A8TROX01CT. 



ASTRONOMY. 



rrtnl phew, M al. that of Daniel During the captivity, tha Jews 

 appear t- hv Imrnt th art, and from that time proUbly , but cer- 

 tainly in the earlier centuries of tha Christian en. became much 

 addicted to it. Several of the more eelehrated writer* on astrology 

 under tha caliphs were Jaws, M Msasahilih, MOMI ban Maimon, 

 Solomon Urchus, whosa almanacs we have mentioned M among tha 

 earliest published, awl many other*. 



In Greece, at lout daring tha classical ages, judicial antrology f..und 

 no reception ; nor do we trace any mark* of It oren in the earlier astro- 

 nomical writan of Out country. The system WM little in harmony 

 with the alleflwfaal mythology which prevailed there; and the orach* 

 aflbrdod perhaps .uffloient nouruliment to tha appetite for tha mar- 

 vellou*. But among tha Roman* astrology WM cultivated with avidity 

 from tha time of tha conquest of Kgyi*, in spite of wveral adicta of 

 tha Mosta. In tha 2nd century the whole world wa astrological, and 

 even Ptolemy WM infected. There U a work entitled Tetrabiblos ' 

 attributed to him, which U entirely devoted to Mtrology ; and though 

 Ha genuineness hu been doubted by eome, merely became it U sstro- 

 lovieal. there appeara no cufflcient reMon to reject it. (See Delambrc, 

 Hut Ast. Anc./ it p. 54S.) 



All the follower* of Mohammed are and have been astrologers. The 

 predestinnrian doctrine* of their lyitem render the transition eay and 

 natural ; for, M we have eeen, the acience of aitmlogy i* baaed upon 

 the notion of the neoeanty of human action*. The establishment of 

 the Moor* in Spain, and the crusade*, caused the introduction or the 

 increased cultivation of the art among the descendant* of the barba- 

 rians who destroyed the Roman empire ; probably the former, for we 

 have no distinct traces either of astronomy or astrology among the 

 northern nations. But the predestinorian principle assumed a modified 

 form more consistent with the belief of the Catholic Church. It wan 

 said that the stars only incline, but cannot compel ; which position, 

 while it left the will free, WM a most convenient explanation of any 

 failure in the prediction*. The Greek and Roman Christian* of the 

 earlier centuries bad in many instances received the whole of astrology ; 

 in others, the modified belief above mentioned. Origen, though he 

 recognises the stars as rational beings, yet, in his ' Philocalia,' contends 

 that the stars neither incline nor compel, but only prophesy or point 

 out what men will do, without exerting any influence. He then trivcx 

 a long and curious argument against their compelling power, without 

 explaining how it does not hold equally against their predicting faculty. 

 St. Augustin (cited by Vossius) argues against astrology altogether. 

 The Church, in its public capacity, condemned the art in the first 

 councils of Braga and Toledo, and in the Decretals (cited by Vossius). 

 The doctrine of astrology was among the errors imputed to the Priscil- 

 lianists. But many cealous Catholics in later time adopted the same 

 opinions, and among them churchmen of the highest rank, such as the 

 Cardinal d'Ailly (died in 14251, who calculated the horoscope of Jesus 

 Christ. The astrology of comets, which ix hardly yet out of date, has 

 even been recognised by a pope: in the 15th century, Calixtu* 111. 

 directed prayers and anathemas against a comet which had either 

 assisted in or predicted the success of the Turks against the Christians. 



The establishment of the Copernican system WM the death of 

 astrology ; and that upon on argument not one bit stronger against It 

 than the preceding systems for it. When it was found that the earth 

 i only one among other planets, it soon came to be reckoned absurd 



by many that our little globe should be of such consequence M to be 

 the peculiar care of the whole system. But why should the principle 

 I mm interference have been preferred to that of the Iwlance of [,,.\MT .' 

 We have lost a charming opportunity of discovering what goes on in 

 other planets. 



The last of the Mtrologers WM Morin. best known M the opponent 

 of Oassendi. The latter had in his youth studied and believed in the 

 art, but hod afterwards renounced and written against it. The former, 

 who worked for thirty years at a book on astrology, and was besides an 

 opponent of the motion of the earth, predicted hi* opponent's death 

 repeatedly, but WM always wrong. He also foretold the death of 

 Louis XIII., with no better succuw. Since his death, which took place 

 in KM, the science ban gradually sunk, and we believe has in no case 

 been adopted by any real astronomer. 



ASTRONOMY signifies the lam of the start, and is applied generally 

 to all that relate* to the motions and theory of the heavenly bodies, oa 

 well M of the earth. If we except general terms, such OH ,>.,. th. >, 

 is perhaps no (ingle word which implies so many and different employ- 

 menu of the human intellect. Y\ e shall therefore confine ourselves 

 a) to a slight sketch of the annals of the science, and a few general 

 ooosidcrationii. {minting out at the same time the articles which should 

 be consulted for further details. 



The work of the astronomer begins in the observatory, where moans 

 are provided for noting the positions of the stars. Of the instruments 

 by which this is done, see the principle and details in the articles 

 l**Tm-><r.sTii<AsTRoNojiir.vi t; ni ; , 1 1 ; CLOCK; PENDULUM; OBSEBVA- 

 TOT; TRANSIT l!MTKUMKNT;ftc. There are two classes of observ 

 the fin*, of known bodies, of which the places are so nearly deteni.inril 

 that no uuestion remains except about quantities less than a second of 

 time, or its corres|wn.ling quantity, fifteen seconds of space [AiroLKJ ; 

 and for this clam the consideration what phenomena shall be observed 

 is made to rest entirely upon the instruments, those phenomena being 

 profaned, for the observation of which the steadiest instrument* can 



be made. These move only in th* meridian, and the star U waited for. 

 The second class of observations, such M those of comets, double stars, 

 and all more Appearance* which require an instrument that can he 

 pointed to any part of the heavens or can be made to follow a rtar, i* 

 performed by telescopes, which are made to revolve with the heaven*. 

 [KyCAToKiAi.] 



The second division of astronomical labour U the department of the 

 mathematician only. The observations M they come from the instru- 

 ment* are subject to all the error* of the Utter, and no perfect 

 instrument* can be constructed. The Iwst circle that can be made is 

 slightly oval ; the best pivot that can be turned will not be truly 

 cylindrical. The question now comes, in what manner to compare 

 different species or set* of observations, so that the discordances them- 

 selves shall point out the quantity and quality of the instrumental 

 errors ; and now from thence to derive the corrections necessary for 

 future observation*. Also, how to choose the time and manner of 

 observation, so that any particular error, whether of instruments or 

 theory, shall be least, if the observer be desirous of avoiding it, or 

 greatest, if he wish to detect and measure it Every-day experience 

 shows that there is no better test of the progress of observation than 

 the discovery of new instrumental errors, provided only the quantities 

 in question become lee* and lea*. The angular error which now set* 

 an observer to work to correct his result, i* lees than the six hundredth 

 part of that which would have been sufficient to annoy Ptal. 

 Hippnrchus. And in speaking of an instrument, we may consider the 

 observer himself M a most material put, on the combined power of 

 whose eye, ear, and judgment, the correctness of the observation 

 : ." It is hardly to be expected that, even under precisely the 

 name circumstances, two observers should note the same phenomenon 

 so M to agree within a small fraction of a second ; and recent 

 ments on phenomena noted with both the eye and hand, have demon- 

 strated the existence of small differences between different observers, 

 attributable only to their different habits of perception or physical 

 constitution. On this point see EQUATION ( PERSONA i \. 



AVI i en observations have been, M nearly M possible, freed from 

 instrumental errors, the next step would be, if we could imagine 

 system of astronomy only in its infancy, with instruments M near 

 perfection as our own, to deduce, by combination of mathematical 

 reasoning and calculation, the real puce* of the stars for some one 

 moment, and the magnitudes and laws of the various motions to which 

 they ore subject, whether periodical or permanent, and whether arising 

 out of the motion of the earth, or out of a proper motion of the stars 

 themselves; and for the solar system, to determine the relative 

 motioiiH and poxitions of the planets anil their satellites, which can 

 only be done by the previous measurement of the earth, and sub- 

 sequent comparison of the results of one observatory with those of 

 another. But these primitive determinations have always been in 

 progress with the instrument, and results have increased in accuracy 

 with the power of observing; so that instead of working afresh for the 

 determination of element*, M they are called, almost the whole of 

 modern astronomy is a process of correction of those which have been 

 previously obtained. This greatly facilitates operations [for the reason 

 of wliiehseclUFFFiiF.XTi s; APPROXIMATION']. The measure- 



ment of the earth itself, and the determination of it* figure, which U 

 the basis of planetary astronomy, so far M ascertaining the actual 

 dimensions of our system is concerned, will be treated M a separate 

 science under the name of OKODESY, though it is a constituent part of 

 astronomy, both on to the methods by which it is carried on, and the 

 objects for which it in undertaken. 



The thin! oVpartment of n-t ronomy, being that which require* the 

 most extended knowledge of mathematics and the highest exercise 

 of thought, in that which goes under the name of phyrieal attnmamy, 

 and consists in the combination of the various phenomena M actually 

 observed, in order to find out what are their physical causes and 

 u.,,. ling to what laws those causes act. It is evident, that without 

 some success in this branch of the science, there can be no jwwer of 

 \nept what arises from the presumption that preceding 

 phenomena have run their whole possible round, so that notfafa 

 happen except a repetition of what hat happened. To a rough view 

 this seem* to be the case, and is so in a great nieomire ; I nit to the 

 instruments of an observatory there appears no such romplet.- 

 dicity. To this head we should refer such questions as those of 



. imx: AiiKHHATiiiN; (imviTATiON. The term ] il>'. 

 noiny is usually applied to invest .igations connected with the latter 

 only; luit I t h' etymology and analogy warrant iU extension to the 

 former. Under this, also, we must place all questions connected with 

 the physical constitution of the various planets, so far as that can 

 become known. Of the great increase whieh the predicting power of 

 astronomy has received since New 1 the motion* of our 



system from the simple law of attraction, them is no need to speak; 

 but we shall notice one peculiar use of that principle, by which the 

 result* of observation arc anticipated, and the first and second 

 divisions of astronomy advanced, while at the saint 1 time the 

 mrntum crutit of the "truth of the prineiplc is furnished. There are 

 many small inequalities of the solar system, which, though not lik*iy 



mixed up as they are with so many others, -. 



certain to be found, if looked for at the time when their effects are 

 most sensible. The results of theory point out that a certain 



