pendulum vs sundial

pendulum

noun
  • A watch's guard-ring by which it is attached to a chain. 

  • Used to refer to the tendency of a situation to oscillate (between two extremes). 

  • A lamp, etc. suspended from a ceiling. 

  • A body suspended from a fixed support so that it swings freely back and forth under the influence of gravity, commonly used to regulate various devices such as clocks. 

sundial

noun
  • A device measuring the time of day by the position of a shadow cast by a pole or plate (gnomon) upon an engraved series of marks. 

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