(b. Wood Plumpton, England, August 1797; d. Chagres River, Isthmus of Panama, 5 February 1831)
Henry Foster was involved with geophysical observations throughout his career in the British navy. Foster joined the Royal Navy in 1812. Early projects included surveys and, on a trip to South America with Captain Basil Hall, determination of the acceleration of gravity. In 1824 Foster was made lieutenant and became a fellow of the Royal Society. He performed most of his investigations while on expeditions to the Arctic in 1824–1825 and to the South Seas in 1828–1831. He spent the winter of 1824–1825 at Port Bowen, north of the Arctic Circle, as astronomer of an expedition led by Sir William Edward Parry; he studied geomagnetism, the velocity of sound, atmospheric refraction, and the acceleration of gravity. The Board of Longitude printed a detailed account of his observations.1 In 1827 Foster received the rank of commander and the Copley Medal of the Royal Society for these researches. In the spring of 1828 he sailed to the South Seas as commander of a sloop sent on a geophysical expedition, at the suggestion of the Royal Society, to study geomagnetism, gravity, meteorology, and oceanography.
Foster was on many occasions occupied with the indirect measurement of the acceleration of gravity. The project, generally referred to as a determination of the length of a seconds pendulum, was popular at the time and was sponsored officially. Foster used the method recently devised by Henry Kater2 and observed coincidences between a pendulum of known length and the pendulum of a clock whose rate is determined by astronomical transit measurements. The final object of the observations at various latitudes was a determination of the ellipticity of the earth.
Foster was interested primarily in observations and performed them carefully.3 He had a minor interest in theory—he speculated, for example, on the source of the diurnal variation in the earth’s magnetic field. He was in some contact with other scientists: at Port Bowen, for example, he repeated some of Samuel Christie’s experiments at the latter’s request.4
1. Published as Philosophical Transactions of the Royal Society, 26 , pt. 4 (1826).
2. Henry Kater, “An Account of Experiments for Determining the Length of the Pendulum Vibrating Seconds in the Latitude of London,” ibid., 18 (1818), 33–109; “An Account of Experiments for Determining the Variation in the Length of the Pendulum Vibrating Seconds,” ibid., 19 (1819), 336–508.
3. Such was the opinion of Gerard Moll, “On Captain Parry’s and Lieutenant Foster’s Experiments on the Velocity of Sound,” ibid., 28 , pt. 1 (1828), 97–104.
4. Henry Foster, “Account of the Repetition of Mr. Christie’s Experiments on the Magnetic Properties Imparted to an Iron Plate by Rotation...,” ibid., 26 , pt. 4 (1826), 188–199.
I. Original Works. Foster’s writings include “Experiments With an Invariable Pendulum,” in Edinburgh Philosophical Journal, 10 (1824), 91–95, written with Basil Hall; “Account of Experiments Made With an Invariable Pendulum...,” in Philosophical Transactions of the Royal Society, 26 , pt. 4 (1826), 1–70; “Magnetical Observations at Port Bowen,” ibid., 73–117, written with W. E. Parry; and “Observations on the Diurnal Changes in the Position of the Horizontal Needle...,” ibid., 129–176. For a complete listing of Foster’s publications, see the Royal Society of London, Catalogue of Scientific Papers, 1800–1863, II (London, 1868), 673–674.
II. Secondary Literature. See Francis Baily, “Report on the Pendulum Experiments Made by the Late Captain Henry Foster, R.N., in His Scientific Voyage in the Years 1828–1831, With a View to Determine the Figure of the Earth,” in Memoirs of the Royal Astronomical Society, 7 (1834), 1–378. An account of Foster’s expedition of 1828–1830, written by the surgeon of the sloop, is William H. B. Webster, Narrative of a Voyage to the Southern Atlantic Ocean, 2 vols. (London, 1834); the appendix contains measurements made on the expedition (II, 211–253). See also Annual Biography and Obituary, XVI (London, 1832), 436–437; and Proceedings of the Royal Society, 3A (1830–1837), 82.