DYE 
DYS 
D Y T 
£/• 5 
•ontains the same colouring matter, but 
in smaller quantity. The bark of the birch 
.also, and many other trees, may be used for 
the same purpose. It is very probable that 
the brown colouring matter is in these vege- 
table substances combined with tan. This is 
certainly the case in sumach, which is often 
employed to produce a brown. This com- 
bination explains the reason why no mordant 
is necessary ; the tan has a strong affinity for 
cloth, and the colouring matter for the tan. 
The dye-stuff, and the mordant, are already, 
in fact, combined together. 
Of dyeing compound colours. — Compound 
colours are produced by mixing together two 
simple ones ; or, which is the same thing, by 
dyeing doth first one simple colour, and then 
another. These colours vary to infinity, ac- 
cording to the proportions of the ingredients 
employed. They may be arranged under 
the following classes. 
Mixtures of, 1 . Blue and yellow ; 2. Blue 
and red ; 3. Yellow and red ; 4. Black and 
other colours. 
Mixture of blue and yellow. — This forms 
green ; which is distinguished by dyers into a 
variety of shades, according to the depth of 
the shade, or the prevalence of either of the 
component parts. Thus we have sea-green, 
grass-green, pea-green, See. 
Wool, silk, and linen, are usually dyed 
green by giving them lirst a blue colour, and 
afterwards dyeing them yellow ; because, 
when the yellow is first given, several incon- 
veniences follow : the yellow partly separates 
again in the blue vat, and communicates a 
green colour to it, and thus renders it useless 
lor every other purpose, except dyeing green. 
Any ot the usual processes for dyeing blue 
and yellow may be followed, taking care to 
proportion the depth of the shades to that of 
the green required. When sulphate of indigo 
is employed, it is usual to mix all the ingre- 
dients together, and to dye the cloth at once; 
tiiis produces what is known by the name of 
Saxon or English green. 
Mixtures of blue and red . — These form 
different shades of violet, purple, and li- 
lac. Wool is generally first dyed blue, and 
afterwards scarlet, in the usual manner. By 
means of cochineal mixed with sulphate of 
indigo, the process may be performed at 
once. Silk is first dyed crimson, by means 
of cochineal, and then dipped into the indigo 
vat. Cotton and linen are first dyed blue, 
then galled, and soaked in a decoction of 
logwood; but a more permanent colour is 
given by means of oxide of iron. 
Mixtures of yellow and red. — These pro- 
duce orange. When blue is combined with 
red and yellow on cloth, the resulting colour 
is olive. Wool may be dyed orange, by 
first dyeing it scarlet, and then yellow. 
When it is dyed first with madder, the result 
is cinnamon-colour. 
Silk is dyed orange by means of cartha- 
mus; a cinnamon colour by logwood. Bra- 
zil-wood, and fustic mixed together. 
Cotton and linen receive a cinnamon- 
colour by means of weld and madder; and 
an olive-colour, by being passed through a 
blue, yellow, and then a madder-bath. 
__ Mixtures of black with other colours . — 
These constitute greys, drabs, and browns. 
If cloth is previously combined with brown 
oxide ot iron, and afterwards dyed yellow 
with quercitron bark, the result will be a 
drab of different shades, according to the 
proportion of mordant employed. When 
the proportion is small, the colour inclines 
to olive, or yellow; on the contrary, the 
drab may be deepened or saddened, as the 
dyers term it, by mixing a little sumach with 
the bark. See Calico-Printing. 
DYERS. Bystat. 3 & 4 Ed. VI. c. 2, no 
dyer may dye any cloth with orchel, or with 
brazil, to make a false colour in cloth, wool, 
See. on penalty of 20s. By stat. 23 Eliz. 
c. 9, dyers are to fix a seal of lead to cloths, 
with the letter M, to shew that they are well 
maddened, See. or forfeit 3s. 4 d. per yard. By 
stat. 23 Geo. 111. c. 15, several penalties are 
inflicted on dyers who dye any cloths deceit- 
fully, and not woaded throughout with indigo 
and madder. Dying blue with logwood, to 
forfeit 20/. Dyers in London are subject to 
the inspection of the dyers’ company, who 
appoint searchers. In other places, these 
are appointed by the justices, and opposing 
the searchers incurs a penalty of 10/. 
DYNASTY, among ancient historians, 
signifies a race or succession of kings of the 
same line or family : such were the dynasties 
ot Egypt. The Egyptians reckon thirty 7 
dynasties, within the space of 36525 years ; 
but the generality of chronologers look upon 
them as fabulous. And it is very 7 certain, 
that these dynasties are not continually suc- 
cessive, but collateral. 
DYSENTERY. See Medicine. 
DYSOREXY, among physicians, denotes 
a want of appetite, proceeding from a weak 
stomach. 
DYSPEPSY, a difficulty of digestion, 
for which physicians prescribe bitters. See 
Medicine. 
DYSPNtEA, a difficulty of breathing, 
usually called asthma. See Medicine. 
DYSURY, in medicine, a difficulty of 
making urine, attended with a sensation of 
heat and pain. It is distinguished from a 
strangury, as, in the last, the urine is voided 
by only a drop, as it were, at a time, but 
however with pain ; and from an ischurv, as 
in this disorder there is an almost total" sup- 
pression of urine. See Medicine. 
DYTISCUS, the water-beetle, in 
zoology, a genus of insects of the order of 
coleoptera ; the antenna; of which are slender 
and setaceous, and the hind feet are hairs', 
and formed for swimming. There are 23 
species, distinguished by their antennae, the- 
various colours of the elytra. See. The 
larvae of the dytiscus are often met with in 
water. They are oblong, and have six scaly 
feet. The body consists of eleven segments. 
The head is large, with four filiform antenna’, 
and a strong pair of jaws. The last segments 
of the body have rows of hairs on the sides ; 
and the abdomen is terminated by two spines 
charged with the like hairs, forming a kind of 
plumes. These larvae are frequently of a 
greenish variegated brown: they are lively, 
active, and extremely voracious : they devour 
and feed upon other water-insects, and often 
tear and destroy 7 each other. The perfect 
insect is little inferior to its larva:; in vora- 
ciousness, but it can only exercise its cruelty 
on the larva; ; the perfect insects, like himself, 
being sheltered by the kind of scaly cuirass 
with which they are armed. This creature 
must be touched cautiously ; for, besides its 
power of giving a severe gripe with its jaws, 
it has moreover under the thorax, another 
weapon, a long sharp spine, which it will 
drive into one’s fingers by the effort it makes 
to move backwards. The eggs of the dytisci 
are rather large, and are by them inclosed in 
a kind of silky duskish cod, of a strong and 
thick texture, in form round, and terminated 
by a long appendix or slender tail, of the 
same substance. These cods are often found 
in the water, and from them are brought forth 
the eggs and larva; of the dytisci. The 
strength of these cods probably serves the 
insect to defend their eggs from the vora- 
ciousness of several other aquatic insects, and 
even from that of their fellow-dytisci, who 
would not spare them. 
Many species of the perfect insect are 
common in stagnated waters, which they quit 
in the evening to fly about. They swim with 
incredible agility, making use of their hinder 
legs after tire fashion of oars. The elytra of 
the females are, in general, furrowed, and 
those of the male plain. When they first 
arrive at their perfect state, their elytra are 
almost transparent, and in many species of a 
beautiful dun colour, mingled with shades of 
a greenish brown. The best method of 
catching them is with a hand-net or sieve ; 
for they are so nimble, and exercise their 
defensive weapons so often, and with such 
painful success to those w'ho endeavour to 
catch them, that they are very often obliged 
to let them escape ; the easiest way to kill 
them is, to let them fall into boiling-hot water, 
which instantly destroys tliein f See Plate 
Nat. Hist. fig. 175. 
