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BROUN, JOHN ALLAN (1817–1879), magnetician and meteorologist, was born on 21 Sept. 1817 at Dumfries, where his father kept a preparatory school for the navy. He entered the university of Edinburgh on his father's death (about 1837). There his turn for physical science attracted the friendship of Professor J. D. Forbes. Through his recommendation he was appointed in April 1842 vdirector of the magnetic observatory founded by Sir Thomas Brisbane at Makerstoun, and, after a short preparatory course of training at Greenwich, entered upon his task with an enthusiasm which quickly widened its scope, and gave to the establishment a high rank among those engaged in simultaneous observations on the plan advocated by Humboldt. Throughout the years 1844-5 observations with all the magnetic and meteorological instruments were made hourly (except on Sundays) ; and though the term originally fixed for the extended activity of the observatory expired in 1846, a limited series of observations was continued for three years longer under Broun's direction, and after his departure until 1855. The preparation of the results for the press cost him much ungrateful toil in developing and testing new methods of correction, which have been generally adopted, and entitle him to a place among the founders of the new observational science of terrestrial magnetism. The data thus laboriously provided, which were of permanent and standard value, appeared under his editorship as volumes xvii. to xix. of the 'Transactions of the Royal Society of Edinburgh' (1845-50), with an appendix, edited by Professor Balfour Stewart (supplement to vol. xxii. 1860).

Broun left Makerstoun in the autumn of 1849, and spent the winter in Edinburgh engaged in completing the reduction of his observations with the aid of his friend and assistant, Mr. John Welsh, afterwards director of the Kew Observatory. In 1850 he went to Paris, where he married Isaline Vallouy, daughter of a clergyman of Huguenot extraction in the Canton du Vaud, by whom he had three sons and two daughters. In the following year he was nominated, at the instance of Colonel Sykes, director of the Trevandrum Magnetic Observatory, founded by the Rajah of Travancore in 1841, and entered upon his arduous duties there in January 1852. Nor did he limit himself to those officially committed to him, but aimed at promoting the general welfare of the province. He established a museum, issued an amended almanac, attempted a reform of weights and measures, planned and superintended the construction of public gardens, a road to the mountains, and a sanatorium. Renewing in 1855 an experiment partially carried out on the Cheviot hills in the summer of 1847 (Report Brit. Assoc. 1847, ii. 19 ; 1850, ii. 7), he built an observatory on the Agustia Malley, the highest peak of the Travancore Ghats, 6,200 feet above the sea. The difficulties in the way were very great, owing to the wild nature of the country, the presence of wild beasts, the superstitious fears and bodily sufferings of the natives ; and Broun himself caught a chill from the sudden transition of temperature, inducing a permanent deafness, for which he vainly sought medical assistance in Europe in 1860. On his return after two years he found the Agustia observatory in ruins, and rebuilt it in 1863 for the purpose of making a final set of observations with new instruments. The results went to show that both magnetic and barometrical oscillations remain unchanged in character at a height of 6,200 feet, but become during the daytime reduced in amount by one half (Proc. R. Soc. xi. 298).

In April 1865 Broun left India definitively, and during a residence of some years, first at Lausanne, then at Stuttgart, devoted his entire energies to preparing for publication the copious materials at his disposal. His sole recreation was an hour's music with his family in the evenings ; for he played the violin well, and was as an ardent admirer of Beethoven. His insufficient private resources were meantime supplemented by a small pension from the Rajah of Travancore, in whose service he had been a loser in point of interest upon sums advanced for scientific purposes. In 1873 he came to live in London, where in the year following he issued a quarto volume entitled 'Observations of Magnetic Declination made at Trevandrum and Agustia Malley in the Observatories of his Highness the Maharajah of Travancore in the years 1852 to 1869.' It contains an exhaustive and highly valuable discussion of the various modes of solar and lunar action on magnetic declination, of which element alone upwards of 300,000 reduced observations were available from the thirteen years of his administration. The publication, however, went no further, and Broun had the mortification of seeing his life's work left incomplete, and the fruits of his anxious toils lying, for the most part, useless. He had never been a prosperous, and he was henceforth a disappointed man. A devoted adherent of the Free church of Scotland, his scruples about subscription had debarred him from professional employment in his native country, and his deafness hindered his promotion in the branch he had made peculiarly his own. He did not, however, sink into inaction. Aided by a grant from the Royal Society, he undertook to complete the reduction of the magnetic observations made at the various colonial stations. The task was one of vast and undefined extent, and his sense of responsibility for quarterly payments added anxiety to his labour. His health began to give way, and in 1878 he had a nervous attack, from which he never satisfactorily recovered. A trip to Switzerland produced a partial rally, but on 22 Nov. 1879 he died suddenly, at the age of sixty-two.

His character was a peculiarly estimable one. He united amiability and social charm with rigid integrity and a sensitiveness of conscience ill fitted to advance his material interests. His scientific merits did not receive the cordial recognition they deserved. He took a prominent part in ascertaining the laws of terrestrial magnetism. The discovery is entirely due to him that the earth loses or gains magnetic intensity as a whole in other words, that the changes in the daily mean horizontal force are nearly the same all over the globe. This conclusion, arrived at through a laborious investigation, was first published in a letter to Sir David Brewster, written from Trevandrum on 21 Dec. 1857 (Phil. Mag. xvi. 81, August 1858). In the same communication the existence of a magnetic period of twenty-six days, attributed to the sun's rotation, was announced, and the evidence on both points was detailed in a paper read before the Royal Society of Edinburgh on 4 Feb. 1861 (Trans. R. Soc. Ed. xxii. pt. iii. 511). Independently of, though subsequently to Kreil, Broun deduced from the Makerstoun observations the fact of a lunar-diurnal influence on the declination-needle (Report Brit. Assoc. 1846, ii. 32), a prolonged study of which showed him that it varied in character with the position of the sun (Proc. R. Soc. x. 484, xvi. 59), and in. amount inversely as the cube of the distance of the moon (Trans. R. Soc. Ed. xxvi. 750). He early defined the annual period of magnetic intensity as consisting of a maximum near each solstice, with minima at the equinoxes (Report Brit. Assoc. 1845, ii. 15) ; gave the first complete account of the daily variations of the needle at the magnetic equator (ib. 1860, ii. 21), and reached, in the course of these discussions, the remarkable conclusion that great magnetic disturbances proceed from particular solar meridians.

His researches contributed largely to establish meteorology on a scientific basis. He discovered the 26-day period of atmospheric pressure, showed the wide range of simultaneous barometrical fluctuations, initiated the systematic study of variously elevated cloud-strata, and indicated the connection between atmospheric movements and isobaric lines (Proc. R. Soc. xxv. 515). But he lacked the power of placing his ideas in a striking light, and the independence of his character did not permit him to purchase applause for himself by flattering the opinions of others. The Royal Society admitted him as a member in 1853, and awarded him a royal medal in 1878. His communications to the Royal Society of Edinburgh were honoured with the Keith prize in 1861.

The Royal Society's 'Catalogue of Scientific Papers' enumerates (vols. i. and vii.) fifty-one of his productions, besides which he contributed to the 'Philosophical Transactions' a paper 'On the Variations of the Daily Mean Horizontal Force of the Earth's Magnetism produced by the Sun's Rotation, and the Moon's Synodical and Tropical Eevolutions' (clxvi. 387, 1876) ; to the 'Transactions of the Royal Society of Edinburgh' an elaborate treatise 'On the Decennial Period in the Range and Disturbance of the Diurnal Oscillations of the Magnetic Needle, and in the Sunspot Area,' assigning as the length of that period 10.45 years (xxvii. 563, 1876), with a 'Note on the Bifilar Magnetometer' (xxviiii. 41). He wrote frequently in 'Nature.' His 'Reports' on the Makerstoun and Travancore observatories were published respectively at Edinburgh in 1850, and at Trevandrum in 1857. He exhibited at the Loan Exhibition of Scientific Instruments in 1876 a 'gravimeter' of his own invention, described by Major J. Herschel in 'Proceedings of the Royal Society,' xxxii. 507.

[Nature, xxi. 112 (Balfour Stewart); Proc. R. Soc. xxviii. 65, xxx. iii.]

A. M. C.