catch sight of vs discern

catch sight of

verb
  • to see for a brief period; to get a glimpse of 

discern

verb
  • To detect with the senses, especially with the eyes. 

  • To distinguish something as being different from something else; to differentiate. 

  • To perceive, recognize, or comprehend with the mind; to descry. 

  • To perceive differences. 

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