ARMATURE, a covering for defence. In zoology the word is used of the bony shell of the armadillo. In architecture it is applied to the iron stays by which the lead lights are secured in windows. (See STANCHION and SADDLE : Saddle-Bars.) In mag netism Dr. William Gilbert applied the term to the piece of soft iron with which he "armed" or capped the lodestone in order to increase its power. It is also used for the "keeper" or piece of iron which is placed across the poles of a horse-shoe magnet, and held in place by magnetic attraction, in order to complete the magnetic circuit and preserve the magnetism of the steel; and hence, in dynamo-electric machinery, for the portion which is at tracted by the electromagnet. The term is now applied to that member of an electric generator (q.v.) or motor (q.v.) in which currents are induced by the action of the field.