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.

CHAP. XI. Of the Crosiers.

WHen the Mariners pass the Aequinoctial Line towards the South, so that they cannot see the North-Star, they make use of another Star, which is the Constellation called the Centaur; which Star, with three other no∣table Stars which are in the same Constellation, maketh the Figure of a Cross (be∣twixt his Legs) for which cause they call it the Crosiers. And it is holden for certain, That when the Star A (which of all four cometh nearest the South-Pole) is

[illustration] celestial diagram

North and South by the Star B, then it is rightly scituated to take the Height by: And because this Star A, which is called the Cocks-foot, is 30 Degrees from the South-Pole, it cometh to pass, it being scituated as before-said, we take the Height thereof (which is then the greatest that it can have) this Height will truly shew how far we are distant from the Aequinoctial: For if the said Height be 30 Degrees, then we are under the very Aequinoctial: But if it be more than 30 deg. then are we by so much past the Aequinoctial, toward the South: And if it be less than 30 deg. so much as it wanteth, we are to the North of the Aequinoctial. And here it is to be noted, That when the Guards are to the North-East, then is the Star in the Crosiers fitly scituated for observation, because then they are in the Meridian.