*$ 136, 13?] Kepler s Rarlv Astronomical M'ork 181 



deal of leisure, which he spent with characteristic energy 

 in acquiring as thorough a knowledge as possible of 

 astronomy, and in speculating on the subject. 



According to his own statement, "there were three 

 things in particular, viz. the number, the size, and the 

 motion of the heavenly bodies, as to which he searched 

 zealously for reasons why they were as they were and not 

 otherwise " ; and the results of a long course of wild 

 speculation on the subject led him at last to a result with 

 which he was immensely pleased a numerical relation 

 connecting the distances of the several planets from the 

 sun with certain geometrical bodies known as the regular 

 solids (of which the cube is the best known), a relation 

 which is not very accurate numerically, and is of absolutely 

 no significance or importance.* This discovery, together 

 with a detailed account of the steps which led to it, as well 

 as of a number of other steps which led nowhere, was 

 published in 1596 in a book a portion of the title of which 

 may be translated as The Forerunner of Dissertations on 

 the U?iiverse, containing the Mystery of the Universe, 

 commonly referred to as the Mysterium Cosmographicum. 

 The contents were probably much more attractive and 

 seemed more valuable to Kepler's contemporaries than 

 to us, but even to those who were least inclined to attach 

 weight to its conclusions, the book shewed evidence 

 of considerable astronomical knowledge and very great 

 ingenuity ; and both Tycho Brahe and Galilei, to whom 

 copies were sent, recognised in the author a rising 

 astronomer likely to do good work. 



137. In 1597 Kepler married. In the following year the 

 religious troubles, which had for some years been steadily 

 growing, were increased by the action of the Archduke 

 Ferdinand of Austria (afterwards the Emperor Ferdinand II.), 

 who on his return from a pilgrimage to Loretto started a 



* The regular solids being taken in the order : cube, tetrahedron, 

 dodecahedron, icosahedron, octohedron, and of such magnitude that 

 a sphere can be circumscribed to each and at the same time inscribed 

 in the preceding solid of the series, then the radii of t'ie six spheres 

 so obtained were shewn by Kepler to be approximately proportional 

 to the distances from the sun of the six planets Saturn Jupiter, Mars, 

 Earth, Venus, and Mercury. 



