PRO 



591 



PRO 



PROJEC'TILE. 1. Impelling, or impelled 

 forward: as a projectile force, a projectile 

 motion : pro, before, andjncio, to throw. 

 2. A body projected into the atmosphere : 

 as a stone thrown from a sling, a bullet 

 from a gun, &c. The laws of projectiles 

 are identical with those by which the 

 motions of bodies falling perpendicularly 

 in free space are governed. Thus, a body 

 at A, if projected forward towards 15, will 



A 



arrive at D exactly in the same time that 

 it -would descend to C, if simply left un- 

 supported at A. 



PROJECTION. 1. In mechanics, commu- 

 nication of projectile force. 2. A 

 branch of perspective ; the art of forming 

 the representation of a body upon a plane, 

 by drawing straight lines through a given 

 point or parallel, from the contour, and 

 from the intermediate lines of the body, 

 if any, so as to cut the plane ; then co- 

 louring the respective compartments 

 according to the degree of light, shade, 

 and hue of each surface. In the projec- 

 tion of the sphere there are three principal 

 points ; the stenographic, in which the 

 eye is supposed to be placed on the sur- 

 face of the sphere; the orthographic, in 

 which the eye is supposed to be at an in- 

 finite distance ; and the gnomic, in which 

 the eye is supposed to be placed in the 



centre of the sphere. 3. Among the 



alchemists, the casting of a certain powder, 

 called the potcder of projection, into a cru- 

 cible full of some prepared metal or other 

 matter, -which was thereby to be trans- 

 muted into gold. 



PROJEC'TURE. In architecture, the jut- 

 ting out of mouldings. 



PRO'JOJOY. A peculiar vegetable pro- 

 duction, described by Mr. Mackay, of the 

 British Consulate at Maracaibo, in a 

 letter to the Zoological Society (read in 

 September, 1839). The plant somewhat 

 resembles the trefoil in its leaves and 

 branch , and at the extremities of the latter 

 there are buds, which contain neither 

 leaves nor flowers, but an insect (resem- 

 bling a wasp) which, as it grows, falls to 

 the ground, or remains on its parent plant, 

 feeding on the leaves till the plant is ex- 

 hausted, when the insect returns to the 

 earth, disappears under the surface, and 

 diet. Soon after, the two head- legs begin 



to sprout and regelate, the shoot extend- 

 ing upwards; and the plant in a short 

 time reaches the heightof six inches, and 

 produces new viviparous buds, which 

 perform again the same functions. The 

 same or a similar production is" also 

 known in North Carolina. 



PROLAPSE, prolapsus. A protrusion or 

 falling down of a part of some viscus of 

 the body, as the uterus, rectum, &c. 



PROLA.TE, Lat. prolatum. A spheroid is 

 said to be prolate when it is produced by 

 the revolution of a semi-ellipsis about its 

 long diameter ; when revolved about its 

 short diameter, it produces an oblate 

 spheroid. 



PROLIOOM'ENA, Gr. jraoXfycuivx, from 

 JT, before, and Xf j^oi, to speak. Prelimi- 

 nary observations or remarks prefixed to 

 a book, &c. 



PRO'LEGS. A name for what are other- 

 wise termed the spurious legs of insects. 

 They consist of fleshy and retractile 

 tubercles. 



PROLEP'SIS, rgoAv4><j, from JT^O, before, 

 and Xau-Savu, to take. Anticipation. 1. A 

 rhetorical figure by which objections are 



anticipated or prevented. 2. An error 



in chronology, wherein an event is 

 dated before the actual time : an ana- 

 chronism. 



PROLIF'IC, ) Lat. prolifer, from pro- 



PROLIF'EROUS, ) les, offspring, and fero, 

 to bear. A term applied in botany to 

 stems which shoot out new branches from 

 the summit of the former ones, as in the 

 Scotch fir ; and to blossoms, when one 

 grows out of another, as happens in the 

 genus polyanthus. 



PHOME'THEA.NS, from Prometheus. 

 Small glass tubes, containing concen- 

 trated sulphuric acid, and surrounded 

 with an inflammable mixture, which they 

 ignite on being pressed. 



PROM'ISE, Lat. promitsum. In law. a 

 declaration, verbal or written, made by 

 one person to another, for a good or va"- 

 luable consideration, in the nature of a 

 covenant, by which the promiser binds 

 himself, and, as the case may be, his legal 

 representatives, to do or forbear some 

 act; and gives to the promisee a legal 

 right to demand and enforce a fulfilment. 



PROM'ONTORT, Lat. promontorium. A 

 headland, or high point of land, project- 

 ing into the sea beyond the line of the 

 coast. It differs from a cape in being hiyk 

 land. 



PROXA'TION. The act of turning the 

 palm of the hand downwards, which is 

 performed by means of the muscles called 

 pronators. Opposed to supinatton. 



PRONA'TOR. In anatomy, a name com- 

 mon to two muscles of the hand, the pro- 

 nator radii quadrates, and pronaior ratiii 

 teret, the use of which is to perform tte 



