heliograph vs jacklight

heliograph

noun
  • An apparatus for signalling by means of a moveable mirror which reflects flashes of sunlight. 

  • A heliogram. 

  • A device for photographing the sun. 

  • An instrument for measuring the intensity of sunlight. 

verb
  • To send a message by heliograph. 

  • To send a heliograph. 

jacklight

noun
  • A spotlight or lamp mounted on a car. 

verb
  • To shine a jacklight or spotlight on an animal, usually a deer, to aid in hunting at night. 

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