LETTER LVIII. Why Does the Magnetic Needle Affect, in Every Place of the Earth, a Certain Direction, Differing in Different Places; and for What Reason Does It Change, with Time, at the Same Place?
LETTER LVIII. Why Does the Magnetic Needle Affect, in Every Place of the Earth, a Certain Direction, Differing in Different Places; and for What Reason Does It Change, with Time, at the Same Place?