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GYPSUM&emsp; In Turkey, as also in England, Finland and Italy, the gypsy calls himself "rom" (man or husband), from which come " romni " (female gypsy — woman or wife) and the adjective "rómano" (gypsy). This may account for the supposed Egyptian origin of the race, the ancient Egyptian "rome" being man. They were traced as late as 1417 from the east through Germany, Switzerland, Italy and France; while in 1447 they reached Spain; Poland and Russia about 1501; Sweden in 1512; and England in 1514. They have been protected by kings, popes and nobles; Emperor Sigismund, Pope Martin V, an Earl of Surrey, James IV and Archduke Joseph of Austria being among the number of their friends. They have also been persecuted in many countries, charged with kidnapping children and acting as spies. They number in Europe about 700,000. Asia has thousands of them, and they are constantly emigrating to the United States and Australia. See Borrows' Rómany-Rye.  Gyp′sum. Gypsum is a mineral composed of lime sulphate in combination with water. Translucent varieties are known as selenite, and very fine grades of the material, of white color and special luster, are known as alabaster. When heated, the water of the gypsum escapes and the mineral becomes a white powder. If moistened, this powder "sets." This material is known as plaster of pans, the name being due to the fact that gypsum was early used near Paris for the making of plaster or cement. Plaster is also used as a fertilizer on land. Gypsum occurs in various states of the Union, notably Iowa. Kansas, Michigan, New York, Ohio and Texas. It is also worked to some extent in Arizona, California, Colorado, Montana, Oklahoma, Oregon, South Dakota, Utah, Virginia and Wyoming. The workable beds of gypsum are deposited in salt lakes. As the salt water becomes more and more concentrated, the gypsum is precipitated before the salt. Gypsum is therefore often associated with salt-deposits, but since it is often deposited from water which is not saturated with salt, it is sometimes precipitated from lakes which never deposit salt. Gypsum occurs in many sedimentary rocks in the form of single crystals or in groups of crystals. In some parts of the west, as in parts of New Mexico, the gypsum occurs at the surface, and its fine particles are blown about like sand, making dunes.  

Gyroscope (jī′rō-skōp), an instrument used to illustrate many of the phenomena which occur in the dynamics of rotation. It consists of a flywheel with a heavy rim, supported in such a way that it may rotate freely about any one of three axes, each at right angles to the other two. The instrument was designed by Bohnenberger (1817) and perfected largely by Foucault (1852) for the purpose of illustrating the various motions of the earth, especially the stability of the axis of rotation, the rate of rotation and the precession of the equinoxes.

The theory of the gyroscope is too intricate for our limited space. For an attractive elementary presentation of this subject, see Worthington's Dynamics of Rotation or Perry's Spinning Tops.

The accompanying figure shows what is perhaps the simplest and most beautiful of gyroscopes, namely, Maxwell's dynamical top. This instrument is supported at its center of gravity, and the three axes about which it may rotate all intersect at this point of support. An ordinary top is merely a gyroscope which is supported below the center of gravity and on a plane. 