CHAP. IX.
Figures illustrating direction and showing varieties
of rotations.
assing from the probable cause of motion toward fixed points (according to magnetick laws and principles), it remains for us to indicate those motions. Above a round loadstone (whose poles are A, B) let a versatory needle be placed whose cusp has been excited by the pole A;
that cusp is certainly directed toward A, and is strongly attracted by A; because, having been touched by A, it is in true harmony with A, and combines with it; and yet it is called contrary, because when the versorium is separated from the stone, it is seen to be moved toward the opposite part of the earth to that toward which the pole A of the loadstone is moved. For if A be the northern pole of the terrella, the cusp is the southern end of the needle, of which the other end (namely, the cross) is pointed to B; so B is the southern pole of the loadstone, but the cross is the northern end of the versorium. So also the cusp is attracted by E, F, G, H, and by every * part of a meridian, from the æquator toward the pole, by the faculty disponent; and when the versorium is on the same parts of the meridian, the cusp is directed toward A. For it is not the point A that turns the versorium toward it, but the whole loadstone; as also the whole earth does, in the turning of loadstones to the earth.
Figures illustrating magnetick directions in a right sphere of stone, and in the right sphere of the earth, as well as the polar directions to the perpendicular of the poles. All these cusps have been touched by the pole A; all the cusps are turned toward A, excepting that one which is repelled by B.
Figures
