Besides the true gums, there are the

GUM-RESINS, which are much more mixed in their chemical constituents; in general terms, however, they may be said to consist of certain resins soluble in alcohol, and of the true gum, so that it requires both water and alcohol to dissolve them entirely. They are chiefly used in medicine and perfumery, and may be said to form a connecting link between the true gums and the true resins, commercially speaking. The principal

are:

1. Gum asafætida. See ASAFOETIDA. 2. Gum benzoin or benjamin. See BENZOIN. 3. Gum styrax or storax is another sweet-scented gum-resin, produced by styraz officinalis in Turkey in Asia. It is usually liquid, of the consistence of treacle, and a blackish or dark-gray color. It is also used in perfumery. 4. Gum sagapenum, another medicinal gum with unpleasant garlic-like odor, dark-brown color, and a soft consistency. It is not known what plant produces it, but it is generally supposed to be obtained from a ferula. 5. Gum galbanum. See GALBANUM. 6. Gum opopanax is vielded by the roots of another umbelliferous plant, opopanax chironium. It comes from the Levant in reddish-yellow lumps of a disagreeable smell. Its only use is in medicine. chiefly for plasters. 7. Gum ammoniacum. See AMMONIACUM. 8. Gum myrrh is a very sweet-smelling gum resin, which exudes from the stems of an Abyssinian shrub, the balsamodendron myrrha. Two distinct kinds are known in commerce, the Turkish and the East Indian; the former is the better. They are both in irregular-shaped small lumps, rarely exceeding the size of a walnut, of a reddish-brown color, rather lighter in the Turkish sort. Considerable quantities are used in medicine, and in perfumery for dentifrices, washes for the teeth, etc., in consequence of its being supposed to possess considerable antiseptic properties, and for the agreeable odor it imparts to the breath. From 15 to 20 tons are imported annually. 9. Gum scammony.-This is obtained from incisions made purposely in the crown of the great tap-root of the convolvulus scammonia, which is bored for the purpose. It is of a dark sap-green color, inclining to greenishgray, in large and small cakes, and in irregular fragments. Its use is extensive as a mild and safe purgative for children, but scarcely any drug has been so uncertain in its operation, owing to the excessive adulteration practiced upon it by the Turks previous to its shipment. This has now been obviated by importing the root itself, and extractng the gum in this country.

There are many other gums known, but these are the ones to be had in shops, and for which uses are found in the arts, manufactures, and in medicine. Many also of the true resins, as copal animi, etc., are called gums, but they are strictly resins. RESINS.

See

Gum-substitutes are manufactured from wheat-starch, farina or potato starch, sagoflour, and other feculas, by baking or roasting, so as to convert the starch into dextrine (q.v.). This is now an important manufacture, in which a large amount of capital is engaged. They are made on a very extensive scale by the Messrs. Laing of Manchester and others, and are largely employed in dressing calicoes and other fabrics, also as a substitute for the more expensive gums in gumming paper, as in the case of postage and receipt stamps, which are made adhesive by dextrine. For this and some other purposes, the gum substitutes are superior to the real gums, as they are easily dissolved, and can be spread more equally over a smooth surface. Very large quantities of the starch of potatoes, called farina or potato-flour, are made in Great Britain, and are also imported from the continent to be used in this manufacture.

GUMBIN NEN, a thriving t. of Prussia, in the province of Prussia, is situated on both banks of the Pissa, one of the affluents of the Pregel, 68 m. e.s.e. of Königsberg. It was first regularly laid out in 1724, and owes its rise and prosperity in great measure to the settlement here of many Protestants, chiefly from Salzburg, who were driven from their homes by religious persecution. Among other institutions, the town has a gymnasium, a public library, churches, and hospitals. Woolen-cloth weaving, ironfounding, brewing, and the making of machinery are the branches of manufacture. Pop. '90, 12,207.

GUMBO, a kind of soup, prepared from okra, and much in vogue in the southern states. It is made in various ways, sometimes containing considerable animal flesh, the most favorite being chicken. Gumbo soup proper, however, is composed principally of okra with portions of other vegetables added according to the taste, as rice or pearlbarley. The name is thought by some to have originated with the slaves, but that is

doubtful. See HIBISCUS.

GUM-BOIL, an abscess (q.v.) near the root of a tooth, and discharging itself towards the mucous membrane of the gum; usually superficial, but sometimes more deeply seated in connection with the bone, and causing considerable deformity, with risk of caries (q.v.) or necrosis (q.v.). Gum-boil should be treated, in the first instance, by

simple protection against cold and external injury; but as soon as the presence of matter can be ascertained, it is usually good practice to give vent to it by a pretty free

incision.

Gun-Cotton.

GUM'MEL, a t. of Africa, in the state of Bornu, in lat. 12° 38′ n., and long. 9° 21' e. In 1851, on the occasion of Dr. Barth's first visit to Gummel, he found it a flourishing town, the great entrepôt for the natron trade, with a weekly market, at which were 300 stalls, offering for sale all sorts of clothing, tools, pottery, victuals, cattle, horses, etc., but in 1854, on visiting it on his return journey, he found that during the interval it had suffered severely from civil wars, and was then in a state of at least temporary decay. Its population in 1895 was placed at over 10,000.

GUMMING, a disease analogous to canker (q v.), and like it, very destructive to fruit trees, but confined to those the sap of which readily produces much gum; as the cherry, plum, peach, apricot, and almond. It is supposed sometimes to originate in wounds, in which a morbid exudation of gum takes place; but it appears to be more frequently occasioned by severe frosts, and to be very much dependent upon causes which induce a general unhealthiness. It very generally terminates in the destruction, not merely of the branch in which it originated, but of the whole tree, although trees in which it is in sure progress sometimes live for years, and meanwhile produce large crops of fruit. A small fungus (næmaspora crocea), which has been supposed to be the cause of gumming, more probably appears in consequence of it.

GUMRI, an old t. of Russian Armenia, on the site of which the important city and fortress of Alexandrapol-pop. '92, 26,086-have been built. The site is on the highroad to Erivan, and is 60 m. n.w. of that town. Alexandropol is built at an elevation of 5,860 ft. above sea-level, and here the cold is so intense that men are often frozen to death in the fields.

GUM'TI, a river of India, remarkable, as its name is meant to express, for its windings, rises in a small lake in lat. 28° 35′ n., and long. 80° 10' e., and after a south. eastern course of 482 m., enters the Ganges from the left in lat. 25° 29′ n., and long. 83° 15' east. It is navigable for inland craft as far up as Lucknow, which is fully more than 300 m. above its confluence with the Ganges.

GUM TREE. See EUCALYPTUS and TUPELO.

GUN, a term applied in its most general application to firearms of any description, but in the more restricted and technical sense to cannon. A gun is a frustum of a right cone, with a cylinder excavated round the axis, to serve as a bore. Close home to the end of this cylinder, the powder is driven, and outside it is the ball to be expelled.

The trunnions are cast in one mass with the piece, and are placed in the second reinforce in such a position that the breech-end of the gun outweighs the muzzle. Their axis is generally about half their diameter below the axis of the piece. This locality has several conveniences; but for the maximum of steadiness in the recoil, it has been shown that the axes of the trunnions and of the gun should exactly intersect. The use of the trunnions is to suspend the cannon on its carriage in such a manner that it may be readily depressed or elevated, but so that it shall have no horizontal motion which is not shared by the whole carriage.

The vent or touch-hole, the channel through which the charge is fired, is a small cylindrical orifice leading at an angle from the breech of the bore towards the base ring. The explosion within reacts with great force on the lower portion of the vent, and in case of rapid or long continued firing, soon honeycombs the iron or brass, often dislodging considerable fragments. This, besides diminishing the regularity of the action of the powder on the projectile, would involve danger of bursting if permitted to any great extent. The gun so affected is therefore bouched, that is, has a new vent constructed. The process consists of drilling a female screw, of larger than the required diameter, in the metal of the gun. Into this matrix, a bar of pure copper is screwed (copper being the metal least liable to fuse under the intense heat of ignited gunpowder), and the vent is then drilled through the copper. Sir A. Dickson devised a plan of ramming a cartridge of sand firmly into the breech, then filling the vent and all interstices with molten copper, and boring a hole through the latter. This simple procedure may be shortened by inserting the stem of a tobacco-pipe during the filling; the pipe, when removed, leaving a perfect vent.

With reference to the manufacture of guns in general, their specific and distinctive features, their inventors and manufacturers, their use and appliances, explosives, projectiles, etc., the reader is referred to the following articles: ARMSTRONG, LORD W. G.; ARTILLERY; ARTILLERY, PARK OF; ARTILLERY, SCHOOL OF; BAR-SHOT; BREECHLOADING ARMS; BRITISH NAVY; CALIBRE; CARRONADE; CARTOUCH; CARTRIDGE; CASE-SHOT; COEHORN; DAHLGREN GUN; DYNAMITE ; DYNAMITE CRUISER; DYNA MITE GUN; EXPLOSIVES; EXPLOSIVES OF HIGH POWER; FIREARMS; FIRE-BALLS; FORTIFICATION; GATLING GUN; GRAPE-SHOT; GRUSON SHIELDED MOUNTINGS; GUNBOAT; GUN-CARRIAGE; GUN COTTON; GUN-FACTORIES; GUN-MAKING; GUNNERY : GUNPOWDER; HOTCHKISS; Krupp, Alfred; LIMBER; MACHINE GUNS; MITRAILLEUSE; MORTAR; NAVIES, MODERN; ORDNANCE; ORDNANCE FABRICATION; PALLISER, SIR WILLIAM; PARROTT, R. P.; PROJECTILES; RAPID-FIRE GUNS; RICOCHET; RIFLED ARMS; RODMAN; SHELL-GUNS; SHELLS; TACTICS; TRAVERSING PLATFORM. GUN-BOAT, a small vessel usually of light draught, armed with one or more guns of heavy calibre. Its use is to run in closer to the shore or up rivers, where larger men-ofwar cannot go. Early in this century it was an extremely popular type of vessel with this government, and over 250 of them were built. The "gun-boat" system was soon

GUNS.-I. Gun with match-lock. 2. Rotary-lock. 3. Flint-lock. 4. French hunter's gun. of same; 9. Cartridge of same. 10. Prussian ovate-ball cartridge. II. Lefaucheux rifle. 16. Its cartridge. 17. Section of latter. 18. Austrian gun, Wänsel's pattern. gun. 24. Spencer's repeating carbine. 25. Section thereof, and 26, cartridge. 31. Lefaucheux revolver. 32. Lefaucheux cartridge. 33. Russian Minié-gun. wooden plug. 37. French expanding ball, ancient form. 38. Recent form of the s peripheral fire. 41. Baden expanding projectile. 42. Ploennis' expanding projectile.

27. H 34.

1.

5. Cossack gun. 6. Russian infantry gun. 7. Prussian needle gun; 8. Section of lock gun, with shot cartridge. 13. Thouvenin gun. 14. Chassepot rifle. 15. English Enfield 19. Remington rifle. 20. Peabody gun. 21. Cartridge, and 22, ball thereof. 23. Pfyffer Henry's repeater. 28. Prussian needle carbine. 29. American carbine. 30. Colt's revolver. Bavarian case-cartridge. 35. Bavarian expanding ball. 36. English expanding ball, with 39. Swiss crdnance cartridge, with ccmpressed powder. 40. Box cartridge, with e. 43. Lorenz's compressed projectile. 44. Old pointed projectile.

same.