7.72.1Quibus rēbus cognitīs ex perfugīs et captīvīs, Caesar haec genera mūnītiōnis īnstituit.When he learned this from deserters and prisoners, Caesar began these kinds of fortification. 7.72.1Fossam pedum vīgintī dīrēctīs lateribus dūxit, ut eius fossae solum tantundem patēret quantum summae fossae labra distārent.He dug a ditch twenty feet wide with vertical sides, so that the bottom of the ditch was as wide as the distance between its edges at the top.Note. dīrēctīs lateribus: 'with vertical sides'. tantundem … quantum: 'as much … as'; the bottom of the ditch was as wide as its top. 7.72.2Reliquās omnēs mūnītiōnēs ab eā fossā pedēs quadringentōs redūxit, id hōc cōnsiliō, quoniam tantum esset necessāriō spatium complexus, nec facile tōtum corpus corōnā mīlitum cingerētur, nē dē imprōvīsō aut noctū ad mūnītiōnēs hostium multitūdō advolāret aut interdiū tēla in nostrōs operī dēstinātōs conicere possent.He set back all the other works four hundred feet from that ditch; he did this on purpose, since he had of necessity enclosed so large an area, and the whole circuit could not easily be manned with a ring of soldiers, so that a mass of the enemy should not swoop on the works suddenly or by night, or by day hurl missiles at our men assigned to the work.Note. id hōc cōnsiliō: 'he did this with this purpose', explained by the clause nē … advolāret aut … possent.
7.72.3Hōc intermissō spatiō duās fossās quīndecim pedēs lātās, eādem altitūdine perdūxit, quārum interiōrem campestribus ac dēmissīs locīs aquā ex flūmine dērīvātā complēvit.Leaving this space, he dug two ditches fifteen feet wide and of the same depth; the inner one, where the ground was flat and low, he filled with water drawn from the river. 7.72.4Post eās aggerem ac vallum duodecim pedum exstrūxit.Behind these he built an earthwork and rampart twelve feet high. 7.72.4Huic lōrīcam pinnāsque adiēcit grandibus cervīs ēminentibus ad commissūrās pluteōrum atque aggeris, quī ascēnsum hostium tardārent, et turrēs tōtō opere circumdedit, quae pedēs LXXX inter sē distārent.To this he added a breastwork and battlements, with large forked stakes projecting at the joins of the screens and the earthwork to slow the enemy's climb, and he surrounded the whole work with towers eighty feet apart.Note. Huic means the rampart (vallum and agger). quī … tardārent is a relative clause of purpose describing the stakes (cervīs).