POISON IVY 287 POLA POISON IVY, a climbing plant which closely resembles the woodbine and which is very irritating to sensitive skins. It may be distinguished from the woodbine by its having only three leaves on a twig, while all other harmless vines have five leaves, one for each finger of the hand. A simple remedy for the poison is a weak solution of common baking soda and water, applied immediately after ex- posure. POISSON, SIMEON-DENIS, a French geometer; born in Pithiviers, department of Loiret, June 21, 1781; and displaying an aptitude for mathematics, he was re- ceived into the Ecole Polytechnique in 1798. In 1802 he became a professor in the Polytechnique; in 1808 a member of the Bureau des Longitudes; in 1809 professor in the Faculty of Sciences; member of the Institute in 1812, etc.; and this list of distinctions was crowned in 1837 by his elevation to the dignity of a peer of France. Poisson's whole life was devoted to the prosecution of sci- entific reseai'ch, and the fruits of his pen number about 300 memoirs. Of the separate treatises published by Poisson, the best known is the "Treatise on Me- chanics" (1833) ; others were on capil- lary action, the mathematical theory of heat, the motion of projectiles, and, lastly, the celebrated work "On the Invaria- bility of the Mean Movement of the Planetary Axes." Poisson is fairly con- sidered one of the chief founders of the science of mathematical physics. He died April 25, 1840. POITIERS, or POICTIERS, a town of France, on the Clain, formerly capital of the province of Poitou, at present of the department of the Vienne. The town occupies a large space, the houses being often surrounded by gardens and or- chards. The principal edifice is the cathedral, founded by Henry II. of Eng- land about 1162. Poitiers is one of the most ancient towns of France, and the vestiges of a Eoman palace, of Roman baths, of an aqueduct, and an amphi- theater still remain. Two famous bat- tles were fought in its vicinity, that in which Charles Martel defeated the Sara- cen army in 732, and that between the French under their king John II., and the English under Edward the Black Prince in 1356. The manufactures are unimportant, but there is a large trade. Pop. about 42,000. POITOir, a former province of S. W. France, coincident with the present de- partments of Deux Sevres, Vendee, and Vienne. It was divided into Upper and Lower Poitou, and had for its capital Poitiers. Its early history is the same as that of Aquitania (q. v.). Poitou became a possession of the English crown when Eleanor, Countess of Poitou and Duchess of Aquitaine, after her divorce from Louis VII. of France, mar- ried (1152) Henry of Anjou, afterward Henry I. of England. Philip Augustus reconquered the province in 1205. By the peace of Bretigny, in 1360, it again reverted to England, but nine years later was retaken by Charles V. POKER, a game played with a full pack of cards, five being dealt, one at a time, to each player in rotation, be- ginning at the left of the dealer. The player winning the "pool," or "pot," always deals. An exposed card may be accepted or rejected; in the latter case it must be placed at the bottom of the pack. The cards rank in value as at Whist (q. v.). The game admits of a number of players, from 2 to 10. POKEWEED, the Phytolacca decan- dirt, a North American branching her- baceous plant, order Phytolaccacex, which is naturalized in some parts of Europe and Asia. Its root acts as a powerful emetic and cathartic, but its use is attended with narcotic effects. Its berries are said to possess the same qual- ity; they are employed as a remedy for chronic and syphilitic rheumatism, and for allaying syphiloid pains. The leaves are extremely acrid, but the young shoots, which lose this quality by boiling in water, are sometimes eaten in the United States as asparagus. POLA, until the World War of 1914- 1918, the most important naval station of Austria-Hungary; situated near the S. extremity of the peninsula of Istria; 105 miles S. of Trieste. The harbor is thoroughly sheltered, deep, and spacious enough to accommodate the largest fleet. The town is protected by forts and bat- teries, and is overlooked by the citadel, by which it and the bay are commanded. There are also artillery and powder stores, docks, slips, etc. The cathedral dates from the 15th century. Pola is also a shipping port, exporting wood, fish, sand and building stones, and im- porting provisions, coal, and bricks. Founded traditionally by the Colchians who were sent in pursuit of Jason, Pola was destroyed by Augustus, but rebuilt at the request of his daughter, Julia, on which account it was named Pietas Julia. It was destroyed in 1267 by its yenetian masters, who had conquered it in 1148; and in 1379 the Genoese, after routing the Venetians in a sea fight off the town, once more ravaged it. But it only passed from Venice in 1797 to Austria, who chose it as her chief naval harbor
