Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/348

 RAD

{landing all together, make a continued canal, there has patted another Shelly 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 point- ed at the end, and like the reft divided into its concame- rations, and pierced along its middle with a fiphunculus. Mem. Acad. Pctrop. Vol. 3. p. 263.

This fhell is therefore a compages of three fhelly bodies, in- clofed one within another ; and it muft be fuppofed, in or- der to carry an analogy with other fhell-fifh, that thefe three fhelly bodies have communications with one another, by means of certain flits or perforations. The communi- cation of thefe, one with another, feems alfo evident, from their being all found in their foffile ftate, filled with the fame ftony matter ; this has, doubtlefs, been all received in at the fiphunculus of the inner fhell, and thence has been thrown into the fecond, and from this into the third fhell, 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 of the fhells. The crooked, and twifted, or wreathed kinds, which have the fiphunculus, ufually placed near the fide, greatly approach in their ftructure to fome of the cornua ammonis. RADIX (Cycl.) — Radix entrochorum, the root of the entrochi, z name given by fome authors to a foffile fubftanoe, ufually found among the entrochi, and feeming to have been the bafis from which they have grown. It is plainly a part of the Jlella ?narbia arborefcens petrified, as thofe ftones alfo are : but people, who from a proper examination of the animal world, had miffed the true origin of thefe ftones, and called them rock plants, have efteemed this part of the fifh the bulbous root of the plant. This foffil is rarely found whole, but the fragments of it are very common. When en- tire, it is about the fize of a walnut ; the top of it being flat, and in fome degree refembling the end of an entrochus, with a central hollow, but not having the leaft appearance of the rays of thofe ftones. Thefe foffils, though not pro- perly judged of as to their origin, have yet been defcribed by a great number of authors. Agricola, in particular, compares the form of them to a wheel. The body of this kind well refembles indeed the nave of a wheel, the fhape of it being conical toward one end, till you come to the top, and then a little flatted, with a hole in it. There is alfo a like hole in the oppofite broad end of the fame foffil, feeming fit for an axle to pafs through > and there are five hollow flirts, or feet, iffuing fideways, at equal dif- tances from the broad bottom, and equally carried on in the fame direction, fo as not amifs to reprefent the fpokes. 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 pafles directly over its center, 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 fhews it in the form of two eyes. Thefe radii, or fpokes, are very feldom found fo perfect as here defcribed. Lifter mentions them as being formed like crefcents at the end, which may very eafily happen from the breaking off a part of the terminating part. Phil. Tranf. N° 129.

The radix enttochorum is never of a fmooth furface, but is wrought all over with trigonal, tetragonal, pentagonal, and hexagonal plates. The ufual ftructure is this : the upper part of the conical end is wrought round with fix large hexa- gonal plates. Thefe reach half way of the ftone, then follow a fecond round made up of eleven pentagonal plates ; thefe are pretty large, and reach almoft to the broad bottom, which is a little convex. The bottom itfclf and the feet contain plates of all the fhapes, but they are ufually ver fmall. The fubftance of this foffil is always a whitifh opake fpar, of the fame nature with the trochites. It has outwardly a ruffy coat, and is blueifh within, like fmall fhells. It is generally found in clay, and is fo, filled up with it, as to appear folid ; 'but on the picking this out with a pointed inftrurnent, the whole appears to be only a hollow fhell, of about the thicknefs of a half crown piece. The fmall fcales of pentangular and other figures, which make up thefe bodies, are often found loofe in the clay where the entrochi are alfo found ; but they have fo little re- femblance to any thing of the entrochus kind, that few have thought of referring them to that foffil, till they- have met with the radix entire. There are a vaft variety of thefe plates, fome are convex, others concave; fome have edges plain and fmooth, others ferrated, and fome have, on the convex parts, the figure of a ftar, conuftingof fix embofled rays, with a ftud between every two of them, in the manner of the wires, or appendicular, growing from the afteria?, which are a fort of foffils, evidently very nearly allied to the entrochus kind in allrefpects. Radix alba, a word ufed by Diofcorides, ta exprefe the root of the dracunculus.

R A I

RADULA, the rafpatory, a chirurgical inftrurnent ufed to cleanfe foul bones.

RAERS of a cart. See the article Cart.

RAGS. In fome counties of England, particularly in Ox- fordfhire, it is a common thing to ufe old woollen rags by way of manure upon land. Taylors threads anfwer this purpofe, in fome degree ; but the old rag s of cloaths, which have been worn by men and women, are much better, which is owing to the falts they have imbibed from the perfpirati- on of the body they ufed to cover. Plot's Oxfordshire, p. 250.

KAG-bolis, in a fhip, are fuch as have jags or barbs on each fide, to keep them from flying out of the hole wherein they are driven.

Rag-^tW, a name given by our artificers to a kind of ftone, which they ufe for fetting an edge upon knives, chifels, and other tools. It is a greyifh coloured ftone, containing a large quantity of talcky particles, and fplits eafily into thin flakes. It is a foft ftone, and is ufed only to finifh the fet- ting an inftrurnent after the edge has been prepared by grinding or rubbing the tool upon fome other ftone of a coarfer texture. We have this from Newcaftle and many other parts of the north of England, where there are very large rocks of it in the hills.

RAG-uwr, jacobaa, in botany. See Jacob^ea.

There are two or three fpecies of this plant cultivated in the gardens of the curious ; and one very common in moft places, which is the maritime kind, remarkable for its white leaves. This had been long ufed to be nurfed up, with great care, in our green houfes ; but of late fome ftraggling feeds of it having propagated themfelves on a wall, and there ftood the winter's cold without hurt, we were taught that the plant did not require the care it had been ufed to be treated with.

All the kinds may be propagated by fowing their feeds m March, on a bed of light earth, watering it frequently in dry weather. In May the plants may be taken up, and planted in pots, and fet in a warm fituation till October, when the tenderer kinds are to be taken into a green-houfe. Thefe require much pruning in fummer to keep them in fhape, for they grow very faft, and in winter will die if they are not often watered. Miller's Gardners Diet. The grey, or white leaved kind, is eafily propagated by cuttings, planting them in light earth, and frequently water- ing them till they have taken root, and then the plants are to be removed into a warm fituation. This method is vaftly better in regard to this particular plant, than the raifing from feeds; becaufe, when fo raifed, it is very apt to degenerate, and lofe the whitenefs of its leaves, which are its principal beauty. SeejACOB^A.

RAHAS, in ichthyology, a name given by fome authors to the torpedo, or cramp fifh. It is a fpecies of the ray fifh, di- ftinguifhed by Artedi, by the name of the raia iota levis 3 the wholly fmooth ray. See Torpedo, Cycl.

RAIA, in the Linnaean fyftem of zoology, the name of a diftindt genus of fifties of the general order of the chondro- pterygii. The diftinguifhing characters of this genus are, that the body is flatted, and the apertures of the gills are five ' on each fide. Linnai Syft. Natur. p. 51. In the Artcdian fyftem of ichthyology, the characters of this genus of fifties are thefe. They are of the chondropterygious kind. The apertures of the bronchia are five on each fide, and are fituated on the breaft a little below the mouth. The head and the whole body are of a remarkably depreffed or flatted figure. The fides are terminated in broad fins, which are in the place of pectoral ones in other fifties, The eyes are placed in the upper fide of the head, and the mouth generally in the lower. There is on each fide of the head a foramen behind the eyes. And the tail is generally long and flcnder.

Of thofe raits which have obtufe or granulous teeth, the following are the fpecies. 1. The oblong ray with one row of fpines, along the middle of the back. This is the rhino- batus and fquatino-raia of authors. 2. The prickly ray, with teeth like tubercles, and a tranfverfe cartilage in the belly. This is the raia clavata of authors, and our thorn- back and ?naid. 3. The fmooth bodied ray, with a Ion* fpine ferrated on one fide in the tail, which has no fin. This is the pajlinacha marina of authors. 4. The fmooth bo- died ray, with generally two fpines ferrated behind in the tail, without a fin. This is the altavela of the Italians. 5. The fmooth bodied ray with a fingle long ferrated fpine in the tail, with a fin on it. This is the fifh, called by authors the a quila marina.

Of the rays with fharp teeth, the following are the known fpecies. 1. The ray with the whole back armed with fpines, with two rows of them on the tail, and a fingle row about the eyes. This is the ray called the white horfe ra\\ or raja tota afpera of authors. 2. The ray with the back and belly fmooth, but with a row of fpines about the eyes, and three rows of them upon the tail. This is the raja Icevis oculata of authors. 3. The variegated ray with two prickly tubercles on the middle of the back. This is the raja oxyrhincos major of authors. It fometimea has two fin?,

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