A NEW ASTRONOMY 211 



tween the planetary orbits and the five regular solids, published 

 in 1596 under a title which may be abridged to Cosmographic 

 Mystery. 



The Earth is the circle, the measure of all. Round it describe a 

 dodecahedron, the circle including this will be Mars. Round Mars de- 

 scribe a tetrahedron, the circle including this will be Jupiter. De- 

 scribe a cube round Jupiter, the circle including this will be Saturn. 

 Then inscribe in the Earth an icosahedron, the circle inscribed in it 

 will be Venus. Inscribe an octahedron in Venus, the circle inscribed 

 in it will be Mercury. 



Kepler declared that he would not renounce the glory of this 

 discovery "for the whole Electorate of Saxony." The corre- 

 spondence of the dimensions of this fantastic geometrical con- 

 struction with the distances of members of our solar system is 

 in reality far from close, but both Tycho Brahe and Galileo 

 seem to have been favorably impressed by the book. 



The difficulties of Kepler's position as a Protestant in Gratz 

 led him, after a preliminary visit, to accept an engagement as 

 Tycho' s assistant at Prague. 



The powers of original genius were then for the first time as- 

 sociated with inventive skill and patient observation, and though the 

 astronomical data provided by Tycho were sure of finding their ap- 

 plication in some future age, yet without them, Kepler's speculations 

 would have been vain and the laws which they enabled him to deter- 

 mine would have adorned the history of another century. Brewster. 



In 1602 Kepler succeeded Tycho as imperial mathematician. 

 Most fortunately, also, he secured possession of his chief's great 

 collection of observations, though not of the instruments, a 

 matter of less consequence, since Kepler like Copernicus was a 

 mathematician rather than an observer. To the study of these 

 records he devoted the next 25 years. Among all the planetary 

 observations of Tycho Brahe those of Mars presented the irregu- 

 larities most difficult of explanation, and it was these which, having 

 been originally assigned to Kepler, engrossed his attention for 

 many years, and in the end led to some of his finest discoveries. 



