Line of, two particular lines on Gunter's sector. They lie between the lines of sines and superficies, and are numbered 5, 6, 7, 8, 9, 10. They represent the diameter of a circle, so divided into 100 parts, that a right line drawn through these parts, and perpendicular to the diameter, shall cut the circle into two segments, the greater of which shall have the same proportion to the whole circle as the parts cut off have to 100.