POLE, PULAR. The word woacor as applied to a point means a turning or hinge point, and was applied to the points at the extremity of the axis of the celestial sphere in the ancient astronomy. Hence, on the hypothesis of the earth's rotation, it comes to mean the extremities of the axis on which the earth turns. From this primary meaning all the various uses of the word pole have been derived. For example, when it was found that the magnet did not always point to the north pole, but to another point, it was natural to call that other point the magnetic pole. Previously to this use of the word, it had already taken a wider signification, as follows :—On looking at the position of the equator with respect to the poles, it is obvious that if the equator, or circle of equal day and night, should be changed, the axis must also be changed, and the poles of rotation. Hence any great circle of the sphere is said to have its poles, meaning those points which would become poles of rotation if that circle became the equator. [SPHERE.] A term seldom passes through several signification, however nearly related, without at last becoming generic in the widest sense. The
word pole is now used to denote any point which is of so strik ing a character as to require a distinct name. In physics the word is naturalised in magnetism, electricity, and optics ; insomuch that any tendency towards a particular point, or even towards a particular direction, is termed polarity. In geometry, the only definition which can now be given of this term is, that it means any point which it is wanted to mean. Thus a point considered as the origin of CO ORDINATES is called the pole; and when distances measured from the origin are among the co-ordinates, they are called polar. Again, it is a well known property of the conic sections, that if all possible chords be drawn through any one given point, and a pair of tangents be drawn from the extremities of each chord, the intersections of all the pairs will lie in one straight line ; the point through which the chords are drawn is called the pole of that straight line.