neighbourhood. In 1870 the population was 15,830, mostly Magyars by nationality. The Hungarians defeated
the Austrians at Gyongybs on the 3d April 1849.GYÖNGYÖSI, István or Stephen (1620–1704), one of the most talented Hungarian poets of the 17th century, was born of poor but noble parents in 1620. The county of his birth is variously given as Gomor or Bons, tho date as August 5 or November 3. His abilities early attracted the notice of Count Ferencz Wessele"nyi, who in 1640 appointed him to a post of confidence in Fiilek eastle. Here he remained till 1653, when he married, and commenced his public career as an assessor of the judicial board. lu 1681 ho was elected as a representative of his county at the diet held at Soprony (Oedenburg). From 1JS6 to 1693, and again from 1700 to his death in 1704, he was deputy lord-lieutenant of the county of Gomor. Of his literary works .the most famous is the epic poem Murdnyi Venus (Caschau, 1664), which hymns the praises of his benefactor s wife Maria Sze csi, the heroine of Murany. Among his later productions the best known are Rozsa-Koszoni, or Rose-Wreath (1690), Kemeny-Jdnos (1693), Cupido (1695), Palinodia (1695), and ChariUia (1700). His poems are chietly remarkable for energy, feel ing, and popular sentiment. The earliest edition of his collected poetical works is by Dugonics (Pressburg and Pesth, 1796) ; the best modern selection is that of Toldy, entitled Gyongyosi Istvdn vdlogatott poetai munkdi (Select poetical works of Stephen Gyongyosi), 2 vols., 1864-65.
GYPSUM, the hydrated sulphate of lime, CaS0 4 .2H 2 O, is a mineral substance occurring in various rock formations, especially in Tertiary deposits, in very considerable abund ance and under varying conditions. In its transparent crystalline state it is known as selenite ; when it presents a finely fibrous opalescent appearance, it is termed satin spar ; and the name alabaster is reserved for the pure milky white massive varieties. Gypsum is very generally disseminated, the most famous locality for the finer qualities worked into alabaster vases and figures being Castelino, about 30 miles from Leghorn ; while Montmartre, Argenteuil, and other places in the environs of Paris, and in the neighbourhood of Derby in England, furnish inexhaustible supplies chiefly for the preparation of plaster of Paris and for agricultural use, <fec. It is also found in large quantities in Nova Scotia, New York, Virginia, and Michigan. The application of gypsum as a manure is referred to under Agriculture, vol. i. p. 351, and ita employment for ornamental purposes is described under Alabaster, vol. i. p. 439. The preparation of plaster of Paris, so called from the fact that the industry chiefly centres in several Parisian suburbs, is the principal primary object of the quarrying or mining of gypsum. By the application of heat gypsum begins, at a temperature of about 175 Fahr., to part with its combined water. An increase of temperature causes the desiccation to proceed with great rapidity, and for manufacturing purposes the best results are obtained at from 230 to 250. For making plaster of Paris, gypsum is burnt in kilns at about the latter temperatures, and subsequently it is powdered and ground to a fine uniform flour. So prepared it possesses the valuable property of recombining with water when mixed with it, and setting, from a thin paste, into a solid mass, the phenomenon being accompanied with some ex pansion and the evolution of heat. It is to this property of recombining with water that the value of plaster of Paris is principally due. When, however, gypsum is burnt at a temperature of 480 and upwards, the sulphate rehydrates only with great difficulty, and at still higher temperatures it loses all power of absorbing water, and in this respect it then resembles anhydrite, the natural water-free sulphate of lime. Plaster of Paris is largely used for obtaining copies of statuary figures, coins, medals, sculptures, and carvings, and also for taking casts from natural objects. It is also employed as the material for moulds for electro- deposits, and for the manufacture of embossed and pressed pottery ware. Still more extensively is it consumed in the finishing of internal plaster work in houses, and for making cornice mouldings and other architectural enrichments in positions sheltered from the weather. Plaster of Paris work is, like gypsum, soluble in water at a temperature of 32 to the extent of 205 per cent., rising to a maximum solubility of 254 at 95 Fahr. Plaster casts made simply with water are soft, porous, and easily injured, and various plans have been devised for producing a harder and more compact body with plaster. Keene s cement, which may be taken as a type of the hardened plasters, is made by treat ing the burnt gypsum with a solution of 1 part of alum to 12 of water at a temperature of about 95. After about 3 hours the plaster is removed, dried, and rebaked in the furnace, and then thoroughly ground and powdered. Thus prepared, the plaster needs comparatively little water to slake it, and it sets much more slowly than the ordinary plaster, while the comparative tenacity of the two varieties is as 1*5 to 1. Parian cement is plaster hardened with water containing 10 per cent, of borax ; and stucco is plaster rendered tenacious by being prepared with a strong solution of glue. When water containing lime or a solution of gum-arabic is used to slake burnt gypsum, a hard plaster is also obtained, which by smoothing, colouring, and sub sequent polishing with oil assumes a marble-like surface. A fair imitation of meerschaum is also made in hardened plaster by polishing, tinting the surface with a solution of gamboge and dragon s-blood, and treating it with either melted paraffin or stearic acid. It is understood that the cheaper " meer schaum " pipes and cigar-holders are thus prepared.
GYROSCOPE, GYROSTAT, are names given to instru ments which are used to demonstrate certain properties of rigid bodies, when made to rotate rapidly about the axis round which they are kinetically symmetrical.
In some of its forms the gyroscope has been known for a very long time, and is, in all probability, of French or German invention. Almost the first instrument of the kind that we hear of, and of which the present gyroscope is merely a modification, is that of Bohnenberger, which was constructed as early as 1810, and is described in Gilbert s Annalen for 1818 (Ix. p. 60). It consisted of a heavy spheroid which could rotate inside a circular ring round its shorter axis, the axis running on pivots situated at opposite ends of the ring s diameter. This ring, with its contained spheroid, was similarly made movable inside a second ring, and round an axis at right angles to the axis of the spheroid. In the same way this second ring, with its contents, could rotate inside a third ring, and round an axis at right angles to each of the others. From this it will be seen that the spheroid had all degrees of free rota tion, one point only within it being fixed, namely, the intersection of the three axes.
of apparatus, involving the gyroscope principle, have been in use for a number of years for illustrating the precession of the equinoxes, and the parallelism of the earth s axis as it revolves round the sun. An instrument of this kind was given by Arago to Professor Playfair, which must have been in existence since 1816-17. Mention is made of a similar instrument as being brought from Italy to Mr Babbage in 1827. At the close of that year a notice of an instrument akin to the gyroscope made by Mr Henry Atkinson was read before the Astronomical Society. In 1836, in a paper read before the Royal Scottish Society of Arts, Mr Edward Sang, C.E., Edinburgh, suggested an ex periment with an instrument exactly similar to the gyro
scope, by which the rotation of the earth on its axis could
