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.

PROBL. XII. Having a Right Line given, How to make a Geometrical Square, whose Sides shall be equal to the Right Line given.

THe Line given is RI, and it is required to make a Geometrical Square whose Sides shall be equal to the Line RI, First draw the given Line RI, then (by the first and se∣cond Problem) upon the Point B raise the Per∣pendicular BC, making the Line BC equal to the given Line RI also: Then taking the said RI in your Compasses, place one Foot in C, with the other describe an Arch at D; The Compass at the same distance, set one Foot in A, and cross the former Arch at D; then draw the Lines D, C and DA, which shall conclude the Geometrical Square ABCD, which was required.

[illustration] geometrical diagram