The Notebooks of Leonardo Da Vinci Complete


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That the heat of the sun resides in its nature and not in its virtue  
or mode of action] is abundantly proved by the radiance of the  
[
solar body on which the human eye cannot dwell and besides this no  
less manifestly by the rays reflected from a concave mirror,  
which--when they strike the eye with such splendour that the eye  
cannot bear them--have a brilliancy equal to the sun in its own  
place. And that this is true I prove by the fact that if the mirror  
has its concavity formed exactly as is requisite for the collecting  
and reflecting of these rays, no created being could endure the  
heat that strikes from the reflected rays of such a mirror. And if  
you argue that the mirror itself is cold and yet send forth hot  
rays, I should reply that those rays come really from the sun and  
that it is the ray of the concave mirror after having passed through  
the window.  
Considerations as to the size of the sun (886-891).  
8
86.  
The sun does not move. [Footnote: This sentence occurs incidentally  
among mathematical notes, and is written in unusually large  
letters.]  
8
87.  
725  


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