John Griffith Williams was the second son of William Williams Esq., of Cefn-y-Cwmmwd, Anglesea Wales. 
He was appointed Surgeon, Royal Navy on 20 July 1838 
John Griffith Williams was employed as Surgeon Superintendent on two convict ship voyages to Australia:
1). Kinnear to VDL in 1848
2). Maria Somes to VDL in 1850.
The Maria Somes departed Portsmouth 6 May 1850 and arrived in Van Diemen's Land 9 August 1850.
Correspondence from John G Williams Esq re the convicts of the Maria Somes
17th May 1851
Taking into consideration the great number that were confined together in so small a space as the between decks of a convict ship and where so many opposite tempers were assembled I never saw a better behaved set of men I felt the greatest interest in the well being of my charge they were kind one to another and evinced much gratitude when any trifling act of kindness was shown to them. 
John Griffith Williams died at Greenwich on 31 August 1854. 
Notes and Links
National Archives. 25 September 1854. Will of John Griffith Williams, Surgeon R.N. of No 14 Cottage Grove Peckham , Surrey