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 Arithmetical way.

6000 × 20 pound 13 ounces./8332 = 15 pound almost, as before.

Thus you are always to take care of over-loading your Piece, which error many run into, when they call a Piece a Demi-canon, they presently load her with so much as is allowed for such a Piece so named, seldom examining whether the Piece have Metal enough for such a Charge; by which mistake they endanger their own lives, and others which stand near. Now, for easy plain Rules, I say you never had before laid down in this manner, to resolve these things; for if you compare these Rules with Nath. Nye, Master Gunner of the City of Worcester, or any other Art of Gunnery, you will find a great deal of difficulty in Cubing and Extracting the Cube Root, and with re∣ducing and Fractions (which here you may do five Questions, for one that way, and more true and near, therefore I compare them to his Rules.