Nine geometricall exercises, for young sea-men and others that are studious in mathematicall practices: containing IX particular treatises, whose contents follow in the next pages. All which exercises are geometrically performed, by a line of chords and equal parts, by waies not usually known or practised. Unto which the analogies or proportions are added, whereby they may be applied to the chiliads of logarithms, and canons of artificiall sines and tangents. By William Leybourn, philomath.

Its Description.

IT is no other then a Quadrant made upon a piece of very thin Brass, and divided into 90 degr. the Brass being cut away close to the divisions of the degrees on the out-side, and also the hollow within, so that there remains nothing but the Limb and the two Sides, as you may discern by the Figure. In the protracting or laying down of Angles, and in finding of the quantity of Angles already laid down, this is

Its Ʋse.

[illustration] geometrical diagram

SUppose you were to finde the quantity of the Angle C A B. Hold a Pin or Needle upon the angular Point at A, to which bring the Centre of your Quadrant, (noted also with A) and there turn it about, till the Me∣ridian Line thereof, A B, lie upon the Line A B of the Angle: then see un∣der what degrees of the Quadrant the Line A C

lieth, which you shall find to lie just under 40 degr. And such is the quantity of the Angle C A B.—And if upon the Line B A you were to protract such an Angle of 40 degr. Lay the Meridian Line of the Quadrant upon the Line A B, (the Centre of the Quadrant upon the Point A) and with your Needle make a prick or point just against 40 degr. of the Quadrant's limb. So a Line drawn from A through this Point shall make an Angle of 40 degr.