clearness vs coherence

clearness

noun
  • Mental or sensory distinctness; clarity of understanding, perception etc. 

  • The state of being free from obstruction or interference. 

  • The state of being free from obscurities or opacity; distinctness of light, colour etc. 

coherence

noun
  • The quality of cohering, or being coherent; internal consistency. 

  • The property of having the same wavelength and phase. 

  • A logical arrangement of parts, as in writing. 

  • A semantic relationship between different parts of the same text. 

  • The quality of forming a unified whole. 

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