The compleat body of the art military in three books : I. The postures of the pike and musket ..., II. Twelve exercises ..., III. The drawing up and exercising of regiments after the manner of private companies ... : also, the duties of all souldiers and officers ... / by Richard Elton ... ; to which is added a supplement comprehending these particulars, I. the duties and qualifications of all officers belonging to an army .., formerly written by Capt. Tho. Rudd ...

Of Irregular Fortifications.

TOuching Irregular Fortifications, I can give no new Precept; only in the general, it is best, if possible, to reduce them to regular Forms: but if the place will not permit it, take first the Plot of the place, and observe what Angles are made between every two sides thereof.

Then look in the Table, in the cell of the Angles of Polygons, and see what Polygon the observed Angle comes neerest to, and make that Bastion according to the measures belonging to that Polygon, and so of the rest; so shall you have unequal Bastions, but alike defensible. Wherein likewise it is be noted, that if the

two sides of your interior Polygon be of unequal length, the Bastion is best framed according to the measures taken upon the shorter side.

Example. Let it be required to draw Bastions to the side of an inordinate Pen∣tagon, whose Angles are, as they are marked in the third Figure.

First, I observe 134, the Angle comprehended between two of the sides, comes neerest to the Angle of an Octagon in the Cell of the Angles of Polygons; I con∣clude therefore, that Bastion is to be drawn according to the measures belonging to an Octagon, taking the measures from the shortest side A B.

Now because the measures of the Polygon interior belong to an Octagon, is 614, you must make a Scale, of which 614 parts shall be equal to A B; then set off the Neck or Gorge A E, B E, 127 such parts, as A B is 614; then measure 106 for the Wing. Lastly, because the Center of the Figure is not known, by which the measure of the Capital line should be taken, I take the Angle between the Wing prolonged and the Face, and take off 240 such parts as the Curtain is 360, and so finish the Bastion belonging to the Angle 134

The next Angle 113, which is neerest to a Hexagon, therefore that Bastion must be framed from the shorter side, according to the measures of a Hexagon; and so must all the Angles be fortified by those measures which come neerest to the Angle comprehended between the sides thereof.

But in all Irregular Fortifications, much is attributed to the judgment of the Enginier, either to increase or diminish the Angles as he finds most convenient, but in such manner as the line of defence may scoure the face of the Bastion, and that one part thereof may defend, and be defended by the other.

It now remains to treat of the manner of making of Ditches about Forts, of the quantity of earth required to make a Fort, with Walls of any determined breadth and height; as also what inclinations they ought to have, both on the inside and the outside; within, of that sloapness, that the Souldiers may (with∣out much difficulty) go up and down; but without, sloaping so little, that they may not be scaled by the Enemy; yet so much, that the foundation may be strong. But this I shall omit for the present, my design not being to write here all necessary to be known in this Art, but only so much as might enable the Ingenious Souldier to be able to fortifie any place in the absence or want of an Enginier.