59$ tSXTUftE XLVIII. 



Kepler died in 1630: before his death he had the satisfaction of applying^ 

 his theory to the motions of the satellites of Jupiter, which, as well as the 

 phases of Venus, and the spots of the sun, had lately been discovered in Italy 

 by the telescopic observations of Galileo. This great man, celebrated as 

 well for his theory of projectiles, as for his zealous defence of the Coperaican 

 system, was born at Pisa in J 564, and lived to the age of 7«, fuli of that 

 enthusiasm which made him despise the threats of the Inquisition, and submit 

 patiently to its persecutions. He died in 1642, the year in which Newton 

 was born. 



The invention of logarithms, by Baron Napier, requires to be noticed for 

 its importance to practical astronomy, and the laborious observatiions of 

 Hevelius deserve also to be mentioned with commendation. The discoveries 

 of the form of the ring of Saturn, and of one of his satellites, by Huygens, 

 and of four more, together with the belts and rotation of Jupiter, by Dominic 

 Cassini, were among the early improvements derived from the introduction 

 of the telescope. But, without dwelling on any of these subjects, we hasten 

 to the establishment of the system of gravitation, which has immortalised 

 the name of Newton, and done unrivalled honour to the country that gave 

 him birth. 



The mutual attraction of all matter seems to have been suspected by the 

 Epicureans, but Lucretius never speaks of it in such terms as are sufficient 

 to convey by any means a distinct idea of a reciprocal force. Gregory, ia 

 tlie preface of his Astronomy, has endeavoured to prove that Pythagoras must 

 have been acquainted even with the law of the decrease of gravitation; and 

 Lalande appears to assent to his arguments; but they rest only on the bare 

 possibility that Pythagoras might have deduced an analogy from the tension of 

 chords, which we have no reason to suppose that he even completely understood : 

 and this merely because he fancifully imagined, that there was a correspon- 

 dence between the planets and the strings of a lyre. But the nature of gra- 

 vitation had long been in some measure suspected ; Plutarch had asserted that 

 the moon is retained by it in her orbit, like a stone in a sling; and Bacon, 

 Copernicus, Kepler, Fermat, and Roberval were aware of its efficacy. 

 Bacon, in his Novum organum, calls the tkscent of heavy bodies the motion 



