ARMATURE (armatures, armor; Ger. anker). The term A. is applied to the pieces of soft iron that are placed at the extremities or poles of magnets to preserve their mag netic power. When magnets are allowed to remain any length of time without such appendages, in consequence of the disturbing influence of terrestrial magnetism they lose considerably in strength; but when they are provided with them their magnetism is kept in a state of constant activity, and thereby shielded from this disturbance. The reason of this is found in two facts well known in the science of, magnetism—viz., that when a piece of soft iron is brought into contact with the extremity of a magnet, it is itself induced to become magnetic; and that the unlike poles of two different magnets poWer fully attract each other. Referring to the figure, the north pole, N, of the horseshoe magnet, NHS, acting on the armature, sn, induces it to become a mag net, having its south pole, s, next to N, and its north pole, n, at the opposite extremity. The pole, S, by virtue of its magnetic affinity, powerfully attracts the north pole, n, thus formed, and adds its own inducing influence to •heighten the magnetic condition previously induced in the armature by the pole N. The A., from the combined
action of both poles of the horseshoe magnet, is thus converted into a 4 powerful magnet, with its poles lying in an opposite direction to that of the primary poles. The original magnet is, in consequence, brought t into contact with one of its own making, the exact counterpart of itself—a condition highly favorable to the maintenance of its strength. It is due to the same mutual attractions that a much larger weight can be suspended from the A. thus placed, than what the single poles can together sustain. Bar magnets may be armed in the same way by lay ing them at some distance parallel to each other, with their unlike poles towards the same parts, and then connecting their extremities by two pieces of soft iron. When a magnet, such as a compass-needle, is free to take up the position required by the magnetism of the earth, the earth itself plays the part of au armature.