Born Apr. 2, 1866, in St. Petersburg; died Mar. 6, 1938, in Leningrad. Soviet meteorologist and hydrologist; organizer of aerological research in Russia. He studied first at the University of St. Petersburg and then at Moscow University, where he did his initial scientific work under the supervision of N. E. Zhukovskii. He worked at the Main Physics Observatory (1894–1919 and 1924–27) and then at the State Hydrological Institute (1929–38). He organized Russia’s first kite station in 1902 in Pavlovsk; it was reorganized in 1912 as the Aerological Observatory, which he headed until 1919. He developed methods for determining the height of clouds and for sounding the atmosphere, and he designed a number of aerological and hydrological instruments.