4 A B .A 
gira, in the prifon of Bagdad aforefaid: and it was not 
till 335 years after his death, that Ivfelick Schah, a fultan 
of the Selgiucidan race, built for him a magnificent mo¬ 
nument in the fame city, whereto he adjoined a College 
peculiarly appropriated to fuch as made a profeflion of this 
feci. This was in the 485th year of the Hegira, and anno 
Chridi 1092. The mod eminent fucceffors of this doflor 
were Ahmed Benali, A 1 Giaffas, and A 1 Razi, who was 
the mailer of Naffari; and there is a mofque particularly 
appropriated to them in the temple of Mecca. 
Aba, a lofty mountain of Great Armenia, part of 
mount Taurus; the rivers Euphrates and Araxes have 
their rife here; alfo a city of the ancient kingdom of Pho- 
cis in Greece, famous for an oracle of Apollo, and for a 
rich temple plundered and burnt by the Perfians. 
ABACA, one of the Philippine Iflands. 
ABACENA, the ancient name of a town in Media, and 
another of Cana in the hither Afia. 
ABACiENUM, anciently a town of Sicily, whofe ru¬ 
ins are fuppofed to be thofe lying near Trippi, a citadel on 
a high and deep mountain not far from Medina. The in¬ 
habitants were called Abacoznini. 
AB ACATUAIA,/. in ichthyology, a barbarous name 
of the zeus vomer. See Zeus. 
ABACH, a market town of Germany, in Lower Bava¬ 
ria, feated on the Danube. It is remarkable for Roman 
antiquities, and for fprings of mineral waters, which are 
faid to be good for various diltempers. E. Ion. 11. 56. 
lat. 48. 53- 
ABACINARE, or Abbacinare, f . a fpecies of pu- 
nilhment exercifed in the middle-ages, confiding in blind¬ 
ing of the criminal, by holding a hot bafon or bowl of 
metal before his eyes. 
ABACK, adv. a fea-termdenoting the fituation of the 
fails when the furfaces are flatted againfl the mads by the 
force of the wind. The fails are faid to be taken aback when 
they are brought into this fituation, either by a hidden 
change of the wind, or by an alteration in the Blip’s 
eourfe. They are laid aback , to effeCl an immediate re¬ 
treat, without turning to the right or left; or, in the fea- 
phrafe, to give the fhip Jlcrn-way , in order to avoid fome 
danger difcovered before her in a narrow channel, or when 
die has advanced beyond her dation in the line of battle, 
or otherwife. The fails are placed in this pofition by 
flackening their lee-braces, and hauling in the weather 
ones; fo that the whole effort of the wind is exerted on 
the fore part of their furface, which readily pufhes the fhip 
adern, unlefs Ate is redrained by fome counterafling force. 
It is alfo ufual to fpread fome fail aback near the Bern, as 
the mizen-top-fail, when a Blip rides with a Angle anchor 
in a road, in order to prevent her from approaching it fo 
near as to entangle the flukes with her flackened cable, and 
thereby loofen it from the ground. 
AB ACOT, f. the name of an ancient cap of date worn 
by the kings of England, the upper part whereof was in 
the form of a double crown. 
ABACTOR, f [Lat.] One who drives away or deals 
cattle in herds, or great numbers at once, in didin&ion 
from thofe that deal only a fheep or two. 
ABACUS, /. [Lat.] in arithmetic, an ancient indru- 
ment ufed by mod nations for cadingup accounts, or per¬ 
forming arithmetical calculations: it is by fome derived 
from the Greek which fignifies a cupboard or buf¬ 
fet, perhaps from the fimilarity of the form of this indru- 
ment; and by others it is derived from the Phoenician 
abak, which fignifies dud or powder, becaufe it ivas faid 
that this indrument was fometimes made of a fquare board 
or tablet, which was powdered over with fine fand or dud, 
in which were traced the figures or characters ufed in mak¬ 
ing calculations, which could thence be eafily defaced, 
and the abacus refitted for ufe. But Lucas Paciolus, in the 
fird part of his fecond diftinCtion, thinks it is a corrup¬ 
tion of Arabicus, by which he meant their Algorifm, or 
Site method of numeral computation received from them. 
ABA 
We find this indrument for computation in ufe, under 
fome variations, with mod nations, as the Greeks, Ro¬ 
mans, Germans, French, Chinefe, &c. 
The Grecian abacus was an oblong frame, over which 
were dretched feveralbrafs wires, drung with little ivory 
balls, like the beads of a necklace; by the various ar¬ 
rangements of which invention all kinds of computations 
were very eafily made. Mahudel, in Hid. Acad. R. Infer, 
t. 3. p.390. 
The Roman abacus was a little varied from the Grecian, 
having pins Aiding in grooves, indead of Brings or wires 
and beads. Philof. Tranf. No. 180. 
The Chinefe abacus, or Shwan-pan, like the Grecian, 
confids of feveral feries of beads drung on brafs wires, 
dretched from the top to the bottom of the indrument, 
and divided in the middle by a crofs piece from fide to fide. 
In the upper fpace every Bring has two beads, which are 
each counted for five; and in the lower fpace every firing 
has five beads, of different values, the fird being counted 
as one, the fecond as ten, the third as 100, and fo on, as 
with us. See Shwan-pan. 
The abacus chiefly ufed in European countries, is near¬ 
ly upon the fame principles, though the ufe of it is here 
more limited, becaufe of the arbitrary and unequal divifions 
of money, weights, and meafures, which, in China, are 
all divided in a tenfold proportion, like our fcale of com¬ 
mon numbers. This is made by drawing any number of 
parallel lines, like paper ruled for mufic, at fuch a dis¬ 
tance as may be at lead equal to twice the diameter of a 
calculus or counter. Then the value of thefe lines, and 
of the fpaces between them, increafes, from the lowed to 
the highed in a tenfold proportion. Thus, counters pla¬ 
ced upon the fird line, fignify fo many units or ones; on 
the fecond line 1 o’s, on the third line 100’s, on the fourth 
line 1000’s, and fo on : in like manner a counter placed in 
the fird fpace, between the fird and fecond line, denotes 
5, in the fecond fpace 50, in the third fpace 500, in the 
fourth fpace 5000, and foon See for example the fol¬ 
lowing figure, where the fame number, viz. 1788, is re- 
prefented in both divifions of the abacus, by different 
difpolitions of the counters: 
Befides the above indruments for computation, there 
have been feveral others invented by different perfons; as 
Napier’s rods or bones, deferibed in his Rabdologia; alfo 
the Abacus Rhabdologicus, a variation of Napier’s, which 
is deferibed in the fird volume of Machines et Inventions 
approuvees par I’Academie Royale des Sciences. An inge¬ 
nious and general one was alfo invented by Mr. Gamaliel 
Smethurd, and is deferibed in the Philof. Tranf. vol. xlvi. 
where the inventor remarks that computations by it are 
much quicker and eafier than by the pen, are lefs bur- 
thenfome to the memory, and can be performed by blind 
perfons, or in the dark as well as in the light. A very 
comprehenfive indrument of this kind was alfo contrived 
by the late learned Dr. Nicholas Saundeffon, by which 
he performed very intricate calculations: an account of 
it is prefixed to the fird volume of his Algebra, and is 
there by the editor called Palpable Arithmetic. 
Abacus, Pythagorean, fo denominated from its in¬ 
ventor, Pythagoras; a table of numbers, contrived for 
readily learning the principles of arithmetic; and was 
probably what we now call the multiplication-table. 
Abacus, or Abaciscus, in architecture, the upper 
part or member of the capital of a column; ferving as 
a crowning both to the capital and to the whole column. 
Vitruvius informs us that the abacus was originally in¬ 
tended 
