E. 1. From 798 to 816 he attests charters with great regularity (Kemble, Codex Diplomaticus, passim). In 798 he was present at a synod at Clovesho, and in 801 at another held at Chelsea. He attended the famous council at Clovesho in 803, and about the same time received a letter of advice from Alcuin, who had heard of Tidferth's exemplary life from an East-Anglian abbot named Lull (Mon. Alcuin. ed. Dümmler, p. 739). Tidferth was also present at the council of Chelsea in August 816, which legislated on the method of consecrating churches, electing abbots and abbesses, and forbade the admission of Scots to ministerial functions (Cotton. MS. Vespasian A. xiv. f. 147; Wilkins, Concilia, i. 169–71). After 816 there is no trace of a bishop of Dunwich until 824, by which time Tidferth was dead. He must be distinguished from a contemporary Tidfrith or Tilferd, the last bishop of Hexham who held that see at the beginning of the ninth century (Richard of Hexham, Surtees Soc. p. 45).
[Petrie's Mon. Hist. Brit. p. 618; Kemble's Codex Diplomaticus; Wilkins's Concilia; Le Neve's Fasti, ed. Hardy, ii. 457; Haddan and Stubbs's Councils, passim; Bishop Stubbs in Dict. Christian Biogr.]
TIDY, CHARLES MEYMOTT (1843–1892), sanitary chemist, was born on 2 Feb. 1843, and was the son of William Callender Tidy, M.D., of South Hackney and his wife, Charlotte Meymott. After attending two small private schools he passed through the Hackney church of England school, and then entered as a student at the London Hospital under Henry Letheby [q. v.], becoming M.R.C.S. and L.S.A. in 1864. In 1865 he entered the university of Aberdeen, and in 1866 graduated C.M. and M.B. with the highest honours. On his return to London he took up his father's medical practice at Hackney, and continued in practice for about ten years. During this period he was also associated at the London Hospital with Dr. Letheby as joint lecturer in chemistry, and under his influence gradually became interested in questions of sanitary reform and public health. On the death of Letheby in 1876 Tidy succeeded to his appointments as professor of chemistry, medical jurisprudence, and public health, and was afterwards called to the bar and appointed reader in medical jurisprudence to the inns of court. He also became public analyst and deputy medical officer of health for the city of London, medical officer of health for Islington, and official analyst to the home office.
In addition to discharging his official duties, Tidy chiefly turned his attention to sanitary questions, and especially to those dealing with water supply and the treatment of sewage, and gained a high reputation and a large practice as an expert in matters of this kind. In 1879 he published a paper on ‘The Processes for determining the Organic Purity of Potable Waters’ (Journal of the Chemical Society, 1879, p. 46), in which he proposed a modification of Forchammer's original process for determining the amount of organic matter in waters by oxidation with potassium permanganate. This method is now generally employed by water analysts, and is usually known as ‘Tidy's process.’ In 1880 he published an elaborate paper, entitled ‘River Water’ (Journ. Chem. Soc. 1880, p. 268), and in 1881 he was appointed by the London water companies, along with Professor Odling and (Sir) William Crookes, to examine the quality of the water supplied to the metropolis. He died at his residence in London on 15 March 1892.
In 1875 he married Violet Fordham Dobell, by whom he had a son and a daughter, both of whom survived him.
Tidy, whose views on sanitary questions were invariably moderate and sound, was the author of a number of works dealing with legal medicine and chemical science, and also published a number of papers and pamphlets which are chiefly concerned with technical subjects. The most important of his publications, in addition to those to which reference has already been made, are: 1. ‘A Handy Book of Forensic Medicine and Toxicology’ (with W. B. Woodman), 1877. 2. ‘A Handbook of Modern Chemistry,’ 1878. 3. ‘Legal Medicine,’ 2 vols. 1882–3. 4. ‘The Story of a Tinder Box,’ 1889. 5. ‘Medical Law for Medical Men’ (with P. Clarke, LL.B.), 1890. Tidy also published the following lectures and papers: 6. ‘Coal and its Products,’ two lectures, 1867. 7. ‘An Analysis of Human Milk’ (‘London Hospital Reports’), 1867. 8. ‘On Poisoning by Colocynth’ (‘Lancet’), 1868. 9. ‘On Poisoning by Opium’ (‘Medical Times and Gazette’), 1868. 10. ‘Development: an Introductory Lecture at the London Hospital,’ 1869. 11. ‘Reports on Chemistry’ in Dobell's ‘Reports on the Progress of Medicine,’ 1869–70. 12. ‘On Ammonia in the Urine in Health and Disease’ with W. B. Woodman, (‘Roy. Soc. Proc.’ 1872, xx. 362). 13. ‘Religion and Health,’ 1874. 14. ‘The Cantor Lectures, 1873, on the Practical Applications of Optics to the Arts and Manufactures and to Medicine,’ 1873. 15. ‘The London Water Supply,’ 1878. 16. ‘The Treatment of Sewage’ (‘Journal of the Society of Arts’),
