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 the cylinders to force the water out, so that the men could work at the bottom of the cylinders, as in a diving-bell. As the material was excavated from the space covered by the cylinders they sank by their own weight. An ‘air-lock’ provided the means of ingress and egress to the cylinders. An account of the work was read by Hughes before the Institution of Civil Engineers in 1851 (cf. Proceedings, x. 353, also published separately). It was afterwards pointed out that the same method had been previously used in France, though on a very small scale.

Potts died on 23 March 1850. He married, in 1820, Miss Anne Wright, of Lambessow, Cornwall. Four daughters and two sons, John Thorpe and Benjamin L. F., both of whom were trained as engineers at the London Works, Smethwick, near Birmingham, under Fox & Henderson, survived him.

[Authorities cited and obituary notice by Hyde Clarke in English's Mining Almanack, 1851, p. 198.]  POTTS, ROBERT (1805–1885), mathematician, the son of Robert Potts, and grandson of the head of a firm of Irish linen-weavers, was born at Lambeth in 1805. He entered Trinity College, Cambridge, in 1828 as a sizar, and graduated B.A. as twenty-fifth wrangler in 1832, proceeding M.A. in 1835. He became a successful private tutor in the university, and was a strenuous advocate of most of the university reforms that were carried in his time. He acquired wide reputation as the editor of Euclid's ‘Elements,’ which he brought out in a large edition in 1845, followed in 1847 by an appendix. His school edition appeared in 1846, and was republished in 1850, 1861, 1864, and 1886; a separate edition of book i. appeared in 1884. The book had an immense circulation in the British colonies and in America, and the William and Mary College of Virginia conferred the honorary degree of LL.D. upon Potts ‘in appreciation of the excellence of his mathematical works.’ The merits of his edition of Euclid consisted in the clear arrangement and division of the component parts of the propositions, and in the admirable collection of notes. Potts died at Cambridge in August 1885.

His other publications include: 1. ‘A View of Paley's Evidences and Horæ Paulinæ,’ 1850. 2. ‘Liber Cantabrigiensis,’ 2 pts. 1855–63, 8vo. 3. ‘Aphorisms, Maxims,’ &c., 1875. 4. ‘Open Scholarships in the University of Cambridge,’ 1866; 2nd edit., 1883. 5. ‘Elementary Arithmetic, with Historical Notes,’ 1876. 6. ‘Elementary Algebra, with Historical Notes,’ 1879. He also edited the 1543 edition of William Turner's ‘Huntyng and Fyndyng out of the Romish Fox,’ 1851, and ‘King Edward VI on the Supremacy … with his Discourse on the Reformation of Abuses,’ 1874, and other theological works.

[Times obituary, 7 Aug. 1885; information kindly given by his sister, Mrs. Sophia Rees Williams.]  POTTS, THOMAS (fl. 1612–1618), author of the ‘Discoverie of Witches,’ was brought up under the care of Sir Thomas Knyvet, lord Knyvet of Escrick [q. v.] He adopted the legal profession, and resided in Chancery Lane. In 1612 he went as clerk on circuit with Sir James Altham and Sir Edward Bromley, barons of the exchequer, and officiated at the trial of the famous Lancashire witches at Lancaster on 12 Aug. At the judges' request he compiled an account of the proceedings, which Bromley corrected before publication. It appeared in the following year under the title ‘The Wonderfull Discoverie of Witches in the Countie of Lancaster,’ &c., London, 1613, 4to. In the dedication to Sir Thomas Knyvet, Potts speaks of it as the first fruit of his learning. It was reprinted by Sir Walter Scott in ‘Somers Tracts,’ 1810 (iii. 95–160), and again by the Chetham Society in 1845, with an introduction by James Crossley. Scott refers to it in his ‘Letters on Demonology and Witchcraft,’ and it furnished the groundwork of Harrison Ainsworth's ‘Lancashire Witches,’ in which Potts is a prominent character. He was subsequently granted (17 April 1618) the office of collector of forfeitures on the laws concerning sewers.

[Introd. to Chetham Soc. Publ. vol. vi.; Cal. State Papers, Dom. Ser. 1611–18, p. 535; various editions of ‘The Discoverie’ in Brit. Mus. Libr.; Hazlitt's Handbook, p. 325.]  POTTS, THOMAS (1778–1842), compiler, born in 1778, was son of Edward Potts (1721–1819) of Glanton, near Alnwick, Northumberland (Gent. Mag. 1819, i. 279). Thomas was a solicitor, and at one time was connected with Skinners' Hall. In 1803 he was residing in Camden Town. Subsequently he seems to have lived at Chiswick and other places, and to have had chambers in Serjeants' Inn. He died at Upper Clapton on 8 Nov. 1842.

Potts published: 1. ‘A Compendious Law Dictionary, containing both an explanation of the terms and the law itself, intended for the use of country gentlemen, the merchant, and the professional man,’ 1803, dedicated to Lord Ellenborough; it was reissued