ROT 



RUP 



posite, but which nevertheless become 

 apparently so by the contraction of the 

 joints of the stem, and lie packed closely 

 over one another, like the petals of a 

 double rose, the offsets of houseleek, &c. 



ROTA MERIDIA'NA. A transit 

 circle erected by Romer at Copenhagen. 

 It was a divided circle set ui)on a hollow 

 double cone, at right angles to the axis 

 of the cones, and concentric with them, 

 the circle being near one end of the axis. 

 The divisions were read by two micro- 

 scope verniers, fixed in a diameter of the 

 circle on one of the supports of the axis. 



ROTAL ACTION OF AFFINITY. 

 A term applied to the action of chemical 

 affinity, as exhibited in the voltaic cir- 

 cle, in which it assumes a circular direc- 

 tion or return upon itself. It is what 

 has been more commonly called induc- 

 tive affinity, from its analogy to magnetic 

 induction. 



ROTATE COROLLA. A wheel-shaped 

 corolla, of which the tube is very short, 

 and the segments spreading, like the 

 radii of a wheel, as in borago. 



ROTATION (in plants). A special 

 motion of the sap, observed in plants of 

 low organization. It consists in a spe- 

 cial circulation of the fluid contained in 

 the interior of each cell, the rotation 

 in one cell never interfering with that 

 in another cell. This phenomenon 

 differs from that of cyclosis, which con- 

 sists in the motion of the latex in the 

 cinenchymatous vessels. The two special 

 motions are said never both to occur in 

 the same species. 



ROTATORY MOTION {rota, a 

 wheel). When the different points of a 

 body move at the same time in different 

 directions, this is called a rotatory mo- 

 tion. Rotation on an axis implies, in 

 addition to this rotatory motion, that all 

 the parts of the body revolve round an 

 imaginary right line in a state of rest, 

 called the axis. The wheels of any piece 

 of machinery have a rotatory motion 

 round their axes ; the diurnal and annual 

 motions of the earth, a rolling ball, the 

 wheels of a waggon as it travels, are 

 illustrations both of direct and of rotatory 

 motioil. 



ROTELLI'NiE. Wheel-shells; a sub- 

 family of the Trochidcc, named from the 

 genus rotella; they are perlaceous, and 

 nearly discoid in shape, with a thickened 

 mass over the inner lip. 



ROTI'FERA {rota, a wheel, fero, to 

 carry). Infusorial animalcules, consist- 

 ing of minute, transparent, soft, aquatic 

 291 



animals, with distinct muscular and 

 nervous systems, and having the appear- 

 ance of revolving wheels, produced by 

 the rapid motion of the cilia placed round 

 the mouth. They are distinguished into 

 the loricata, which have the surface of 

 the body protected by a sheath ; and the 

 nuda, in which the body is soft and 

 naked. 



ROTTEN-STONE. A massive mine- 

 ral, consisting of alumina, silica, and 

 carbonaceous matter, found near Bake- 

 well, &c., and employed in polishing 

 metals. 



RUBBLE, A term applied by quarry- 

 men to the upper fragmentary and de- 

 composed portion of a mass of stone. 



RU'BELLITE. Red schorl or tour- 

 maline, found at Rozna in Moravia. 



RUBY. A crystallized gem of variou.s 

 shades of red. The spinelle ruby is 

 scarlet-coloured ; the balass ruby is of a 

 pale or rose red ; the rubicelle is yellowish 

 red. The oriental ruby of jewellers is 

 the red sapphire. 



RUBY SILVER ORE. A double 

 sulphur-salt ; distinguished into tlie dark 

 and the light red, both of the same crys- 

 talline form, but in the latter of which 

 sulphuret of arsenic takes the place of 

 sulphuret of antimony of the former. 



RUDO'LPHINE TABLES. A set of 

 astronomical tables computed by Kepler, 

 and founded on the observations of Tycho 

 Brahe. They were named in honour of 

 Rudolph II., emperor of Bohemia, and 

 were the first tables ever calculated on 

 the hypothesis that the planets move in 

 elliptic orbits. 



RUMINANTIA (rumino, to chew the 

 cud). An order of the Mammalia, con- 

 taining the ox, deer, sheep, &c., charac- 

 terized by their cloven feet, the absence of 

 incisors in the upper jaw, and the com- 

 plex arrangement of the stomachs by 

 which rumination is effected. 



RUMINATED. A term applied to 

 the albumen of certain plants, in which 

 it is perforated in various directions by 

 dry cellular tissue, as in the nutmeg, and 

 pulmaceous plants. 



RUNNER. A prostrate aerial stem, 

 forming at its extremity roots and a 

 young plant, which itself gives origin to 

 new runners, as in strawberry. 



RU'PTURING or SOLUBILITY. In 

 Botany, the spontaneous contraction of a 

 portion of the pericarp, by which its tex- 

 ture is broken through, and holes formed 

 for the dispersion of the seeds, as in An- 

 tirrhinum and Campanula. 

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