THE 



BRITISH ENCYCLOPEDIA 



ABA 



4 The first letter of the alphabet, and 

 * * one of the five vowels, is pronounc- 

 ed variously ; sometimes open, as in the 

 words talk, ~i\il!c ; and at others close, as 

 in talci; -icatci' 



A is also used, on many occasions, as a 

 ftharncter, mark, or abbreviation. Thus, 

 in tin- calendar 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, 

 , or aa, among- physicians, denote ana, or 

 an equal weight, or quantity, of several 

 Ingredients. 



\ \M, <>r HUM, 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 tin- 

 ship's course. They are laid aback, to 

 ofh'-ct an immediate retreat, without turn- 

 ing either to the right or left, to avoid 

 some immediate danger in a narrow 

 channel, or when she baa advanced be- 

 yond her station in the line of battle. 



ABACUS, in architecture, the upper- 

 most member of the capital of a column. 

 In tlie (Jrcck Doric, it is a plane square 

 fillet. In the Ionic, and Corinthian, 

 moulded and enriched. 



A n AC is, among ancient mathemati- 

 cians, was a table strewed over u ith.dust, 

 r sand, on which they drew ihcir figures 

 er schemes. 



ABACI'S, in arithmetic, a-i instrument 

 for facilitating operations by means of 

 counters. Its t'orm i-; v.irioio*: but that 



VOL fc 



ABA 



chiefly used in Europe is made by dva\\ 

 ing parallel lines, distant from each other 

 at least twice the diameter of a counter; 

 which, placed on the Io.wermost 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 tiie half of 

 what it would do on the ncxtsuperior line. 



ABACTS, pythoforicv, a multiplication - 

 table, or a table of number* ready cast up. 

 to faciii'.aV- operations in Arithmetic. 



AH AITS, I'i'fiitticiiXi is a)so a kind of mul- 

 tiplication-table, in forai of a right-angled 

 triangle. 



An AC t,8, harmanicns, among musicians, 

 denotes the arrangement of the keys of a 

 musical instrument. 



AB.UTS, Grecian, an oblong frame, over 

 which arestretchedscver.il brass \\ins, 

 strung with little ivory halls. 

 ons arrangements of which all kinds of 

 computations are easily m.. 



Ami , or Schwan pan, consists 



l.f S' Acl-al S' >i|o- ( , n |)ra is 



wires, stretched from the- '.op to the bot- 

 tom of the instrument, and divided in the 

 middle by a cross piece from si.k- to side. 

 In the upper space every string has two 

 beads, which a i-r each co-intcd for five; 

 and in the lowest space every .it ring h:v> 

 five beads, of ditti-ren' the first 



being counted as 1, the second as 10, the 

 third as loO, and so on. 



ABAFT, in tge, 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-must, when , 

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

 the stem. 



AiiM-f> h-tt.ji, denotes the relative 

 situation of any object wah the ship, when 

 the object is placed in any part of that 



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