H rt ' 



as 



RIC 



d$n tea new class of animals of the lo^ cr 

 degree than the radiata, possessing a 

 power of locomotion by moans of minute 

 tentacular filaments. This class would 

 comprise the animals which construct 

 the miliola and some microscopic fora- 

 miniferous shells. 



RHO'DIUM. A metal discovered by Dr. 

 "Wollaston in crude platinum, and so 

 named from po^n, a rose, on account of 

 the rose colour of some of its compounds. 



RHODOPEN'DRON. Rose-bay : a genus 

 of permanent plants. VecandriaMono- 

 gynia. Name from pStfn, a rose, and 

 8iSjov, a tree. There are 20 species, 

 natives of temperate climates. 



RHOMB, Lat. rhombus; Gr. popSa;, 

 from ptf^Scu, to turn round. A quadri- 

 lateral plane figure, whose sides are equal 

 and parallel, two and two, and whose ad- 

 jacent angles are unequal. The opposite 

 angles are necessarily equal, and, taken 

 pair and pair, aie greater and less than 

 two right angles. AVhen all the angles 

 are equal, the figure becomes a square. 



RHOM'BOID, from pofjJZts, a rhomb, and 

 utos, likeness. A quadrilateral figure, 



whose opposite sides only are equal and 

 parallel. The adjacent sides and angles 

 are therefore unequal. The figure is 

 otherwise called a parallelogram ; and the 

 straight line which joins obliquely the 

 two opposite angles is named a diagonal. 

 AVhen the adjacent angles are equal, and 

 therefore right angles, the figure is called 

 a rectangle, and popularly an oblong. 



RHOMB-SPAR. A crystallised magnesian 

 carbonate of lime, so named from the 

 form of the crystal, of which the faces 

 are rhombs. 



RHON'CHUS. Poy^aj A rattling or 

 wheezins sound. The term is applied in 

 auscullatioii to any preternatural sound 

 accompanying respiration, occasioned 

 either by the passage of the air through 

 fluids obstructing the bronchia or air- 

 cells, or by the constriction of the 

 bronchial tubes. It is also called rattle, 

 and r It by the French writers. 



RHB'BARB. See RHB'CM. 



RHUMB, from rhomb. In navigation, a 

 vertical circle of any given placf . or the 

 intersection of a part of such circle with 

 the horizon: in this last sense rhumbs 

 coincide with the points of the compass, 

 tna are canud accordingly. 



RHIS. Sumach. A geiiu* of trees and 

 shrubs of many species. Pentandria 

 Trigynia. Name from put, to flow, be- 

 cause it stops fluxes. All the species are 

 poisonous except the S,. coriaria of the 

 south of Europe. 



RHYNCHOPH'ORA.. A family of Coleo- 

 pterous insects, distinguished by the en- 

 tire prolongation of the head, which forms 

 a sort of proboscis : whence the name 

 from pty;t*>, a beak, and Qttot, to carry - 

 The genera live chiefly on plants ; several 

 of them exclusively within their fruiis 

 and seeds, and do much injury. 



RHYNCH'OPS. A genus of birds; the 

 Skimmers: order Palmipedes: family 

 Longipennes. Name from pvy^6f, ros- 

 trum. One species only is known, the 

 Black Skimmer of the Antilles. 



RHTTH'M, Lat. rhythmus ; Qt.puBfMf, 

 metre. In music, variety in the move- 

 ment, as to quickness or slowness, or 

 length and shortness, of the notes. la 

 poetry, it is the relative duration of the 

 moments employed in pronouncing the 

 syllables of a verse. 



RIB (Saxon). 1. A bone of animal 

 bodies, forming a part of the frame of 



the thorax. 2. In ship-building, a 



piece of timber, forming part of the 

 frame-work of the side of a ship. The 

 ribs of a parrel are short pieces, having 

 holes through which are reeved the two 

 parts of the parrel rope. 3. In archi- 

 tecture and engmee.'iny, a term used gene- 

 rally to denote a girder, but more parti- 

 cularly an arched beam, sustaining tho 



superior work of a vault, bridge, &c. 



4. In botany, the continuation of the 

 petiole along the middle of a leaf, and 

 from which the veins take their rise. 



RIB'BET, dim. of rib. In architecture, 

 the recess of a wall to receive a door ot 

 window-shutter, as it folds back when 

 opened. 



RIB'BON, )Wel.-rW6m. A fillet of silk. 



RIBB'AND, I Innai-ai architecture, along, 

 narrow flexible piece of timber, nailed 

 upon the outside of the ribs, from stem 

 to stern, so as to encompass the ship 

 lengthwise: the principal are the flooi- 

 ribband and breadth-ribband. 



RI'BES. The Currant tree. A very 

 extensive genus of arborescent shrubs. 

 Pentandria Monogynia. The name ie 

 Arabic, and properly belongs to an acid- 

 leaved species of Rheum; but which 

 botanists, for 200 years past, have, by 

 mistake, applied to the currant and 

 gooseberry family, and with these it 

 now remains. The red, rock, alflne, 

 black, and spiked currants, and the 

 rouLh and smooth gooseberry, are indi- 

 gent us species. 



H CE, Fr. rii. The ROed of the Orysa 

 Mtica, It is the principal foo-i 01 UM 



2 a 



