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. II. To find the Hour of the Night by any of the Stars that are in the Table of the Sixth Proposition.

TAKE the Altitude of the Star, and by his Declination and Altitude find the Hour (by the Twelfth Proposition) as if it were by the Sun, which I call the Star's Hour. Then comparing the Right Ascension of the Sun with the Right Ascen∣sion of the Star, you may come to find the Hour of the Night.

Example. Upon the 16. day of November, in the Morning, I took the Altitude of Arcturus, finding it to be 27 degr. 12 m. and his Declination (by the Table) I find to be 20 degr. 58 m. By help of these two and the Latitude I find the Star's Hour to be 72 degr. Then compare the Sun's Right Ascension with the Star's Right Ascension, and find his time of coming to the Meridian, as in the former Probl. the difference between the Star's Hour and his coming to the Meridian is the Hour of the Night. See the manner of the Operation.

	d.	m.
The Right Ascension of Arcturus	210	13
The Right Ascension of the Sun	242	00
Adde to make Subt.	360	00
The Sum is	570	13
The Sun's Right Ascension substracted, rests	328	13
From which take 180 degr. or 12 hours	180	00
Rests	148	13
The Star's Hour substracted	72	00
Leaves the Hour of the Night	76	13

Which converted into Time is 5 h. 5 m. and that is the Hour in the Morning.