A>*Ti:"N'>MY. 



ASTRONOMY. 



bad twin- rwen in the wert, are. o far as their credit goes, conftrma- 



-. : - : i -. - - 



h regard to the astronomy of the Greeks previously to the 

 earlM* extant worka, then ia little to be laid. The Ionian school, 

 founded by Thalm B.C. 000, followed in ucoauion by Anaximander, 

 A t ^j Aauagant, added little or nothing to practical 



Mtroootny. If Thales really predicted the toUl ellipse of the sun, 

 Ecurus], be mu*t hare succeeded in doing no by mean* of 



- 



-... a 

 . 



ear!', ni 



an Sanw,or 



at 18 yean and 10 dan, which produce* 

 alar and lunar eclipse*. The opinion of the 



' motion attributed to Anaximander rents on alender foundation. 

 The nboal of Croton. founded by Pythagoras about the year B.C. 500, 

 and sustained by Philolaus, produced no obwrren, though it certainly 

 adopted the opinion of the earth'* motion. Pythagoras is aaid to have 

 Ant taught that Lucifer and Hesperus, or the morning and the evening 

 tar, are in reality one and the aame planet The following is a liitt of 

 ancient philosophers to whom the i-piiii..ii of the earth's motion has 



attributed: 



I'.. 

 PnOoIaoB. 



rter. 



Nioeta* of Syracuse. 

 Seleucun. 



Cleanthes the Samnite. 

 Leucippui. 

 Ecphantus. 

 Heraclides of Pontus. 

 Aristarchus of Samoa. 



Meton. B.C. 432, introduced the Luni-Solar cycle of nineteen years. 

 In conjunction with Euctemon, he observed a solstice at Athens in the 

 roar B.C. 434. Calippus, B.C. 330, introduced the improvement of the 

 Metonic cycle, known by his name. Eudoxua of Cnidos, B.C. 370, 

 brought into Greece according to Pliny, the year of 365J days, and 

 wrote some worka, one of which exist** in the poetical version of 

 Aratua. 



Pytheas, about the time of Alexander, measured the latitude of 

 Marseille with tolerable accuracy. The work of Aristotle on astro- 

 nomy is lost ; and what is still more to be regretted, that of his 

 dwciple Endemus on the history of astronomy. The poem on the 

 Sphere attributed to Empedocles, B.C. 450, is probably much more 

 modern. 



\\Y now come to the period of history, and of the Alexandrian 

 achool. This article being for reference only, we shall condense as 

 much as possible the principal discoveries of the succeeding astrono- 

 mers, in order of time. This could not be done in the chain of 

 surmises mixed with history which we have just tinixhed, since it is 

 important to avoid confounding what i known with what is only 

 supposed. 



List of astronomers of the Alexandrian school : 



AristylliiK. 



Timocharis. 



Eratosthenes. 



Ooaoa. 



Hipparchus. 



'- 



Theon the Elder. 



Ptolemy. 



Paulus of Alexandria. 



Thoon the Younger. 



Hypatia. 



Pappus. 



Diodoru. 



Theophilus. 



C'yrillua. 



AvtrJyna, B.C. 800. His books are the earliest which are extint in 

 the Greek language on astronomy. They are two : I. On the sphere 

 in motion. 2. On the ruing and netting of the stars. He appears to 

 hare considered the year as exactly 365 days. 



TYmoe&oru and AritlyUut, B.C. 300 (T), made the observations which 

 afterwards enabled Hipparchiu to discover the precession of the 

 equinoxes. 



/;//!</ of Alexandria, B.C. 300. The ' Elements of Euclid ' show 

 that the Greeks of his time had no trigonometry. There is aiit.thrr 

 work attributed to him, entitled ' Phenomena,' which is no more than 

 a treatise on the doctrine of the sphere. 



Arattu of Cilicia, B.C. 281, baa left an astronomical poem, chiefly 

 taken from Eudoxua, and valuable on account of the commentary of 

 Hipparchus. 



Many other ancient writers have also written commentaries on the 

 poem of Aratua. The following list of them U given by De Chales : 



Agesianax. 



Alexander of .Etolia. 

 Alexander of Epheaiu. 

 Antigonns the Grammarian. 

 ApoUoniu* the Grammarian. 

 ApoUonius the Geometer. 

 Aristarchus the Grammarian. 

 ArisUrchu* of Samoa. 

 Ari*tophane. 

 The two Arutylli. 

 Atalus of Rhode*. 

 Bathiu*. 

 Callimachua of Cyrene. 



Callistratus Tenedoa. 



I': ' 



The two Didymi. 

 Eratosthenes. 

 Heliodorus the Stoic. 

 The two Hertnippi. 

 Hipparchus. 

 Niiiiu-niiis Parmenidea. 

 ParmeniscuR. 

 Pyrrhus of Magnesia. 

 Sminthes Thalea. 

 Timotheus Zeno. 



Aritlarduu of Samos, B.C. 280. His work n the magnitude! and 

 distance* of the ran and moon is the first attempt to measure the 

 relative distances of these two bodic, by observing their angular dia- 



tance at the time of half moon. To him also is attributed the opini< <n 

 that the earth revolves round the sun. 



Jtamttko the Egyptian, B.C. 240. Hi- history U lost, but a poem 

 attributed to him remain-. It is a dencription of the heavens, filled 

 with astrology and containing no obaervni 



Okenaof Cyrene, B.C. 240, is said to have observed with some 

 celebrated astrolabes which he erected at Alexandria, win 

 standing till the time of Ptolemy. Various works are attul. 

 lam. for which aee bin I.ilV, in the llioo. l)iv. He observed 

 with a gnomon or with a meridian circle) [ASTROI.ABK] the obliquity 

 of the ecliptic, and the latitude of Alexandria ; and from the latter, 

 and the fact that at Syene the sun was vertical at the summer solstice, 

 he deduced an approximation to the earth's magnitude. His approxi- 

 mation makes a degree to be 700 stadia. A catalogue of stars attri- 

 buted to him (the oldest extant) is probably spurious, but shows that, 

 in and about his time, the method of referring stars to t) 

 and longitudes was not practised. His value of the obliquity f tlm 

 eeliptie 11 part* out of 166 of the whole circumference was n ' 

 Ly Ilip|>archu8and Ptolemy. 



Arrhimtdet of Syracuse, died B.C. 212. He observed solstices, and 

 attempted to measure the sun's diameter. His writings show that 

 trigonometry was a* yet unknown. 



rfluu of Bithynia (f), B.C. 160-125, the greatest of all the Greeks 

 in astronomy. In his youth he wrote a commentary on Aratu.-. I L- 

 discovered the precession of the equinoxes, by comparing his own 

 observations with those of Aristyllus and Timocharis, or others of hii 

 predecessors. He was the first who employed processes analagous to 

 those of plane and spherical trigonometry, for which he constructed a 

 table of chords. He first used right ascensions and declin.r 

 he afterwards abandoned in favour of latitudes and lon^itu.l. If.- 

 suggested the method of referring terrestrial positions to latitude and 

 longitude, and was probably the inventor of the stereographic projec- 

 tion. He determined the mean motion of the sun and of its apogee, 

 the inequality of the sun's motion, and the length of the year, to 

 greater exactness than his predecessors. He found the mean motion 

 of the moon, of her nodes, and of her apogee ; her parallax, ecceni 

 the equation of her centre, and the inclination of her orbit. His 

 observations also led him to suspect another inequality in the moon's 

 motion, which Ptolemy afterwards discovered (the erection). II.- 

 calculated eclipses, and used the results in the improvement, "i tin: 

 ' Elements.' He made one of the first steps towards a correct repre- 

 sentation of phenomena, by nup|>omng the sun to move round the. 

 earth in a circle, the earth not being at the centre. His catalogue of 

 the longitudes and latitudes of 1081 stars was the first at all \\. 

 the name. If Hipjiarehiis hod possessed the pendulum and th 

 scope, fifty years might have enabled his successors to place astronomy 

 in the state in which it stood at the birth of Newton. > 

 his means, his observations are perhaps unequalled. 



After the death of Hipparchua there ia no astronomer of eminence 

 till Ptolemy. Between them we have 



/ffi/mdt of Alexandria, B.C. 146, wrote the 14th and 15th K 

 (lie ' Klcmente of Euclid,' which contain some astronomical propo^-i 



(rrminiii (of Rhodes f) B.C. 70, wrote an introduction to tl 

 phenomena, containing no new discovery. It would seem he watt not 

 on observer. 



Putidimiiit about the same time attempted to verify the men 

 the earth of Eratosthenes. Hi writings are all lost, but many of lii.< 

 opinions are preserved in Cleomedes and Strabo. He n-m i 

 probably he was not the first who did so) the connection of high water 

 with the southing of the moon. 



Thtoduuu* of Bithynia, B.C. 50, left a work on spherical geometry, 

 another on climates, and a thin! n tin: phenomena of day and night. 



.na of Alexandria, B.C. 50, corrected the calendar under Julius 

 Ot me. 



"i left an astronomical description of the heavens. 



MaUi\n, a Roman, A.D. 10, wrote an astronomical and astrological 

 poem. 



Seneca, A.D. 60. His book on natural philosophy contains many 

 pieces of information on astronomical history, but is priiu-ip.illy re- 

 markable for the bold opinions of the author on the nature of cometa. 

 These he declares to be planets, whose laws he predicted . :. 

 day be calculated, and that posterity would wonder how things so 

 simple could have so long escaped notice. 



Menelaiu, A.D. 80, observed at Rome and Rhodes. He has loft three 

 books of spherical trigonometry. 



Theon of Smyrna, A.D. 117 (?) observed at Alexandria. He wrote on 

 astronomy, and mode a collection of astronomical works. His observa- 

 tions are cited by Ptolemy. 



Cleomedt* wrote on astronomy. He certainly lived after Posidonius, 

 but whether before or after Ptolemy is uncertain. He ia usually con- 

 sidered as having lived under Augustus Caesar. 



We must suppose that there wore many real observers between the 

 epochs of Hipparchus and Ptolemy; Lot t'n>m the loss of even their 

 names, and the silence of P: ..;.!:_> Inmself, it is clear that no di' 

 of any importance was made. 



' Alexandria, A.D. 130-150. We must briefly mention his 

 works, his system, and his discoveries. The nafhinaTixr) auvtai 

 mallitntaticuU collection, afterwards called ntyd\ri awrafis, and by the 



