CHAP. XXII. How to find the Arches and Angles which are requisite in a North Decliner Recliner, and a South Decliner Incliner.
I Could not pass by this Example of the North Recliner Decliner, and South In∣cliner Decliner, although it is shewed in the Fundamental Diagram; but it may be too obscure, and harder to be apprehended by the Industrious Practitio∣ner there; therefore I would advise him to draw a Scheme of the Dial, as was shewed Chap. 15. & 18. or draw the Fundamental Diagram in Paper, and with a small Needle prick the Hour-lines, Horizon, and Meridians; Aequinoctial, and the Tro∣picks; and then you have a Figure ready to be stamped with a little Charcoal-dust as often as you have occasion: Or if you apprehend your Work in any manner, the Figure following, or the like, may serve your turn, to shew you the Angles you are to find, and Arches for the making of your Dial. I shall be short in this, and refer you to Chap. 15. & 18.
The Circle ESWN is our Horizon, as before; NS our Meridian, FLC the Plane, ZL the Reclination thereof, FC the Base or Horizontal Line of the Plane, AEN the Vertical of the Plane, cutting it right at L, and cutting the Pole thereof at H: for N is the Pole of a Plane erect upon FC; but the Pole of the Reclining Plane FLC is H; SE or nN the Declination of the Plane.
Now you see your three Triangles all adjoyning in this Scheme, viz. FSO and ORP rectangled at S and R, and PZH obtuse angled at Z.
It is true, That the two first may do the Work, and so we will be brief. Observe, you are to find as followeth.
- 1. The Arch between the Horizon and the Plane FO.
- 2. The Arch of the Meridian between the Horizon and the Plane SO.