Of Cittadels and Castles.
CIttadels, and Castles, are built to Command and Bridle a Town, in case the Burgers should be Rebellious, and to be the last Refuge or Retreit. They are commonly of four or five Bastions, and are used when a Town is so great, that the Garrison makes in Number but a 1/5 or 1/6 part of the Burgers; al∣though sometimes they are used as Blinds, built on any Hill, or Rising-Ground near a Town, from hindring an Enemy from Shooting into it. They are set so, that there may be two Faces, and a Curtain towards the Town.
The Pentagon is the most advantageous Figure to make a good Cittadel, which opposes three Bastions to the Enemy, and two to the Town, Commanding at the same time both the Cam∣paign and the Town.
The Interior Polygon of the Pentagon may be made of 1/4 of the adjoyning Curtain, or a little more; the two Ports, or Gates of the Cittadel are placed, that one may be towards the Cam∣paign, the other towards the Town, every one covered by a Ravelin.
If the Cittadel, or Castle, be a square, or 9 sided Figure, then the Center of it may be on the Point of the Interior Polygon of the place.
The Center of the Pentagon, or 5 sided Figure, may be near on the Point of the Bastion of the Town, taken away to make the Cittadel in, al∣though some use them at a greater distance.
The Gorges, Flanks, and Capitals are set off in proportion to their Interior Polygons; the Ram∣perts are to be as high as those of the Town.
For a more particular description of the Out-Works, consult Travaux de Mars.