DUC 
Icosandria Polygynia class and order. Na- 
tural orderof Senticosa?. Rosaceae, Jussieu. 
Essential character : calyx five to ten cleft ; 
petals five to eight; seeds tailed, hairy. 
There are two species, viz. D. anemonoides, 
aud D. octopetala. The latter is a delicate 
evei'green plant, with snow-white blossoms. 
The stalks and branches are woody, and 
perennial, lying flat upon the ground, 
spreading wide about the roots in tufts. 
It is a native of high mountains in Lapland, 
Denmark, and Switzerland. Also ip Scot- 
land and in some parts of Yorkshire.^. It- 
flowers in June. 
DRYPIS, in botany, a genus of the Pen- 
tandiia Trigynia class and order. Natural 
order of Caryophyllei. Essential character : 
calyx five-toothed; petals five; capsules 
clipped round, one seeded. There is only 
one species, viz. D. spinosa, the leaves of 
which are subulate, somewhat three cor- 
nered, niucronate ; those at the subdivisions 
of the stem are lanceolate, with three 
teeth on each side; peduncles shorter than 
the flower ; calyx erect ; corolla crowned, 
as in Silene, purple or white ; petals very 
narrow, spreading; stamens erect. It is 
biennial: native of Barbary, Italy, and 
Istria. 
DUCATOON, a silver coin, frequent in 
several parts of Europe. See Coin — Table. 
DUCES tecum, in law, a writ that com- 
mands a person to appear in the Court of 
Chancery, and bring vi’ith him certain 
writings, evidences, or other things, which 
the court is inclined to view. 
DUCK. See Anas. 
DUCKING at the main-yard, among sea- 
men, is a way of punishing offenders on 
board a ship ; and is performed by binding 
the malefactor, by a rope, to the end of the 
yard, from whence he is violently let down 
into the sea, once, twice, or three times, 
according to his offence : and if the offence 
be vei-y great, he is drawn underneath the 
the keel of the sliip, w’hich they call keel- 
haleing. 
DUCT, in general, denotes any tube or 
canal. See Anatomy. 
DUCTILITY, in physics, a property of 
certain bodies, whereby they are capable 
of being expanded, or stretched forth, by 
means of a hammer, press, &c. 
The great ductility of some bodies, espe- 
cially gold,, is vei-y surprising: the gold- 
beaters and wire-drawers furaisli us with 
abundant proofs of this property; they, 
every day, reducg,gold into lamellm incon- 
DUC 
ceivably thin, yet without tlie least aper- 
ture, or pore discoverable, even by the 
microscope : a single grain of gold may be 
stretched under the hammer into a leaf that 
will cover many square inches, and yet the 
■ leaf remain so compact, as not to transmit the 
rays of light, nor even admit spirit of wine 
to transude. Dr. Halley took the following 
method to compute the ductility of gold : he 
learned from the wire-drawers that an ounce 
of gold is sufficient to gild, that is, to cover 
or coat a silver cylinder of forty-eight ounces 
weight, which cylinder may be drawn out 
into a wire so very fine tliat two yards 
thereof shall only weigh one grain ; and con- 
sequently ninety-eight yards of the same 
wire only forty-nine grains : so that a single 
grain of gold here gilds ninety-eight yards ; 
and, of course, the ten-thousandth part of a 
grain is here above one-third of an inch 
long. And since the third part of an inch 
is yet capable of being divided into ten les- 
ser parts visible to the naked eye, it is evi- 
dent that the hundred-thousandth part of a 
grain of gold may be seen without the assis- 
tance of a microscope. Proceeding in his 
calculus, he found, at length, that a cube of 
gold, whose side is the hundredtlj part of 
an inch, contains 2,433,000,000 visible 
parts ; and yet, though the gold wherewith 
such wil e is coated, be stretched to such a 
degree, so intimately does its parts cohere 
that there is not any appearance of the 
colour of the silver underneath. 
Mr. Boyle, examining some leaf-gold, 
found that a grain aud a quarter’s weight 
took up an area of fifty square inches ; sup- 
posing therefore the leaf divided by parallel 
lines of an inch apart, a grain of gold 
will be divided into five hundred thousand 
minute squares, all discernible by a good 
eye : and the same author shews, that an 
ounce of gold drawn out into wire, would 
reach 155 miles and a half. 
But M. Reaumur has carried the duc- 
tility of gold to a still greater length : a gold 
wire every body knows is only a silver one 
gilt. This cylinder of silver, covered with 
leaf gold, they draw' through the hole of an 
iron, and the gilding still keeps pace with 
the wire, stretch it to what length they 
can. Now M. Reaumur shews that in the 
common way of drawing gold-wire, a cylin- 
der of silver twenty-two inches long and 
fifteen lines in diameter is stretched to 
1,16 j, 520 feet, or is 634,692 lines longer 
than before, which amounts to about ninety- 
seven leagues. To wind this throad on silk ’ 
for use they first flatten it, in doing which it 
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