dissertation vs tract

dissertation

noun
  • A lengthy lecture on a subject; a treatise; a discourse; a sermon. 

  • A formal exposition of a subject, especially a research paper that students write in order to complete the requirements for a doctoral degree in the US and a non-doctoral degree in the UK; a thesis. 

tract

noun
  • A brief treatise or discourse on a subject. 

  • Part of the proper of the liturgical celebration of the Eucharist for many Christian denominations, used instead of the alleluia during Lenten or pre-Lenten seasons, in a Requiem Mass, and on a few other penitential occasions. 

  • A series of connected body organs, such as the digestive tract. 

  • A commentator's view or perspective on a subject. 

  • Continued or protracted duration, length, extent 

  • An area or expanse. 

  • A small booklet such as a pamphlet, often for promotional or informational uses. 

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