The description and use of a joynt-rule fitted with lines for the finding the hour of the day and azimuth of the sun, to any particular latitude, or, to apply the same generally to any latitude : together with all the uses of Gunters quadrant applyed thereunto ...
Brown, John, philomath.
For 6 and 12.
As the Co•tangent of the Latitude,
To the Sine of 90:
So is the sine of Declination,
To the Cotangent of 6 from 12.
