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.

Directions for Observation in South Latitude.

ADmit a Ship at Sea the 7th of July, Anno 1695. and I am in Longitude 135 deg. East, and the Sun being upon the Meridian, I find the Complement of his Meridian Altitude by Observation to be 42 deg. 34 min. North; The Latitude is demanded, the Ship is in.

	deg.	min.
The Complement of the Meridian Altitude	42	34
The Sun's Semidiameter, add	00	16
The Sun's Center distant from the Zenith	42	50
The Declination North, substract	21	16
The Latitude the Ship is in	21	34

Admit I were in a Ship the fifth of November, Anno 1687. and in Longitude 120 deg. West, and the Complement of the Sun's Meridian Altitude by Observation is 31 deg. 37 min. North; The Latitude is required, the Ship is in.

	deg.	min.
The Complement of the Meridian Altitude	31	37
The Sun's Semidiameter, add	00	16
The Sun's Center distant from the Zenith	31	53
The Declination South	18	37
The Proportional Minutes	00	05 Added.
The Sun's Declination in the Meridian given	18	42
Which add to the Zenith-distance	31	53
The Latitude the Ship is in	50	35

Suppose I were in a Ship at Sea to the Southwards of the Aequinoctial, the third of January, Anno 1683. and I find the Sun upon the South part of the Meridian, and by Observation his Meridian Altitude is 75 deg. 38 min. The Latitude the Ship is in, is required.

	deg.	min.
The Complement of the Meridian Altitude	14	22
The Sun's Semidiameter, add	00	16
The Sun's Center from the Zenith	14	38
The Declination South	21	28
The Latitude the Ship is in South	06	50

EXAMPLE.

In this Figure let C be the South, and P the North Pole, DE the Aequinoctial, AB the Horizon, Z the Ze∣nith. Let AF be the Altitude of the Sun a∣bove the Horizon, in the North 58 deg. DF South Declination 8 deg. If you substract the Declination DF 8 deg. from FA the Altitude, there remains 50 deg. the Height of the Ae∣quinoctial above the Horizon in the North; that being deducted out of 90 deg. there remaineth AP 40 deg. for the Depth of the North Pole under the Horizon, just to BC the Elevation or Alti∣tude of the South-Pole above the Horizon in the South.

[illustration] geometrical diagram

	deg.	min.
Sun's Altitude	58	00
South Declination	08	00
Height of the Aequator	50	00
	90	00
The Latitude is	40	00