William Petrie was appointed Surgeon to the Alfred in 1812.
He was entered in the Navy List of Medical Officers in 1814.
William Petrie was employed as Surgeon Superintendent on two convict ship voyages to Australia:
1) Woodford to VDL in 1828
2). Sir Charles Forbes to VDL in 1830
Woodford departed Portsmouth 2 May 1828 and arrived in Van Diemen's Land 25 August 1828. William Petrie kept a Medical Journal from 29 March to 31 August 1828.
Sir Charles Forbes departed Plymouth 5 April 1830 and arrived in Van Diemen's Land 27 July 1830. He kept a Medical Journal from 27 February to 1st August 1830.
November 1828 - At Kingston, Jamaica, of the endemical fever, in the 14th year of his age, Thomas James Huyghue, only surviving son of William Petrie, M.D. and surgeon, Royal Navy, Leith. 
At Milverton, Warwickshire, Charles Campbell Sutherland esq., eldest son of George Sutherland, Esq. of Campbelton, Argyllshire to Agnes Anne Waugh, second daughter of the late William Petrie esq. M.D. Surgeon R.N.