1 62 A Short History of Astronomy [Cn. VI. 



Although in scientific importance the Saggiatorc ranks 

 far below many others of Galilei's writings, it had a great 

 reputation as a piece of brilliant controversial writing, and 

 notwithstanding its thinly veiled Coppernicanism, the new 

 Pope, Urban VIII., to whom it was dedicated, was so much 

 pleased with it that he had it read aloud to him at meals. 

 The book must, however, have strengthened the hands 

 of Galilei's enemies, and it was probably with a view to 

 counteracting their influence that he went to Rome next 

 year, to pay his respects to Urban and congratulate him 

 on his recent elevation. The visit was in almost every 

 way a success; Urban granted to him several friendly 

 interviews, promised a pension for his son, gave him several 

 presents, and finally dismissed him with a letter of special 

 recommendation to the new Grand Duke of Tuscany, who 

 had shewn some signs of being less friendly to Galilei 

 than his father. On the other hand, however, the Pope 

 refused to listen to Galilei's request that the decree of .1616 

 should be withdrawn. 



128. Galilei now set seriously to work on the great 

 astronomical treatise, the Dialogue on the Two Chief 

 Systems of the World, the Ptolemaic and Coppernican^ 

 which he had had in mind as long ago as 1610, and in 

 which he proposed to embody most of his astronomical 

 work and to collect all the available evidence bearing on 

 the Coppernican controversy. The form of a dialogue was 

 chosen, partly for literary reasons, and still more because 

 it enabled him to present the Coppernican case as strongly 

 as he wished through the mouths of some of the speakers, 

 without necessarily identifying his own opinions with theirs. 

 The manuscript was almost completed in 1629, and in the 

 following year Galilei went to Rome to obtain the necessary 

 licence for printing it. The censor had some alterations 

 made and then gave the desired permission for printing at 

 Rome, on condition that the book was submitted to him 

 again before being finally printed off. Soon after Galilei's 

 return to Florence the plague broke out, and quarantine 

 difficulties rendered it almost necessary that the book 

 should be printed at Florence instead of at Rome. This 

 required a fresh licence, and the difficulty experienced in 

 obtaining it shewed that the Roman censor was getting 



