4.17.1Caesar hīs dē causīs quās commemorāvī Rhēnum trānsīre dēcrēverat;Caesar had decided to cross the Rhine for the reasons I have mentioned; 4.17.1sed nāvibus trānsīre neque satis tūtum esse arbitrābātur neque suae neque populī Rōmānī dignitātis esse statuēbat.but he thought that crossing by ships was not safe enough, and he judged it not in keeping with his own dignity or that of the Roman people.Note. neque suae … dignitātis esse: predicate genitive, 'was not in keeping with his dignity'. 4.17.2Itaque, etsī summa difficultās faciendī pontis prōpōnēbātur propter lātitūdinem, rapiditātem altitūdinemque flūminis, tamen id sibi contendendum aut aliter nōn trādūcendum exercitum exīstimābat.And so, although the very great difficulty of building a bridge was set before him, because of the width, swiftness and depth of the river, he nevertheless thought he must make the effort, or else not take the army across.Note. id sibi contendendum: 'that he must strive for it', the gerundive with dative of agent; the alternative is aliter nōn trādūcendum exercitum, 'otherwise the army was not to be led across'. 4.17.3Ratiōnem pontis hanc īnstituit.He set about the plan of the bridge in this way. 4.17.3Tigna bīna sēsquipedālia paulum ab īmō praeacūta dīmēnsa ad altitūdinem flūminis intervallō pedum duōrum inter sē iungēbat.He joined together pairs of beams a foot and a half thick, sharpened a little at the bottom and measured to the depth of the river, two feet apart.Note. tigna bīna: distributive numeral, 'pairs of beams'. intervallō pedum duōrum: ablative of measure, 'at a distance of two feet'.
4.17.4Haec cum māchinātiōnibus immissa in flūmen dēfīxerat fistūcīsque adēgerat, nōn sublicae modō dērēctē ad perpendiculum, sed prōnē ac fastīgātē, ut secundum nātūram flūminis prōcumberent, iīs item contrāria duo ad eundem modum iūncta intervallō pedum quadrāgēnum ab īnferiōre parte contrā vim atque impetum flūminis conversa statuēbat.When he had let these down into the river by machines, fixed them, and driven them in with rammers, not straight up and down like a pile, but leaning forward and sloping, so that they inclined with the current of the river, he set opposite them two more joined in the same way, forty feet apart, on the downstream side, slanting against the force and current of the river.Note. sublicae modō: 'in the manner of a pile'. ab īnferiōre parte: 'on the downstream side'. impetū should be impetum. 4.17.6Haec utraque īnsuper bipedālibus trabibus immissīs, quantum eōrum tignōrum iūnctūra distābat, bīnīs utrimque fībulīs ab extrēmā parte distinēbantur;These two pairs were held apart at the top by beams two feet thick laid in between them, as wide as the gap between the joined timbers, with a pair of braces at each end; 4.17.7quibus disclūsīs atque in contrāriam partem revīnctīs, tanta erat operis firmitūdō atque ea rērum nātūra ut, quō maior vīs aquae sē incitāvisset, hōc artius inligāta tenērentur.since these were held apart and fastened in opposite directions, the structure was so strong and of such a nature that the greater the force of the water rushing against it, the more tightly the parts were held bound together.Note. quō maior … hōc artius: ablatives of degree of difference, 'the greater … the more tightly'.
4.17.8Haec dērēctā māteriā iniectā contexēbantur ac longuriīs crātibusque cōnsternēbantur;These were connected by timber laid lengthwise on top and covered over with poles and wickerwork; 4.17.9ac nihilō sētius sublicae et ad īnferiōrem partem flūminis oblīquē agēbantur, quae prō ariete subiectae et cum omnī opere coniūnctae vim flūminis exciperent, et aliae item suprā pontem mediocrī spatiō, ut, sī arborum truncī sīve nāvēs dēiciendī operis causā essent ā barbarīs missae, hīs dēfēnsōribus eārum rērum vīs minuerētur neu pontī nocērent.and none the less piles were also driven in slantwise on the downstream side of the river, to be set under like a buttress and joined to the whole structure to take the force of the current; and others likewise a short way above the bridge, so that if tree trunks or ships were sent down by the barbarians to break the structure, the force of these things might be lessened by these barriers and they might not harm the bridge.Note. nihilō sētius: 'none the less'. The text splits oblīquē into obli que. prō ariete: 'as a buttress' (literally 'in place of a ram').