LOG 



or ftone, or elfe conftrufted with wooden frames, (Tieathed 

 on the oiitfide with boards. 



LOGIC, the ?rt of thinkincf ji'^')' > "'' "^ making a 

 right nff of our rational faciihics, in defining, dividing, and 

 reafoning : or, as it is defined by an excellent writer on 

 this fubjeft, logic is the art of ufing rcafon well in our en- 

 quiries after truth, and the communication of it to others. 

 Watts. 



The word is Greek, Aoyix)!, derived from Xiyoc, fermo, 

 difcourji ; in regard thinking is only an inward, mental dif- 

 courfe, wherein tlie mind converfes with itfelf. 



Logic is alfo fometimes called dla'eSka ; and fometinies 

 the canonical art, as being a canon, or rule for direfting us 

 in our reafonings. 



As, in order to think aright, it is neceflary that we 

 apprehend, judge, difcourfe, and difpofe, or methodize, 

 rightly : hence perception or apprehenlion, judgment, dif- 

 courle or reafoning, and difpofition, whence rcfults method, 

 become the four fundamental articles of this art ; and it is 

 Irom our refleftions on thofe operations of the mind that 

 logic is, or ought to be, wholly drawn. 



Lord Bacon divides logic into four branches, according 

 to the ends propofed in each : for a man reafons, either to 

 find what he feeks, or to judge of what he finds, or to 

 retain what he judges, or to teach what he retains ; whence 

 arife fo many arts of reafoning ; ik's. the art of tnquifi- 

 llon, or invention ; the art oi examining, or judgment; the 

 art of prefer'v'mg, or of memory ; and the art of elocution, 

 or delivery. 



Logic, having being extremely abufed, is now in fome 

 difrepute. The fchools have fo clogged it with barbarous 

 terms and phrafcs, and have run it out fo much into dry 

 ufelefs fubtleties, that it fcems rather intended to exercife 

 the mind in wrangling and dilputation than to aflift it in 

 thinking juftly. It is true, in its original, it was rather in- 

 tended as the art of cavilling than of reafoning; the Greeks, 

 among whom it had its rife, being a people who piqued 

 themfelves mightily upon their being able to X.3[^ extempore ; 

 and to argue, by turns, on either fide of the quellion. — 

 Hence their dialedlici, to be always furnifhed with arms for 

 fuch rencontres, invented a fet of words and terms, rather 

 than rules and reafons, fitted for the ufe of contention and 

 difpute. 



Logic, then, was only an art of words, which frequently 

 had no meaning, but ferved well enough to hide ignorance 

 inftead of improving knowledtje ; to baffle reafon inftead of 

 affifting it ; and to confound the truth inilead of clearing it. 

 Much of that heaj) of words, and rules, which we ha\e 

 borrowed from the old logic, is of little ufe in life ; and is 

 fo far out of the common ufage, that the mind does not at- 

 tend to them without trouble : and finding nothing in them 

 to reward its attention, it foon difcharges itfelf, and lofes 

 all ideas it had conceived of them. 



But logic, difengriged from the jargon of the fchools, 

 and reduced into a clear and intelligible method, is the art 

 of condufthig the underftanding in the knowledge of things, 

 and the difcovery of truth. 



From its proper ufe we gain feveral very coniaJerable ad- 

 vantages : for, I. The confideration of rules incites the 

 mind to a clofer attention and application in thinking : fo 

 that we hereby become afured, ttiat we make the belt ufe 

 of our faculties. 2. Wc hereby more eafily and accurately 

 difcover and find out the errors and defetls in our reafoning j 

 for the common hght of reafon, unaffiftcd by logic, fre- 

 quently obferves an argumentation to be faillty, without 

 being able to determine wherein the precile failure confdls. 

 5. By tbefe refic£Uons on the order and manner of tlie ope- 



LOG 



rations of the mind, we are brought to a more jufl and 

 complete knowledge of the nature of our own underftand- 

 ing. See Soul and UNDEnsTANniNO^ 

 LOGICAL CoNX'REi E. See Concrete. 

 Logical Part. See Pakt: 



LOGINOV, in Geography,^ towrt of RufTia, in the 

 government of Tobolfli, on the Irtifch ; 16 miles S.E. of 

 'J'ara. 



LOGISTA, the title of an officer at Athens, whcfe 

 bulinels was to receive and pafs the accounts of magillrates 

 when they came out of their office. 



The logiiliE were in number ten ; they were defied by 

 lot, and had ten euthyni, or auditors of account?, under 

 them. 



LOGISTIC, or Logarithmic Linr, a curve fo called, 

 from its properties and ufe.i, in conftrufting and explaining 

 the nature of logarithms. 



If the right line A X {Plate XI. Anahfn, fg. 4.) be 

 divided into any number of equal parts, and to the points 

 of "thofe divifions, A, P, p. Sec. be drawn lines continually 

 proportional, the points N, M, m, Sec. form the logiftic 

 or logarithmic line or curve. 



Here the abfcilTas A P, A p, Sec. are the logarithms of 

 the femiordinates P M, p m, &.c. 



Hence, if A P = .v, A/ = ^^ V M = y, p m = a., and 

 the logarithms of y and z =:i I y and I z; .v will be = I y, and 

 V ^ Iz; confequently .v : -u = /_y : /z.; that is, the denomi- 

 nators of the ratios A N : P M, and A'N : pm, are to one 

 another as the abfciffas A P and A p. 



Hence it follows, that there may be infinite other logiftic 

 lines invented: provided .v m : v m : •.ly:lz., that any oi" 

 the roots, or powers, may be the logarithms of the femior- 

 dinates. The logillic will never concur with the axis, 

 except at an infinite dillanee ; fo that A X is its afymptote. 

 See Logarithmic Curve. 



LOGI.STIC, Quadrature of the. See QuADRATlTRE. 

 Logistic, or Logarithmic fp'iral, a line whofe conflru<5tion 

 is as follows : Divide the quadrant of a circle into any 

 number of equal part?, in the points N, n. n, &c. {Plate ji.1. 

 Anahfis^ Jig. 5.) and from the radii C N, C Sj C n, &c. 

 cut off C M, C m, C m, &c. continually proportional, the 

 points M, m, m, &c. form the logiilic fpiral. 



The arcs, therefore, A N, A n, &c. are the logarithms 

 of the ordinates C M, C m, &c. whence alfo it follows, 

 that tliere may be infinite logiftic fpirais. See SriRAL. 



LOGISTICA, or Logistical Arithmetic, a denomina- 

 tion fometimes given to the arithmetic of fexagelimal frac- 

 tions, ufed by aftronomers in tlieir calculations. 



It was fo called from a Greek Treatife of one Barlaamus 

 Monachus, who wrote about fexagefimal multiphcation very 

 accurately ; and intitled his book Aofinii- This autiior 

 VofTuis places about the year 135c, but he miftakes the 

 work for a treatife of Algebra. 



Shakerly, in his Tabulae Britannlcse, has a table of loga- 

 rithms adapted to the fexagefimal fradtions ; which, there- 

 fore, he calls logiftical logarithms ; and the expeditious 

 arithmetic of th?m, which is by this means obtained, and 

 by which all tlie trouble of multiplication and divifion is 

 faved, he calls logiftical arithmetic. 



LOGOGRAPHI, Ao)crj>^fo., among the Ancients, were 

 the fecretaries of the logiftx, and kept an account of the 

 public revenues. 



LOGOGRAPHY, derived from ?.oyof, luori, and y^aijaj^. 

 / lurite, a now mode of printing, in which the types cor- 

 refpond to whole words, and not, according to the ufual 

 method, to fingle letters. For this mode of printing a 

 patent r/as obtained fome years ago, and in the year 17 S3 



1. the 



