The compleat surveyor containing the whole art of surveying of land by the plain table, theodolite, circumferentor, and peractor ... : together with the taking of all manner of heights and distances, either by William Leybourn.

3. How to finde the quantity of any angle in the field, by the Circumferentor.

If it were required to finde the quantity of the former angle EKG, by the Circumferentor; First, place your Instrument (as before) at K, with the Flower-de-luce, in the Card, towards you; then direct your sights to E, and observe what degrees in the Card are cut by the South end of the Needle, which let be 296, then turning the Instrument about the staffe (the Flower-de-luce alwayes towards you) direct the sights to G, noting then also what degrees are cut by the South end of the Needle, which suppose 182, this done (alwayes) substract the lesser number of degrees out of the greater, as in this Example 182 from 296, and the remainder is 114 degrees, which is the true quantity of the angle EKG.

Again; the Instrument standing at K, and the sights being direct∣ed to E, as before, suppose that the South end of the Needle had cut 79 degrees; and then directing the sights to G, the same end of the needle had cut 325 degrees, now, if from 325, you substract 79, the remainder is 246, but because this remainder 246 is greater then 180, you must therefore substract 246 the remainder, from 360, and there will remain 114, the true quantity of the inquired angle, and thus you must alwayes do, when the remainder exceedeth 180 degrees.

¶ This adding and substracting for the finding of angles, may seeme tedious to some, but here the Reader is desired to

take notice, that for quick dispatch, the Circumferentor is as good an Instrument as the best, for in going round a field, or in surveying of a whole Mannor, you are not to take notice of the quantity of any angle, but only to observe what de∣grees the needle cutteth, which in those cases is sufficient, as will appear hereafter, but in taking of distances by the Cir∣cumferentor it is altogether necessary, as may appear by the 7 Chap. following, and for that reason I have here shewed how to finde an angle by the Circumferentor, and also that you might thereby perceive what congruity and harmony there is in all the three Instruments.