A NEW ASTRONOMY 213 



proved that not only did this new theory satisfy the observations, 

 but that no other hypothesis could be made to agree with the obser- 

 vations, as every proposed alternative left outstanding errors, such 

 as it was impossible to ascribe to errors of observation. Kepler had 

 therefore, unlike all his predecessors, not merely put forward a new 

 hypothesis which might do as well as another to enable a computer 

 to construct tables of the planet's motion; he had found the actual 

 orbit in which the planet travels through space. 



In the history of astronomy there are only two other works of 

 equal importance, the book De Revolutionibus of Copernicus and 

 the Principia of Newton. The 'astronomy without hypothesis' 

 demanded by Ramus had at last been produced, and well might 

 Kepler proclaim : 



' It is well, Ramus, that you have run from this pledge, by quitting 

 life and your professorship ; if you held it still, I should, with justice, 

 claim it.' 



Resuming later the tendency of his Cosmographic Mystery, 

 he published in 1619 his Harmony of the World, containing his 

 third law : 



The squares of the times of revolution of any two planets (in- 

 cluding the earth) about the sun are proportional to the cubes of 

 their mean distances from the sun. 



In his delight he exclaims 'Nothing holds me, I will indulge in 

 my sacred fury ; I will triumph over mankind by the honest confession 

 that I have stolen the golden vases of the Egyptians to build up a 

 tabernacle for my God, far away from the confines of Egypt/ 



' What sixteen years ago, I urged as a thing to be sought, that for 

 which I joined Tycho Brahe, for which I settled in Prague, for which 

 I have devoted the best part of my life to astronomical contempla- 

 tions at length I have brought to light, and recognized its truth 

 beyond my most sanguine expectations. It is not eighteen months 

 since I got the first glimpse of light, three months since the dawn, 

 very few days since the unveiled sun, most admirable to gaze on, 

 burst out upon me.' . . . 



Archimedes of old had said " Give me a place to stand on, and 

 I shall move the world." Tycho Brahe had given Kepler the 

 place to stand on, a.nd Kepler did move the world. 



