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.

The Ʋse of the Fore-Staff in South Latitude for the Sun and Stars.

SUppose I were at Sea in a Ship the second of June, Anno 1694, and I find the Sun's Meridian Altitude by Observation to be 59 deg. I demand the Latitude the Ship is in.

	deg.	min.
The Meridian Altitude North	59	00
The Declination North, add	23	15
The Complement of the Latitude	82	15
	90	00
The Latitude required	07	45

Admit I were at Sea in a Ship to the Southward of the Aequinoctial, the 12th of January, Anno 1682. and in Longitude 135 East; and I find by Observation the Me∣ridian Altitude 63 deg. 34 min. North: There is required the Latitude the Ship is in.

The Declination for this Meridian, the Lands-end of England, is about 19 deg. 33 min. the daily difference in Declination at this time is 14 min. Therefore if you look in the Table of Proportion, you will find the Proportional Minutes to be 5, which you must add to the Declination of the former Meridian, and the Sum will be the true Declination for the Longitude of 135 deg. East, which is 19 deg. 38 min.

	deg.	min.
The Meridian Altitude	63	34
The Declination South	19	38 substract.
The Complement of the Latitude	43	56
	90	00
The Latitude required	46	04

Admit a Ship were at Sea the third of August, Anno 1675. and I find the Sun's Meridian Altitude to be 59 deg. 36 min. North, The Latitude is required.

	deg.	min.
The Meridian Altitude North	59	36
The Declination North, add	14	42
The Complement of the Latitude	74	18
	90	00
The Latitude the Ship is in	15	42

Suppose a Ship at Sea, the Sun's Declination being 21 deg. 42 min. South, and the Sun's Meridian Altitude 74 deg. 23 min. South, The Latitude is required the Ship is in.

	deg.	min.
The Complement of the Sun's Meridian Altitude	15	37
Substracted from the Sun's Declination	21	42
The Latitude the Ship is in	06	05

This being made so plain and easie to be understood, need no more Precedent: But observe this, If you observe the upper Edge or part of the Sun, you must sub∣stract 16 minutes; if the lower part, add 16 minutes for the Semidiameter of the Sun, and the Sum sheweth the true Altitude of the Center of the Sun.