RESEARCHES ON SATURN'S RINGS. 345 



at the following result : The action of Jupiter regulates 

 the movements of rotation of the satellites so that, with- 

 out taking into account the secular perturbations, the 

 time of rotation of the first satellite plus twice the time 

 of rotation of the third, forms a sum. which is constantly 

 equal to three times the time of rotation of the second. 



Influenced by a deference, a modesty, a timidity, 

 without any plausible motive, our artists in the last 

 century surrendered to the English the exclusive privi- 

 lege of constructing instruments of astronomy. Thus, 

 let us frankly acknowledge the fact, at the time when 

 Herschel was prosecuting his beautiful observations on 

 the other side of the Channel, there existed in France 

 no instruments adapted for developing them ; we had 

 not even the means of verifying them. Fortunately for 

 the scientific honour of our country, mathematical anal- 

 ysis is also a powerful instrument. Laplace gave ample 

 proof of this on a memorable occasion when from the 

 retirement of his chamber he predicted, he minutely 

 announced, what the excellent astronomer of Windsor 

 would see with the largest telescopes which were ever 

 constructed by the hand of man. 



When Galileo, in the beginning of the year 1610, 

 directed towards Saturn a telescope of very low power 

 which he had just executed with his own hands, he per- 

 ceived that the planet was not an ordinary globe, with- 

 out however being able to ascertain its real form. The 

 expression tri-corporate, by which the illustrious Floren- 

 tine designated the appearance of the planet, implied 

 even a totally erroneous idea of its structure. Our 

 countryman Roberval entertained much sounder views 

 on the subject, but from not having instituted a detailed 

 comparison between his hypothesis and the results of 



15* 



