$$ i47 is J The Rudolphine Tables 195 



149. After a number of unsuccessful attempts to secure 

 the arrears of his salary, he was told to apply to Wallenstein, 

 the famous Imperialist general, then established in Silesia 

 in a semi-independent position, who was keenly interested 

 in astrology and usually took about with him one or more 

 representatives of the art. Kepler accordingly joined 

 Wallenstein in 1628, and did astrology for him, in addition 

 to writing some minor astronomical and astrological treatises. 

 In 1630 he travelled to Regensburg, where the Diet was 

 then sitting, to press in person his claims for various arrears 

 of salary ; but, worn out by anxiety and by the fatigues of 

 the journey, he was seized by a fever a few days after his 

 arrival, and died on November i5th (N.S.), 1630, in his 59th 

 year. 



The inventory of his property, made after his death, 

 shews that he was in possession of a substantial amount, 

 so that the effect of extreme poverty which his letters 

 convey must have been to a considerable extent due to his 

 over-anxious and excitable temperament. 



150. In addition to the great discoveries already men- 

 tioned Kepler made a good many minor contributions to 

 astronomy, such as new methods of finding the longitude, 

 and various improvements in methods of calculation required 

 for astronomical problems. He also made speculations of 

 some interest as to possible causes underlying the known 

 celestial motions. Whereas the Ptolemaic system required 

 a number of motions round mere geometrical points, centres 

 of epicycles or eccentrics, equants, etc., unoccupied by any 

 real body, and many such motions were still required by 

 Coppernicus, Kepler's scheme of the solar system placed a 

 real body, the sun, at the most important point connected 

 with the path of each planet, and dealt similarly with the 

 moon's motion round the earth and with that of the four 

 satellites round Jupiter. Motions of revolution came in 

 fact to be associated not with some central point but with 

 some central body, and it became therefore an inquiry of 

 interest to ascertain if there were any connection between 

 the motion and the central body. The property possessed 

 by a magnet of attracting a piece of iron at some little 

 distance from it suggested a possible analogy to Kepler, 

 who had read with care and was evidently impressed by 



