chimney stack vs smokestack

chimney stack

noun
  • A vertical structure, normally of brick, rising from a roof, containing one or more flues, each one terminating in a chimney pot. 

smokestack

noun
  • A conduit or group of conduits atop a structure allowing smoke to flow out, as on a steam locomotive, ship, factory, or power plant using fossil fuels. 

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