*Date of Seniority Royal Navy 22 January 1834
James Leathem Clarke joined the Navy on 01 November 1827 
He was on the list of Surgeons of the Royal Navy who were fit for service in 1841
James L. Clarke was employed as Surgeon Superintendent on four convict ships to Van Diemen's Land:
Navarino from London to Hobart 1841 with female prisoners. The Navarino departed the Downs 12 October 1840 and arrived in Hobart on 17 January 1841. Five deaths of convicts.
North Briton to Hobart in 1843. The North Briton departed Dublin on 20 December 1842 and arrived in Hobart on 4 April 1843 with 179 male convicts. One death on the voyage
Greenlaw to Hobart in 1844. The Greenlaw departed Dublin 5 March 1844 and arrived in Hobart on 2 July 1844 with 115 female convicts. Five deaths on the voyage
Joseph Somes to Hobart in 1846 . The Joseph Somes departed Woolwich on 22 December 1845 and arrived in Hobart 19 May 1846 with 243 male convicts. Ten deaths occurred on the voyage.
A son James Thomas Robert was born to James Leathem and Jane Lydia Clarke in 1842, Co. Middlesex and another George Pears Clarke was born at Brighton Terrace St. Matthew Brixton in 1845.
James Leathem Clarke died in September or October 1849  In his Will, he left his estate to his wife Jane Clarke.
. National Archives UK
 Quarterly Naval Obituary. The Morning Post (London, England), Tuesday, October 02, 1849; pg. ; Issue 23656. British Library Newspapers, Part II: 1800-1900.