•RAD 



the generic cliarafler and name, as well as in his reference to 

 Linnxus. Tlio ralyx is many-cleft, not compofi-d of four 

 diftini't leaves; the plant has hardly any thing of the afped't 

 of a I.inum, and therefore cannot properly be called ImrAtles ; 

 neither has it been publiflied as a genus, under the name 

 of Radiola, by Linnxus, as Gmclin's reference to tlie i2th 

 edition of Sylt. Nat. indicates. 



RADIOMETER, a name which fome writers give to 

 ihe radhis ajlronomicui, or Jacob's llaff. See Fore-stakf. 



RADISH, in TJo/anj'. (See Rapha.vus.) The radifh 

 is much grown, according to the author of the Agricul- 

 tural Survey of the County of Kent, on the bell rich loamy 

 foils of the Ide of Thanet, and in Eaft Kent, for the fupply 

 of the London feedfmen. The forts ulually cultivated for 

 this ufe are, the early fhort top, the falraon, and the turnip- 

 rooted radilh. 



The land for the growth of this fort of crop (hould be in 

 a fine ftate of preparation, by benig ploughed to a great 

 depth in the early part of the winter, and broken well down 

 by harrowing, fo as to render it perfeftly clean from weeds, 

 being previoufly tilled with well reduced manure. The 

 ground being brought into this tine condition, the feed is 

 fown on furrows about ten inches apart, in a dry time in the 

 month of March, about two or three gallons per acre. And 

 as foon as the plants appear, every other row is cut up with 

 a horfe-hoe, leaving the rows twenty inches apart. When 

 the plants get two or three rough leaves, they are hoed out 

 in rows, and are then kept clean by repeated horfe and hand- 

 hoeing, when necefl'ary, leaving the plants at about eighteen 

 inches diftance. It is added, in the above Report, that the 

 crop is (eldom fit to reap till October, and fometimes is out 

 in the fields till Chriilmas, without receiving injury from wet 

 weather ; it being neceffary that it fliould have much rain to 

 rot the pods, that it may thrafh well. In refpeft to the 

 produce, it is from eight to twenty-four bufiiels /><■>■ acre : 

 and it is fold to the London feedfmen, who fend it to all 

 parts of the kingdom for retailing to the gardeners. 



It is probable that this fort of crop might be grown in 

 many other diltridts near the metropolis, or other large 

 towns, with equal fuccefs, where the foil is of a rich loamy 

 nature, as it is very eafy in its culture, and requires but 

 little labour or trouble. As it is neceflary for it to remain 

 out fuch a length of time, however, it will be proper, 

 efpecially in wet feafons, to keep the Hems from falling 

 too much upon the ground, as they ami tlie feed may be 

 injured by being too much in contatl with it. If kept up 

 in this way, the Italks, feed-hutks, and other oflal parts, may 

 alfo form a good cut food for fome forts of live-ftock, as is 

 the cafe with fome other fimilar forts of crops. 



Radish, Horfe. See Cochleakia Armoracla, 

 • RADIUS, in yfnatomy, that bone of the fore-arm which 

 extends from the humerus to the wriil, in the line carried 

 from the external condyle of the former bone to the thumb. 

 See Extremities. 



Radius, Dlflocntlons mid FraSures of. See Frac- 

 ture and Luxation. 



Radius, in Botany and Vegetable Phfjiology, means the 

 aggregate marginal florets, ot compound flowers, each gene- 

 rally of an oblong form, and all fpreading from the centre, 

 or difl^, like rays. Such are the white florets of the Daify, 

 and blue, purple or red ones, for the moit part, of the jijhr. 

 The ufual fhape of the limb or border of fuch florets is ligu- 

 late ; either linear, or elliptical ; rarely, as in Achillea, Ihort 

 and roitiidifli ; the extremity having three or five teeth. In 

 fome compound flowers the radius confifts of tubular florets, 

 as in Centaurea ; and thofe are neuter, defliitute of organs of 

 frutlitication. The hgulate radiant florets above-mentioned 



RAD 



are either female, producing perfect feed ; or they are abor- 

 tive, with more or lefs imperfedt traces of a piftil. Many 

 of them have no figns of a Ryk- or iligma, but none is without 

 fo much of a germen, as ferves for the bafis, tliat fupports 

 the petal itfelf: 



A radius is occafionally alTumed by fome flowers, natu- 

 rally deltitute of one, as in the genus Bidcni, each fpecies 

 of which, by fuch an acquifition, becomes a Cweopfti, and 

 changes its order in the Syngenefia, from Polygamia 4tqimlu, 

 to P. fuperjlua. Tin's change is an approach towards a 

 double flower, in that clafs ; being a transformation of 

 a certain number of the perfect, or united, florets into female 

 ones. If fuch a transformation be total, and all the tubular 

 florets become ligulate, the whole flower is double, and un- 

 produftive of feed, like the double Chamomile. 



Radius, Ray, in Geometry, the femidiameter of a circle- 

 or a right line drawn from the centre to the circumference. 



The word is derived from the Greek ^'a'5'oc,-, rod. Fleta 

 ufes the word radius, for a furrow. 



The radius is alfo called, efpecially in trigonometry, /7n«j- 

 tolus ; the whole line. 



It is implied in the definition of a circle, and it is apparent 

 from its coiiltrudion, that all the radii of the fame circle 

 are equal. 



Radius, in the Higher Geometry, Radius of the evolule, 

 Radius curvedinis, or Radius ofculi, called alfo the radius of 

 concavity and the radius of curvature, is a right line repre- 

 fenting a thread, by whofe evolution from off the curve on 

 which it was wound, the curve is formed ; or it is the 

 radius of a circle that has the fame curvature in a given 

 point of a curve with that of the curve in that point. See 

 Curvature and Evolute, under which articles the me- 

 thod of finding this radius may be feen. 



Radius Ajlronomicus, an inltrument ufually called Jacob's 

 ilaff^, the crofs-ilaff, or fore-ftaff. 

 Radius, in Optics. See Ray. 



Radius, in Mechanics, is applied to the fpokes of a wheel; 

 becaufe ifluing like rays from its centre. 



Radius VeSor, is alfo ufed for a right line drawn from 

 the centre of force in any curve in which a body is fup- 

 pofed to move by a eentripetal force, to that point of the 

 curve where the body is fuppofed to be. See Central 

 Force. 



Radius, among the Romans, a name given to the iron 

 rod with which tlie boys rolled the trochus. 



Radius Articulatus, in Natural Hijlory, a name given by 

 Mellius, Gmelin, and fome other authors, to a kind of 

 figured foflils, of which there are a great many very different 

 fpecies, fome of which have been defcribed by authors 

 among the belemnitje, under the names of alveoli bclemni- 

 tarum. Mr. Gmelin, who has taken great pains to inform 

 himfelf, as well of the nature and figure of thefe Hones, 

 from the fubjefts themfelves, as of their hitlory, and the 

 various accounts of them from other authors, obferves, that 

 the place where they are moft frequent is Sweden, and that 

 there they are no where fo common as in the ifle of Oeland. 

 Volkman figures fome alfo which he found in Silefia, and 

 Helwing others which he collected in Pruflia : he alfo 

 found great numbers of them himfelf in Ruflia. 



They are ufually immerfed in hme-ltone, and though at 

 firll fight they may all appear alike, yet, on a careful exami- 

 nation, they will be found to differ very greatly. The 

 molt obvious general diltindtion, ellabliflied by Gmelin, is 

 tkat fome of them are. itraight, and others crooked. The 

 ftraight ones may be divided into two genera. The firft 

 of thefe comprehend, according to this gentleman, two 

 fpecks ; the firlt imooth, and with a converging alveolus. 



The 



