In 585, we learn from Gregory of Tours, that the Battering Ram and the Testudo were employed by the Burgundians in the siege of Comminges[148]. This Tortoise, or screen for the propellers of the Ram, is described by the translator of Vegecius in 1408 under the name of the "Snayle or Welke[149]:" "For, righte as the snaile hath his hous over hym where he walkethe or resteth, and oute of his hous he shetethe his hede whan he wolle, and draweth hym inne a-yene, so doth this gynne." In the ninth century we obtain considerable light on this subject from the curious description of the Siege of Paris, written in Latin verse by Abbo, a monk of St. Germain-des-Prez, who was an eye-witness of the events he records. He names the Musculus and the Pluteus, both of which were contrivances to shelter the besiegers while at work; the Balista and Mangana, machines for casting large stones; the Catapulta, which cast both stones and darts; the Terebra, a spiked beam for boring into the walls; and the Falarica, a gyn throwing darts to which burning substances were affixed; a terrible instrument in those days, when the roofs of houses were almost invariably covered with thatch. The Moveable Towers formed of wood, in imitation of those of the Romans, and placed by the walls of city or castle in order to bring the assailants to a level with the defenders, are first mentioned in medieval annals under the eleventh century; but they play no conspicuous part in the military history of these days till the succeeding century, when their employment appears to have been frequent. In 1025, Eudes, comte de Chartres, is said to have used the Moveable Tower in besieging the Castle of Montbrol, near Tours; and so high was it, that it overtopped the keep-tower of the fortress[150].