GUM 



GUM 



tise on the nature of rivers was published 

 at Bologna in 1756, with the notes of Man- 

 fredi ; and the whole of his works were 

 printed in a collective form at Geneva, in 

 1719, in two volumes quarto. 



GUIAC. See RF.SUT. 



GUIDE, in music, the name given to 

 that note in a fugue, which leads ofi'and 

 announces the subject. 



GUILAND1NA, in botany, boruhtc or 

 nicker tree, a genus of the Decandria Mo- 

 nogynia class and order. Natural order 

 of Lomentacese. Leguminosx, Jussieu. 

 Essential character : calyx one-leafed ; 

 salver-shaped ; petals inserted into the 

 neck of the calyx, nearly equal ; seed ves- 

 sel a legume. There are six species. 



GUILD, or GILD, a fraternity or com- 

 pany. As to the original of these guilds, 

 or companies, it was a law among the 

 Saxons, that every free man of fourteen 

 years of age should find sureties to keep 

 the peace, or be committed ; upon which 

 the neighbours entered into an associa- 

 tion, and became bound for each other, 

 either to produce him who committed 

 any offence, or to make satisfaction to the 

 injured party : in order to which they 

 raised a sum among themselves, which 

 they put into a common stock; out 

 of which they, upon occasion, made a 

 pecuniary compensation, according to 

 the quality of the offence committed. 

 These gilds are now companies, join- 

 ed together with laws and orders made 

 by themselves, by the licence of the 

 prince. 



GUITAR. See MUSICAL instruments. 



GULES, in heraldry, signifies the co- 

 lour red, which is expressed in engraving 

 by perpendicular lines falling from the top 

 of the escutcheon to the bottom. 



GUM, a thick transparent tasteless 

 fluid, which exudes occasionally from 

 certain species of trees. It is adhesive, 

 and gradually hardens without losing its 

 transparency. Gum is chiefly obtained 

 from different species of the mimosa, par- 

 ticularly from M. nilotica,a native of Egypt 

 and Arabia, which is known by the name of 

 gum arabic. The specific gravity of gum 

 is about 1.4. It is not changed by expo- 

 sure to the air, but is deprived of its co- 

 lour by the action of the sun. By heat it 

 becomes soft, and is speedily reduced to 

 the state of charcoal, which enters large- 

 ly into its composition. The constituent 

 parts of gum are, carbon, hydrogen, and 

 oxygen, with smaller proportions of ni- 

 trogen and lime. The oxygen Is much 

 less in quantity than the saccharine mat- 

 ter. See SCTGAJR, The existence of lime 



and nitrogen in gum renders it essentially 

 different from fecula and sugar, to which, 

 in other respects, it bears a near relation; 

 they, however, are able to undergo the 

 vinous fermentation, which is not the case 

 with gum. Gum readily dissolves in wa- 

 ter, and the solution, which is thick and 

 adhesive, is known by the name of muci- 

 lage. It is soluble also in the vegetable 

 acids. Sulphuric acid decomposes it, 

 and converts it into water, acetic acid, 

 and charcoal. With the assistance of 

 heat, muriatic acid, and nitric acid, pro- 

 duce a similar effect. It is insoluble in 

 alcohol and ether. Such are the chief 

 properties of gum arabic. There are, 

 besides |this, other gums, of which the 

 principal is denominated tragacanth, from 

 the astragalus tragacantha, a native of the 

 island of Crete, which is in the form of 

 vermicular masses ; it is less transparent 

 arid more adhesive than gum arabic, but 

 by distillation it yields similar products. 

 In our gardens and orchards we find, in 

 good quantities, gum exuding from the 

 cherry and plumb trees, which differs 

 chiefly from gum arabic in being softer 

 and more soluble. Gum, in a state of 

 mucilage, exists in a number of plants, 

 especially in the roots and leaves. It is 

 most abundant in bulbous roots, and of 

 these the hyacinth seems to contain the 

 largest quantity. A pound of the bulbs 

 of this root, when dried, yields four 

 ounces of a powder, which, when mace- 

 rated in water, give a mucilage that acts 

 well as a mordant for fixing the colours 

 in calico-printing. Gum is used in medi- 

 cine, and is considered as a specific a- 

 gainst the strangury occasioned by blis- 

 ters; it constitutes, under particular forms, 

 a nutritious food, and it is well known as 

 an important article in the manufacture 

 of our ink. 



GUM resins, are certain substances that 

 have long been used in medicine. They 

 are all solid, generally brittle and opaque, 

 have a strong smell, and a pungent and 

 bitter taste. They consist chiefly of gum 

 and resin, the - proportions varying with 

 the particular substance. They are never 

 obtained by means of spontaneous exu- 

 dation, but are procured by wounding 

 the ^plants which contain them. The 

 principal of the gum-resins are, 1. AMMO- 

 xi AC, which see. 2. Asstifbetida, obtained 

 from the ferula assafoetida, a plant found 

 in Persia. The gum resin is extracted 

 from the roots by cutting off the extre- 

 mities ; a milky juice flows out, which is 

 dried in the sun. It is brought to Eu- 

 rope in masses ; its smell is very foetid, 



