loS SECTION PHYSICS. 



at great distances, and many other admirable machines. Now, by 

 reasoning on these things, they will be able with very little trouble, 

 and with very great honour and advantage, to discover their construc- 

 tion ; but even if they do not succeed they will derive the benefit of 

 being able to certify, for their own satisfaction, that that ease of fabri- 

 cation which they had promised themselves from the pre-knowiedge 

 of the true result, is very much less than what they had imagined." 



From the above-mentioned statements it is evident that if we have 

 to thank Holland for having by chance discovered the principle of the 

 telescope, we cannot but render due homage to the genius of the man 

 who thought it out and constructed the instrument with full knowledge 

 of what he was doing. And I may mention that very great was the 

 number of telescopes made by Galileo, and that he himself gave away 

 many, chiefly in compliance with demands for them, to distinguished 

 persons, among whom were : The Grand Duke of Tuscany, Prince 

 D. Antonio de' Medici, the Elector of Bavaria, the Emperor Mathias, 

 Cardinal Borghese, the Queen of France, the Landgrave of Hesse- 

 Cassel, the King of Spain, the King of Poland, Giuliano de' Medici, 

 Cardinal Dal Monte, the Dukes of Acerenza, Professor Wallis [Valseo] 

 of London, and many others. And he, moreover, got reports from 

 Holland, in which it was stated, on the authority of Signer Danielle* 

 Antonini, and of Spinola, that in that country, no one, not even the 

 inventor, could make a telescope that would enlarge an object more 

 than five times. And Constantine Huygens writes to Elia Diodati, in 

 1637, that in Holland magnifying glasses were not yet made with 

 which Jupiter's satellites could be observed distinctly. 



In the meantime, by dint of industry and perseverance, Galileo had 

 succeeded in perfecting his telescopes, so that for some time he 

 obstinately refused to impart to any one the manner in which he made 

 them ; and it was not until his eyesight began to fail him, that he 

 consented to create a manufacturer in the person of Ippolito Mariani, 

 commonly called II Tordo ; whose only authentic telescope now in 

 existence, I am pleased to be able to place before you. It was only 

 about the year 1637 that Francesco Fontana, a Neapolitan, began to 

 make good telescopes. And since I am on the subject of telescopes, I 

 must mention Torricelli, who, after the death of Galileo, having been 

 made mathematician to the Grand Duke, set to work to construct 



