hemisphere vs spherule

hemisphere

noun
  • Any half-sphere, formed by a plane intersecting the center of a sphere. . 

  • A realm or domain of activity . 

  • A map or projection of a celestial or terrestrial hemisphere . 

  • Half of the celestial sphere, as divided by either the ecliptic or the celestial equator . 

  • Half of the Earth, such as the Northern Hemisphere, Southern Hemisphere, Western Hemisphere or Eastern Hemisphere, Land Hemisphere, Water Hemisphere etc. . 

  • Either of the two halves of the cerebrum. . 

spherule

noun
  • A small sphere. 

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