GELASIUS II. 276 GEM uated on the S. coast of the island be- tween Agrigentum and Camarina ; found- ed in 690 B. c. by a colony of Cretans and Rhodians. The colony was remarkably prosperous, and in 528 B. C. sent out a portion of its inhabitants, who founded Agrigentum. In 280 Phintias, the tyrant of Agrigentum, utterly destroyed Gela. GELASIUS II., Bishop of Rome (1118- 1119), formerly John of Gaeta. He was educated at the Benedictine abbey of Monte Cassino, was cardinal and chan- cellor under Urban II. and Paschal II., and on the death of the latter was chosen Pope by the party hostile to the Em- peror Henry V. The imperial party at Rome under the Frangipani seized his person, but were forced to set him free by the menacing attitude of the mob. The new Pope fled before the advancing imperial troops to Gaeta, where he first received his consecration, and whence he fulminated the thunders of excommuni- cation against Henry V. and Gregory VIII., the antipope he had set up. Soon after he was able to return to Rome, but ere long had to betake himself for pro- tection to France, where he died in the monastery of Clugny, Jan. 29, 1119. GELATINE, or GELATIN (Latin, gelahis=trozen, so named from the tend- ency which the substance has to congeal and become to a certain extent solid) , in chemistry, CUi.^T^i^^O^.'! Animal glutin, obtained by treating bones with dilute hydrochloric acid, which dissolves the mineral constituents of the bone, con- sisting of phosphates and carbonates of calcium, magnesium, etc., and leaves the bone cartilage. This, when boiled for a long time with water, dissolves, and forms gelatine, which can be purified by dissolving in hot water and precipitating by alcohol. A pure variety is obtained from the swimming bladder of the stur- geon, or other species of Acipenser. Im- pure gelatine, called glue, is prepared by boiling down pieces of hide, horn, hoof, cartilage, etc., with water under pres- sure. Pure gelatine is amorphous, trans- parent in thin plates, of a yellowish- white color; it has neither taste nor smell, and is neutral to vegetable colors; it is insoluble in alcohol and in ether. In contact with cold water it swells up, and is soluble in hot water. Gelatine sub- jected to dry distillation yields methyl- amine, cyanide of ammonium, pyrrol, etc. ; by oxidation with sulphuric acid and manganese dioxide, or with chromic acid mixture, it yields hydrocyanic acid, acids of the fatty series, benzoic aldehyde and benzoic acid, etc. Gelatine boiled with caustic potash yields glycocine and leu- cine. Gelatine contains about 50 per cent, of carbon, 6.6 of hydrogen, and 18.4 of nitrogen; when pure it probably con- tains no sulphur. GELATIN PROCESS, the name given to the preparation of a photographic dry- plate by covering with an emulsion of sensitive salts in warm gelatin, and then drying. The plates are very much more sensitive than the old-fashioned wet plates, and have therefore made possible the photographing of rapidly moving ob- jects. The exact composition of the gela- tin emulsions varies considerably, and is kept secret by the different manufac- turers, but generally speaking, the chemicals used in their manufacture in- clude silver nitrate, ammonium bromide, potassium bromide and potassium iodide. GELNHAUSEN (geln'hou-zen), a town of Prussia, on the Kinzig river, and on the slopes of a vine-clad hill, 26 miles N. E. of Frankfort-on-the- Main. Here, on an island in the Kinzig, Frederick Barbarossa built an imperial residence ("the Pfalz") ; and in 1169 he conferred on the village the freedom of the empire. After being transferred to the counts of Hanau in 1435, Geln- hausen began to decay. GELSENKIRC HEN (gel'zen-ker- chen), a modern manufacturing town of Westphalia, 4 miles N. W. of Bochum. It owes to coal and iron its rise from a mere village since 1860. Pop. about 170,000. GEM, a precious stone. Gems are sometimes found crystallized in regular shapes and with a natural polish, more commonly of irregular shapes and with a rough coat. The term gem often de- notes more particularly a stone that is cut, polished, or engraved, and it also includes pearls and various artificial productions. The first and most valuable class of gems includes diamonds, emer aids, rubies, sapphires, and a few others; the second class includes the amethyst, topaz, garnet, etc.; while agate, lapis-lazuli, cornelian, etc., though much used for ornament, can scarcely be called gems. The fabrication of arti- ficial gems is now prosecuted with skill and capital, and has become an impor- tant industrial art. One class called semi-stones or doublets, are made by affixing thin slices of real gems to an under part of the strass by means of invisible cement. In some cases an imi- tation is made by setting uncolored strass or quartz in jewelry vdth some colored "foil" at the back of it. Attempts have been made with a fair measure of success to manufacture true gems by artificial processes. In 1858 MM. De- ville and Caron communicated to the
