D.

DAHLINE, the same as Inuline, the fecula obtained from elecampane,

analogous in many respects to starch. It is not employed in the arts.

DAMASCUS BLADES, are swords or scymitars, presenting upon their surface

a variegated appearance of _watering_, as white, silvery, or black

veins, in fine lines, or fillets; fibrous, crossed, interlaced or

parallel, &c. They are brought from the East, being fabricated chiefly

at Damascus, whence their name. Their excellent quality has become

proverbial; for which reason these blades are much sought after by

military men, and are high priced. The oriental processes have never

been satisfactorily described; but of late years methods have been

devised in Europe to imitate the fabric very well.

Clouet and Hachette pointed out the three following processes for

producing Damascus blades: 1, that of _parallel fillets_; 2, that by

_torsion_; 3, the _mosaic_. The first, which is still pursued by some

French cutlers, consists in scooping out with a graving tool the faces

of a piece of stuff composed of thin plates of different kinds of steel.

These hollows are by a subsequent operation filled up, and brought to a

level with the external faces, upon which they subsequently form

tress-like figures. 2. The method of torsion, which is more generally

employed at present, consists in forming a bundle of rods or slips of

steel, which are welded together into a well-wrought bar, twisted

several times round its axis. It is repeatedly forged, and twisted

alternately; after which it is slit in the line of its axis, and the two

halves are welded with their outsides in contact; by which means their

faces will exhibit very various configurations. 3. The mosaic method

consists in preparing a bar, as by the torsion plan, and cutting this

bar into short pieces of nearly equal length, with which a faggot is

formed and welded together; taking care to preserve the sections of each

piece at the surface of the blade. In this way, all the variety of the

design is displayed, corresponding to each fragment of the cut bar.

The blades of Clouet, independently of their excellent quality, their

flexibility, and extreme elasticity, have this advantage over the

oriental blades, that they exhibit in the very substance of the metal,

designs, letters, inscriptions, and, generally speaking, all kinds of

figures which had been delineated beforehand.

Notwithstanding these successful results of Clouet, it was pretty clear

that the watered designs of the true Damascus scymitar were essentially

different. M. Bréant has at last completely solved this problem. He has

demonstrated that the substance of the oriental blades is a cast-steel

more highly charged with carbon than our European steels, and in which,

by means of a cooling suitably conducted, a crystallization takes place

of two distinct combinations of carbon and iron. This separation is the

essential condition; for if the melted steel be suddenly cooled in a

small crucible or ingot, there is no damascene appearance.

If an excess of carbon be mixed with iron, the whole of the metal will

be converted into steel; and the residuary carbon will combine in a new

proportion with a portion of the steel so formed. There will be two

distinct compounds; namely, pure steel, and carburetted steel or

cast-iron. These at first being imperfectly mixed will tend to separate,

if while still fluid they be left in a state of repose; and form a

crystallization in which the particles of the two compounds will place

themselves in the crucible in an order determined by their affinity and

density conjoined. If a blade forged out of steel so prepared be

immersed in acidulous water, it will display a very distinct damascus

appearance; the portions of pure steel becoming black, and those of

carburetted steel remaining white, because the acids with difficulty

disengage its carbon. The slower such a compound is cooled, the larger

the damascus veins will be. Travernier relates that the steel crucible

ingots, like those of wootz, for making the true oriental damascus, come

from Golconda, that they are of the size of a halfpenny roll, and when

cut in two, form two swords.

Steel combined with manganese forges easily, but it is brittle when

cold; it displays however the damascus appearance very strongly.

A mixture of 100 parts of soft iron, and 2 of lamp black, melts as

readily as ordinary steel. Several of the best blades which M. Bréant

presented to the Société d’Encouragement are the product of this

combination. This is an easy way of making cast-steel without previous

cementation of the iron. 100 parts of filings of very gray cast-iron,

and 100 parts of like filings previously oxidized, produced, by their

fusion together, a beautiful damascene steel, fit for forging into white

arms, sabres, swords, &c. This compound is remarkable for its

elasticity, an essential quality, not possessed by the old Indian steel.

The greater the proportion of the oxidized cast iron, the tougher is the

steel. Care should be taken to stir the materials during their fusion,

before it is allowed to cool; otherwise they will not afford a

homogeneous damasc. If the steel contains much carbon it is difficult to

forge, and cannot be drawn out except within a narrow range of

temperature. When heated to a red-white it crumbles under the hammer; at

a cherry-red it becomes hard and brittle; and as it progressively cools

it becomes still more unmalleable. It resembles completely Indian steel,

which European blacksmiths cannot forge, because they are ignorant of

the suitable temperature for working it. M. Bréant, by studying this

point, succeeded in forging fine blades.

Experience has proved that the orbicular veins, called by the workmen

_knots_ or _thorns_ (_ronces_), which are seen upon the finest Eastern

scymitars, are the result of the manner of forging them, as well as the

method of twisting the Damascus bars. If these be drawn in length, the

veins will be longitudinal; if they be spread equally in all

directions, the stuff will have a crystalline aspect; if they be made

wavy in the two directions, undulated veins will be produced like those

in the oriental damascus.

DAMASK is a variegated textile fabric, richly ornamented with figures of

flowers, fruits, landscapes, animals, &c., woven in the loom, and is by

far the most rich, elegant, and expensive species of ornamental weaving,

tapestry alone excepted. The name is said to be derived from Damascus,

where it was anciently made.

Damask belongs to that species of texture which is distinguished by

practical men by the name of tweeling, of which it is the richest

pattern. The tweel of damask is usually half that of full _satin_, and

consequently consists of eight leaves moved either in regular succession

or by regular intervals, eight leaves being the smallest number which

will admit of alternate tweeling at equal intervals.

In the article CARPET, two representations have been given of the damask

draw-loom.

The generic difference of tweeling, when compared with common cloth,

consists in the intersections, although uniform and equidistant, being

at determinate intervals, and not between the alternate threads. Hence

we have specimens of tweeled cloth, where the intersections take place

at the third, fourth, fifth, sixth, seventh, eighth, or sixteenth

interval only. The threads thus deflecting only from a straight line at

intervals, preserve more of their original direction, and a much greater

quantity of materials can be combined in an equal space, than in the

alternate intersection, where the tortuous deflection, at every

interval, keeps them more asunder. On this principle tweeled cloths of

three and four leaves are woven for facility of combination alone. The

coarser species of ornamented cloths, known by the names of dornock and

diaper, usually intersect at the fifth, or half satin interval. The

sixth and seventh are rarely used, and the intersection at the eighth is

distinguished by the name of satin in common, and of damask in

ornamental tweeling. It will further be very obvious, that where the

warp and woof cross only at every eighth interval, the two sides of the

cloth will present a diversity of appearance; for on one side the

longitudinal or warp threads will run parallel from one end of a web to

the other, and, on the other, the threads of woof will run also

parallel, but in a transverse direction across the cloth, or at right

angles to the former. The points of intersection being only at every

eighth interval, appear only like points; and in regular tweeling these

form the appearance of diagonal lines, inclined at an angle of 45° (or

nearly so) to each of the former.

The appearance, therefore, of a piece of common tweeled cloth is very

similar to that of two thin boards glued together, with the grain of the

upper piece at right angles to that of the under one. That of an

ornamental piece of damask may, in the same manner, be very properly

assimilated to a piece of veneering, where all the wood is of the same

substance and colour, and where the figures assume a diversity of

appearance from the ground, merely by the grain of the one being

disposed perpendicularly to that of the other. See TEXTILE FABRIC.

From this statement of the principle, it results that the most unlimited

variety of figures will be produced, by constructing a loom by which

every individual thread of warp may be placed either above or below the

woof at every intersection; and to effect this, in boundless variety, is

the object of the Jacquard mounting; which see.

The chief seat of this manufacture is probably the town and

neighbourhood of Dunfermline, in Fifeshire, and Lisburn and Ardoyne,

near Belfast, where it is considered as the staple, having proved a very

profitable branch of traffic to the manufacturer, and given employment

to many industrious people.

The material used there is chiefly linen; but many have been recently

woven of cotton, since the introduction of that article into the

manufacture of cloth has become so prevalent. The cotton damasks are

considerably cheaper than those of linen; but are not considered either

so elegant or durable. The cotton, also, unless frequently bleached,

does not preserve the purity of the white colour nearly so well as the

linen.

DAMASKEENING; the art of ornamenting iron, steel, &c., by making

incisions upon its surface, and filling them up with gold or silver

wire; chiefly used in enriching sword blades, guards, and gripes, locks

of pistols, &c.

Its name shows the place of its origin, or, at least, the place where it

has been practised in the greatest perfection; viz. the city of

Damascus, in Syria; though M. Felibien attributes the perfection of the

art to his countryman, Cursinet, who wrought under the reign of Henry

IV.

Damaskeening is partly mosaic work, partly engraving, and partly

carving. As mosaic work, it consists of pieces inlaid; as engraving, the

metal is indented, or cut in intaglio; and as carving, gold and silver

are wrought into it in _relievo_.

There are two ways of damaskeening; in the first, which is the most

beautiful, the artists cut into the metal with a graver, and other tools

proper for engraving upon steel, and afterwards fill up the incisions,

or notches, with a pretty thick silver or gold wire. In the other, which

is only superficial, they content themselves to make hatches, or

strokes across the iron, &c. with a cutting knife, such as is used in

making of small files. As to the first, it is necessary for the gravings

or incisions to be made in the dove-tail form; that the gold or silver

wire, which is thrust forcibly into them, may adhere the more strongly.

As to the second, which is the more usual, the method is this:--Having

heated the steel till it changes to a violet, or blue colour, they hatch

it over and across with the knife; then draw the ensign or ornament

intended, upon this hatching, with a fine brass point or bodkin. This

done, they take fine gold wire, and conducting or chasing it according

to the figures already designed, they sink it carefully into the hatches

of the metal with a copper tool.

DAMASSIN is a kind of damask, with gold and silver flowers, woven in the

warp and woof; or occasionally with silk organzine.

DAMPS, in mining, are noxious exhalations, or rather gases, so called

from the German _dampf_, vapour. There are two principal kinds of mine

gases, the _fire-damp_, or carburetted hydrogen, and the _choke-damp_,

or carbonic acid gas. See MINES.

DAPHNINE; the bitter principle of the _Daphne Alpina_.

DATOLITE. A mineral composed of silica, lime, and boracic acid.

DECANTATION, (Eng. and Fr.; _Abgiessen_, Germ.) is the act of pouring

off the clear supernatant fluid from any sediment or deposit. It is much

employed in the chemical arts; and is most conveniently effected by a

syphon.

DECOCTION, (Eng. and Fr.; _Abkochung_, Germ.) means either the act of

boiling a liquid along with some organic substance, or the liquid

compound resulting from that act.

DECOMPOSITION, (Eng. and Fr.; _Zersetzung_, Germ.) is the separation of

the constituent principles of any compound body. The following table,

the result of important researches recently made by M. Persoz, Professor

of Chemistry at Strasburgh, shows the order in which decompositions take

place among the successive substances.

Nitric Acid. Muriatic Acid.

Oxide of Magnesium Oxide of Magnesium

-- Silver -- Cobalt

-- Cobalt -- Nickel

-- Nickel Protox. of Mercury

Protox. of Cerium -- Cerium

Oxide of Zinc Oxide of Zinc

Protox. of Manganese Protox. of Manganese

Oxide of Lead -- Iron

-- Cadmium -- Uranium

-- Copper -- Copper

-- Glucinum Tin

-- Alumium Oxide of Glucinum

-- Uranium -- Alumium

-- Chromium -- Uranium

Protox. of Mercury -- Chromium

Oxide of Mercury -- Iron

-- Iron -- Tin

-- Bismuth -- Bismuth

-- Antimony

By means of the cupric oxide we may separate, 1, the ferric oxide from

the manganous oxide; 2, the cobaltic, nickelic, zincic and cerous oxides

from the uranic, ferric, chromic, and aluminic oxides; 3, the ferrous

oxide from the chromic oxide, when dissolved in the muriatic acid.

In boiling a muriatic solution of the cobaltic, nickelic, and manganous

oxides, with the mercuric oxide, the first two oxides alone are

precipitated. Alumina separates the cadmic oxide from the bismuthic

oxide, the stannous oxide from the stannic oxide, and the stannous oxide

from the antimonic acid. The cupric oxide separates also by

precipitation, the aluminic, uranic, chromic, titanic, and vanadic

oxides from all the oxides which are precipitable in the state of

sulphuret, by hydrosulphuret of ammonia.