Born on 27 June 1866 he was educated at King's College School and in 1884 won the Salters' university scholarship. He entered the medical department of King's College, London, in October 1884, won many prizes and the Sambrooke exhibition, and served as assistant demonstrator of physiology. In 1889 as senior scholar he won Sir Joseph Lister's clinical surgery prize. He served as clinical assistant to M M McHardy, who encouraged him to specialise as an ophthalmologist, but he also had the good fortune to act as house surgeon to Lister, whom he admired profoundly, and in later years publicly described the flawless character as well as the scientific achievements of his great master. After taking the Fellowship in 1892 he became surgical registrar at the Royal Eye Hospital, and in 1894 was appointed Sambrooke surgical registrar at King's College Hospital. With these two hospitals he maintained his connection throughout his career: he was elected assistant surgeon to the Eye Hospital in 1896 and to the ophthalmic department at King's in 1899, becoming on retirement in 1931 consulting surgeon to each hospital. He was also ophthalmic surgeon to the Seamen's Hospital, Greenwich. At the Royal Eye Hospital he was Chairman of Council 1931-48. During the South African war he served as ophthalmic surgeon with the Imperial Yeomanry Hospital, winning the medal and clasp. He published "Notes on ophthalmic conditions resulting from modern gunshot wounds" in the *British Medical Journal* 1901, 2, 1262. During the first world war (1914-18) he was an honorary consultant to military hospitals in London, with charge of the ophthalmic department of the 4th General Hospital. Cargill took an active part in his specialty, and was in much demand as a chairman. He was for many years on the Councils of the Ophthalmological Society of the United Kingdom and the Oxford Ophthalmic Congress; he also examined for the Oxford University diploma. In 1930 he visited Canada to attend the British Medical Association meeting at Winnipeg, the opening of the Banting Institute at Toronto, and the Pacific Coast Oto-Ophthalmologic Society's Congress at Victoria. After retiring he acted as treasurer of the Board of Registration of Medical Auxiliaries, was honorary consultant to the War Seal Foundation, an active governor of King's College School, Wimbledon, a member of the committee of management of the Chelsea Physic Garden, and Master of the Society of Apothecaries 1939-40. He was elected a Fellow of King's College, London in 1939. Cargill married in 1897 Emma, only daughter of William Sherwood; Mrs Cargill died in 1951. He died on 13 December 1955 aged 89, survived by his three daughters. He had lived at 63 Highland Heath, Putney. Cargill frequently contributed reports of unusual cases to the Transactions of the Ophthalmological Society. He was of middle height and handsome appearance.