Instruction on the Fortification of Cities

A detailed technical diagram shows the ground plan of a bastion integrated into a city wall. Two diagonal lines labeled "City Wall" flank the construction. A central vertical axis is labeled with 'f' at the top and passes through point 'b' at a horizontal intersection. A horizontal line is marked with points 'd', 'b', and 'e'. Points 'i', 'h', and 'g' are plotted along a lower arc. Arcs indicate the thickness and curvature of circular walls. Various alphabetical labels (a, p, m, n, o, l, q) designate specific geometrical points and construction lines. Centered within the diagram is the identifying text: "This is the ground plan of this bastion below."

Now the thickness of the walls is established; first, let the city walls remain at the thickness they were before where they meet the bastion, and if they can be used for the construction as they stand, it is for the better. But upon the line .d.e., one should lay a straight wall in the foundation eighteen feet original: "schůch"; a historical unit of measurement roughly equivalent to a modern foot. thick. Thereafter, make the first foundation of the circular wall .d.i.e. also eighteen feet thick, and set a compass original: "zirckel" with one foot at point .f. and with the other draw this wall thickness in a circle until it reaches the line .d.e. Where it then touches the inside on both sides, place .n. and .o. there. Next, take the thickness .d.n. and .o.e. and proceed backward to the line .l.m.; that is how thick the side walls shall be. But make the rear transverse wall original: "zwerch mauer" .l.m. ten feet thick. Furthermore, make the cross-wall original: "creutz mauer" on the line .f.h.i. also eighteen feet thick. Then set two other circular walls behind the outermost ones, making them increasingly thinner and narrower the closer they come to the middle wall .d.e., just as with the empty spaces between them. But one seeks this tapering tapering: "veriungung" in the original; the masterly geometric reduction of structural elements to maintain stability while managing weight and space. as follows: take the length on the cross-line .h.g. between the middle wall .d.e. and point .i., and mark the thickness of the circular walls on line .h.i. with a point .z., and at the back of the wall .d.e. with an .h. Mark these three points .i., .z., and .h. on a straightedge original: "richtscheyt". Afterward, a triangle .a.b.c. is made so that .b. is a right angle and .c.b. is a vertical line. Subsequently, divide .c.b. with five points into six equal fields, and from all points between .c. and .b., draw straight lines to point .a. Then place the straightedge with point .i. at the top on line .c.a., but place point .h. on line .a.b. and move the straightedge back and forth until point .z. reaches the next line drawn from the first point below line .c.a. to point .a. Where the other lines, drawn from line .c.b. to point .a., intersect the straightedge between .z. and .h., mark those points. All of this is then transferred into the ground plan, and the circular walls and the fields between them are drawn accordingly from point .f. to the straight walls .d.e. Thus the walls taper masterfully; I have drafted original: "auffgerissen" such a figure following this ground plan.