of March, 1823, the party, consisting of the leader, with five men, and five pack-horses, carrying provisions for ten weeks, left Parramatta for Bathurst, which was reached on the 5th of April, and then the northward journey commenced. After many weary stages, during which the patience of the men and the strength of the horses were severely tried, they reached the Warrambungle Mountains, which form the southern boundary of the Liverpool Plains; but the difficulty in finding a passage through this barrier appeared to be insuperable. The first fortnight was spent to no purpose in attempting to discover an opening on the south-eastern side. Almost in despair, the party retraced their steps and fell back on a former encampment on the Goulburn River, the principal tributary of the Hunter. Provisions were now getting short,