Hammer and nail; a note on cruel and kindly Nature
Why a hammer-blow ejects a nail, with a pen aphorism on Nature
At the upper right a small sketch shows a hammer striking a nail set into a cylinder, with a note asking why the blow makes the nail spring out. Below, a passage written in pen reflects that Nature seems in many animals to have been a cruel stepmother rather than a mother, and to some a compassionate mother. The page thus pairs a mechanics question with a philosophical aside.
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Why a hammer-blow springs the nail out
The sketch at upper right shows a nail set into a cylinder being struck by a hammer. Leonardo asks why the blow of the hammer makes the nail spring out. It is a question about the effect of impact.
Nature as cruel stepmother and tender mother
A note written in pen reflects that Nature here seems, in many animals, to have been a cruel stepmother rather than a mother, and to some not a stepmother but a compassionate mother. It is one of the notebook's philosophical asides.