

PTOLEMAIC STRTKM. 



PUBLICANI. 



which ha* expend him to some suspicion of rcci-i\ in;- 

 even in the final scholium of the Prindpla Newton think/i it 

 worth while onoa more to overturn them, u Tyeho Brah<5 h.vl done 

 before him, by droving that if they existed, the oometa could not 

 more u they were known to more. 



The fint heaven U that of the moon ; the second that of Mercury ; 

 the third that of Verm.- ; the fourth that of the Sun ; the fifth that of 

 liars; the >i\lh that of .lupitrr; the Mrenth that of Saturn; the 

 eighth that of all the fixed stars. The heavens of Aristotle end here ; 

 later theorist* odd two more, a ninth, to make the precession of the 

 equinoxe*, and a tenth, or primum mobile, to make the diurnal 

 r. -'v.ilution. All beyond this u the empyreal heaven. 



The office of the primum i '../< is to revolve from east to west in 

 twenty-four hours, carrying with it (but how, we do not know) the 

 whole of the stiWdinate heavens, and making all the phenomena of 

 day and night All the heavenly motions are to be circular and 

 uniform ; this doctrine of the Platonic school is the keystone of the 

 whole system. The poles of the primuni mobile are those of the 

 equator ; but the ninth heaven moves slowly round the poles of the 

 elliptic, carrying the whole system forward in longitude, so as to give 

 the phenomena arising from the precession of the equinoxes. The 

 heaven* of the other heavenly bodies move round with the mean 

 motions of the bodies depending upon them ; and this completes the 

 general view of the system. 



The details of the heavenly motions were for the mathematicians 

 only, who dropped the orbs, and only took such circles out of them 

 as were necessary in the explanation of the inc.: 



Without entering into all the details connected with this explana- 

 tion, which ore rather complicated, and require besides some knowledge 

 of the actual inequalities of the planetary motions, we shall take the 

 two leading circumstances of thugc motions, namely, their not being 

 uniform, and their being sometimes direct, or according to the order 

 of the signs of the zodiac, and sometimes retrograde. One way of 

 explaining the simple irregularity of motion was by supposing the orb 



of the planet to be a sphere, and revolving uniformly, hut not con- 

 centric with the earth. Let the earth be at E, and let the circle r q E 

 revolve uniformly round the centre 0, or let the planet P revolve 

 uniformly in that circle. Consequently, the nearer the planet is to E, 

 the faster it will appear to move, and the contrary, that is, a spectator 

 at E will see the planet moving most slowly when at p, from whence 

 the apparent motion will be accelerated until it arrives at It, and 

 retarded while it returns to r on the other side. The circle P q R is 

 called an eccentric. This hypothesis was a tolerably good representa- 

 tion of the motion of the sun, when r. c was taken in a certain specified 

 ]iro|Nirtiini to the radius c n ; and if the sun had been placed at E, it 

 would have made a sufficient representation of the motions of the 

 pUneti, at least for the earlier periods of observation. But it must be 

 remembered that though an acceleration and retardation would thus 

 ,be established, it would not be precisely that of the planets, though 

 sufficiently near, as remarked, to represent the results of rough 

 observation. 



The mode of obtaining the alternate progressive and retrograde 



n is as follows : Let P be the centre of a circle called an epicycle, 



and let p rev.-lvi. uniformly round the earth at c, while the epicycle 



revolves uniformly round it centre, carrying the planet on its circum- 



whilc the planet revolves uniformly round the epicycle. 



v-le itwlf move fa the direction PQ n, and let the planet 



"" tli- Move in the same direction, or ADD. If then the 



time* of revolution ,,f the planet in the epicycle be sufficiently great 



i red with Hint of the epicycle itself, its retrogradation at D will 

 more than compensate for the progression of the epicycle itself ; that 

 is, the planet will appear to a spectator at c to move In a retrograde 

 direction, when it is in the lower part of the epicycle. But in the 

 njgher part, at A, both motions conspire to make it appear to move 



y. There must consequently be an intermediate point at which 

 the direct motion cease* and the retrograde begins: and near this 



In- pUnct will appear stationary. 



by a complicated, use of these method! that Ptolemy succeed* 



iving a tolerable account of the angular motions known in his 



time; but they fail in placing the planet at the right distance from the 



'1,'h they may place it nearly in the right longitude. We 



imagine that in modern tunes very few persons have taken the trouble 



to make themselves acquainted with the details of this system. These 



maybe 1. .1-1,1, \\ith some trouble, from Delombre's account of tho 

 Syntaxu f Hist, Astron. Am-.'i,but they are explained with much 

 more clearness in Mr. Nan-ion's ' Origin and Progress of Astron 

 London, 18S8. Those who would have Ptolemy's own explanation at 

 less expense of time than is necessary to find it in the Syntax!*, 

 should look at his short tract, npl irxotiftwn r rAuw/i/iw, which 

 was published with the Sphere of Proolua, by Dr. Bainbridge, in 1620. 

 The physical views may be collected, as well as the mathematical ones, 

 from the ' Philolaus,' the fint work of Bouillaud, Amsterdam, 1639. 

 [TBOCIIOIHAI. l'i nvw.] 



PTO8IS is a dropping of the upper eyelid, which the patient cannot 

 by any voluntary exertion raise from before the globe of the eye. In 

 some cases this effect is produced by great inflammatory swelling of 

 the eyelid, with effusion of serum into its tissue ; but in those eases to 

 which tho name of ptoftii is more especially applied, it results from a 

 paralysis of the third pair of nerves [DRAIN, in NAT. HI>T. DIV.J..T 

 only of that branch of it which supplies the levator palpebne muscle, 

 | KYI:, in NAT. HIST. Div.] These are in fact cases of local paralysis, 

 and must be 'treated, without any particular reference to the eye, 

 according to the principles on which paralytic affections in general are 

 managed. [PABAI.TSIS.] 



PTYALIN. An albuminous matter constituting about ono-third of 

 the soluble solids of the saliva. It converts starch into dextrin and 

 sugar. 



PUBERTY (Pubertat), the age at which the period of boyho.nl or 

 girlhood ends, and that of adolescence begins. [AGE.] The word in 

 derived from pitta, which in its primary signification means the down 

 or soft hair that generally begins to grow on young people about that 

 time. Puberty appears at various ages, according to the climate, the 

 circumstances connected with education, and the constitution of the 

 individual. The usual period in this country is f n mi the twelfth to 

 the fourteenth year for females, and from the fourteenth to the six- 

 teenth for males. In the northern parts of the island it is often a year 

 or two later in both sexes. Women in all countries reach the period 

 of puberty one or two years before men ; and the inhabitants of warm 

 before those of cold climates. In the hottest regions of Africa, Asia, 

 and America, girls arrive at puberty at ten, or even at nine years of 

 age ; in France not till thirteen, fourteen, or fifteen ; whilst in Sweden, 

 Russia, and Denmark this period is not attained till from two to three 

 years later. 



Occasionally however an extraordinary precocity exhibits itoelf in 

 the development of both males and females. It is not necessary to 

 dwell at any great length upon instances of exemplification, which 

 may be traced in great numbers in the writings of physiologists who 

 have been curious upon this subject. Those who are desirous of doing 

 so may turn to the 'Journal des Scavans' for 1688, and the ' Philo- 

 sophical Transactions' for 1745; and other instances in Dr. Good's 

 ' Practice of Medicine.' 



The period which commences with puberty is, both as regards the 

 mind and the body, one of the most important epochs of human 

 existence ; for, gays Dr. Copland (' Dictionary of Practical Medicine '), 

 during it the natural development of the sexual organs imports a 

 health and tonic excitement throughout the economy, bringing to 

 their state of full perfection all the organs of the body, and all the 

 manifestations of mind, excepting those that are derived from ex- 

 perience. It is chiefly during this period of life that the mind becomes 

 stored with ideas, derived both from the learning of the ancients, the 

 science of the modems, and the arts and accomplishments of highly 

 civilised life ; and is more particularly and more ardently engaged in 

 decomposing the information thus acquired, and recombining it in new 

 and useful attractive forms. 



PUBLIC HEALTH. [SANITARY LEGISLATION.] 



PUBLIC LIBRARIES. [LIBRABIES.] 



PUBLIC POLICY. This expression sometimes occurs in the 

 reports of law cases, and sometimes the expression " policy of the law " 

 occurs; neither of these expressions has a sufficiently definite meaning. 

 An example will best explain how they are applied. One man may 

 agreo with another for a certain valuable consideration to give up to 

 him some trade, art, or business, and agree that he will not carry on 

 the same within the realm, with the object of securing to the purchaser 

 all the benefit which can be derived from his bargain. If he who has 

 received the money happens to break his contract by commencing the 

 same trade, art, or business in a distant part of the realm, as at the 

 Land's End or Ncwcastle-on-Tync (the original place of business being 

 London), and on action be brought on the contract, it could not be 

 maintained, because the contract itself was againtt jn- which 



would be explained to mean that the public ought not to be dap 

 of a man's services by such an unreasonable contract. Yet if the con- 

 tract were that the trade or business should not be exercised within a 

 certain limited distance of London, the contract would be valid. 

 & PUBLICA'NI. The publican! were a body of persons in the Roman 

 state who farmed the public revenues (vectiyalia), from which -in inn- 

 stance apparently their name i untiir 

 qui publics vectigalia habent conducta," ' Dig.,' 39, tit. 4, s. 1 2.) They 

 were numerous as early as the 6th century of the republic, and they 

 'oiitinucd to exist under the emperors. The publicani formed v 

 societies or partnerships, which had a corporate character. Kacli 

 societas had a uiagistcr, or chief manager, at Itomo, and a deputy 



