POP 



580 



POR 



PONS VAH'OLII. An arched eminence of 

 the medulla oblongata. 



POMTEE'. In glass-works, an iron instru- 

 ment used to stick the glass on at the bot- 

 tom, for the more convenient fashioning 

 of the neck of it. 



PON'TIFF, Lat. pout if ex, a high priest. 

 The Romans had a college of pontiff s(pon- 

 tifices) ; the Jews had their pontiffs, and 

 in modern times the Pope is denominated 

 the sovereign pontiff, and his reign a 

 pontificate. 



PONTO'ON, Fr. and Span, ponton. 1. A 

 floating bridge, formed of flat-bottomed 

 boats, anchored in two lines, with planks 

 laid across, for the passage of soldiers and 

 military stores. The boats themselves are 

 sometimes called pontoons, and the bridge 

 formed of them is accordingly a pontoon- 

 bridge. 2. In naval affairs, a lighter : a 



low flat vessel, resembling a barge, fur- 

 nished with cranes, capstans, and other 

 machinery; used in careening vessels 

 chiefly in the Mediterranean. 



PONTOO'N-CAR'RIAGE. A carriage made 

 with two wheels only, and two side pieces, 

 whose fore-ends are supported by timbers. 



PONT-VOLANT. A flying-bridge. This is 

 a description of light bridge, used in 

 sieges, for surprising a post or outwork 

 which has but a narrow moat. It is com- 

 posed of two small bridges, laid one over 

 the other, and so contrived that by the 

 aid of cords and pullies, the upper one 

 may be drawn forward till it reaches the 

 destined spot. 



Poop. The highest and aftmost deck of 

 a ship. The poop-royal is a short deck or 

 platform, placed over the aftmost part of 

 the poop, in the largest of the French and 

 Spanish men of war, and serving as a 

 cabin for their masters and pilots. This 

 is usually called the top-gallant-poop by 

 our seamen. To have wind in the poop is to 

 have the wind behind or favourable. 



POOP'INO. The shock of a heavy sea 

 upon the stern or quarter of a ship, when 

 she scuds before the wind in a tempest. 

 The term is also used to denote the action 

 of one ship running her stem into an- 

 other's stern. 



POPE, Papa, xavrot, father. 1. The Bi- 

 shop of Rome and head of the Catholic 

 Church. 2. A small fish, the ruff. 



POP'INJAY. 1. In ornithology, a parrot. 

 2. The green woodpecker of Europe. 



POP'LIN. A stuff made of silk and 

 worsted. 



POPLIT'EAL. Appertaining to the ham 

 fpoples), or back part of the knee-joint, as 

 the popliteal artery. 



Pop'uLrs. Poplar tree. A genus of 

 about 20 known species. Dicecia Octan- 

 dria. The most known species are the 

 Abele or great white poplar (P. alba], the 

 Black (P. nigra), the Aspen or trembling 

 poplar (P. tremula) ; the one indigenous. 



All the species are of rapid growth ; the 

 wood is soft, but easily wrought, and not 

 apt to swell or shrink. The Lombardy 

 poplar (P. dilatata), is the finest species 

 of the tree. 



POR'CATE, Lat. porca, ridge. "When a 

 surface has several longitudinal ridges. 



POR'CELAIN. A beautiful and semi- 

 transparent variety of earthenware, first 

 'and extensively yet) manufactured in 

 China and Japan. The Chinese call it 

 tse-ki, and the two chief ingredients which 

 they employ in the manufacture of it are 

 pe-tun-tse, and Jcao-lin. The Portuguese 

 were the first importers of the article, 

 and bestowed upon it the name of porce- 

 lain, fromporcella, a cup. The name is now 

 used to denote generally all earthenware 

 which has been semi- vitrified, and has 

 become somewhat translucent in the pro- 

 cess of firing; and the name china, or 

 china-ware, is again used, to denote the 

 finest variety of porcelain. See POTTERY. 



PORCEI/LANITE. A siliceous mineral, of 

 various colours, which occurs in amor- 

 phous masses, or fragments often rifted. 

 Its fracture is imperfectly conchoidal, 

 more or less glistening, and often has the 

 aspect of certain porcelains. It melts be- 

 fore the blowpipe into black scoria?, and 

 yields by analysis silex 61, alumina 27, 

 potash 3'6, magnesia 3, oxide of iron 2'4. 

 It is supposed to be an alteration of some 

 variety of argillaceous slate by pseudo- 

 volcanic heat. It occurs in large masses 

 near the pitch-lake of Trinidad, and often 

 in the vicinity of coal-mines. 



PORCH. An arched vestibule at the 

 entrance of a building. See PORTICO. 



POR'CCPINE. 1. In zoology, see HYSTRIX. 



2. The porcupine, properly so called, 



is the H. cristata, Lin. The name porcu- 

 pine (Fr. pore- 4 pic) is from porcus (Welch 

 pore), a pig, and spina, a spine, or thorn : 

 that is, spiky-hog, or spine-hog. 



POR'CVPINE-FISH. A species of diodon 

 covered with spines. 



PORES, from trcgo;, a passage. 1. The 

 small interstices between the solid parti- 

 cles of bodies. 2. The animal body is- 



provided with pores for respiration. 



PORIF'ERA, from poriis and fero. ) An 



PORIPH'ERA, from -ro^os and Qtgv. ) or- 

 der of Radiata, forming the various ge- 

 nera of sponge met with on every rocky 

 coast of the ocean. 



PO'RISM, from VOIIS/MS, acquisition. 

 The ancient geometers gave this name 

 to two classes of propositions: (1.) to co- 

 rollaries ; and (2.) to propositions affirm- 

 ing the possibility of finding such con- 

 ditions as will render a certain problem 

 indeterminate, or capable of innumerable 

 solutions. The porism is not a theorem 

 r.or a problem, or rather it includes both. 

 It asserts that a certain problem is inde- 



