320 COSMOS. 



he first directed toward the mountainous parts of the inoor\ 

 and showed how their summits might be measured, while he, 

 hke Leonardo da Vinci and Mosthn, ascribed the ash-colored 

 light of the moon to the reflection of solar light from the earth 

 to the moon. He observed with low magnifying powers the 

 group of the Pleiades, the starry cluster in Cancer, tht Milky 

 Way, and the group of stars in the head of Orion. Then fol- 

 lowed, in quick succession, the great discoveries of the four 

 satellites of Jupiter, the two handles of Saturn (his indistinct- 

 ly-seen rings, the form of which was not recognized), the solar 

 spots, and crescent shape of Venus. 



The moons of Jupiter, the first of all the secondary planets 

 discovered by the telescope, were first seen, almost simulta 

 neously and wholly independently, on the 29 th of December, 

 1609, by Simon Marius at Ansbach, and on the 7tli of Jan- 

 uary, 1610, by Galileo at Padua. In the publication of this 

 discovery, Galileo, by the Niincius Siderius (1610), preced- 

 ed the Mujidus Jovialis (1614) of Simon Marius,*" who had 



on our earth." The comparison is remaiknble, suice, according to Ric- 

 cioli, very exaggerated ideas of the height of our mountains were then 

 entertained, and one of the principal or most celebrated of these ele 

 rations, the Peak of Teneritfe, was first measured trigonometrically, 

 with some degi'ee of exactness, by Feuillee, in 1724. Galileo, like all 

 other observei's up to the close of the eighteenth century, beheved in 

 the existence of many seas and of a lunar atmosphere. 



* I here again find occasion {Cosmos, vol. i., p. 185) to refer to the 

 proposition laid down by Arago : " The only rational and just method 

 of writing the history of science is to base it exclusively on works, the 

 date of whose publication is certain. All beyond this must be confused 

 and obscure." The singularly-delayed publication of the Frdnkische 

 Kalender or Practlca (1612), and of the astronomically important mem- 

 oir entitled " Mundus Jovialis anno 1609 delectus ope perspicilli Bel 

 gici (FebiTiary, 1614)," may indeed have given occasion to the suspicion 

 that Marius had drawn his materials from the Nunclus Sidere7is of Gal 

 ileo, the dedication of which is dated March, 1610, or even from ear 

 lier manuscript communications. Galileo, irritated by the still remem- 

 bered lawsuit against Balthasar Capra, a pupil of Marius, calls him the 

 usurper of the system of Jupiter, " Usurpatore del sistema di Giove," 

 and he even accuses the heretical Protestant astronomer of Gunzen- 

 hausen of having founded his apparently earlier observation on a con- 

 fusion between the calendars. " Tace il Mario di far cauto il lettore, 

 come essendo egli separate della chiesa nostra, ne avendo accettato 

 i'emendatione Gregoriaua, il giorno 7 di gennaio del 1610, di noi Cat- 

 tolici (the day on which Galileo discovered the satellites) e I'istesso, 

 che il di 28 di Decembre del 1609, di loro ei^tici, e questa h tutta la 

 precedenza delle sue finte osservationi" (Venturi, Memoire e Lettere di 

 G. Galilei, 1818, Part i., p. 279 ; and Delambre, Hist, de VAstr. Mod., 

 t. i., p. 696). According to a letter written by Galileo in 1614 to tha 

 Accademia di Lincei, it would appear that he attempted, somewhat uu- 

 philosophically, to direct his complaint against Marius to the Marches*! 



