RAD 



Gil 



RAI 



RA'DIANT. In geometry, a straight line 

 pruceea.ng from a given point or fixed 

 pole, about which it is conceived to re- 

 >oi'e. In physics, radiant heat is that 

 which is thrown off at the surface of hot 

 bodies in all directions. 



RADI A'TA. The name given to the fourth 

 pt^at division of the animal kingdom, be- 

 cause the parts of the body of the animals 

 composing it are arranged round an axis, 

 and in one or several radii or lines, ex- 

 tending from pole to pole ; whence the 

 iiumr. The division comprises five classes; 

 viz.Echinoderma,Acalepha,Polypiphera, 

 Poriphera, and Polygastrica. The Radi- 

 ata have also been termed Zoophyta or 

 Zoophytes. 



RA'DIATE, Lat. radiatus, rayed. Di- 

 verging like rays from a common centre. 

 Applied to compound flowers, in which 

 the florets of the centre differ in form from 

 those of the circumference. Example, the 

 daisy. 



RA'DIATED IRON PYRITES. A variety 

 of sulphuret of iron, which occurs regu- 

 larly crystallised, in radiated, granular, 

 and lamellar concretions, in spherical, 

 and also in cylindrical masses, with fibres 

 diverging from the centre or axis. Iron 

 46, sulphur 54. 



RA'DIATING POINT. In optics, any point 

 from which rays of light proceed. 



RAD'ICAL, from radix, a root. 1. In 

 chemistry, applied to that which is con- 

 sidered to constitute the distinguishing 

 part of an acid, by its union with the aci- 

 difying principle. Thus sulphur is the 

 radical of sulphuric acid, and nitrogen of 



the nitric acid. 2. In botany, applied 



to leaves which spring from the root, like 



those of the cowslip. 3. In philology, 



a radix, or simple underived, uncoin- 

 pounded word. 



RAD'ICAL BASS. In music, the same as 

 fundamental bass (q. v.). 



RAD'ICAL QUANTITIES. In algebra, all 

 quantities under the radical sign (q. v.). 



RAD'ICAL REFORMERS. In politics, a 

 party who desire the rooting out of abuses 

 which have crept into the government, 

 and the remodelling all our institutions. 



RAD'ICAL SIGN. The sign v placed 

 before any quantity to denote that the 

 root of that quantity is to be extracted: 

 thus, y a, and \/ a + b. 



RAD'ICANT, Lat. radicans, rooting. Ap- 

 plied in botany to stems which cling to 

 other bodies for support, and strike root 

 by means of fibres, which do not imbibe 

 nourishment. The ivy (hedera helix) is 

 an example. 



RADICA'TION, from radicate, to root. In 

 litany, the disposition of the root of a 

 plant with respect to the ascending and 

 eUiiceading caudex and the radicles. 



IA*'iCLs, Lat radicula, from radix, a 



root: a rootlet. In botany, that part of 

 the embryo which grows downwards and 

 becomes the root. 



RADIOM'ETER, from radius, rod, and 

 [Mrqov, measure: the forestaff. An in- 

 strument for taking the altitudes of the 

 celestial bodies. 



RAD'ISH. In botany, the common and 

 horse-radish belong to the genus Cochle- 

 aria; the garden-radish is the Jtaphanus 

 sativus. The water-radish is a species of 

 Sitymbrium. 



RA'DIUS (Lat.), a ray. 1. In geometry, 

 a right line, drawn or extending from 

 the centre of a circle to the periphery ; 



the semidiameter of a circle. 2. In 



mechanics, the spoke of a wheel, &c. 



3. In anatomy, a bone of the forearm, 

 which accompanies the ulna from the 

 elbow to the wrist; so named from its 

 supposed resemblance to the spoke of a 

 wheel. 4. In botany, the marginal part 

 of the corolla of compound radiate 

 flowers. Also the radii of a peduncle of 

 a compound umbel are the common 

 stalks or spokes of that umbel, and the 

 pedicelli are the stalks of the florets. 



RA'DIUS VEC'TOR. In physics, a line 

 drawn from the centre of force of any 

 curve in which a body is supposed to 

 move by centripetal force, to that point 

 of the curve where the body is supposed 

 to be. Plural, Radii vectores. 



RAF'TERS. In carpentry, pieces of tinv- 

 ber which stand in pairs on the railing- 

 piece, meet in an angle at the top, and 

 form as it were the ribs of the roof. 



RAG'BOLT. An iron pin or bolt with 

 barbs on its shank to hold it in its 

 place. 



RAGG, 1 called also Rowley Ragg, 



RAGS'TONE, j and Dudley Basalt. A 

 fusible siliceous stone, of a dark grey 

 colour, with shining crystals, and a 

 granular texture ; so named from its 

 rough fracture. It is used as whetstone, 

 and is found near Dudley. 



RAO'MAN'S ROLL. A roll or register of 

 the value of benefices in Scotland, made 

 by Ragimund, a legate of the pope, and 

 according to which the clergy were after- 

 wards taxed by the court of Rome: 

 hence the word rigmarole. 



RAG'ULED. In heraldry, a cross raguUd 

 may be best understood by calling it two 

 ragged staffs. 



RA'IA. A genus of fishes, the Rays, 

 recognised by the horizontally flattened 

 body, which resembles a disk: order 

 Chondropterygii, with fixed branchiae: 

 family Selachii, Cuv. Raia, in Latin, and 

 BoiTif and BTOS, in Greek, are the 

 ancient names. The subdivisions are the 

 Sting-ray, Spotted Torpedo, Thornback 

 Skate, &c. 



RAIL. 1. In fencct, the rails are tit 



2 B 2 



