Quinquangle

And from hence also shall be the geodesy of the Icosaedrum. For the finding out of the heighth of the pyramis, there is the semidiagony of the side of the decangle and the halfe ray of the circle: But the side of the decangle is a right line subtending the halfe periphery of the side of the quinquangle, or else the greater segment of the ray proportionally cut.

It is about 2,500 yards in circuit, is built of red stone, and, according to Von Orlich, is now " a bastioned quinquangle ; the ancient walls with semicircular bastions face the two streams ; the land side is quite regular, and consists of two bastions, and a half-bastion with three ravelins," and stands higher than any ground in face of it.

Kenett states that the military works still known by the name of Tadmarten Camp and Hook-Norton Barrow were cast up at this time ; the former, large and round, is judged to be a fortification of the Danes, and the latter, being smaller and rather a quinquangle than a square, of the Saxons.