[5] In March 1801 Governor Phillip Gidley King sent him with Lieutenant James Grant in HMS Lady Nelson to further explore, survey and map Bass Strait.
[6] Barrallier's resulting maps of Jervis Bay, Western Port[7] and some of Bass Strait[8] were recognised by Governor King, who made him the Colony's engineer and artillery officer.
[3] After a preliminary reconnaissance in September-October, he mounted a major expedition in November, employing a bullock cart to take provisions to a depot that he set up northwest of today's town of Picton.
The first terminated prematurely in the Burragorang Valley when his principal guide, the Dharawal man Gogy, found himself unwelcome amongst the Gundungurra people whose country they had entered.
On the second incursion, with two different Aboriginal assistants, Badbury (Boodbury) and Le Tonsure, he penetrated further west but eventually turned around at Johnston Falls in Wheengee Whungee Creek, six kilometres southwest of Kanangra Walls.
[12] These documents provide an important record of his encounters with the First Nations people he met or who accompanied him, and reveal that Barrallier had an uncommon understanding of their ownership of country.
He was then appointed aide-de-camp to General Sir George Beckwith, commander of the English forces in the West Indies, and in 1810 earned another silver medal for his role in the capture of Guadeloupe.
[20][21] This has proved to be significant in the campaign for restorative justice for the people of Barbados, a former slave colony, for it lists the names of all the English owners of the plantations of the time.