Bonnar emigrated to South Australia aboard
Warrior, arriving in South Australia (dep from London 17 November 1839, via Plymouth) on 17 April 1840. He married Lucy Anderson (1826–1904) on 2 September 1848 at St James Church, Blakiston, South Australia. She had arrived in the colony aboard
Anna Robertson with her parents and siblings on 20 September 1839. The Bonnars opened a school at
Mount Barker in 1846 His schoolroom was used for Sunday services by Rev.
James Pollitt in the absence of a Presbyterian church building in the town. :His brother, Henry Bonnar ( – ), third son of James Bonnar, surgeon, RN, had a school near Mount Barker Springs in 1855 He then had a school in
Shellharbour, New South Wales from 1859 followed by the school in nearby
Kiama. His wife Emily, née Ellis, died in March 1863. He married again on 3 September 1863 to Julianna Collie of
Wollongong. He returned to South Australia and in 1868 opened a school in
Strathalbyn, which flourished and had to be expanded several times, but Bonnar had difficulty managing the larger school and was in 1880 transferred to
Morphett Vale. His subsequent movements are yet to be found. Some later accounts of the history of Mount Barker appear to confuse or conflate these two Bonnars and their schools. In the early 1850s or perhaps earlier, Bonnar began practising as a solicitor in Mount Barker. When or how he was admitted to the bar is not known, but it is clear that he had a training in a lawyer's office. In 1865 he transferred his head office to Strathalbyn, and took as a partner
Joseph James Whitby to handle the Mount Barker office. A year later the partnership was dissolved, and Bonnar took into partnership William Steele, who died in August 1868. By this time other lawyers, T. Goddard and William Walker had opened offices in Mount Barker, and Bonnar allowed this side of his business to lapse. :On 11 June 1866,
Louis von Doussa was articled to Bonnar at Strathalbyn, and was admitted to the Bar in November 1871. He then resumed the old Mount Barker legal business and began practice there early in 1872. He since made a name for himself, which business was carried on by his grandson,
William von Doussa. He died at "Dunreath",
Manly, New South Wales and his remains were interred in the Manly Cemetery. ==Other interests==