DISCOVERIES IN THE CELESTIAL SPACES. 707 



possess only very obscure and discrepant data on this subject. 

 It is probable that he recognised the solar spots in April 

 1611, for he showed them publicly at Rome in Cardinal Ban- 

 dini's garden on the Quirinal, in the months of April and May 

 of that year. Hariot, to whom Baron Zach ascribes the dis- 

 covery of the sun's spots, (16th of January, 1610), certainly saw 

 three of them on the 8th of December, 1610, and noted them 

 down in a register of observations ; but he was ignorant that 

 they were solar spots ; thus, too, Flamstead, on the 23rd of 

 December, 1690, and Tobias Mayer, on the 25th of Septem- 

 ber, 1756, did not recognise Uranus as a planet when it 

 passed across the field of their telescope. Hariot first observed 

 the solar spots on the 1st of December, 1611, five months, 

 therefore, after Fabricius had published his discovery. Gali- 

 leo had made the observation that the solar spots, " many of 

 which are larger than the Mediterranean, or even than Africa 

 and Asia," form a definite zone on the sun's disk. He occa- 

 sionally noticed the same spots return, and he was convinced 

 that they belonged to the sun itself. Their differences of 

 dimension in the centre of the sun, and, when they disap- 

 peared on the sun's edge, especially attracted his attention, 

 but still I find nothing in his second remarkable letter of the 

 14th of August, 1612, to Marcus Welser, that would indicate 

 his having observed an inequality in the ash-coloured margin 

 on both sides of the black nucleus when approaching the sun's 

 edge (Alexander Wilson's accurate observation in 1773). The 

 Canon Tarde, in 1620, and Malapertus in 1633, ascribed all 

 obscurations of the sun to small cosmical bodies revolving 

 around it and intercepting its light, and named the Bourbon 

 and Austrian stars* (Borbonia et Austriaca Sidera). Fabri- 

 cius recognised, like Galileo, that the spots belonged to the 

 sun itself;f he also noticed that the spots he had seen vanish 

 all re-appear; and the observation of these phenomena taught 

 him the rotation of the sun, which had already been conjec- 

 tured by Kepler before the discovery of the solar spots. The 

 most accurate determinations of the period of rotation were, 

 however, made in 1630, by the diligent Scheiner. Since the 

 strongest light ever produced by man, Drummond's incan- 



* Delambe, Hist, de VAstronomie moderne, t. i. p. 690. 

 f The same opinion is expressed in Galileo's Letters to Prince Cesi 

 (May 25, 1612); Venturi, P.i. p. 172. 

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