U JU J V J5 XV a 1 A ^ 



THE 



BRITISH ENCYCLOPEDIA, 



ABA 



A The first letter of the alphabet, and 

 9 one of the five vowels, is pronounc- 

 ed variously; sometimes open, as in the 

 words talk, walk , and at others close, as 

 in take, wake. 



A is also used, on many occasions, as a 

 character, mark, or abbreviation. Thus, 

 in the calender, it is the first of the domi- 

 nical letters ; among logicians, it denotes 

 an universal affirmative proposition ; as a 

 numeral, A signified 1 among the Greeks; 

 but among the Romans, it denoted 500, 

 and with a dash over it, thus A~, 5000. A, 

 a, or aa, among physicians, denote ana, or 

 an equal weight or quantity, of several 

 ingredients. 



AAM, or HAAM, a liquid measure used 

 by the Dutch, equal to 288 pints English 

 measure. 



ABACK, in sea language, signifies the 

 situation of the sails when their surfaces 

 are flatted against the mast. They may 

 be brought aback, either by a sudden 

 change of wind, or an alteration in the 

 ship's course. They are laid aback, to 

 effect an immediate retreat, without turn- 

 ing either to the right or left, to avoid 

 some immediate danger in a narrow 

 channel, or when she has advanced be- 

 yond her station in the line of battle. 



ABACUS, in architecture, the upper- 

 most member of the capital of a column. 

 In the Greek Doric, it is a plane square 

 fillet. In the Ionic, and Corinthian, 

 moulded and enriched. 



ABACUS, among ancient mathemati- 

 cians., was a table strewed over with dust, 

 or sand, on which they drew their figures 

 or schemes. 



ABACUS, in arithmetic, an instrument 

 for facilitating operations by means of 

 counters. Its form is various ; but tbut 



VOL. I, 



ABA 



chiefly used in Europe is made by draw- 

 ing parallel lines, distant from each other 

 at least twice the diameter of a counter 5 

 which, placed on the lowermost line, sig- 

 nifies 1 ; on the second, 10 ; on the third, 

 100 : on the fourth, 1000 ; and so on. A- 

 gain, a counter, placed in the spaces be- 

 tween the lines, signifies only the half of 

 what it would do on the next superior line. 



ABACUS, pythagoricus, a multiplication- 

 table, or a table of numbers ready cast up, 

 to facilitate operations in arithmetic. 



ABACUS, logisticus, is also a kind of mul- 

 tiplication-table, in form of a right-angled 

 triangle. 



ABACUS, harmonious, among musicians, 

 denotes the arrangement of the keys of a 

 musical instrument. 



ABACUS, Grecian, an oblong frame, over 

 which are stretched several brass wires,, 

 strung with little ivory balls, by the vari- 

 ous arrangements of which all kinds of 

 computations are easily made. 



ABACUS, C%z'ne$e,orSchwanpan,consis{% 

 of several series of beads strung on brass 

 wires, stretched from the top to the bot- 

 tom of the instrument, and divided in the 

 middle by a cross piece from side to side. 

 In the upper space every string has two 

 beads, which are each counted for fivej 

 and in the lowest space every string has 

 five beads of different values, the first 

 being counted as 1, the second as 10, the 

 third as 100, and so on. 



ABAFT, in sea-language, a term appli- 

 ed to any thing situated towards the stern 

 of a vessel : thus a thing is said to be abaft 

 the fore-mast, or main-mast, when placed 

 between the fore-mast, or main-mast, and 

 the stern. 



ABAFT the beam, denotes the relative 

 situation of any object with the ship, when 

 the obiect is placed in any part of that 



A 



