perennials, and are propagated by parting the roots in autumn, and are retained in some curious gardens for variety; but their chief merit is for medical purposes: they are powerful astringents, and are used both internally and externally; esteemed very efficacious in hæmorrhagies and other fluxes, and good to heal sore mouths. All the above species are hardy, and thrive in any soil or situation.

POLYGRAM, n. s. Gr. πολυς and γραμμα. A figure consisting of a great number of lines. POLYGRAPHY, n. s. Gr. πολυς and γραφή; Fr. polygraphie. The art of writing in several unusual manners of cyphers; as also deciphering the same.

POLYGRAPHY, POLYGRAPHIA, or POLYGRAPHICE, is formed from the Greek woλu, much, and ypaon, writing. The ancients seem to have been very little acquainted with this art; nor is there any mark of their having gone beyond the Lacedemonian scytals. Trithemius, Porta, Vigenere, and father Niceron, have written on polygraphy. See CIPHER.

POLYGYNIA. See BOTANY.

POLYHALLITE, a mineral in masses of a fibrous texture. Sp. gr. 277. Pearly lustre. Its constituents are hydrous sulphate of lime 28.25; anhydrous sulphate 22-42; anhydrous sulphate of magnesia 2003; sulphate of potassa 27-7; muriate of soda 0·19; red oxide of iron 0.34. It occurs at Ischel in Upper Austria. POLYHEDRON, in geometry, denotes a body or solid comprehended under many sides or planes.

POLYHEDRON, in optics, is a multiplying-glass or lens, consisting of several plane surfaces disposed into a convex form. See OPTICS.

POLYHISTOR (Alexander), an ancient Grecian historian, born at Miletum about A. A. C. 85. He wrote forty-two books on grammar, history, and philosophy, of which only a few extracts are extant in the works of Pliny and other

authors.

POLYHYMNIA, in the Pagan mythology, one of the nine Muses, thus named from woλug, much, and μveta, memory. She presided over history, or rather rhetoric; and is represented with a crown of pearls and a white robe; her right hand in action as if haranguing, and holding in her left a caduceus or sceptre, to show her power.

POLYL'OGY, n. s. Gr. πολυς and λογος. Talkativeness.

POLYM'ATHY, n.s. Gr. moλvc and pavlavw. The knowledge of many arts and sciences; also an acquaintance with many different subjects.

POLYMIGNITE, a new mineral found in the zirconian sienite of Frederickswärns. It is black, brilliant, and crystallised in small prisms, long, thin, with a rectangle, the edges of which are commonly replaced by one or several planes. Sp. gr. 4-806. It scratches glass, but cannot be scratched by steel. Fracture conchoidal, without indications of cleavage. The surface of the crystals has vivid lustre, almost metallic. The fracture also resembles the surface, possessing a brilliancy far beyond what is common in minerals. At the blow-pipe it suffers no change.

-Berzelius; Annales de Chim. xxxi. 405.

POLYMNESTOR, a king of the Thracian Chersonesus. He married Ilione, Priam's eldest daughter; and, for the sake of the treasure with which he was entrusted by Priam during the siege of Troy, he murdered Polydorus. The fleet in which the victorious Greeks returned, together with their Trojan captives, among whom was Hecuba, stepped on the coasts of Thrace, where one of the female captives discovered the body of Polydorus, whom Polymnestor had thrown into the sea. The dreadful news was communicated to Hecuba his mother, who, to revenge her son's death, called out Polymnestor; when the female captives, rushing on him, put out his eyes with their pins, while Hecuba murdered his two children, who had accompanied him. Euripedes says that the Greeks condemned Polymnestor to be banished into a distant island for his perfidy; but Hyginus relates the story differently, and tells us that, when Polydorus was sent to Thrace, Ilione his sister took him instead of her son Deiphilus, who was of the same age, being afraid of her husband's cruelty The monarch, unacquainted with the imposition, looked upon Polydorus as his own son, and treated Deiphilus as her brother. After the destruction of Troy, the conquerors wished the house and family of Priam to be extirpated, and therefore offered Electra the daughter of Agr memnon to Polymnestor, if he would destroy Ilione and Polydorus. He accepted the offer. and despatched his own son Deiphilus, whom he took for Polydorus. Polydorus, who passed as the son of Polymnestor, consulted the oracle, and being informed that his father was dead, he mother a captive in the hands of the Greeks, and his country in ruins, he communicated the aswer to Ilione, who told him what she had done to save his life, upon which he avenged the pe fidy of Polymnestor by putting out his eyes.

POLYMNIA, in botany, a genus of the poly gamia necessaria order, and syngenesia class of plants; natural order forty-ninth, composite. The receptacle is paleaceous; there is no pap pus; the exterior calyx is tetraphyllous, or pe taphyllous; the interior decaphyllous, and coff posed of concave leaflets.

POLYNESIA is a name given by modem geographers to various groupes of islands in the Great Pacific Ocean, situated east of the Asiatic Islands and AUSTRALASIA (which see), and en both sides the Equator.

Hence they are sometimes divided into Northern and Southern Polynesia. The meridian of 130° E. long. separates these islands from the Asiatic Archipelago; and nearly from the shores of Japan, a line extending to the E. to about 125° of W. long., forms the eastern confines to the fiftieth parallel of S. lat. by which they are bounded on that side. Polynesia thus stretches through an extent of about 5100 miles from north to south, and 3600 from east to west. Besides an indefinite number of detached islands, this space includes the following principal groups :

:

NORTH OF THE EQUATORIAL LINE.

1. Pelew Islands,

2. Carolines,

3. Ladrones,

4. Sandwich Islands,

5. Minor Islands,
6. Friendly Islands.

SOUTH OF THE EQUATORIAL LINE.

7. Navigator's Islands,

8. Georgian Islands,

9. Society Islands,

10. Marquesas,

11. Washington Islands,
12. Minor Islands.

Almost all these groupes engage our separate attention in their alphabetical places; but the Minor' islands on both sides of the line, and the Georgians will require some notice in this place.

The Minor islands in the Northern Pacific may be thus traced:-Commencing on the northwest, we meet with Rica de Plata, Rica de Oro, and the groups called Guadalupa and Malabriga. To the south-east of these are Dicierta, Comitra, Lamira, St. Bartholomeo, Gasper Rico, Brown's Range, Piscadores, Calvert's Islands, St. Pierre, Barbadoes, Pit Isle, Matthew's Island, and Christmas Island. This last was discovered by captain Cook on the 24th of December, 1777. The Russian commander, Von Kotzebue, has also lately disclosed two chains of islands, stretching nearly north and south, situated principally between 6° and 12° of lat., and be tween 167° and 173° of E. long. from Greenwich. The eastern chain he calls Radack, and the western Ralick. Each of them contains several islands, but present no remarkable fea

ures.

The Georgian Islands are a groupe that includes OTAHEITE, EIMEO, Tapua-manu, and Tetaroa. For an account of the two former see the alphabetical places. About fourteen leagues west of the harbour of Talu, in Otaheite, is Tapua manu, five or six miles long, and rising in the centre to a peak, with a double summit. It abounds with cocoa-nut trees, but the population is small. Within ten leagues of Matavai, and enlosed with a reef of coral rocks, there are a number of low islets, called Tetaroa, belonging to the king of Otaheite, and which supply this island with fish, in exchange for bread-fruit. A conspicuous island, called Maitea, is situated nearly twenty leagues east of Otaheite; and is only a few miles in circumference. Its northern side is too precipitous to be inhabited, but the declivities in the southern part are more gentle,

and the country populous, This is enclosed on the cast by a coral reef, and is occasionally visited by canoes from Otaheite, which barter for pearls. Society presents a very different aspect, both in these and the Society Islands, from that which it exhibited a few years ago, the labors of the missionaries having resulted in the formal renunciation of idolatry with its superstitious customs and practices in Otaheite, and eight of the other islands. Infanticide has been abolished; the practice of murdering prisoners of war renounced; the suppression of many pernicious amusements effected; and a reception of Christianity avowed. The erection of numerous places for Christian worship, and the establishment of schools, have been the necessary consequences, together with a general observance of the Christian sabbath.

The Minor islands scattered over the Southern Pacific are Byron's Island, situated near the equator; St. Augustine's, several degrees southwest of it: north-west of these, Solitary Island; and, between the Equator and the Georgian archipelago, Penrhyn, and some other small rocky islets. There are also several islands on the south side of this group, among which are Hood's, Gloucester, Osnaburg, and High Islands. Further east, and stretching to the American coast, S. J. Baptista, Oparo, Tubouai, and Pitcairn's Islands, with Ducie's Isle, and Easter Island. The most interesting of these are Tubouai, Pitcairn's, and Easter Islands. On Tubouai, the mutineers of the Bounty attempted to form a settlement after they left Otaheite in 1789, but the hostility of the natives compelled them to seek another asylum, which they afterwards found on PITCAIRN'S ISLAND, which see. See also EASTER ISLAND.

The language throughout all the Polynesian Isles is so nearly similar that the natives can easily understand each other; and, in the whole of the dialects spoken from New Zealand to the Marquesas, and from the Sandwich Islands to Easter Island, scarcely a term occurs which, it is said, cannot be found in the various dialects of the Malay language. It is difficult to account for this similarity, unless we suppose all these people to have sprung from the same stock. Yet it is remarkable that the prevailing trade wind, which greatly facilitates the passage westward, renders it so difficult in the direction in which these people are supposed to have spread, that it seems only possible to have been accomplished during the season of the variable winds, when tempests have been known to drive the existing inhabitants so far to sea in their canoes as to render their return impracticable. Thus, in the hands of nature, or rather Nature's Almighty God, to scatter the feathery seed of plants, and rear up the coral rock from the depths of the ocean to receive it; or carry thither the floating waste of an older world, and, finally, man, are operations alike easy-while the storm by which the feeble canoe is driven from all that is dear to its possessors, is made to subserve some mighty plan of Providence, and to spread universal civilisation.

POLYNICES, the son of (Edipus by his mother Jocasta. See EIFOCLES, JOCASTA, and (EDIPUS.

POLYPETALOUS. See BOTANY. POLYPHEMUS, in fabulous history, a celebrated Cyclops, king of all the Cyclops in Sicily, the son of Neptune and Thoosa the daughter of Phorcys. He was a monster of great strength, very tall, and had but one eye in the middle of the forehead. He ate human flesh, and kept his flocks on the coast of Sicily, where Ulysses, at his return from the Trojan war, was shipwrecked. Ulysses, with twelve of his companions, was seized by the Cyclops, who confined them in his cave, and daily devoured two of them. Ulysses would have shared the same fate, had he not intoxicated the Cyclops, and put out his eye with a firebrand when he was asleep. Polyphemus was awakened by the sudden pain, and stopped the entrance of his cave; but Ulysses escaped, by creeping between the legs of the rams of the Cyclops as they were led to feed on the mountains. Polyphemus became enamoured of Galatæa; but his addresses were disregarded, and the nymph shunned his presence. The Cyclops, when he saw Galatea preferred Acis, crushed his rival with a piece of broken rock.

POLYPHONISM, n. s. Gr. πολυς and φωνη, sound. Multiplicity of sound.

The passages relate to the diminishing the sound of his pistol, by the rarity of the air at that great ascent into the atmosphere, and the magnifying the sound by the polyphonisms or repercussions of the rocks and caverns. Derham.

POLYPODIUM, in botany, male fern, a genus both of the natural and artificial orders of filices, belonging to the cryptogamia class of plants. The fructifications are in roundish points,

scattered over the inferior disc of the frons or leaf. There are sixty-five species, of which the most remarkable are these:

1. P. filix mas, common male fern. This grows in great plenty throughout Britain, in woods and stony uncultivated soils. The greatest part of the root lies horizontally, and has a great number of appendages, close to each other in a vertical direction, while a number of small fibres strike downwards. The leaves are a cubit high, and grow in circular tufts. They are at first alternately pinnate, the pinnæ increasing in size from the base towards the middle, and afterwards gradually decreasing upwards to the summit of the leaf. These pinna are again pinnatifid, or subdivided almost to the nerve into obtuse parallel lobes, crenated on the edges. The stalks are covered with brown filmy scales. The fructifications are kidney-shaped, and covered with a permanent scaly brown, surrounded with a saffron-colored elastic ring. This fern has nearly the same qualities, and is used for most of the same intentions, as the pteris aquilina. They are both burnt together for the sake of their ashes, which are purchased by the soap and glass-makers. In the island of Jura are exported annually £150 worth of these ashes. Gunner relates, in his Flor. Noveg., that the young curled leaves, at their first appearance out of the ground, are by some boiled and eaten like asparagus: and that the poorer Norwegians cut off those succulent lamina, like the nails of the finger at the crown of the root, which are bases of the future stalks, and brew them into

beer, adding thereto a third portion of malt, and in times of great scarcity mix the same in their bread. The same author adds that this fern cut green, and dried in the open air, affords not only an excellent litter for cattle, but, infused in hot water, becomes no contemptible fodder to goats, sheep, and other cattle, which will readily eat and sometimes grow fat upon it: a circumstance well worth the attention of the inhabitants of the Highlands and Hebrides, as great numbers of their cattle, in hard winters, frequently perish for want of food. But the anthelmintic quality of the root of the male fern is that for which it is chiefly to be valued. See MEDICINE.

2. P. oreopteris, and 3. thelypteris, are chiefly remarkable because they have been cofounded by English botanists with the above species. The oreopteris has a large scaly root, wrapped and tied together with small strong fibres, not to be separated without difficulty. The fructifications are on the margins, both when young and old, and never run into one another: the lobes are oval and plain. It is four times as large as the thelypteris, and grows in dry woods, moors, or hills, and very seldom near water; which characters are widely different from those of the species with which it has been confounded. It is found in England, and very plentifully in Scotland. See Linnæan Transactions, vol. 1. Lat. polypodium. A

p. 181.

POLYP'ODY, n. s.

plant. Polypody is a capillary plant with oblong jagged leaves, having a middle rib, which joins them to the stalks running through each division.

Miller. A kind of polypody groweth out of trees, though it windeth not. Bacon's Natural Histery. POLYPREMUM, in botany, Carolina fax. a genus of the monogynia order, and tetandra class of plants; natural order twenty-second. caryophilleæ: CAL. tetraphyllous. COR. quadrifd and rotaceous, with its lobes obcordate; the capsule compressed, emarginated, and bilocular.

POLYPUS, n. s. Į Gг.подuñeç; Fr.polag POLYPOUS, adj. Any thing with many roots or feet, as a swelling in the nostrils; a tout concretion of grumous blood in the heart and arteries, &c.: of the nature of a polypus.

If the vessels drive back the blood with too great a force upon the heart, it will produce polypous concretions in the ventricles of the heart, especially when its valves are apt to grow rigid.

Arbuthn

The juices of all austere vegetables, which cogulate the spittle, being mixed with blood in the veins, form polypusses in the heart.

CULE.

The name of hydra was given them by Linnæus on account of the property they have of reproducing themselves when cut in pieces, every part soon becoming a perfect animal. Dr. Hill called them biota, on account of the strong

principle of life with which every part of them is endowed. These animals were first discovered by Leuwenhoek, who gave some account of them in the Philosophical Transactions for 1703; but their wonderful properties were not known till 1740, when Mr. Trembley began to investigate them, or rather till March 1741, when he had satisfied himself that they were real animals. The surprise of Mr. Trembley and others on discovering the true nature of these animals was very great. When Reaumur saw for the first time two polypes formed from one which he had divided into two parts, he could scarcely believe his own eyes; and, even after having repeated the operation 100 times, he said that the sight was by no means familiar to him. On the 18th July, 1741, M. Buffon wrote to Martin Folkes, esq., president of the Royal Society, acquainting him with the discovery of a small insect called a polypus, which is found about the common duckweed; and which, being cut in two, puts forth from the upper part a tail, and from the lower end a head, so as to become two animals instead of one. If it be cut into three parts, the middlemost also puts out from one end a head, and from the other a tail, so as to become three distinct animals, all living like the first, and performing the various offices of their species.' In March 1742 Mr. Folkes gave an account of these animals to the Royal Society. They were soon after found in England: after which no further doubt remained concerning their reality. The strange properties recorded of this animal, though very surprising, are, however, none of them peculiar to it alone. The Surinam toad produces its young, not in the ordinary way, but in cells upon its back. Mr. Sherwood has discovered the small eels in sour paste to be without exception full of living young ones. And, as to the most amazing of all its properties, the reproduction of its parts, the crab and lobster, if a leg be broken off, always produce a new one; and Messrs. Bonet, Lyonet, Reaumur, and Folkes, have all found by experiment that several earth and water worms have the same property, some of them even when cut into thirty pieces. The urtica marina, or sea-nettle, has been also found to have the same; and the sea-star fish, of which the polype is truly a species, though it had long escaped the searches of the naturalists, was always well known by the fishermen to have it also. The general character of the polype is, that it fixes itself by its base; is gelatinous, linear, naked, contractile, and can change its place. The month, which is placed at one end, is surrounded by hair-like feelers. The young ones grow out from its sides; but in autumn it produces eggs from its sides. There are seven varieties.

1. P. nastaticus, or hydra Anastatica, the clustering polype, forms a group resembling a cluster, or rather an open flower, supported by a stem, which is fixed by its lower extremity to some of the aquatic plants or extraneous bodies in th water; the upper extremity is formed to eight or nine lateral branches, perfectly similar to each other, which have also subordinate branches, whose collective form much resembles that of a leaf. Every one of these assemblages is composed of one principal branch

or nerve, which makes the main stem of the cluster an angle somewhat larger than a right one: the smaller lateral branches proceed from both sides of this nerve, and these are shorter the nearer their origin is to the principal branch. There is a polype at the extremity, and others on both sides of the lateral twigs, but at different distances from their extremities. They are all exceedingly small, and bell-shaped, with a quick motion about the mouth, though it is impossible to discern the cause of it. See ANIMALCULE, and PULEX.

2. P. fuscus has frequently eight arms several times longer than the body.

3. P. griseus is of a yellowish color, small towards the bottom, and has generally about seven long arms. The fuscus, griseus, and viridis, are those on which the greatest number of experiments have been made; and their shapes are so various that it is not easy to describe them. They are generally found in ditches. Whoever has carefully examined these when the sun is very powerful, will find many little transparent lumps of the appearance of a jelly, the size of a pea, and flatted upon one side. The same kind of substance is likewise met with on the under side of the leaves of plants which grow in such places. These are the polypes in a quiescent state, and apparently inanimate. They are generally fixed by one end to some solid substance, with a large opening, which is the mouth, at the other; having several arms fixed round it, projecting as rays from the centre. They are slender, pellucid, and formed of a tender substance like the horns of a snail, and capable of contracting themselves into a very small compass, or of extending to a considerable length. The arms are capable of the same contraction and expansion as the body; and with these they lay hold of minute worms and other insects, bringing them to the mouth and swallowing them; the indigestible parts are again thrown out by the mouth. The green polype was that first discovered by Mr. Trembley; and the first appearances of spontaneous motion was perceived by its arms, which it can contract, extend, and twist about in various directions. On the first appearance of danger they contract to such a degree that they appear little bigger than a grain of sand, of a fine green color, the arms disappearing entirely. Soon after he found the griseus, and afterwards the fuscus. The bodies of the viridis and griseus diminish almost insensibly from the anterior to the posterior extremity; but the fuscus is for the most part of an equal size for two-thirds of its length from the anterior to the posterior extremity, from which it becomes abruptly smaller, and then continues of a regular size to the end. These three kinds have at least six, and at most twelve or thirteen arms, though sometimes the griseus is met with having eighteen arms. They can contract themselves till their bodies do not exceed onetenth of an inch in length, and they can stop at any intermediate degree of contraction or extension. They are of various sizes, from half an inch to an inch and a half long; their arms are seldom longer than their bodies, though some have them an inch, and some even eight inches

long. The thickness of their bodies decreases as they extend themselves, and vice versâ; and they may be made to contract themselves either by agitating the water in which they are contained, or by touching the animals themselves. When taken out of the water, they all contract so much that they appear only like a little lump of jelly. The arms have the same power of contraction or expansion that the body has; and they can contract or expand one arm, or any number of arms, independent of the rest; and they can likewise bend their bodies or arms in all possible directions. They can also dilate or contract their bodies in various places, and sometimes appear thick set with folds, which, when carelessly viewed, appear like wings. Their progressive motion is performed by that power which they have of contracting and dilating their bodies. When about to move they bend down their head and arms, lay hold by means of them on some other substance to which they design to fasten themselves; then they loosen their tail, and draw it towards the head; then either fix it in that place, or, stretching forward their head as before, repeat the same operation. They ascend or descend at pleasure in this manner upon aquatic plants, or upon the sides of the vessel in which they are kept; they sometimes hang by the tail from the surface of the water, sometimes by one of the arms; and they walk with ease upon the surface of the water. On examining the tail with a microscope, a small part of it will be found to be dry above the surface of the water, and in a little concave space, of which the tail forms the bottom; so that it seems to be suspended on the surface of the water, on the same principle that a small pin or needle is made

to swim.

When a polype, therefore, means to pass from the sides of the glass to the surface of the water, it has only to put that part out of the water by which it is to be supported, and to give it time to dry, which it always does upon these occasions; and they attach themselves so firmly by the tail to aquatic plants, stones, &c., that they cannot be easily disengaged: they often further strengthen these attachments by means of one or two of their arms, which serve as a kind of anchors for fixing them to the adjacent substances. The stomach of the polype is a kind of bag or gut into which the mouth opens, and goes from the head to the tail. This, in a strong light, is visible to the naked eye, especially if the animal be placed between the eye and a candle; for these animals are quite transparent, whatever their color may be. The stomach, however, appears to more advantage through a powerful magnifier. Mr. Trembley, by cutting one of these animals transversely into three parts, satisfied himself that they were perforated throughout. Each piece immediately contracted itself, and the perforation was very visible through a microscope. The skin which encloses the stomach is that of the polype itself; so that the whole animal, properly speaking, consists only of one skin, in the form of a tube, and open at both ends. No vessels of any kind are to be distinguished. The mouth is situated at the anterior end in the middle between the shooting

forth of the arms, and assumes different appearances according to circumstances; being sometimes lengthened out in the form of a nipple, at others appearing truncated; sometimes the aperture is quite closed, at others there is a hollow; thoug' at all times a small aperture may be dis covered by a powerful magnifier. The skin of a polype, when examined with a microscope, ap pears like shagreen, covered with little grains, more or less separated from each other, according to the degree of contraction of the body. If the lips of the polype be cut transversely, and placed so that the cut part of the skin may lie directly before the microscope, the skin throughout its whole thickness will be found to consist of an infinite number of grains, and the interior part to be more shagreened than the exterior one; but they are not strongly united to each other, and may be easily separated. They even separate of themselves, though in no great numbers, in the most healthy animals of this kind; for, where they are observed to separate in large quantities, it is a symptom of a very dangerous disorder. In the progress of this disorder the surface of the polype becomes gradually more and more rough and unequal, and no longer well defined or terminated as before. The grains fal off on all sides; the body and arms contract and dilate, and assume a white shining color; and at last the whole dissolves into a heap of grains, which is more particularly observed in the green polype.

The skin of the polype is entirely composed of grains, cemented by a kind of gummy s stance; but it is to the grains entirely that the polype owes its color. The structure of the arms is analogous to that of the body; and they appear shagreened when examined by the m croscope, whether they be in a state of contraction or extension; but if very much contracted they appear more shagreened than the body, though quite smooth when in their utmost state of extension. In the green polype the p pearance of the arm is continually varying; and these variations are more sensible towards the extremity of the arm than at its origin, but me scattered in the parts further on. The extrem is often terminated by a knob, the hairs of whic cannot be observed without a very powerful marnifier. They have a remarkable inclination of turning towards the light; so that if that part of the glass on which they are be turned from the light, they will quickly remove to the other. The fuscus has the longest arms, and makes use of the most curious manoeuvres to seize its prey. They are best viewed in a glass seven or eight inches deep, when their arms commonly hang down to the bottom. When this, or any other kind is hungry, it spreads its arms in a kind of circle to a considerable extent, enclosing in this, as in a net, every insect which comes within the ccumference. While the animal is contracted by seizing its prey, the arms are observed to swe like the human muscles when in action. The no appearance of eyes can be observed in the polype, they certainly have some knowledge of the approach of their prey, and show the greates attention to it as soon as it comes near them. It seizes a worm the moment it is touched by cae