Z 01 
ZIZANIA, in botany, a genns of the 
Monoecia Hexandria class and order. Na- 
tural order of Gramina. Gramine®, Jus- 
sieu. Essential character: male, calyx 
none; corolla glume two-valved, awnless, 
mixed with the females : female, - calyx 
none ; corolla glume two-valved, cowled, 
awned ; style two-parted ; seed one, clothed 
w'ith the plaited corolla. There are two 
species ; viz, Z. aquatica and ,Z. terrestris. 
ZIZIPHORA, in botany, a genus of the 
Diandria Monogynia class and order. Na- 
tural order of Verticillatae. Labiatae, Jus- 
sieu. Essential character : calyx filiform ; 
corolla ringent, with the upper lip bent 
back and entire; seeds four. There are 
four species. 
ZODIAC, in astronomy, a broad circle, 
whose middle is the ecliptic, and its ex- 
tremes two circles, parallel thereto, at such 
a distance from it, as to bound or compre- 
hend the excursions of the sun and planets. 
The sun never deviates from the middle 
of the zodiac, i. e. from the ecliptic, but 
the planets all do more or less. Their 
greatest deviations, called latitudes, are the 
measure of the breadth of the zodiac, which 
is broader or narrower, as the greatest lati- 
tude of the planets is made more or less ; 
accordingly some make it sixteen, some 
eighteen, and some twenty degrees broad. 
The zodiac, cutting the equator obliquely, 
makes an angle therewith of about 23^“, 
which is what we call the obliquity of the 
zodiac, and is the sun’s greatest declina- 
tion. 
Tile zodiac is divided into twelve por- 
tions, called signs, and those divisions or 
signs are denominated from the constella- 
tions which anciently possessed each part; 
but the zodiac being immoveable, and the 
stars liaving a motion from west to east, 
those constellations no longer correspond 
to their proper signs, whence arises what 
we call the precession of the equinoxes. 
ZOEGEA, in botany, a genus of the 
Syngenesia Polygamia Frustranea class and 
Older. Natural order of Compositae Cap'- 
tat£B. Cinarocephalae, Jussieu. Essential 
character : calyx imbricate ; corolla of the 
ray ligulate ; down bristle-shaped ; recep- 
tacle bristly. There is but one species, viz. 
Z. leptaurea, a native of the Levant. 
ZOISITE, in mineralogy, is of a greyish 
colour. It occurs massive, and in crystals, 
which are imbedded^ It occurs in primitive 
mountains, principally in quartz with mica. 
This fossil is placed between the axinite 
and pistazite, and connects both species 
together. 
ZOO 
ZONE, in geography and astronomy, 
a division of the terraqueous globe, with 
respect to the different degrees of heat 
found in the different parts thereof. A 
zone is the fifth part of the surface of the 
earth, contained between two parallels. 
The zones are denominated torrid, frigid, 
and temperate. The torrid zone is a band 
surrounding the terraqueous globe, and ter- 
minated by the two tropics. Its breadth 
is 46° 58'. The equator, running through 
the middle of it, divides it into two equal 
parts, each containing 23“ 29'. Tlie an- 
cients imagined the torrid zone uninhabi- 
table. The temperate zones are two bands, 
environing the globe, and contained be- 
tween the tropics and the polar circles : 
the breadth of each is 43° S'. The frigid 
zones are segments of the surface of the 
earth, terminated, one by the antarctic, and 
the other by the arctic circle. The breadth 
of each is 46° 68'. 
ZONITES, in natural history, a genus 
of insects of the order Coleoptera : an- 
tenna5 testaceous ; four feelers filiform ; 
jaw entire, longer than the feelers ; lip 
emarginate. There are eight species, found 
chiefly in warm countries. 
ZOOLOGY, constitutes that branch of 
natural history which relates to animals. 
Various methods of arrangement have, by 
different naturalists, been devised to render 
this branch, of study easy of comprehen- 
sion, and familiar to the minds of those 
who wish for a general view of animated 
nature. We shall, in this article, give an 
outline of the Linnsean system, which has, 
in the various departments of the British 
Encyclopedia, been adopted, as most gene- 
rally approved by our own countrymen, 
and by many philosophers of all countries. 
Linneeus divides tiie whole animal king- 
dom into six classes, the characters of w hich 
are taken from the internal structure of the 
being treated of. It may be observed, that 
a considerable portion of the bulk of ani- 
mals is composed of tubular vessels, which 
originate in a heai't : the heart propels 
through the arteries, with the assistance of 
tlieir own muscular powders, either a colour- 
less transparent fluid, or a red blood, into 
the extremities of the veins; through which 
it again returns to the origin of motion. 
Insects and worms have their circulating 
fluids a little w.rrmer than the surrounding 
medium, and in general it is colourless ; 
but insects have legs furnished with joints, 
and worms have nothing but simple tenta- 
cuia at most, in place of legs. Fishes have 
cold red blood, which is exposed to the air 
