BOOK ONE.

[Signature A 2]

SECOND PROPOSITION.

THEOREM.

It very often happens that the DefenseThe "defension" or line of defense refers to the line of sight and fire that soldiers use to protect the walls from attackers., while appearing to originate from one line, in fact fails because it proceeds from another line.

FIGURE NO. II.

In the figure, the defense seemingly issues from the line marked with a point A, and then a part of this line appears to provide fire to the line CD; but when the width of the ParapetA breastwork or low wall on top of a rampart, designed to protect soldiers from enemy fire. is added, it is clearly evident that the defense comes from another line, marked B,B,B,B, since the defenders must station themselves at the interior line.

THIRD PROPOSITION.

THEOREM.

Demonstration of the best Defense that can be found.

FIGURE NO. III.

The flanking lines are drawn from all sides to show that the line HI is flanked by the defenders marked A; the line GH is flanked by the others marked C; and FG by the others marked B. Then it shall be said that such a defense is the best, judging by the intervention of the width determined by DE, for it is evident that the wider such a defense is, the better it is; adding that the line HI is commonly the first to be attacked. Therefore, to prove the quality of the defense, such width ensures that every place fortified in this manner surpasses others that do not have such an extended defense.

ON SMALL WORKS.

Small Works are those which lack a full defense; either because they are not provided with any defense at all, such as RedoubtsSmall, enclosed defensive structures, usually square, used to protect isolated points., or because they have only a half-defense, such as Star Forts and Forts with half-Bastionsoriginal: "Boulevards." In the 17th century, "boulevard" specifically referred to a bastion, a projecting part of a fortification..

FIRSTLY, ON REDOUBTS.

Redoubts, for lack of defense, are more suitable for watch-towers and sentries than for guarding a place of high importance. The Square shape is most suitable for them, and its side shall be made from about forty-eight up to six score feet original: "fix vingts pieds." This is 120 feet, using the early modern French vigesimal (base-20) counting system.. Now, as it is always necessary to take certain givens to complete a fortification, it will be necessary to provide two things here, which we shall take: the Square Shape and the Side length.

FOURTH PROPOSITION.

To Draw the Design of a Redoubt.

FIGURE NO. IV.

Here the Square figure is given, and the side of forty-eight feet; one need only take these forty-eight feet from a scale, and from such length draw line AB, upon which the Square is constructed according to Geometry; and the design of such a Redoubt will be completed.

FIFTH PROPOSITION.

Calculation of a Redoubt.

FIGURE NO. V.

One must learn by heart the names of the points, lines, and angles of every work.
A is the center point. B, C, D, E are the points of the figure.
AC is the Radiusoriginal: "Raid." From the Latin "radius," the distance from the center to a vertex.. BC is the Side. BE is the Diagonal.
BAC is the angle of the Center. BCE is the angle of the figure.