[471] The ravine which descends to the Auron is still recognised at the present day, between the Portes Saint-Michel and Saint-Paul, by the sudden incline of the ground. Old plans of Bourges designate it by the name of the Vallée Saint-Paul. The opposite ravine, which runs towards the Porte Bourbonnoux, has disappeared under the successive fillings up composing the soil of the garden of the archbishop’s palace. The ridge of land forming the avenue cannot have been in Cæsar’s time more than 100 mètres broad. It has lost its primitive physiognomy, especially by the formation of the Place Sérancourt, in 1700, on a site the level of which did not then exceed that of the field of the present fair. The depression of the ground which existed before the wall is more visible; it has been filled-up during the different sieges of Bourges.
[472] This is evident, since the Romans, in order to be able to give the assault, were obliged to construct a terrace eighty feet high. General de Gœler believed this measurement exaggerated. Nevertheless, as this terrace was constructed in a ravine, it was necessary that it should compensate a difference of level of eighty mètres, of which thirty, perhaps, represent the height of the wall.
[473] Vercingetorix, encamped first towards Dun-le-Roi, had approached nearer Bourges. He had established his new camp to the east of that of Cæsar, perhaps at La Chenevière, at the confluence of the Yèvre and the brook of Villabon, fourteen kilomètres from Bourges.
[474] See the quotation from Vegetius, p. 143, note (1).
[475] We read in Vitruvius, on occasion of the siege of Marseilles: “When the tortoise approached to batter the wall, they let down a cord furnished with a slip-knot, in which they caught the ram, and raised its head so high, by means of a wheel, that they prevented its striking the wall.” (Vitruvius, X. 16.)
[476] Titus Livius expresses himself thus in speaking of the beseiged in Ambracia, who dug a mine to meet that of the enemies: “Aperiunt viam rectam in cuniculum.” (XXXVII. 7.)
[477] Several authors have thought that these beams, instead of being placed perpendicularly to the direction of the wall, were placed parallel to that direction. This interpretation appears to us inadmissable. The beams so placed would have no solidity, and would easily have been torn down. We see on the Trajan Column walls constructed as we describe; moreover, the Latin expression trabes directæ can leave no doubt, for the word directus means always perpendicular to a direction. (See De Bello Gallico, IV. 17, directa materia injecta, and the dissertation in the Philologus, Jahrganges 19, Heft. 3.)
[478] The name of pluteus was given generally to all kinds of covering with hurdles or with skins. (Festus, in voce Pluteus.—Vitruvius, X. 20.)—Vegetius (IV. 15) applies the name of pluteus to a kind of penthouse, of wicker-work or skins, mounted on three wheels, and protecting the men placed behind it, so that they might shoot at the defenders.
[479] They gave this name to a small engine resembling the balistæ, which threw darts. These scorpions composed, as it were, the field-artillery of the ancients.
[480] De Bello Gallico, VII. 32.