HM 
ARC 
species. A. sphyrana, or European athe- 
rine, inhabits the Mediterranean, and some- 
times wanders to the British coast, it is 
from two to four inches long ; body round 
and tapering ; back and sides, as far as the 
lateral line, pale ash mixed with green, be- 
low the line and belly fine silvery ; the air- 
bladder is conic on both sides, appearing 
as if covered with silver leaf, and is used in 
the manufacture, of artificial pearls. A. 
glossodonta, is a very elegant species found 
in the Red Sea : as is also A. machnata; but 
the other species, A. Carolina, which is the 
size of a small herring, is found in the fresh 
waters of Carolina. 
ARGENTUM vivum. See Mercury. 
ARGIL. See Alumina. 
ARGONAUT A, in natural history, a 
genus of worms, of the order Testacea. 
Animal a sepia or clio ; shell univalve, spiral, 
involute membranaceous, one-celled. There 
are five species. A. argo has the keel, or 
ridge of the shell slightly toothed on each 
side ; it inhabits the Mediterranean and 
Indian oceans, and is the famous nautilus, 
supposed in the early ages of society to 
have first taught men the use of sails. 
When it means to sail it discharges a quan- 
tity of water, by which it is made lighter 
than the sea, and rising to the surface, erects 
its arms and throws out a membrane be- 
tween them, by which means it is driven 
forwards like a vessel under sail : two of 
the arms it hangs over the shell, to serve as 
oars or a rudder. The shell is white or 
yellowish, with smooth or knotty stria: or 
ribs, which are sometimes forked ; the keel 
is generally brownish. 
ARGOPHYLLUM, in botany, a genus 
of the Pentandria Monogynia class and 
order. Calyx five-cleft, superior ; corol fivc- 
petalled ; nectary pyramidal, five-angled, as 
long as the corol ; capsule three-celled, 
many-seeded: fdundin New Caledonia, 
ARGUMENT, in rhetoric and logic, an 
inference drawn from premises, the truth 
of which is indisputable, or at least highly 
probable. 
The arguments of orators receive parti- 
cular denominations, according to the topics 
from whence they are derived ; thus, we 
meet with arguments from affection, which 
interest the passions of the person to whom 
they are addressed ; also with the argu- 
ments a tnto, ad ignaviam, ab invidia, & c. 
In reasoning, Mr. Locke observes, that 
men ordinarily use four sorts of arguments. 
The first is to allege the opinions of men, 
whose parts and learning, eminency, power, 
ARI 
or some other cause, has gained a name, 
and settled their reputation in the common 
esteem, with some kind of authority ; this 
may be called argumenturri ad verecundiam. 
Secondly, another way is to require the ad- 
versaries to admit what they allege as a 
proof, or to assign a better ; this he calls 
argumenturri ad ignorantiam. A third way 
is, to press a man with consequences, drawn 
from his own principles or concessions ; this 
is known by the name of argumentum ad 
haminem. Fourthly, the using proofs drawn 
from any of the foundations of knowledge 
or probability ; this he calls argumentum ud 
judicium ; and observes, that it is the only 
one of all the four, that brings true instruc- 
tion with it, and advances us in our way to 
knowledge. For, 1. It argues not another 
man’s opinion to be right, because I, out of 
respect, or any other consideration, but that 
of conviction, will not contradict him. 2. 
It proves not another man to be in the right 
way, nor that I ought to take the same with 
him, because I know not a better. 3. Nor 
does it follow, that another man is in the 
right way, because he has shewn me, that I 
am in the wrong : this may dispose me, 
perhaps, for the reception of truth, but 
helps me not to it ; that must come from 
proofs and arguments, and light arising from 
the nature of things themselves, not from 
my shamefacedness, ignorance, or error. 
See the articles Reason and Reasoning. 
Argument, in astronomy, denotes a 
known arch, by means of which we seek 
another one unknown. 
The argument ot the moon’s latitude is 
her distance from the node ; and the argu- 
ment of inclination is an arch of a planet’s 
orbit, intercepted between the ascending 
node and the place of the planet from the 
sun, numbered according to the succession 
of the signs. 
ARGYTHAMNIA, in botany, a genus 
of plants of the Monoecia Tetrandria class 
and order. Essen, char, male calyx four- 
leaved; petals four: female calyx five- 
leaved ; no corol ; three styles, forked ; cap- 
sule three-celled ; seeds solitary. There is 
but a single species, a shrub, found in 
Jamaica, with a whitish bark; leaves 
oval; flowers axillary, on very short pe- 
duncles. 
ARIANS, a denomination of Christians 
that take their name from Arius, a presby- 
ter of Alexandria who flourished in the 
year 315. The propagation of this doc- 
trine was the occasion of the celebrated 
council of Nice by Constantine, in the year 
