How to take the Declination of any Wall or Plane, without the help of a Needle or Loadstone.
FOr Example. Suppose SNDE represent a Wall, or the face of the Plane where∣on I am to make a Dial, and I desire to know the Declination thereof from the Meridian Eastward or Westward.
If you have no Instrument, take a plain Board, having one planed or straight side or edge, which Board let be repre∣sented by DEVQ: apply the straight edge of the Board ED to the side of the Wall or Plane, as in this Figure, and in the middle of the Board at C, I set one foot of the Compasses, and the other opened to 60 deg. of my Line of Chords, I describe the Circle ZBHA. In the Center C, I erect or place a Stile or Wire, as CO perpendicular to the Horizon, pla∣cing the Board as neer Horizontal as I can. I find by observation, that the shadow of the top of the Pin or Wire toucheth the Circle in the forenoon at the Point B, where I make a little mark; and like∣wise I observe in the afternoon that it toucheth the said Circle in the Point A: Then I measure the half thereof from B or A to X, and drawing a Line through the Center to X, as KCX, you shall have the Meridian Line exactly described KCX. Lastly, I take the Distance ZX, which I apply to my Scale of Chords, and find the Arch thereof 18 deg. 10 min. and so much is the Declination of th•• Plane EDNS, which you may see by the Meridian Line XK to be towards the East; therefore it is a South Plane declining West 18 d. 10 m. This way is the most easie way, and requires time for the making the two Ob∣servations; therefore I will lay down some other ways, that may resolve at one mo∣ment, or at one observation.