coloured gelatinous material a mixture of wood charcoal and animal charcoal, leaving the whole together for some hours,
then redissolving and straining off the clarified gelatin.
Isinglass.—Isinglass or fish glue, in its raw state, is the swimming-bladder or sound of various species of fish. The sounds undergo no other preparation than careful dry- ing, but in the drying they are variously treated and made up, so that the isinglass comes into commerce under the names of “leaf,” “staple,” “book,” “pipe,” “lump,” “honey- comb,” and other designations, according to its form. The finest isiuglass, which comes from Russia, is prepared by cutting open the sounds, steeping them in water till the outer membrane separates from the inner, then washing the latter and exposing it to dry in the air. Russian isinglass is obtained from several species of sturgeon (A cipenser), found in the Volga and other tributaries of the Caspian Sea, in the Black Sea, and in the Arctic Ocean. Brazilian isinglass, obtained from Brazil and Guiana, is the produce of a large fish, Silurus parherii, and probably some other species; and Manila and East Indian isinglass are yielded by species of fish not yet satisfactorily determined. The sounds of the common cod, the bake, and other Gatlidce are also used as a kind of isinglass. The principal uses to which isinglass is applied are for jellies and confections, and as a clarifying or filtering medium for wine, beer, and other liquids. When used for culinary and confectionery purposes, isinglass is rolled into thin sheets and cut into fine shreds to facilitate its solution. For clarifying liquids its fibrous structure is of great value, as it forms a fine network in the liquid in which it is disseminated, and thereby mechanically carries down all the minute particles which render the liquid thick and turbid. Isinglass dissolved in strong acetic acid forms a powerful cement, much used for repairing glass, pottery, and similar small objects.
Uses of Gelatin.—The gelatin derivable from bones enters very largely into human food, in the stock for soups, &c., and as prepared gelatin, “ calves foot jelly,” and isin- glass. In addition to the uses already alluded to, gelatin has many other applications in the arts. It is employed as a sizing agent in paper-making, and by painters it is also used for sizing or priming, and for preparing tempera colours. Further, it is used in the preparation of elastic moulds of undercut work, and in the manufacture of inking rollers for printing. Gelatin treated with bichromate of potash, under the influence of light, undergoes a remarkable chemical and physical change, whereby it is rendered en- tirely inabsorbent of and insoluble by water. The change is due to the'oxidizing effect of the bichromate ; and the circumstance has given rise to the numerous so-callcd carbon-processes introduced into photography by Swan, Johnson, lVoodbury, Albert, Edwards, and others, in all of which an image is produced in gelatin oxidized by chromium compounds. An insoluble glue may be prepared by adding to dissolved glue, just before using, a proportion of a solu- tion of bichromate of potash, and such a preparation forms a useful waterproofing medium. Glue may be kept liquid at ordinary temperatures by the addition of concentrated acetic acid or of weak nitric acid. Dumoulin’s liquid glue, which possesses powerful adhesive properties, is composed of glue in the proportion of 2 lb dissolved in 1 quart of water with 7 oz. of nitric acid (sp. gr. 1335) added. Month or lip glue is prepared by adding £511) or thereby of sugar to each pound of dissolved glue. It forms solid but easily dissolved cakes, and as it can be sufficiently softened by the tongue, it is for many purposes extremely convenient. Transparent gelatin, brightly coloured by dyeing substances, and cast in excessively thin sheets, is largely used for ornamental wrappings for bon-bons, &c.
Various adhesive but non-gelatinous substances are, on account of their Dronerties. known connnerciallv s glue. nd are used as substitutes for ordinary glue. Thus marine glue, employed in shipbuilding and for other purposes, is a compound of iudia-rubber and shell-lac dissolved in coal-tar naphtha. Glue substitutes are also prepared from the albuniinoids casein and gluten, but they are not likely to become substances of any considerable connncrcial importance.
GELDERLAND, Geldern. See Guelderland, Guelders.
GELÉE, Claude. See Claude of Lorraine.
GELL, Sir William (1777–1836), classical scholar and antiquarian, was born at Ilopton in Derbyshire in 1777. After the usual preliminary education, he entered Emmanuel College, Cambridge, taking his BA. degree in 1798, and afterwards becoming a fellow. About the be— ginning of the century he was sent on a diplomatic mission to Greece ; and on his return in 1803 he was knighted. In the following year he published his Topography of Troy and its l'icinity, illustrated and explained by (I)'(t?('i72{/s and descriptions. His Geography and Antiquities of I than: was published in 1807. In 1810 appeared The Itinerary of Greece, with a Commentary on Pausanius and Stra/m, aml an account of monuments of antiquit y existin g in that country. This was followed in 1816 by the Itinerary of the JIorm, being a description of the routes of that. peninsula, a new edition of which was published in 1823, under the title of Il'arrative of a Journey in the ilforea. His best known work is I’ompeiuna, or Observations on the Topography, I'Iclifices, and Ornaments of Pompeii, in which he was assisted by Mr J. I’. Gaudy. The first part of this was published in 1817—19, and was translated into French in 18:28; the second part appeared in 1830—31. It was followed in 1834 by the Topography (3f Rome and its Vicinity. In Italy, whither he had retired on account of his health, he became acquainted with Queen Caroline, and his noble and disinterested behaviour during her trial ex- hibits his moral character in a very favourable light. The queen showed her sense of his co—operation in her defence by appointing him one of her chamberlains in 1820. He died at Naples in 1836. His drawings, representing a very large series of views of classical ruins and localities, and executed, if not with much artistic skill, yet with great detail and exactness, are now in the print room of the British Museum.
