132 ANNUAL REPORT SMITHSONIAN INSTITUTION, 194 



Straight line, parallel to the ecliptic, and to be brighter than the rest of the 

 stars, equal to them in magnitude. The position of them with reference to one 

 another and to Jupiter was as follows : 



E * * O * W 



On the east side there were two stars, and a single one towards the west. The 

 star which was furthest towards the east, and the western star, appeared 

 rather larger than the third. 



I scarcely troubled at all about the distance between them and Jupiter, for, 

 as I have already said, at first I believed them to be fixed stars ; but when on 

 January 8th, led by some fatality, I turned again to look at the same part of 

 the heavens, I found a very different state of things, for there were three little 

 stars all west of Jupiter, and nearer together than on the previous night, and 

 they were separated from one another by equal intervals, as the accompanying 

 figure shows, 



E Q * * * y^ 



At this point, although I had not turned my thoughts at all upon the approxi- 

 mation of the stars to one another, yet my surprise began to be excited, how 

 Jupiter could one day be found to the east of all the aforesaid fixed stars when 

 the day before it had been west of two of them ; and forthwith I became 

 afraid lest the planet might have moved differently from the calculation of 

 astronomers, and so had passed those stars by its own proper motion. I, there- 

 fore, waited for the next night with the most intense longing, but I was dis- 

 appointed of my hope, for the sky was covered with clouds in every direction. 



But on January 10th the stars appeared in the following position with 

 regard to .Jupiter, the third, as I thought, being hidden by the planet. They 

 were situated just as before, exactly in the same straight line with Jupiter, and 

 along the Zodiac .... 



E * * O "^ 



When I had seen these phenomena, as I knew that corresponding changes 

 of position could not by any means belong to Jupiter, and as, moreover, I 



FiGUEE 1. — Part of a page from Galileo's notebook recording the discovery of satellitea 



revolving around Jupiter. 



