PER 



557 



PER 



snail, or Turbo littortus, Liu. '2. In bo- 



tany, a species of Yinca. 



PER'MIT, from pennctto. A license or 

 instrument granted by the officers of ex- 

 cise, authorising the removal of goods 

 subject to excise duties. Permits are one 

 of the useless nuisances of our excise 

 laws. 



PEHMPTA'TIOX. In algebra, the arrange- 

 ment of any determined number of ob- 

 jects in all possible orders, after each 

 other. 



PER'NIS. A genus of birds of prey : the 

 honey-buzzards, separated by Cuvier from 

 the kites. Order Accipitrcs, Lin., family 

 ZHurnce, Cuv. 



PERORA'TION, from per and oro, to pray. 

 The concluding part of an oration, where 

 the speaker recapitulates the principal 

 points of his argument, and urges them 

 with greater earnestness. 



PEROX'IDE. See PER. 



PERPENDIC'ULAR, Lat. perpendicularis, 

 relating to a plumb-line (perpetidiculum) , 

 from per and pendeo, to hang. A perpen- 

 dicular line, or a perpendicular, means in 

 common language any line falling at 

 right angles to the plane of the horizon, 

 that is, extending from some point in a 

 right line towards the centre of the earth 

 or centre of gravity. 

 In geometry, a per- 

 pendicular is any 

 line falling at right 

 angles on another 

 line , or making equal 

 angles with it on 

 either side. In -u- 

 nery, the name is given to a small instru- 

 ment for finding the centre line of a pier e 

 of ordnance, in the operation of pointing 

 it at an object. 



PERFENDIC'ULAR. LIFT (on canals). A 

 contrivance for passing boats from one 

 level to another. 



PER'PETUAL MO'TIOJJ. Motion that gene- 

 rates a power of continuing itself indefi- 

 nitely. Every body in nature, when in 

 motion, would continue in that state, and 

 every motion once begun would be per- 

 petual, but for the operation of some ex- 

 ternal causes, as friction, gravity, &c. ; 

 but since no absolute power can be gained 

 by any combination of machinery, to 

 counteract these causes, it follows that a 

 perpetual motion can never take place by 

 any purely mechanical contrivance; yet 

 this is a problem which has engaged the 

 attention of many ingenious, though ill- 

 educated men. 



PERPET'UAL SCREW. A screw which 

 acts against the teeth of a wheel, and 

 continues its action without end. 



PERPETU'ITY. 1. In law, is where, if all 

 that have an interest join in the convey- 

 ance, yet they cannot bar the estates. 

 2. In annuities, the number of years 



in which the simple interest of any prin- 

 cipal sum will amount to the same as the 

 principal itself. 



PER'PYEN-WALLS. llie name given to 

 two walls in Fotheringhay church, 

 which divide the body of the (hurch 

 from the aisles. The origin of the name 

 does not appear to be known. 



PER'RON (French). A staircase lying 

 open or withoutside the building ; more 

 properly the steps in front of a building, 

 which lead into the first story, when this 

 is raised above the level of the ground. 



PER SALTHM. By a leap, at once. 



PERSE. 1. Of its own nature ; i.e. in 

 virtue of its own entity, as the sun gives 



light per se. 2. By itself; as when a 



body is distilled without the addition of 

 any other matter, it is said to be distilled 

 per se. 



PER'SEUS. 1. In mythology, a hero, the 



son of Jupiter. 2. In astronomy, a 



northern constellation. 



PER'SIAN BERRIES. A yellow dye drug, 

 the fruit of a Persian variety of the 

 Ithammis infectorius, which grows in, 

 Persia. See BERRIES or AVIGNON. 



PER'SIAN WHEEL. A wheel used for 

 the purposes of irrigation, and usually 

 equipped with floats on its circumference, 

 and turned by the stream in which it is 

 placed, but turned by animal power when 

 the water in which it is worked is stag- 

 nant. Upon its rim are buckets sus- 

 pended, which are filled with water at 

 the lowest point, and empty themselves 

 into a receiver at the highest point, from 

 which it is conveyed away in canals. This 

 is one of the cheapest and most efficient 

 modes of raising water to small eleva- 

 tions, and requires neither nicety in 

 construction, nor attention in working, 

 especially where a running stream is 

 obtained. It is much used in the East. 



PER'SIANS. In architecture, the same as 

 Caryatides (q. v.). According to some, the 

 male figures only are called Persians, and 

 the female figures Caryatides 



PERSIS'TENT, Lat. persistens. Perma- 

 nent. Applied to flower-cups which re 

 main long after the flower. Also, in 

 optics, to the duration of the impression 

 of light upon the retina of the eye, after 

 the removal of the source of the light. 



PER'SON , Lat. persona. 1. A mask used 

 by actors on the stage, from per and sonus, 

 sound. The term is now used to denote a 



human being. 2. In grammar, the agent 



which performs, or the patient which 

 suffers, the action expressed by the verb, 

 and hence, also, we apply the word person 

 to the termination or modified form of the 

 verb used in connection with the persons, 

 as the verb is in the first, second, or 

 third pcrsun. Such verbs are usually de- 

 nominated personal verbs. 



PERSON A'T^. A natural order of plants 



