Nine geometricall exercises, for young sea-men and others that are studious in mathematicall practices: containing IX particular treatises, whose contents follow in the next pages. All which exercises are geometrically performed, by a line of chords and equal parts, by waies not usually known or practised. Unto which the analogies or proportions are added, whereby they may be applied to the chiliads of logarithms, and canons of artificiall sines and tangents. By William Leybourn, philomath.

PROBL. I. How to find at what time any of the Stars in the Table of the Sixth Proposition will be upon the Meridian.

SUbstract the Right Ascension of the Sun from the Right As∣cension of the Star, the remainer is the time of the Star's coming to the Meridian after noon. But if the right Ascension of the Star be less then the Right Ascension of the Sun, adde 360 degr. thereto, and substract the Right Ascension of the Sun from the Sum, and the Remainer is the time of the Star's coming to the Meridian.

Example. Upon the fourth of October 1667, the Sun being in 21. degr. of Libra, I would know at what time Sirius (or the Great Dog) will be upon the Meridian.

	d.	m.
The Right Ascension of Sirius is	97	27
The Right Ascension of the Sun that day is	199	23
Because Substraction cannot be made, adde 360 d. to the Right Ascension of the Star	360	00
The Sum is	457	27
The Sun's Right Ascension substracted from 458 degr. 4 min. leaves the time of the Star's coming to the Meridian	258	04

Which 258 degr. 4 min. being converted into Time make 17 hours almost, that is, at 5 of the Clock the next Morning Sirius will be upon the Meridian.