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Galle, Johann Gottfried

(Encyclopedia)Galle, Johann Gottfried yōˈhän gôtˈfrēt gäˈlə [key], 1812–1910, German astronomer. He is noted for his discovery of the planet Neptune, Sept. 23, 1846, by following the guidance of calculat...

Hough, George Washington

(Encyclopedia)Hough, George Washington hŭf [key], 1836–1909, American astronomer, b. Montgomery co., N.Y., grad. Union College, 1856. He discovered 627 double stars and made systematic studies of the surface of ...

Saussure, Horace Bénédict de

(Encyclopedia)Saussure, Horace Bénédict de də sōsürˈ [key], 1740–99, Swiss physicist and geologist. He was professor at the Univ. of Geneva from 1762 to 1786. He is famous for his studies of the geology, m...

powder

(Encyclopedia)powder, any mass of fine particles or dust prepared by various mechanical means, e.g., grinding of solid substances, or by chemical means, e.g., precipitation from solutions. In a special sense, the w...

Deluc, Jean André

(Encyclopedia)Deluc, Jean André zhäN äNdrāˈ dəlükˈ [key], 1727–1817, Swiss geologist. During the first half of his life he was engaged mainly in business in Switzerland. He also made scientific excursions...

theodolite

(Encyclopedia)theodolite thēŏdˈəlītˌ [key], calibrated optical instrument used to determine relative position in surveying, navigation, and meteorology. It is similar in construction to a surveyor's transit, ...

mixture

(Encyclopedia)mixture, in chemistry, a physical combination of two or more pure substances (i.e., elements or compounds). A mixture is distinguished from a compound, which is formed by the chemical combination of t...

MacCready, Paul Beattie

(Encyclopedia)MacCready, Paul Beattie, 1925–2007, American engineer and inventor known for his achievements in human-powered flight, b. New Haven, Conn., Ph.D. California Institute of Technology, 1952. In 1997 he...

actinometer

(Encyclopedia)actinometer ăkˌtənŏmˈətər [key], instrument used to measure the heating power of radiation. Actinometers are used chiefly in meteorology to measure solar radiation as transmitted directly by th...

Hoffmann, Friedrich

(Encyclopedia)Hoffmann, Friedrich hôfˈmän [key], 1660–1742, German physician. He taught and practiced at Halle from 1693. He studied and wrote on such varied topics as pediatrics, mineral waters, and meteorol...