The mariners magazine, or, Sturmy's mathematical and practical arts containing the description and use of the scale of scales, it being a mathematical ruler, that resolves most mathematical conclusions, and likewise the making and use of the crostaff, quadrant, and the quadrat, nocturnals, and other most useful instruments for all artists and navigators : the art of navigation, resolved geometrically, instrumentally, and by calculation, and by that late excellent invention of logarithms, in the three principal kinds of sailing : with new tables of the longitude and latitude of the most eminent places ... : together with a discourse of the practick part of navigation ..., a new way of surveying land ..., the art of gauging all sorts of vessels ..., the art of dialling by a gnomical scale ... : whereunto is annexed, an abridgment of the penalties and forfeitures, by acts of parliaments appointed, relating to the customs and navigation : also a compendium of fortification, both geometrically and instrumentally / by Capt. Samuel Sturmy.

Rules for Observation in North Latitude.

SUppose I am at Sea, and I observe the Sun's Meridian Altitude to be 39 deg. 32 min. and the same time the Sun's Declination is 15 deg. 20 min. North; I de∣mand the Latitude I am in.

	deg.	min.
The Meridian Altitude	39	32
The Declination North, subst.	15	20
The Complement of the Lat.	24	12
	90	00
The Latitude I am in	65	48 North.

Suppose I were in a Ship at Sea the 18th of April, Anno 1667. and by Observati∣on I find the Sun's Meridian Altitude to be 62 deg. 15 min. The Latitude is required.

	deg.	min.
The Meridian Altitude	62	15
The Declination North, subst.	14	18
The Complement of the Latitude	47	57
	90	00
The Latitude I am in, required	42	03

Admit you were in a Ship at Sea the 5th of November, Anno 1679. and I find the Sun's Meridian Altitude to be 24 deg. 56 min. The Latitude is required I am in.

	deg.	min.
The Meridian Altitude	24	56
The Declination South, add	18	37
The Complement of the Latitude	43	33
	90	00
The Latitude I am in	46	27

Suppose a Ship at Sea the 28th of May, Anno 1666. and I find the Sun's Me∣ridian Altitude by Observation 56 deg. 45 min. The Latitude is required I am in.

	deg.	min.
The Meridian Altitude	56	45
The Declination North, Subst.	22	46
The Complement of the Latitude	33	59
	90	00
The Latitude required I am in	56	01

Admit a Ship at Sea the 11th of June 1668. and find the Sun's Meridian Al∣titude by Observation 79 deg. 30 min. North, It is required the Latitude I am in.

	deg.	min.
The Meridian Altitude	79	30
The Declination North	23	31 add.
	103	01
	90	00
The Latitude I am in	13	01 required.

Suppose I were at Sea the 14th of May 1693. and the Meridian Altitude of the Sun was 69 deg. 07 min. North, I demand the Latitude the Ship is in at that time.

	deg.	min.
The Meridian Altitude	69	07
The Declination North	20	53 add.
	90	00
	90	00
The Ship is under	00	00 the Aequinoctial.