68 
A M M 
A M M 
A M I 
the oriental ones, at least some of the finer 
specimens, being so hard and bright as to 
equal any of the coloured gems in value. Hotv- 
ever, by tar the greater number of amethysts 
faii infinitely short of these, as all the European 
ones, and not a few of those brought from the- 
East and West Indies, are very little harder 
than common crystal. 
Amethyst, in heraldry, a term for the 
purple colour in the coat of a nobleman, in use 
with those who blazon by precious stones in- 
stead of metals and colours. This in a gen- 
tleman’s escutcheon is called Purpure, and in 
those of sovereign princes Mercury. 
AMERHYSTEA, a genus, of the diandria 
Bionog.ynia class and order, of the natural order 
ot verticillaue anti labial ;r. The characters are : 
the calyx consists of a single-leaved peri- 
antihum,' bell-shaped, angular, semiquinque- 
fid, and persistent: the corolla is monopeta- 
lous; the border quinquepartite, the lowest 
division more expanding: the stamina con- 
sist of two slender filaments approximated: 
the anthers are simple and roundish: the pis- 
tillum has a four-cleft germen ; stylus, the size- 
of the stamina ; stigmata two, acute : no co- 
rolla: the seeds four, gibbous, and shorter 
than the calyx. There is only one known 
species: it is a native of Siberia. It is an an- 
nual plant, with an upright stalk, which rises 
about a foot high. Towards the top it puts 
forth two or three small lateral branches, gar- 
nished with small trilid leaves, sawed on their 
edges, of a very dark, green colour. The 
flowers appear in June or July, and are pro- 
duced in small umbels at the extremities of 
the branches. They are of a line blue colour, 
as are also tiie upper part of the branches, and 
the leaves immediately under the umbel, so 
that they make a fine appearance. The seeds 
of the ametbystea should be sown in autumn, 
as they are apt to remain a whole year in the 
ground. 
AMETHYSTINE, a term applied to a 
kind of purple garment dyed of the hue of 
amethyst. This colour is a medium between 
the tyriun and hyacinthine. 
AMIABLE, or Amicable numbers, such 
as av.* mutually equal to the sum of one ano- 
ther’s aliquot parts, as the numbers 284 and 
220. Thus the aliquot parts of 220, are 1, 2, 
4, 5, 10, 11, 20,22, 44, 55, 110, and these 
a:i.led together are equal to 284 ; and the ali- 
quot parts of 284, are 1, 2, 4, 71, 142, and 
those added together are equal to 220. 
Van Schouten was the first who gave this 
name to such numbers, of Which it is easily 
apprehended, there are but very few at least 
to be set down and manageable by us; for 284 
and 220 are the two least, and the two next 
greater are 184,16 and 17296; the third, pair 
©f numbers are 9363584 and 9437056. 
A\iiANT{llJS, a fibrose, flexile, and 
elastic mineral substance, composed of short 
and abrupt figments. 
There are several species of amianthi ; that 
of a greyish green colour,, with short, abrupt, 
and interwoven filaments, isthe_same with the 
plumose alum of the shops. 
The properties of the amianthus are very 
wonderful. They will neither give fire with 
sled, nor ferment with aquafortis; and if 
thrown into the fire, will endure the most ex- 
treme heat without the least injury to their 
t xture. Amianthus threads are sometimes 
used as perpetual wicks for lamps ; they re- 
quire occasional cleaning from the- soot; and 
by great heat they are apt to run together in a 
state of semifusion, so as to prevent the due 
supply of oil. The amianthus and all the 
varieties of asbestos, are classed by Mr. Kir- 
wan among the' magnesian earths, as they con- 
tain about a fifth part of that substance. See 
Asbestos and Mineralogy. 
AMICABLE benches, in Roman an-, 
tiquity, were, according to Ritiscus, lower and 
less honourable seats allotted for the inferior 
•judges, who, upon being admitted of the em- 
peror’s council, were dignified by him with 
the title. amici. 
AM ICTUS, among ecclesiastical writers, 
the uppermost garment anciently worn by 
the clergy; the other five being the alba, sin- 
gulum, stola, manipulus, and planeta. The 
amictuswas a linen garment, of a square figure, 
covering the head, neck, and shoulders, and 
buckled, or clasped, before the breast, it is 
still worn by the religious abroad. 
AMICULUM, in Roman antiquity, a wo- 
man’s upper garment, which differed from the 
palla, as we learn from Livy ; but in what 
that difference consisted we are at a loss to 
know, unless that it was shorter than the palla. 
The amiculum was. worn both by matrons and 
courtezans. 
AMICUS curiae, a law term, to denote 
h by-stancler, who informs the court of a mat- 
ter in law. that is doubtful or mistaken. 
AMIESTl.ES, cotton cloths, which come 
from the East Indies. 
AM1RANTE, in the Spanish polity, a 
great officer of state, answering to our lord- 
high-admiral. 
AMITTERE legem terrte, among 
lawyers, a phrase importing the loss of the li- 
berty of swearing in anv court. The punish- 
ment of a champion overcome or yielding in 
battle, of jurors found guilty in a writ of 
attaint, and of a person outlawed. 
AMMAN, or Ammant, in the German 
and Belgic policy, a j udge who has the cogni- 
zance of civil causes. 
Ammant is also used among the French 
for a public notary, or officer who draws up 
instruments and deeds. 
AMM ANN I A, in botany, the name ofa ge- 
nus of plants, belonging to the tetrandria mono- 
gynia class and order of Linnaeus ; the flower of 
which is composed of four oval patent peta’s, 
growing within the cup ; and its fruit is a 
roundish capsule covered by the cup, and 
containing four cells; and this description 
forms its essential character. There are seven 
species, all of which seem to be annual, and 
being natives of hot climates most of them re- 
quire protection in this country. 
AMMI, bishop's zveed, in botany, a genus 
of umbelliferous plants, belonging to the pen- 
tandriadigynia class and order of LinUams ; the 
flower of .which is rosaceous and composed of 
heart-like petals ; and its fruit is a small round- 
ish and striated capsule, containing two striated 
seeds, convex on one side. There are three 
species, all annual. 
AMMOCHRYSOS, in natural history, the 
name of a stone common in Germany, being 
a species of mica, with gold-coloured spangles'. 
Reduced to powder, it is used to strew over 
writing. 
AMMODYTES, the name of a genus of 
fishes, of which only a single species lias 
hitherto been discovered. r l he head is com- 
pressed, narrower than the body; upper lip 
doubled, lower jaw narrow and pointed ; teeth 
sharp ; gill membrane of seven rays ; body 
long square; tail fin distinct. It inhabits the 
sandy shores of the northern seas, and it takes 
its name from its quality of diving into, or. 
burying itself under the sand. It is usually 
from nine to twelve inches in length., it is 
silvery white, and greenish on the back. 
AMMONIA, or Volatile Alkali, is 
distinguished from the fixed alkalis by a very 
sharp irritating pungent smell, and by its 
great volatility. 
Ammonia may be procured by the fol- 
lowing process : 
1. Put into a retort a mixture of three 
parts of quick lime and one part of sal am- 
moniac in powder. Plunge the beak of the 
retort below. the mouth of a glass jar tilled 
with mercury, and standing inverted in a 
bason of mercury. Apply the heal of a lamp 
to the retort ; a gas comes over, which dis- 
places the mercury and fills the jar. r J his 
gas is ammonia. It was known by the name 
of volatile alkali; it was also called hartshorn, 
because it was often obtained by distilling the 
horn of the hart ; spirit of urine, because it may 
be obtained by the same process from urine ; 
and spirit of sal ammoniac, because it may be 
obtained from that salt. Dr. Black first 
pointed out the difference between ammonia 
and carbonat of ammonia, or ammonia com- 
bined with carbonic acid ; and Dr. Priestley 
discovered the method of obtaining if in u 
state of purity, by the process already de- 
scribed. 
2. Ammonia in the state of gas is transpa- 
rent and colourless like air ; its taste is acrid, 
and caustic like that of the fixed alkalies, but 
not nearly so strong, nor does it, like them, 
corrode those animal bodies to which it is 
applied: its smell is remarkably pungent, 
though not unpleasant when -sufficiently di- 
luted. Its use as a stimulant to prevent faint- 
ing is well known. 
Animals cannot breathe it without death. 
When a lighted candle is let down into. this, 
gas, it goes out three or four times succes- 
sively; but at each time the flame is consi- 
derably enlarged by the addition. of another 
flame of a pale yellow colour, and at last 
this flame descends from the top of the vessel 
to the bottom. 
Its specific gravity is 0,000732. Its weight 
is to that of common air as 3 to 5. 
When exposed to a cold of —45° it is com 
de-hsed into a liquid, which again assumes the 
gaseous form when the temperature is raised. 
When passed through a red hot tube of 
porcelain or glass, it is totally decomposed 
and converted into hydrogen and azotic gas. 
That' this experiment may succeed, the dia- 
meter of the tube must not be too great. 
3. It combines very rapidly with wafer. 
When a piece of ice is brought into contact 
with this ga3,. it melts and absorbs the ammo- 
nia, while at the same' time its temperature is 
diminished. Cold water absorbs this gas 
almost instantaneously, and at the same time 
heat is evolved, and the specific gravity of 
the water is diminished. Water is capable 
of .absorbing and condensing more than a 
third of its weight of ammoniacal gas. The spe- 
cific gravity of the saturated solution is 0.905-4. 
It is in this state that ammonia is usually 
employed by chemists. The term ammonia, 
indeed, almost always means this liquid so- 
lution of ammonia in water. When heated 
to the temperature of about 130°, the ammo- 
