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 PERPETUAL MOTION as well as of the machine of Orffyreus, and also of other engines sought to be moved by- water and other means, may be found in Mr. Dircks's work. Ever since the establishment PERRAUD 309 FIG. 2. Capra's Machine. of the laws of motion, about the middle of the 17th century, the impossibility of produ- cing such a perpetual motion has been ap- parent to all who have mastered the princi- ples of mechanics. Admitting the third law, that action and reaction are equal, perpetual motion can only become possible when a body once set in motion shall meet with no resis- tance, which is an impossible condition. If a top could be made to spin in a perfect vacuum upon a point without friction, it might never come to rest ; but it could exert no external force without losing its own. The impossi- bility of a perpetual motion was assumed by Stevinus in the demonstration of a principle in statics. He supposed an endless chain of balls hung over two unequal inclined planes of equal altitude, the chain forming a loop beneath the planes. It is demonstrated that the weight of the balls on each plane, multiplied into the reciprocal length of the planes, will be equal, and that therefore the forces will balance each other; but Stevinus concluded that an equi- librium would result by assuming that other- wise an absurdity, viz., a perpetual motion, could take place. Another demonstration of the impossibility of perpetual motion is the establishment of the doctrine of the conserva- tion of forces. (See CORRELATION AND CON- SERVATION OF FORCES, HEAT, and MECHANICS.) This doctrine was advocated by Count Rum- ford, and demonstrated by him with a con- siderable approach to accuracy ; but the more recent investigations of Joule are regarded as more satisfactory and complete. The doctrine has also been advocated in a theoretical man- ner by Dr. Mayer of Heilbronn and by Profes- sors Henry, Balfour Stewart, Maxwell, Grove, and others. But it can hardly be said that this places the matter in any clearer light than that given by the laws of motion. In either aspect a mechanical perpetual motion is clear- ly an absurdity. PERPIGNAff, a city of S. France, capital of the department of Pyrenees-Orientales, on the right bank of the Tet, at its confluence with the Basse, 6 m. from the Mediterranean, 34 m. S. of Narbonne, and 425 m. S. by E. of Paris; pop. in 1872, 27,378. It commands the S. E. entrance to France from Spain by the Pyrenees, and is strongly fortified with a wall and fosse, and commanded by a citadel with a double line of defences. In character the city is Spanish. Its streets are narrow and dirty, and the houses are semi-Moresque, with wooden balconies and inner courts. Over the Basse there is a bridge of a single arch, and one of seven arches over the Tet. Most of the public buildings date from the Spanish period, and are built of brick or rolled pebbles. In the building of the former university, an institu- tion of the 14th century which was abolished by the revolution, is the public library, con- taining 18,000 volumes. The city has a fine cathedral, a theological seminary, a high school, a botanic garden, two hospitals, manufactories of woollen cloth, lace, leather, soap, and soda, and a considerable commerce in red wines, liqueurs, brandy, oil, silk, wool, iron, and cork. Perpignan belonged with the province of Roussillon to the kingdom of Aragon, but was taken by the French in 1475, after being re- duced by famine. Restored to Spain, it was again conquered in 1642, and finally included in the cession to France of Roussillon in 1659. The Spaniards were defeated by the French under the walls of the city in 1794. PERQUIMANS, a N. E. county of North Caro- lina, bordered S. by Albemarle sound, and drained by Perquimans river ; area, about 200 sq. m. ; pop. in 1870, 7,945, of whom 3,998 were colored. It has a nearly level surface, and the soil is generally fertile. The chief productions in 1870 were 34,232 bushels of wheat, 310,135 of Indian corn, 27,519 of oats, 32,851 of sweet potatoes, 1,340 tons of hay, and 593 bales of cotton. There were 733 horses, 1,061 milch cows, 1,906 other cattle, 847 sheep, and 7,367 swine. Capital, Hertford. PERRAUD, Jean Joseph, a French sculptor, born at Monay, department of Jura, in 1819. He was apprenticed to a wood carver, studied in Lyons and Paris, and won the grand prize in 1847, which entitled him to several years' residence in Rome, where he executed a bass relief entitled " Leavetaking." Among his subsequent works are statues of " The Child- hood of Bacchus," " Ste. Genevieve," and " Galatea;" many works for public buildings, including a group of " The Day " for the ave- nue of the Observatory (1874), and of " The Lyrical Drama " for the new opera house opened in 1875, busts of Mozart and Beethoven for the theatre at Baden-Baden, &c. His