CIR 



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CIR 



The name has also been given to an ad- 

 mixture of letters, as the initials of a 

 name, engraved on a seal, plate, &c., so 

 as to have an enigmatical appearance. 

 These are plentiful on ancient tombs, 

 gravestones, &c. It has also been used as 

 the name of a disguised manner of 

 writing, wherein such arbitrary charac- 

 ters are made use of as may be agreed 011 

 by two or more persons corresponding, to 

 stand for letters or words, and which cha- 

 racters are supposed to be understood 

 only by the persons agreeing to use them. 

 This kind of writing has been exten- 

 sively used in times of war, to conceal 

 from the enemy the facts contained in 

 any letters which they might intercept. 

 This mode of writing gave rise to another 

 art, that of deciphering, or reading letters 

 written in cipher; and hence, also, the 

 word cipher came to signify the key to 

 unravel the characters of cipher-writing. 



CIP'OLIN , an Italian marble, containing 

 a slight admixture of quartz and oxide 

 of iron. Its colour is green, with white 

 zones. Name from Ital.ei/wW/ia,ashalot. 



CIPRIN'D^;, the carp family of fishes. 

 Type, Cyprindus, Lin. ; Order, Malacopte- 

 rygii abdominales, Cuv. ; Genera, Cyprin- 

 dus, Lin. ; Cobitis, Lin. ; Anableps, Blum. 



CIRCJJA, the Enchanter's Nightshade, a 

 genus of British perennial plants. Dian- 

 dria Monogynia. Name from Circe, an 

 enchantress, supposed to have used it in 

 her magical operations. 



CIR'CLE, Lat. circuius, from circus. A 

 geometrical figure contained under one 

 line called the circumference ; and is 

 such, that all straight lines drawn from a 

 certain point within the figure called the 

 centre, to the circumference, are equal to 

 one another. Thus, in the figure, AB = 

 AC = AD. These are called radii of the 

 eircle, of which the line BD, passing 

 through the centre, is the diameter. 



The diameter of a circle is to its circum- 

 ference nearly as 1 to 8, more nearly as 7 

 to 22, more nearly as 106 to 333, more 

 nearly as 113 to 355, more nearly as 1702 

 to 5347, &c. ; or, taking the diameter as 1, 

 the circumference is 



Circle of curvature ; that circle the curva- 

 ture of which is equal to that of any 



curve at a certain point ; called also the 



circle of equi-curvatvre. Circles of the 



sphere ; such circles as cut the mundane 

 sphere, and have their circumference on 

 its surface. They are either movcable or 

 fixed. The first are those whose peri- 

 pheries are in the moveable surface, and 

 which therefore revolve with its diurnal 

 motion, as the meridians, &c. ; the latter 

 have their peripheries in the moveablo 

 surface, and do not revolve, as the ecliptic, 

 equator, and its parallels. The circles of the 

 sphere are, besides, either greater little: 

 a great circle divides it into two hemi- 

 spheres, having the same centre and dia- 

 meter with it as the horizon : a little or 

 less circle divides the sphere into two 

 unequal parts, having neither the same 

 centre nor diameter with it as the paral- 

 lels of latitude. Circles of Altitude. See 



ALMUCANTAR. Circles of declination; 



great circles intersecting each other in 

 the poles of the world. Circles of excur- 

 sion ; circles parallel to the ecliptic, and at 

 such a distance from it (usually 10) as 

 that the excursions of the planets towards 

 the poles of the ecliptic may be within 



them. Circle of illumination ; a circle 



passing through the centre of a planet 

 perpendicular to a line drawn from the 

 sun to the respective body. This is sup- 

 posed to separate the illumined part from 

 the unillumined part, which it does nearly . 



Circles of latitude ; great circles, 



called also secondaries of the ecliptic, per- 

 pendicular to the plane of the ecliptic, 

 passing through the poles thereof, and 

 through every star and planet. They are 

 so called because they serve to measure 

 the latitude of the stars, such latitude 

 being simply the arc of one of the circles 

 intercepted between the star and the 



ecliptic. Circles of longitude ; several 



lesser circles parallel to the ecliptic, dimi- 

 nishing in proportion as they recede from 

 it : on these arcs the longitude of the stars 

 is reckoned. Circle of perpetual appa- 

 rition ; one of the lesser circles parallel 

 to the equator, described by any point of 

 the sphere touching the northern point of 

 the horizon, and carried about with the 

 diurnal motion. All the stars within this 



circle never set. Circle of perpetual 



occupation ; a lesser circle parallel to the 

 equator, and containing all those stars 

 which never appear in our hemisphere. 

 The stars situated between the circles of 

 perpetual apparition and perpetual occul- 

 tation, alternately rise and set at certain 

 times. 



CIRCUIT, from Lat. circum, round. The 

 journey or progress which the judges take 

 twice every year through the counties of 

 England and Wales, to hold courts and 

 administer justice. Thus England is di- 

 vided into six circuits the Home Circuit, 

 Norfolk Circuit, Midland Circuit, Oxford 



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