Source : Webster's Revised Unabridged Dictionary (1913)

Horology \Ho*rol"o*gy\, n. [See {Horologe}.]
   The science of measuring time, or the principles and art of
   constructing instruments for measuring and indicating
   portions of time, as clocks, watches, dials, etc.

Source : WordNet®

horology
     n : the art of designing and making clocks