center, and are of various and often beautiful patterns. See Mosses and Musci. Per'kin, Sir Wm. Henry, LL. D., Ph. D.,

F. R. S., eminent English chemist, the discoverer of the first aniline color and founder of the coal tar color industry, the jubilee of which was celebrated in 1906, when distinguished scientists from all over the world came to England to do Sir William honor. Born in London in 1838, he was educated at the City of London School and for a time studied chemistry under Dr. A. W. Hofmann at the Royal College of Chemistry. In 1856, while pursuing his own researches, he was led to discover aniline purple or mauve, a discovery which founded the industry of the coal-tar colors. His name is also connected with other important discoveries, for which he has been made the recipient of many honors. Among the medals he held was one awarded by the American Chemical Society, on the occasion of his visit to the United States in 1006. The influence of the great chemist's discovery on the coal-tar industry has been great, for to-day no less than 700 coloring matters are derived from coal-tar products. He died on July 14, 1907.

Per'nambu'co, a state of northeastern Brazil, has an area of nearly 50,000 square miles, and is fertile and thickly populated on the coast, though somewhat barren and mountainous inland. Pernambuco produces great quantities of sugar and a good deal of coffee, cotton, tobacco and maize. Cattle and horses are raised on the plateaus of the interior. The capital is Pernambuco or Recife, a town of nearly 200,000 people. This is a great trading-port, owing to its nearness to Europe, and that in spite of the fact that the harbor is not navigable by the largest vessels. Pernambuco ranks third among the cities of Brazil (g. v.).

Perpet'ual Motion, stated in modern terms, is a name given to the problem of creating energy. Lavoisier proved the impossibility of creating or annihilating even the most minute portion of matter. In like manner all modern physical investigations have shown the impossibility of creating or annihilating energy. Since no mechanism is known which does not absorb some energy in friction, it is evident that if we are to keep any mechanism in motion we must constantly supply it with energy. This great generalization may be said to date from 1847, when Helmholtz published his great memoir on the Conservation of Energy. But long before that time it was well-known to clear thinkers that the law of the conservation of energy applies to all purely mechanical operations. Accordingly in 1775 the French Academy declared that it would not thereafter receive any communications upon the subject of perpetual motion. This latter date may, therefore, be considered as marking the complete overthrow of the idea

that motion can be secured in any actual mechanical device without a constant supply of energy; and 1847 may be considered as marking the overthrow of the idea that perpetual motion can be secured by any means whatever, mechanical, electrical, thermal or other. See Dynamics and Energy. Per'rault {pa'ro'), Charles, a French author, was born at Paris, Jan. 12, 1628, the youngest of an advocate's four sons. He was sent at nine years of age to the College of Beauvois, but quarreled with his teachers, and the rest of his education was left to himself. He studied law and was admitted to practice, but, soon tiring of the routine of the legal profession, he procured an easy post under his brother, the receiver-general of Paris. Perrault's name has been made immortal by eighteen fairy-tales, published in 1Ŏ97. The titles include The Sleeping Beauty, Little Red Riding-Hood, Bluebeard, Puss in Boots, The Fairy, Cinderella, Hop o' My Thumb and others dear to childhood. Perrault died at Paris, May 16, 1703. Per'ry, Oliver Hazard, an American naval officer, was born at South Kingston, R. I., Aug. 23, 1785. He entered the United States navy in 1809, and at the beginning of the War of 1812 was transferred at his own request from the command of a division of gunboats on the Atlantic coast to serve under Commodore Chauncey on Lakes Erie and Ontario. He participated in the attack upon Fort George at the head of a body of seamen, but his fame rests upon the victory he won over the British squadron on Lake Erie, near Put-in-Bay, O., Sept. 10, 1813. In this action, known as Perry's Victory, the Americans were completely victorious, the result being fitly told in Perry's dispatch to the government:. "We have met the enemy, and they are ours." He was rewarded with the rank of captain and a vote of thanks by Congress. He continued in the naval service throughout thk xrax and for several years thereafter t*. til his death, which took place at Port Spain, on the island of Trinidad, Aug. 23, i'i.

Persepolis (pr-sĕp'-lĭs) (Persia City), the Greek name for the capital o ancient Persia, the Persian name having beer) lost This city was situated in a beautiful plain near the junction of the Araxes (Boildoinir) and the Medus ^(Polwar) River. Nothing remains of the city at the present day

Description images/pp0350 1

commodore o.h.perry