PSORIASIS-PTARMIGAN.

Pterodactyl.

PTEROMYS-PTOLEMAIC SYSTEM.

probably to allow the head to fall back to the centre of gravity during flight. The dorsal vertebræ are from 17 to 20 in number. The sacrum is formed by the coalescence of two vertebræ only, as in existing reptiles, and not of many, as in birds and certain extinct saurians. The tail is generally short, an unusual character with saurians; but a species with a long tail occurs at Solenhofen. There are five toes or digits on each foot; the outer finger of the forearm is immensely elongated for the support of a membranous expansion (the impression of which is preserved in some instances); and the other digits of fore and hind feet terminated in long curved claws. The size and form of the extremities shew that the Pterodactyl was capable of perching on trees, of hanging against perpendicular surfaces, and of standing firmly on the ground, when, with its wings folded, it might crawl on all-fours, or hop like a bird.' The famous quarry of lithographic stone at Solenhofen, of Upper Oolite age, has supplied a great variety of these flying lizards; but the largest species have been found in the Secondary beds of this country. In the Upper Greensand, at Cambridge, the remains of a species that must have had a spread of wing of 25 feet across, have been found; and in the Kentish Chalk, another has been met with very little short of this in its dimensions. The various species vary as much in structure as in form, so that the original genus has been lately raised to the position of an order, under the name of PTEROSAURIA, and the species have been arranged under the following genera, characterised principally by the structure of the jaw and teeth: Pterodactylus, in which the jaws are furnished with long slender teeth along their whole length; Ramphorhynchus, with the extremities of the jaws smooth, probably furnished when living with a horny bill, and towards the bases of the jaws having four or five strong teeth; and Dimorphodon, with large strong teeth in front, and small shorter ones behind. Nearly 30 species have altogether been described.

PTEROMYS. See FLYING SQUIRREL. PTEROPODA (Gr. wing-footed), a class of molluscs, having for their only organs of locomotion wing-like fins attached to the sides of the head or neck, one to each side, by which they make their way through the water, flapping them as a bird or an insect does its wings in the air. They are allied to Gasteropoda, but are inferior to them in organisation; and their wings are not at all homologous to the foot of that class. They are hermaphrodite. The head is perfectly distinct in some, but obscurely distinguished from the body in others. Those which have the head most distinct, as Clio (q. v.), have no shell, and form

Example of the Pteropoda (Cleodora pyramidata).

the order Gymnosomata; those with the head indistinct, the order Thecosomata, have a thin external shell, which in some is globular, with slits for the wings to pass through, in some triangular and pyramidal, in some conical, in some slippershaped, &c. All the species are marine; they are small and delicate creatures, very lively and active, always in quest of food, and affording food to fishes and cetaceans. They are found in all parts of the world, some of them in immense numbers in tropical, and some in arctic seas. None of them are common on the British coasts. The genera and species are few.

PTOLEMA'IC SYSTEM of Astronomy, so called from Ptolemy (q. v.), its chief expounder, was originated, however, long before his time, and was, in fact, merely an attempt to reduce to a scientific form the common and primitive notiona concerning the motions of the heavenly bodies. It was implicitly adopted by Plato, Aristotle, Hipparchus, and (with the exception of the Pythago reans, and probably of Pythagoras himself) all the eminent physicists and philosophers of ancient times; passing from them to the Byzantines and Arabs, who, especially the latter, were the means of disseminating it through Western Europe, where it continued to be the universally established doctrine till the 16th century. The primary and fundamental doctrines of this system are that the earth is the centre of the universe, and that the heavenly bodies revolve round it in circles, and at a uniform rate. These notions, which are naturally suggested by the first general aspect of things, hav ing, previous to any accurate observation, established themselves as unquestionable axioms, phenomena which were found, on closer examination, to be. inconsistent with them, were explained by the introduction of additional hypotheses. The belief that the earth is the centre of the universe, was supported by its being in accordance with the relation of the primary elements of which the material world was supposed to be composed. Thus, earth, I the most stable of the elements, held the lowest place, and supported water, the second in order; above water was placed air, and then fire, ether being supposed to extend indefinitely above the others. In or beyond the ether element were certain zones or heavens, each heaven containing an immense crystalline spherical shell, the smallest enclosing the earth and its superincumbent elements, and the larger spheres enclosing the smaller. To each of these spheres was attached a heavenly body, which, by the revolution of the crystalline, was made to move round the earth. The first or innermost sphere was that of the moon, and after it in order came those of Mercury, Venus, the Sun, Mars, Jupiter, Saturn, and the fixed stars, eight in all. To this system, later astronomers added a ninth sphere, the motion of which should produce the precession of the Equinoxes (q. v.), and a tenth, to cause the alternation of day and night. This tenth sphere, or primum mobile, was supposed to revolve from east to west in 24 hours, and to carry the others along with it in its motion; but the Ptolemaic astronomers do not venture to explain how this was done, although since the axis of motion of the primum mobile was that of the equator, its extremities being the poles of the heavens, while that of the ninth sphere was the axis of the ecliptic, some explanation was certainly necessary. As observations of the heavens became increased in accuracy, it was found that the heavenly motions were apparently not uniform, and this was explained as follows: The accele ration of the sun on one side, and retardation on the other side of his orbit, is only apparent, and

PTOLEMAIS-PTOLEMY IL

results from the earth not being in the centre of
his sphere, C (see fig.), but at E, and consequently
his motion appears to be slowest at P, and

R

quickest at R.

E

B

After said battle of Salamis, in 306 a. C., Artigoms assumed the title of king which example P. and the other successors of Alexander followed In 305 & C., P. opelled Dementing the vallas son of Antigonus, to raise the siege of Rhodes, for which deliverance the Rhodians were so grazial that they worshipped him as a deity, and conferred on ko the title of Boter, or Preserver. The later pat of his reign was peace. He governed his kingdo with an enlightened and virom pobry, and laid the foundation of that progeny vid L enjoyed for many succeeding gebertine encouraged commerce, and soon made Alementos the great mars of the Meinement. Be fonect Literature, science, and art; and not my founded E regression of the planets was accounted for by losopher; Prietes, the decat poe: Zavára e The alternate progression and Muses; Easad the geometana; Stipe dhe pr the famous Museum and Liny i Alinica VE supposing them to move, not directly with their grammarian: Amphine and Apele the pacing also entertained as is cours the ones of the crystallines, but in a small circle, whose centre was with many others. The many if Alicanters wa a fixed point in the crystalline, and which revolved, by P, the base of Amal was the suce on its axis as it was carried round with the latter; subject Two years before the feat sen thus (fig.) the planet was carried round the small in 3 ale docted a true o sen circle ABD, as that circle was carried round PQP Podley Philadelpoms (now supposed to represent the planetary crystal line). its small circle, would thus have a forward, and The planet, while in the outer portion of in the inner portion a backward motion. larger circle was called an eccentric, and the smaller scue rater for the m an epicycle. This theory of eccentrics and epicyspace um dejan satisfied the early astronomers; but further in gation shewed its incompleteness, and in a pics of Spee a va sa times it was found necessary to explain newy mos me my va uga discovered discrepancies by heaping garde meni se i mga lame Kaza a epicycle, till such a complication of the premenstag 1 2 had been produced, as drew from Alfonso I fie fmove to Castile, to whom the P. S. was being explained the va a en to. humorous though somewhat blasphemous remark 18 er at v that if the Deity were now to rescatras the world, he (Alfonso) could give him a few of hints.' As soon as astronomers came to mdemand and test the Copernican Theory the Tea the tray i bratra vi and disorderly pile of hypotens, the mean sentative of the P. S., with had rerred the pan seal of infallibility, and had in ranos form at Beta u visom supreme sway over the mda of men for twenty centuries, at once crumbled to atoma, si mna nós oblivion.

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PTOLEMA'IS. See Aczz.

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day. In 316 C, wu vit se
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It lasted till 301 ac; aina vanera & va
left in possession of sinon the une vun e
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of Cyprus, which, by the sara sathe #tam
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was thereafter attached to toe Rena nagra

PTOLEMY III-PTOLEMY VII.

some have explained the name Philadelphus, as in irony. By his first wife, he had two sons, Ptolemy, his successor, and Lysimachus; and one daughter, Berenice, married to Antiochus II., king of Syria. He reigned from 285 to 247 B. C.

B. C.

of his empire in Syria which had been taken from him. He was declared of age in 196 B.C., and his coronation was performed with unusual splendour. The decree published on this occasion is that which forms the inscription on the far-famed Rosetta Stone (q. v.). P. married Cleopatra in 193 B. C. The affairs of the kingdom were managed by the wise and his counsels, all went well. But the king's ear was virtuous Aristomenes, and so long as P. followed gradually opened to insinuations against his great minister, whom he ultimately compelled to drink poison. While P. was preparing for an expedition against Syria, he was poisoned by some of his followers, whom he had alarmed for their own safety. Under him, Egypt rapidly sank in prosperity, power, and reputation.

PTOLEMY III., surnamed EUERGETES, succeeded his father Philadelphus, and reigned from 247 to 222 He made war on the kingdom of Syria, to avenge the death of his sister Berenice, who had been murdered at the instigation of Laodice, former wife of Antiochus. He overran all the provinces as far south as Babylon and Susa; those on the north and east as far as Bactria and India, offered him homage; and he might have extended the bounds of his empire much further, had not domestic troubles compelled him to hasten back to Egypt. The treasures he brought with him were immense; PTOLEMY VI., PHILOMETOR, reigned from 181 and among the things most highly prized were the to 146 B.C. He was very young at his father's stues of the Egyptian gods which Cambyses had death, and the affairs of the kingdom were therefore ca ried off to Babylon in 525 B. C. It was the directed by his mother Cleopatra, who acted with restoration of these to their proper temples which remarkable prudence and energy. When she died gained for P. the title of Euergetes (the Benefactor). in 173 B.C., the administration fell into the hands His fleets gained many possessions on the coast of two worthless ministers, Eulæus and Lenæus, of the Mediterranean, such as Pamphylia, Cilicia, who, engaging in war with Antiochus, brought the and Ionia, which remained for a long time subject kingdom to the brink of ruin. The young king to Egypt, though the eastern provinces recently con- was taken prisoner by Antiochus (170 B. C.), who quered soon returned to their former sovereign. He hoped to obtain possession of the whole of Egypt; pushed the limits of the home-empire further south, but his younger brother, also called Ptolemy, by conquering part of Ethiopia, where he formed a immediately declared himself sovereign under the colony and centre of trade at Adule. P., like his title of Euergetes II., and took vigorous measures to predecessors, patronised learned men, and encour-defend the kingdom. By the intervention of the aged the study of the arts and sciences. He added so largely to the library of Alexandria that he has by some been called its founder. Among the celebrated men who adorned his court, and kept up the fame of the Museum,' were Apollonius Rhodius, Eratosthenes, and Aristophanes, the grammarian. In his reign, the Egyptian kingdom reached the highest point of military glory, prosperity, and wealth.

PTOLEMY IV., surnamed PHILOPATOR, reigned from 222 to 205 B. C. He was the unworthy son of the preceding king. His reign began in blood by the murder of his mother Berenice, his brother Magas, and his uncle Lysimachus; and it ended in blood by the violent death of his wife Arsinoë. He abandoned himself to debauchery, and intrusted the management of his kingdom to favourites. Antiochus, king of Syria, profiting by his indolence, wrested from him in war some of the provinces which his father had gained; but P., at length roused from his lethargy, took the field in person, and defeated Antiochus at the battle of Raphia. When peace was concluded, P. returned to his capital, and plunged with increased zest into every vice and indulgence. He died in 205 B. C.; his death being hastened by his excesses. He followed the example of his father and grandfather in patronising arts and letters, and cultivated friendship with the Romans, to whom he sent large supplies of grain during the second Punic War, but persecuted the Jews, against whom he had conceived a hatred in consequence of being refused admittance to the sanctuary at Jerusalem by the high priest.

PTOLEMY V., EPIPHANES, succeeded to the throne of his father Philopator, when only five years of age, and reigned from 205 to 181 B.C. His dominions were invaded by Antiochus, king of Syria, and Philip, king of Macedonia, while he was still an infant, and several provinces were severed from the Egyptian kingdom; but the Romans at length interfered, and peace was concluded, it being arranged that P. should marry Cleopatra, daughter of Antiochus, and receive as her dowry those parts

Romans, Antiochus was compelled to return to his kingdom. The brothers reigned jointly for some time, but at length quarrelled, and a civil war ensued in which Euergetes II. was ultimately worsted. The deputies of the Roman Senate, who now did as they pleased in Egypt, arranged that P. Philometor should retain Egypt proper, while Euergetes II. should obtain Cyrene as a separate sovereignty. This settlement substantially held during the lifetime of the former, P. reigned 35 years, and died in 146 B. C., from injuries received by a fall from his horse in a battle against the Syrian usurper Alexander Balas. He is celebrated for his mild and humane disposition, which was strikingly evinced in his magnanimous treatment of his unworthy brother.

PTOLEMY VII., or EUERGETES II., best known by the nickname PHYSCON, or Big-belly, ascended the throne after the death of his brother. He married his brother's sister and widow, Cleopatra (who was also his own sister), and on the same day murdered her infant son P. Eupator, whom she had at first declared king. The history of his reign is one unbroken record of murder and blood, whence his subjects nicknamed him Kakergetes ('the malefactor'). Not only relatives who stood in his way to the throne, but those who opposed his acces sion, and even innocent persons, were butchered with savage cruelty. His private vices and debaucheries were equally infamous. He divorced his wife and sister Cleopatra to marry her daughter by her first husband-his own brother; and when temporarily driven from his throne, 130-127 B. C., by the indignation of his subjects, who chose the divorced Cleopatra in his room, the monster took a diabolical revenge by murdering his own and Cleopatra's son, and sending the head and hands as a present to the latter on her birthday. One is almost ashamed to add that he retained the hereditary taste for learning, and patronised learned men. He himself wrote a work of 24 books, called Memoirs (Hypomnēmata). He reigned from 146 to 117 B. C.

Besides these, there are several Ptolemies of less