him to Tycho.[1] Within a few days some preliminary arrangements were made with regard to the distribution of work between the various assistants. Tycho's younger son, Jörgen, was to have charge of the laboratory; Longomontanus had the theory of Mars in hand; Kepler at first had to put up with the promise of the next planet which was taken up, but afterwards Mars was intrusted to him, as he was particularly eager to attack this most difficult planet, while Longomontanus undertook the lunar theory.[2] But though Tycho was most cordial to Kepler, he did not enter very much into learned discourses, so that Kepler had often to coax him into answering some question while they were at table. He had a feeling that he was not looked upon as a man of recognised scientific standing, but merely as an ordinary assistant to the world-famed Tycho Brahe, and yet he felt that he ought to have full access to the great treasure of observations which Tycho possessed. In a document which Kepler drew up for the information of his friends,[3] he remarks that Tycho had hitherto, by the magnitude of his undertakings, been prevented from discussing his observations, and now that old age was approaching and soon would enervate him, he would hardly be able to undertake that great work himself. If the journey from Gratz was not to have been made in vain, either Tycho should allow him to copy the observations, which he doubtless would refuse, since they were his treasure to which he had devoted all his life, or he should admit Kepler to a share in the working out of the results from them. And the Emperor should do as King Alphonso had done, and associate others with Tycho. He himself ran the risk of losing his post at Gratz, for if Tycho took offence at some-
