By means of the sector, we may dispense with the protractor. Thus, to lay down an angle of any number of degrees: - take the radius of the circle on the compasses, and open the sector till this becomes the transverse distance of 60 on the line of chords; then take the transverse distance of the required number of degrees, keeping the sector at the same opening; and this transverse distance being marked off on an arc of the circle whose radius was taken, will be the required number of degrees.

We will not enter farther on the use of the sectorial lines, as what we have said will, we hope, be found sufficient for the purposes of the practical mechanic.