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colouring matter : and 2dly, from tlie ace- 
tic acid disengaged in the process, not act- 
ing with the same force on tlie colouring 
matter as the sulphuric acid would do. The 
acetate being also very soluble, and having 
little tendency to crystallize, can be more 
equally mixed and applied. The discovery 
of this mordant, so essential in the art of 
calico-printing, was altogether accidental, 
or rather empirical. Tlie recipes of the 
calico-printers were at one time very com- 
plicated ; different articles were from time 
to time omitted or changed, until at length 
the simple mixture of alum and acetate of 
lead was found to answer as a mordant, 
equally with compositions more compli- 
cated; and even after its discovery, its 
operation for a time was far fi-om being 
understood by the artist. The mordant 
thus prepared is thickened with gum or 
starch; or in this country, within these 
few years, with the mucilage prepared from 
lichens scalded and boiled with a little pot- 
ash. It is applied by wooden blocks, or 
stamps to the parts of the cloth on which 
the figures cut in the stamp are designed to 
be impressed, or by a pencil if more deli- 
cate lines are to be traced. The cloth is 
afterwards dried thoroughly, is washed in 
warm water to remove the mucilage and 
the superfluous mordant, and is then dipped 
in the dye colour, suppose it to be an infu- 
sion of madder ; the whole is dyed, but the 
parts which have been impregnated witli 
the mordant, receive a brighter colour 
than the part which has not: tlie colour 
too of the former is permanent, while that 
of the latter is fugitive. It is discharged 
by subsequent boiling with substances hav- 
ing a weak attraction to the colouring mat- 
ter, principally with bran, and by exposure 
on the field, repeating these alternately. 
The ground of the cloth is thus at length 
rendered white, while the colours of the 
parts on which the mordant has been im- 
pressed, representing of course the design 
on the stamp, remain with little or no alte- 
ration. 
Sometimes after the whole cloth has been 
permanently dyed, by having been impreg- 
nated with the mordant, the colour is dis- 
charged from certain parts, by stamping 
these witli a weak acid liquor : after being 
washed, these are again stamped, either 
with tue same or with a different mordant, 
and dyed w'ith different materials ; and thus 
the most difficult kind of cloth printing is 
effected, where the ground is coloured, and 
at the same time impressed with a design 
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in different colours. By combining these 
methods too, and by dextrously applying 
to different parts of the cloth different mor- 
dants, by stamps adapted to each other, 
so as to form a regular design, different 
colours are impressed either on a white or 
coloured ground. 
CALK, a genus of minerals, which is di- 
vided into twenty species. 1. Rock-milk, 
denominated by Werner, bergmilch. 2. 
Chalk, denominated kreide, or creta alba : 
external characters ; colour white ; occurs 
massive disseminated, and as a crust cover- 
ing flint ; fragments indeterminately angu- 
lar, blunt edged ; opaque ; soils ; writes ; 
easily frangible ; specific gravity according 
to Kirwan 2.3, but bishop Watson takes it 
at 2.6 ; various specimens will no doubt ac- 
count for this and other differences of the 
same kind. It effervesces strongly with 
acids, and is found to consist almost entire- 
ly of lime and carbonic acid. It constitutes 
a peculiar kind of formation ; contains nu- 
merous flinty petrefactions ; and is even re- 
markable for being the most general reposi- 
tory of flint. It is found chiefly on sea- 
coasts, as at Calais and Dover, and several 
of the Danish islands in the Baltic, as Rugen 
and Zealand : it occurs also in Poland, and 
several great tracts of country in the south 
of England are composed of it. In some 
parts of Kent a chalkpit is no contemptible 
estate, producing from one to five hundred 
per annum and upwards. In the manu- 
factures it is used for polishing and cleansing 
metals, glass, &c. and when burnt into lime 
it is of great importance in building. 3. 
Lime-stone ; denominated kalkstein, which 
is divided into four sub-species, viz. com- 
pact-limestone ; foliated limestone ; fibrous 
limestone; peastone. The first is of a 
greyish colour, composed chiefly of lime 
and carbonic acid, with small portions of 
iron, alumina, and inflammable matter ; and 
is found in the sandstone and coal forma- 
tions of Saxony, Bohemia, Bavaria, Swe- 
den, France, England, Scotland, &c. It is 
used as mortar, when deprived of its carbo- 
nic acid, and in this state also it is employed 
in the manufaeture of soap, in tanning, 
and other processes. It is likevrise used as 
a flux, in the reduction of such ores as are 
difficultly fusible, by means of its silica and 
alumina. The Florentine arborescent mar- 
ble, a variety of this species, is, according to 
Jameson, very valuable for the purposes of 
ornament ; and the limestone of Pappen- 
heim serves for paving, grave-stones, and 
sometimes for polishing plate-glass. Of the 
