# Dictionary of National Biography, 1885-1900/Beaufoy, Mark

​BEAUFOY, MARK (1764–1827), astronomer and physicist, was the son of a brewer near London, of the quaker persuasion. He began experiments on the resistance of water to moving bodies before he was fifteen, in the coolers of his father's brewhouse, and it was mainly by his exertions that the Society for the Improvement of Naval Architecture was founded in 1791. Under its auspices an important series of experiments was conducted at the Greenland Dock during the years 1793-8 by the care, and in part at the cost, of Colonel Beaufoy. Many useful results in shipbuilding were thus obtained, as well as the first practical verification in England of Euler's theorems on the resistance of fluids. The details were printed in 1834, at the expense of Mr. Henry Beaufoy (son of the author), in a large quarto volume entitled 'Nautical and Hydraulic Experiments, gratuitously distributed to public bodies and individuals interested in naval architecture. In the laborious calculations connected with this work, Beaufoy was materially assisted, up to the time of her unexpected death in 1800, by his gifted wife. His magnetic observations, prolonged (though not altogether continuously) from March 1813 to March 1822, were superior in accuracy and extent to any earlier work of the kind. They served to determine more precisely the laws of the diurnal variation, as well as to fix the epoch and amount of maximum westerly declination in England. This he considered to have occurred in March 1819, for which month the mean deviation of the needle from the true north was 24° 41' 42" W. (Annals of Philosophy, xv. 338). The data accumulated by Beaufoy enabled Lamont in 1851 to confirm his discovery of a decennial period in the amount of diurnal variation, by placing a maximum in 1817 (Pogg. Annal. lxxxiv. 576).
Beaufoy removed from Hackney Wick to Bushey Heath near Stanmore in Hertfordshire towards the close of 1815. It was here that the series of observations on the eclipses of Jupiter's satellites was made, which the Astronomical Society rewarded with its silver medal on 11 April 1827. They embraced 180 immersions and emersions, observed 1818-26, and their value as Sir John Herschel pointed out in his address (Mem. R. A. Soc. iii. 135) was enhanced by the uniformity imparted to them by being the work of one observer, using a single telescope (a 5-foot Dollond), and a single power (86). They were communicated to the society in two papers, printed amongst their 'Memoirs (ii. 129, iii. 69), and reproduced in the 'Astronomische Nachrichten' (Nos. 19 to 82), and gave to the little observatory where they were made a European reputation. Beaufoy was prevented by illness from attending in person to receive the medal, and died at Bushey Heath on 4 May 1827, aged 63. His instruments, consisting of a 4-foot transit, an altitude and azimuth circle (both by Gary), and two clocks, were, by his desire, presented to the Astronomical Society by his son, Lieutenant George Beaufoy (Mem. R. A. Soc. iii. 391).
Beaufoy's military title dated from 20 Jan. 1797, when he became colonel of the Tower ​Hamlets militia. He was admitted to the Royal Society in 1815, was a fellow of the Linnean Society, and one of the earliest members of the Astronomical Society. He was the first Englishman to ascend Mont Blanc, having reached the summit on 9 Aug. 1787, only six days later than Saussure. His 'Narrative' of the adventure was made public in 1817 (Ann. Phil. ii. 97). He was a constant contributor to the 'Annals of Philosophy' from 1813 until 1826, The whole of his astronomical, meteorological, and magnetic observations appeared in its pages, besides miscellaneous communications of scientific interest, of which a list, to the number of twenty-eight, will be found in the Royal Society's 'Catalogue of Scientific Papers.'
A. M. C.