Source : Webster's Revised Unabridged Dictionary (1913)

Joule \Joule\ (j[=oo]l), n. [From the distinguished English
   physicist, James P. Joule.] (Physics.)
   A unit of work which is equal to 10^{7} units of work in the
   C. G. S. system of units (ergs), and is practically
   equivalent to the energy expended in one second by an
   electric current of one ampere in a resistance of one ohm.
   One joule is approximately equal to 0.738 foot pounds.

   {Joule's equivalent}. See under {Equivalent}, n.



   Note: This term was adopted by Wollaston to avoid using the
         conjectural expression atomic weight, with which,
         however, for a time it was practically synonymous. The
         attempt to limit the term to the meaning of a
         universally comparative combining weight failed,
         because of the possibility of several compounds of the
         substances by reason of the variation in combining
         power which most elements exhibit. The equivalent was
         really identical with, or a multiple of submultiple of,
         the atomic weight.

   3. (Chem.) A combining unit, whether an atom, a radical, or a
      molecule; as, in acid salt two or more equivalents of acid
      unite with one or more equivalents of base.

   {Mechanical equivalent of heat} (Physics), the number of
      units of work which the unit of heat can perform; the
      mechanical energy which must be expended to raise the
      temperature of a unit weight of water from 0[deg] C. to
      1[deg] C., or from 32[deg] F. to 33[deg] F. The term was
      introduced by Dr. Mayer of Heilbronn. Its value was found
      by Joule to be 1390 foot pounds upon the Centigrade, or
      772 foot pounds upon the Fahrenheit, thermometric scale,
      whence it is often called {Joule's equivalent}, and
      represented by the symbol J. This is equal to 424 kilogram
      meters (Centigrade scale). A more recent determination by
      Professor Rowland gives the value 426.9 kilogram meters,
      for the latitude of Baltimore.