Another argument is drawn from the fourteenth chapter of the Second Treatise, where (on page 84 in this volume) the shadow in the Moon is ascribed to "the rarity of its body, in which the rays of the Sun can find no end wherefrom to strike back again as in the other parts." In the second canto of the Purgatorio, Beatrice opposes that opinion, whence it may be inferred that Dante had learnt better, and he speaks of this again in a later canto (the twenty-second) as a former opinion. This leads to an inference that the Second Treatise was written before 1300. Attention is due also to a passage in the third chapter of the First Treatise (on pages 16 and 17 in this volume), in which Dante speaks of his long exile and poverty. The exile and the wanderings of Dante began after the year 1300. He was befriended by Guido da Polenta in Ravenna, by Uguccione della Faggiola in Lucca, by Malaspina in the Lunigiana, by Can Grande della Scala in Verona, by Bosone de' Raffaelli in Gubbio, by the Patriarch Pagano della Torre in Udine. In 1311, when the Emperor Henry of Luxembourg went to Italy, Dante had some hope of return, which passed away in 1313 when that Emperor died in Buonconvento. Dante remained in exile. In 1321 his patron, Guido Novello da Polenta, sent him on an embassy to Venice, in which he was unsuccessful. The sea way being blocked, he had to return by land, and he was struck by the malaria which caused his death by fever on the 14th of September in that year, 1321. This reference to long exile leads to an inference that the First Treatise was written much later than 1300. But, again, there is a passage in the third chapter of the Fourth Treatise (on page 171 of this volume) that points to an earlier date. Frederick of Suabia is named as the Emperor who held, As far as he could see, Descent of wealth, and generous ways, To make Nobility.