Thesaurarium mathematicae, or, The treasury of mathematicks containing variety of usefull practices in arithmetick, geometry, trigonometry, astronomy, geography, navigation and surveying ... to which is annexed a table of 10000 logarithms, log-sines, and log-tangents / by John Taylor.

PROP. IV. How to draw the Hour-lines on a direct South, and North Plane,

This Plane or Dial must stand upright, ha∣ving his face or Plane, if it be a South Dial, di∣rectly opposite unto the South; but if a North Plane, directly opposite unto the North; now admit it be required to make a Direct South Dial,* 1.1 for the Latitude of 51° 32': To make which first describe the Circle ABCD, to represent an E••ect direct South Plane, cross it with the Dia∣meters CB, and AD, then out of your Line of Chords take 38° 28', the Complement of the La∣titude, and set it from A, unto a, and from B, unto b, Then lay a Ruler from C unto a, and it will cut the Meridian ARD, in P, the Poles of

[illustration]

Plate V Page 261

* 1.2 * 1.3* 1.4* 1.5

other hath the North Pole of the World eleva∣ted above it, and beholdeth the North part of the Meridian. The Hour-lines of 9, 10, 11, or 1, 2, and 3, is not expressed on this Plane, because 12, representeth 12, at Midnight; neither are the other said Hours expressed, because the Sun is never above the Horizon, at those Hours; Therefore the North Dial is capable only to* 1.6 receive these Hours, namely 4, 5, 6, 7, and 8, in the Morning; and 4, 5, 6, 7, and 8, at Night; as doth plainly appear in the Figure: Now the distance of the Hour-lines from the Meridian, may be found by this Analogy, or Propor∣tion.

As Radius or S. 90°,

To Sc. of the Latitude.

So is T. of the Hour from Noon,

To T. of the Hour-line from the Meridian.

Notes

• * 1.1

  Fig. 68.
• * 1.2

  Fig.
• * 1.3

  Fig. 68.
• * 1.4

  Fig.
• * 1.5

  69.
• * 1.6

  Fig. 69.