Finnis was born in Dover, a son of Gilbert Finnis and his wife Elizabeth Finnis. He qualified as a mariner, and after a few years as a working captain, in 1831 with Joseph Montefiore purchased the barqueElizabeth, in which he spent five successful years whaling in the southern seas. In September 1838, he, with Captain Charles Sturt, Giles Strangways and George McLeod brought 400 cattle overland from the Hume River. In 1839 Finnis, with Hampden Dutton and Duncan McFarlane, purchased 4000 acres, to the chagrin of John Barton Hack, who was squatting there and had no intimation of the Special Survey. The land was used to fatten their cattle for sale, and settle 39 German families. brought to Australia by George Fife Angas on the Zebra and Catharina. The following year he drove 10,000 sheep from New South Wales to Adelaide with Nelson and John Tooth, then supervised several later musters. Early in 1841 he and Frederick Dutton had another 12,000 sheep brought overland, which they offered for sale in March 1841, and also quantities of brandy, cigars and tobacco which they had brought by sea. In 1843 he returned to the sea, chartering the Joseph Albino to bring goods from New Zealand and by the return journey export wheat and other commodities. He then purchased the ship and made other voyages, but the Joseph Albino was impounded in America with no redress. He died at his home in Franklin Street, Adelaide.
Family
In Sydney, on 23 March 1832, he married Ludovina Rosa Da Silva Cameron , the widow of Colonel Charles Cameron. Children of Rosa and Charles included:
Charlotte da Silva Cameron married Hampden Dutton on 2 July 1831.
Ewan Wallace Cameron married Sophia Nail in 1856
Julian Ludovina Cameron married Dr. George Bennett of Sydney on 28 November 1835. She took her own life by taking prussic acid. They had two sons and three daughters.
On 3 September 1856, at his home in Franklin Street, Adelaide, Finnis married Mary Ann Russell, a daughter of his sister. The Rev. James Pollitt was charged under canon law, on the information of G. S. Kingston, of officiating at a clandestine marriage within the Anglican Church's prohibited bounds of consanguity, and had his licence suspended for a year. They had two sons, one of whom, John Mercer Finnis survived to adulthood, and whose son, Harold Finnis, was a longtime secretary of the R.A.& H.S
