A Z A 
h rough- the refracting medium, from the 
point of refraction, perpendicular to the re- 
iacting superficies. 
Axis, in architecture. Spiral axis is the 
ixis ot a twisted column drawn spirally in 
ijrder to- trace the circumvolutions, without. 
Axis of the Ionic capital, is a line passing 
perpendicularly through the middle of the 
eye of the volute. 
Axis of a vessel,. is an imaginary right line 
passing through the middle of it perpendi- 
cularly to its base, and equally distant from 
its sides. 
Axrs of a magnet, is a line passing through 
the middle of a magnet lengthwise in such 
a manner as that, however the magnet is di- 
vided, provided the division is made accord- 
ing to a plane in which such line is found, the 
magnet will be cut or separated into two 
loadstones ; and the extremes of such lines 
are called the poles of the magnet, 
i Axis, in anatomy, the second vertebra of 
the neck, so ealjed from the head’s turning 
on it like an axis. 
Axis, in zoology, an animal of the deer 
kind. SeeCERvus. 
AXY RiS, in botany, a genus of the trian- 
dria order, belonging to the monoecia class of 
plants, and in the natural method ranking 
under the twelfth order, holoraceae. The 
calyx of the male is tripartite; it has no co- 
rolla. The calyx of the female consists of 
jtwo leaves; it has two styli and one seed. 
There are three species, all annual, and na- 
tives of Siberia. 
j AYE-AYE, in zoology, a singular qua- 
druped discovered in Madagascar. Its name 
is an exclamation of the inhabitants, which 
LM. Sonnerat applied to this animal. Bqth 
pale and female are slothful and gentle ani- 
anals;and, like owls, they are scarcely able to 
discern objects in the day-time. They live 
chiefly under ground, feeding on worms and 
insects which they find in the earth or in 
jCrevices in the trunks of trees, whence 
I they extract them by means of their long 
jandslender toe. Sonnini forms a new genus 
jof this animal, the generic character of which 
Ss the long toes, the thumb of the hinder pair 
being' turned backw ard. 
AYENIA, in botany, a genus of the pen- 
tandria order, belonging to the gynandria 
class of plants, and in the natural method 
ranking under the 37th order, columniferse. 
The calyx has two leaves ; the petals are in , 
the form of a star, with long ungues ; and the 
papsule lias five cells. There are four spe- 
cies, all natives of the West Indies. 
AZAB, in the Turkish armies, a distinct 
body of soldiery-, who are great rivals of the 
Janizaries. 
AZALEA, an American upright honey- 
suckle, a genus of the monogynia order, and 
pentandria class of plants ; and in the natural 
method ranking under the 18th order, bi- 
:ornes. The corolla is bell-shaped ; the sta- 
mina are inserted into the receptacle, and 
:he capsule has 5 cells. There are 7 species, 
>f which the most remarkable are the fol- 
owing: 
1. Azalea nudiflora, or red American up- 
■ight honeysuckle, grows taller than the vis- 
:osa, and in its native country will sometimes 
.rrive at the height of 12 feet, but in Britain 
lever rises to above half that height. It has 
everal stems with oblong smooth leaves, 
.'he flower-stalks arise from the division of j 
A Z 0 
A Z O tgi 
the tranches, which are long and naked, sup- 
porting a cluster of red flowers: these are 
divided at the top into 5 equal segments, 
which spread open. 
2. Azalea viscosa, with a white flower, is a 
low shrub, arising with several stems to the 
height of two or tliree feet. The leaves come 
out in clusters without any order at the end 
of the shoots, and their edges are set with 
very short teeth, which are rough. The 
flowers come out in clusters between the 
leaves, have much the appearance of honey- 
suckle, and are as well scented. 
3. Azalea Pontica, a native of Pontus, lias 
large and beautiful yellow flowers, very fra- 
grant. 
Of the nudiflora there are also some beau- 
tiful varieties, particularly the scarlet and the 
orange. In short, there has not been a 
greater accession to our gardens than these 
truly elegant shrubs. They will only thrive 
in bog-earth, and are chiefly propagated by 
layers, as the finer roots seldom ripen seeds 
in England. They must be removed with a 
dump of earth, as disturbing the fibres de- 
stroys them. 
AZIMUTH, in astronomy, an arch of the 
horizon, intercepted between the meridian of 
the place and the azimuth, or vertical circle 
passing through the centre of the object, 
which is equal to the angle of the zenith form- 
ed by the meridian and vertical circle; or it 
is found by this proportion ; As the radius, to 
the tangent of the latitude of the place, so is 
the tangent of the sun’s or star’s altitude, for 
instance, to the co-sine of the azimuth from 
the south, at the time of the equinox. To 
find the azimuth by the globe, see the article 
Globe. 
Azimuth, magnetical, an arch of the ho- 
rizon intercepted between the azimuth, or 
vertical circle passing through the centre of 
any heavenly body, and the magnetical me- 
ridian. This is found by r observing the object 
with an azimuth compass. 
Azimuth compass , an instrument adapted 
to find, in a more accurate manner than by 
the common sea-compass, the sun’s or star’s 
magnetical amplitude, or azimuth.. 
Azimuth dial, one whose style or gnomon 
is at right angles to the plane of the horizon. 
Azimuth circles, called azimuths, or ver- 
tical circles, are great circles of the sphere, 
intersecting each other in the zenith and na- 
dir, and cutting the horizon at right angles in 
all the points thereof. The horizon being 
divided into 360°, they usually conceive 360 
azimuths. These azimuths are represented 
by the rhumbs on common sea-charts, and 
on the globe they are represented by the 
quadrant of altitude when screwed in the ze- 
nith. On these azimuths is reckoned the 
height of the stars, and of the sun, when not 
in the meridian. 
AZOGA ships, Spanish ships, commonly 
called the quicksilver ships, from their carry - 
ing quicksilver to the Spanish West Indies, 
in order to extract the silver out of the mines 
of Mexico and Peru. These ships, strictly 
speaking, are not to carry any goods unless 
for the king of Spain’s account; but by pro- 
curing special licences, they are enabled to 
take in a full cargo for merchants, as well as 
the sovereign. 
AZOOPHAGUS, a term used by authors 
to express such animals and insects as never 
eat the flesh of any creature that has had life. 
AZOTE, or nitrogen, in chemistry, a sub ' 
stance hitherto considered as elementary, ex- 
isting abundantly in nature, forming full 
three-fourths ot the atmosphere. It is a pe- 
culiar and almost characteristic ingredient of 
animal matter, the basis of nitric acid, and 
one ot the constituents of volatile alkali. Pure 
azote is known only in the form of gas ; it is 
then synonimous with the phlogisticated air 
ot Scheele and Priestley, the atmospherical 
mephitis of Lavoisier, and the nitrogen gas of 
Ghaptal. 
Azote may be procured by the following 
processes. It a quantity of iron filings and 
sulphur, mixed together, and moistened with 
water, is put into a glass vessel full of air, it 
will absorb all the oxygen in the Course of a 
tew r days ; but a considerable residuum oi air 
will still remain incapable of any farther di- 
minution. T his residuum has obtained the 
appellation of azotic gas. T here are other 
methods of obtaining it more speedily. If 
phosphorus, for instance, is substituted for 
the iron filings and sulphur, the absorption i< 
completed in less than 24 hours. The fol- 
lowing method, first pointed out by Ber- 
thollet, furnishes very pure azotic gasj if the 
proper precautions are attended to. Very 
much diluted aqua fortis, or nitrous acid, as ib- 
is called in chemistry, is poured upon a piece 
of muscular flesh, and a heat of about 100 *' 
applied. A considerable quantity of azotic 
gas is emitted,, which may be received in 
proper vessels. 
The air of the atmosphere contains about 
0.78 parts (in bulk) of azotic gas; almost all 
the rest of it is oxygen gas. Mr. Lavoisier 
was the first philosopher who published this* 
analysis, and who made azotic gas known as a 
component part or air. ITis experiments 
were published in 1774, or perhaps rather 
1775. Scheele undoubtedly wasacquainted 
as early with the composition of air; but ids 
Treatise on Eire, in which that analysis is 
contained, was not published till j 777. 
Mr. Kirvvan examined the specific gravity 
of azotic gas obtained by Scheele’s process''; 
it was 0.00120; it is therefore somewhat- 
lighter than atmospheric air; it is to atmo- 
spheric air as 985 to 1000. According to the 
experiments of Lavoisier, its specific gravity 
is only 0.00115, or it is to common air as 
942.6 to 1000. 
T his gas is invisible and elastic, like com- 
mon air; and like it too, capable of indefinite 
condensation and dilation. It is exceedinoly 
noxious to animals; if obliged to respire^it, 
they drop down dead almost instantly. No 
combustible will burn in it. Hence the rea- 
son why a candle is extinguished in atmo- 
spherical air as soon as the oxygen near it is 
consumed. 
oxygen. I ake a glass tube, the diameter of 
wflich is about the sixth part of an incli ; shut 
one of its ends with a cork, through the 
middie of which passes a small wire with a 
ball of metal at each. end. Fill the tube with 
mercury, and then plunge its open end into a 
bason of that fluid. Throw up into the tube 
as much ot a mixture, composed of J 3 parts, 
of azotic and 87 parts of oxygen gas, as will 
fill three inches. Through this gas make 
by means of the wire in the cork, a number 
ot electric explosions pass. The volume of 
gas gradually diminishes, and in its place 
there is found a quantity of- nitric acid. T his 
