CEM 



CEP 



aggresrated compound rocks, which is cha- 

 racterized by the presence of numerous 

 small cavities, of a roundish, oval, or 

 other form, as in lava. 



CA'VID^. The Guinea-pig tribe; a 

 family of the JRodentia, containing the 

 largest-sized animals of the order, indi- 

 genous in tropical America, where they 

 replace the hares and rabbits of cold 

 climates) 



CAVITA'RIA {cavitas, a cavity). In- 

 testinal worms, or Entozoa, which have 

 an intestinal canal floating in a distinct 

 abdominal cavity. 



CAWK, A technical term applied to 

 opaque sulphate of baryta, or vitriolated 

 heavy spar. 



CE'BRIONITES. A family of Coleo- 

 pterous insects, of the section Malaco- 

 derma of Latreille, named from the 

 genus cebrio. 



CE'DRIRET. A substance found 

 among the products of the distillation 

 of wood. 



CE'LAPRAXITE'LLIS. A modern 

 southern constellation, consisting of six- 

 teen stars. 



CE'LESTINE (ccelum, the sky). Sul- 

 phate of strontian, so named from its 

 frequently presenting a blue colour. 



CELLA'RIAD^. The second family 

 of the Polypiaria membranacea of Blain- 

 ville, named from the genus cellaria, and 

 consisting of hydriform animals, distinct 

 from one another, contained in mem- 

 branous cellules with a bilateral opening, 

 and comprising the flustra, lunulites, &c. 



CE'LLULAR TISSUE (cellula, a little 

 cell). The elastic connecting tissue of 

 the various parts of animal and vegetable 

 bodies, consisting of cellules or vesicles 

 of various figures, adhering together in 

 masses. 



CELLULA'RES (cellula, a little cell). 

 Cellular plants ; those which consist, in 

 many cases, entirely of cells, and have 

 no flowers or spiral vessels. They are 

 also called cryptogamous and acotyledo- 

 nous plants. See Vasculares. 



CEMENT. A preparation made of 

 various materials, which is applied in a 

 soft state, and afterwards hardens and 

 unites the surfaces to which it is applied 



Roman Cemetit. A mortar made of 

 lime, and puzzolano ground to fine 

 powder. The latter substance consists 

 principally of pumice, found near Poz- 

 zuoli. 



CEMENTATION. A process by which 

 the properties of a body are changed, on 

 being surrounded with the powder of 

 72 



other bodies, and exposed to a high 

 temperature, as the conversion of iron 

 into steel, by cementation with charcoal. 

 The substance so employed is called 

 cement powder. 



CENTAURUS. The Centaur ; a south- 

 ern constellation, consisting of thirty-five 

 stars. 



CENTRAL ECLIPSES. A term ap- 

 plied to annular eclipses, because the 

 centres of the sun and of the moon ap- 

 pear to coincide. 



CENTRAL FORCES. The forces 

 which cause a moving body to tend 

 towards, or recede Irom, the centre of 

 motion. 



CENTRAL MOTION. A curvilinear 

 motion round that point of a body which 

 is called the centre of gravity, resulting 

 from the balance of the centripetal and 

 the centrifugal or tangential forces. 



CENTRI'FUGAL FORCE {centrum, 

 a centre, fuc/io, to avoid). The force by 

 which all bodies, when set in motion 

 round a centre, tend to move uniformly 

 in a straight line, and thus io fly from the 

 centre, in a tangent to the circle in which 

 they move. 



Centrifugal Evolution. Leaving the 

 centre ; a term applied to inflorescences, 

 in which the central flowers open first. 



CENTRI'PETAL FORCE {centrum, 

 a centre, peto, to seek). The force or 

 gravity by which a body tends towards 

 some point as a centre : in obedience to 

 this law all the planets are drawn to the 

 centre of their respective orbits, and all 

 bodies tend towards the centre of the 

 earth. 



Centripetal Evolution. Approaching 

 the centre ; a term applied to inflores- 

 cences, in which the marginal flowers 

 open first. 



CEPHALA'NTHIUM {Ke<pa\n, the 

 head, avOo^, a flower). A head of flowers ; 

 a designation of the inflorescence of 

 Compositae, more commonly called a 

 capitulum or anthodium. 



CE'PHALOTHO'RAX {^ecpaMj, the 

 head, Ocopa^, the thorax). The anterior 

 division of the body in spiders, scorpions, 

 &c., which consists of the head and chest 

 blended together, answering to the flrst 

 two segments of insects in a confluent 

 state. 



CEPHALO'PODA {KecpaXij, the head, 

 TToif?, 7ro5c)9, a foot). A group of mollus- 

 cous invertebrate animals, in which the 

 head is situated between the trunk and 

 the feet, or principal organs of locomo- 

 tion, as in the cuttle-fish. 



