KEPLER'S LAWS. 307 



quite a modern science. It dates only from the sixteenth 

 century. 



Three great, three brilliant phases, have marked its 

 progress. 



In 1543 Copernicus overthrew with a firm and bold 

 hand, the greater part of the antique and venerable scaf- 

 folding with which the illusions of the senses and the 

 pride of successive generations had filled the universe. 

 The earth ceased to be the centre, the pivot of the celes- 

 tial movements ; it henceforward modestly ranged itself 

 among the planets ; its material importance, amid the 

 totality of the bodies of which our solar system is com- 

 posed, found itself reduced almost to that of a grain of 

 sand. 



Twenty-eight years had elapsed from the day when 

 the Canon of Thorn expired while holding in his falter- 

 ing hands the first copy of the work which was to diffuse 

 so bright and pure a flood of glory upon Poland, when 

 Wiirtemberg witnessed the birth of a man who was des- 

 tined to achieve a revolution in science not less fertile in 

 consequences, and still more difficult of execution. This 

 man was Kepler. Endowed with two qualities which 

 seemed incompatible with each other, a volcanic imagina- 

 tion, and a pertinacity of intellect which the most tedious 

 numerical calculations could not daunt, Kepler conjec- 

 tured that the movements of the celestial bodies must be 

 connected together by simple laws, or, to use his own 

 expressions, by harmonic laws. These laws he under- 

 took to discover. A thousand fruitless attempts, errors 

 of calculation inseparable from a colossal undertaking, 

 did not prevent him. a single instant from advancing 

 resolutely towards the goal of which he imagined he had 

 obtained a glimpse. Twenty-two years were employed 



