94 G U M 
•J feg the double flaggon charge their hand ; 
See them puff off the froth, and gulp amain, 
While with,dry tongue I lick my lips in vain. Cay. 
GULP, /. As much as can be fwallowed at once.— 
In deep j'ufpiratipns we take more large gulps of air to 
cool our heart, overchanged with love and forrow. More, 
As oft as he can catch a gulp of air, 
And peep above the feas, he names the fair. Dryden, 
GULPE, a river of the duchy of Limburg, which 
runs into the Geul two miles above Fauquemont. 
GUL'PEN, a town of the Netherlands, in the duchy 
«f Limburg : four miles fouth of Fauquemont. 
GULPH, J'. See Gulf. 
GUL'ZOW, a town of Germany, in the circle of Up¬ 
per Saxony, in Hinder Pomerania: fourteen miles fouth- 
eaft of Cammin. 
GULat.] Themucilageof vegetables : 
He ripens fpices, fruit, and precious gum, 
Which from remoteft regions hither come. Waller . 
G um-is ufually tranfparent, more or lefs brittle when dry, 
though difficultly pulverable ; of an infipid, or flightly 
faccharine, tafte; ioluble in, or capable of combining 
with, water in all proportions, to which it gives a gluey, 
adheftve confidence in proportion as its quantity is 
greater. Thefe are the leading properties of gums, 
rightly fo called ; but the inaccurate cuftom of former 
• times applied the term gum to all concrete vegetable 
juices, fo that in common we hear of gum-copal, gum- 
fandarach, and other gums, which are either pure re¬ 
fills, or mixtures of refins with the vegetable mucilage. 
The only gums are., u. The common gums, obtained 
from the plum, the peach, the cherry-tree, &c. 2. 
Gum Arabic, which flows naturally from the acacia in 
Egypt, Arabia, Senegal, and elfewhere. 3. Gum 
adragant or tragacanth, from a plant growing in Sy¬ 
ria, "Crete, and other eaftern parts. It comes to us in 
fmall white contorted pieces refembling worms. It is 
ufually dearer than other gums, and forms a thicker 
jelly with water.-—For the chemical analylis of thefe 
gums, and for the properties and genera of gum-refnYs, 
fee the article Chemistry, vol. iv. pages 168, 169, 322, 
339, and 340.—And for further on Elastic Gum, fee 
the article Caoutchouc, vol. iii. p. 744-743, 
A very valuable liibftitute for foreign gums, as em¬ 
ployed by calico printers, and in many other branches 
of manufacture, has lately been difeovered by the earl 
of Dundonald, for which his majefty’s letters patent 
have been obtained, dated July 31, 180?. His lordffiip 
Hates this invention to conlift in procuring a fubftitute 
for gum-fenegal, or other gums, from theclafs of plants 
called in botany lichens, from the plants of hemp and 
flax, likewife from the bark or rind of a willow or 
lime-tree. The procefs for obtaining the gum maybe 
varied according to circumftances, and is done by wafli- 
ing the materials in water, digeftiori, and boilings, and 
with or without the aid of fixed volatile alkaline falts, 
or their- folutions. His lordfliip proceeds: “It does 
not appear, from fuch trials as I have hithirto made, 
that there is any very great difference in the produce of 
gum from the lichen colledted from different trees or 
fhrubs; all of them anfwer equally well for yielding a 
gum fit for calico printing. The lichen is molt abun¬ 
dant on the trees which grow in a poor ftiff clay foil, 
particularly if iituated at fome confiderable height above 
lea-level. It fliould be pulled in dry weather, other- 
wife it is apt to break in the pulling; befides, in this 
cafe, requiring to be dried before it can with l’afety be 
lain up in the ftore-houfe, where, if put in dry, it may 
be kept for years; ffiould a fufficient quantity of it not 
be found in this country, it may be had in almoft unli¬ 
mited abundance in Sweden, Norway, and in the north¬ 
ern part of America, where it grows to the length of 
from a foot to eighteen inches, deprefling the branches 
GUM 
of the tree by its Weight. Thefe is, however, every 
reafon to believe, that a fufficient quantity is to be had 
in this country, according to information from Dr. 
Brown, lecturer on botany. It takes three or four years 
in coming to maturity, of its full lize, fo that a crop 
from the fame tree may be had every fourth year. The 
lichen does not conlift entirely of a gummy matter : there 
is the outer Ikin Of cuticle, below that a green refinous 
matter ; the remainder of the plant conlifts'of partly 
gum, partly fomewhat analogous to animal fubftances, 
and a fmall proportion of fibrous matter, which cannot 
be dilfolved by boiling, Or the action of alkaline falts. 
“The firft procefs in preparing gum from the lichen i* 
to free it of the outer (kin of the plant and the refinous 
matter. This is done by fcalding tlie lichen two or three 
times with boiling water, allowing it to remain fo long 
in the water as by abforbing it to fwell; in doing this 
the Ikin cracks, and comes off along with the greateft 
part of the refinous matter; or it may be freed from them 
by gently boiling.the lichen for about fifteen Or twenty 
minutes, then walhing it in cold water, laying it after¬ 
wards on a ftone or brick floor, where it ffiould lie for 
ten or twelve hours, perhaps more. The reafon for this 
is, that the expofure for that time to air greatly facili¬ 
tates the fubfequent extraction of the gum. The fcald. 
ed lichen is then to be put into a copper boiler, with a 
due proportion of water, fay two wine-gallons to every 
pound of lichen, and boiled during ten or twelve hours, 
adding about a quarter of an ounce of foda or pearl- 
allies for every pound of lichen, or, inltead of thefe falts, 
about two ounces of volatile alkali. The boiling Ihotild 
be continued until the liquor acquires a confiderable de¬ 
gree of gummy confiftence. It is then to be taken out of 
the boiler, allowed to drain or drip through a wire or 
hair-cloth or fearfe. The refiduum to be put into a hair¬ 
cloth bag, and to be fqueezed in a prefs fimilar to 
that which is ufed by the melters or rinders of tallow. 
“The firft boiling does not extract the whole bf~the 
gum. The lichen ffiould be boiled a fecond or even 
a third time, repeating the procefs as above deferibed, 
diminiffiing at each procefs the quantity of water and 
the quantity of alkali, which a little experience will 
foon.point out: when three boilings are employed, the 
gummy extradt of the laft boiling fhould be kept for 
the firft boiling of a frefli batch of lichen ; the extradt 
proceeding from the firft and fecond boilings ffiou-ld be 
mixed together, and evaporated to the confiftence ne- 
ceffary for block or prefs printing. The evaporating 
veftels fliould be of tin or thin lead, placed over a range 
of ftpves, and moderately heated by fire, or the fteam of 
water. Before evaporating the gummy extradt to the 
confiftence neceffary, it fliould be kept ten or twelve 
hours, fo as to allow the fediment or dregs to fubfide. 
The clean liquor may either be drawn off by a fyplion, 
or the dregs may be drawn off by a cock, at the bottom 
of the wooden veffel; the bottom of which ffiould be 
made Hoping, higher at the back than the fore part, in 
order that the dregs may run more completely off. The 
proportion of gummy matter remaining in the dregs 
may be got off by mixing them with a due proportion 
of boiling water, allowing the liquor to clear, and pro¬ 
ceeding as above diredted, employing this weak folii-' 
tion for boiling the next batch of lichen. When vola¬ 
tile alkali is ufed, the boiler ffiould be iron, as vola¬ 
tile alkali adts on copper. Hemp, flax, and the bark of 
the willow and lime trees, or fea-weed, are to be heated 
in a fimilar manner, to extradt the gum or mucilage 
contained in them. When gum from the lichen is to 
be employed for making ink, manufacturing and Itain- 
ing paper, or for flattening lilks, crapes, and gauzes, it 
ffiould be extradted from the lichen without employing 
any alkaline falts, continuing the boiling or digeftion 
longer, and with a moderate degree of heat, in which 
cafe the gummy extradt will be nearly colourlefs.— 
This invention bids fair to produce an immenle faving 
to calico printers, as well as to every other fpecies of 
manufadture, 
