ASY 
Astronomy is sometimes divided in books, 
with respect to its different states, into 
“ new ” and “ old.” The former refers to 
the art as it stood under Ptolemy and his 
followers, with all the apparatus of solid 
orbs, epicycles, &c. &c. By new astronomy 
is meant the science as it has been culti- 
vated since the period in which Coperni- 
cius flourished. By that great man the 
constitution of the heavens was reduced to 
more simple, natural, and certain princi- 
ples. The substance of the old astronomy 
is given by Tacquet, and of the new by 
Whiston, in his “ Prelectiones Astrono- 
mic®, published in 1707". The whole doc- 
trine, both according to the ancients and 
moderns, is explained by Mercator in his 
Iustitutiones Astron. 
Having concluded this brief sketch of a 
very important science, we shall refer to 
other articles, in which many subjects will 
be discussed, that usually find place in a 
treatise of astronomy. Under the word 
Sun will be found some interesting specula- 
tions of Dr. Herschel ; under that of Moon, 
an account of the methods of measuring its 
mountains, an explication of the harvest 
moon and horizontal moon. For equation 
of time, see Time ; see also Earth, figure 
of; Ecliptic; Equinoxes, precession of ; 
Galaxy; Gravitation; Nebulae; Sa- 
turn, ring of; Astronomy, practical ; and 
Astonomical instruments ; see Observa- 
tory; Satellites; Transit; &c. &c. 
&c. 
ASTROSCOPE, an instrument com- 
posed of two cones, having the constella- 
tions delineated on their surfaces, whereby 
the stars may be easily known. 
ASYMETRY, in a general sense, the 
want of proportion between the parts of 
any thing, being the contrary of symmetry. 
In mathematics it is used for what is 
more commonly called incommensurability, 
or the relation of two quantities which have 
no common measure, as between one and the 
. square root of two, or as 1 : y'g, or the 
side and diagonal of a square. 
ASYMPTOTE, in geometry, a line 
which continually approaches nearer to an- 
other ; but, though continued infinitely, will 
never meet with it : of these there are 
many kinds. 
The term asymptotes is appropriated to 
right lines, which approach nearer and 
nearer to some curve, of which they are said 
to be the asymptotes ; but if they and their 
curves are indefinitely continued they will 
never meet. 
Concerning asymptotes and asymptotical 
ATM 
curves, it may be remarked, 1. That al- 
though such curves as have asymptotes are 
of the number of those which do not include 
a space ; yet it is not true, on the other 
hand, that wherever we have a curve of that 
nature, we have an asymptote also. 2. Of 
these curves that have an asymptote, some 
have only one, as the conchoid, cissoid, 
and logarithmic curve ; and others two, as 
the hyperbola. 3. As a right line and a 
curve may be asymptotical to one another, 
so also may curves and curves : such are 
two parabolas, whose axes are in the same 
right line. 4. No right line can ever be an 
asymptote to a curve that is every where 
concave to that right line. 5. But a right 
line may be an asymptote to a mixed curve, 
that is partly concave, and partly convex, to- 
wards the same line. And, 6. All curves 
that have one and the same common asymp- 
tote, are also asymptotical to one another. 
See Conic. Sections. 
ASYNDETON, in grammar, a figure 
which omits the conjunctions in a sentence, 
as in that verse of Virgil. 
Ferte citi flammas, date vela, impellite 
remos. 
ATCIIIEVEMENT, in heraldry, denotes 
the arms of a person, or family, together 
with all the exterior ornaments of the shield, 
as helmet, mantle, crest, scrolls, and motto, 
with such quarterings as may have been ac- 
quired by alliances, all marshalled in order. 
ATHAMANTA, in botany, a genus of 
the Pentandria Digynia class of plants, tbs 
general corolla whereof is uniform ; the 
partial one consists of five inflexo-cordated 
unequal petals : there is no pericarpium ; the 
fruit is ovato-oblong, striated, and divisible 
into two parts ; the seeds are two, oval, 
striated, and convex on the one side, and 
plane on the other. There are 10 species. 
ATHANASIA, in botany, a genus of the 
Syngenesia Polygamia iEquulis class and or- 
der, and of the natural order of compound 
flowers. The essential character is calyx 
imbricate ; down chaffy, very short ; recep- 
tacle chaffy. There are 20 species. 
ATHEIST, is one who does not believe 
in the existence of a God. He attributes 
every thing to a fortuitous concourse of 
atoms. Plato distinguishes three sorts of 
Atheists. 1. Such as deny absolutely that 
there any gods. 2. Others who allow their 
existence, but deny that they have any con- 
cern with human affairs ; and lastly, such as 
believe in gods and a providence, but think 
they are easily appeased, and remit the 
greatest of crimes for the smallest supplica- 
