William Clifford kept a Medical Journal from 20 December 1829 to 4 May 1830 on the voyage of the Forth...........The convicts embarked on the Forth were without exception men whose habits from the earliest period indolent in the extreme and disposed to depression and illness...To keep up that system and regularity of discipline and cleanliness so conducive to health and personal comfort on ship during a long voyage made with vicissitudes of climate required every energy during the early stage and as we advanced to the Tropics when fever appeared. 
The Sydney Gazette reported the following testimonial to Dr. Clifford by the prisoners: Dr. Clifford, the Surgeon Superintendent of the Norfolk, has now performed three voyages, to this colony in that arduous and responsible capacity. For kind attention to the prisoners under his charge, united with the maintenance of the strictest discipline and good order, Dr. Clifford is not surpassed by any of his professional brethren in this branch of the public service. Of this a more satisfactory proof could not be afforded than the fact, that he has been presented by the convicts, both on this and former voyages, with written testimonials of their gratitude for his humane treatment. The Transport Board has also been made sensible of his merits, for which it has made suitable acknowledgements. (5)
William Clifford kept a Medical Journal from 10 August 1837 to 2 January 1838. He began treating women while the vessel still lay in Kingston Harbour... The first patient Eliza Burke sought the surgeon's assistance on 8th August 1837 and was found to be suffering from enteritis. On the same day there was a violent quarrel amongst the women in the Mess and Bridget Ryan age 23 received a serious injury when she was hit over the eye with the edge of a pot. Although the bone was exposed and there was a large haemorrhage, syncope and vomiting the surgeon treated her successfully and she was discharged from the sick list on 18th August.
He had much to contend with during this voyage because of the very crowded state of the ship which was nearly constantly wet owing to being low in the water...... The Irish convicts desponding, indolent and disposed to dirt, required every exertion to keep their minds in a fit state.. There was an outbreak of scurvy which was treated with vinegar and sugar and as the surgeon had found in previous voyages, early doses of nitrous were effective. After the Cape the weather turned cold and there were several cases of catarrh. An infant George Kelly, age 17 months was treated for dysentery on 11th October 1837 and died on 29th October. One of the women who died was of a broken constitution after a life of prostitution and dissipation. Margaret (Peggy) Fallon from Galway died at sea on 2nd December 1837 
William Clifford was on the List of Surgeons of the Royal Navy who were fit for service in 1841
He died at his residence Cumberland, Parsonstown, Ireland on 1 March 1858 aged 73 years.  National Archives - William - William Clifford, Surgeon Royal Navy, who died: 2 March 1858. Notes on executor's application for money owed by the Royal Navy. Reference: ADM 45/39/606 Description: Number: 606