There is a James NATION who married a Lavinia SWEETINGHAM on the Isle of Wight in Hampshire, England in 1879, who is in Hobart by the mid 1880s having children. In 1881 census they were still on the Isle of Wight.
Landrock Cottage, Niton, Isle of Wight
James NATION, head mar 32, Waiter, born Hants, Basingstoke
Lavinia NATION, wife mar 30, born Hants, Southampton
Hilda NATION, dau 1, born Isle of Wight, Landown
James NATION, son 2m, born Isle of Wight, Niton
+ a servant
RG11/1186/7/8
There was a child born in Hobart in 1881, so they must have come out during that year. Lavinia NATION died aged 39 in Hobart in 1890.
Ian C