RAVELIN 



284 



HEED 



Ravelin. 



A, ravelin ; B, bastion ; 

 C, glacis ; D, covered 



Ravelin, (rav'lin). [The French word.] 



A triangular projecting 



portion of a fortifica- 

 tion. 

 Raven, (ra'vn). [Hrcefen, 



the A.-S. name. ] = 



Corvus corax: a bird, 



usually black, belong- 

 ing to Corvidse. 

 Ray, (ra). [Radius, the 



Latin word.] A fish= 



Raia. Beaked R. = 



Rhinobatis. Eagle R.= 



Myliobatis. Electric R. 



= Torpedo. Horned R. 



=Cephaloptera. Sting 



jR.=Trygon. 

 Ray, (ra). [1. Raia, the _ 



Latin name; 2. Radius, way; E, cavalier; F, 

 the Latin word.] 1. curtain ; G, ditch. 

 =Raia, &c.: a flat fish, belonging to Elas- 

 mobranchii. 2. A line 

 of light. Ordinary R, : 

 in double refraction, 

 the ray which follows 

 the ordinary rule of re- 

 fraction. Extraordi- 

 nary R.: in double re- 

 fraction, the ray which 

 does not follow the Ray. 



ordinary rule of refraction. JR. grass=Rye, 



Ray's classification of plants 

 Flowerlesa. 

 Flowering. 



Dicotyledones. 



Monocotyledones. 



Rayed animals =Radiata, q.v. 



Rays, v. Actinic R. and Herschelian R. 



Razor, R. bill: a bird belonging to Nata- 



tores. R. shell = Solen ensis: a burrowing 



mollusc; also called Razor fish. 

 Reading, (red'ing). [R. in Berkshire.] R. 



beds, v. Woolwich and Reading beds. 

 Real, (re'al). [L. res, thing.] R. image, v. 



Image. R. focus, v. Focus. 

 Realgar, (re-al'gar). [The French word.] 



As2So=Redsulphide of arsenicum: a mineral, 



with~oblique crystallization, belonging to the 



arsenic group. 

 Reaumur's thermometer, in which the freezing 



point of water is 0" and the boiling point 80, 



the distance between being divided into 80 



equal parts or degrees. 

 Reaumuriaceae, (ro-mu-ri-a'se-e). [Reamur.] 



=Reaumuriads : shrubs, with scale-like 



leaves, belonging to Guttiferales. 

 Recent, (re'sent). \Recens, the Latin word.] 



R. rocks, with fossil shells and Mammalia, 



all of living species. 

 Receptacle, (re-sep'ta-kl). [Rcceptaculum,tl\e 



Latin word.]=Torus: the disc of the flower, 



which supports the sexiial organs. 

 Reciprocals, (re-si p'ro-klz). [L. reciproco, I 



interchange.] The quotients of the division 



of unity by a given series of numbers; e.g., J 



and are the reciprocals of 2 and 5. 

 Reckoning, v. Dead-reckoning. 



Rectangle, (rek'tang-1). 

 [L. rectus, right; Angle, 

 q. v.]= Oblong: a figure 

 formed by four straight 

 lines, all the angles be- 

 ing right angles, but 

 the opposite sides only 

 being equal. Rectangle. 



Rectangular, (rek-tang'u-lar). [Rectangle, 

 q.v.] Oblong: having the form of a rectangle. 



Rectum, (rek'tum). [L. rectus, straight.] The 

 extremity of the large intestine which opens 

 outwardly. 



Recurvirostra, (re-ker-vi-ros'tra). [L. recur- 

 vus, bent back: rostrum, beak.] A wading 

 bird, with curved beak; also called Avocet, 

 q.v. 



Red, (red). [Rad, the A.-S. word. ] R. 

 ant = Formica sanguinea. R. antimony = 

 Kermesite, q.v. R. bole: a clay coloured 

 by oxide of iron. R. breast Erythraca= 

 Robin red-breast. jR. coral, v. Coral. R. 

 crag. One of the older Pliocene beds, with 

 marine shells, found in Suffolk. R. dyes: 

 madder, alizarin, logwood, &c. R. flames, 

 v. R. prominences. R. grouse = Lagopus 

 Scoticus. R. feacl=Minium, q.v. R. ochre; 

 a variety of red haematite. R. phosphorus 

 = Amorphous phosphorus. R. pigments 

 =Ochre, bole, chrome, mercury, &c. R. 

 prominences: seen in total eclipses of the 

 sun, from 30 to 70 thousand miles in extent. 

 R. races: Andian, Pampean, Guarang, &c. 

 R. sandstone, v. Red Sandstone. R. silver 

 ore: Dark R.=Pyrargyrite; Light R. : Prous- 

 tite. R. snow=Protococcus nivali. R. stars; 

 Aldebaran, Antares, Arcturus, Fonialhaut, 

 Betelguese. R. valerian 

 = Centranthus ruber. 

 R. v&rioisBotryogen, 

 q.v. R. ?eeec2=Papaver 

 rheas=Red poppy. 



Redan, (re-dan'). [The 

 French word.] A field 

 work, shaped like a V, 

 with the apex towards Keilan. 



the enemy. 



Redoubt, (re-douf). [Redoute, the French 

 word.] A small en- 

 closed fort. 



Redruthite, (red'io- 

 thit). [Redruth, in 

 Cornwall.] A va- 

 riety of chalcocite, 

 q.v. ; an ore of cop- 

 Reducing flame of 

 blowpipe. The por- 

 tion where incom- 

 plete combustion 

 takes place, so that Redoubt, 



any oxydised substance is deprived of its 

 oxygen. 



Reduvius, (re-du-vi'us). v. Fly-bug. 



Reed, (red). [Hreod, the A.-S. name.] = 

 Phragmites, q.v. Sea /J.=Marram crass, 

 q.v. R. &ur=Sparganiatn. R. j>;are=Typha. 

 R. warMer=Salicaria strepera. R. wnn= 

 B. warbler, q.v. 



