Source : Webster's Revised Unabridged Dictionary (1913)

Corps of Engineers \Corps of Engineers\, a corps of officers and
   enlisted men consisting of one band and three battalions of
   engineers commanded by a brigadier general, whose title is
   Chief of Engineers. It has charge of the construction of
   fortifications for land and seacoast defense, the improvement
   of rivers and harbors, the construction of lighthouses, etc.,
   and, in time of war, supervises the engineering operations of
   the armies in the field.
   (b) In the United States navy, a corps made up of the
       engineers, which was amalgamated with the line by act of
       March 3, 1899. It consisted of assistant and passed
       assistant engineers, ranking with ensigns and
       lieutenants, chief engineers, ranking from lieutenant to
       captain, and engineer in chief, ranking with commodore
       and having charge of the Bureau of Steam Engineering.