cast about vs delve

cast about

verb
  • To try to find; look around; search. 

  • To plan; plot; contrive. 

delve

verb
  • To search thoroughly and carefully for information, research, dig into, penetrate, fathom, trace out 

  • To dig; to excavate. 

  • To dig into the ground, especially with a shovel. 

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