gradual vs seeable

gradual

noun
  • A service book containing the musical portions of the Mass. 

  • An antiphon or responsory after the epistle, in the Mass, which was sung on the steps, or while the deacon ascended the steps. 

adj
  • Proceeding or advancing by small, slow, regular steps or degrees 

seeable

noun
  • That which is to be seen. 

adj
  • Able to be seen; visible. 

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