292 HISTORY OF FORMAL ASTRONOMY. 



the sun on his axis, before the invention of the telescope, and his opin- 

 ion that the obliquity of the ecliptic was decreasing, but would, after 

 a long-continued diminution, stop, and then increase again. 2 Nothing 

 can be more just, as well as more poetically happy, than Kepler's pic- 

 ture of the philosopher's pursuit of scientific truth, conveyed by means 

 of an allusion to Virgil's shepherd and shepherdess : 



Malo me Galatea petit, lasciva puella 



Et fugit ad salices et se cupit ante videri. 



Coy yet inviting, Galatea loves 



To sport in sight, then plunge into the groves ; 



The challenge given, she darts along the green, 



Will not be caught, yet would not run unseen. 



We may notice as another peculiarity of Kepler's reasonings, the 

 length and laboriousness of the processes by which he discovered the 

 errors of his first guesses. One of the most important talents requisite 

 for a discoverer, is the ingenuity and skill which devises means for rap- 

 idly testing false suppositions as they offer themselves. This talent 

 Kepler did not possess : he was not even a good arithmetical calcula- 

 tor, often making mistakes, some of which he detected and laments, 

 while others escaped him to the last. But his defects in this respect 

 were compensated by his courage and perseverance in undertaking and 

 executing such tasks ; and, what was still more admirable, he never 

 allowed the labor he had spent upon any conjecture to produce any 

 reluctance in abandoning the hypothesis, as soon as he had evidence 

 of its inaccuracy. The only way in which he rewarded himself for his 

 trouble, was by describing to the world, in his lively manner, his 

 schemes, exertions, and feelings. 



The mystical parts of Kepler's opinions, as his belief in astrology, his 

 persuasion that the earth was an animal, and many of the loose moral 

 and spiritual as well as sensible analyses by which he represented to 

 himself the powers which he supposed to prevail in the universe, do 

 not appear to have interfered with his discovery, but rather to have 

 stimulated his invention, and animated his exertions. Indeed, where 

 there are clear scientific ideas on one subject in the mind, it does not 

 appear that mysticism on others is at all unfavorable to the successful 

 prosecution of research. 



I conceive, then, that we may consider Kepler's character as con- 

 taining the general features of the character of a scientific discoverer, 



2 Bailly, A. M. iii. 175. 



