CIR 



CIR 



CINE'NCHYMA {kiv€(o, to move, 

 efxvfxa, infusion). A botanical term ap- 

 plied to the laticiferous tissue in plants, 

 distinguished by its irregular branching 

 and anastomozing character. 



CI'NGULUM. lAtexAWy, a girdle. In 

 Zoology, the neck of a tooth. The term 

 cingula denotes the transverse series of 

 bony pieces connected by flexible joints, 

 as in the armour of the armadillo. 



CI'NNABAR. Sulphuret of mercury ; 

 the common ore of mercury, sometimes 

 occurring crystallized as a beautiful ver- 

 milion. 



CINNAMON STONE. A silicate of 

 lime, alumina, and oxide of iron, brought 

 from Ceylon, and named from its colour. 



CI'NNAMYL. The hypothetical radi- 

 cal of the essence of cinnamon and of 

 cinnamic acid — an acid formed by the 

 oxidation of the essence of cinnamon in 

 air. 



CINNY'RIDiE. The Sun-birds; a 

 family of the Insessores, or Perchers, 

 named from the genus cinnyris, closely 

 allied to the Trochilidae, or Humming- 

 birds, which they represent in the Eastern 

 Continent. See Tenuirostres. 



CI'PHER {sifr, Arabic). A term sig- 

 nifying empty, and used as a substantive 

 to denote the figure 0. 



CI'POLIN. A green piarble with white 

 zones, brought from Rome. 



CI'RCINATE {circino, to make a 

 circle). Rolled inwards, or spirally down- 

 wards, from the point to the base, as the 

 aestivation of certain plants, the deve- 

 lopment of the young fronds of ferns, the 

 inflorescence of Boraginaceous plants, 

 &c. 



CI'RCINUS. The Compasses; a mo- 

 dern constellation, consisting of four 

 stars, not very far from the South Pole. 



CIRCLE {circulus, dim, of circus, a 

 ring). A plane figure contained by one 

 line, which is called the circumference, 

 and such that all straight lines drawn 

 from a certain point within the figure to 

 the circumference are equal to one an- 

 other; this point is called the centre of 

 the circle, and the straight lines, radii, 

 or rays. 



1. Circles, Arctic and Antarctic. Circles 

 supposed to be drawn round the Arctic 

 and the Antarctic pole, at the distance of 

 about 23^ degrees. On the terrestrial 

 globe these circles surround what are 

 called the two frozen zones, or girdles of 

 the earth. 



2. Circle, Astronomical. A term usually 

 applied to an astronomical instrument, of 



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which the sole or principal use is the 

 measurement of angles of altitude, or 

 zenith distance. 



3. Circles, Co-ordinate. Two circles at 

 right angles to each otlier ; or two circles, 

 one of which passes through the pole of 

 the other. By reference to two such 

 circles a point in the sphere is deter- 

 mined: e.g., on the earth, by determin- 

 ing the longitude and latitude; in the 

 starry heavens, by the right ascension 

 and declination; in the visible hemi- 

 sphere, by the azimuth and altitude. 



4. Circles, Concentric. Circles which 

 have the same centre, the one surround- 

 ing the other, as with a ring. Circles 

 which are wholly or partially surrounded 

 by another, but have different centres, 

 are termed eccentric. 



5. Circle of Declination. A circle on 

 which declination is measured, i. e. a 

 horary circle passing through the poles. 

 According to some writers on Astronomy, 

 the term denotes a parallel of any declina- 

 tion, or the small circle, all of whose 

 points have the same declination; that 

 is, a parallel to the equator. 



6. Circles, Tropical. Circles drawn 

 parallel to the equator through the sol- 

 stices. 



7. Circle of Illumination. That imagi- 

 nary circle which divides the enlightened 

 hemisphere of the earth from the dark- 

 ened hemisphere. 



8. Circles of the Sphere. Circles whose 

 planes pass through the sphere, and have 

 their circumference upon its surface. If 

 the plane pass through the centre of the 

 sphere, it is called a great circle : if not, 

 it is called a less circle. The equator and 

 ecliptic are great circles ; the polar circles 

 and the parallels of latitude or declina- 

 tion, are small circles. 



9. Circles of Perpetual Apparition. 

 Small circles parallel to the equator, and 

 touching the horizon of any given place. 



10. Circles of Perpetual Occultation. 

 Small circles parallel to the equator, and 

 touching the lower part of the horizon, 

 or never appearing above it. 



11. Circles of Position. Great circles 

 of the sphere, passing through the com- 

 mon intersection of the meridian and 

 horizon, and through any degree of the 

 ecliptic, or centre of a star or planet. 



CI'RCULAR PARTS. The name given 

 to Napier's proposition in Trigonometry, 

 which generalizes the relations between 

 the parts of a spherical right-angled tri- 

 angle under two formulae. 



CIRCULAR VELOCITY. The velo- 



