mediate vs preside (over)

mediate

adj
  • Gained or effected by a medium or condition. 

  • Acting through a mediating agency, indirect. 

  • Intermediate between extremes. 

verb
  • To divide into two equal parts. 

  • To act as an intermediary causal or communicative agent; to convey. 

  • To intervene between conflicting parties in order to resolve differences or bring about a settlement. 

  • To resolve differences, or to bring about a settlement, between conflicting parties. 

  • To act as a spiritualistic medium. 

preside (over)

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