3. North of the Tagus is Lusitania, the principal of the nations of Iberia, and the one which has most frequently encountered the arms of the Romans. On the southern side this country is bounded by the Tagus, on the west and north by the ocean, on the east by the well-known nations of the Carpetani, the Vettones, the Vaccæi, the Gallicians, and by others not worthy to be mentioned on account of their insignificance and obscurity. On the other hand, certain historians of the present day give the name of Lusitanians to all of these nations. To the east the Gallicians border on the nation of the Asturians and Keltiberians, the others [border] on the Keltiberians. In length Lusitania is 3000[1128] stadia; its breadth, which is comprised between the eastern side and the opposite sea-coast, is much less. The eastern part is mountainous and rugged, while the country beyond, as far as the sea, consists entirely of plains, with the exception of a few inconsiderable mountains. On this account Posidonius remarks that Aristotle was not correct in supposing that the ebb and flow of the tide was occasioned by the sea-coast of Iberia and Maurusia.[1129] For Aristotle asserted that the tides of the sea were caused by the extremities of the land being mountainous and rugged, and therefore both receiving the wave violently and also casting it back. Whereas Posidonius truly remarks that they are for the most part low and sandy. 4. The country which we are describing is fertile, and irrigated by rivers both large and small, all of which flow from the eastern parts parallel with the Tagus: most of them are navigable and full of gold dust. After the Tagus, the most noted rivers are the Mondego[1130] and the Vouga,[1131] which are navigable but for a short distance. After these is the Douro,[1132] which flows from afar by Numantia,[1133] and many other colonies of the Keltiberians and Vaccæi; it is capable of being navigated in large vessels for a distance of nearly 800 stadia. Besides these there are other rivers, after which is the [river] of Lethe, which some call the Limæa,[1134] others the Belio,[1135] it likewise rises amongst the Keltiberians and Vaccæi. After [CAS. 153] this is the Bænis, (some call it the Minius,[1136]) by far the largest river of Lusitania,[1137] being navigable for a distance of 800 stadia. Posidonius says this too rises amongst the Cantabrians.[1138] An island[1139] lies before its outlet, and two moles affording anchorage for vessels. A natural advantage [of this country] well deserving of commendation is, that the banks of the rivers are so lofty as to be capable of containing the entirety of the water raised by the high tides of the sea, without either being overfilled, or overflowing the plains. This was the limit of Brutus’s expedition. Beyond there are many other rivers parallel to those I have named.