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358 —Works on the gypsies and their dialects are: Valentge's “Description of the East Indies” (Amsterdam, 1724-'6); Peyssonel, Sur les peuples barbares qui ont habité sur les bords du Danube (1765); Pray, Annales Regum Hungariæ (5 vols. fol., Vienna, 1764-'70); Grellmann, Historische Versuche über die Zigeuner (Göttingen, 2d ed., 1787); Molnár, Specimen Linguæ Cingaricæ (Debreczin, 1798); Gardiner, “Essays, Literary, Political,” &c. (Edinburgh, 1803); Hasse, Zigeuner im Herodot (Königsberg, 1803); Bischoff, Deutsch-Zigeunerisches Wörterluch (Ilmenau, 1827); John Staples Harriot, in the “Transactions of the Asiatic Society” for 1831; Cogalniceano, Esquisse sur l'histoire, les mœurs et la langue des Cigains (Berlin, 1837); Predari, Origine e vicende dei Zingari (Milan, 1841); George Borrow, “The Zincali, or an Account of the Gypsies of Spain” (2 vols., London, 1841); Von Heister, Ethnographie und geschichtliche Notizen über die Zigeuner (Königsberg, 1842); Pott, Die Zigeuner in Europa und Asien (Halle, 1844-'5); Bataillard, De l'apparition et de la dispersion des Bohémiens en Europe (in the 5th vol. of the Bibliothèque de l'école de Chartres, 1844); Böhtlingk, Die Sprache der Zigeuner in Russland (St. Petersburg, 1852); Jimenez, Vocabulario del dialecto jitano (Madrid, 1854); Liebich, Die Zigeuner in ihrem Wesen und in ihrer Sprache (Leipsic, 1863); Ascoli, Ziguenerisches (Halle, 1865); Simson, “History of the Gypsies” (London, 1865); Kivasnikoff, “Collection of Songs of the Russian Gypsies,” in Russian (Moscow, 1869); Borrow, “Lavo-Lil: Word Book of the Romany or English Gypsy Language” (London, 1874); and numerous articles in the publications of philological societies.  GYPSUM, a common mineral, frequently crystallized, oftener amorphous, and sometimes forming rock masses. Its crystallization is monoclinic; hardness, 1.5 to 2; specific gravity, 2.2 to 2.4; transparent or translucent, vitreous; on cleavage, pearly or silky; colorless and snow-white, but often red, yellow, or brown from enclosed coloring matters. Its transparent variety, called selenite, sometimes occurs in large plates, which have been used for windows. It also frequently occurs in aggregated needle-like crystals, and is then called fibrous gypsum. In its amorphous condition, when compact and translucent, it is named alabaster. More commonly it is white, opaque, and soft, and is then called snowy gypsum. Its chemical composition is expressed by the formula CaSO4, 2H2O; i. e., it is a hydrated sulphate of lime. Gypsum occurs in nearly all geological formations and countries. In clay and shale it is frequently found in beautifully defined detached crystals, apparently derived from the action of sulphuric acid, liberated by the decomposition of iron pyrites on carbonate of lime. It is also formed where sulphuric acid is generated or discharged from volcanic or other subterranean sources and comas in contact with calcareous matter,

as about sulphur springs and craters of volcanoes. The great repository of gypsum, however, is the water of the ocean, which always holds it in solution, and from which it has been precipitated by evaporation to form all the great masses of this substance. It is also soluble in fresh water in the proportion of 1 part to 400 or 500 of water. The most important deposits known are those of the Paris basin at Montmartre, which are of eocene age, and from which it has taken the common name of plaster of Paris; those of Nova Scotia, Virginia, and Michigan, of carboniferous age; of central New York, Ohio, and Canada West, in the upper Silurian; and in the triassic strata of the far west. It also occurs in the trias at Bex in Switzerland, Vic and Dieuze in France, Cheshire in England, and Stasfurt in Germany. In all these, as in the most important American localities, it is associated with rock salt. Gypsum is known to exist in large quantities in Mexico, South America, Africa, India, Australia, and China.—The origin of the great masses and strata of gypsum found in many countries has been a subject of much discussion. By most writers they are represented to have been produced by the action of sulphuric acid contained in the water of acid springs acting upon strata of limestone. This theory is, however, inapplicable to all the most important deposits, which are undoubtedly derived from the precipitation of gypsum by evaporation from its solution in circumscribed basins of salt water, like the Dead sea and Great Salt lake. This is apparent in the structure of the gypsum beds, which are generally accurately stratified, and not unfrequently alternate with sheets of limestone. Gypsum is also usually associated with greater or less quantities of the salts which are found in sea water, viz., the chlorides of sodium, calcium, magnesium, the sulphate of soda, &c. Of all the solid matter contained in sea water, gypsum is the least soluble, and therefore is the first precipitated. It is thus deposited by itself, and forms continuous and regular strata many miles in extent and of great thickness. The next ingredient which would be thrown down in the evaporation of sea water is the chloride of sodium; and this we find in the strata of rock salt which accompany beds of gypsum. The other salts mentioned have such an affinity for water that they are not found solid, but compose the bitterns of the brines of wells and springs. In New York, Canada, and Ohio, gypsum occurs chiefly in the Salina or Onondaga salt group. This formation is made up of a series of earthy sediments interstratified with salt and gypsum, and is plainly the deposit which accumulated at the bottom of a great salt lake, which in the Silurian age reached from eastern New York to the Cincinnati axis. In the western part of this basin, at Sandusky, Ohio, the Salina group contains sheets of regularly bedded strata of gypsum, divided horizontally by thin sheets of 