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roads leading to the gates should be winding and turnto the left from the gates. By this arrangement, theright sides of the attacking troops, which are not coveredby their shields, will be open to the weapons of the be-sieged. The plan of a city should not be square, norformed with acute angles, but polygonal; so that themotions of the enemy may be open to observation. Acity whose plan is acute-angled, is with difficulty de-fended ; for such a form protects the attacker more thanthe attacked. The thickness of the walls should be suf-ficient for two armed men to pass each other with ease.The walls ought to be tied, from front to rear, with many 'pieces of charred olive wood; by which means the two *faces, thus connected, will endure for ages. The advan-tage of the use of olive is, that it is neither affected byweather, by rot, or by age. Buried in the earth, orimmersed in water, it lasts unimpaired: and for thisreason, not only walls, but foundations, and such walls asare of extraordinary thickness, tied together therewith,are exceedingly lasting. The distance between eachtower should not exceed an arrow’s flight; so that if, atany point between them, an attack be made, the besiegersmay be repulsed by the scorpions and other missile en-gines stationed on the towers right and left of the pointin question. The walls will be intercepted by the lowerparts of the towers where they occur, leaving an intervalequal to the width of the tower; which space the towerwill consequently occupy : but the communication acrossthe void inside the tower, must be of wood, not at allfastened with iron : so that, if the enemy obtain posses-sion of any part of the walls, the wooden communicationmay be promptly cut away by the defenders, and thusprevent the enemy from penetrating to the other parts ofthe walls without the danger of precipitating themselvesinto the vacant hollows of the towers. The towers shouldbe made either round or polygonal. A square is a badform, on account of its being easily fractured at the