for the bar, but devoted his life to the study of archæology and the collection of works of art. His collections, which he kept at his house, 3 Montague Street, Bloomsbury, were extremely valuable, and were formed with learned discrimination. He was an excellent artist, and was a fellow of the Society of Antiquaries and other archæological societies, and a frequent attendant at their meetings and contributor to their ‘Proceedings.’ He died unmarried in 1878. By the codicil to his will, dated 1 Nov. 1877, Henderson bequeathed to the university of Oxford all his Greek and Roman vases and Egyptian antiquities; to the trustees of the British Museum his valuable collection of water-colour drawings by Canaletto, Turner, Girtin, Cozens, David Cox, and W. J. Müller (now in the print room), his collection of Russian silver and enamels, his Damascus, Persian, Rhodian, and majolica porcelain and pottery, his oriental and Venetian metal-work, his oriental arms, his Roman, Greek, and Venetian glass (all now in the department of general antiquities), and the correspondence of his grandfather, George Keate, with Voltaire and Dr. Edward Young (now in the department of manuscripts, Addit. MSS. 30991–2). To the trustees of the National Gallery he bequeathed his water-colour drawings by G. Cattermole and P. De Wint, two pictures by A. Canaletto, and any others of his old masters which they might select. Charles Cooper Henderson [q. v.] was his brother.
[Private information.]
HENDERSON or HENRYSON, ROBERT (1430?–1506?), Scottish poet. [See Henryson.]
HENDERSON, THOMAS (1798–1844), astronomer, born at Dundee in Scotland on 28 Dec. 1798, was the youngest of five children of a respectable tradesman, who died early. He was educated at the local schools, and learnt mathematics from Mr. Duncan, principal of the Dundee Academy, who described him as ‘remarkable for everything that was good.’ At the age of fifteen he entered the office of Mr. Small, a writer in Dundee, with whom his brother was in partnership. He was employed partly in classifying the burgh records, and after six years placed himself under a writer to the signet in Edinburgh. His business capabilities there attracted the notice of Sir James Gibson Craig [q. v.], through whose influence he was appointed advocate's clerk to John Clerk, lord Eldin [q. v.], and he acted from 1819 to 1831 as secretary to the Earl of Lauderdale and Lord Jeffrey.
Henderson was of a weak constitution, and at times nearly blind, but seemed to acquire scientific knowledge by intuition (Grant, University of Edinburgh, ii. 362). His familiarity with astronomical methods, acquired during his leisure at Dundee, introduced him to Professors Leslie and Wallace, and to Captain Basil Hall [q. v.] He joined the Astronomical Institution of Edinburgh, and was allowed the use of the instruments in their observatory on the Calton Hill. He showed special dexterity in the computing processes of practical astronomy, and he forwarded to Dr. Thomas Young [q. v.] in 1824 an amended method of calculating occultations, inserted in the ‘Nautical Almanac’ for 1827 and four subsequent years. He received the thanks of the board of longitude for this improvement, which was published in the ‘Quarterly Journal of Science’ (xviii. 344, 1825), and was followed by similar communications.
In a paper ‘On the Difference of Meridians of the Royal Observatories of Greenwich and Paris’ (Phil. Trans. cxvii. 286), sent by him to the Royal Society of London in 1827, he greatly added to the value of Sir John Herschel's result by rectifying an error in the data furnished to him; and his discussion of transit observations made on the Calton Hill in 1827 (Memoirs Royal Astr. Soc. iv. 189) showed his early adoption of the German method of deducing the probable errors of results. The thanks of the Royal Astronomical Society were voted to him in 1830 for various computations, including a list of moon-culminating stars for Sir James Ross's Arctic expedition. He declined all remuneration, although much of his small income was at this time devoted to the support of his mother and sisters.
Henderson's connection with the Earl of Lauderdale involved an annual visit to London, where he made many astronomical acquaintances, and was allowed to use Sir James South's fine instruments. He failed to succeed Dr. Robert Blair (d. 1828) [q. v.] as professor of practical astronomy at Edinburgh in December 1828, although Dr. Young had supported his claims, besides leaving a posthumous recommendation of him as his successor in the superintendence of the ‘Nautical Almanac.’ Pond was nominated; and Henderson, though invited to co-operate on advantageous terms, chose to continue his legal career. On the death of Fearon Fallows [q. v.] in 1831, he was persuaded to become royal astronomer at the Cape of Good Hope, where he arrived in April 1832. The instruments at his disposal were a ten-foot transit by Dollond, and a defective mural circle by Jones (ib[. viii. 141). With Lieutenant Meadows as his sole assis-
