The Notebooks of Leonardo Da Vinci Complete


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if all the mass of the earth were to be turned into salt, it would  
not suffice for all human food [Footnote 27: That is, on the  
supposition that salt, once consumed, disappears for ever.]; whence  
we are forced to admit, either that the species of salt must be  
everlasting like the world, or that it dies and is born again like  
the men who devour it. But as experience teaches us that it does not  
die, as is evident by fire, which does not consume it, and by water  
which becomes salt in proportion to the quantity dissolved in  
it,--and when it is evaporated the salt always remains in the  
original quantity--it must pass through the bodies of men either in  
the urine or the sweat or other excretions where it is found again;  
and as much salt is thus got rid of as is carried every year into  
towns; therefore salt is dug in places where there is urine.-- Sea  
hogs and sea winds are salt.  
We will say that the rains which penetrate the earth are what is  
under the foundations of cities with their inhabitants, and are what  
restore through the internal passages of the earth the saltness  
taken from the sea; and that the change in the place of the sea,  
which has been over all the mountains, caused it to be left there in  
the mines found in those mountains, &c.  
The characteristics of sea water (948. 949).  
9
48.  
779  


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