408 SEC. 11. ASTRONOMY. 



" any of my predecessors had enjoyed. These facts, Sig. Sarsi, did not take 

 " place in a forest or in a desert, they occurred at Venice, and if you had 

 " been there then you would not have put me down simply as a foster-parent 

 " of the invention. But perhaps some one may tell me that it is no small 

 " help towards the discovery or solution of any problem to be first of all 

 " apprised in one way or another of the truth of its conclusion, and to know 

 " for certain that it is not an impossibility that is being sought after ; and 

 " that, therefore, the information and the certainty that the telescope had 

 " already been made, were of such use to me, that in all probability I should 

 " never have made the discovery without them. To this I answer that the 

 " help given me by the information I received, undoubtedly awoke in me 

 the determination to apply my mind to this subject, and that without it 

 I should very likely never have turned my thoughts in that direction ; but 

 besides this, that I cannot believe that the notice I had had could in any- 

 way render the invention easier; and I say moreover, that to find the 

 solution of a problem already thought out and expressed requires far greater 

 genius than to discover one not previously thought of ; for in the latter 

 case chance can play a great part, while the former is entirely the work of 

 reasoning. We know that the Dutchman, the first inventor of telescopes, 

 was simply a common spectacle-maker, who, handling by chance glasses of 

 various kinds, happened at the same moment to look through two, the one 

 concave, the other convex, placed at different distances from his eyes, and 

 in .this manner he observed the effect which was produced, and thus invented 

 the instrument ; but I, warned by the aforesaid notice, came to the same 

 conclusion by dint of reasoning ; and since it is by no means difficult to 

 follow, I should like to lay it before you. This, then, was niy reasoning ; 

 this instrument must either consist of one glass only, or of more than one 

 glass, it cannot be of one alone, because its figure must either be convex, or 

 concave, or comprised between two parallel superficies, but neither of 

 these shapes alters in the least the objects seen whilst increasing or 

 " diminishing them, for it is true that the concave glass diminishes, and that 

 " the convex one increases them ; but both show them very indistinctly, hence, 

 " one glass is not sufficient to produce the required effect. Passing on to 

 " two glasses, and knowing that the glass of parallel -superficies has no 

 " effect at all, I concluded therefore, that the desired result could not possibly 

 " follow by adding this one to either of the other two. Hence, I restricted 

 " my experiments to combinations of the other two glasses, and I saw how 

 " this brought me to the result. Such was the progress of my discovery, in 

 " which you see of how much avail was the knowledge of the truth of the 

 " conclusion. But Sig. Sarsi, or. others, believe that the certainty of the 

 " result affords great help in producing it and carrying it into effect. Let 

 " them read history and they will find that Archites made a dove that could 

 " fly, and that Archimedes made a mirror that burned at great distances, and 

 " other admirable machines ; now by reasoning on these, they will be able 

 " with very little trouble, and very great honour and advantage, to discover their 

 " construction, but even if they do not succeed, they will derive the benefit of 

 " being able to certify themselves that the ease of fabrication which they. 

 " promised themselves from the pre-knowledge of the true result was much 

 " less than they had imagined." 



We must add that many of the principal persons in Europe were anxious 

 to have Galileo's telescopes, and that he sent presents of them to the Grand 

 Duke of Tuscany, to Prince D. Antonio de' Medici, the Elector of Bavaria, 

 the Emperor Mathias, Cardinal Borghese, the Queen of France, the King of 

 Spain, the King of Poland, the Landgrave of Hesse, Giuliano de' Medici, 

 Cardinal Del Monte, Cardinal Montalto, to the Dukes of Acerenza and of 

 Acquairva, &c., &c. ; he also sent some to Holland, whence Constantino 



