We may add that the word is not used with this special import in the time of the republic; and beyond doubt this conception of the _limes_ only originated with the institution of the chain of posts enclosing the state, where natural boundaries were wanting--a protection of the imperial frontier, which was foreign to the republic, but was the foundation of the Augustan military system, and above all, of the Augustan system of tolls.] [66: The Sugambri transplanted to the left bank are not subsequently mentioned under this name, and are probably the Cugerni dwelling below Cologne on the Rhine. But that the Sugambri on the right bank, whom Strabo mentions, were at least still in existence in the time of Claudius, is shown by the cohort named after this emperor, and thus certainly formed under him, doubtless of Sugambri (_C. I. L._ iii. p. 877); and they, as well as the four other probably Augustan cohorts of this name, confirm what Strabo also in a strict sense says, that these Sugambri belonged to the Roman empire. They disappeared doubtless, like the Mattiaci, only amidst the tempests of the migration of nations.] [67: The fortress of Niederbiber, not far from the point at which the Wied falls into the Rhine, as well as that of Arzbach, near Montabaur, in the region of the Lahn, belong to upper Germany. The special significance of the former stronghold, the largest fortress in upper Germany, turned on the fact that it, in a military point of view, closed the Roman lines on the right bank of the Rhine.] [68: The levies (_Eph. Epigr._ v. p. 274) require us to assume this, while the Frisians, as they come forward in the year 58 (Tacitus, _Ann._ xiii. 54) rather appear independent; the elder Pliny also (_H. N._ xxv. 3, 22) under Vespasian names them, looking back to the time of Germanicus, as _gens tum fida_. Probably this is connected with the distinction between the _Frisii_ and _Frisiavones_ in Pliny, _H. N._ iv. 15, 101, and between the _Frisii maiores_ and _minores_ in Tacitus, _Germ._ 34. The Frisians that remained Roman would be the western; the free, the eastern; if the Frisians generally reach as far as the Ems (Ptolem. iii. 11, 7), those subsequently Roman may have settled perhaps to the westward of the Yssel. We may not put them elsewhere than on the coast that still bears their name; the designation in Pliny, iv. 17, 106, stands isolated, and is beyond doubt incorrect.] [69: The fourth upper German legion was sent in the year 58 to Asia Minor on account of the Armeno-Parthian war (Tacitus, _Ann._ xiii. 35).] [70: Frontinus, _Strat._ iv. 3, 14. In their territory the advancing troops must have constructed a reserve station and a depot; according to tiles recently found near Mirabeau-sur-Bèze, about fourteen miles north-east of Dijon, men of at least five of the advancing legions had executed buildings here (_Hermes_, xix. 437).]