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STEPHENSON 77 STEREOSCOPE visited South America to inspect the gold and silver mines of that country; and established a name as the first civil en- gineer in Europe. Among the works with which Robert Stephenson's name is associated, are the High Level Bridge over the Tyne, the Tweed Viaduct, the Britannia Bridge over the Menai Straits, the Victoria Bridge at Montreal across the St. La-vrence, one of the grandest of engineering achievements, and the Alex- andria and Cairo railway. In 1847 he entered Parliament for Whitby ; he was a Fellow of the Royal Society, and a mem- ber of nearly all the scientific societies of Europe. He published two valuable works, "The Locomotive Steam Engine," and "The Atmospheric Railway System." He died in London Oct. 12, 1859, and was buried in Westminster Abbey, where there is a memorial window in his honor. STEPNIAK (step'nyak), SERGIUS MICHAEL DRAGOMANOV, a Russian revolutionist; born in Gadjatch, Poltava, Russia, in 1841. Exiled in 1876 on ac- count of his criticisms on the system fol- lowed by Count Tolstoy, minister of jus- tice, he settled in Geneva in 1877. Among his works are "The Turks Within and Without" (1876) ; "Underground Rus- sia" (1881) ; "Tyrannicide in Russia" (1881) ; "The Russian Peasantry"; "His- torical Poland and the Muscovite De- mocracy" (1881) ; "Little Russian Inter- nationalism"; "The Propaganda of So- cialism"; "Russia under the Czars"; and "The Career of a Nihilist," a novel (1889). He assisted in editing the folk songs of Little Russia. In 1891 he vis- ited the United States. He died in Lon- don, England, Dec. 23, 1895. STEPPE, a term applied to one of those extensive plains which, with the occa- sional interpolation of low ranges of hills, stretch from the Dnieper across the S. E. of European Russia, round the shores of the Caspian and Aral seas, between the Altai and Ural chains, and occupy the low lands of Siberia. In spring they are covered with verdure, but for the greater part of the year they are dry and barren. There are three different kinds of steppe, viz., grass, salt, and sand steppes, each maintaining peculiar forms of vegetation. STERE (star), the French unit for solid measure, equal to a cubic meter, or 35.3156 cubic feet. STEREO-CHEMISTRY, that branch of chemistry which studies the arrange- ment of the atoms of a molecule in space. 5t concerns itself especially with com- pounds of carbon. Many examples are F known where two compounds are found to consist not only of the same atoms but of the same groups of atoms, and yet they differ in their properties, both chem- ical and physical. For instance, both fumaric acid and maleic acid have the chemical formula C4H4O4, and the atoms are grouped in this manner: COOH.CH:CH.COOH. The two com- pounds are known as isomers, and the fact that two substances could exist with the same structural formula, and yet be entirely different and distinct compounds for a long time remained unexplained. The solution to the problem was offered by stereo-chemistry. Following the the- ories of Van't Hoff, the carbon atom is conceived as being situated at the center of a regular tetrahedron, the groups com- bined with it being located at the angles. The differing properties of isomers is explained by the theory that the arrange- ment of the groups at the corners, rela- tive to one another, differs in the two compounds. For instance, if a projection were made of the "solid formula" of the two compounds given above, they would appear as: H-C-COOH H-C-COOH H-C-COOH Maleic Acid COOH-C-H Fumaric Acid STEREOCHROMY, a process of mural painting in which water glass is em- ployed to fix or consolidate the colors. It has not proved successful. STEREOPTICON, a magic lantern having two objective tubes that can be focused on the same part of a screen, and by the alternate projection of pictures from the separate tubes produce the well-known phenomena of "dissolving views." STEREOSCOPE, a simple and once popular optical contrivance, by which two flat slightly dissimilar pictures of an object are fused into one image, having the actual appearance of relief. A re- flecting form of the stereoscope was in- vented by Professor Wheatstone in 1838. Subsequently Sir David Brewster in- vented the refracting or lenticular stereo- scope, based on the refractive properties of semidouble convex lenses; and this instrument, of which there are numerous forms came into general use. ^ Convex lenses magnify the pictures besides pro- ducing a stereoscopic effect. Photogra- phy greatly assists the stereoscope in providing perfectly accurate right-and- left monocular views, which are taken simultaneously on a plate in a twin camera. Several modifications of the re- Cyc— Vol. IX