HAD 



R A 1) 



The rofrular and nice configuration of thefe bodies fhews 

 very plainly tliat they cannot be of mineral origin ; but the 

 feveral patellie of which each is compofed, the fipliunculus 

 of communication, obvious in feveral, and the flielly matter 

 yet found remaining on many, prove them to have been 

 once (hell-fifh of the univalve or tubular concamerated kind; 

 the dofcription of which, fo far as it can be gathered from 

 thefe remains, mud have been this. The ftiell mull have 

 been either cylindric or conic in figure, of a fmooth furface, 

 and divided into feveral chambers or cells ; but this fo that 

 the fcpta which form the concamerations are not continued 

 and whole, but in feme part of the periphery are cut in, in 

 the fliape of a crefcent. Through thefe crefcents, which, 

 iUnding all together, make a continued canal, there has 

 paffed another fhelly body of a cylindric or conic figure, 

 alfo divided into concamerations, and that in fuch a manner, 

 that the fepta which form the cells are pierced with a fmall 

 aperture on one fide, which grows gradually fmaller as the 

 fhell extends in length ; and finally, through thefe aper- 

 tures, in the concamerations, there pafles another (hell pointed 

 at the end, and, like the relt, divided into its concamerations, 

 and pierces along its middle with a fiphunculus. Mem. 

 Acad. Petrop. vol. iii. p. 263. 



This (hell is, therefore, a compages of three fheHy bodies, 

 enclofed one within another ; and, it muft be fuppofed, in 

 order to carry an analogy with other (hell-fi(h, thefe three 

 (helly bodies have communication with one another, by 

 means of certain (lips or perforations. The communication 

 of thefe, one with another, feems all evident, from their 

 being all found in their folTile (late, filled with the fame (tony 

 matter ; this has, doubtlefs, been all received in at the 

 fiphunculus of the inner fhell, aod thence has been thrown 

 into the fecond, and from this into the third (hell, fo as to 

 fill up all the concamerations of the outer, as well as of the 

 inner parts. This muft have been the cafe with thefe ; and 

 the feveral various fpecics that are at this day found foffile, 

 muft have owed their origin to as many different fpecies ©f 

 the (hells. The crooked and twifted, or wreathed kinds, 

 which have the fiphunculus ufually placed near the fide, 

 greatly approach in their ftrudture to fome of the cornu 

 ammonis. 



RADIX, in Botany and Vegetable Phyfwlogy. See 

 Root. 



Radix is ufed among forae anatomifts for the fole of the 

 foot. 



Radix Carlo Sanffo ; this root is found in temperate foils, 

 in Mechoacan, a province of America. Its bark is eafily 

 feparated from it, is of an aromatic fmell, and of a bitter 

 and fomewhat acrid tafte. The root itfelf confifts of very 

 (lender fibrils, which are eafily feparated from each other. 

 The bark is accounted fudorific, and corroborates the (k)- 

 mach and gums : if chewed, it procures an agreeable breath. 

 It is good for fcurvies, catarrhs, epilepfies, haftening deli- 

 veries, and removing hernias, and the fmall-pox, if taken 

 either in powder or in the form of a decoAion. The Spa- 

 niards have called it by the name of St. Charles, on account 

 of its uncommon virtues. 



, Radix Entrochorum, the root of the entrochi, a name 

 given by fome authors to a folTile fubftance, ufually found 

 among the entrochi, and feeming to have been the bafis from 

 which they have grown. It is plainly a part of the ftella 

 marina arborefcens petrified, as thofe ftones alfo are. This 

 fodile is rarely found whole, but the fragments of it are very 

 common. When entire,' it is about the fize of a walnut ; the 

 top of it being flat, and in fome degree refembling the end of 

 anentrochus, with a central hollow, but not having the leaft 

 ;)ppearance of the rays of thofe ftones. Thefe foITils, though 



not properly judged of as to their origin, have yet been de- 

 (cribed by a great number of authors. Agricola, in particular, 

 compares the form of them to a wheel. The body of thi» 

 kind well refenibles indeed the nave of a wheel, the (Kape 

 of it being conical [toward one end, till you come to tlie 

 top, and then a little flattened, with a hole in it. There is 

 alfo a like hole in the oppofite broad end of the fame fo(ril, 

 feeming fit for an axle to pafs through ; and there are five 

 hollow (lilts, or feet, iduing fideways, at equal diftances from 

 the broad bottom, and equally carried on in the fame direc- 

 tion, fo as notamifsto reprefent the (pokes. At the end of 

 each of thefe rays or fpokes, there is a hollow, of the fame 

 nature with thofe in the middle of the common entrochi, 

 but this is cut acrofs, by a feam, or ftreak of the fame ftone, 

 which pades direftly over its centre, and covers about a third 

 part of it ; this goes no farther than the mouth of the hole, 

 but it cuts it into two, and (hews it in the form of two eyes. 

 Thefe radii or fpokes are very feldom found fo perfeft as 

 here defcribed. Lifter mentions them as being formed 

 like crefcents at the end, which may very eafily happen 

 from the breaking o(f a part of the terminating portion. 

 Phil. Tranf. N= 129. 



Radix /llba, a word ufed by Diofcordes, to exprefs the 

 root of the dracunculus. 



Radix, among Grammarians. See Radical, and Root. 



Radix, in Mathematics, the fame as root ; but ufed in a 

 different fenfe by different authors : we fay the root of an 

 equation, but the radix of a fyftem of logarithms, the ra- 

 dix of a feries, the radix of notation, &c. meaning in all 

 thefe cafes the fundamental quantity on which the fyftem is 

 conftrutted, or that whence it has been derived, or that by 

 means of which all other things of a like kind are com- 

 pared. 



Radix of a Syjlem of Logarithms, is that number which- 

 involved to the power denoted by the logarithm, is equal to 

 that number. Thus, under the article Logarith.ms it is 

 (hewn, that if r = a, then x is the logarithm of a, and r is 

 called the radix of the fyftem. This radix in the common 

 or Briggs's logarithms, is 10, and in the Neperian or hyper- 

 bolic logarithms, it is 2.71828128, &c. and generally the 

 radix of any fyftem of logarithms, is that number whofe 

 logarithm in that fyftem is unity. 



Radix of a Syjleni of Notation, is that number which in- 

 dicates the local value of the figures, and is in all fyftems 

 reprefented by a unit and cipher ( 10), which is /<?« in the 

 common fyftem, ttvo in the binary fyftem, three in the ter- 

 nary, twelve in the duodenary, and fo on. See Nota- 

 tion. 



Radix of a Series is ufed, by fome authors, as a term of 

 comparifon between any finite funftion, and its expaflfion or 

 developement : thus, the radix 



of I - 



of I - 



of I - 



of I - 



+ I 



+ 4 



4- I 



&c. is 



°^2^- 4 +"8 



16 &c. 



— -f- — &C. IS 



16 32 



of I + .r -f *r' -f- *' -f x' &C. is 



I + * 



of 



