the dactylus iambus -), the ditrochæus ~~), which it is best to have in one word, and the dactylus trochaus (~~~~), which, however, on account of its hexametrical form, is to be used with great caution. The period should have a proper proportion of pauses, so as to be equally removed from total irregularity, and from a constantly-returning symmetry which approaches to metrical rhythm. The construction of sentences attained a perfection with the Greeks, which has not been reached by any other nation, for two reasons,-their deep and universal feeling of the beautiful, and the richness of their charming idiom in participles and well-sounding terminations. The Romans imitated the Greeks, but the example of Cicero is not to be closely followed, as he amplifies his phrases too much.

In physiology, periods designate the various stages in the developement and decay of the animal organization, which are distinguished by a marked character; as the period of childhood, of puberty, &c. Periods also denote, in medicine, those repetitions of phenomena which we observe in certain diseases, e. g. in intermittent fevers, the increase of the disorder in the evening, &c. Periodical diseases are such as, at certain times, make regular attacks, or are attended with regular aggravations. This property is very common, and there is hardly a disease in which it has not been observed in the case of some individual. On the contrary, there is no disease which always pursues its course periodically.

with this department of literature, the present state of knowledge and civilization cannot be understood, and the historian will find it essential to a comprehension of the great movements of our time. Châteaubriand threw Villèle from his saddle, by articles in the Journal des Débats; and when we see editors of newspapers drawing up a protest so noble and historical as that of the Paris editors on July 26, 1830, and immediately afterwards shedding their blood for the rights therein maintained; and find statesmen like Brougham, Mackintosh, Peel, contributing articles to English reviews,-we cannot be surprised at the importance of the periodical press. We have given, in the article Newspapers, a sketch of the history and present state of that branch of periodical literature. The first journal of the character of a review was the Journal des Savants, established in 1663. Its success gave rise to Les Nouvelles de la République des Lettres, by Bayle; Le Mercure, by Visé; Le Journal de Trévour, set up by P. Catrou, a Jesuit; in Italy, to the Giornale de' Literati; in Germany, to the Acta Eruditorum (q. v.). In England, the first review of this sort was the Monthly, commenced in 1749, and still published. (For further information, see the article Review.) The utility of periodicals has been very great; they have spread knowledge through quarters to which the bulky productions of the sixteenth and seventeenth century never could have penetrated. The reviews, in particular, have done much to promote the cause of truth and just thinking. But the periodical press, like every thing else in the world, has its bad side as well as its good, and one of its bad consequences has been a taste for superficial accomplishment. Periodicals, however, have become a matter of necessity, as the circle of civilization has widened, as the various nations have become more and more interested in each other, and as the great interests of mankind have been more deeply investigated and more universally discussed. For a citizen of Athens, the market and the gymnasia may have afforded a sufficient supply of news to keep him acquainted with the events generally interesting to his community; the wits of Florence may have found the shop of Burchiello (q. v.) a sufficient centre of intelligence; but our times require much more regular, extensive and effectual means for the diffusion of information on the events and productions of the day, and for the discussion of the numberless im

PERIODICALS, in the proper sense of the word, are all publications which appear at regular intervals; and in the wide sense which the word has now received, it may even be considered as embracing those publications which, as is not unfrequently the case in Germany, appear from time to time, yet neither at regular intervals nor in numbers of a fixed amount of pages (Zwanglose Hefte). The periodical press, comprising newspapers, reviews, magazines, annual registers, &c., devoted to religion, politics, the sciences, arts, amusements, husbandry, &c., is one of the most interesting and most momentous consequences of the invention of the art of printing. At first, slips of paper containing a few particulars, intended principally for the gratification of curiosity, periodicals have now become one of the most important parts of the machinery of society, particularly in England, France and the U. States. Without an acquaintance

of men.

PERIOSTEUM. (See Bone.)

PERIPATETIC PHILOSOPHY. The philosophy of Aristotle (q. v.) received this name either from his custom of teaching while walking (EрinаTE), or from the place where it was taught a walk planted with trees. We can give but a brief sketch of the system of this powerful mind. Philosophy was to Aristotle the science of knowledge. Direct knowledge, by which we know immediately the general and necessary, rests on experience. According to him, logic, as a preparatory science, as the organ of all science, has the precedence of all. Logic either treats of appearances, and is then called dialectics; or of truth, and is then called analytics. In his Physics, he opposes the two systems then prevailing (that of emanation, which taught that all things emanated from God; and the atomic, which explained the origin of things by the concourse of atoms, eternal, like God), and assumes the eternity of the world. According to him, the heavens are of a more perfect and divine nature than other bodies. In the centre of the heavens is the earth, round and stationary. The stars, like the sky, beings of a higher nature, but of grosser matter, move, though not of themselves, but by the impulse of the primum mobile. Every change presupposes a substratum (substance), that by which a thing becomes possible; a form, by which a thing becomes real; and privation, inasmuch as the existence of a certain form is founded on the exclusion of others. All change or motion takes place in regard to substance, quantity, quality and place. There are three kinds of substances-those alternately in motion and at rest, as the animals; those perpetually in motion, as the sky; and those eternally stationary. The last, in themselves immovable and imperishable, are the source and origin of all motion. Among them there must be one first being, unchangeable, which acts without the intervention of any other being. All that is proceeds from it; it is the most perfect intelligence-God. The immediate action of this first mover-happy in the contemplation of himself-extends only to the heavens; the other inferior spheres are moved by other incorporeal and eternal substances, which the popular belief adores as gods, and to which it attributes bodies, contrary to their nature. The soul is the principle of life in the organic body, and is inseparable from the body. As faculties of the soul, Aristotle enume

trition; of sensation, memory and recollection; the faculty of thinking, or the understanding; and the faculty of desiring, which is divided into appetite and volition. The ethical principles of Aristotle have been often misunderstood, partly on account of the degeneracy of his school; and he has been considered a supporter of the philosophy whose principle is pleasure; but to Aristotle, the best and highest (i. e. that which is desirable for itself) is the happiness which originates from virtuous actions. Virtue, according to him, consists in acting according to nature: by the expression "according to nature," he means, keeping the mean between the two extremes of the too much and the too little. Thus valor, in his view the first of virtues, is a mean between cowardice and rashness; temperance is an observance of the mean in respect to sensual enjoyments. Human actions, to be called moral, must be independent of external motives; otherwise they are but phenomena, the laws of which belong to physics, and are therefore indifferent to the practical philosopher. Self-action, and consequently the power to act or not to act, to act in one way or another, is the condition of all morality. Perfect happiness can be attained only in political society or the state; but the best form of state polity must be determined by circumstances. The school of Aristotle (the peripatetic school) continued at Athens uninterruptedly till the time of Augustus. Among those who proceeded from it are Theophrastus, author of several works on natural history; Strato of Lampsacus, whose views are but imperfectly known to us from some fragments preserved by Cicero and Plutarch; and Demetrius Phalereus. (q. v.) No one of the philosophical schools of antiquity maintained its influence so long as the peripatetic. Even down to modern times, its principles served as the rule in philosophical inquiries, and some countries still honor Aristotle as an infallible master of wisdom. The Arabians did not first make him known to the philosophers of modern Europe, but they extended his authority. The acuteness and profoundness which appear in his works, his dogmatic tone, his subtile distinctions, and the technical language, first introduced by him into philosophy, pleased them more than Plato's philosophical doubts and allegorical language. But we find him in the Christian church as early as the time of the Arian controversy; and while the influence of Plato

by cutting off the hand. By the Napoleon code, perjury in criminal cases is punishable by confinement at hard labor for a limited time. If the party accused is sentenced to a severer punishment, the perjurer is to suffer the like. In cases of correctional or police jurisdiction, it is punishable by confinement. Perjury in civil suits, is punishable by civic degradation. By the Prussian code, promulgated by Frederic William in 1794, whoever, whether he appears as a party or as a witness, perjures himself, is to be excluded for ever from his employments, rights and civil profession, to undergo an ignominious exposition as a perjured person, or to be publicly declared such, and, in addition thereto, to be condemned to confinement from one to three years. If the perjury be with a view to profit the perjurer, he is to forfeit a sum quadruple of that which he endeavored to obtain. If the perjury is committed in a capital case, and an innocent person is, in consequence, condemned, the punishment of the perjurer is death; and in cases not capital, the punishment of the perjurer is to be proportioned to the crime of which the innocent person was accused and convicted. By the law of Spain (in 1804), perjury, in civil causes, is punishable with ten years' condemnation to the galleys; and in criminal cases, in which the punishment for the offence charged does not extend to death, public infamy and perpetual condemnation to the galleys. (Johnston's Civil Law of Spain, L. vii, tit. 17, lib. 8, Rec.)

PERKIN WARBECK. (See Warbeck.) PERKINS, doctor Elisha, the inventor of the metallic tractors, was born at Norwich, Connecticut, in January, 1740, and was educated by his father, doctor Joseph Perkins, for the profession of medicine. He was indebted to nature for uncommon endowments, both bodily and mental. In person he was six feet high, and of remarkable symmetry. He possessed extraordinary ability to endure fatigue. His reputation and success as a physician were considerable, but he is principally known by his metallic tractors. These were formed by him from a composition which he discovered after numerous experiments with various kinds of metals, during several years, he having conceived the idea that metallic substances might have an influence on the nerves and muscles of animals, and be capable of being converted to useful purposes as external agents in medicine. They consisted of two instruments, one of the appearance of steel, the

other of brass, and were about three inches in length, and pointed at one end. The manner in which they were applied was, by drawing the points over the affected parts, in a downward direction, for about twenty minutes each time. The complaints in which this operation was found most useful, were local inflammations in general, pains in the head, face, teeth, breast, side, stomach, back, rheumatism, &c. Doctor Perkins procured a patent for his discovery, and the success which it obtained was great, not only in this country, but on the other side of the Atlantic. The professors of three universities in America gave attestations in favor of its efficacy. In Copenhagen, twelve physicians and surgeons, chiefly professors and lecturers in the Royal Frederic's Hospital, commenced a course of experiments, accounts of which were published in an octavo volume. They introduced the term Perkinism, in honor of the discoverer, and asserted that it was of great importance to the physician. In London, a Perkinian institution, as it was called, was established, principally with the view of benefiting the poor by the use of the tractors; and, in a pamphlet giving an account of the institution, it was stated that the communications of cases were from disinterested and intelligent characters from almost every quarter of Great Britain, including professors, regular physicians, surgeons and clergymen. A computation of the cures said to have been effected, presents the number of one million five hundred thousand. It may be well deemed a matter of surprise, after what we have stated, that the tractors have sunk into oblivion; but such is the fact. During the prevalence of yellow fever in New York, in 1799, doctor Perkins went thither for the purpose of testing the merits of a highly antiseptic remedy which he had introduced into practice; but after about four weeks of unremitted assiduity in attending the sick, he took the disease himself, and died at the age of 59 years. He was a man of great liberality of character and of strict honor and integrity. In address and colloquial powers, few of his profession ex celled him.

PERMUTATIONS. (See Combinations.)

PERNAMBUCO; the name generally given to the two cities of Olinda and Recife, in Brazil. The former contains 4000 inhabitants, and is the see of a bishop. It lies about three miles north-east of the latter, in lat. 8° S. It was formerly more populous and flourishing, but since its capture by the Dutch in 1640, its commerce and

nanufactures have deserted it for the latter. (See Recife.)

PÉRON, François, a distinguished French naturalist, born at Cerilly, in 1775, studied in the college at that place, and, in 1792, joined the army on the Rhine. Having been captured at Kaiserslautern, in about a year he was exchanged, and, having lost the sight of one eye, was discharged from the service, and returned to Cerilly, in August, 1795. He then obtained admission into the school of medicine at Paris, where he applied himself closely to his studies, and also attended the lectures of the museum of natural history. When the expedition to the South seas, under captain Baudin, had been projected, Péron, with some difficulty, obtained the situation of zoologist. The vessels appointed for this service, the Geographer and the Naturalist, sailed from Havre, October 19, 1800, and returned to France in April, 1804. They had visited New Holland, and many of the Australian and Polynesian islands; and during the whole of the voyage, Péron seized every opportunity for augmenting the stores of science, by making collections and observations. After his return, he was employed, in conjunction with captain Freycinet, to draw up an account of the voyage, and, with M. Le Sueur, to describe the new objects of natural history which had been procured. Péron died December 14, 1810. His works are, Observations sur l'Anthropologie; and Voyage de Découvertes aux Terres Australes (1807–1816, 3 vols., 4to.); an unfinished History of the Medusæ, fragments of which have been published, and several valuable memoirs on subjects of natural history.

PÉROUSE, LA. (See Lapérouse.) PERPENDICULAR, in geometry; a line falling directly on another line, so as to make equal angles on each side; called also a normal line. These lines may be straight lines or curves. A plane is perpendicular to another plane, if a line drawn on one of them, perpendicular to the line of intersection, forms right angles with a perpendicular line on the other plane drawn to the same point. (See Plumb Line.) A vertical line is one perpendicular to a horizontal line (a line parallel to the surface of calm water), so called because it passes from our vertex or zenith (q. v.) down to the nadir (q. v.), so that the vertical line is a particular kind of perpendicular line.

PERPETUAL MOTION; a motion which is supplied and renewed from itself, without the intervention of, external causes. 3

VOL. X.

The problem of a perpetual motion consists in the inventing of a machine which has the principle of its motion within itself; and numberless schemes have been proposed for its solution. The difficulty is, that the resistance of the air, the friction of the parts of the machine, &c., necessarily retard, and finally stop, the motions of machines, and therefore seem to render perpetual motion an impossibility. Attempts have recently been made to produce a perpetuum mobile, by means of galvanism; a metallic bar, being placed between two dry galvanic columns, is alternately attracted by each column.

PERPETUITY, in the doctrine of annuities, is the number of years in which the simple interest of any principal sum will amount to the same as the principal itself; or it is the number of years' purchase to be given for an annuity which is to continue for ever; and it is found by dividing £100 by the rate of interest agreed upon: thus, allowing 5 per cent., the perpetuity is £10 100 – 20...

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PERPIGNAN; a city of France, capital of East Pyrenees, about a league from the Mediterranean sea; lon. 2° 54′ E.; lat. 42° 42′ N.; population, 15,350. It is a place of strength, and accounted one of the keys of the kingdom, on the side of Spain. It is mostly ill built and gloomy. The trade consists in corn, wool, iron and wine. The manufactures are woollen and silk.

PERRAULT. Of four brothers of this name, who lived during the reign of Louis XIV, the most known are Claude (born 1613, died 1688), a physician, naturalist and architect, from whose designs the cel ebrated façade of the Louvre (q. v.) and the observatory at Paris were built; and Charles (born 1633, died 1703), a man of erudition, but of little taste, whose verses have not outlived his day. Colbert availed himself of their assistance in founding the French academy of art, of which Charles was the librarian. His poem Le Siècle de Louis le Grand, which he read before the academy in 1687, gave rise to the famous controversy on the comparative merits of the ancients and moderns. In his Parallèle des Anciens et Modernes (1688—96), in the form of a dialogue, be maintains that the moderus have carried art and science, which were in a state of infancy among the ancients, to the highest perfection, and have excelled them in their works. This opinion was warmly attacked by Boileau, and zealously defended by Fontenelle and Hudart de la Motto. Perrault was also author of Les