James Orr.

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color, Inclining to greenish-gray, in large and small cakes, and in irregular frag-
ments. Its use is extensive as a mild and safe purgative for children, bnt scarcehr
any drag has been so uncertain in its operation, owing to the excessive adnh
teratiou practised npon it by the Tarks provions to its shipment This has
now been obviated by importing the root itself, and extracting the gum in this
country.

There are many other gams well known, but these are the ones to be had In
shops, and for which nses are found In the arts, manufactnree, and in medicine.
Many also of the true resins, as copal aulmV <fce., are called gums, but they are
strictly rwins. See KBsnrs.

Oum-mihlUuteB are manufactured from wheat-starch, farina or potato-starch,
sago-flour, and other feculas by baking or roasting, so as to convert the starch Into
Dextrine (q. v.). This now an important mannfacture, in which a large amount of
capital is engaged. They are made on a very extensive scale by the Messrs. Latng
of Manchester and others, and are largely employed in dressing calicoes and other
fabrics, also as a substitute for the more expensive gams In euraming 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 farma or potato-flour, are
made In this country, and are also Imported from the continent to be used iu this
manufacture.

GUMBI'NNBN, a thriving town of Prussia, in the province of Prussia, is situ-
ated on both banks of the PiH:jia, one of the affluents of the Pregel, 68 miles east-
south-east of KOnigsberg. It was first regularly laid out hi ITftC and owes its rise
and prosperity iu great measure to the seftleniont here of many Protestants, chiefly
from Salzburg, who were driven from their homes by religious persecntion. Among
other institutions, the town has a gymnasium, a public library, three Protestant
churches, and three hospitals. Wooleu-cloth weaving, brewing and distilling, ace the
branches of manufacture. Pop. (1975) 9116.

GUM-BOIL, an Abscess <q. v.) near the root of a tooth, and dtaoharging itself
towards the mucous membrane of the gum ; usually soperfloial, but sometimes
more deeply seated In connection with the 1>one, and eansine considerable de-
formity, wiiii risk of Caries (q. v.) or Necrosis (q. v.). Oum-bolT 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 aaoally good practice to give
▼out to it by a pretty f nee incision.

GUM TREE. See EucALYFTiri and Tupblo.

GU'MMEL, a town of Africa, in the state of Bomu, in lat W* 38' n., and long.
9^%V c Iu 1851, on tlie occasion of Dr Barih's first visit to G., he found it a flomv
ishing town, the great entrcpOt for the natron-trade, with a weekly market, at which
were 800 stalls, offering for sale all sorts of clothing, tools, pottery, victiuls, cattle,
horses, &., and with a pop. of 10,000 ; but in IS&i, on visitlnflr it ou his return jour-
ney, he found that, during the interval, it had suffered severely from civil wars, and
was then In a state of at least temporary decoy.

GUMMING, a disease anatogons to Canker (q. v.), and like It, vei^^ destructive to
fruit-trees, but confined to those the sap of which readily produces much gum : as
the cherry, plmn, peach, apricot, and almond. It is supposed sometimes to origin-
ate iu wounds, In which a morbid exudation of gum tjikes place ; but it appears to
be more frequently occasioned by severe frosts, and to be very much depeodebt



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npon canpeft which todnce a peneral nnhealthineBB. It rery generally terminates in
the tlcHtmctiou, not merely of the brunch In which it oriiiliuitej, but of the wholo
tree, jUiMough trees in wbUh it is in fnre progress sometimet* live for yearp, aud
meauwhilc produce larcc crops of fruit. A fmall fiiugiis iSa-moMpora eroeea),
which ha^been sappoaeu to be the cauae of gummlug, more piooubly appears in con-
feeqaeoce of it,

GU'MRIf an old town of RasBiaii Armenia, aii the site of which the important
city and fortress of Alexaodraiwl— pop. (IH67) 17^78— have been built. Tlie site is
on ifati high road to Krivan, nud is fiO milet) north-west of tliat town. Alexandrapol
t» built at au elevation of 68(0 feet above sea-level, aud here the cold ia so intense
Uiat men are often troxen lo death in ttie fields.

GU'MTI, a river of Indfn. remarkable, as its name is meant to express, for ita
windings, rises in a small lake in lat, SS® 3ft' n., and lonp. 80« 10' e., and after a
south-eastern coarse of 488 miles, enters the Ganges from the left in lat. SI6° W n.,
aud k>o^. 83** 15' o. It is navigable for inland craft as far np as Lacknow. which is
folly more than 800 miles above its confluence with the Gang^. At Jaoupore,
about 56 miles from the Gauges, it is spauned by abridge of 16 arches.

GUN, a term applied in Its most general application to firearms of any descrip-
tion, bnt in the more restricted and technical sense to Cannon (q. v.). A gun is a
ftnstnm of a riglit cone, with a cylinder excavated ronnd the axl?, to serve as a
bore. Close home to the end of this cylinder, ihc powder is driven, aud outside it
is the ball to be exiwlled.

The trunnions are cast in one mass with the piece, and are placed in the second
reinforce in snch a nosltlon tliat the breech-end of the gun outweighs the muzzle.
Their axis is generally alwnt half their diameter below ttje axis of the piece, Tliis
locality has several conveniences ; but for the maxinnim of steadiness in the recoil,
it has been shewn that the axes of the trunnions and ot the gun should exnctiv
intersect. The use of the trunnions is to suspend the cannon on its carriajre in puch
a manner that it mav 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 tonch-hole, the cbannel through which the charge is fired, is a small
cylindrical orifice leading at an angle from the breech of the bore towards the base
nng. 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
bmss, often dislodging consideraole fragments. This, besides dimlninhlng the regu-
larity of the ftclion of the powder on the projectile, would Involve danger of bursting
if permitted to any great extent. The gun po effected is therefore bonche^, that is,
baa a new vent constructed. The process consists of drilling a female screw, of lar-
ger tbaii the required diameter, in the metal of the gun. Into this matrix, a bar of
pore coi»per is screwed (copper t)eing the metal least liable to fuse under the intense
neat of ignited gnnpowder). and the vent is then drilled through the copper. Sir A.
Dickson devised the following simple mode: he rammed a cartridge of sand firmly
into the breech, then filled the vent and all the Interstices wltli molten copper, and
bad only to bore a hole through the latter to complete the operation. In cases of
great urgency, even this timple procedure may bo shortened by the insertion of the
f4em of % tobacco-pipe during the Aliiuy ; the pipe, wlien removed, leaves a perfect
Vent.

With reference to Rifled Cannon, some particulars have already l>een given under
AnxsTBOKo GirK^ and fuller details will be given under Kifleb Abus. Under the
beading Caitkon will be fomid some details as to various kinds of heavy guns, as well
cs under the several headings Lamcastbb Gun, Mortar, Susll-qun, &c. The his-
tory of guns aod gunpowder is sketched in the article I^'ibb-aiiiis. Th(> various kinds
fA small-nrms are discussed under their respective heads, as An()UEBUs, Match-
lock, PisToi^ Rbvolter, Kix*U50 Arms.

GUN-BOAT, A small host or vessel armed with one or more guns of heavy
calibre, Fro»n its small dimensions, it is capable of running close Inshore or up
rivers, and from the same cause it has little chance of being nit by a larger ves!*«fl
at the long range which the carrying |)Ower of its guns enables it lo maintain.
On the outbreak of the Russian war (1$54— 1866), as the British navy was without
a single guu-boat| a large squadron of them was hadlily constructed in 1855 mxi



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186#, but too late for that npecial war. From the baate with which thej were p«t
together, most of those reesols prored defectire. Tbefr tonna^ waa small ; and
their armament osaally consisted of oue S-inch gao and one lOO-ponoder Armatrong
gnu. In tho last two wars with China, gnu-boats performed excellent aerrlce. bar-
ing penetrated nearly to Pelclng, aud far op the Tanff-tse-kiang. Oun-boats in tbeir
more modern form are small maetless vessels monating one large gnn in the bow,
and propelled by an en^iue with aingle or twin screws. The gun is pointed )>y
Bieana of the helm or the sorewf, and the gm)>boat )e in fact a IkMUing gnn-car-
rfage. The StouncA, the drst gnn-boat bnfit on thla principle for our navy, has
giten her name to the whole class. In onr nary these gno-boata carry an armor-
pierelng gnn of 18 tons, on a dranght of only 4 feet. Bnt they haTe been designed
to carry even B6-ton gnus. Four nave hitely been bnilt by Messrs Armstrong for the
Chinese navy - the Alpha, Beta, Gamma, and Delta ; two of these carry a SS^n gnn,
and two a gun of over 30 tons. A small flotilla of snch gnn-boata, proteeted oonr by
their smalfsiae, wonld be in coast defence fdrmidabte opponents even for iroBcfada.
At the beginning of the centaiy the United Statee bad over 800 of ttieee vnaaela ; bol
the ** gnn-boat eyltom " waa soon abandoned. tSoma of the conttuaatal navleaara
well provided with gnn-boata.

OUN-CARRIAGE la a very important clement in tbe eqalpment of each piec0
of ordnance. It requires to be of great strength, and at the same time of oonaidera-
ble weight, in order that the whole apparatoa— gnn and carriage togethei^-may not
be driven backward by the recoil in firing. Fleld-gnn carriagea have, besideif to
bear an enormoos strain in passing at a rapid pace over broken, nneven, or rocky
ground. To provide for thia severe wear aud tear, every part Is fitted with the ntr-
moat precision, made of well-seasoned material, and on strict mechaoicalprinciples.
A large departmen twitted with splendid machinery, in tbe Royal Arsenal at v7oolwich,
called the Royal Carriage Department, ia charged with this branch ol manofactnre
for tbe BrlUsU service. Carriagea are of various kinda, according to the aervice for
which they may be required. When the field-gnu is to be movec^ the trail-plate la
hooked to the Limbxr (o. v.), which converta the gnn-carriage and limber into a
four-wheeled vehicle, capuble of conveying the gnu, fta tools and ammunition, and
aeveral of ita gnnuera. Informatioo relat^e to certain species of gun-carriagea wOl
likewise be found nnder Tbavkhsivo Plattobm. Amon^c modem inventions of
war is the If oncrlefl or elevating gun-carriage, in which the gnn Is poised at the end
of a lever pivoted on the carriage, and balanced by a heavy counter-weicht. Before
firing, the gun is raised by mecnanism ; when fired, ita own recoil dnves It down
upon tbe carriage. This arrangement enablea gun and gonnera to lie concealed be-
hmd a parapet until the moment of discharge.

GUN-COTTON, a detonating sobatanee invented by Schtobein in 19M, and
obtained in the following manner. One part of finely carded cotton le Immersed in
16 parte of a mixture of equal meaanrea of strong nitric add (sp. rr. 1*(Q and siil-
phurte acid (sp. gr. 1*846). The cotton mnat be completely immereedm tbe mixture,
otherwiae it becomea ao hot as to nndergo immediate decomposition. After a few
minutes* immersion, it must be pinngedlnto a large volume or cold water, and then
washed till the moist mass oeasea to ahew any adn reaction when plaoed on litmns
paper. It is then to be carefully dried at a temperatore not exceeding 170^.

Any anbetance oontainiBg oelhiloee, snch aa tow, linen, aaw-dnst, paper, Ac, may
be employed instead of cotton, and the change that takes place in the formation of
the explosive compound seems, from the researches of Hadow, to be aa follows : tbe
composition of cellulose ia represented by the formula C* %B.% oOy o* In the formatJon
of gnn-colton or pproctytin (derived from pyr* fire, and «yfoi>, wood), nine eqniva-
lents of the hydrogen are replaced by an equal number of eqnivalents of peroxide of
idtroflren (N04>, so that the formula for the new compound la O^ «Hf itN04,Oto*
The fibre, in undergoing thia change, increases about 70 per cent In weight, aud
acquires perfectly new propertiea. Although scurcely differing in appearance from
unchanged cotton, it may be distinguished from it by ita barshnesiL by the crepitat-
ing sound which it yields when pressed by the hand, by its having lost the property
of depolarisation which ordinary cotton posnesees, and by Its electric condition.
Iodine diasolved in a aolntion of iodide of potaasinm affords a cenaiu means of die*
tingniahingexploaive from ordinary cotton. If tide former hi moiatened with thla



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iodtDe tolntlon, and a Httle dllmte 8ali>harlc mold fs ini%«e<raeDtIy added (one part of
f he add to four of vrattT), a yellow color to evolved ; while orainarv cotton wool,
when alDilarly trented, asaaineo a blue color. Its moat remarknbly property la,
however, the facility with which it tukea flre, and ita rapid and coinplf te comboa-
tion. Tlie rennlts of Genera! vou Lenk'a improvemcut^ In the munnfacture of giiu-
cotton. which, however, did not lead to ita aaiMfraeding fi^npowder in atrv one
direction, are fdven in another place. The more recent experlmenta of Proieaaor
Al>el, which have been carried on for the laet ten yeara at the Woolwich Araeiial,
aud are still being contiuaed, have resnltfd In further 1«pit>v1ng the mannfactnro,
and alao In determiDing more accnrately the properties of gan-cotton. Abel'a pro-
cess coosleta In steeping cotton-waste in strong nitric und solpharic acids at a low
temperatnre, and afterwards washing It thoroughly. It Is next reduced to a pulp hi
a common rng-englne (see Papbb), and then fn the pulpy condition it ia washed
again In a large qunntity of water to remove every trace of free acid. After thoL
it Is pressed at a low power, and aubaeqoently In a powerful bydranlic press, out of
whlcn It comes in so wet a state aa to bo uninflammable. Gun-cotton can thus be
compressed into masses of any shape, ns cylinders or cubes, and of any re-

a aired density or hardness. It can also be converted into the fonn of paper, or
ito gnn-cotton grains for sporting purposes.
Gun-cotton can now be manufnctnrt*d so as to keep, there Is every reason to be-
lieve, with perfect safety in a wet state, and be as good aa ever when dried ngaiii.
The remits of some experiments carried on a year or two ago by a government com-
mittee at Chatham shewed that whou j^nn-ootton Is firmlv confine^ it exerts a de-



Btmctlve effect equal to aboat five timea that of gnnpowcfer.
Professor Abel has proved that the more thoroughly gm
the more perfectly can its action be controlled, and it ia now generally used in com-



pact disca for mining purposes; that it is sympathetic, so that, if gently ignited by
a spark, in the form of jraro, It smoulders slowly away ; if by a flame. It hums up
rapidly ; and if fired in the compressed atute by a detonating fuse. It explodes with
great violence, even when unconflned. The most recent and atrikiitg discovery re-
garding it, however, Is, that Although, aa a rule, non-inflammable and nou-exploelve
In the wet state, yet, whep flred in this condition with the detonating substance ful-
minate of mercury, anci a little dry gnn-cotton or gunpowder, it explodea with aa
uuKh violence aa when it is dry.

While gunpowder djjes not explode at a lower temperature than 600* P., gnn-
ootton has been known to do so at 877° F., and cannot be hetiti d to 400*> F, with-
out explosion. Gnu-cotton produces neither smoke nor fouling when fired, and
does not heat the gun so much as gunpowder, though, by the rapidity of ita explo-
rion, it strains the barrel more.

GUN-COTTON. During the last few years, groat Improvements hove lieen
effected In the mannfactnro und application of this material, and in consequence, its
use is rapidly extending, especially In Great Britain, where it is found of great ad-
vantage in mining operations, owing to Its not producing smoke when exploded.
For the Improvements as well as the invention of gnn-cotton, we are chiefly indebted
to the Anstrlans, the most important Improvement being that of Baron Lenlc, cou-
nting chieflv in the following precautious In the manufacture : 1. A perfect clean-
sing and drying of the cotton. %. The nee of the most concentrated and purest odds
procurable commercially. 8. Steeping the cotton a second time In a mixture of
the strong acids. 4. Contlnnance of this steep for forty-eight hours. 6. A thorough
purification of the gun-cotton from free acid by washing In a running stream for sev-
eral weeka. This may be supplemented by washing In a weak solntion of potash.
bat Is not absolutely necessary. The following are the important advanUges insured
by the new method of making gun-cotton :

For PurpoatM of ArlUlery,—!, The same initial velocity of the projectile can be
oMained by a charae of gnn-cottou one-fourth of the weight of gunpowder. 3.
There is no arooke from the exploaion of gun-cotton. 8. Gnn-cotton does not foul
the gnu. 4. Gun-cotton does not heat the gun to the Injurious dcffree of gunpowder.
5. Gnn-cottongives the same velocity to the projectile with much smaller recoil of
the gun. 6w Gun-cotton will produce the »ame initial velocity of projectile with a
fiboner length of barrel. 7. In projectiles of ttie nature of explooive aheli^ gun-



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eotton liaB the advantago of breaking tiie ahell more eqnaUy Into much mora
naiuerons pieces Ihau gunpowder. 8. Wheu truu-cottoa 1» iwed in fiheDs io^tead of
gnnpowder, a quauUly equal lu weight to on^-Uiird oC the laUer produces doable the
oxploaive force.

For Cicii EnginefHwj and Mining.— 9. In driving tunnela throngh hard rocl«, a
charge of gnu-coltou of givcu site exerts double tlio ux]>lo(»ive force of guupowdcr,
so as to render a anaaller number of boles necesaary. 10. Gun-cotton a«80 may be
so UHed as, in its explot^ion, to reduce tbe roclc to much smaller pieces than gunpow-
der, and so faciUtiite its removal. 11. As guu-coUon produces no unioke, Uio work
can proceed much more rapidly, and with lens injury to the healtli of the miners.
18. In working coal-mine?, the advantages of bringing down much lureer qaautities
of material with a given charge, and the absence of smoke in the expiosioUf enable
a much greater quantity of work to be done in a ^iven time at a given cohU 13.
The weight of gun-cotton required to produce a given effect in niimuK is only oue«
sixth part of the weight of gunpowder. 1-4. In blasting rock under water the wider
range and greater force of a given charge is a };rent element in cheaiMHiing the cost
of submarine work. 15. The peculiar loaii action of gun-cotton, to which the effects
of gunpowder sliew no analogy, enables the engineer to destroy and remove sub-
marine stoneA and rocks without the preliminary delay and exi)ense of boring cham-
bers for the charge.

For Military Engineering. — Ifi. The smaller weigiit of gun-cotton otters great
advantages in facility of transport, the weight l>eiug one-sixth ttiat of gunpowder.
17. The pecuhar localised action of gun-cotlou enables lite engineer to destroy
bridges and palie«ad(!8, and to remove every kind of obstacle with great facility. 18.
Por submarine expioskm, either in attack or defence, gun-cotton has the advantage
of n much wider range of destructive power than gunpowder. 19. For the same
purpose, gun-cotton, from its lightncsi^ has the advantage oC keeping afloat
the water-tight cose in which it 7s contained, while gunpowder sinks ft to the
bottom.

For Naval ITar/aiv.— 20. Where guns are close together, as in tbe batteries of
ships and casemnted forts, the absence of smoke removes the grest evil of the tiring
ot oue gun impeding the aim of the next, and thus gun-cotton facilitates rapid
flring. 21. Between-dccks also, the absence of smoke hIIowm continuous rapid flr*
iug to be maintttlne<i. The absence of fouliug and of heating aro equally udvaA-
tageous for naval as for military artillery.

Utneral Advantage. — Time, damp, and exposure do not alter its qualities when
carefully prepared. Being made in the form of rope, yarn, or, acconding to the
most recent improvement, in compressed discs, accidents cimnot arise from spilling
as in gunpowder. It is also believed to be f r. e from the danger of spontaneous
combustion, but this is perhaps not the case under all circumstMiices.

The dreadful explosion at the Gnn-Cotlon Mills. Stowmarket, in August 1871,
Iia^ thrown doubts on the safely of this 8ul)j»taiice. vV'iih re>f*i>oct to that puriiciihir
accident, evidiuice was givcu to shew that sulphuric acid had been inallclously added
to the gun-cotton, although this was not completely proved. Some minor accidents
have happened since, caiit*cd, so far as we can learn, by cjireleesness in handling
tlie mateiiul. However, the works at .Slownnirket luive been rebuilt, and guu-
cotton appears to be more or loss used for mining and quanting in several parts of
England.

GUN FACTORIES. Royal, are government establishments at Woolwich for the
connt ruction of great guns for the u«e ot the Britlch army and navj'. For a long
period there had been at Woolwich a small factory for the manufacture of brass
cannon, but guns of cast iron were obtained from private fonndrles by contract At
last It was determined that government should become in p:irt Its own gnn-founder,
and extensive works.lops were erected In lSM-1856. Tne adoption of the .Armstrong
wrought-iron gnu info general n<»e in the service, in 1S59, arrestttl the further mak-
ing of caM-lron guns, nmi occasioned again a great expenditure In the erection of
8h()p=* and costly machinery, which have since been o^iapted to the other PVhtcms of
wrought-iron ordnance adoptc<l into the service under the name of *' Woolwich."
Tne tactohes may now fairly be regarded as among the ni0!*t remarkable slcrhtj* in
the kingdom. In each department, whatever the process, it is repeated over and



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ovrr agnin, till lohg^parnllol llnrs of similar mills are seen, pach bimfly fashioning a
wparate gnu. Iroii nt rod-lioiit Is flrstt wound roniid a solid core (ropresentltig the
bon? of rhe futnre gnn), OBtapt* inJght bo round a pencil ; and tluMi by the action of
6nc<*«*8siv<» blows from a sliaui-liaiiinier (therein one of 100 tonf), the Btript* ar«
woldtnl into a compact cylinder of wrou^iit iron of extreme deiipit}*.
This lyl in diT, uf I cr undcrixoini; several hpniini:?* and pounding.* with the ste:im-
h ninier. i:* encomp:is<M» d witli wron;;lit-iron riny^s uf immen!»e strenjjtli, Mhicli nro
hhnnik on, and then trunsmifted to tlie borin«r-mllI. Here tlio i)roper cnlibre is Im-
parted to it ; in another department, tlic bore is rifled ; in anotlxr, flie outside of
the gun i» cjtrefidly turned ; and in >ef unotlier, tlie wliole is i)olished nud l)rowned.
A ^uii is Si'wral weeivs in its pHS»'H<,'e throUL'li tijese mnuy nro<M"«siH. Bv the inge-
nuity of Sir Wllli:im Armstrong, the superintendent, Mud I)r Jolin An«lerson, I)i9
al>le as^istant, every part of the difflcult niaiiufactiin' lias Inei. rctinced to u question
of inachini ry. Many tlious;ind gnus liave to tliis time l)eeii turned out complete,
of winch upward** of 7000 are now avMiIal)le for military or navnl U(*e. 'i he cost of
tiie guns as now made Is. on an aveiage, as follows : 'l2-pounder, 4:82; ?0-p(iunder,
jClS4; 40-pounder, jC^OU; To-jiounder, jC3T5 : .R.Vton gun, jC'2156. Tlie royal gun fac-'
tory at Woolwich was ehtimuttni to cost for 18THI— 1Sj9 the sum of X203,»48, of which
X-'>*.M2 were for luanagenieiit ; jCTS.CjO lor the w:iges of nrtlflrern and lalmrers;



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