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 died on 4 Aug. 1883. A portrait of Leach was exhibited at the Loan Collection of National Portraits at South Kensington in 1868 (Cat. No. 222), and there is a fine mezzotint of him by Dawe after Penny (Notes and Queries, 5th ser. vi. 273). Some of Leach's equity pleadings, signed ‘J. L.,’ were printed in F. M. Van Heythuysen's ‘Equity Draftsman’ (London, 1816, 8vo). His speech of 31 Dec. 1810 on the regency resolutions was published in 1811 (London, 8vo, second edition). 

LEACH, THOMAS (1746–1818), legal writer, born in 1746, was called to the bar from the Middle Temple. In 1790 he was appointed police magistrate at Hatton Garden, and was also chairman of the county court of requests in Fulwood's Rents, Holborn. He was an able lawyer, but ill-health made him irritable. He sent in his resignation in November 1818, and died unmarried on 31 Dec. following.

He published:
 * 1) ‘Considerations on the matter of Libel, suggested by Mr. Fox's Notice in Parliament of an intended Motion on that subject,’ 8vo, London, 1791.
 * 2) ‘Reports of Sir George Croke,’ 4th edit. 3 vols. 8vo, London, 1790–2.
 * 3) ‘Modern Reports, or Select Cases adjudged in the Courts of King's Bench, Chancery, Common Pleas, and Exchequer, from the Restoration of Charles II to the 28th of George II,’ 5th edit. 12 vols. 8vo, London, 1793–6.
 * 4) ‘Sir B. Shower's Reports of Cases adjudged in the Court of King's Bench during the reigns of Charles I, James II, and William III,’ 2nd edit. 2 vols. 8vo, London, 1794 (3rd edit. 1836).
 * 5) ‘Hawkins's Pleas of the Crown, 7th edit., digested under proper heads,’ 4 vols. 8vo, London, 1795.
 * 6) ‘Cases in Crown Law determined by the Twelve Judges, by the Court of King's Bench, and by Commissioners of Oyer and Terminer, and General Gaol Delivery, 1730–1815,’ London, 1789, 1792, 1800, and in 2 vols. 8vo, 1815.

Leach was for some years editor of the ‘Whitehall Evening Post.’ His portrait has been engraved by Audinet. 

LEACH, WILLIAM ELFORD (1790–1836), naturalist, born at Plymouth in 1790, after studying medicine under Abernethy at St. Bartholomew's Hospital, London, proceeded to Edinburgh, where he graduated M.D. in 1812. Abandoning his profession shortly after taking his degree to devote himself to natural history, he was in 1813 appointed assistant librarian, and had risen by 1821 to be assistant keeper of the natural history department in the British Museum. In 1815 he published the first part of his excellent history of British crustacea, which was never completed. Meanwhile he laboured at the British Museum with great zeal. The introduction of the natural system of arrangement in conchology and entomology, on the lines of Latreille and Cuvier, as opposed to the artificial system of Linnæus, was mainly due to his initiative. Though he made many new discoveries among the various classes of vertebrates, especially birds, it was in entomology and malacology that his labours bore the most fruit, his knowledge of crustacea being superior to that of any other naturalist of his time. His arrangement was, it is true, far from faultless, and was superseded by that of Henri Milne-Edwards, in his ‘Histoire Naturelle des Crustacés,’ 1834; but the French naturalist gave high praise to Leach as the one of his predecessors to whom subsequent investigators in the same field would always owe the highest obligation. Unfortunately Leach's studies injured his health, and his brain becoming affected he was compelled in 1821 to retire from his post at the museum. For the last few years of his life he resided with his sister in Italy, resumed to some extent his favourite occupations, and wrote letters of interest on scientific subjects to his friends in France and in England. He died suddenly of cholera on 25 Aug. 1836, at the Palazzo St. Sebastiano, near Tortona.

‘Few men,’ says Dr. Boot, in the ‘Anniversary Notice of Members of the Linnean Society,’ 1837, ‘have ever devoted themselves to zoology with greater zeal than Dr. Leach, or attained at an early period of life a higher reputation at home and abroad as a profound