~~ ot ees, “ Mins 
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 ¢7?-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* 
