Date of Seniority Royal Navy 22 February 1831
James Barr was employed as Surgeon Superintendent on two convict ship voyages to Australia: Waverley to NSW in 1839 and Mary Anne to VDL in 1841
VOYAGE OF THE WAVERLEY
The Waverley departed Dublin on 22 February 1839 and arrived in Port Jackson on 17th June 1839. James Barr kept a Medical Journal from 14 January to 23 June 1839.
Prisoners were mustered and inspected on Thursdays and Sundays during the voyage. James Barr ensured the prisons were kept clean and dry by swinging stoves. If the weather was fine, the men were obliged to be on deck unless they were in school or were unwell.
He thought a great improvement could be made in the construction of prison ships by replacing the upright elm stanchions in the three hatchways with iron bars which would provide better ventilation. 
VOYAGE OF THE MARY ANNE
On the voyage of the Mary Anne to Van Diemen's Land on 19 March 1841 he kept a Medical Journal from 16th October 1840 to 30th March 1841.
James Barr is listed in the Medical Register of 1865 -
Registered 28 May 1861, Surgeon Royal Navy, Silverton Hill, Hamilton, Lanarkshire.
Lic Royal College Surgeons, Edinburgh 1823;
M.D. University of Glasgow 1828. 
He is entered in the 1851 Census and gave his birth place as Lesmahagow, Lanarkshire and age 53. He resided in Dumfrieshire with his wife Janet age 45. He was not practising as a Surgeon and ran a farm employing 11 labourers and other staff.
He was on the list of Surgeons of the Royal Navy retired in 1864
James Barr died in January 1867 
 Journal of James Barr on the voyage of the Waverley. Ancestry.com. UK, Royal Navy Medical Journals, 1817-1857 Original data: The National Archives. Kew, Richmond, Surrey
 Medical Register
 The Lancet