PROJECTION 



PROMETHEUS 



439 



attain a velocity of 522 feet per second. If pro- 

 jected downwards with a greater velocity it will be 

 retarded, since the resistance due to the atmosphere 

 is greater than the weight of the body. If pro- 

 jected upwards with a speed of 800 feet per second 

 it will reach a height of only 5112 feet instead of 

 nearly 10,000, and will return to earth again with 

 a velocity of 351 feet. These results show why 

 a meteoric stone never reaches the earth's surface 

 with a velocity of more than a few hundred feet 

 per second. It matters not with what relative 

 speed the meteor may meet the earth. Once it 

 gets into the atmosphere its kinetic energy is 

 rapidly dissipated in heat, and much of its sub- 

 stance volatilised at the high temperature that 

 'suits. Our atmosphere, in fact, acts as a practi- 

 oally perfect shield to meteoric bombardment. 



For projectiles discharged from firearms, see 

 the articles on Bullet, Cannon, Cartridge, Firearms, 

 Gun, Rifles, Shell, Shot. 



Projection is the representation on any sur- 

 face of objects or figures as they appear to the eye 

 of an observer. It thus includes Perspective (q.v"), 

 and is most simply illustrated by the shadow of an 

 object thrown by a candle on a wall ; the shadow 

 being the projection and the place of the light the 

 position of the eye. The theory of projections is 

 of great importance, both in mathematics and geo- 

 graphy, being, in the former case, perfectly general 

 in its application, while in the latter only the pro- 

 jection of the sphere is required. Projections of 

 the sphere are of various kinds, depending upon 

 the position and distance of the eye from the 

 sphere, and the form of the surface on which the 

 projection is thrown ; thus we have the ortho- 

 graphic, stereographic, globular, conical, and cylin- 

 drical or Mercator's projections, all of which are 

 treated of under the article MAP. Another pro- 

 jection frequently employed is the gnomonic. In 

 the gnomonic projection the eye is supposed to lie 

 situated at the centre of the sphere, and the sur- 

 face on which the projection is thrown is a plane 

 surface which touches the sphere at any one point 

 (called the principal point). It is evident that a 

 map constructed on the gnomonic projection is 

 sensibly correct only for a circular area whose 

 circumference is at a small angular distance from 

 the principal point. From the position of the eye 

 in the gnomonic projection (which is not suited for 

 representing large portions of the earth's surface) 

 it follows that all great circles or portions of great 

 circles of the sphere are represented by straight 

 lines, for their planes pass through the eye. The 

 gnomonic projection derives its name from its con- 

 nection with the mode of describing a gnomon or 

 I)ial (q.v.). The gnomic and stereographic pro- 

 jection of crystals is described and illustrated at 

 CRYSTALLOGRAPHY. 



Prolapsus Alii is a common affection of the 

 termination of the intestinal canal, and consists in 

 an eversion of the lower portion of the rectum, and 

 it* protrusion through the anus. It may depend 

 on a naturally relaxed condition of the parts, as 

 in infancy, or may be caused by violent straining 

 in caws of costiveness, piles, &c. Whenever it 

 occurs the parts should l>e washed, and if possible 

 replaced by careful pressure with the hand ; and 

 if tlii'v do not easily return the forefinger should lie 

 oiled and pushed up into the anus, and it will con- 

 vey the protruded intestine with it, after which 

 the patient should retain the recumbent position 

 for some hours. If it cannot lie returned by the 

 above means surgical assistance should lie at once 

 sought. In order to remove the tendency to pro- 

 lapsus the patient should regulate his bowels so as 

 to avoid costiveness, should sponge the parts after 

 every evacuation with cold water or soap and water, 



and if necessary use astringent injections, as, for 

 example, a weak solution of sulphate of iron, 1 

 grain to the ounce. In young children the power 

 of straining, and therefore the tendency to the 

 occurrence of the protrusion, may be much dimin- 

 ished by preventing their feet from resting on the 

 ground during defecation. Dr Druitt (in his Sur- 

 geon's Vade Meciim) recommends a plan first sug- 

 gested by Dr M'Cormac viz. that when the stools 

 are passed the skin near the anus should be drawn 

 to oue side with the hand so as to tighten the ori- 

 fice. If after the adoption of these means the 

 bowel continues to descend certain surgical means 

 must be resorted to, as destroying a portion of the 

 relaxed mucous membrane by the application of 

 nitrate of silver or nitric acid, or removing a part 

 of the loose skin surrounding the orifice, with or 

 without portions of the mucous membrane as 

 well. 



Prolapsus Uteri. See WOMB. 



Proletariate, a term used to denote the 

 lowest and poorest classes of the community. It 

 is derived, through the French, from the Latin 

 proletarii, the name given in the census of Servius 

 Tullius to the lowest of the centuries, who were 

 so called to indicate that they were valuable to the 

 state only as rearers of offspring (proles). The 

 word has come much into use in the literature of 

 Socialism (q.v.); see also MARX. 



Prologue, a preface or introduction to a dis- 

 course or poem, as the prologue to Chaucer's 

 Canterbury Tales; but more especially the dis- 

 course or poem spoken before a dramatic perform- 

 ance, corresponding to the Epilogue (q.v.) at its 

 close. This usually stands outside the action of 

 the piece, an external adjunct to it, being, indeed, 

 a mere address to the public occasioned by the 

 play. The introduction proper, again, belongs to 

 the action itself, and this we find provided for in 

 the prologue of Euripides, spoken by one of the 

 characters, in narrative form, half within and half 

 without the action ; in the separate induction of 

 many old English plays ; and in the preludes and 

 prologues of modern dramas like Faust. 



Prometheus, a great cujture-hero of Greek 

 mythology, the son of the Titan lapetus and of 

 Clymene, brother of Atlas, Mencctius, and Epi- 

 metheus. Hesiod tells his history as follows : Once, 

 under the reign of Zeus, when men and gods were 

 disputing with one another at Mecone as to which 

 portions of the victims at sacrifices were to be given 

 to the gods, Prometheus, to outwit Zeus cut up 

 an ox, and placed on one side the best parts covered 

 with ofl'al, on the other the bones covered with 

 fat. Zeus was asked to choose, but, finding the 

 deceit practised upon him, avenged himself on the 

 mortals by withholding from them the fire neces- 

 sary for the cooking of the meat ; whereupon Pro- 

 metheus stole it in a hollow fennel-stalk, and 

 brought it to them. Zeus next caused Hephspstus 

 to mould a virgin of wondrous beauty, Pandora 

 (q.v.), whom Epimetlieus was unwise enough to re- 

 ceive as a present from Hermes, and thus brought 

 through her all imaginable ills upon humanity. 

 Prometheus himself was chained to a rock, and an 

 eagle sent to tear his liver by day, while Zeus 

 caused it to grow anew during the night. At 

 length Hercules killed the eagle, and by the 

 permission of Zeus delivered the suffering Pro- 

 metheus. Thus far Hesiod's legend. In the 

 splendid tragedy of jEschylus, the Prometheus 

 Vinctus, Prometheus is an immortal god, a friend 

 of the human race, who does not shrink from 

 opposing the evil designs of Zeus against mankind, 

 and even from sacrificing himself for their salva- 

 tion. He is the long-suffering hero, who, although 

 overcome by Zeus's superior might, yet does not 



