they could long before foretell their places and relative positions."[1] He therefore lost no time in procuring a copy of the Ephemerides of Stadius in order to satisfy his curiosity as to astronomical matters; and not content with the meagre information he could get from this book, he very soon made up his mind to go to the fountain-head, and at the end of November in the same year he invested two Joachims-thaler in a copy of the works of Ptolemy, published at Basle in 1551. This copy is still in existence, and may be seen in the University Library at Prague; there are many marginal notes in it, and at the bottom of the title-page is written in Tycho's own hand that he had bought the book at Copenhagen on the last day of November for two thaler. This book contained a Latin translation of all the writings of Ptolemy except the Geography, the Almegist being in the translation of Georgios from Trebizond. The study of this complete compendium of the astronomy of the day must have given the youthful student enough to do; indeed, it may well be doubtful whether he was at that time able to master it.
Tycho remained at Copenhagen for three years, chiefly occupying himself with mathematical and astronomical studies. We are not acquainted with any details as to this period of his life; all we know is that he formed an intimate friendship with one of the professors of medicine, Hans Frandsen, from Ribe, in Jutland (Johannes Francisci Ripensis), and especially with Johannes Pratensis, a young man of French extraction, who also afterwards became professor of medicine.[2] Jörgen Brahe now thought that the time had come to send his nephew to a foreign uni-
