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 ... / contriv'd & written by J. Brown, philomath.

2. To finde the Suns Altitude at any time.

Put a pin in the center hole, at the upper end of the Scale of Altitudes, and on the pin hang a thread and plum∣met; then if the Sun be low, that is to say, under 25 degrees high, as in the winter it will always be, then lift up the moveable leg, where the moneths and the degrees be, till the shadow of the end fall just on the meeting of that leg with the head, then the thread shall shew the Suns altitude, counting from 60|0 towards the head, either 10, 20, 25, or any degree between.

But if the Sun be above 25 or 30 de∣grees

high, lift up the head leg till the shadow of that play as before, or make the shadow of the pin in the center hole play on the innermost line of the Scale of Altitudes where the pin stand∣eth, then the thread will fall on the degree, and part of a degree that his true altitude shall be.

But if the Sun be in a cloud, and can not be seen so as to give a shadow, then look up along by the head-leg, or move∣able leg, just against the middle of the round body of the Sun, and the thread playing evenly by the degrees, shall show the true altitude required. The like must you do for a Star, or any other object, whose altitude you would find.