588 



CUM ARABIC GUNNERY. 



less mixed, in the gum which exudes from the plum, 

 cherry, and other fruit-trees, as also in the mucilage 

 of flaxseed, slippery elm, &c. A'arious resins and 

 gum-resins arc commonly confounded under this ap- 

 pellation. 



GUM ARABIC is the product of the mimosa 

 Nitotica and some other species of the same genus, 

 inhabiting the sandy parts of Arabia, Egypt, Senegal 

 and Central Africa. It exudes spontaneously, in a 

 fluid state, and remains attached to the branches after 

 it lias concreted and become solid. This exudation 

 takes place continually, during the whole of the dry 

 season, from October to June, but more copiously 

 immediately after the rains. December and March 

 are the two months in which this gum is collected by 

 the Arabs, with whom it is an important aliment, 

 those tribes that are continually wandering in the 

 desert often making it their principal article of food 

 during a great part of the year. Gum Arabic is ob- 

 tained in rounded masses, transparent, or of a light 

 yellow colour, capable of being easily reduced to a 

 powder, insipid to the taste, or possessing a slight 

 acidity, which, however, is only perceptible by those 

 who use it habitually. It is easily soluble in water, 

 and the solution has the property of conveying pul- 

 verized solids through a filter, which would separate 

 them were they suspended merely in water : thus it 

 is impossible, by this means, to separate powdered 

 charcoal from gum water. In pharmacy, gum Ara- 

 bic is employed to suspend in water, substances 

 which, otherwise, could not be kept equally diffused, 

 as balsams, fixed oils, resins, &c.; but its principal 

 consumption is in manufactures, forming the basis of 

 crayons and cakes of water-colours, as well as of 

 writing-ink, and several liquid colours, serving to 

 increase the consistency of these colours, and to pre- 

 vent their spreading in calico printing, affording a 

 clear cement for joining light substances which may 

 be prepared in a moment, giving a lustre to ribands, 

 silks. &c., which, however, is destroyed by the appli- 

 cation of water. It is, besides, used for a great 

 variety of purposes. In medicine, it is frequently 

 employed, especially in dysenteries, as a demulcent, 

 and enters into the composition of a variety of emol- 

 lient preparations. Gum Senegal does not differ in 

 its sensible properties ; indeed, the chief part of the 

 gum Arabic of commerce is brought from Senegal, 

 and constitutes the most important article of trade 

 with that country. 



GUM RESINS apparently combine the properties 

 of gums and resins, being partly soluble in water, 

 partly in alcohol ; but they are evidently compound 

 substances, formed of two or more vegetable princi- 

 ples, which, indeed, are often in a state of mere me- 

 chanical mixture. Aloes, ammoniac, assafoetida, 

 galbanum, gamboge, olibanum, scammony, and a 

 great variety of concrete juices, are referred to this 

 head. 



GUN ; a fire-arm, or weapon of offence, which 

 forcibly discharges a ball, shot, or other offensive 

 matter, through a cylindrical barrel, by means of 

 gunpowder. 



Gun is a general name, under which are included 

 divers, or even most species of fire-arms. They may 

 l>e divided into great and small. Great guns, called, 

 also, by the general name cannons, make what we 

 also call ordnance, or artillery, under which come the 

 several sorts of cannon. (See Cannon, Artillery, &c.) 

 Great guns, of all sorts, cannons, carronades, &c., 

 whether of iron or brass, are cast in sand, and after- 

 wards bored. Small guns, muskets, fowling-pieces, 

 &c., are forged from bars of malleable iron, hammer- 

 ed to a proper width, and then turned over a mandril, 

 v cylindrical rod, so as to form a tube with a bore 

 smaller than that of the intended piece. The edges 



overlap alwut luilf an inch, and are firmly welded to- 

 gether. The tube is then hammered, in semicircular 

 grooves, on an anvil hollowed for the purpose. It is 

 afterwards bored with several instruments, of differ- 

 ent sizes, in succession, till the hollow is sufficiently 

 large and smooth. A strong plug is firmly screwed 

 into the breech, so as to make it perfectly close. The 

 projecting parts of the barrel, the sight, the loops 

 which fasten it to the stock, &c., are soldered on. 



In plate XLII, fig. 8, we have given a section of a 

 cannon in order to point out the principal parts into 

 which it is divided by gunners, C B is the length of 

 the gun, C D the first reinforce, D E the second re- 

 inforce, E F the chase, and F B the muzzle, A C the 

 caseable, K, G, S, D, E, F, B, the bore, and C B 

 the axis of the piece. K, the bottom of the bore, 

 and the space between C and K the vent field, the 

 vent being at K, one of the trunnions is shown at H, 

 the opposite one being cut away. The breech is seen 

 at C, and M is called the button of the breech. The 

 angle formed by the axis of the bore and a line ap- 

 plied to the side of the gun, is called the angle of dis- 

 part. 



Cannon are most commonly made of brass or iron. 

 The size of a cannon is reckoned by the diameter of 

 its bore, estimated by the weight of a cast iron ball 

 that will fit it. Thus, a six pounder is a cannon whose 

 bore is fitted to discharge a six pound cast iron bullet. 

 The diameter of a six pound bullet being 3-335 

 inches, an increase of one tenth is allowed for the 

 width of the bore, wherefore the calibre will be 

 3 '668 inches. The general dimensions of a cannon 

 are taken from the length which is supposed to be 

 divided into eighteen equal parts, as shown in the 

 line XY, in the figure ; but the unit of measure for 

 the more minute portions is taken from the diameter 

 of the calibre, which is supposed to be divided into 

 sixteen equal parts. Considerable diversity exists in 

 the proportions of cannon even in the British service. 

 Large guns are not now so much used as formerly, 

 but even as late as the seventeenth century, guns of 

 extraordinary size were in use. The largest gun 

 now existing, is one at Beijapoor : it is about four- 

 teen feet in length, and would require a bullet of 

 2600 Ibs. ; but is supposed to be intended for stone 

 balls. At Dover, there is a sixty pounder, called 

 Queen Anne's pocket pistol, and in Edinburgh 

 castle, an eighty pounder, called Mons Meg. 



Fig. 9, is a view of a cannon mounted on a carri- 

 age; fig. 10, shows the interior of a bomb; fig. 11, a 

 view of grape shot ; and fig. 12, a mortar mounted 

 on its carriage. 



GUNNERY signifies the science of using artillery 

 against an enemy judiciously, and to the greatest 

 effect. Besides an accurate acquaintance with the 

 management of ordnance of all kinds, the range and 

 force of every kind, the charge and direction neces- 

 sary for different distances, their materials, the man- 

 ner of making and of preserving them, with the 

 component parts, the kinds, the fabrication, the effect 

 of gunpowder, and the method of preserving it, with 

 the manner of preparing and managing every thing 

 that appertains to ammunition, the artillerist must 

 be able to instruct his men in their exercises, both 

 on horseback and on foot ; he must be well acquainted 

 with the management of the horses, that are used to 

 transport the cannon, and to mount the flying artil- 

 lery ; must know how to harness them to the can- 

 non ; how to move and manoeuvre with them on 

 ground of every kind; how to repair, at the mo- 

 ment, any sudden damage ; and must be thoroughly 

 acquainted with tactics, especially with the peculiari- 

 ties of the ground, and with the art of availing him- 

 self of them most judiciously in the disposition of his 

 artillery. He nnist, finally, be able to attack or 



