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Originally appearing in Volume V24, Page 238 of the 1911 Encyclopedia Britannica.
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HORACE BENEDICT DE SAUSSURE (1740-1799), Swiss physicist and Alpine traveller, was born at Geneva on the 17th of February 1740.' Under the influence of his father and his maternal uncle, Charles Bonnet, he devoted himself to botany. In 1758 he made the acquaintance of Albrecht von Haller, and in 1762 he published his first work, Observations sur l'ecorce des feuilles et des petales. The. same year he was chosen professor of philosophy at the academy of Geneva, and retained this chair till 1786. His health began to fail in 1791, when too he suffered great pecuniary losses. But he was able to complete his great work in 1796, before his death on the 22nd of January 1799. He became a F.R.S. after his visit to England (autumn of 1768), and in 1772 founded the Societe pour 1'Avancement des Arts at Geneva. His early devotion to botanical studies naturally led him to undertake journeys among the Alps, and from 1773 on-wards he directed his attention to the geology and physics of that great chain. Incidentally, he did much to clear up the topography of the snowy portions of the Alps, and to attract the attention of pleasure travellers towards spots like Chamonix and Zermatt. In 176o he first visited Chamonix, and offered a reward to the man who should first succeed in reaching the summit of Mont Blanc (then unsealed). He made an unsuccessful ' His father, Nicolas de Saussure (1709-1790), an agriculturist of unusually liberal opinions, resided all his life at his farm of Conches, on the Arve, near Geneva. As a member of the council of Two Hundred he took part in public affairs. Most of his writings bear on the growth and diseases of grain and other farm produce. His last work Le Feu, Principe de la fecondite des plantes et de la fertilite de la terre (1782), was more speculative in its nature. The Alps formed the centre of Saussure's investigations. They forced themselves on his attention as the grand key to the true theory of the earth, and among them he found opportunity for studying geology in a manner never previously attempted. The inclination of the strata, the nature of the rocks, the fossils and the minerals received his closest attention. He acquired a thorough knowledge of the chemistry of the day; and he applied it to the study of minerals, water and air. Saussure's geological observations made him a firm believer in the Neptunian theory: he regarded all rocks and minerals as deposited from aqueous solution or suspension, and in view of this he attached much importance to the study of meteorological conditions. He carried barometers and boiling-point thermometers to the summits of the highest mountains, and estimated the relative humidity of the atmosphere at different heights, its temperature, the strength of solar radiation, the cbmposition of air and its transparency. Then, following the precipitated moisture, he investigated the temperature of the earth at all depths to which he could drive his thermometer staves, the course, conditions and temperature of streams, rivers, glaciers and lakes, even of the sea. The most beautiful and complete of his subsidiary researches is described in the Essai sur l'hygrometrie, published in 1783. In it he records experiments made with various forms of hygrometer in all climates and at all temperatures, and supports the claims of his hair-hygrometer against all others. He invented and improved many kinds of apparatus, including the magneto-meter, the cyanometer for estimating the blueness of the sky, the diaphanometer for judging of the clearness of the atmosphere, the anemometer and the mountain eudiometer. His modifications of the thermometer adapted that instrument to many purposes: for ascertaining the temperature of the air he used one with a fine bulb hung in the shade or whirled by a string, the latter form being converted into an evaporometer by inserting its bulb into a piece of wet sponge and making it revolve in a circle of known radius at a known rate; for experiments on the earth and in deep water he employed large thermometers wrapped in non-conducting coatings so as to render them extremely sluggish, and capable of long retaining the temperature once they had attained it. By the use of these instruments he showed that the bottom water of deep lakes is uniformly cold at all seasons, and that the annual heat wave takes six months to penetrate to a depth of 30 ft. in the earth. He recognized the immense advantages to meteorology of high-level observing stations, and whenever it was practicable he arranged for simultaneous observations being made at different altitudes for as long periods as possible. It is perhaps as a geologist (it is said that he was the first to use the term "geology "—see the " Discours preliminaire" to vol. i. of his Voyages, publ. in 1779) that Saussure worked most; and although his ideas on matters of theory were in many cases very erroneous he was instrumental in greatly advancing that science. See Lives by J. Senebier (Geneva, 18oi), by Cuvier in the Biographie universelle, and by Candolle in Decade philosophique, No. xv. (trans. in the Philosophical Magazine, iv. p. 96); articles by E. Neville in the Bibliotheque universelle (March, April, May 1883), and chaps. v.-viii. of Ch. Durier's Le Mont-Blanc (Paris, various editions between 1877 and 1897). (W. A. B. C.)
End of Article: HORACE BENEDICT DE SAUSSURE (1740-1799)

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