PO'RISM, a kind of geometric proposition in high favor among ancient Greek mathe maticians, but of which the notices that have come down to us are so few and meager that, till lately, mathematicians were not agreed about what a porism really was. The ancient works in which porisms are mentioned are the Collectiones Hathernaticce of Pap pus, and the Commentarli of Proclus. Dr. Robert Simson (q.v.) was the first to restore the probably original form of porisms. As defined by Playfair, "a porism is a proposi tion affirming the possibility of finding such conditions as will render a certain problem indeterminate, or capable of innumerable solutions." Good examples of porisms are given in Simson's Opera Religua; Playfair's " Origin and Investigation of Porisms" (Trans. of Roy. Soc. of Edin. vol. iii.): Wallace's paper, " Some Geometrical Porisms, etc." (Edin. Trans. vol. iii. etc.).
PORK (Fr. pore, a hog, from Lat. porcus). The flesh of swine forms a very large por tion of the animal food of most nations, although it is not the most nutritive, as will be seen by the following comparison of the four principal kinds of flesh-food: It has qualities, however, which especially fit it for man's use; its fatness makes it a very heat-giving food for cold and temperate climates; whilst it surpasses all other kinds of animal food in the ease with which it may be preserved by salting and drying. Hence the trade in pork is considerable in all countries where it is used, but especially so in Great Britain and America, where vast quantities are cured for the supply of ships and the army, and for home use. The quantity of pork imported into Britain (of which the
greater part comes from the United States) is prodigious; in 1875 the value of the bacon and hams imported amounted to R6,955.200, besides pork to the value of £504,386. Mill ions of hogs are raised iu the state of Ohio, and the curing of swine's flesh is the staple business of Cincinnatiand other towns. A more vivid idea of the extent of this vast trade cannot be given than a recent statement of the Louisville Gazette, that " there were between 5 and 6 acres of barreled pork piled up 3 tiers high, in open lots, and not less than 6 acres unpiled, which would cover 18 acres if closely laid in a single tier on the ground; besides all which, 6 acres of pens were filled with hogs waiting to be killed." America has long furnished the chief supply of mess and common pork not only for the British army, navy, and mercantile marine, hut also for those of most European nations. Next to America, Ireland, and especially the neighborhood of Cork, furnishes the largest supply of cured pork; and London and Wiltshire, and other parts of England, also fur nish vast quantities of bacon and hams for general consumption.