2These lines being accurately drawn, a small flexible ruler of willow or withy, smeared with liquid pitch, is attached at the first point of intersection, and made to pass obliquely through the remaining intersections of the longitudinal and circular divisions; whence progressing and winding through each point of intersection it arrives and stops in the same line from which it started, receding from the first to the eighth point, to which it was at first attached. In this manner, as it progresses through the eight points of the circumference, so it proceeds to the eighth point lengthwise. Thus, also, fastening similar rules obliquely through the circumferential and longitudinal intersections, they will form eight channels round the shaft, in the form of a screw.
2When these lines have been correctly drawn, a slender withe of willow, or a straight piece cut from the agnus castus tree, is taken, smeared with liquid pitch, and fastened at the first point of intersection.
Then it is carried across obliquely to the succeeding intersections of longitudinal lines and circles, and as it advances, passing each of the points in due order and winding round, it is fastened at each intersection; and so, withdrawing from the first to the eighth point, it reaches and is fastened to the line to which its first part was fastened. Thus, it makes as much progress in its longitudinal advance to the eighth point as in its oblique advance over eight points. In the same manner, withes for the eight divisions of the diameter, fastened obliquely at the intersections on the entire longitudinal and peripheral surface, make spiral channels which naturally look just like those of a snail shell.