Source : Webster's Revised Unabridged Dictionary (1913)

Spherograph \Spher"o*graph\, n. [Sphere + -graph.]
   An instrument for facilitating the practical use of spherics
   in navigation and astronomy, being constructed of two
   cardboards containing various circles, and turning upon each
   other in such a manner that any possible spherical triangle
   may be readily found, and the measures of the parts read off
   by inspection.