5^ PHILOSOPHICAL TRANSACTIONS. [aNNO 1666. 



passing over his body. One of those small stars moving round his body, which 

 are therefore called his satellites, coming between the sun and it, made a small 

 eclipse, appearing on the face of Jupiter as a little round black spot. 



Of a permanent Spot in Jupiter : by ivhich is manifested the Rotation 

 of Jupiter about his own Axis. N" 8, p. 143. 



Besides that transient shadow last mentioned, there has been observed, by 

 Mr. Hook first, (as is mentioned in Number I of these Transactions) and 

 since by M. Cassini, a permanent spot in the disk of Jupiter ; by means of 

 which they have been able to observe, not only that Jupiter turns about his own 

 axis, but also the time of such rotation ; which he estimates to be nine hours 

 and 56 minutes. 



For, as Kepler before conjectured, from the motion of the primitive planets 

 about the sun as their centre, that the sun moved about his own axis, but could 

 not prove it, till by Galileo and Schiner the spots in the sun were discovered ; 

 so it has been thought probable, from the secondary planets moving about 

 Jupiter, that Jupiter is also moved about his axis ; yet till now it has not been 

 evinced by observation that he does so move, much less in what period of time. 

 And the like reason there is to judge so of Saturn, because of the secondary 

 planet discovered by M. Huygens to move about him, though such motion be 

 not yet evinced from observation^ as well as that of the earth, from its atten- 

 dant the moon. 



Of some Philosophical and curious New Books. N" 8, p. 145. 

 Of these it may be sufficient to mention two, viz. 



1 . A narration of the establishment of the Lyncei, an Italian academy, and 

 of their design and statutes : the Prince Cesi being the head of them, who also 

 intended to establish such philosophical societies in all parts of the world, and 

 particularly in Africa and America, to be by that means well informed of what 

 considerable productions of Nature were to be found in those parts. 



2. A book just printed at Oxford, being a catalogue of fixed stars, with their 

 longitudes, latitudes, and magnitudes, according to the observations of Uleg- 

 Beig, a king and noted astronomer, who was great grandson to the famous 

 Tamerlane, and one of his successors in some of his kingdoms. These observa- 

 tions were made at Samarcand, in the year of Christ 1437 : for, not finding the 

 tables of Ptolemy to agree sufficiently with the heavens, he, with great diligence 

 and expense, made observations anew; as Tycho Brahe has done since. It is 

 only a small part of a larger astronomical treatise of his, of which there are 

 several Persian manuscript copies in Oxford. Out of which this is translated 



