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animal kingdom, having skeletons as 

 various as the forms of the animals. 

 These skeletons are sometimes external, 

 most frequently internal, often composed 

 of minute pieces symmetrically arranged, 

 or of one solid mass ; often of a thin 

 diaphanous horny consistence, or com- 

 posed of dense siliceous or calcareous 

 spicula, or of masses of carbonate with a 

 little phosphate of lime. The osseous 

 parts in these classes appear to be extra 

 vascular, and to grow by the juxta-position 

 of new portions, and from the simplicity 

 of the general structure and functions of 

 these animals, and from the internal situa- 

 tion of their solid parts, they are not 

 exuviable. 



RA'DIATE. In botany, a corolla consisting 

 of a disk, in which the corollets are tubu- 

 lar and regular, and of a ray, in which 

 the florets are irregular. 



RA'DIATED. (radiatus, Lat.) 



1. Adorned with rays. 



2. Belonging to the division Radiata. 

 The radiated animals are among the most 

 frequent organic remains in the transition 

 strata ; many of the strata appear almost 

 entirely composed of their mineralized 

 exuviae ; but generally in a fractured 

 condition. Radiated animals comprise all 

 those which were formerly called zoo- 

 phytes, or animal plants, as the corallines, 

 &c. ; which were long mistaken for ma- 

 rine vegetables. 



3. In mineralogy, when the fibres are 

 broad and flat, and diverging as from a 

 centre. 



RA'DIATED IRON PYRI'TES. A variety of 

 sulphuret of iron of a pale bronze yellow, 

 more or less inclining to steel-grey, or to 

 brass-yellow. It occurs regularly crys- 

 tallized ; in radiated, granular, and 

 lamellar concretions. But more fre- 

 quently its form is globular, botryoidal, 

 reniform, tuberose, &c. Its surface is 

 often rough, and sometimes presents the 

 solid angles of octahedral crystals. Lustre 

 varies from glistening to glimmering, and 

 is metallic. It is easily frangible. When 

 its form is spherical, the fibres diverge 

 from the centre ; when nearly cylindrical, 

 from the axis. Its constituents are iron 

 46-03, sulphur 53'97. It occurs more 

 particularly in the chalk deposit. 



RADIA'TION. (radiation, Lat. radiation, 

 Fr.) 



1. Beamy lustre ; emission of rays. 



2. Divergence from a centre. 

 RADIA'TION OF HEAT. It is a general law, 



that all hot bodies throw out or radiate 

 heat in all directions, and that other 

 colder bodies placed in their neighbour- 

 hood become hot, as if they received the 

 heat so radiated. There are two modes 

 of communicating heat, by radiation, 



and by conduction ; and both these have 

 their peculiar, and, to all appearance, 

 very different laws. 



RA'DICATED. (radicatus, Lat.) In coii- 

 chology, when the shell is fixed by the 

 base, or by a byssus, to some other body. 



RA'DICAL. (from radix, Lat. a root, radi- 

 cal, Fr.) Primitive; original. In bota- 

 ny, radical leaves are such as spring from 

 the root : the dandelion is a familiar 

 example. 



RA'DICLE. (radicula, a little root, from 

 radix, Lat. radicitle, Fr.) In botany, 

 that part of the embryo which grows 

 downwards and becomes the root. The 

 primary object of vegetable structures 

 appears to be the establishment of the 

 functions of nutrition ; and we find that 

 while the plumule, bursting from its en- 

 veloping capsule, proceeds to extend itself 

 vertically upwards, at the same time, 

 slender filaments, or radicles, shoot out 

 below to form the roots. 



RA'DII VECTO'RES. Imaginary lines joining 

 the centre of the sun and the centre of a 

 planet or comet, or the centres of a planet 

 and its satellite, 



RA'DIOLITES. A genus of irregular inequi- 

 valved fossil shells obtained from that 

 part of the Pyrenees which is named 

 Les Corbieres. They are striated exter- 

 nally. The inferior valve is in the form 

 of a reversed cone ; the superior valve 

 convex. They have neither hinge nor 

 cartilage. The shell is beautifully figured 

 in Parkinson's Organic Remains. 



RA'DIUS. (radius, Lat. radius, Fr.) 



1. The semi-diameter of a circle. The 

 mean radius of the earth is intermediate 

 between the distances of the centre of the 

 earth from the pole and from the equator. 



2. One of the bones of the fore-arm, or 

 that part of the upper extremity which 

 extends from the elbow to the wrist. The 

 fore-arm contains two bones, the radius 

 and the ulna ; the radius is the smaller of 

 the two. 



RAGG. ) Called also Rowley ragg, or 



RA'GSTONE. $ Dudley basalt. A fusible 



siliceous stone, of a dark grey colour, 



occurring near Dudley. 



RA'MOSE. > (from ramus, a branch, Lat.) 



RA'MOUS. $ Branched , full of branches. 



Applied also to flowers growing on the 



branches ; to peduncles proceeding from 



a branch ; and also to leaves growing on 



branches when they differ from those on 



the stems. 



RANE'LLA. A genus of marine univalves, 

 belonging to the family Canalifera. Recent 

 ranellse are found principally in the Indian 

 seas at depths varying to eleven fathoms. 

 Some fossil species have been discovered 

 in the London clay. 

 RAPTO'RIOUS. (from rapio, Lat. to snatch.) 



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