4S9 



HIPPARCHUS. 



HIPPO. 



430 



tuuity which was afforded him of perusing the books iu the library of 

 the observatory. After having been a short time at Kingstown, near 

 Dublin, in connection with a scientific commission sent there by the : 

 government, he received, on the recommendation of Professor Airy, 

 the astronomer-royal, an appointment in the observatory of Mr. Bishop, 

 in the Regent's Park, London. Here he commenced iu 1845 the series i 

 of observations which have since been attended with such extraordi- j 

 nary success in the discovery of planets, comets, and stars, previously 

 unobserved. The planets discovered by Mr. Hind, with the dates of j 

 discovery, are as follows:!, Iris, Aug. 13, 1847; 2, Flora, Oct. 18, 

 1847; 3, Victoria, Sept. 13, 1850; 4, Irene, May 19, 1851; 5, Mel- 

 pomene, June 24, 1852; 6, Fortuna, Aug. 22, 1852; 7, Calliope, 

 Nov. 16, 1852; 8, Thalia, Dec. 15, 1852; 9, Euterpe, Nov. 8, 1853; 

 10, Urania, July 22, 1854. Besides these planets, Mr. Hind discovered, 

 on the 29th of July 1846 a comet, which had been seen two hours 

 previously at Rome by De Vice ; and on the 6th of February 1847, 

 another comet, which he observed till the perihelion passage on the 

 24 th of March, when it was bright enough to be visible in strong 

 morning twilight. He has also discovered several stars not previously 





In December 1844 Mr. Hind was chosen a member of the Royal 

 Astronomical Society of London, and was afterwards appointed foreign 

 secretary to the society. In 1846 he was named foreign secretary to 

 the Philomathic Society of Paris, and in 1847 corresponding member. 

 In 1851 he was chosen corresponding member of the Academy pf 

 Sciences of the Institute of Paris. In 1852 the council of the Astro- 

 nomical Society of London awarded him their gold medal ' for hU 

 mtrocomical discoveries, and in particular for the discovery of eight 

 mall planets," and the British government granted him a pension of 

 '2001. a year " for important astronomical discoveries." He is also 

 superintendent of the ' Nautical Almanac,' published by the British 

 government. 



Mr. Hind's scientific investigations have been published chiefly in 

 the ' Transactions ' of the Royal Astronomical Society of London, and 

 iu the ' Comptes Rendus ' of the Academy of Sciences of Paris. In 

 thy course of the last ten or eleven years he has calculated the orbita 

 of a large number of planets and comets, and the results of his labours 

 have appeared in the above-named scientific periodicals. 



Mr. Hind's separate publications are of a popular character. In 

 1 845 he published in the ' Athemeum ' (Aug. 9) an account of ' Recent 

 Comets and the Elements of their Orbits,' and in 1848 a pamphlet 

 ' On the expected Return of the Great Comet of 1264 and 1556.' The 

 following works were published in 1852 : ' An Astronomical Vocabu- 

 lary, being an Explanation of all the Terms in use among Astronomers 

 at the present Day,' 16mo ; ' The Comets : a Descriptive Treatise on 

 those Bodies, with a condensed Account of the numerous modern Dis- 

 coveries respecting them, and a Table of all the Calculated Comets from 

 the earliest Ages to the present Time,' 12mo; ' The Solar System ; a 

 Descriptive Treatise upon the Sun, Moon, and Planets, including an 

 Account of all the recent Discoveries,' 8vo, in the series entitled 

 ' Readings in Popular Literature.' In 1853 he published ' Illustrated 

 London Astronomy, for the Use of Schools and Students,' Svo. These 

 works, cheap and unpretending as they are, contain a large amount of 

 useful information, and entertaining also, for general readers unac- 

 quainted with the principles of astronomy as a science. 



HIITARCHUS. [PisiSTRiTOS.] 



HIPPARCHUS, the first astronomer on record who really made 

 systematic observations, and left behind him a digested body of astro- 

 nomical science. He was born, according to Strabo, at Nicsca in 

 Bithynia, and was alive, as appears from his observations preserved by 

 Ptolemy, in the interval B.C. 160-125 ; but neither the year of his 

 birth nor that of his death is recorded. His astronomical observations 

 were probably commenced in Bithynia, and certainly continued at 

 Rhodes; whence he is called by some authors the Bitbynian, and by 

 others the lihodian, and some even suppose two astronomers of the 

 same name, which is certainly incorrect. He is also supposed to have 

 observed at Alexandria; but Delambre, comparing together such 

 passages as Ptolemy has preserved on the subject, is of opinion that 

 Hipparchus never speaks of Alexandria as of the place in which he 

 resided ; and this opinion of Delambre appears to us to be correct. 



The proper place for an account of the discoveries of Hipparchus is 

 in connection with notice of the ' Syntaxis ' of PTOLEMY, or the Alma- 

 gest, and for this reason, that the loss of the writings of Hipparchus 

 ha* left us without any specific account of his discoveries except that 

 contained in the ' Syntaxit.' And since it is a matter of very great 

 doubt whether Ptolemy made observations himself to any extent, and 

 since it is also certain that he drew his catalogue of stars, and nearly 

 all the observations on which his theory is founded, from Hipparchus, 

 the notice just alluded to would necessarily contain all that is to be 

 said on the subject. We shall therefore here content ourselves with 

 citing the works which Hipparchus is said to have written, and the 

 resume" of his labours given by Delambre. 



The titles of the writings attributed to Hipparchus, on whom 

 Ptolemy has fixed the epithet of ' <f>i\Anorot xal <pt\a\i]9ri5 (' the lover 

 of labour and truth 1 ), have been collected by Fabricius, and are to be 

 found in Weidler, as follows : 1, n/>! ray iirAavi^ avayparpal ; 2, n<pl 

 fuytSair itaJ h^om-^uiiruii 3, De XII. Signorum Ascensione ; 4, Utpi 

 rrjt (cori \CTOS ^vuu'at fiji <rA^n)t mrfiatus ; 6, npl /uqriafov xpivov; 



of these which has come down to us is the last and least important 

 the commentary on Aratus, written probably when Hipparchus was 

 young, since he does not mention any of his subsequent discoveries", 

 and the results of observation are not so correct as those of his cata- 

 logue. This work was published by Peter Victorious, Florence, 1561, 

 and by Petavius in his ' Uranologion,' 1630. Hipparehus also wrote a 

 work, according to Achilles Tatius, on eclipses of the sun ; and there 

 is also recorded a work with the following title : "H -rwv trwava-roXiav 



The following summary is from the preface to Delatnbre's ' History 

 of Antient Astronomy,' in which work will be found the most com- 

 plete account of the labours of Hipparchus. The bias of this historian 

 seems to be, to add to Hipparchus some of the fame which has been 

 generally considered due to Ptolemy, for which he gives forcible 

 reasons : " Let no one be surprised at the errors of half a degree 

 which we attribute to Hipparchus, seemingly with reproach. It must 

 be remembered that his astrolabe was nothing but an armillary sphere, 

 of no great diameter, and with very small subdivisions of a degree ; as 

 well as that he had neither telescope, vernier, nor micrometer. What 

 should we do even now if deprived of these helps, and if we knew 

 neither the refraction nor the true altitude of the pole, on which 

 point, even at Alexandria, and with armillse of every sort, an error of 

 a quarter of a degree was committed ? At this day we dispute about 

 a fraction of a second : they could not then answer for any fraction of 

 a degree, and might be wrong by a whole diameter of the sun or moon. 

 Let us rather think of the essential services which Hipparchus ren- 

 dered to astronomy, of which science he is the true founder. He was 

 the first who gave and demonstrated methods of solving all triangles, 

 whether plane or spherical He constructed a table of chords, of which 

 he made nearly the same use as we now do of our tables of sines. He 

 made many more and much better observations than his predecessors. 

 H established the theory of the sun in such a manner that Ptolemy, 

 263 years afterwards, found nothing to change. It is true that he 

 mistook the inequality of the sun's motion ; but it can be shown that 

 his mistake arose from an error of half a day in the time of the solstice. 

 He himself avows that he may have been wrong by a quarter of a day ; 

 and we may always safely suppose that, without impeachment of an 

 author's integrity, his self-love may halve the error which he is really 

 liable to commit. He determined the first inequality of the moon 

 (the equation of the centre), and Ptolemy found nothing to change iu 

 his result : he gave the mean motion of the moon, and that of the 

 apogee and nodes, in which the corrections made by Ptolemy were 

 slight, and of more than doubtful goodness. He had a sight of the 

 second inequality (the evection) ; it was he who made all the observa- 

 tions necessary for a discovery of which the honour was resarved for 

 Ptolemy ; a discovery which he had not perhaps time to fiuish, but for 

 which he had prepared everything. He showed that all the hypotheses 

 of his predecessors were insufficient to explain the two-fold inequality 

 of the planets ; he predicted that none would be successful which did 

 not combine the two hypotheses of the eccentric and epicycle. He 

 had not the proper observations, because they require more time than 

 the duration of the longest life ; but he made them ready for his suc- 

 cessors. We owe to his catalogue the important knowledge of the 

 retrograde motion of the equinoctial points. We might, it is true, 

 have derived this knowledge from much better observations, made 

 within the last hundred years ; but we should then have had no proof 

 that this motion remains sensibly the same through a long course of 

 ages ; and the observations of Hipparchus, by their number and their 

 antiquity, and in spite of the errors which we are obliged to admit, 

 give important confirmation to one of the fundamental points of 

 astronomy. It is to him that we owe the first discovery of this phe- 

 nomenon. He also invented the planisphere, or the method of 

 describing the starry heavens upon a plane, and of deducing the solution 

 of problems in spherical astronomy by a method often more exact and 

 convenient than that of the globe itself. He is also the father of real 

 geography, through the happy idea of marking the position of towns 

 in the same manner as that of the stars, by circles drawn through the 

 pole perpendicularly to the equator, that is, by latitudes and longi- 

 tudes. His method, by means of eclipses, was for a long time the only 

 one by which the longitude could be determined ; and it is by means 

 of the projection of which he was the author that we now make our 

 maps of the world and our best geographical maps." 



HIPPIAS. [PlSISTRATUS.] 



HIPPO, a Greek philosopher, who is called by some a native of 

 Samos and a follower of Pythagoras, and by others a native of 

 Rhegium, in southern Italy. With regard to his age, some writers 

 have made him a contemporary of Thales, or have placed him even 

 before the age of Thales ; but he evidently belongs to a much Inter 

 time, and was perhaps a contemporary of the comic poet Cratiuus 

 (about B.O. 450), who rediculed him in one of his last comedies; 

 further, Hippo mentions the four elements of the physical philosophy 

 of Empedocles in such a manner that we must infer that he was 

 acquaiuted with the theory of Empedocles. Aristotle ('Metiiphys.' i. 3) 

 does not appear to attach any great value to the philosophical system 

 of Hippo, which in fact was that of Thales, with sundry additions and 



