memoir vs treatise

memoir

noun
  • Any form of narrative describing the personal experiences of a writer. 

  • A biography; a book describing the experiences of a subject from personal knowledge of the subject or from sources with personal knowledge of the subject. 

  • An autobiography; a book describing the personal experiences of an author. 

treatise

noun
  • A formal, usually lengthy, systematic discourse on some subject. 

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