instability vs solidity

instability

noun
  • The quality of being unstable. 

  • A state that is not in equilibrium, or in which a small change has a large irreversible effect. 

solidity

noun
  • The state or quality of being solid. 

  • Moral firmness; validity; truth; certainty. 

  • The solid contents of a body; volume; amount of enclosed space. 

How often have the words instability and solidity occurred in a corpus of books? (source: Google Ngram Viewer )