Ixii 



INTRODUCTORY AND HISTORICAL. 



thirds of its whole amount. His estimated distance of the sun was 3,592 earth's semi-diameters,* 

 but, for the roundness of the number, he adopted 3,600, corresponding to a parallax of 49". 



Godefridus Wendelinus, (Godfrey Wendelin,) a Belgian astronomer, deduced, in 1647, from 

 morning and evening observations of the moon,f the value of the solar parallax as 15" at the 

 outside, or the distance at least 13,740 terrestrial semi-diameters, and fixed 14,656 of these 

 semi-diameters as the most probable value. Kicciolus, rejecting this comparatively small value, 

 arrived at the conclusion,! in 1665, that a value between 28" and 30" could deviate only by 

 very few seconds from the truth. 



Eicciolus gives an interesting list of the successively adopted values, a tabular view of 

 which is as follows, the references having been verified or corrected in all cases where I have 

 access to the originals, which has been generally the case, and in some instances made more 

 complete. 



Distance of the sun from the centre of the earth, expressed in terrestrial semi-diameters. 



Authority. 



Mean 

 distance. 



Authority. 



From Hipparchus' data 



or 



Posidonius, (apogee) 



Ptolemy and Maurolycus 



Clavius, Barocius 



Aibategnitu and Alphonso , 



Lansberg, from data of Albategniui, (apogee) , 



Alfraganus 



Jno. Femelius 



Copernicus, Maginus 



Lansberg, from data of Copernicus, (apogee) 



Michael Neander 



Mtestlinus 



Jno. Offusius 



Tycho and Blancanus 



Longomontanus 



Keppler, [3] in Ephemerides . . . . 

 Stella Martis . . . . 

 Stella Nora . . . , 

 Epit. Astron., (apogee) 

 Tab. Rudolphin . . . 



LansbergittB, (min. eccentricity) . . 



Ism. Bnllialdoi 



Atbanasins Kircherus 



Anton. Maria de Bbeita .... 



Wendelinus 



Galileo 



Marius Betunns 



Langrenus 



Ricciolus 



Ricciolus, (in round numbers) . . . 



1473 

 1379 

 13141 

 1168 

 1168 

 1107 

 7936 

 1215 

 1256 

 1142 



943 

 1160 

 1160 

 1152 

 1150 



1768 

 1768 

 1432 

 3469 

 3381 

 1499 

 1460 

 1906 

 2000 

 14656 

 1208 

 1145 

 3420 

 7327 

 7300 



Plinus, Lib. II., cap XXII. Ed. Siilig I., 130 [1.] 



Almagest, Lib. Id., c. iv. ; V., c. XV. ; Maur. Cosm. 



Clavius, Comm. in Sphajr., p. 215; Barocius Cosmogr. I. -i-. 



Albategn, capp. XXVIII. XXX. L.; Alph. Tabb. 



MS. letters to Ricciolus. 



Alfragani Rud. Astron. ; Different. XXI. 



Cosmotheoria, Lib. I., cap. 7. 



Cop. de Rev. IV., capp. 19, 21 ; Magin. Nov. del. Orb. TUeor. I., 

 cap. 3, II. cap. 24. 



apnd Ricciolum. 



Sphsra Mundi, p. 124. 



Appendix ad Kcppleri Myst. Cosm., p. 168. 



De Dirina Astrorum Facaltatc. 



Tycho, Progymn, (Ed. 1648,) pp. 5, 101, 275, 296, etc. Blancanus, 

 Sphara Muudi, Lib. X., cap. 1. 



\su. Danica. p. ii., pp. 171,231, 241, 298. 

 p. 2. 



Chapter XXX., p. 162. 

 Cap. XVI. 

 Lib. IV., 45, 490. 

 Precept. 141, p. 98. Tabb., p. 92. 

 Proleg. Uranometria ; Lib. II., F.lem. 11. 

 Astron. Fhilolaica, Lib. IV., cap. i. 

 Are Magna Lucia et Umbra. Lib IX., Probl. 9. 

 Radius Sidereomysticus, p. 20, Lib. iv. 



Idea Tabb. Atlant., in Eclips. Lun. ; MS. letters to Ricciolus. 

 Dialog. III., de Syst. Mundi ; Syst. Cosm., p. 266. 

 Apiaria Univ. Phil. Math. ; Apiar. X. 

 US. cited by Ricciolus. 

 ' Aluiag. Xovum I., 731. 



[1] 8*8 LAHSBK'S TraW. d' JUroaomie II. 402, 3. [3] Sua hint remprt Cenwnnu. de die natal, 13. SiUig. PKniu* I, 129. 



[3] RICCIOLI, Lit. Ill, ScAoI. II, p. 111. 



The next attempts at determining the parallax were those of Cassini and Richer. The latter 

 astronomer was sent by the French Academy to South America for purposes similar to those 

 which prompted in our days this present expedition of Lieutenant Gilliss. His observations 

 were published! in 1679, after his return, and his declinations of Mars were compared by 



Ibid., p. 456. 



t RICCIOLI Almagrtum Nowm, I, 109, 731. WHDLEB But. Aitr. p. 457. See also his letter GASSESDI Op.omn. VI, 464. 



f RICCIOLI Aim. Nov., I, 110,731,734. 



Cf. PLCTAKCH depladtit PhOotophorum lib. II, cap. 31. Aristarcrms Propos. 7. 



tutronomiguu etphyxque, fate m fhU de Cay*, par M. RICHEE, Paris, 1679. Also Htm. de PAcad. Roy. da 

 Ijp. 233. 



