ROT 



ROY 



for medicinal purposes. The cisttis, or 

 rock rose, and the h} pincum, or Si. 

 John's wort, have been annexed also to 

 this order. It niav oe observed, that 

 gum labdanum is an odoriferous balsam, 

 or resin, which is found on a species of 

 the rock-rose, viz. the cistus ladanit'era, 

 that grows natural!} in the Levant. This 

 substance is collected by the natives by 

 means of leathern thongs, rubbed gently 

 over the surface of the shrub which pro- 

 duces it. From a species of the hyperi- 

 cuni, an oil is extracted, that proves an 

 excellent vulnerary. 



ItOTALA, in botany, a genus of the 

 Triandria Monogynia class and order. 

 Natural order of Caryophyliere. Essen- 

 tial character: calyx three-toothed ; co- 

 rolla none ; capsule three-celled, many- 

 seeded. There is but one species, viz. 

 R. verticiiiaris, a native of the East In- 

 dies. 



ROTATION, in geometry, a term 

 chiefly applied to the circumvolution of 

 any surface round a fixed and immoveable 

 line, which is called the axis of its rota- 

 tion : and by such rotations it is, that so- 

 lids are conceived to be generated. The 

 iate ingenious M. de Moivre shows how 

 solids, thus generated, may be measured 

 or cubed. His method is this : for the 

 fluxion of such solids, take the product 

 of the fluxion of the absciss, multiplied 

 by the circular base ; anil suppose the ra- 

 tio of a square to the circle inscribed in it 



to be : then the equation expressing the 



nature of any circle, whose diameter 

 is cl, is y y = d x x x. Therefore 



4 d x x x* x . n . 



is the fluxion of a por- 



n 



t.ion of the sphere ; and, consequently, 

 the portion itself 4^ d x x x xi, and 



. ,. , . 

 the circumscribed cylinder is 



and therefore the portion of the sphere is 

 to the portion of the circumscribed cylin- 

 der, as %d 1 x to d x. 



ROTHIA, in botany, so named in ho- 

 nour of Albrecht Wilhelm Roth, physi- 

 cian at Bremen ; a genus of the Syrigene- 

 sia I'olygamia JEqualis class and order. 

 Natural order of Composite Semifloscu- 

 losse. Cichoracex, Jussieu. Essential 

 character: calyx many-leaved, in a single 

 row, equal, woolly ; receptacle in the ray 

 chali'y, in the disk villose ; seeds in the 

 ray bald, in the disk pappose. There is 

 only one species, viz. R. andryaloides. 



ROTTBOELLIA, in botany, so named 

 in memory of Christian Friiis Rottboel, 



Professor of Botany at Copenhagen ; a 

 genus of the Polygamia Monoecia class 

 and order. Natural order of Gramina, 

 Graminea:, or Grasses. Essential charac- 

 ter : rachis jointed, roundish, in most spe- 

 cies filiform ; calyx ovate, lanceolate, flat, 

 one or two-valved; florets alternate on a 

 rie.xuose rachis. There are seventeen 

 species. 



ROUND, in a military sense, signifies a 

 walk which some officer, attended with a 

 party of soldiers, takes in a fortified place 

 around the ramparts, in the night-time, 

 in order to see that the Gentries are 

 watchful, and every thing in good order. 

 The Gentries are to challenge Che round? 

 at a distance, and rest their arms as they 

 pass, to let none come near them ; and 

 when the round conies near the guard, 

 the centry calls aloud, "Who comes 

 there ."' and being answered, " the 

 rounds;" he says "stand;" and then calls 

 the corporal of the guard, who draws his 

 sword, and calls also, " Who comes 

 there ?" and when he is answered, "the 

 rounds," he who has the word advances, 

 and the corporal receives it with his 

 sword pointed to the giver's breast. Iti 

 strict garrison, the rounds go every quar- 

 ter of an hour. 



ROUSSEA, in botany, so named in me- 

 mory of the celebrated Jean Jacques 

 Rousseau ; a genus of the Tetrandria Mo- 

 nogynia class and order. Essential cha- 

 racter : calyx four-leaved ; corolla one pe- 

 talled, bell-shaped, four-cleft, inferior; 

 berry quadrangular, many-seeded. There 

 is but one species, viz. R. simplex, this 

 is a small climbing shrub, found by Com- 

 merson in the island of St. Mauritius. 



ROXBURGHIA, in botany, so named 

 in honour of William Roxburgh, M. D ; a 

 genus of the Octandria Monogynia class 

 and order. Essential character: calyx 

 four-leaved ; corolla four-petalled, in- 

 wardly keeled ; nectary four, awl-shap- 

 ed ; leaflets on the apex of the keel of 

 the petals, converging ; anthers linear, 

 sessile in the grooves of the keel; cap- 

 sule one-celled, two-vulved ; seeds many, 

 inserted in a spongy receptacle. There 

 is but one species, viz. R. gloriofoides, a 

 native of Coromandel, in moist valleys 

 between the mountains, flowering in the 

 cold season. It is the Canipoo Tiga of 

 the Telingas. 



ROYALTIES, are the rights of the 

 King. See PREROGATIVE. 



ROYAL Exchange. The term royal, 

 applied to the Exchange of London, ori- 

 ginated with Queen Elizabeth, a princess 

 who, though tinctured with the arbitrary 



